text
stringlengths 286
572k
| score
float64 0.8
0.98
| model_output
float64 3
4.39
|
|---|---|---|
On September 29th, Lauranne Lanz led a seminar titled “Panchromatic View of Jet Feedback in Radio Galaxies” at Wilder Hall. Lanz received her Ph.D in astronomy from Harvard University in 2013. She is currently a postdoctoral scholar at Dartmouth College studying active nuclei at the center of galaxies.
According to Lanz, when dust falls into a black hole, the disks of dust that form help launch jets of particles which we can observe at radio frequencies. These powerful jets can transverse an entire galaxy and interact with the dust and gas between stars known as the interstellar medium. The radio jet feedback, affects the interstellar medium’s ability to form new stars, and the details of this phenomenon is an active area of research.
Lanz studies how the jets impact star formation activity in radio galaxies and how they interact with the interstellar medium. When the jets come into contact with the interstellar medium, they inject mechanical energy into the dust and create a hot pocket of gas in the shape of a cocoon around the jet. This cocoon emits X-rays, and the turbulent motion of the gas drives shocks into cooler gas which then releases H2.
Approximately 30% of radio galaxies possess large amounts of H2 at 100-1500 K which were heated by shocks and have liquid hydrogen. These traits are consistent with galaxies that get power from the mechanical energy dissipating from the radio jet. While not directly correlated with jet feedback indicators, star formation in these galaxies is suppressed by a factor of 3 to 6, which is a statistically significant difference from other galaxies. This suppression is likely to have the strongest impact on the stellar mass of moderately gas-rich galaxies. Lanz will continue to research how the radio jets impact the galaxies around them, and how stellar formation is affected by this phenomenon.
- Lanz, L. (2016, September 29). Panchromatic View of Jet Feedback in Radio Galaxies. Lecture, Hanover. | 0.820405 | 3.859343 |
How dense is dark matter?
It very much depends on where you are! Dark matter as we understand it must be some kind of particle, or at least act like some kind of particle. We’re not exactly clear on what the exact nature of that particle would be, or what its individual mass is, or what kind of interactions it ought to have either with itself or with the matter that makes up our planet and all the stars.
But it certainly does seem that dark matter isn’t spread evenly throughout the entire universe. It’s clustered in lumps, and those lumps become the homes to galaxies. Small gatherings of dark matter are generally assumed to be roundish, since that’s the easiest shape for a three dimensional object to form under the influence of gravity.
For galaxy clusters, we can actually map out the shape of the dark matter surrounding these thousands of galaxies by looking at the way that light bends around that part of the Universe. Not all clusters have particularly spherical dark matter surroundings, and we can see the irregularities because the light from galaxies behind the cluster is not bent in the same way along all of the cluster’s edges.
Within any of these collections of dark matter (technically called halos) surrounding a galaxy or a collection of galaxies, the dark matter is densest at the center, and becomes gradually more diffuse the further out you go. For our own Milky Way, that means that the dark matter density is the highest towards the very center of the galaxy, and out near our solar system, the dark matter density is significantly lower.
Most galaxies contain significantly more mass in dark matter than in luminous matter, but this isn’t because it’s more dense -- the dark matter halo is simply much larger. In the case of the dark matter surrounding our Milky Way, it’s also spherical and not effectively flat, like the bright part of the galaxy is. You can pack a lot more material in a sphere than you can in a circle, so the combination of the dark matter halo being physically larger and a sphere means you wind up with a lot more mass.
The dark matter density near the solar system, from what I could find, sits at around 0.006 solar masses per cubic parsec, which is a set of units that’s not going to make much sense unless you’re a professional astrophysicist. This is extremely low density. Six-thousandths of a solar mass is approximately the same as six Jupiter mass planets, and a parsec is a 75% of the distance from the Sun to the nearest star. So this means if you wanted to reproduce the dark matter density with the luminous matter that planets are made of, you’d have to clear out a cube of space that’s three light years to a side of absolutely everything. No dust, no gas, no stars, no planets. You get six Jupiters in that box, and you’ll have to spread those Jupiters around, since we don’t have any indication that dark matter comes in chunks.
We can scale this metaphor down a bit; if you wanted to get the same kind of density but in a cubic kilometer, you’d have to evacuate that square kilometer of absolutely every single atom of material. A single grain of birch pollen floating in that cubic kilometer would contain 20 times more mass than there would be in dark matter in that same volume.
At the center of the galaxy, the dark matter should be more than 150 times more concentrated, but this is very difficult to measure within our own galaxy. So far, our observations seem to line up with the models we’ve developed, but there’s definitely room to improve. In any case, 150 times the density of the solar neighborhood is still not very dense! That gets us all of about eight grains of pollen. | 0.817626 | 3.981712 |
These places never see sunlight, are buried deep under thick ice crusts and warmed mostly by radioactive decay and tidal forces: subsurface oceans of celestial objects far from their stars – if they have any. Decades ago, they were the domain of science fiction, until such places were hypothesized in our solar system thanks in part to Voyager flybys of Europa in 1979. Shortly after, the idea was popularized when it appeared in Arthur C. Clarke’s Space Odyssey saga. Since then, we learned much more about characteristics of possible subsurface oceans, discovered that they probably exist on more worlds than we dared to expect just a few years ago, and that they’re more fascinating than even SF authors hoped.
My article on the topic of subsurface oceans was published today in Clarkesworld Magazine. I wrote about moons and dwarf planets in our system as well as extrasolar planets; however, the topic is so vast that I couldn’t have possibly covered everything of interest – especially when virtually any piece of information is interesting and thought-provoking. If you’ve read the article and want to go deeper and learn more, you can read some of the following material I’ve used. Many of the scientific papers can be downloaded without any special access (use Google Scholar). The rest should be accessible from most university libraries.
If you don’t want to dig into the scientific articles at first, I can recommend the popular science book Alien Seas: Oceans in Space. It doesn’t deal just with subsurface oceans of icy objects; it concerns nearly any conceivable kind of oceans in a broad sense of the word, in our system as well as in the rest of the galaxy. It’s an excellent introductory read, well-written and an interesting food for thought.
There is plenty of resources about Europa but it’s never a bad way to start with a relatively recent good review. That’s the case of Kargel et al. (2000); very comprehensive information about Europa’s history, geology, characteristics of both the crust and the ocean and its prospects for life can be found there. Specifically conditions for methanogenesis as an energy source for possible life on Europa are discussed in McCollom (1999). More about all three Galilean moons possibly containing bodies of liquid water and consequences of different parameters is to be found in Zimmer et al. (2000) and Spohn and Schubert (2003).
A lot has been published about Saturn’s moons Enceladus and Titan; this is just a tip of the iceberg: Titan’s probable internal structure is described in Tobie et al. (2005). Regarding the tiny Enceladus, Roberts and Nimmo (2007) investigated the long-term stability of its ocean; analysis of ice grains from its geysers in Saturn’s E-ring is present in Postberg et al. (2009); shear heating as a heat source for the ocean is discussed in Nimmo et al. (2007); possible conditions for life in Parkinson et al. (2007); this along with possible biomarkers in McKay et al. (2008).
A paper by Hussmann et al. (2006) dealt with modeling the interior of icy satellites of the giant planets and trans-Neptunian objects. This work represents a turning point of a kind – a subsurface ocean even in very far Kuiper belt bodies like Eris and Sedna (sometimes also considered an inner Oort cloud object) was first officially proposed here. Thermal evolution and possible cryovolcanism of KB objects is also investigated in Desch et al. (2009).
Concerning Pluto, Robuchon and Nimmo (2011) modeled Pluto with several different initial condition sets and proposed what observable features might tell us about the possible presence of the ocean during the New Horizons flyby. Spectroscopy of Pluto, its moon Charon and Neptune’s Triton is described in Protopapa et al. (2007), including the detection of crystalline water ice on Charon’s surface.
A very good overview of possibilities of life in the Solar System, including subsurface oceans, and opportunities of energy cycles and geoindicators of life detection can be found in Schulze-Makuch et al. (2002).
Speaking of even further places, Ehrenreich and Cassan (2006) investigated the possibilities of existence of bodies of liquid water (both surface and subsurface) on extrasolar planets throughout the galaxy. Information specifically about the GJ 667C system can be found in Anglada-Escudé et al. (2012). Exomoons are discussed very well in Scharf (2006).
I hope you enjoyed the Clarkesworld article and this list of resources will be of interest to you. If I’ve managed to ignite even one spark of fascination and curiosity, I’m happy.
3rd April 2014 update: Results from Cassini’s measurements of the gravitational pull of Enceladus suggest a large pocket of liquid water near the south pole, as published in the newest issue of Science (Iess et al. 2014); it adds to the indirect (albeit extremely important) evidence of the moon’s intense cryovolcanism. So – good news! Also, discoveries of three dwarf planets were announced in the last couple of days. 2013 FY27 is might be even larger than Sedna (between 760 and 1500 km compared to about 1000 km) so we can expect quite significant radiogenic heating – according to Hussman et al. (2006) model maybe sufficient for a liquid ocean. Let’s hope for even more amazing discoveries like these.
Anglada-Escudé, G., Arriagada, P., Vogt, S. S., Rivera, E. J., Butler, R. P., Crane, J. D., … & Jenkins, J. S. (2012). A planetary system around the nearby M dwarf GJ 667C with at least one super-Earth in its habitable zone. The Astrophysical Journal Letters, 751(1), L16.
Desch, S. J., Cook, J. C., Doggett, T. C., & Porter, S. B. (2009). Thermal evolution of Kuiper belt objects, with implications for cryovolcanism. Icarus,202(2), 694-714.
Ehrenreich, D., & Cassan, A. (2007). Are extrasolar oceans common throughout the Galaxy?. Astronomische Nachrichten, 328(8), 789-792.
Hussmann, H., Sohl, F., & Spohn, T. (2006). Subsurface oceans and deep interiors of medium-sized outer planet satellites and large trans-neptunian objects. Icarus, 185(1), 258-273.
Kargel, J. S., Kaye, J. Z., Head III, J. W., Marion, G. M., Sassen, R., Crowley, J. K., … & Hogenboom, D. L. (2000). Europa’s crust and ocean: Origin, composition, and the prospects for life. Icarus, 148(1), 226-265.
McCollom, T. M. (1999). Methanogenesis as a potential source of chemical energy for primary biomass production by autotrophic organisms in hydrothermal systems on Europa. Journal of Geophysical Research: Planets (1991–2012), 104(E12), 30729-30742.
McKay, C. P., Porco, C. C., Altheide, T., Davis, W. L., & Kral, T. A. (2008). The possible origin and persistence of life on Enceladus and detection of biomarkers in the plume. Astrobiology, 8(5), 909-919.
Nimmo, F., Spencer, J. R., Pappalardo, R. T., & Mullen, M. E. (2007). Shear heating as the origin of the plumes and heat flux on Enceladus. Nature,447(7142), 289-291.
Parkinson, C. D., Liang, M. C., Yung, Y. L., & Kirschivnk, J. L. (2008). Habitability of Enceladus: Planetary conditions for life. Origins of Life and Evolution of Biospheres, 38(4), 355-369.
Postberg, F., Kempf, S., Schmidt, J., Brilliantov, N., Beinsen, A., Abel, B., … & Srama, R. (2009). Sodium salts in E-ring ice grains from an ocean below the surface of Enceladus. Nature, 459(7250), 1098-1101.
Protopapa, S., Herbst, T., & Böhnhardt, H. (2007). Surface ice spectroscopy of Pluto, Charon and Triton. Messenger, 129, 58-60.
Roberts, J. H., & Nimmo, F. (2008). Tidal heating and the long-term stability of a subsurface ocean on Enceladus. Icarus, 194(2), 675-689.
Robuchon, G., & Nimmo, F. (2011). Thermal evolution of Pluto and implications for surface tectonics and a subsurface ocean. Icarus, 216(2), 426-439.
Scharf, C. A. (2006). The potential for tidally heated icy and temperate moons around exoplanets. The Astrophysical Journal, 648(2), 1196.
Schulze-Makuch, D., Irwin, L. N., & Guan, H. (2002). Search parameters for the remote detection of extraterrestrial life. Planetary and Space Science, 50(7), 675-683.
Spohn, T., & Schubert, G. (2003). Oceans in the icy Galilean satellites of Jupiter?. Icarus, 161(2), 456-467.
Tobie, G., Grasset, O., Lunine, J. I., Mocquet, A., & Sotin, C. (2005). Titan’s internal structure inferred from a coupled thermal-orbital model. Icarus, 175(2), 496-502.
Zimmer, C., Khurana, K. K., & Kivelson, M. G. (2000). Subsurface oceans on Europa and Callisto: Constraints from Galileo magnetometer observations.Icarus, 147(2), 329-347. | 0.939991 | 3.648217 |
A team of transatlantic scientists taking a second look at data observations from NASA’s Kepler space telescope, which the agency retired in 2018, have discovered an earth-size exoplanet orbiting in its star’s habitable zone, the space agency announced in a press release on April 15.
The planet, called Kepler-1649c, is located 300 light-years from Earth and is most similar to it in size and estimated temperature, being just 1.06 times larger than our planet, NASA said. The amount of starlight it receives from its host star is 75 percent of the amount of light Earth receives from our sun, suggesting the exoplanet’s temperature may be similar to Earth’s too.
Kepler-1649c is also located within the habitable zone of its star, existing at just the right distance where liquid water can exist on the surface, suggesting that it could potentially support life as we know it.
Unlike Earth though, it orbits a red dwarf star. Such stars make up the largest population of stars in the galaxy and are much smaller and cooler than our Sun. Though none have been observed in this system, this type of star is known for stellar flare-ups that may make a planet’s environment challenging for any potential life.
While much is still unknown about the new-found exoplanet, including its atmosphere, which could affect its temperature, and correct size, NASA said the discovery is intriguing for scientists searching for worlds with potentially habitable conditions.
“This intriguing, distant world gives us even greater hope that a second Earth lies among the stars, waiting to be found,” said Thomas Zurbuchen, associate administrator of NASA’s Science Mission Directorate in Washington. “The data gathered by missions like Kepler and our Transiting Exoplanet Survey Satellite [TESS] will continue to yield amazing discoveries as the science community refines its abilities to look for promising planets year after year.”
The exoplanet joins other’s that are estimated to be closer to Earth in size, like TRAPPIST-1f, while TRAPPIST-1D and TOI 700d are considered to be closer to Earth in temperature. However, Kepler-1649c is by far the most intriguing exoplanet yet as it may be similar in both size and temperature to Earth and lies in the habitable zone of its system.
According to Nasa, Kepler-1649c was overlooked because a computer algorithm called Robovetter, which helps to sort through massive amounts of data produced by the Kepler spacecraft, classified it as false positive. Astronomers know computers make mistakes, so researchers in the Kepler False Positive Working Group, analyze all the false positives to ensure they are genuine errors and not exoplanets, took another look. As it turns out, Robovetter had mislabeled Kepler-1649c, and thus, it was identified as a planet.
“Out of all the mislabeled planets we’ve recovered, this one’s particularly exciting—not just because it’s in the habitable zone and Earth-size, but because of how it might interact with this neighboring planet,” said Andrew Vanderburg, a researcher at the University of Texas at Austin and first author of the study. “If we hadn’t looked over the algorithm’s work by hand, we would have missed it.”
Researchers believe there may also be a third planet in the system but have so far been unable to spot it. They noted that this might be because it’s too small to see or is at an orbital tilt that makes it impossible to find using Kepler’s transit method.
“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,” said Vanderburg. “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.” | 0.807156 | 3.659254 |
Hundreds of hidden nearby galaxies have been studied for the first time, shedding light on a mysterious gravitational anomaly dubbed the Great Attractor.
Despite being just 250 million light years from Earth — very close in astronomical terms — the new galaxies had been hidden from view until now by our own galaxy, the Milky Way.
Using CSIRO’s Parkes radio telescope equipped with an innovative receiver, an international team of scientists were able to see through the stars and dust of the Milky Way, into a previously unexplored region of space.
The discovery may help to explain the Great Attractor region, which appears to be drawing the Milky Way and hundreds of thousands of other galaxies towards it with a gravitational force equivalent to a million billion Suns.
Lead author Professor Lister Staveley-Smith, from The University of Western Australia node of the International Centre for Radio Astronomy Research (ICRAR), said the team found 883 galaxies, a third of which had never been seen before.
“The Milky Way is very beautiful of course and it’s very interesting to study our own galaxy but it completely blocks out the view of the more distant galaxies behind it,” he said.
Professor Staveley-Smith said scientists have been trying to get to the bottom of the mysterious Great Attractor since major deviations from universal expansion were first discovered in the 1970s and 1980s.
“We don’t actually understand what’s causing this gravitational acceleration on the Milky Way or where it’s coming from,” he said.
“We know that in this region there are a few very large collections of galaxies we call clusters or superclusters, and our whole Milky Way is moving towards them at more than two million kilometres per hour.”
The research identified several new structures that could help to explain the movement of the Milky Way, including three galaxy concentrations (named NW1, NW2 and NW3) and two new clusters (named CW1 and CW2). | 0.847784 | 3.690228 |
For thousands of years, the lights they see in the night sky have fascinated people. Our moon is the closest to us and therefore its light appears to be the largest. Why does it look different every night? Is it like the Earth? The Earth’s Moon Lessons will help students learn more about this light in the sky.
1. Students will learn vocabulary related to the Moon.
2. Students will understand why the Moon seems to change shape.
3. Students will compare the Earth to the Moon.
4. The students will learn unusual facts about the Moon.
1.The Moon is a natural satellite of the Earth. A satellite is a celestial body that travels around a larger body.
2. The dips or pits on the Moon’s surface are called craters. This word comes from a Greek word meaning “bowl”. Large rocks hitting the Moon cause craters.
3. The Moon reflects light from the sun. Reflect means to bounce off or throw back from the surface without absorbing it.
4. The Moon has an orbit around the Earth while the Earth has an orbit around the Sun. An orbit is a path around a larger celestial body.
5. The force of gravity keeps the Moon in its path. Gravity is an invisible force attracting one celestial body to another that has mass.
6. The Moon and the Earth both rotate on an invisible axis. To rotate means to spin like a top.
7. The Earth revolves around the Sun and the Moon revolves around the Earth. To revolve means to move in a somewhat circular movement around another object.
Why does the Moon look slightly different each night? It is because we are all in motion. This is even a somewhat difficult concept for an adult because it surely does not feel like we are moving!
The best way to explain this is to use three balls: A large beach ball (the Sun), a soccer ball (the Earth) and a tennis ball (the Moon). Mark the soccer ball with an X indicating where you live.
1. One student holds the Sun in the middle of the room. Remind students that the Sun is a medium star and our source of light and heat. The force of gravity holds the Earth in an orbit around the Sun.
2. Now have the second student hold the Earth several yards from the Sun. The Earth rotates on its axis and revolves around the
Sun. So the student should slowly spin and move around the Sun at the same time.
3. Student three has the Moon and should be placed a few feet from the Earth. The Moon rotates (spins) and revolves around the Earth while the Earth revolves around the Sun.
4. Freeze frame! Stop everyone. From where you live, where is the Sun and where is the Moon? Remember that the Moon reflects the light from the Sun. From where we live, we only see a certain part of the lighted surface because everything is moving.
5. A full Moon is when the Earth is between the Sun and the Moon and we can see the whole lighted surface.
6. Keep a calendar for a month and in each square draw a picture of what the moon looks like. The phases will range from new(totally dark), crescent, half, gibbous and full.
Comparing/Contrasting the Earth and Moon
Provide a graphic organizer for each student.
Each student should add entries to a graphic organizer to compare the Earth and Moon as they learn more facts. How are they alike?How are they different? Use an informational website to help them acquire more information.
Would you weigh more on the Earth or the Moon?
Between the Earth and the Moon, which is colder at night? Hotter in the daytime?
Which one has craters? (both)
Which one has water?
Which one has mountains?
1.The Earth is the only planet to have only one moon. Some planets have no moons while others have many moons.
2. The Moon has no atmosphere. Because of that it becomes very hot during the day and very cold at night. An atmosphere acts like a blanket around the Earth to keep it from having extreme temperatures.
3. If you were standing on the Moon it would always appear to be nighttime.
4. A “Blue Moon” is when two full moons occur in one month.
5. When astronauts Neil Armstrong and Buzz Aldrin placed a USA flag on the moon it had a wire frame around it to give the appearance that it was stretched out in the wind. Remember, there is no air or wind on the moon.
6. The footprints from the astronauts are still there. No wind or rain to destroy them.
7. There is no sound on the Moon. You need air to carry sound waves.
8. If you weigh 100 pounds on the Earth you would only weigh 16.6 pounds on the Moon.
References and Reflections
Hopefully, when your students look into the night sky, they will remember things they have learned from the Earth’s Moon lessons. The Moon is often a remarkable sight. We all need to take time to see it.
Exploring the Moon by Rebecca Olien. Copyright 2007
Why Does the Moon Change Shape? by Melissa Stewart. Copyright 2009
Moon Phase Calendar: https://www.nightskyinfo.com/maps_images/html/moon_phases.htm
Nasa Photo: https://nssdc.gsfc.nasa.gov/imgcat/html/object_page/a16_m_3021.html | 0.801707 | 3.410918 |
Seeing is believing, except when you don’t believe what you see. Astronomers using NASA’s Hubble Space Telescope have found a puzzling arc of light behind an extremely massive cluster of galaxies residing 10 billion light-years away. The galactic grouping, discovered by NASA’s Spitzer Space Telescope, was observed as it existed when the universe was roughly a quarter of its current age of 13.7 billion years.
The giant arc is the stretched shape of a more distant galaxy whose light is distorted by the monster cluster’s powerful gravity, an effect called gravitational lensing. The trouble is, the arc shouldn’t exist.
“When I first saw it, I kept staring at it, thinking it would go away,” said study leader Anthony Gonzalez of the University of Florida in Gainesville, whose team includes researchers from NASA’s Jet Propulsion Laboratory, Pasadena, Calif. “According to a statistical analysis, arcs should be extremely rare at that distance. At that early epoch, the expectation is that there are not enough galaxies behind the cluster bright enough to be seen, even if they were ‘lensed,’ or distorted by the cluster. The other problem is that galaxy clusters become less massive the further back in time you go. So it’s more difficult to find a cluster with enough mass to be a good lens for gravitationally bending the light from a distant galaxy.”
Galaxy clusters are collections of hundreds to thousands of galaxies bound together by gravity. They are the most massive structures in our universe. Astronomers frequently study galaxy clusters to look for faraway, magnified galaxies behind them that would otherwise be too dim to see with telescopes. Many such gravitationally lensed galaxies have been found behind galaxy clusters closer to Earth.
The surprise in this Hubble observation is spotting a galaxy lensed by an extremely distant cluster. Dubbed IDCS J1426.5+3508, the cluster is the most massive found at that epoch, weighing as much as 500 trillion suns. It is 5 to 10 times larger than other clusters found at such an early time in the history of the universe. The team spotted the cluster in a search using NASA’s Spitzer Space Telescope in combination with archival optical images taken as part of the National Optical Astronomy Observatory’s Deep Wide Field Survey at the Kitt Peak National Observatory, Tucson, Ariz. The combined images allowed them to see the cluster as a grouping of very red galaxies, indicating they are far away.
This unique system constitutes the most distant cluster known to “host” a giant gravitationally lensed arc. Finding this ancient gravitational arc may yield insight into how, during the first moments after the Big Bang, conditions were set up for the growth of hefty clusters in the early universe.
The arc was spotted in optical images of the cluster taken in 2010 by Hubble’s Advanced Camera for Surveys. The infrared capabilities of Hubble’s Wide Field Camera 3 helped provide a precise distance, confirming it to be one of the farthest clusters yet discovered.
Once the astronomers determined the cluster’s distance, they used Hubble, the Combined Array for Research in Millimeter-wave Astronomy (CARMA) radio telescope, and NASA’s Chandra X-ray Observatory to independently show that the galactic grouping is extremely massive.
“The chance of finding such a gigantic cluster so early in the universe was less than one percent in the small area we surveyed,” said team member Mark Brodwin of the University of Missouri-Kansas City. “It shares an evolutionary path with some of the most massive clusters we see today, including the Coma cluster and the recently discovered El Gordo cluster.”
An analysis of the arc revealed that the lensed object is a star-forming galaxy that existed 10 billion to 13 billion years ago. The team hopes to use Hubble again to obtain a more accurate distance to the lensed galaxy.
The team’s results are described in three papers, which will appear online today and will be published in the July 10, 2012 issue of The Astrophysical Journal. Gonzalez is the first author on one of the papers; Brodwin, on another; and Adam Stanford of the University of California at Davis, on the third. Daniel Stern and Peter Eisenhardt of JPL are co-authors on all three papers.
Lead image caption: These images, taken by NASA’s Hubble Space Telescope, show an arc of blue light behind an extremely massive cluster of galaxies residing 10 billion light-years away. Image credit: NASA/ESA/University of Florida, Gainsville/University of Missouri-Kansas City/UC Davis | 0.878564 | 3.966146 |
What is a rocket and its uses – How do rockets work: This article, written in a simplified form, contains necessary information regarding what is a rocket and how do rockets work. Rocket and balloon work on a similar mechanism. Its mechanism is based on Newton’s third law of motion. This law states that every action has an equal and opposite reaction. You must have noticed when you release the nozzle of a filled balloon. The air coming out pushes the balloon here and there. The air pushing the balloon act as the thrust makes the balloon fly.
The balloon will fly stable if the opening of the balloon is in solid-state and contains some mass. Similarly, the bottom of the rocket contains mass, making it bulky. So, it can fly with stability in one direction, i.e., the rocket doesn’t move here and there. You must be wondering how do rockets work on such a small principle. We will be talking about how do rockets work in the latter part of this article.
What is a rocket (uses of the rocket)
Rocket is a long, cylindrical tube, spacecraft, or missile which moves up the ground, exuding a large amount of energy and pressure in the form of gas. It is used to send space shuttles, astronauts, space crafts, satellites, etc. in the space. The frame of the rocket is made of light but sturdy materials such as aluminium and titanium. Rockets are encased in a solid and thin layer to protect it from high temperatures and maintains cold temperatures within the rocket. This layer is known as the thermal protection system. Rockets are extremely heavy and weigh hundreds of tons. Most of the weight comprises of fuel, i.e., liquid hydrogen or liquid oxygen. Some of the rockets also use solid fuel instead of liquid fuel.
How do rockets work
The working of a rocket is based on Newton’s third law of motion. Rocket burns the fuel, i.e., liquid hydrogen or liquid oxygen, and throws out hot gases through its nozzle. This hot gas pushes the rocket forward. There is a direct relationship between the fuel burnt and speed of the rocket, the more the fuel burnt, the more is the speed of the rocket. The gas coming out through nozzle acts as action, and upward thrust acts as a reaction. You can better understand this phenomenon with the help of the example given in the first part of this article.
Rockets contain a large amount of fuel that helps to resist the earth’s gravitational force. Rocket needs to reach the extreme speed of about 27,990 km/h to leave the thick layers of atmosphere and enter the space.
Some of the rockets work in 2-3 stages, i.e., parts. These parts contain fuel. This process is known as staging. Rockets separate these parts to reduce the weight after using fuel from that part. The parts separated from the rocket falls into the ocean and are reused later.
The working of a rocket depends on the four crucial parts of the rocket. Rocket comprises of four parts:
The payload is the carrying capacity of the rocket. It is a cone-shaped part that contains the things, i.e. space shuttles, astronauts, satellites, etc. which are required to be sent in the space.
This part consists of liquid hydrogen or any other type of fuel. When it is burnt, it emits a tremendous amount of energy through the nozzle in terms of pressure and heat, acting as an upward thrust for the rocket.
Oxygen: This part of the rocket contains oxygen required by rocket engines to operate in space without air, i.e., airless environment.
See also: Top 12 Fastest Land Animals in the World
The rocket engine is the most critical and complex part of the rocket. The rocket engine is further divided into sections:
a) Mixing chamber
The mixing chamber acts as a powerhouse for the turbine. It contains a small amount of oxygen and fuel, which provides power to the turbine.
b) Power turbine
The power turbine helps in working with the fuel pump and oxygen pump and acts as a powerhouse for these pumps. It provides power to these pumps.
c) Fuel pump
The fuel pump is used to boost the fuel to the combustion chamber.
d) Oxygen pump
The oxygen pump helps in raising oxygen to the combustion chamber.
e) Combustion chamber
The combustion chamber is also known as a mixing tank, which helps in mixing the fuel and oxygen. In the combustion chamber, burning of fuel takes place, and a massive amount of energy and hot gas is produced.
Throat helps in increasing the pressure of the hot exhaust, i.e., hot gases generated by the combustion chamber.
The pressurized gas produced in the combustion chamber is thrown out through the nozzle after passing from the throat. Nozzle increases the speed of the gas because it is expanded as it is shaped like a bell.
I hope you have liked this article and will share this useful information with your friends. | 0.834808 | 3.274114 |
3D Simulations Disperse Some of the Mystery Surrounding Massive Stars
Three-dimensional (3D) simulations run at two of the U.S. Department of Energy’s national laboratory supercomputing facilities and the National Aeronautics and Space Administration (NASA) have provided new insights into the behavior of a unique class of celestial bodies known as luminous blue variables (LBVs) — rare, massive stars that can shine up to a million times brighter than the Sun.
Astrophysicists are intrigued by LBVs because their luminosity and size dramatically fluctuate on a timescale of months. They also periodically undergo giant eruptions, violently ejecting gaseous material into space. Although scientists have long observed the variability of LBVs, the physical processes causing their behavior are still largely unknown. According to Yan-Fei Jiang, an astrophysicist at UC Santa Barbara’s Kavli Institute for Theoretical Physics, the traditional one-dimensional (1D) models of star structure are inadequate for LBVs.
“This special class of massive stars cycles between two phases: a quiescent phase when they’re not doing anything interesting, and an outburst phase when they suddenly become bigger and brighter and then eject their outer envelope,” said Jiang. “People have been seeing this for years, but 1D, spherically-symmetric models can’t determine what is going on in this complex situation.”
Instead, Jiang is leading an effort to run first-principles, 3D simulations to understand the physics behind LBV outbursts — using large-scale computing facilities provided by Lawrence Berkeley National Laboratory’s National Energy Research Scientific Computing Center (NERSC), the Argonne Leadership Computing Facility (ALCF), and NASA. NERSC and ALCF are DOE Office of Science User Facilities.
Physics Revealed by 3D
In a study published in Nature, Jiang and his colleagues from UC Santa Barbara, UC Berkeley, and Princeton University ran three 3D simulations to study three different LBV configurations. All the simulations included convection, the action when a warm gas or liquid rises while its cold counterpart sinks. For instance, convection causes hot water at the bottom of a pot on a stove to rise up to the top surface. It also causes gas from a star’s hot core to push to its outer layers.
During the outburst phase, the new 3D simulations predict that convection causes a massive star’s radius to irregularly oscillate and its brightness to vary by 10 to 30 percent on a timescale of just a few days — in agreement with current observations.
“Convection causes the star to expand significantly to a much larger size than predicted by our 1D model without convection. As the star expands, its outer layers become cooler and more opaque,” Jiang said.
Opacity describes how a gas interacts with photons. The researchers discovered that the helium opacity in the star’s outer envelope doubles during the outburst phase, making it more difficult for photons to escape. This leads the star to reach an effective temperature of about 9,000 degrees Kelvin (16,000 degrees Fahrenheit) and triggers the ejection of mass.
“The radiation force is basically a product of the opacity and the fixed luminosity coming from the star’s core. When the helium opacity doubles, this increases the radiation force that is pushing material out until it overcomes the gravitational force that is pulling the material in,” said Jiang. “The star then generates a strong stellar wind, blowing away its outer envelope.”
Massive Simulations Required
Massive stars require massive and expensive 3D simulations, according to Jiang. So he and his colleagues needed all the computing resources available to them, including about 15 million CPU hours at NERSC, 60 million CPU hours at ALCF, and 10 million CPU hours at NASA. In addition, NERSC played a special role in the project.
“The Cori supercomputer at NERSC was essential to us in the beginning because it is very flexible,” Jiang said. “We did all of the earlier exploration at NERSC, figuring out the right parameters to use and submissions to do. We also got a lot of support from the NERSC team to speed up our input/output and solve problems.”
In addition to spending about 5 million CPU hours at NERSC on the early phase of the project, Jiang’s team used another 10 million CPU hours running part of the 3D simulations.
“We used NERSC to run half of one of the 3D simulations described in the Nature paper and the other half was run at NASA. Our other two simulations were run at Argonne, which has very different machines,” said Jiang. “These are quite expensive simulations, because even half a run takes a lot of time.”
Even so, Jiang believes that 3D simulations are worth the expense because illuminating the fundamental processes behind LBV outbursts is critical to many areas of astrophysics — including understanding the evolution of these massive stars that become black holes when they die, as well as understanding how their stellar winds and supernova explosions affect galaxies.
Jiang also used NERSC for earlier studies, and his collaboration is already running follow-up 3D simulations based on their latest results. These new simulations incorporate additional parameters — including the LBV star’s rotation and metallicity — varying the value of one of these parameters per run. For example, the speed from rotation is larger at the star’s equator than at its poles. The same is true on Earth, which is one of the reasons NASA launches rockets from Florida and California near the equator.
“A massive star has a strong rotation, which is very different at the poles and the equator. So rotation is expected to affect the symmetry of the mass loss rate,” said Jiang.
The team is also exploring metallicity, which in astrophysics refers to any element heavier than helium.
“Metallicity is important because it affects opacity. In our previous simulations, we assumed a constant metallicity, but massive stars can have very different metallicities,” said Jiang. “So we need to explore the parameter space to see how the structure of the stars change with metallicity. We’re currently running a simulation with one metallicity at NERSC, another at Argonne, and a third at NASA. Each set of calculations will take about three months to run.”
Meanwhile, Jiang and his colleagues already have new 2018 data to analyze. And they have a lot more simulations planned due to their recent allocation awards from INCITE, NERSC, and NASA.
“We need to do a lot more simulations to understand the physics of these special massive stars, and I think NERSC will be very helpful for this purpose,” he said.
This is a reposting of my news feature originally published by Berkeley Lab’s Computing Sciences. | 0.854571 | 4.012155 |
A 16-member international team of researchers that includes James Kennett, professor of earth science at UC Santa Barbara, has identified a nearly 13,000-year-old layer of thin, dark sediment buried in the floor of Lake Cuitzeo in central Mexico. The sediment layer contains an exotic assemblage of materials, including nanodiamonds, impact spherules, and more, which, according to the researchers, are the result of a cosmic body impacting Earth.
These new data are the latest to strongly support of a controversial hypothesis proposing that a major cosmic impact with Earth occurred 12,900 years ago at the onset of an unusual cold climatic period called the Younger Dryas. The researchers’ findings appear in the Proceedings of the National Academy of Sciences.
Conducting a wide range of exhaustive tests, the researchers conclusively identified a family of nanodiamonds, including the impact form of nanodiamonds called lonsdaleite, which is unique to cosmic impact. The researchers also found spherules that had collided at high velocities with other spherules during the chaos of impact. Such features, Kennett noted, could not have formed through anthropogenic, volcanic, or other natural terrestrial processes. “These materials form only through cosmic impact,” he said.
The data suggest that a comet or asteroid — likely a large, previously fragmented body, greater than several hundred meters in diameter — entered the atmosphere at a relatively shallow angle. The heat at impact burned biomass, melted surface rocks, and caused major environmental disruption. “These results are consistent with earlier reported discoveries throughout North America of abrupt ecosystem change, megafaunal extinction, and human cultural change and population reduction,” Kennett explained.
The sediment layer identified by the researchers is of the same age as that previously reported at numerous locations throughout North America, Greenland, and Western Europe. The current discovery extends the known range of the nanodiamond-rich layer into Mexico and the tropics. In addition, it is the first reported for true lake deposits.
In the entire geologic record, there are only two known continent-wide layers with abundance peaks in nanodiamonds, impact spherules, and aciniform soot. These are in the 65-million-year-old Cretaceous-Paleogene boundary layer that coincided with major extinctions, including the dinosaurs and ammonites; and the Younger Dryas boundary event at 12,900 years ago, closely associated with the extinctions of many large North American animals, including mammoths, mastodons, saber-tooth cats, and dire wolves.
“The timing of the impact event coincided with the most extraordinary biotic and environmental changes over Mexico and Central America during the last approximately 20,000 years, as recorded by others in several regional lake deposits,” said Kennett. “These changes were large, abrupt, and unprecedented, and had been recorded and identified by earlier investigators as a ‘time of crisis.’ “
Other scientists contributing to the research include Isabel Israde-Alcántara and Gabriela Dominguez-Vásquez of the Universidad Michoacana de San Nicólas de Hidalgo; James L. Bischoff of the U.S. Geological Survey; Hong-Chun Li of National Taiwan University; Paul S. DeCarli of SRI International; Ted E. Bunch and James H. Wittke of Northern Arizona University; James C. Weaver of Harvard University; Richard B.
Firestone of Lawrence Berkeley National Laboratory; Allen West of GeoScience Consulting; Chris Mercer of the National Institute for Materials Science; Sujing Zie and Eric K. Richman of the University of Oregon, Eugene; and Charles R. Kinzie and Wendy S. Wolbach of DePaul University.
Note : The above story is reprinted from materials provided by University of California – Santa Barbara. | 0.844193 | 3.665571 |
Sneak peek of Gaia's sky in colour
16 August 2017While surveying the positions of over a billion stars, ESA's Gaia mission is also measuring their colour, a key diagnostic to study the physical properties of stars. A new image provides a preview of Gaia's first full-colour all-sky map, which will be unleashed in its highest resolution with the next data release in 2018.
|Preliminary map of Gaia's sky in colour. Credit: ESA/Gaia/DPAC/CU5/DPCI/CU8/F. De Angeli, D.W. Evans, M. Riello, M. Fouesneau, R. Andrae, C.A.L. Bailer-Jones|
Stars come in a variety of colours that depend on their surface temperature, which is, in turn, determined by their mass and evolutionary stage.
Massive stars are hotter and therefore shine most brightly in blue or white light, unless they are approaching the end of their life and have puffed up into a red supergiant. Lower-mass stars, instead, are cooler and tend to appear red.
Measuring stellar colours is important to solve a variety of questions, ranging from the internal structure and chemical composition of stars to their evolution.
Gaia, ESA's astrometry mission to compile the largest and most precise catalogue of stellar positions and motions to date, has also been recording the colour of the stars it observes. The satellite was launched in December 2013 and has been collecting scientific data since July 2014.
A special effort in the Gaia Data Processing and Analysis Consortium (DPAC) is dedicated to the challenging endeavour of extracting stellar colours from the satellite data. While these measurements will be published with Gaia's second data release in April 2018, a preview of the Gaia sky map in colour demonstrates that the ongoing work is progressing well.
The new map, based on preliminary data from 18.6 million bright stars taken between July 2014 and May 2016 , shows the middle value (median) of the colours of all stars that are observed in each pixel. It is helpful to look at it next to its companion map, showing the density of stars in each pixel, which is higher along the Galactic Plane – the roughly horizontal structure that extends across the image, corresponding to the most densely populated region of our Milky Way galaxy – and lower towards the poles.
|Star density map. Credit: ESA/Gaia/DPAC/CU5/DPCI/CU8/F. De Angeli, D.W. Evans, M. Riello, M. Fouesneau, R. Andrae, C.A.L. Bailer-Jones|
Even though this map is only meant as an appetizer to the full treat of next year's release, which will include roughly a hundred times more stars, it is already possible to spot some interesting features.
The reddest regions in the map, mainly found near the Galactic Centre, correspond to dark areas in the density map: these are clouds of dust that obscure part of the starlight, especially at blue wavelengths, making it appear redder – a phenomenon known as reddening.
It is also possible to see the two Magellanic Clouds – small satellite galaxies of our Milky Way – in the lower part of the map.
The task of measuring colours is performed by the photometric instrument on Gaia. This instrument contains two prisms that split the starlight into its constituent wavelengths, providing two low-resolution spectra for each star: one for the short, or blue, wavelengths (330-680 nm) and the other for the long, or red, ones (640-1050 nm). Scientists then compare the total amount of light in the blue and red spectra to estimate stellar colours.
To precisely calibrate these spectra, however, it is necessary to know the position of each source on Gaia's focal plane to very high accuracy – in fact, to an accuracy that only Gaia itself can provide.
As part of the effort to extract physical parameters from the data sent back by the satellite, scientists feed them to an iterative algorithm that compares the recorded images of stars to models of how such images should look: as a result, the algorithm provides a first estimate of the star's parameters, such as its position, brightness, or colour. By collecting more data and feeding them to the algorithm, the models are constantly improved and so are the estimated parameters for each star.
|Artist's impression of Gaia. Credit: ESA/ATG medialab; background image: ESO/S. Brunier|
The first Gaia data release, published in September 2016, was based on less than a quarter of the total amount of data that will be collected by the satellite over its entire five-year mission, which is expected to observe each star an average of 70 times. This first release, listing unprecedentedly accurate positions on the sky for 1.142 billion stars, along with their brightness, contained no information on stellar colours: by then, it had not been possible to run enough iterations of the algorithm to accurately estimate additional parameters.
As the satellite continues to observe more stars, scientists have now had more time to feed data to the iterative algorithm to obtain estimates of stellar colours, like the ones shown in the new map. These estimates will be validated, over the coming months, as part of the overall data processing effort leading to the second Gaia data release.
Since the first data release, scientists across the world have been using Gaia's brightness measurements – which are obtained over the full G-band, from 330 to 1050 nm – along with datasets from other missions to estimate stellar colours. These studies have been applied to a variety of subjects, from variable stars and stellar clusters in our Galaxy to the characterisation of stars in the Magellanic Clouds.
Next year, the second release of Gaia data will include not only the position and G-band brightness, but also the blue and red colour for over a billion stars – in addition to the long-awaited estimates of stellar parallaxes and proper motions based on Gaia measurements for all the observed stars . This extraordinary dataset will allow scientists to delve into the secrets of our Galaxy, investigating its composition, formation and evolution to an unparalleled degree of detail.
The preliminary colour map shows a sample of stars that have been selected randomly from all Gaia stars with G-band magnitudes brighter than 17 and for which both colour measurements (from the blue and the red channels of Gaia's photometric instrument) are available.
Gaia's goal is to measure the parallax (a small, periodic change in the apparent position of a star caused by Earth's yearly revolution around the Sun, which depends on the star's distance from us) and proper motion (the motion of stars across the plane of the sky caused by their physical movement through the Galaxy) for over one billion stars. In the process, Gaia will measure also the brightness and colour of these stars, take spectra for a subset of them, and observe a variety of other celestial objects, from asteroids in our own Solar System to distant galaxies beyond the Milky Way. | 0.827948 | 3.846496 |
About this courseSkip About this course
In the Universe, high-energy cosmic rays are violently propagating in space. While we know these cosmic rays come from outside of the solar system, exactly how and where they originate is a mystery.
Professor Shoji Torii from Waseda University and many researchers from around the world, believe that understanding about their origin will help resolve the mysteries of the Universe, such as, supernova remnants, dark matter, and even the Universe’s evolution.
The most widely accepted theory is that high-energy cosmic rays are created by supernova explosions, but there are many other possibilities. Professor Torii hypothesis that these mysterious cosmic rays originate by the annihilation or decay of weakly interacting massive particles (WIMPS). That is, they are candidates of dark matter.
To examine this theory and to truly understand where high-energy cosmic rays originate and propagate, Professor Torii, along with the Japan Aerospace Exploration Agency (JAXA) and in collaboration with NASA and the Italian space Agency (ASI) have developed the Calorimetric Electron Telescope (CALET), now onboard the international space station.
Join us on this course on high-energy cosmic rays and get the latest research findings from the International Space Station to help unravel some of our greatest mysteries.
What you'll learnSkip What you'll learn
- The evolution of the universe
- The origin and propagation of cosmic rays
- The search for dark matter through cosmic ray observation
Meet your instructors
Pursue a Verified Certificate to highlight the knowledge and skills you gain$49.00
Official and Verified
Receive an instructor-signed certificate with the institution's logo to verify your achievement and increase your job prospects
Add the certificate to your CV or resume, or post it directly on LinkedIn
Give yourself an additional incentive to complete the course
Support our Mission
EdX, a non-profit, relies on verified certificates to help fund free education for everyone globally | 0.839621 | 3.201649 |
Earth Map in the Sky – Landforms as Constellations
Learn how to see the map of Earth in the starry sky.
Stars help us find our way. Stars are like a giant map in the sky that tells us where we are on the surface of the Earth. Sailors use them as a “map” to navigate the world. For thousands of years, the stars were stationary markers of latitude and longitude.
We are going to learn to map something new onto the sky: locations on the Earth! We can create an exciting new set of “constellations” out of the shapes of the continents on the Earth.
We live on a sphere so we can see half of the sky (a hemisphere) at any one moment. It’s easy to imagine half the Earth mapped onto half the sky. Keep reading to learn how.
Wherever you are on the Earth, when you look straight up (toward your zenith), you might see one star, but there are a bunch of other stars within view. All of the stars you see in the sky are directly overhead some other place on the Earth. Every place on Earth has their own set of stars directly overhead – their “zenith stars.”
Look up at any star in the night sky; that star is directly over some place on Earth. There are hundreds of “faraway zeniths” up there.
World Zeniths – See the Map of the Earth in the Sky
Every star maps to a location on Earth and every location on Earth maps to a star.
If you live in the western hemisphere, you can learn to look up and “see” the land borders of the North American and South American continents visible, projected into the sky like a giant painting on a curved ceiling. You can learn to see even more landforms in the sky – you can learn to see the entire western half of the Earth projected in the sky.
Visualize Countries in the Sky
We can learn to see country outlines in the sky. The key is to imagine yourself at the center of the Earth looking out into space “through” a translucent Earth surface.
Here is a good way to visualize these countries-in-the-sky even when you are on the surface. Imagine that you can look up and see your location at the zenith.
When I do this, I see southern New York state, Long Island jutting out into the water like a long pier, and the wide Hudson River emptying past New York City. Eastward is the dark expanse of the Atlantic Ocean and low on the eastern horizon are the countries of Europe and West Africa.
Westward in the sky, I can see the outline of the west coast of the US. Then, there is a big blank space of the Pacific Ocean and a spot near the western horizon that is Hawaii.
The Map of the Earth in the Sky is Reversed
There is one odd thing about the map as you see it in the sky… it’s reversed – as if seen in a mirror! This happens because we project the map lines outward into space toward the stars. When we look at the map this way it’s as if we are “inside” the Earth looking outward.
The map of the USA covers about 58˚ of sky from east-to-west. 58˚ is about 2x pinky-to-thumb (spread out all your fingers of both hands and touch thumbs). Your left pinky tip should be on your zenith. If you are in New York or somewhere on the east coast, the right pinky tip will indicate the approximate western edge of the USA.
Physical Astronomy – Stars Map to Places on Earth
Learn to see the zenith map in your sky using this Physical Astronomy technique.
Exercise 1: face south and point high in the sky.
Face south. Then, reach both hands straight up over your head and point above your head with both pointer fingers. You are pointing at your zenith. Now, bring both arms down until they are pointing one due east and one due west. You are pointing at two points in the sky that are zeniths for someone else.
When I do this exercise in New York, my left hand (the eastern) points at a spot in the starry sky that is the zenith star for someone in the country of Nigeria in West Africa. This is a location on the globe that is 6 time zones east. My right hand (the western) points at a spot in the sky that is the zenith for someone in the island state of Hawaii in the middle of the Pacific Ocean. This location is 6 time zones west of New York.
So, when I look at the eastern horizon sky I am looking at the starry sky that is already directly above a place 6 time zones ahead of me. I am looking at someone else’s zenith stars.
Exercise 2: Repeat exercise 1. But this time, face east.
Face east, point up. Now, bring your arms down and point toward the north and the south directions. This time your right hand points south and your left hand points north. Your right hand points at a spot in the sky that is over the city of Cuzco, Peru (the closest city to Machu Pichu) and your left hand points to sky that is over Yekaterinburg, Russia – the 4th largest city in Russia.
Secret! You Can See a Star That Another Person Can’t
If you do this physical astronomy exercise right after sunset, the eastern and southern zenith locations are in night, but the western and northern sky points are over Earth locations that still have daytime.
This means that you can see the star that is at their zenith, but they cannot see that star. For example, Seattle still has 3 hours of sunlight left in their day so stars are invisible behind blue sky. The city of Yekaterinburg is on the opposite side of the world and just after sunset in New York it faces the Sun and has a bright daytime sky!
We are on the night time side of the Earth and we can see the current zenith stars of Seattle and Yekaterinburg – but people who live in these cities cannot see them! They have to wait to rotate to the night time side of the Earth to see stars.
The Math – How High Up is the Zenith Map?
Project an imaginary map of the Earth into the sky. The map has to be the correct size so that when it is viewed from a distance it “covers” the same distances.
If a map is too close, it is just the same size as the territory. So, we have to choose the correct distance to project the zeniths. As the zenith map “projector screen” moves away from the Earth we see more of the borders of the Earth. But, at some point the distance of the map corresponds exactly to the faraway zeniths.
Our question is: “How far away from the Earth do you have to be so the landforms (like the continents) have an angular diameter that is equivalent to their “actual size” in the sky?” How far away does our imaginary zenith map USA (about 3000 miles wide) image have to be to cover 58 degrees of arc in the sky?
To answer this we need math.
The Zenith Map Distance from Earth
The Earth is approximately 24,901 miles in circumference at the equator. If we can see half the sky from any point on the Earth, then we can “see” half the Earth projected onto the sky by the zenith map. That means that for 180˚ of sky we can “see” about 12,450 miles of the Earth’s surface projected into space. 12,450/180 = 69 miles. When 1 degree of arc spans 69 equatorial miles the image is “at” the correct distance.
1 Degree of Sky equals 69 Miles
So, at the equator every degree of sky covers about 69 miles in every direction. As you go towards the poles the longitude degrees (east and west) cover less and less zenith map distance, but the latitude degrees (north and south) always stretch 69 miles. Every 15˚ of sky equals about 1035 (69*15) miles.
The distance between your pointer finger and your pinky (when you hold your arm and hand stretched out in front of you) is 15˚ – so you are measuring about 1035 miles on Earth with that sky measurement. One pinky width is equal to 1˚, which is 69 miles of zenith map!
The Math – Inverse Tangent and Angular Diameter
There is a simple calculation that helps us determine how far away something needs to be to fill just 1˚ of the sky. Here we use just a tiny drop of trigonometry to discover the “tangent of 1 degree.”
The tangent of 1˚ is 0.017455. The inverse of something is when you divide 1 by the number you want to invert. So, the inverse of 0.017455 (1/0.017455) is 57.29. The inverse of the tangent of 1˚ helps us figure out the distance something has to be to appear to be 1 degree angular diameter.
This page explains how to calculate distance from a known angular size. “When an object’s distance is 57.29 times its size, it has an angular size of 1 degree.”
So, 57.29 * 69 miles = 3,953 miles away! This is how far away the “map” has to be to show you your hemisphere of the Earth map. 3,953 miles is higher than low Earth orbit (LEO) satellites (lower than 1200 miles); it’s closer than geosynchronous satellites (at about 23,000 miles); and it’s about 1/60 the way to the Moon.
So, imagine that the Earth map is projected onto a screen – an imaginary celestial sphere, shell-shaped – that is quite close to the Earth and encircles us. It shows us our Earthen landforms and the oceans beside, superimposed in the sky.
We live on a sphere. When we look at out night sky we are able to see stars low on our horizon that are visible directly above someone else – one-quarter the way around the around the world in all directions.
If you live within 6 time zones of someone that means that you share some “simultaneous sky.” Anyone living further than 6 time zones away sees a completely different sky – unless you can see circumpolar stars that dip under the North Star. That means that you can see countries past the North Pole and down the other side of the globe.
Your zenith is yours – it is unique and changing all the time. Not even someone standing right beside you shares your zenith. You can use this idea of the zenith stars to comprehend the vast and mysterious experience of life on a sphere.
A list of extreme geographic points in the USA – Wikipedia – https://en.wikipedia.org/wiki/List_of_extreme_points_of_the_United_States | 0.800463 | 3.339902 |
#05: Gaia Service Module Thermal Balance/Thermal Vacuum testing completed
10 September 2012The Protoflight Model of the Gaia Service Module has successfully completed thermal balance and thermal vacuum testing in the SIMLES chamber at Intespace Toulouse. These tests verify the thermal performance of the spacecraft module under space conditions.
Once a spacecraft reaches space, its thermal environment changes dramatically compared to that experienced on Earth. The absence of air means that convection no longer occurs and all heat transfer takes place through conduction and radiation. Those parts of the spacecraft that are pointed towards deep space experience extreme cold - they are radiating towards a thermal sink with a temperature only just above 0 K. Any part of the spacecraft that is illuminated by the Sun experiences solar radiation unattenuated by Earth's atmosphere; the thermal design must ensure that these areas do not attain excessive temperatures and the mission design must keep the rest of the spacecraft in shadow at all times.
Thermal Balance (TB) testing checks the performance of the spacecraft by operating all of its systems in a vacuum and exposed to cooling shrouds, simulating the cold of deep space, until thermal equilibrium is achieved. Thermal Vacuum (TV) testing pushes the spacecraft subsystems to their thermal design limits using test heaters for the hot case, and verifies that they perform correctly.
Gaia will operate in a Lissajous orbit around L2, the second Lagrange point of the Sun-Earth system. This provides a fairly benign thermal environment but the rigorous requirements for the thermal stability of Gaia's payload have driven the thermal design of the spacecraft.
During the cruise to L2 and its operational lifetime, the -X face of Gaia, which is fitted with the solar arrays and main antenna, will point towards the Sun. The deployable sunshield that surrounds this face will protect the rest of the Service Module (SVM) and the Payload Module (PLM) from solar radiation.
Unlike Earth-orbiting satellites, which experience repeated thermal cycling as they move in and out of eclipse, Gaia will operate in a stable thermal environment; this means that the TB/TV testing can be simplified compared to that needed for most other missions.
SIMLES is a space simulation chamber; it is capable of producing conditions that mimic those that a spacecraft will encounter once in space. In addition to recreating the vacuum of space, the chamber reproduces the extreme cold of exposure to deep space by surrounding the item under test with thermal shrouds through which liquid nitrogen is pumped. This achieves a temperature of ~ 100 K - not as cold as deep space, which has a temperature of ~ 2.7 K, but close enough for verification of spacecraft thermal performance and validation of the thermal models used during the design process.
SIMLES is also able to simulate solar illumination, but these capabilities were not used during the Gaia SVM tests. Because of its size (> 10 m across when deployed), the sunshield could not be present during the test. However, the SVM is designed to be in shadow at all times, so no solar illumination was used; dedicated thermal shrouds were used instead.
The main body of the SIMLES chamber is suspended from the structure of the building that houses it. The bottom of the chamber can be lowered away from the main body for the installation of the spacecraft and instrumentation; the Gaia SVM was mounted on a tripod attached to the base of the chamber.
Thermal balance test
With the Gaia SVM mounted on the chamber bottom and all the instrumentation connected, the complete assembly was lifted into place to close the chamber. Vacuum pumping commenced on 23 July 2012 and a pressure of 10-6 mbar (10-4 Pa) was maintained for the duration of the TB/TV test campaign, which lasted until 10 August.
The PLM was not present during these tests; it will begin a separate, two-month long TB/TV test campaign later this year. For the SVM tests, the PLM thermal interface was simulated using thermal shrouds and test heaters. One cycle of TB testing was performed; all results were in accordance with expectations and have confirmed the validity of the thermal models.
Thermal vacuum test
For the TV test, the most critical component was the Phased Array Antenna (PAA). This is the primary means of communication between Gaia and the ground stations that receive science and housekeeping data and transmit commands to the spacecraft. Since the PAA will be permanently illuminated by the Sun, a dedicated thermal shroud was positioned close to it and its performance was verified at the highest operating temperature. The temperatures of the units inside the SVM were controlled by their self-dissipation or with the use of test heaters. External thermal shrouds were employed in critical locations.
One cycle of TV testing was performed. Temperatures inside the SVM varied from -20°C to +70°C; again, all results were as expected. The successful completion of this test campaign marks another step for Gaia in the preparations for launch by the end of next year.
Gaia will create a three-dimensional map of the Milky Way, in the process revealing information about its composition, formation and evolution. The mission will perform positional measurements for about one billion stars in our Galaxy and Local Group with unprecedented precision, together with radial velocity measurements for the brightest 150 million objects. Gaia is scheduled to launch in 2013 for a nominal five-year mission, with a possible one-year extension.
The spacecraft will operate in a Lissajous orbit around the second Lagrange point of the Sun-Earth system (L2). This location in space offers a very stable thermal environment, very high observing efficiency (since the Sun, Earth and Moon are all behind the instrument FoV) and a low radiation environment. Uninterrupted mapping of the sky will take place during the operational mission phase.
The Prime Contractor for Gaia is Astrium SAS, based in Toulouse, France. | 0.847722 | 3.446516 |
In more recent studies the universe appears as a collection of giant bubble-like voids separated by sheets and filaments of galaxies, with the superclusters appearing as occasional relatively dense nodes.
At the centre of the local supercluster there is a gravitational anomaly, known as the Great Attractor, which is drawing in galaxies over a region hundreds of millions of light years across. These galaxies are all redshifted, in accordance with the 'Hubble flow', as if they were receding from us and from each other, but the variations in their redshift are sufficient to reveal the existence of a concentration of mass equivalent to tens of thousands of galaxies.
The Great Attractor, discovered in 1986, lies at a distance of between 150 million and 250 million light years (250 million is the most recent estimate), in the direction of the Hydra and Centaurus constellations. In its vicinity there is a preponderance of large old galaxies, many of which are colliding with their neighbours, and/or radiating large amounts of radio waves.
Another indicator of large-scale structure is the 'Lyman alpha forest'. This is a collection of absorption lines which appear in the spectral lines of light from quasars, which are interpreted as indicating the existence of huge thin sheets of intergalactic (mostly Hydrogen) gas. These sheets appear to be associated with the formation of new galaxies.
Finally, there is evidence of quantisation of redshift. There have been numerous studies investigating this phenomenon, but it is not universally accepted as real, and is the subject of considerable controversy.
Some caution is required in describing structures on a cosmic scale because things are not always as they appear to be. Bending of light by gravitation can result in images which appear to originate in a different direction from their real source. This kind of optical illusion can obscure the actual processes taking place. Another possible optical illusion is where a galaxy cluster will contain galaxies with some random motion. When these random motions are converted to redshifts, the cluster will appear elongated, and this creates what is known as a finger of God; the illusion of a long chain of galaxies pointed at Earth.
There is much work in cosmology which attempts to model the large-scale structure of the universe. Using the big bang model and assumptions about the type of matter that makes up the universe, it is possible to predict the expected distribution of matter, and by comparison with observation work backward to support and refute certain cosmological theories. Currently, observations indicate that most of the universe must consist of cold dark matter. Models which assume hot dark matter or baryonic dark matter do not provide a good fit with observations. | 0.83945 | 4.092917 |
This normally involves isotope-ratio mass spectrometry. The precision of a dating method depends in part on the half-life of the radioactive isotope involved. For instance, carbon has a half-life of 5, years.
After an organism has been dead for 60, years, so little carbon is left that accurate dating cannot be established. On the other hand, the concentration of carbon falls off so steeply that the age of relatively young remains can be determined precisely to within a few decades. If a material that selectively rejects the daughter nuclide is heated, any daughter nuclides that have been accumulated over time will be lost through diffusion , setting the isotopic "clock" to zero. The temperature at which this happens is known as the closure temperature or blocking temperature and is specific to a particular material and isotopic system.
These temperatures are experimentally determined in the lab by artificially resetting sample minerals using a high-temperature furnace. As the mineral cools, the crystal structure begins to form and diffusion of isotopes is less easy.
At a certain temperature, the crystal structure has formed sufficiently to prevent diffusion of isotopes. This temperature is what is known as closure temperature and represents the temperature below which the mineral is a closed system to isotopes. Thus an igneous or metamorphic rock or melt, which is slowly cooling, does not begin to exhibit measurable radioactive decay until it cools below the closure temperature.
You May Also Like
The age that can be calculated by radiometric dating is thus the time at which the rock or mineral cooled to closure temperature. This field is known as thermochronology or thermochronometry. The mathematical expression that relates radioactive decay to geologic time is .
The equation is most conveniently expressed in terms of the measured quantity N t rather than the constant initial value N o. The above equation makes use of information on the composition of parent and daughter isotopes at the time the material being tested cooled below its closure temperature. This is well-established for most isotopic systems. Plotting an isochron is used to solve the age equation graphically and calculate the age of the sample and the original composition. Radiometric dating has been carried out since when it was invented by Ernest Rutherford as a method by which one might determine the age of the Earth.
In the century since then the techniques have been greatly improved and expanded. The mass spectrometer was invented in the s and began to be used in radiometric dating in the s. It operates by generating a beam of ionized atoms from the sample under test. The ions then travel through a magnetic field, which diverts them into different sampling sensors, known as " Faraday cups ", depending on their mass and level of ionization.
On impact in the cups, the ions set up a very weak current that can be measured to determine the rate of impacts and the relative concentrations of different atoms in the beams.
Radiometric Dating: Methods, Uses & the Significance of Half-Life
Uranium—lead radiometric dating involves using uranium or uranium to date a substance's absolute age. This scheme has been refined to the point that the error margin in dates of rocks can be as low as less than two million years in two-and-a-half billion years. Uranium—lead dating is often performed on the mineral zircon ZrSiO 4 , though it can be used on other materials, such as baddeleyite , as well as monazite see: Zircon has a very high closure temperature, is resistant to mechanical weathering and is very chemically inert.
Zircon also forms multiple crystal layers during metamorphic events, which each may record an isotopic age of the event. One of its great advantages is that any sample provides two clocks, one based on uranium's decay to lead with a half-life of about million years, and one based on uranium's decay to lead with a half-life of about 4. This can be seen in the concordia diagram, where the samples plot along an errorchron straight line which intersects the concordia curve at the age of the sample.
This involves the alpha decay of Sm to Nd with a half-life of 1.
- Geologic Age Dating Explained - Kids Discover;
- Navigation menu!
- You must create an account to continue watching!
- What is Radioactive Dating? - Definition & Facts - Video & Lesson Transcript | xycajahegopi.cf.
- Radiometric Dating.
Accuracy levels of within twenty million years in ages of two-and-a-half billion years are achievable. This involves electron capture or positron decay of potassium to argon Potassium has a half-life of 1.
- Radiometric dating - Simple English Wikipedia, the free encyclopedia;
- Radioactive Dating.
- good goth dating site?
- speed dating in dallas area!
- dating in maryland?
This is based on the beta decay of rubidium to strontium , with a half-life of 50 billion years. This scheme is used to date old igneous and metamorphic rocks , and has also been used to date lunar samples. Closure temperatures are so high that they are not a concern. Rubidium-strontium dating is not as precise as the uranium-lead method, with errors of 30 to 50 million years for a 3-billion-year-old sample.
A relatively short-range dating technique is based on the decay of uranium into thorium, a substance with a half-life of about 80, years. It is accompanied by a sister process, in which uranium decays into protactinium, which has a half-life of 32, years. While uranium is water-soluble, thorium and protactinium are not, and so they are selectively precipitated into ocean-floor sediments , from which their ratios are measured.
The scheme has a range of several hundred thousand years. A related method is ionium—thorium dating , which measures the ratio of ionium thorium to thorium in ocean sediment. Radiocarbon dating is also simply called Carbon dating. Carbon is a radioactive isotope of carbon, with a half-life of 5, years, which is very short compared with the above isotopes and decays into nitrogen. Carbon, though, is continuously created through collisions of neutrons generated by cosmic rays with nitrogen in the upper atmosphere and thus remains at a near-constant level on Earth. The carbon ends up as a trace component in atmospheric carbon dioxide CO 2.
A carbon-based life form acquires carbon during its lifetime. Plants acquire it through photosynthesis , and animals acquire it from consumption of plants and other animals. When an organism dies, it ceases to take in new carbon, and the existing isotope decays with a characteristic half-life years.
What is Radioactive Dating? - Definition & Facts
The proportion of carbon left when the remains of the organism are examined provides an indication of the time elapsed since its death. This makes carbon an ideal dating method to date the age of bones or the remains of an organism. The carbon dating limit lies around 58, to 62, years.
The rate of creation of carbon appears to be roughly constant, as cross-checks of carbon dating with other dating methods show it gives consistent results. In , he was awarded the Nobel Prize in Chemistry for this work. He first demonstrated the accuracy of radiocarbon dating by accurately estimating the age of wood from an ancient Egyptian royal barge of which the age was known from historical documents.
From Wikipedia, the free encyclopedia. Carbon Dioxide Information Analysis Center. Retrieved 1 May Retrieved from " https: Archaeology Carbon Radiometric dating.
Radiocarbon dating - Simple English Wikipedia, the free encyclopedia
Views Read Change Change source View history. In other projects Wikimedia Commons. Absolute age dating is like saying you are 15 years old and your grandfather is 77 years old. To determine the relative age of different rocks, geologists start with the assumption that unless something has happened, in a sequence of sedimentary rock layers, the newer rock layers will be on top of older ones. This is called the Rule of Superposition. This rule is common sense, but it serves as a powerful reference point. Geologists draw on it and other basic principles http: Relative age dating also means paying attention to crosscutting relationships.
Say for example that a volcanic dike, or a fault, cuts across several sedimentary layers, or maybe through another volcanic rock type. Pretty obvious that the dike came after the rocks it cuts through, right? With absolute age dating, you get a real age in actual years. Based on the Rule of Superposition, certain organisms clearly lived before others, during certain geologic times. The narrower a range of time that an animal lived, the better it is as an index of a specific time.
No bones about it, fossils are important age markers. But the most accurate forms of absolute age dating are radiometric methods. This method works because some unstable radioactive isotopes of some elements decay at a known rate into daughter products. This rate of decay is called a half-life. Half-life simply means the amount of time it takes for half of a remaining particular isotope to decay to a daughter product. Good discussion from the US Geological Survey:
- Radiometric dating!
- asian dating online.com.
- Radiometric dating - Wikipedia?
- drunk hook up yahoo;
- credit score dating snobs;
- Radiocarbon dating. | 0.816919 | 3.311293 |
Pluto and its moon, Charon
—Picture courtesy Johns Hopkins University Applied Physics Laboratory/Southwest Research Institute (JHUAPL/SwRI)
A few months earlier, Kansas native Clyde Tombaugh had been hired by the observatory to search for what was then being called Planet X.
During his lifetime, Lowell calculated where he thought the mystery planet should be and funded three separate searches for its whereabouts.
Although Lowell died unsatisfied in 1916, his fellows at the observatory continued the search and even built a special camera in 1929 for that purpose.
Tombaugh and a telescope
—Photograph courtesy NASA
The idea was to take pictures of the night sky along what’s known as the ecliptic plane, the band in the sky where most of the other planets orbit, and see if anything moved.
Sure, stars do migrate across the sky as Earth rotates. But the points of light stay in fixed positions relative to each other—making, for example, constellations possible.
However, the ancients noted that some stars “wandered” across the sky, popping up in different constellations over time. These wandering stars, we now know, are the other planets orbiting the sun.
Tombaugh’s job was to compare one picture from the camera with another taken a few days later using what’s called a blink comparator.
This device toggles between two images, kinda like a person quickly closing one eye then the other, to reveal any differences.
When Tombaugh loaded up the January 23 picture of the constellation Gemini with another taken on January 29, this is roughly what he saw:
Did you see it? That itteh bitteh dot is moving.
Ironically, Pluto is so itteh bitteh that it doesn’t really affect Uranus or Neptune at all: Lowell was wrong on that count, which makes it even more amazing that Tombaugh found the darn thing.
Now technically our man Clyde didn’t look at the two January pictures until February 18, 1930, so that’s the true anniversary of Planet X’s discovery. Later that year the planet was officially named Pluto, on the suggestion of an 11-year-old British lass.
New Horizons, by the by, launched four years ago this past Tuesday, and is slated to arrive at Pluto in 2014.
New Horizons lifts off from Kennedy Space Center
—Photograph by Scott Andrews, NIKON via NASA
The mission should answer some lingering questions about just what is this Pluto thing anyway and how does it fit in the solar system’s family album?
In the meantime, I’m gonna take a moment of silence on Saturday to honor Tombaugh and his persistent blinking. Pluto may be a dwarf planet now, Clyde baby, but you’re still the first American to discover a planet in my book. | 0.842838 | 3.359024 |
After a longer and colder winter than normally experienced here in Kentucky, everyone is eagerly looking forward to the return of spring. But have you ever thought about what causes the change of seasons here in Kentucky?
A brief history lesson is important because before the 15th Century, it was believed that the sun orbited around the earth. Nicolai Copernicus (1473-1543) radically changed our understanding of astronomy when he proposed that the sun, not Earth, was the center of the solar system. This led to our modern understanding of the relationship between the sun and the Earth. We now know that Earth orbits the sun elliptically and so is closer to the sun during part of its orbit and farther away at other times. Earth has seasons because our planet’s axis of rotation is tilted at an angle of 23.5 degrees relative to our orbital plane. Over the course of a year, the angle of tilt does not vary and so Earth’s northern axis is always pointing the same direction in space.
But the orientation of Earth’s tilt with respect to the sun, our source of light and warmth, does change as we orbit. The northern hemisphere is oriented toward the sun for half of the year and away from the sun for the other half. The same is true of the southern hemisphere. When the northern hemisphere is oriented/tilted toward the sun, that region of Earth warms because of the corresponding increase in solar radiation. The sun’s rays are striking that part of Earth at a more direct angle; it’s summer. When the northern hemisphere is oriented/tilted away from the sun, the sun’s rays are less direct, and that part of Earth cools; it’s winter. Seasons in the southern hemisphere occur at opposite times of the year from those in the northern hemisphere. Northern summer = southern winter.
The seasons are marked by solstices and equinoxes — astronomical terms that relate to Earth’s tilt. The solstices occur each year on June 20 or 21 (summer) and Dec. 21 or 22 (winter), and represent the official start of the summer and winter seasons. In the Northern hemisphere, the summer solstice is the longest daylight day of the year, with the direct rays of the sun striking the Tropic of Cancer (23.5 degrees north of the equator) while the winter solstice is the shortest daylight day of the year, with the direct rays of the sun striking the Tropic of Capricorn (23.5 degrees south of the equator).
The vernal equinox and autumnal equinox herald the beginning of spring and fall, respectively. At these times of the year, the sun is directly over Earth’s equator, and the lengths of the day and the night are equal over most of the planet. On March 20 or 21 of each year, the Northern Hemisphere reaches the vernal equinox and enjoys the signs of spring. At the same time, the winds turn colder in the Southern Hemisphere as the autumnal equinox sets in. The year's other equinox occurs on Sept. 22 or 23, when summer fades to fall in the north, and winter’s chill starts giving way to spring in the south.
So, today we welcome the first signs of spring, thanks to the vernal equinox!
This blog entry is written by Matt Lahm, Interpretive Ranger at The Parklands of Floyds Fork.
Being a donor-supported public park means we rely on donations, not tax dollars, for annual operations each year. Because of your generosity, we are able to maintain, program, and further develop this extraordinary public space without charging an entry fee. Together we work to enhance quality of life and help our community and economy grow in ways that are healthy, sustainable, and enjoyable for people of all ages. Help us reach our goal of sustaining The Parklands by becoming a Member today. Members make it happen!
Become a Member | 0.866899 | 3.762906 |
CoRoT celebrates its 300 days in orbit, since its launch on December 27th from Baonour. It started to collect scientific data on the February 2nd, and it works in normal scientific operations since 2 April 2007. It just finished its first very long sequence of observation (150 days) towards the region of the galactic centre and has turned towards the anticentre direction in order to keep the Sun in its back on the 15th of October.
Operations have been conducted from the centre de Mission in CNES Toulouse. It has then started its new long observation on October 23rd, which will last till next March.
CoRoT has observed 3 carefully selected regions of the sky: an area in the direction of the constellation of the Unicorn (Monoceros) during 60 days followed by a short (26days) and a very long (150 days) pointing in the opposite direction, in the constellation of the Snakes tail (Serpens Cauda). CoRoT obtains "light curves", i.e. it measures the light coming from a very large number of stars with unprecedented precision for a hitherto unheard length of time. During each set of observations more than 12000 light curves have been obtained, with almost uninterrupted data.
It is now clear that CoRoT will instigate a breakthrough in both of the fields of science that it applies to. The scientific impact of CoRoT relies on its three major characteristics never reached before for which the satellite fulfils and surpass its originals specifications:
the precision with which the satellite is working, which is set by physical laws -- not by the working of the instrument (the data are thus photon noise limited essentially over all magnitude ranges).
the duration of the observations on the same star
the continuity of these observations, which have almost no interruption over these very long periods. And CoRoT finds that essentially every star it observes varies.
CoRoT is discovering exo-planets at a rate only set by the available resources to follow up the detections,
CoRoT has detected solar type oscillations in solar type stars at a level so far unprecedented apart for observations of our own Sun,
CoRoT is observing all kinds of activity on a large domain of frequencies from multi-mode oscillations, signature of erratic superficial motions, to the signature of differential rotation as seen by the different periods of the passage of sunspots at different latitudes. This is demonstrated by this example. The data here cover 120 days of uninterrupted observation. It is important to note that what is presented here is raw data (so-called N0 data), and that further refinements will follow shortly.
The scientific interpretation of these data will be very soon presented in several papers being prepared for peer reviewed journals.
On this "light curve" one can immediately see a variety of variabilities and time scales.
A "periodic" variation over approximately 1.5 days,
A long term variation, producting a sort of beat phenomenon with a period of roughly 40 days. Let's remark that the continuity of the observations over 120 days was necessary to detect this effect. These large scale variations are probably due to the rotation of the star, which has a non uniform surface (as seen on a smaller scale on the Sun), but it is too early to give a firm interpretation.
very narrow spikes occurring regularly superimposed on top of this long term variations. They are the signature of a smaller body orbiting the star with a period of almost 5 days. The nature of this object (a very big planet or a very small star) will be confirmed by follow-up observations on the ground. | 0.842752 | 3.872813 |
Earlier this year, Mike Brown—an astronomer at Caltech who is famous for his role in the (somewhat controversial) planetary demotion of Pluto—offered, seemingly by way of atonement, evidence for the existence of a large planet in the outer Solar System.
But this distant world would be no pipsqueak, like the other icy, planetary embryos that we’ve discovered in the Kuiper Belt.
In fact, Brown and his team calculated a mass for the object of approximately 10 times the Earth’s, suggesting that it was the incipient core of a giant planet (like Jupiter or Saturn) that was jostled in the early phases of the Solar System’s formation, and rudely ejected into an astonishing 149 billion-kilometer (92 billion-mile) orbit, or nearly 75 times more distant than Pluto.
That means the hypothetical planet’s “year” can last anywhere from 10,000-20,000 terrestrial years.
Now, the evidence for the existence of such an object is indirect—specifically, the effect it seems to be having on neighboring outer Solar System bodies, called Kuiper Belt Objects (KBOs). Six of these objects had been detected with wildly eccentric orbits, including the large planetoid Sedna, with an orbital period of 11,000 years.
PLANET X, NEMESIS, AND ALL THE REST
“Hey Planet Nine fans, a new eccentric KBO was discovered. And it is exactly where Planet Nine says it should be,” Mike Brown tweeted. Furthermore, he says, the new object “takes the probability of this being a statistical fluke down to ~.001% or so.”
Whether this hypothetical, 10 Earth-mass planet is the famed “Nemesis” object, said to be responsible for cometary influxes that cause mass extinctions on Earth, remains to be seen (though astronomers are, understandably, skeptical); but with the detection of uo3L91, the case for something massive lurking in the outer Solar System, and affecting the orbits of distant planetoids, just got a little bit stronger.
But we’ll have to wait and see. Perhaps more such detections will let us nail down the giant planet’s orbital path; maybe then we’ll be able to snap a picture of it with some next-gen Earth-based telescope.
Till then, keep your eyes peeled for more eccentric KBOs.
Source – Futurism | 0.860811 | 3.843015 |
XMM-Newton spies first clear X-ray flares from massive stellar lighthouse
26 February 2018In 2014, ESA's XMM-Newton spotted X-rays emanating from the massive star Rho Ophiuchi A and, last year, found these to ebb and flow periodically in the form of intense flares – both unexpected results. The team has now used ESO's Very Large Telescope to find that the star boasts a strong magnetic field, confirming its status as a cosmic lighthouse.
|XMM-Newton view of massive star Rho Ophiuchi A. Credit: ESA/XMM-Newton; I. Pillitteri (INAF–Osservatorio Astronomico di Palermo)|
Stars like the Sun are known to produce strong X-ray flares, but massive stars appear to be very different. In stars upwards of eight solar masses X-ray emission is steady, and no such star had been confidently observed to repeatedly flare in this part of the spectrum – until recently.
In 2014, a team of scientists used ESA's XMM-Newton space observatory to observe a massive star named Rho Ophiuchi A. This star sits at the heart of the Rho Ophiuchi Dark Cloud, a nearby region known to be actively forming new stars. Surprisingly, the data showed an abundance of X-rays streaming out from the star, prompting the team to look closer.
"We observed the star with XMM-Newton for almost 40 hours and found something even more unexpected," says Ignazio Pillitteri of the INAF–Osservatorio Astronomico di Palermo, Italy, and leader of the research team.
"Rather than a smooth, steady emission, the X-rays pulsed periodically outwards from Rho Ophiuchi A, varying over a period of roughly 1.2 days as the star rotated – like an X-ray lighthouse! This is quite a new phenomenon in stars bigger than the Sun."
|X-ray flares from Rho Ophiuchi A. Credit: ESA/XMM-Newton; I. Pillitteri (INAF–Osservatorio Astronomico di Palermo)|
Rho Ophiuchi A is far hotter and more massive than our parent star. It remains unknown how X-rays are generated in such stellar heavyweights; one possibility is a strong intrinsic magnetism, which would be observable via signs of surface magnetism. However, how such a magnetic field would come to be – and how it would be linked to any X-ray emission – remains unclear.
"We guessed that there may be a giant active magnetic spot on the surface of Rho Ophiuchi A – a bit like a sunspot, only far bigger and more stable," adds Pillitteri.
"As the star rotates, this spot would come in and out of view, causing the observed pulsing X-rays. However, this idea was somewhat unlikely; spots on stars form when an interior magnetic field pops out to the surface, and we know that only one in ten massive stars has a measurable magnetic field."
Another way the pulsing 'lighthouse effect' could be created is via a lower-mass orbiting companion that added its own copious X-rays to the light attributed to Rho Ophiuchi A; this X-ray emission would vary in strength as the hypothetical smaller star crossed in front of and behind Rho Ophiuchi A during its 1.2-day orbit. The team also considered this possibility: that Rho Ophiuchi A could have a small, unseen, lower-mass companion in a very tight orbit.
"To find out one way or another, we rushed to get magnetic measurements of Rho Ophiuchi A using one of the largest ground-based telescopes in existence: ESO's Very Large Telescope," says Lida Oskinova of the University of Potsdam, Germany, a member of the international team that conducted the study.
"Excitingly, these measurements confirmed one of our predictions and showed that the X-rays are most likely linked to magnetic structures on the surface of the star."
These measurements were made in visible light using a technique known as spectropolarimetry, which involves studying various wavelengths of polarised light emanating from a star. The data showed Rho Ophiuchi A to have an intense magnetic field some 500 times stronger than that of the Sun.
"Such a strong field is easily capable of producing the kind of flares we spotted," says Pillitteri.
"This confirms that what we discovered using XMM-Newton were indeed X-ray flares on Rho Ophiuchi A, that massive stars can be magnetically active – as shown by the optical observations – and that this activity can be seen in X-rays."
The combined data indicate that Rho Ophiuchi A is the only star of its type to have a confirmed active magnetic region on its surface that emits X-rays. Hunting for similar behaviour in stars like Rho Ophiuchi A will help scientists to understand how prevalent this phenomenon is, and unravel more about the magnetic properties of such stars.
"This study is an important one in our exploration of massive stars – there's much we still don't understand about these objects," says Norbert Schartel, ESA XMM-Newton Project Scientist.
"Together, the extraordinary capabilities of XMM-Newton and the Very Large Telescope have now uncovered another piece of the puzzle."
"As a bonus, it illustrates the process of science very well – of finding something interesting or unusual, investigating and coming up with a few possible hypotheses, and following up with more observation to figure out which is correct. It's a wonderful example of an international collaboration between telescopes, both in orbit and on the ground, working together to explore and explain the phenomena we see throughout the cosmos."
Notes for editors
These findings are described in three papers published in the journal Astronomy & Astrophysics: "Smooth X-ray variability from ρ Ophiuchi A+B: A strongly magnetized primary B2 star?" by Pillitteri et al. (2014), doi: 10.1051/0004-6361/201424243; "The early B-type star Rho Ophiuchi A is an X-ray lighthouse" by Pillitteri et al. (2017), doi: 10.1051/0004-6361/201630070; and "Detection of magnetic field in the B2 star ρ Oph A with ESO FORS2" by Pillitteri et al. (2018), doi: 10.1051/0004-6361/201732078.
More information about ESA's XMM-Newton mission can be found here.
The optical observations were performed using the FOcal Reducer/low dispersion Spectrograph 2 (FORS2) instrument on the European Southern Observatory's Very Large Telescope, located in Chile.
For further information, please contact:
INAF–Osservatorio Astronomico di Palermo
Tel: +39 091 233 420
Institute of Physics and Astronomy, University of Potsdam
Tel: +49 331-9775910
XMM-Newton Project Scientist
European Space Agency | 0.893274 | 3.889728 |
Saturday, August 18, 2018
Friday, August 17, 2018
Thursday, August 16, 2018
Wednesday, August 15, 2018
Tuesday, August 14, 2018
Sunday, August 12, 2018
"All year long as Earth revolves around the sun, it passes through streams of cosmic debris. The resulting meteor showers — like the Perseids that are peaking on Sunday, August 12 — can light up night skies from dusk to dawn, and if you’re lucky you might be able to catch one.
If you spot a meteor shower, what you’re really seeing is the leftovers of icy comets crashing into Earth’s atmosphere. Comets are sort of like dirty snowballs: As they travel through the solar system, they leave behind a dusty trail of rocks and ice that lingers in space long after they leave. When Earth passes through these cascades of comet waste, the bits of debris — which can be as small as grains of sand — pierce the sky at such speeds that they burst, creating a celestial fireworks display.
A general rule of thumb with meteor showers: You are never watching the Earth cross into remnants from a comet’s most recent orbit. Instead, the burning bits come from the previous passes. For example, during the Perseid meteor shower you are seeing meteors ejected from when its parent comet, Comet Swift-Tuttle, visited in 1862 or earlier, not from its most recent pass in 1992.
That’s because it takes time for debris from a comet’s orbit to drift into a position where it intersects with Earth’s orbit, according to Bill Cooke, an astronomer with NASA’s Meteoroid Environment Office.
The name attached to a meteor shower is usually tied to the constellation in the sky from which they seem to originate, known as their radiant. For instance, the Orionid meteor shower can be found in the sky when stargazers have a good view of the Orion constellation."
The Perseids and More Meteor Showers That Will Light Up Night Skies in 2018 - The New York Times | 0.879351 | 3.701275 |
A large sunspot has been the site of several major eruptions in recent days, including one Thursday that was the largest of the series. Charged particles from the events have been hammering orbital spacecraft.
The storms caused minor glitches on the Sun-watching SOHO spacecraft and forced scientists to put two of its instruments into "safe mode," not unlike an electronic nap.
The sunspot group is "one of the most flaring regions of the last few years," said Bernhard Fleck, SOHO Project Scientist with the European Space Agency (ESA).
Sunspots are regions of intense magnetic energy, cooler than the surrounding solar surface. They're a bit like corks in a shaken bottle of champagne, and when they cut loose, radiation and matter are flung into space. Flares of visible light and X-rays are rated M for medium and X for strong, with an accompanying number that signifies further intensity.
The sunspot group, numbered 720, has delivered 15 M-class flares and five X-class flares. At around 2 a.m. ET Thursday, it unleashed an X7, one of the most intense measured in recent years.
"This activity is significant," said NOAA space weather forecaster Bill Murtagh. "However, it is considerably less intense than the activity observed during the 'Halloween Storms' of 2003."
The 2003 rampage, which included 10 X-class flares, knocked out two Earth-orbiting satellites and even crippled an instrument aboard a Mars orbiter.
Some flares are accompanied by coronal mass ejections (CMEs), which are clouds of charged subatomic particles that race outward at millions of miles per hour. They can damage satellites and occasionally trip power grids on Earth. No serious effects have been attributed to this month's storms. But scientists are on watch.
"Even before the peak of the flare, energetic protons were pummeling SOHO as well as geostationary spacecraft around Earth," Fleck said.
SOHO (Solar and Heliospheric Observatory) is run by ESA and NASA. It and the geostationary satellites orbit much higher than many other satellite and are more directly exposed to storms.
SOHO uses stars to guide it and maintain its attitude. In the past, loss of a guide star could throw the probe into an emergency. A software upgrade was done in 1999 after such a problem.
"With the improved software, several stars are tracked at the same time, and losing the primary one is no big deal as long as there are more stars left to track," Fleck said. Good thing, because these latest tempests have proved challenging.
"During the first few hours of the storm, four stars were lost," Fleck said. Two of SOHO's instruments were manually put in safe mode by turning down high voltages, he added.
Residents of the far north have enjoyed fantastic displays of the Northern Lights during the storm series. The aurora, as they are also known, are triggered when the solar storms hit Earth's protective magnetosphere, causing charged particles to stream into the upper atmosphere, where they excite molecules into glowing.
The residents of the International Space Station are relatively safe from most solar storms, because they orbit inside the planet's protective magnetosphere.
In general, the Sun is near a minimum of activity in a roughly 11-year cycle. But sunspots, flares and eruptions can occur anytime during the cycle. The storminess is likely to subside in coming days as the sunspot rotates to the back side of the Sun.
- Sun Cam
- Aurora Meter
- What is the Aurora?
- Anatomy of the Sun
- Best Sun Pictures Ever
|About the Sun|
The Sun makes up 99.86 percent of the solar system's mass and provides the energy that both sustains and endangers us.
|About the Sun|
|About the Sun|
Scientists estimate that it takes a few hundred thousand years for photons, the basic units of light, to escape the Sun's core and reach the surface. They arrive at Earth about 8-and-a-half minutes later.
If you stood on the Sun, its gravity would make you feel 38 times more heavy than you do on Earth. We don't recommend trying.
Starry Night software brings the universe to your desktop. Map the sky from your location, or just sit back and let the cosmos come to you. | 0.864225 | 3.560919 |
For the first time, scientists observe "devouring of planet" by young star
It will take further study to confirm the star's iron influx came from a planet or two, but the initial theory is quite compelling.
The star, named RW Aur A and located in the Taurus-Auriga constellation, is a few million years old; it’s been watched and studied by astronomers since before World War II—1937, in fact.
The light from this star has dimmed periodically over the last 80 years for as long as a month, according to NASA.
The phenomenon has became much more frequent since 2011, causing scientists to pay even more attention to the star; the Chandra X-ray Observatory and telescope, highly sensitive to x-rays, began to be focused much more on it since then in an effort to collect enough data to figure out what was happening.
And that’s when the light bulb came on. Specifically, the detection of a high quantity of iron around the star; this was a new phenomenon, when compared with the same star in 2013, and the best possible solution is that a planet—perhaps more than one—collided with the star and was swallowed up by it. The dust, rocks, particles, and gas remaining would explain the dimming effect.
This artist’s illustration depicts the destruction of a young planet or planets, which scientists may have witnessed for the first time using data from NASA’s Chandra X-ray Observatory. Credits: Illustration: NASA/CXC/M. Weiss; X-ray spectrum: NASA/CXC/MIT/H. M.Günther
“Computer simulations have long predicted that planets can fall into a young star, but we have never before observed that. If our interpretation of the data is correct, this would be the first time that we directly observe a young star devouring a planet or planets,” said Hans Moritz Guenther, research scientist at MIT’s Kavli Institute for Astrophysics and Space Research. Guenther headed up the study.
There’s a second theory that is also plausible, though less favored: The star’s sister, RW Aur B, may in fact pass close enough to RW Aur A that the latter actually rips particles of iron from the disk that surrounds the former. As NASA explained:
“RW Aur A is located in the Taurus-Auriga Dark Clouds, which host stellar nurseries containing thousands of infant stars. Very young stars, unlike our relatively mature sun, are still surrounded by a rotating disk of gas and clumps of material ranging in size from small dust grains to pebbles, and possibly fledgling planets. These disks last for about 5 million to 10 million years.”
This second theory holds that within those clumps of material are iron particles, and they are jarred loose by the gravitational forces of RW Aur B passing by.
It’s not settled yet; future efforts will continue building data from Chandra, as well as compare data from the multiple decades that the star has been studied to see if there are clues about planet-eating, collisions, or perhaps something else entirely.
And if the thought of a planet-eater made you think of Star Trek: The Doomsday Machine, well, you’re in good company.
To create wiser adults, add empathy to the school curriculum.
- Stories are at the heart of learning, writes Cleary Vaughan-Lee, Executive Director for the Global Oneness Project. They have always challenged us to think beyond ourselves, expanding our experience and revealing deep truths.
- Vaughan-Lee explains 6 ways that storytelling can foster empathy and deliver powerful learning experiences.
- Global Oneness Project is a free library of stories—containing short documentaries, photo essays, and essays—that each contain a companion lesson plan and learning activities for students so they can expand their experience of the world.
Philosophers like to present their works as if everything before it was wrong. Sometimes, they even say they have ended the need for more philosophy. So, what happens when somebody realizes they were mistaken?
Sometimes philosophers are wrong and admitting that you could be wrong is a big part of being a real philosopher. While most philosophers make minor adjustments to their arguments to correct for mistakes, others make large shifts in their thinking. Here, we have four philosophers who went back on what they said earlier in often radical ways.
Numerous U.S. Presidents invoked the Insurrection Act to to quell race and labor riots.
- U.S. Presidents have invoked the Insurrection Act on numerous occasions.
- The controversial law gives the President some power to bring in troops to police the American people.
- The Act has been used mainly to restore order following race and labor riots.
Got any embarrassing old posts collecting dust on your profile? Facebook wants to help you delete them.
- The feature is called Manage Activity, and it's currently available through mobile and Facebook Lite.
- Manage Activity lets users sort old content by filters like date and posts involving specific people.
- Some companies now use AI-powered background checking services that scrape social media profiles for problematic content.
Researchers from Japan add a new wrinkle to a popular theory and set the stage for the formation of monstrous black holes. | 0.872659 | 3.840257 |
Observing the Moon
The object of the month this time is the closest celestial body to us: The Moon.
The Moon plays a big part in Astronomy for a number of reasons, the main one being light. Although the Moon does not generate light itself, it acts as a giant reflector for the sun. When the Moon is full it reflects enough sunlight to create shadows on the ground. It is even possible for the Moon to reflect sunlight that is itself reflected from the Earth. This is called earthshine.
Earthshine occurs during the new Moon lunar phase when a small amount of sunlight is reflected from the Moon creating a crescent Moon and sunlight reflected from the Earth illuminates the rest of the Moon. The earthshine is far fainter than the moonshine but it does let you see the entire Moon.
For astronomers the Moon can be quite inconvenient. The light it reflects has the effect of flooding the night skies and obliterating the faint stars, galaxies and nebula for all periods other than around new Moon. Of course this does give us at least one celestial body to observe, which is probably why the Moon is the most popular object for astronomers.
The phases of the Moon determine what an observer can see. At new Moon there is nothing visible of the moon and with clear dark skies the wonders of the Universe are opened up to us. As the nights progress a crescent Moon appears then fills out over the nights until seven days later the waxing Moon is at first quarter or half moon. During this period the Moon rises during the day and sets in the early evening, gradually rising later in the morning and setting later in the evening. A further seven days later there will be a full Moon when the moon rises at dusk and sets at dawn and is in the sky all night. During the period from first quarter to last quarter the skies will be washed out and little observing can take place. Finally as the waning Moon enters the last quarter it rises later in the evening and sets during the daytime. It is during this period that observing during the night can take place before the Moon exerts its influence on the night skies.
To observe the Moon one might expect that the best time would be during the time around full Moon. To a certain extent that would be correct, but really the proper answer to the question is any time that the Moon is in the sky, even during the day.
Although at full Moon the entire surface of the Moon will be visible this is actually not the best time to look at it. The best details are observed during the waxing and waning of the Moon. It is at this time that the terminator can be seen. The area around the terminator shows a lot more detail of the surface of the Moon due to the angle that the sunlight hits it. This creates shadows revealing much more detail in the craters, which look completely different than when they are fully illuminated. As the days progress and the more of the Moon is revealed different parts of the surface are exposed at the terminator.
Viewing the moon can be done without any optical equipment. The seas are clearly visible and, of course, the daily changes between crescent Moon and full Moon can be seen.
A small pair of binoculars will enable more of the detail of the Moon to be discovered, the major craters of Tycho and Copernicus are clearly visible along with more minor ones. The seas become more delineated with the boundaries being particularly visible.
Moving up to a telescope at low power the entire sphere of the Moon can be viewed in the eyepiece. Changing to a higher magnification allows you to zoom in on the detail of the lunar surface, and will reveal great delights along the line of the terminator. At these higher magnifications you are more subject to the turbulence of the atmosphere, which will make the view shimmer in the thermals, but on a steady night will allow intricate details to pop into focus. The trick is to keep looking and over time you will get some stunning views.
Imaging the Moon
Imaging the Moon can be quite a challenge, the main problem being getting the exposure correct. To achieve this you really need a camera with manual controls. When looking at the Moon it appears quite large in the sky, which it is compared to the stars, but through a camera lens it is quite small. Most cameras will average the exposure for an image which means that with the majority of the frame being dark the surface of the Moon will be vastly overexposed and no detail will be visible. When setting the exposure manually the effects of the background can be eradicated and the details of the Moon can be imaged.
There are a multitude of ways that the Moon can be imaged. Firstly it can be captured as part of a landscape image, this will be very tricky with exposure settings as mentioned above. The best option for a landscape is to merge two images, one exposed for the landscape and one for the Moon.
A friend of mine takes an artistic approach to imaging the Moon. Using a long telephoto lens of about 500mm he gets a nice large Moon but he focuses on something like a leaf or branch in front of the Moon. This throws the Moon out of focus acting as a circular light source with the subject in the foreground.
It is even possible to image the Moon and the Sun together in an eclipse without filters, but great care needs to be taken to avoid damage to your camera, and more importantly yourself. Never look at the Sun directly or through a telescope without the correct filter to ensure that you do not damage your eyes. If in doubt do not do it. The eclipse image here was taken using a special solar filter. The second landscape image of the partial eclipse was taken at sunset over Monument Valley when it was safe to take a photograph with no filters.
Two weeks after a full eclipse there will be a lunar eclipse. During the lunar eclipse you can safely take images of the moon as the Sun will not be in the sky. During the lunar eclipse, which always occurs during full Moon, the Moon passes through the shadow of the Earth. As it enters the shadow the Moon dims, but with no sharp delineation as with a solar eclipse, when it enters the Earth’s shadow it turns red, which leads to the term “Blood Moon”.
A more traditional image of the Moon can be taken with a medium telephoto lens on a DSLR camera. Using a tripod to steady the camera an image can be taken which will show good detail of the Moon. The image will only cover a very small part of the frame, but can be cropped to produce a reasonable sized picture with lots of detail. It is always good practice to take a number of images at different exposures to enable you to process and select the best ones on your computer. The example images were taken with a Canon T3i camera and a 200mm lens with an exposure of 1/125 second at f11 and ISO 100. This was for a full Moon, and can be used as a starting point. At other times of the month the Moon will reflect a lot less light so the exposure will need to be adjusted accordingly.
For even closer images then you need to start using a telescope with a DSLR attached to it. This setup is the type that was described in the previous issue. Telescopes have a focal length starting at around 450mm (in DSLR terms) and going right up to 1250mm and beyond. The same techniques apply as for shooting with a DSLR and normal lens with the exception that the f-stop is fixed so the ISO and shutter speed need to be adjusted to get the best exposure.
To get really close images of the features of the Moon a Planetary or WebCam attached to a telescope is required. This will allow you to get incredibly close pictures of the lunar landscape. The problem with this is that the atmosphere of the Earth makes the images very distorted and unstable. To overcome this a technique has been developed that takes a video then processes the individual frames of the video dropping the bad ones and combining the good ones to create some stunning images of the features of the Moon.
Next issue I will cover the basics of this imaging and processing which applies to planets as well as the Moon. | 0.854315 | 3.660608 |
In "An Extremely Energetic Supernova from a Very Massive Star in a Dense Medium" -- given scientists' usual efforts not to overplay their discoveries, the very title indicates how remarkable this is -- a team led by Matt Nicholl of the University of Birmingham describes a massive explosion of a star in a yet-unnamed galaxy four billion light years from us that released energy on the order of 10^52 ergs -- that's a 1 followed by fifty-two zeroes -- which is ten times higher than the previous record-holder.
The galaxy is a dwarf elliptical galaxy, and seems to be similar in structure to the Magellanic Clouds, the two dwarf galaxies near the Milky Way. This supernova (SN2016aps) is something else again, outshining its entire host galaxy by a large margin. "SN2016aps is spectacular in several ways," said Edo Berger, Harvard University astronomy professor and co-author on the paper, in a press release. "Not only is it brighter than any other supernova we’ve ever seen, but it has several properties and features that make it rare in comparison to other explosions of stars in the universe... The intense energy output of this supernova pointed to an incredibly massive star progenitor. At birth, this star was at least a hundred times the mass of our Sun."
SN2016aps [Image from the Panoramic Survey Telescopes and Rapid Response System (Pan-STARRS)]
"Spectroscopic observations during the followup study revealed a restless history for the progenitor star,” said study lead author Matt Nicholl. "We determined that in the final years before it exploded, the star shed a massive shell of gas as it violently pulsated. The collision of the explosion debris with this massive shell led to the incredible brightness of the supernova. It essentially added fuel to the fire."
The fact that this supernova is four billion light years away should be reassuring; not only is that a "far piece from here" (as my grandma used to describe anything more than about five miles away), but this means the explosion occurred four billion years ago. The fact that there has never been anything seen on this magnitude from nearer to us (and therefore, that happened more recently) may mean not only that such events are extremely rare, but that they were more likely in the early universe than they are now.
Which is a relief. As spectacular as this would be, seeing it from close range would be inadvisable. Fans of the original Star Trek might remember the episode "All Our Yesterdays," wherein an entire planet's population jumped into the past to escape their host star's impending supernova, and the intrepid members of the Enterprise's away team get trapped in different pasts (of course), almost get killed and/or permanently stuck there (of course), and all get away with seconds to spare (of course). The final moments -- the star blowing up, and the Enterprise hauling ass to get away -- is pretty dramatic, but underplays the actual magnitude of such an event. Warp drive notwithstanding, being this close to a supernova would be a good way to get yourself vaporized.
Anyhow, that's our astronomical superlative of the week. If April keeps going this way, you have to wonder what's next. Me, I hope that it's a light show from Comet ATLAS, although sadly that's looking less and less likely. Other than that? We'll just have to keep our eyes on the skies.
This week's Skeptophilia book recommendation of the week is brand new -- only published three weeks ago. Neil Shubin, who became famous for his wonderful book on human evolution Your Inner Fish, has a fantastic new book out -- Some Assembly Required: Decoding Four Billion Years of Life, from Ancient Fossils to DNA.
Shubin's lucid prose makes for fascinating reading, as he takes you down the four-billion-year path from the first simple cells to the biodiversity of the modern Earth, wrapping in not only what we've discovered from the fossil record but the most recent innovations in DNA analysis that demonstrate our common ancestry with every other life form on the planet. It's a wonderful survey of our current state of knowledge of evolutionary science, and will engage both scientist and layperson alike. Get Shubin's latest -- and fasten your seatbelts for a wild ride through time. | 0.800406 | 4.069208 |
- 01 Overview
- 02 Research Track Record
- 03 How It Works
- 04 What's in a Name?
TRIUMF’s unique DRAGON (Detector of Recoils And Gammas of Nuclear Reactions) facility is giving astronomers a clearer view of our stardust origins by simulating the rapid nuclear reactions that take place in exploding stars. It is the only facility in the world capable of experimentally measuring many of these astrophysical reactions.
DRAGON is a recoil mass spectrometer, a tool designed to simulate the nuclear reactions in stars and then identify the reaction products, the recoils.
In the Big Bang, the only elements formed were hydrogen, helium and minute quantities of lithium and beryllium. All of the other naturally occurring elements of the Periodic Table, from carbon to gold and uranium were, and are being, created in stars.
The big question is: how? Observational astronomers and astrophysics theorist work to figure-out the nuclear reaction processes in stars by studying stars’ elemental fingerprints. These are the specific ratios of different elements astronomers see produced by exploding stars, such as nova and supernova. However, in many cases, the specific underlying processes that produce the observed elemental fingerprints are still a mystery, unexplained by stellar models.
This is why DRAGON’s experimental results are so important. The high temperature in an exploding star creates a zoo of very short-lived radioactive isotopes not formed in usual stellar burning. The presence of these rare isotopes creates tens of thousands of different possible nuclear reaction pathways, and which path occurs has a huge influence on the elements that will be produced. What’s key to determining these reaction pathways is the probability that one of these rare isotopes will react.
DRAGON precisely measures the reaction rates of these short-lived radioactive isotopes, particularly a fusion reaction called radiative capture. For example, in 2013 images from the Hubble Space Telescope identified fluorine for the first time in the ejecta of a nova explosion. To enable astronomers to make sense of fluorine’s observed presence, DRAGON researchers measured the probability of one of the key fluorine production radiative capture pathways, the fusion of neon-19 (19Ne) with hydrogen, producing sodium-20 (20Na) and a gamma ray.
DRAGON is designed to experimentally pinpoint the rapid nuclear processes and pathways that occur in exploding stars, primarily for elements created in nova explosions. Novas occur in stellar pair systems, often involving a red giant star (a bloated, dying Sun-like star) and a white dwarf, (the dense, hot carbon-rich cinder of such a star in close proximity). The white dwarf gravitationally draws material, primarily hydrogen, from its neighbour onto it surface until this nuclear fuel builds up to tipping point and explodes in a nuclear flare.
TRIUMF is an associate member of the Joint Institute for Nuclear Astrophysics – Center for the Evolution of the Elements (JINA-CEE), a world-leading repository for stellar nuclear reaction information. Thus, DRAGON’s precision astrophysics nuclear reaction data is used by researchers worldwide and integrated into the latest stellar computational codes and models, providing astronomers with new eyes to follow the elemental story of our cosmos’- and us.
02 Research Track Record
DRAGON Research Track Record: Explaining anomalies in the spectra of classical novaeExplaining anomalies in the spectra of classical novae: The optical, ultraviolet and infrared spectra of the debris left over after nova explosions – thermonuclear detonations on the surface of accreting white dwarves in stellar binary systems – contain important fingerprints of the chemical elements synthesized and ejected during these cataclysmic events. However, for some elements, namely argon and calcium, much more than expected seems to be present. This flies in the face of theoretical models of nova explosions which say that nucleosynthesis in novae effectively stops at calcium, with around the same amount of calcium being present after the explosion as before the explosion. The volume of elements from Ar-Ca produced in these scenarios depends sensitively on the strengths of nuclear reactions around that region, in particular proton-induced radiative capture reactions. One of these, p (38K ,γ)39Ca has now been experimentally measured for the first time using TRIUMF’s DRAGON facility, previously impossible because if the short lifetime of 38K, but accessible to the inverse kinematics technique of DRAGON using an intense 38K beam made at ISAC. This makes p (38K,γ)39Ca the highest mass reaction ever measured using this technique with radioactive beams. Direct measurement of astrophysically important resonances in 38K(p,γ)39Ca, G. Christian, G. Lotay, C. Ruiz et al., Physical Review C, Volume 97, Issue 2, id.025802 (2018) rc/abstract/10.1103/PhysRevC.97.025802 Synopsis: Intel on Stellar Element Production from Accelerator Data (APS Physics Editor’s Highlight) https://physics.aps.org/synopsis-for/10.1103/PhysRevC.97.025802 Direct Measurement of the Astrophysical 38K(p,γ)39Ca Reaction and Its Influence on the Production of Nuclides toward the End Point of Nova Nucleosynthesis, G. Lotay, G. Christian, C. Ruiz et al., Physical Review Letters, Volume 116, Issue 13, id.132701 (2016) https://journals.aps.org/prl/abstract/10.1103/PhysRevLett.116.132701
DRAGON Research Track Record: Relating Hubble observations to the inside of a novae explosionRelating Hubble observations to the inside of a novae explosion: Several years ago, fluorine was observed in the spectrum of a nova explosion for the first time by a joint exercise between the Hubble Space Telescope and the Nordic Optical Telescope. This provides a powerful tool to compare astronomical observations with theoretical stellar models, because only one stable isotope of fluorine exists, 19F, and its quantity is extremely sensitive to the nuclear reactions that create and destroy it as well as the temperature & density conditions in the explosion. One such reaction, p (19Ne,γ)20Na, was measured for the first time at the DRAGON facility, using a beam of short-lived 19Ne produced at ISAC. This long sought-after reaction cross section was previously inaccessible to direct measurement. The results reduce the uncertainties resulting from nuclear physics inputs to negligible levels, when comparing theoretical stellar models to the HST observations. Direct Measurement of the Key Ec.m .=456 keV Resonance in the Astrophysical 19Ne(p,γ)20Na Reaction and Its Relevance for Explosive Binary Systems, R, Wilkinson, G. Lotay, A, Lennarz, C. Ruiz, G. Christian et al., Physical Review Letters, Volume 119, Issue 24, id.242701 (2017) https://journals.aps.org/prl/abstract/10.1103/PhysRevLett.119.242701
DRAGON Research Track Record: Understanding gamma-ray emission from nova explosionsUnderstanding gamma-ray emission from nova explosions: One of the first signals to emanate from a nova explosion is an intense burst of X- and gamma rays, long before the peak of the optical brightness is reached. At such a time, the 511 keV gamma-ray line is directly linked to the amount of radioactive 18F synthesized in the explosion. Thus, observing the 511 keV gamma ray intensity in a nova explosion would give astronomers a direct “thermometer” in the heart of the explosion. The problem is that the rates of nuclear reactions that create and destroy 18F in this environment are highly uncertain, including specifically the 18F(p,𝛼)15O and 18F(p,γ)19Ne reactions. Complementary to work on the 18F(p,𝛼)15O reaction performed at TUDA, DRAGON has measured a key resonance in 18F(p,γ)19Ne for the first time, finding it to be much weaker than previously thought, and reducing the uncertainties in the amount of 18F produced in these scenarios. Measurement of Radiative Proton Capture on 18F and Implications for Oxygen-Neon Novae, C. Akers, A.M. Laird, B. R. Fulton, C. Ruiz et al., Physical Review Letters, vol. 110, Issue 26, id. 262502 (2013) https://journals.aps.org/prl/abstract/10.1103/PhysRevLett.110.262502 Measurement of radiative proton capture on 18F and implications for oxygen-neon novae re-examined, C. Akers, A.M. Laird, B. R. Fulton, C. Ruiz et al., Physical Review C, Volume 94, Issue 6, id.065803 (2016) https://journals.aps.org/prc/abstract/10.1103/PhysRevC.94.065803
03 How It Works
Located in the centre of TRIUMF’s ISAC-I experimental hall, DRAGON is a 21-meter-long, semi-circular apparatus divided into three key parts: a “head”; “body”; and “tail”.
The “head” is the target, the site of the star-like nuclear reactions. The long “body” is where fusion products separate from the unreacted beam, and the “tail” is the detector.
DRAGON’s “Head”: The Gas Target and Gamma Ray Detector
This is where DRAGON’s radiative capture nuclear reactions take place. DRAGON’s “brain” is a triangular chamber that can be filled with hydrogen or helium gas, the main fusion fuel in stars. Short-lived radioactive isotope beams produced in ISAC-I, of the varieties and energies similar to those found in exploding stars, are fired at the gas target, resulting in the same nuclear fusion reactions that occur in stars. For example, when an atom from a beam of sodium-21 (21Na) isotopes slams into an atom of hydrogen gas, it fuses to produce magnesium-22 (22Mg) , which emits gamma rays of specific energies.
One of DRAGON’s distinctive features is that this gas target chamber has tiny entrance and exit holes, six and eight millimeters in diameter, for the ISAC beam and recoil products, to pass through. The holes are necessary because otherwise the recoil products would be contaminated with fusion products from the beam isotopes reacting with the window material.
However, this means the gas chamber is also like trying to keep a balloon inflated when it has two holes in it, especially since the rest of DRAGON is at vacuum pressure, a million times lower pressure than in the gas target cell. Left alone, the target gas would leak-out in a fraction of a second. To solve this conundrum, DRAGON’s gas target is surrounded by a sophisticated and powerful pumping system that captures and recirculates the gas that spills out of the holes.
The gas target is also almost completely surrounded by an array of 30 germanium gamma-ray detectors. These detectors record the energy signatures and timing of the gamma rays inherent to each radiative capture reaction.
DRAGON’s “Body”: The Magnetic Dipole and Electric Dipole Separators
A central experimental challenge with DRAGON is that radiative capture reactions have very low probability and occur relatively infrequently. On average, there’s one fusion recoil for every 100 billion incoming isotope atoms.
The recoils created in the gas chamber exit as a tiny fraction of the unreacted beam, which, like a river, continues into DRAGON’s “body”. Thus, DRAGON’s main task is beam suppression – to separate out the short-lived recoils from the unreacted beam particles.
Like panning for gold, DRAGON uses a series of electromagnetic and physical filters to sift-out the recoil gems. This is accomplished in two main steps, first using a magnetic dipole and then an electric dipole as filters, and a series of slits to physically stop unwanted beam particles.
The beam and recoils come out of the gas target in a range of charge states and this mixed overall beam is focused using magnetic quadrupoles and steered into a magnetic dipole chamber.
This is DRAGON’s coarse filter, where the isotopes are separated by how much electrical charge they possess. This can be done because in a magnetic field, particles follow a path based on the ratio of their momentum-to-charge. The greater its charge, the more a particle will curve in a magnetic field. For example, two particles with the same momentum and both with four electrons missing, will follow the same magnetic path. In DRAGON, the researchers know the predicted charge state of their experimental recoil product and set the magnet to direct only this charge state through the magnetic dipole’s 2.5 cm wide exit aperture. As a result, all of the particles with a different charge state slam into the wall of the charge slit box and are filtered out.
The electric dipole is DRAGON’s fine filter separating particles of different masses. The particles exiting the magnetic dipole’s slit all have the same charge and momentum, but critically, the recoils are travelling slower. As with the magnetic dipole separation, DRAGON researchers set the electric dipole to bend and direct only the recoil atoms through a narrow mass exit slit. Thus, only atoms with the predicted mass, charge, and kinetic energy of the desired recoil atoms pass through the slit, and all the others are stopped in the slit box.
The Tail: DRAGON’s Detectors
With the bulk of DRAGON’s separation work accomplished, the cleaned beam of recoil atoms is sent through another nearly identical set of magnetic and electric dipoles. However, this time the objective is to refocus the beam so that the particles are positioned as they were when they left the gas chamber. Thus, when they hit the detectors there’s a spatial correspondence between the detections in the tail, and the gamma rays detected in the head.
DRAGON’s “tail” has three main detectors that can be used individually or in combination to identify the recoils. The Double-Sided Silicon Strip Detector records the number of recoils, their energy, timing, and exactly where they hit the detector. A gas-filled ionization chamber detector and a micro-channel plate detector can also be used to record the number of recoils, their time of impact, but additionally can identify recoils by mass, via measuring their velocity, and atomic number.
Correlated with the final detection of recoils, the timing and energy of the gamma ray detections provides crucial information to separate-out the real events recorded on the recoil detector from background noise, such as the detection of cosmic rays.
04 What's in a Name?
DRAGON is a recoil separator for radiative capture reactions using something called ‘inverse kinematics’. This mouthful of a description makes sense when taken one step at a time, starting at the end.
“Inverse kinematics” refers to the fact that DRAGON mimics stellar fusion reactions by firing short-lived radioactive isotopes at a target of hydrogen or helium gas. Historically, it was the other way around. Before the advent of sophisticated in-flight, rare isotope separators such as ISAC-I, the only way to create fusion reactions was to accelerate hydrogen or helium at a target. Thus, DRAGON reverses (or inverts) this kinematic (motion of objects) process.
DRAGON specializes in measuring a key type of stellar nuclear reaction called radiative capture. This is a nuclear reaction in which an isotope (in DRAGON’s case usually a short-lived exotic one) fuses with a hydrogen or helium nucleus to form a heavier element, which subsequently emits a gamma ray. Thus, it’s a fusion capture reaction followed by a radiative component, the emission of the gamma ray.
Finally, at its core, DRAGON is a recoil separator. The product of a nuclear fusion reaction is a recoil. In DRAGON, the radiative capture recoils are swamped in a river of the unreacted beam isotopes and DRAGON’s is uniquely able to separate these recoils from unreacted beam isotopes.
For more, read TRIUMF scientist Chris Ruiz’s academic review article Recoil separators for radiative capture using radioactive ion beams. | 0.83806 | 4.077726 |
Asteroids and comets that repeatedly smashed into the early Earth covered the planet's surface with molten rock during its earliest days, but still may have left oases of water that could have supported the evolution of life, scientists say.
The new study reveals that during the planet's infancy, the surface of the Earth was a hellish environment, but perhaps not as hellish as often thought, scientists added.
Earth formed about 4.5 billion years ago. The first 500 million years of its life are known as the Hadean Eon. Although this time amounts to more than 10 percent of Earth's history, little is known about it, since few rocks are known that are older than 3.8 billion years old. [How the Earth Formed: A History]
Earth's violent youth
For much of the Hadean, Earth and its sister worlds in the inner solar system were pummeled with an extraordinary number of cosmic impacts.
"It was thought that because of these asteroids and comets flying around colliding with Earth, conditions on early Earth may have been hellish," said lead study author Simone Marchi, a planetary scientist at the Southwest Research Institute in Boulder, Colorado. This imagined hellishness gave the eon its name — Hadean comes from Hades, the lord of the underworld in Greek mythology.
However, in the past dozen years or so, a radically different picture of the Hadean began to emerge. Analysis of minerals trapped within microscopic zircon crystals dating from this eon "suggested there was liquid water on the surface of the Earth back then, clashing with the previous picture that the Hadean was hellish," Marchi said. This could explain why the evidence of the earliest life on Earth appears during the Hadean — maybe the planet was less inhospitable during that eon than previously thought.
Cosmic bombardment history
The exact timing and magnitude of the impacts that smashed Earth during the Hadean are unknown. To get an idea of the effects of this bombardment, Marchi and his colleagues looked at the moon, whose heavily cratered surface helped model the battering that its close neighbor Earth must have experienced back then.
"We also looked at highly siderophile elements (elements that bind tightly to iron), such as gold, delivered to Earth as a result of these early collisions, and the amounts of these elements tells us the total mass accreted by Earth as the result of these collisions," Marchi said. Prior research suggests these impacts probably contributed less than 0.5 percent of the Earth's present-day mass.
The researchers discovered that "the surface of the Earth during the Hadean was heavily affected by very large collisions, by impactors larger than 100 kilometers (60 miles) or so — really, really big impactors," Marchi said. "When Earth has a collision with an object that big, that melts a large volume of the Earth's crust and mantle, covering a large fraction of the surface," Marchi added.
These findings suggest that Earth's surface was buried over and over again by large volumes of molten rock — enough to cover the surface of the Earth several times. This helps explain why so few rocks survive from the Hadean, the researchers said.
However, although these findings might suggest that the Hadean was a hellish eon, the researchers found that "there were time gaps between these large collisions," Marchi said. "Generally speaking, there may have been something on the order of 20 or 30 impactors larger than 200 km (120 miles) across during the 500 million years of the Hadean, so the time between such impactors was relatively long," Marchi said.
Any water vaporized near these impacts "would rain down again," Marchi said, and "there may have been quiet tranquil times between collisions — there could have been liquid water on the surface."
The researchers suggested that life emerging during the Hadean was probably resistant to the high temperatures of the time. Marchi and his colleagues detailed their findings in the July 31 issue of the journal Nature. | 0.850591 | 3.953083 |
This month, Venus shifts from the evening to the morning sky. For the next few days, look for it low in the southwest at dusk. If no buildings or trees block the view, you can still make out Venus in the twilight; it outshines everything in the sky but the Sun and the Moon. Notice how it appears lower on the horizon each night and is soon completely gone.
On Jan. 10, Venus passes between Earth and Sun (“inferior conjunction“), which would normally make it invisible to us. This time, however, Venus passes above the Sun from our perspective, which means the sharp-eyed observers with clear horizons can observe Venus both at dawn and at twilight for a few days around Jan. 10. After this, you can watch Venus emerge in the morning sky, visible in the southeast at dawn.
Venus remains a morning star for almost all of 2014.
Mercury briefly enters the evening sky this month, right as Venus leaves. Look for it low on the horizon during the last half of January. Although not nearly as bright as Venus, it easily outshines the dim stars near it. Thus, any “star” you see in twilight over the point of sunset late this month is probably Mercury.
Jupiter will remain well placed for evening observing all winter and into the spring (as the Earth passed between it and the Sun on Jan. 5). Look for it in the east at dusk and almost overhead later in the evening.
Mars remains in the morning sky. It continues to brighten a bit in the southwest at dawn.
Saturn has reappeared in the pre-dawn sky. Face south-southeast right before sunup to see it.
In January, the Big Dipper is only partly risen at dusk. As the Big Dipper sets, though, Cassiopeia rises. This is a pattern of five stars in a distinct W (or M) shape which lies directly across the North Star from the Big Dipper. Look for Cassiopeia high in the north on fall and winter evenings.
Watch for the Great Square of Pegasus in the west at dusk. Taurus the Bull is high in the south. Look for the Pleiades star cluster above reddish Aldebaran. Dazzling Orion the Hunter takes center stage on winter evenings. Surrounding Orion are the brilliant stars of winter.
Orion’s belt points down to Sirius, the Dog Star, which outshines all other stars we ever see at night. The Little Dog Star, Procyon, rises with Sirius and is level with Orion’s shoulder as they swing towards the south. To the upper left of Orion’s shoulder is Gemini, the Twins, which contains Jupiter this winter.
New: Jan. 1, 5:15 a.m.; Jan. 30, 3:40 p.m.
1st Quarter: Jan. 7, 9:40 p.m.
Full: Jan. 15, 10:53 p.m.
Last Quarter: Jan. 23, 11:21 p.m.
At 5:59 a.m. on Sat., Jan. 4, the Earth is as close to the Sun as it will get this year; this is called perihelion. Keep in mind that Earth’s orbit is so close to being a perfect circle that its perihelion distance is 0.98 AU, where 1 AU (astronomical unit) is defined as the average Earth-Sun distance. This 2% difference is too small to influence our seasons; the tilt of the Earth’s axis toward or away from the Sun dominates this small effect. That’s why it’s so cold right now (even here in Houston!) and so hot in July.
Although the winter solstice is the shortest day, the earliest sunset occurred on about December 2, and the latest sunrise will occur January 10. That’s because the Earth speeds up on its orbit near perihelion. This acceleration shifts sunrise, local noon, and sunset slightly later each day at this time of year. The effect is smaller than that of the Sun taking a low path across the sky, which normally dominates in causing earlier sunsets and later sunrises. But the Sun’s apparent path varies very little near the solstice itself, allowing the secondary effect of the Earth being nearer to the Sun to predominate.
For most people, then, (those who witness sunset but sleep through sunrise), days will seem to lengthen much more than they actually are. Early risers, on the other hand, will find sunrise occurs even later than last month, at least until late January.
The New Moon of Jan. 30 is the second New Moon after the winter solstice. It therefore marks Chinese New Year. On this date, the Year of the Snake ends and the Year of the Horse begins.
Visit the HMNS website to see this month’s Planetarium schedule
On most clear Saturday nights at the George Observatory, you can hear me do live star tours on the observation deck with a green laser pointer. If you’re there, listen for my announcement. We’re also hosting telescope classes on Jan. 11, so if you or someone you know received one over the holidays come by and let us help you set it up! | 0.821138 | 3.489761 |
Plumbing a 90 million-year-old layer cake of sedimentary rock in Colorado, a team of scientists from the University of Wisconsin-Madison and Northwestern University has found evidence confirming a critical theory of how the planets in our solar system behave in their orbits around the sun.
The finding, published Feb. 23, 2017 in the journal Nature, is important because it provides the first hard proof for what scientists call the “chaotic solar system,” a theory proposed in 1989 to account for small variations in the present conditions of the solar system. The variations, playing out over many millions of years, produce big changes in our planet’s climate — changes that can be reflected in the rocks that record Earth’s history.
The discovery promises not only a better understanding of the mechanics of the solar system, but also a more precise measuring stick for geologic time. Moreover, it offers a better understanding of the link between orbital variations and climate change over geologic time scales.
Using evidence from alternating layers of limestone and shale laid down over millions of years in a shallow North American seaway at the time dinosaurs held sway on Earth, the team led by UW-Madison Professor of Geoscience Stephen Meyers and Northwestern University Professor of Earth and Planetary Sciences Brad Sageman discovered the 87 million-year-old signature of a “resonance transition” between Mars and Earth. A resonance transition is the consequence of the “butterfly effect” in chaos theory. It plays on the idea that small changes in the initial conditions of a nonlinear system can have large effects over time.
In the context of the solar system, the phenomenon occurs when two orbiting bodies periodically tug at one another, as occurs when a planet in its track around the sun passes in relative proximity to another planet in its own orbit. These small but regular ticks in a planet’s orbit can exert big changes on the location and orientation of a planet on its axis relative to the sun and, accordingly, change the amount of solar radiation a planet receives over a given area. Where and how much solar radiation a planet gets is a key driver of climate.
“The impact of astronomical cycles on climate can be quite large,” explains Meyers, noting as an example the pacing of Earth’s ice ages, which have been reliably matched to periodic changes in the shape of Earth’s orbit, and the tilt of our planet on its axis. “Astronomical theory permits a very detailed evaluation of past climate events that may provide an analog for future climate.”
To find the signature of a resonance transition, Meyers, Sageman and UW-Madison graduate student Chao Ma, whose dissertation work this comprises, looked to the geologic record in what is known as the Niobrara Formation in Colorado. The formation was laid down layer by layer over tens of millions of years as sediment was deposited on the bottom of a vast seaway known as the Cretaceous Western Interior Seaway. The shallow ocean stretched from what is now the Arctic Ocean to the Gulf of Mexico, separating the eastern and western portions of North America.
“The Niobrara Formation exhibits pronounced rhythmic rock layering due to changes in the relative abundance of clay and calcium carbonate,” notes Meyers, an authority on astrochronology, which utilizes astronomical cycles to measure geologic time. “The source of the clay (laid down as shale) is from weathering of the land surface and the influx of clay to the seaway via rivers. The source of the calcium carbonate (limestone) is the shells of organisms, mostly microscopic, that lived in the water column.”
Meyers explains that while the link between climate change and sedimentation can be complex, the basic idea is simple: “Climate change influences the relative delivery of clay versus calcium carbonate, recording the astronomical signal in the process. For example, imagine a very warm and wet climate state that pumps clay into the seaway via rivers, producing a clay-rich rock or shale, alternating with a drier and cooler climate state which pumps less clay into the seaway and produces a calcium carbonate-rich rock or limestone.”
The new study was supported by grants from the National Science Foundation. It builds on a meticulous stratigraphic record and important astrochronologic studies of the Niobrara Formation, the latter conducted in the dissertation work of Robert Locklair, a former student of Sageman’s at Northwestern.
Dating of the Mars-Earth resonance transition found by Ma, Meyers and Sageman was confirmed by radioisotopic dating, a method for dating the absolute ages of rocks using known rates of radioactive decay of elements in the rocks. In recent years, major advances in the accuracy and precision of radioisotopic dating, devised by UW-Madison geoscience Professor Bradley Singer and others, have been introduced and contribute to the dating of the resonance transition.
The motions of the planets around the sun has been a subject of deep scientific interest since the advent of the heliocentric theory — the idea that Earth and planets revolve around the sun — in the 16th century. From the 18th century, the dominant view of the solar system was that the planets orbited the sun like clockwork, having quasiperiodic and highly predictable orbits. In 1988, however, numerical calculations of the outer planets showed Pluto’s orbit to be “chaotic” and the idea of a chaotic solar system was proposed in 1989 by astronomer Jacques Laskar, now at the Paris Observatory.
Following Laskar’s proposal of a chaotic solar system, scientists have been looking in earnest for definitive evidence that would support the idea, says Meyers.
“Other studies have suggested the presence of chaos based on geologic data,” says Meyers. “But this is the first unambiguous evidence, made possible by the availability of high-quality, radioisotopic dates and the strong astronomical signal preserved in the rocks.”
Chao Ma, Stephen R. Meyers, Bradley B. Sageman. Theory of chaotic orbital variations confirmed by Cretaceous geological evidence. Nature, 2017; 542 (7642): 468 DOI: 10.1038/nature21402 | 0.832578 | 3.887218 |
Active galactic nuclei are the most luminous persistent (non-transient, even if often variable) objects in the Universe. They are bright in the entire electromagnetic spectrum. Blazars are a special class where the jets point nearly to our line of sight. Because of this special geometry and the bulk relativistic motion of the plasma in the jet, their radiation is enhanced by relativistic beaming. The majority of extragalactic objects detected in γ-rays are blazars. However, finding their counterparts in other wavebands could be challenging. Here we present the results of our 5-GHz European VLBI Network (EVN) observation of the radio source J1331+2932, a candidate blazar found while searching for possible γ-ray emission from the stellar binary system DG CVn (Loh et al. 2017). The highest-resolution radio interferometric measurements provide the ultimate tool to confirm the blazar nature of a radio source by imaging compact radio jet structure with Doppler-boosted radio emission, and give the most accurate celestial coordinates as well.
|Journal||Proceedings of Science|
|Publication status||Published - Jan 1 2018|
|Event||14th European VLBI Network Symposium and Users Meeting, EVN 2018 - Granada, Spain|
Duration: Oct 8 2018 → Oct 11 2018
ASJC Scopus subject areas | 0.841436 | 3.621331 |
This month marks the 20th anniversary of the detection of the first planet spotted around a sun-like star. Here are some other wonderful planet extremes out there in our solar system.
Barnard's Star is famous less for the planets it has than for the planets it doesn't have. Let me explain.
The star, the fourth closest to us, has been the subject of a heated back-and-forth in astronomy circles since the 1960s as to whether or not it has planets. The current answer is no. But for at least 10 years, following an official announcement by Peter van de Kamp in 1963, many people believed the answer was a resounding yes, and that Barnard's Star had two gas giants orbiting it. Van de Kamp never gave up on his claims, but Hubble observations showed them to be impossible in the late 1990s.
But here's the thing: Hubble didn't rule out that Barnard's Star could have planets. It ruled out large planets at certain distances from the ancient sun. It's not out of the question that a rocky word or even a Neptune-sized ice giant could be there.
Future exoplanet surveys may answer the question once and for all ... or just spur on more controversy.
We've discovered planets around sun-like stars for 20 years. But we've known of planets outside our solar system for a little longer ... they just happened to be radically different than any kind of solar system we'd conceived of. Like around the remnant of a supernova.
The first exoplanet discovered still holds the record for being the least massive. PSR B1257+12 A is barely bigger than the moon, orbiting the harsh environment of a pulsar. The planets in the system were discovered in 1992 by the tug they gave on their home star.
Pulsars are known as cosmic timekeepers, sometimes called the "most accurate clocks in the universe." But something was making the beat of PSR B1257+12 just a little off. It was determined that the culprits in question were two planets, including this one. A third was later found, and claims to a third were made and subsequently retracted.
While 51 Pegasi b wasn't the first planet discovered, it was the first confirmed planet around a sun-like star. Even so, it was nothing like any planet we knew. This giant world completes a swift orbit of its star every few days. It kicked off the discovery of many "hot Jupiters," gas giants in orbits even tighter than Mercury's.
In 2015, the atmosphere of 51 Pegasi b was characterized in the visible spectrum, another first. Instead of just observing 51 Pegasi b's silhouette as it passes in front of its home star, we can study things like the planet's actual mass or orbital inclination by looking at the visible light it throws off. This may seem like small potatoes compared to how much we know about most of the planets in our own solar system, but when you're talking about an exoplanet that's 50 lightyears away, this is valuable and fresh information.
The name PSR B1620-26b, like many other exoplanets, doesn't quite roll off the tongue. But this is the oldest planet known, at somewhere around 12.7 billion years old. That's just a little younger than the universe itself.
The ancient planet orbits both a pulsar and an ultra-dense white dwarf, itself another supernova remnant. The two stars orbit each other while the gas giant orbits around the gravitational center of those dense dance partners.
It's only 15 light years away. It's small enough to be rocky, though far, far larger than Earth. But don't pack your bags yet: Gliese 876d is a hell-world. Its day is a shade less than an Earth day in length, but its orbit is just a fraction of Mercury's distance from the sun. It is hot, hot, hot. But the 2005 discovery of the planet is important for showing that there are rocky worlds beyond our solar system.
Four comparatively small planets orbit Gliese-581. Two of them may be habitable. Gliese-581c is on the inner edge of the habitable zone, and may have suffered a fate similar to Venus, turning noxious and harsh. The other, Gliese-581d, is on the outer edge. The pair were the first announced exoplanets to be found in the "Goldilocks zone" of their star.
There's a problem with classifying smaller exoplanets: We've seen a number of planets out in the void that are bigger than Earth but smaller than Neptune. But here in our solar system, we have nothing of the sort. That makes it hard to guess what these world's might be like. At what size something is more likely to be a rocky planet like Earth or Mars? At what size do they become more like the ice giants like Uranus and Neptune?
There's little to no debate with Kepler-11f, a confirmed mini-Neptune. Its density hints at a Saturn-like atmosphere with only a small rocky core. It created a class of "gas dwarves" which are unseen in our home solar system.
Kepler-452b is almost definitely the most Earth-like planet found thus far. Its star is the size of the sun, its year is just a shade longer than ours, and it's a little bit bigger than our planet but firmly in the habitable zone of the star. There are only a few problems: It's more than 1,000 light years away, so we'll never get there. And it's 1.5 billion years older than Earth, meaning that its host star may have grown enough to make the planet currently uninhabitable. Long ago, though, this could have been our twin.
1RXS J160929.1−210524 has a very important record: the first directly imaged exoplanet. That is, the picture you see here is not an artist's conception or a graph depicting the dip in light as the planet passes in front of its star. This is an actual image of the planet.
Most exoplanets have to be detected indirectly, such as through radial velocity, or through methods like transit detection, which look for nearly imperceptible dips in light across a planet's surface. It would take incredible optics to find planets by telescope, something that in most cases won't be available until James Webb Space Telescope and giant ground based operations are online. But younger, hotter planets can be detected with the right imagers. That's just what happened to 1RXS J160929.1−210524.
It's more massive than Jupiter and relatively young, owing to why it could be spotted directly in the first place. Only one other orbital object, to that date, had been directly imaged–a likely brown dwarf–so this is the first time we'd seen a planet in all our years of discovering them. The picture was released in 2008. | 0.944048 | 3.562976 |
The first mission to orbit Mercury is nearing its end. Since arriving at the innermost planet in March 2011, the Messenger spacecraft has “rewritten the entire textbook on Mercury and the implications for the formation and evolution of the inner solar system,” says its principal investigator Sean Solomon of Columbia University. The probe was due to run out of fuel at the end of March, which would have initiated its gradual fall to the planet's surface. Recently, however, engineers found a way to squeeze a few more weeks' worth of propellant from its stores of helium, potentially pushing Messenger's demise into mid-April. The reprieve should allow sufficient extended time for measurements of Mercury's surface from within 15 kilometers—closer than ever before. Although the official mission will be over soon, astronomers now have more than 10 terabytes of data to keep them busy unspooling the mysteries of Mercury for years to come.
By the Numbers
Mercury days Messenger has orbited the planet
Earth days Messenger has orbited the planet
Orbits of Mercury completed
Photographs returned to Earth
Total miles traveled
What We've Learned about Mercury
Weird Magnetic Field
In the 1970s Mariner 10's flyby revealed that Mercury has a magnetic field. Yet Messenger's observations showed that, strangely, the field is not centered inside the planet but instead is offset toward its north pole. Theorists have yet to explain what causes the asymmetry.
Messenger settled a long-running debate about whether volcanism is prevalent on Mercury. Previous imagery showed plains that could have resulted either from volcanic activity or from asteroid collisions. New data from Messenger indicated that these areas best match expectations for dried lava flows and that, in fact, volcanic material covers most of the planet's surface.
Surprising Formation History
Before Messenger, researchers thought Mercury had experienced periods of superhigh temperatures—up to 10,000 kelvins—during its early history, perhaps caused by an asteroid impact. Messenger detected surface metals that would have vaporized at such high temperatures, contradicting this theory.
Messenger revealed enigmatic flat and shallow bright spots littering Mercury's surface. Scientists dubbed them “hollows,” which appear to be unique to the planet. Experts' best guess is that these features form when volatile material from the surface is lost to space, perhaps through interactions with the solar wind of particles blown off the sun. | 0.872671 | 3.85086 |
Although the Kepler Space Telescope itself is defunct due to a malfunction that rendered it out of operation some months ago, the mission goes on as scientists churn through massive amounts of data gathered by Kepler, enough to keep them busy for years to come. One of the fruits of Kepler is an exoplanet called Kepler 78b located just 400 light-years away, which apparently is the most Earth-like planet in terms of size and mass discovered thus far. The similarities end here, however. The planet completes a full orbit around its parent star every 8.5 hours compared to Earth’s steady 365-day orbit. This makes Mercury sound like the North Pole in comparison.
Kepler discovers worlds beyond our solar system by studying light. Each time a planet transits between the observational plane Kepler/parent star, a distinct wobble can be measured. Because Kepler 78b has such a short orbital period, scientists were able to gather a whole lot more data than usual, basically collecting enough data to characterize the planet in a few weeks compared to years with other exoplanets.
Each week Kepler 78b circles its star about 20 times, and based on this MIT researchers found the exoplanet is about 1.2 times Earth’s size — making Kepler 78b one of the smallest exoplanets ever measured. The mass was a lot trickier to determine, though. Each planet exerts a gravitational tug on its parent star, and this stellar motion can be detected as a very slight wobble, known as a Doppler shift. Analyzing this effects was daunting to say the least, since the star’s signal was very faint and besides starspots – dark patches on the surface of stars – also interfered with measurements.
By tracking the frequency at which certain starspots appeared and devising a set of clever calculations, the MIT researchers found the star completes a full rotation every 12.5 days and d that the star rotates relatively slowly, at 1.5 meters per second — about the speed of a jog, or a brisk walk.
“The star is moving at the same speed as when we walk to school or go grocery shopping,” notes Roberto Sanchis-Ojeda, an MIT student who was part of the research. “The difference is that this star is 400 light-years away, so imagine how complicated it is to measure such speeds from so far away.”
The most Earth-like exoplanet in terms of size and mass
Knowing the star’s true Dopler Shift, the researchers determined Kepler 78b is 1.7 times more massive than Earth. When considering size as well, this implies that the exoplanet is similar in density to Earth and that it may be primarily made out of iron and rock. So, in many ways, Kepler 78 is pretty similar to Earth, but when considering how close its is to its star, all other similarities end here.
“It’s Earth-like in the sense that it’s about the same size and mass, but of course it’s extremely unlike the Earth in that it’s at least 2,000 degrees hotter,” says team member Josh Winn, an associate professor of physics at MIT and a member of the Kavli Institute for Astrophysics and Space Research. “It’s a step along the way of studying truly Earth-like planets.”
The researchers say they still have a lot to learn about the planet, like its surface and atmospheric composition. Just earlier this month is was reported that a team of NASA scientists made the first cloud map of an exoplanet, Kepler 7b.
Artie Hatzes, a professor of astronomy at the Institute of Thuringer Landessterwarte in Germany, says this is the first Earth-like planet, in terms of mass, size, and composition, that has been fully characterized.
“This is a tricky measurement to make because the star is very active and it has starspots,” says Hatzes, who did not participate in the research. “These create a false Doppler signal often referred to as ‘activity jitter.’ You can use special tricks to disentangle the Doppler wobble due to the planet, and the Doppler velocity variation caused by the spots on the star. If the planet had a much longer orbital period, it would be much more difficult to do so.”
The exoplanet Kepler 78b was characterized in a paper recently published in the journal Nature. | 0.826712 | 3.912561 |
Last fall, a little-known star called KIC 8462852 became our planetary obsession when astronomers said that its erratic flickering could be the result of an alien megastructure. Further observation of Tabby’s Star yielded no signs of aliens, but the sudden dips in luminosity continue to defy explanation. Now, things just got a bit weirder.
Not only did the star’s light output occasionally dip by up to 20 percent, its total stellar flux diminished continuously over the course of four years.
“We spent a long time trying to convince ourselves this wasn’t real. We just weren’t able to.”
For the first 1000 days of Kepler’s campaign, Tabby’s Star decreased in luminosity by approximately 0.34 percent per year. For the next 200 days, the star dimmed more rapidly, its total stellar flux dropping by 2 percent before leveling off. Overall, Tabby’s Star faded roughly 3 percent during the four years that Kepler stared at it—an absolutely enormous, inexplicable amount. The astronomers looked at 500 other stars in the vicinity, and saw nothing else like it.
Earlier this year, Bradley Schaefer of Louisiana State University decided to examine the star in old photographic plates of sky dating back to the 19th century. He found that over the past 100 years, the star’s total light output has diminished by a whopping 19 percent. But shortly after publishing his claims, other astronomers started poking holes in them, saying that the observed dimming was the result of flawed data.
“We realized that in order to settle this, you needed either a long baseline, or high precision data,” Montet, Caltech astronomer said. “Kepler has the latter.” Montet added that the rate of dimming he measured in the Kepler data is about twice what Schaefer found, which “is different, but not necessarily inconsistent.”
“None of the considered phenomena can alone explain the observations.”
Some of the most credible explanations to date include a swarm of cometary fragments, the effect of a distorted star, or the remnants of a shattered planet. Certain things can explain long-term dimming while others can explain short-term flickering, but as Montet put it, “nothing nicely explains everything.”
What’s clear is that we aren’t going to solve this mystery until we get a better look at this star, which is exactly what Tabby Boyajian—the astronomer who first discovered it—is gearing up to do.
Following a successful crowdfunding campaign to secure time at the the Las Cumbres Observatory Global Telescope Network, Boyajian is going to observe her namesake star for a full year, with the hope of catching it in the act of flickering. If that happens, other telescopes around the world will be alerted and swiftly mobilized. We’ll be able to watch the star wink at us across the entire electromagnetic spectrum, and hopefully, decode its message. | 0.85937 | 3.958096 |
Explosive volcanoes may explain mysterious rock formation on Mars
New Delhi : A mysterious rock formation on Mars may have connections to explosive volcanic eruptions that shot jets of hot ash, rock and gas skyward, a study has found.
The findings in the study have been published in the Journal of Geophysical Research: Planets. The results will enable scientists in better understanding the outer shell of Mars and its habitable nature in future.
The mysterious rock formation - Medusae Fossae - was first spotted by NASA's Mariner spacecraft in 1960 at the Mars's equator, with undulating hills and abrupt mesas.
Researchers suggest that the formation was deposited during explosive volcanic eruptions on the red planet more than 3 billion years ago.
"This is a massive deposit, not only on a Martian scale, but also in terms of the solar system, because we do not know of any other deposit that is like this," said Lujendra Ojha, a planetary scientist at Johns Hopkins University in the US.
The Medusae Fossae Formation consists of hills and mounds of sedimentary rock straddling Mars's equator. Sedimentary rock forms when rock dust and debris accumulate on a planet's surface and cement over time.
Scientists have known about the Medusae Fossae for decades, but were unsure whether wind, water, ice or volcanic eruptions deposited rock debris in that location.
But now, after several tests including gravity data, the researchers are now confident that the rock is so porous, it had to have been deposited by explosive volcanic eruptions. | 0.876406 | 3.396107 |
During the afternoon poster session at the Division of Planetary Sciences / European Planetary Science Congress meeting, I had a long talk with Ludmila Zasova (IKI) about Russia's Venera-D mission to Venus. It has been pushed back to 2018, and been scaled back significantly. In its original conception, it had a large orbiter, sub-satellite, two balloons, two small landers, and a large, long-lived lander. While this sounds spectacular, it also sounded dangerously complex for Russia's first mission to Venus since the mid-1980s.
In its new incarnation, the orbiter, of Phobos-Grunt heritage, is still large and will have extensive instrumentation, including an ultraviolet imaging spectrometer. The orbiter's mission will primarily focus on the atmosphere, studying its chemistry, greenhouse properties, and super-rotation. It will use infrared instruments to study surface-atmosphere interactions and look for volcanic activity, but unlike the earlier incarnation of the mission, it will not carry a radar instrument. The sub-satellite for plasma investigations has been retained.
NASA / JPL-Caltech
Ovda Regio, Venus
Parts of Venus are covered with landforms called tesserae that result from a long and complex history of folding, faulting, and volcanic infilling of the Venusian surface.
The balloons and landers have been replaced with a single, large lander which will largely build on the heritage of the Vega landers, which launched in 1985. It will have a maximum surface lifetime of three hours, based on battery life. Unlike the Soviet landers, this one will have a targeted landing. For the early Venera landers, Venus had yet to be mapped, so there was no way to choose a landing site. The Venera-D lander will be targeted to one of the complex, enigmatic tesserae, regions of complex ridges that are unique to Venus. There are many theories as to the origin of tessera terrain, but compositional data from the surface is needed to discriminate among them.
The lander will have extensive instrumentation to study the surface and atmosphere. One of the most exciting things is that it will have a several panoramic cameras and engineering cameras that will take images that show the surface in a more human, complete perspective, than the U-shaped scans taken by Veneras 9,10, 13, and 14, giving us back on Earth a much better feel for what the region is "like". Given the complexity of the terrain they plan to land in, these views should be spectacular. It will, incidentally, carry old-style panoramic cameras as well in order to get some really close-up views of the surface very close to the lander.
While many of you may be disappointed at the scaling back of this mission, I believe it is for the best. Given the funding available, which, while much better than in the 1990s, is still constrained, this is a mission that has a real chance of actually flying. No other space agency has a mission to land on Venus (or build a new orbiter, although Venus Express continues to operate and Akatsuki may eventually enter some sort of orbit around the planet) in planning or development, so this is likely our only chance to make a major advance in Venusian exploration in the coming decade. Best of luck to the Venera-D team!
Poster on Venera-D mission presented at DPS/EPSC 2011 | 0.833976 | 3.911089 |
A lot happened between these two pictures.
On the left is the "first light" of the Kepler Space Telescope. Dated April 8, 2009, it represents NASA's initial image from the planet-hunting telescope. Now, nearly a decade later, the agency has released Kepler's parting gift: its "last light" image, as seen on the right. It was taken on September 25, 2018, just before mission's end.
The pictures themselves don't say much. They represent Kepler's field of view, the parts of the sky it surveyed during a decade of uncovering planets and solar systems far beyond our own. Look closely, though, and you'll see how our world has changed thanks to what we learned about other ones.
The Delta II rocket that left Cape Canaveral in March 2009 to carry Kepler into space departed a planet with a different view of itself. Scientists had confirmed the discovery of the first planets beyond our solar system not too long before, in the early-to-mid 1990s. But the big questions about other worlds had to be answered with a shrug and a hypothesis. Are there other planets like Earth? Is our eight-planet solar system typical, or an outlier? Nobody could say with much certainty.
Anyone hoping for the existence of life beyond Earth didn't have much to go on, either. Before the Kepler mission, most known exoplanets were so-called hot Jupiters—megaworlds so huge and scaldingly close to their stars that any kind of life as we know it would be impossible. But in the years following first light, Kepler found stacks of new worlds—hundreds, and then thousands. To date, the mission has identified more than 5,000 planet candidates, with at least 2,600 of those confirmed to be real.
Time would catch up to Kepler, as it does to us all. In 2013, NASA said two of the telescope's four reaction wheels—effectively high-tech gyroscopes used to stabilize the instrument—had failed. When a third broke, engineers had to make clever and strategic use of fuel while taking advantage of the physical pressure of sunlight to keep the telescope operational, this time in a secondary mission called K2 that searched for larger worlds. In October 2018, the telescope ran out of fuel, beaming back its last light before disappearing into the distance.
Kepler's legacy lives on in its successor, TESS, the Transiting Exoplanet Survey Satellite. Last April, a SpaceX rocket launched that mission to map 85 percent of the sky in the coming years and look for planets similar to ours, ones that could be prime candidates to hunt for extraterrestrial life. TESS could find many times more exoplanets than Kepler ever did.
And yet, there is little buzz about the mission. With so many mind-blowing discoveries from Kepler and other telescopes over the past several years, the interstellar goalposts have moved. Where a few new planets once shook up our picture of our own place in the cosmos, data dumps about hundreds of newfound planets now elicit a yawn.
For now. TESS is up there in a highly elliptical orbit around Earth, beginning to rack up new planet candidates. Someday soon, perhaps it will send down data that will change everything again. | 0.856131 | 3.603461 |
Pics After years of research and testing, NASA has demonstrated spacecraft positioning equipment that relies on measuring X-ray bursts. The hardware will help future spacefarers navigate the galaxy and beyond.
Your car or smartphone GPS gear works out its position using signals received from a constellation of satellites orbiting Earth. The NASA system – dubbed Station Explorer for X-ray Timing and Navigation Technology, or SEXTANT – uses the same sort of approach by analyzing bursts of X-ray emissions from distant pulsars.
"This demonstration is a breakthrough for future deep space exploration," said SEXTANT project manager Jason Mitchell, an aerospace technologist at NASA's Goddard Space Flight Center in Maryland. "As the first to demonstrate x-ray navigation fully autonomously and in real-time in space, we are now leading the way."
For the technology's first test drive, in November last year pulsar signals were picked up by the Neutron-star Interior Composition Explorer (NICER), which is a washing-machine-sized collection of 52 X-ray telescopes and silicon drift detectors installed on the hull of the International Space Station. Pulsars are usually neutron stars, or white dwarfs, hence the neutron star reference.
NICER's mirror assemblies direct signals from distant stars onto X-ray detectors ... Source: NASA
NICER was aimed at four pulsar targets — J0218+4232, B1821-24, J0030+0451, and J0437-4715 – and timed the bursts they emitted down to the millisecond. After just 78 measurements, NASA's SEXTANT software was able decode NICER's readings and accurately determine the position of the ISS from the pulsars' output.
The precision took the space boffins by surprise. The goal was to get a position accurate to within 10 miles, yet the team got it down to three – which may not sound that useful, but when you're talking interstellar distances, that's good enough.
"We're doing very cool science and using the space station as a platform to execute that science, which in turn enables x-ray navigation," said Keith Gendreau, NICER principal investigator, who presented the findings on Thursday this week at the American Astronomical Society meeting in Washington. "The technology will help humanity navigate and explore the galaxy."
The team now wants to build pulsar positioning hardware small enough to be used by any kind of spacecraft. The first trial of said gear will take place later this year. ®
Sponsored: Webcast: Ransomware has gone nuclear | 0.849244 | 3.484302 |
So on the same week that the highly-anticipated film “The Martian” opens in U.S. theaters (you are going to go see it, I assume) NASA revealed the latest discovery regarding the Red Planet: there is water on the surface there, salty rivulets that periodically run down steep slopes in Hale Crater and stain its sands with dark streaks.
It might not be something that Mark Watney would want to guzzle a glassful of, but it is a major finding for planetary scientists!
The news was released to the world on Monday, September 28, during a presser at NASA HQ in Washington DC. (You can see the full video below.) During the hour-long event NASA scientists and dignitaries John Grunsfeld, Jim Green, and Michael Meyer made the public affirmation that the typically drier-than-bone-dry surface of Mars does — at least in some locations — feel the wetness of liquid water to this day. The discovery was made with observations from NASA’s Mars Reconnaissance Orbiter (MRO) and research performed by Georgia Tech grad student Luju Ojha.
To make a long story short (you can read the full press release here) dark streaks that had been previously imaged by the HiRISE camera aboard MRO have been subsequently examined by another instrument aboard the orbiter and found to contain certain forms of salts (perchlorates) that can only be present in liquid water, and that also help keep water liquid at low temperatures.
The dark streaks are known as recurring slope lineae, or RSLs, because they have show up on satellite imagery as dark lines that appear and fade periodically with the Martian seasons, and are found mainly on steep slopes of craters and tall peaks.
RSLs have been observed by HiRISE for years and have long been suspected to be a result of flowing water, but the identification of hydrated perchlorates within them — the first such detection from orbit — is the “dripping water gun” for the presence of liquid water.
So what does this mean for Mars and future human exploration?
For one thing it gives a target for where to look for the possibility of life on the surface of Mars. Here on Earth where there’s water there’s nearly always some sort of life that uses it to survive, and the same may be said for Mars (not to mention elsewhere in the Solar System.) And even if life isn’t crawling around literally on top of Mars, the source of the water — whatever that may prove to be — could be located at a safe enough distance from the harshness of the Martian surface to support life.
“It’s very likely I think that there’s life in the crust of Mars, as microbes,” stated Alfred McEwen, principal investigator for the HiRISE instrument, during Monday’s press conference.
And with the presence of water comes potential resources for future explorers, in the form of drinking and irrigation water (properly desalinated, of course) and the base ingredients for rocket fuel: hydrogen and oxygen.
“Water…may decrease the cost and increase the resilience of human exploration on the Red Planet.”
— Mary Beth Wilhelm, NASA’s Ames Research Facility
Of course these damp, salty streaks in the Martian sand are far from actual streams, rivers, or oceans, but they are our best hints at hidden reservoirs on the Red Planet. | 0.860385 | 3.700011 |
Climbing the Harmonic Mountain
Harmonic Transformation for Megalithic Astronomy
The behaviour of prime numbers is far easier to study than planetary astronomy. Megalithic astronomy was already studying numbers using lengths rather than arithmetic. Division by three, for example, could be done through dividing a number of counters by repeated subtraction of three units to see if there were any left over. The door was also open to the idea of using these lengths as musical strings so as to discover that those interval ratios involving the first three primes gave the ear sounds that seem more harmonious.
This division between music and astronomy reveals a natural duality found within music, since string length forms a musical tone, while the ear is the judge of which tone pairs are harmonious. The notion that a mythical character named Pythagoras invented numerical tuning cannot be true since two thousand years before him Sumerians had a numerical tuning theory. However, it is Pythagoras who kept alive the idea of a Harmony of the Spheres, leading to the many later Theoretical Harmonists.
Knowledge of musical harmony between planetary synodic periods, which entered the historical record in Sumeria by the time of Gilgamesh, was due to the megalithic usage of measure as a pre-arithmetic notation (in which numbers were stored as lengths). The capacity of megalithic astronomers to make the necessary orbital measurements of the Moon (120), Sun, Jupiter (135), and Saturn (128) revealed musical intervals between these bodies. The later megalithic astronomers would then have had a theory of harmony based on the factorization of numbers and the intervals found between them. It was their numerical tuning theory that one finds expressed in the ancient Near Eastern texts, where the strings of harps were given names that were numbers--exact numbers that were the smallest possible integers required to form the required scales--thus populating their octaves with harmonious tone sets.
Limiting the Flood of Numbers
When the lunar measurements found in outer orbital planetary periods were numerically “cleared” of fractions, they could be studied beneath a limiting harmonic number equal to or greater than 135, the highest number in the set. This approach of using limits would prove to be the only clear way of investigating the universe of rational harmony, and the idea of a lunar month equal to 10 units of time was the founding step. Having noted that powers of three and five demarcate the arising of harmonic numbers within the field of all numbers, harmonic numbers can be lined up left to right according to the power of three they contain, and vertically stacked according to their composite power of five. There are less powers of five possible within a given range, with the greatest power of five atop what then becomes a mountain of numbers between a limit and half of that limit, forming an octave populated by tones and, between tones, intervals. In the next chapter, it becomes clearer that this is the best way to look at harmonic numbers within limits, since powers of three are added when tuning an instrument using perfect fifths--that is, when multiplying by 3/2. From this we learn that each unique combination of powers of three and five, within a limit, leads to only one harmonic number in each octave mountain.
When a limiting number is chosen, it should be a harmonic number (called a regular number in the ancient Near East) made up of factors of 2, 3 and 5. As stated, the largest number in our set [120,128,135] is 135 and the only harmonic number greater than this is 150. There is a biblical reference concerning Noah's flood that "The waters prevailed upon the earth a hundred and fifty days" (Genesis 7:24), an example of how the Bible compilers seem to use significant harmonic numbers within their stories, as shall become obvious in later chapters.
The number for Saturn (128) contains no threes or fives and seems to belong to a different category as a number, in which two doubles itself. In this case two is being doubled six times and in each of those doublings the limit rapidly grows: 2:4:8:16:32:64:128. It is only with the last doubling that Saturn as 128 (its synod) can contain the Moon as 120 (the lunar year). Yet 128 cannot contain Jupiter as 135 (its synod), while 150 can hold 135, 128 and 120 within its octave of 75:150. When these three astronomical periods were investigated, as number phenomena based upon a unit one tenth of a lunar month, 150 is the lowest limit in which the Moon, Saturn, and Jupiter can share an octave. This makes 150 a significant and unique number, perhaps signified in the limit of Noah's flood. These could be referring to the step forward in late megalithic understanding that was subsequently transmitted to the Near East and Far East, where lessons in far larger harmonic limits were to follow.
Both 120 and 135 contain a single factor of five, but there are no factors of five in the interval (9/8) between them. Meanwhile, 150 has two fives in its own "make-up" and so one seeks to go beyond the flood limit of 150 days and "come down" to the age at which Isaac dies(180), whereupon one sees that 90:120::135:180 reveals the 120::135 interval as held between an ascending fourth of 4/3 x 90 and a descending fourth of 3/4 x 180. If we divide 90 by 2 then 45 cannot be halved and the biblical Adam, the precursor to Noah and First Man, is A.D.M = 1.4.40, which sums to 45. Abraham's wife Sarah would give birth to Isaac at age 90 and then, as above, Isaac died at 180. The Bible's Genesis story appears to be recapitulating early limits necessary to "contain" the two outer planets and the lunar year. | 0.86048 | 3.721123 |
Surf's Up on Saturn's moon Enceladus. Check out the spewing spray as caught by the Cassini spacecraft:
NASA's Cassini spacecraft has discovered the best evidence yet for a large-scale saltwater reservoir beneath the icy crust of Saturn's moon Enceladus. The data came from the spacecraft's direct analysis of salt-rich ice grains close to the jets ejected from the moon. NASA JPL
From NASA's press release:
"The salt-rich particles have an "ocean-like" composition and indicate that most, if not all, of the expelled ice and water vapor comes from the evaporation of liquid salt water. The findings appear in this week's issue of the journal Nature."
"There currently is no plausible way to produce a steady outflow of salt-rich grains from solid ice across all the tiger stripes other than salt water under Enceladus's icy surface," said Frank Postberg, a Cassini team scientist at the University of Heidelberg, Germany, and the lead author on the paper. When water freezes, the salt is squeezed out, leaving pure water ice behind. If the plumes emanated from ice, they should have very little salt in them."
Water, water everywhere is the rule of the Universe I do believe....we have found it on Mars, our own Moon, comets and perhaps other moons in the solar system.
Sky Guy in VA | 0.820318 | 3.16357 |
Researchers using NASA's Mars Reconnaissance Orbiter (MRO) have found eight sites where thick deposits of ice beneath Mars' surface are exposed in faces of eroding slopes.
These eight scarps, with slopes as steep as 55 degrees, reveal new information about the internal layered structure of previously detected underground ice sheets in Mars' middle latitudes.
The ice was likely deposited as snow long ago. The deposits are exposed in cross section as relatively pure water ice, capped by a layer one to two yards (or meters) thick of ice-cemented rock and dust. They hold clues about Mars' climate history. They also may make frozen water more accessible than previously thought to future robotic or human exploration missions.
Researchers who located and studied the scarp sites with the High Resolution Imaging Science Experiment (HiRISE) camera on MRO reported the findings today in the journal Science. The sites are in both northern and southern hemispheres of Mars, at latitudes from about 55 to 58 degrees, equivalent on Earth to Scotland or the tip of South America.
"There is shallow ground ice under roughly a third of the Martian surface, which records the recent history of Mars," said the study's lead author, Colin Dundas of the U.S. Geological Survey's Astrogeology Science Center in Flagstaff, Arizona. "What we've seen here are cross-sections through the ice that give us a 3-D view with more detail than ever before."
Windows into underground ice
The scarps directly expose bright glimpses into vast underground ice previously detected with spectrometers on NASA's Mars Odyssey orbiter, with ground-penetrating radar instruments on MRO and on the European Space Agency's Mars Express orbiter, and with observations of fresh impact craters that uncover subsurface ice. NASA sent the Phoenix lander to Mars in response to the Odyssey findings; in 2008, the Phoenix mission confirmed and analyzed the buried water ice at 68 degrees north latitude, about one-third of the way to the pole from the northernmost of the eight scarp sites.
The discovery reported today gives us surprising windows where we can see right into these thick underground sheets of ice," said Shane Byrne of the University of Arizona Lunar and Planetary Laboratory, Tucson, a co-author on today's report. "It's like having one of those ant farms where you can see through the glass on the side to learn about what's usually hidden beneath the ground."
Scientists have not determined how these particular scarps initially form. However, once the buried ice becomes exposed to Mars' atmosphere, a scarp likely grows wider and taller as it "retreats," due to sublimation of the ice directly from solid form into water vapor. At some of them, the exposed deposit of water ice is more than 100 yards, or meter, thick. Examination of some of the scarps with MRO's Compact Reconnaissance Imaging Spectrometer for Mars (CRISM) confirmed that the bright material is frozen water. A check of the surface temperature using Odyssey's Thermal Emission Imaging System (THEMIS) camera helped researchers determine they're not seeing just thin frost covering the ground.
Researchers previously used MRO's Shallow Radar (SHARAD) to map extensive underground water-ice sheets in middle latitudes of Mars and estimate that the top of the ice is less than about 10 yards beneath the ground surface. How much less? The radar method did not have sufficient resolution to say. The new ice-scarp studies confirm indications from fresh-crater and neutron-spectrometer observations that a layer rich in water ice begins within just one or two yards of the surface in some areas.
Astronauts' access to Martian water
The new study not only suggests that underground water ice lies under a thin covering over wide areas, it also identifies eight sites where ice is directly accessible, at latitudes with less hostile conditions than at Mars' polar ice caps. "Astronauts could essentially just go there with a bucket and a shovel and get all the water they need," Byrne said.
The exposed ice has scientific value apart from its potential resource value because it preserves evidence about long-term patterns in Mars' climate. The tilt of Mars' axis of rotation varies much more than Earth's, over rhythms of millions of years. Today the two planets' tilts are about the same. When Mars tilts more, climate conditions may favor buildup of middle-latitude ice. Dundas and co-authors say that banding and color variations apparent in some of the scarps suggest layers "possibly deposited with changes in the proportion of ice and dust under varying climate conditions."
This research benefited from coordinated use of multiple instruments on Mars orbiters, plus the longevities at Mars now exceeding 11 years for MRO and 16 years for Odyssey. Orbital observations will continue, but future missions to the surface could seek additional information.
"If you had a mission at one of these sites, sampling the layers going down the scarp, you could get a detailed climate history of Mars," suggested MRO Deputy Project Scientist Leslie Tamppari of NASA's Jet Propulsion Laboratory, Pasadena, California. "It's part of the whole story of what happens to water on Mars over time: Where does it go? When does ice accumulate? When does it recede?"
The University of Arizona operates HiRISE, which was built by Ball Aerospace & Technologies Corp., Boulder, Colorado. The Johns Hopkins University Applied Physics Laboratory, Laurel, Maryland, leads MRO's CRISM investigation. The Italian Space Agency provided MRO's SHARAD instrument, Sapienza University of Rome leads SHARAD operations, and the Planetary Science Institute, based in Tucson, Arizona, leads U.S. involvement in SHARAD. Arizona State University, Tempe, leads the Odyssey mission's THEMIS investigation. JPL, a division of Caltech in Pasadena, California, manages the MRO and Odyssey projects for the NASA Science Mission Directorate in Washington. Lockheed Martin Space, Denver, built both orbiters and supports their operation.
News Media Contact
Jet Propulsion Laboratory, Pasadena, Calif.
U.S. Geological Survey, Denver
Laurie Cantillo / Dwayne Brown
NASA Headquarters, Washington
202-358-1077 / 202-358-1726
[email protected] / [email protected] | 0.839157 | 3.924112 |
While astronomers are trying to figure out which planets they find are habitable, there are a range of things to consider. How close are they to their parent star? What are their atmospheres made of? And once those answers are figured out, here’s something else to wonder about: how many minerals are on the planet’s surface?
In a talk today, the Carnegie Institution of Washington’s Robert Hazen outlined his findings showing that two-thirds of minerals on Earth could have arisen from life itself. The concept is not new—he and his team first published on that in 2008—but his findings came before the plethora of exoplanets discovered by the Kepler space telescope.
As more information is learned about these distant worlds, it will be interesting to see if it’s possible to apply his findings—if we could detect the minerals from afar in the first place.
“We live on a planet of remarkable beauty, and when you look at it from the proximity of our moon, you see what is obviously a very dynamic planet,” Hazen told delegates at “Habitable Worlds Across Time and Space”, a spring symposium from the Space Telescope Science Institute that is being webcast this week (April 28-May 1).
His point was that planets don’t necessarily start out that way, but he said in his talk that he’d invite comments and questions on his work for alternative processes. His team believes that minerals and life co-evolved: life became more complex and the number of minerals increased over time.
The first mineral in the cosmos was likely diamonds, which were formed in supernovas. These star explosions are where the heavier elements in our cosmos were created, making the universe more rich than its initial soup of hydrogen and helium.
There are in fact 10 elements that were key in the Earth’s formation, Hazen said, as well as that of other planets in our solar system (which also means that presumably these would apply to exoplanets). These were carbon, nitrogen, oxygen, magnesium, silicon, carbon, titanium, iron and nitrogen,which formed about a dozen minerals on the early Earth.
Here’s the thing, though. Today there are more than 4,900 minerals on Earth that are formed from 72 essential elements. Quite a change.
Hazen’s group proposes 10 stages of evolution:
- Primary chondrite minerals (4.56 billion years ago) – what was around as the solar nebula that formed our solar system cooled. 60 mineral species at this time.
- Planetesimals—or protoplanets—changed by impacts (4.56 BYA to 4.55 BYA). Here is where feldspars, micas, clays and quartz arose. 250 mineral species.
- Planet formation (4.55 BYA to 3.5 BYA). On a “dry” planet like Mercury, evolution stopped at about 300 mineral species, while “wetter” planets like Mars would have seen about 420 mineral species that includes hydroxides and clays produced from processes such as volcanism and ices.
- Granite formation (more than 3.5 BYA). 1,000 mineral species including beryl and tantalite.
- Plate tectonics (more than 3 BYA). 1,500 mineral species. Increases produced from changes such as new types of volcanism and high-pressure metamorphic changes inside the Earth.
These stages above are about as far as you would get on a planet without life, Hazen said. As for the remaining stages on Earth, here they are:
- Anoxic biosphere (4 to 2.5 BYA), again with about 1,500 mineral species existing in the early atmosphere. Here was the rise of chemolithoautotrophs, or life that obtains energy from oxidizing inorganic compounds.
- Paleoproterozoic oxidation (2.5 to 1.5 BYA)—a huge rise in mineral species to 4,500 as oxygen becomes a dominant player in the atmosphere. “We’re trying to understand if this is really true for every other planet, or if there is alternative pathways,” Hazen said.
It should be noted here that oxygen does not necessarily indicate there is complex life. Fellow speaker David Catling from the University of Washington, however, noted that oxygen rose in the atmosphere about 2.4 billion years ago, coincident with the emergence of complex life.
Animals as we understand them could have been “impossible for most of Earth’s history because they couldn’t breathe,” he noted. But more study will be needed on this point. After all, we’ve only found life on one planet: Earth.
Note : The above story is based on materials provided by Universe Today | 0.879457 | 3.898875 |
Artistic vision of a quasar
Using ATLAS and WISE, scientists were able to find two new bright quasars with a high redshift. The objects were named VST-ATLAS J158.6938-14.4211 and VST-ATLAS J332.8017-32.1036. With their help, we can improve our understanding of universal evolution.
Quasars with high redshift (more than 6.0) are especially interesting to astronomers, since their UV light is absorbed by neutral hydrogen in direct visibility. As a result, they can be used to probe the intergalactic medium in early space. These are the brightest and most distant compact objects in the Universe.
The spectrum of quasars with a high redshift level can be used to determine the massiveness of a supermassive black hole, which limits the evolution and model of quasar formation. Therefore, such objects can serve as powerful tools for studying the early Universe. However, these types of quasars are difficult to find using ordinary color selections. It's all about their low spatial density and high levels of pollution from cool dwarfs. Among the 300,000 quasars found at this stage, only 290 have redshifts above 5.0.
Recently, scientists from the University of Durham (UK) found two new high-redshift quasars using ATLAS and WISE. Further spectroscopic observations confirmed the phenomena.
For VST-ATLAS J158.6938-14.4211, the redshift reaches 6.07, and for VST-ATLAS J332.8017-32.1036 - 6.32. Their values are 19.4 and 19.7, respectively. The researchers also managed to conduct a preliminary assessment of the mass of black holes that feed the quasars. In J158-14, the black hole's mass is 1.8 billion solar, and in J332-32 it is 2 billion times more than the solar one. | 0.819792 | 3.56183 |
Tidal effects should follow from the inertial free fall of each galaxy in the accelerating expansion of the Universe. So we show that growing rotation of galaxies is due to tidal acceleration, and causes the apparent need for dark matter, in the same way that the inertial free fall condition of all galaxies causes the apparent need for dark energy.
As seen in the main article, the accelerating expansion of the Universe may be understood as the combined effect of the inertial free falls of all galaxies. For an observer in any galaxy, his/her reverse acceleration from all the rest of the Universe causes the global redshift of other galaxies’ light, and the rising of an “Aurora Mirror” from his/her cosmic background, or horizon, in such a way that nothing can differentiate, in physical terms, his/her condition from what we know and understand as free fall.
Like any free fall, this one should cause tidal effects. But the net acceleration of each galaxy is relative to all the points of its spherical horizon (or background), so that tide does not have a privileged direction, but it emerges like a growing rotation involving each galaxy, while Universe’s age (and entropy) increases. This growing tidal rotation causes the apparent need for dark matter, in the same way that the inertial free fall condition of every galaxy causes the apparent need for dark energy.
In this article we show why inertial tide results in a growing rotation of each galaxy, with three examples involving three ideal and approximate scales, going from high heterogeneity to high homogeneity, and two other considerations. Before you continue, we simply point out that this growing rotation, as seen in the main article, implies increasing local space rotation, in order to balance the increasing inertia added to the respective local scale system.
Supercluster level: “Earth and Moon” example. The Moon is orbiting around the Earth less rapidly than how quickly Earth is spinning, so Earth’s rotation keeps the position of tidal bulge of the oceans (and its mass) ahead of the position directly under the Moon. If we take the Moon away, distancing it from the Earth, the inertia of the bulge, whilst its level falls, gives more angular momentum to the Earth spin, making the day get shorter. So if we give a component of radial acceleration to our satellite, some angular momentum is transferred from the previous orbital motion of the Moon to the present rotation of the Earth. This due to the irregularity of Earth’s surface and to the liquid (non-rigid) nature of this irregularity (the oceanic bulging). The same goes for single galaxies and clusters: it is the non-rigid irregularity of their mass distribution to make their angular momentum grow while all the other clusters gain a net component of radial acceleration. If orbits in a cluster get higher angular momentum, much of this, through tidal effects, will be transferred to single galaxies in the course of time.
Filament level: “an imaginary Jupiter with its satellites” example. Let’s imagine a situation similar to the previous one, this way an extrasolar Jupiter with many of its satellites in a momentary alignment: if we give a radial acceleration to this group of bodies, taking them away from the planet, we transfer some of their orbital angular momentum to the main body, which is a gas giant (whereas any supercluster is very much more irregular, and then more subjected to tidal accelerations). Our conclusion does not change if there are a few other satellites, which are revolving out of that line. If they are not evenly spaced, their inverse radial acceleration makes a contribution to the angular momentum of the giant planet. All those influences transform tidal effects in tidal accelerations: they are little but continuous in Universe’s time. One important difference, to be remarked, is that from this level up, a few outer “satellites” – to stay in our example – begin to show retrograde direction orbits: this does not decrease but enhances the remote influence of their net radial acceleration.
Indeed superclusters have different directions of space rotation to the extent that they are set around any of several cosmic voids; so well-known voids are like amphidromic points or tidal nodes of an ocean, i.e. regions wherein spins of the space fabric are almost neutralizing each other.
The Universe is keeping relatively high spin and irregular regions (superclusters, linked by filaments) around relatively low spin but regular ones (cosmic voids). So entropy has a slightly different meaning from the ordinary one in the logic of the Cosmos, and this is very important with regard to large structure formation and keeping up. Space rotation factor is storing a considerable part of ever increasing entropy into those expanding, regular and almost empty dump-sites; while a further part is to be stored in tidal-accelerating spins of galaxies and clusters, with the consequence of preserving low scale heterogeneity.
Global level: “the galaxy in a glass bowl” example. Let’s imagine a single galaxy in a very large glass bowl. We might see accelerating expansion as the continuous growing of the glass bowl, but we might say the same thing by presuming the glass bowl as unchanged, while seeing the galaxy becoming progressively smaller and smaller. Since this involves a progressive reduction of its moment of inertia, its angular velocity, or spin, must increase (like an ice skater who withdraws her arms).
Our consideration is not so arbitrary. The glass of the bowl is not the boundary of its universe, for the lonely galaxy. Since the bowl is not spinning, that glass is the ideal line where space rotation, involving galaxy’s spin, ends, because from that line forward counter-spin or reverse spin prevails (global spin of the Universe is to be zero, so our imaginary galaxy has to be encircled, from a certain point forward, by a counter-rotating zone). We could say that the bowl represents the unfolding over a spherical surface of a tidal node (from a random cosmic void – the hemispheric asymmetry we see in CMB or “Aurora Mirror” could be explained following the same principle: we cannot look at the entire background, i.e. at the whole “sky”, as if it all might ever rotate in one single direction). Global accelerating expansion distances that ideal surface, or line, so, with respect to its space-rotating region, our galaxy (which following our example is the only massive object in its zone, hence the only object wherein inertia exists) gets a relatively minor momentum of inertia.
The consequence: large scale homogeneity in galaxies distribution is the condition that keeps to its minimum the average moment of inertia of each of them, at a given era. As seen by an observer in a galaxy, at a given era, it is also the condition that preserves to its minimum his/her galaxy combination of radial acceleration and angular momentum, i.e. the mix of proper inertia and local space tide: in fact, any other distribution would be more dissipative, and global motions would be in the direction of removing any global heterogeneity (and of increasing, in the same time, the local one).
The real observer. For an observer in inertial free fall together with his/her galaxy, attributing the global redshift to the remote inertial mass or to the relative reverse acceleration (or proper inertia) is, for the equivalence principle, to say two identical things. So dark energy and far (non-local) dark matter seem to be what we simply name remote inertia. By measuring it, that observer, if in free fall, is measuring his/her own entire proper inertia.
The speed of any observer, relative to his/her deep background (or horizon), cannot exceed the speed of light. Any further acceleration must result in a growing relativistic mass (or proper inertia). However his/her galaxy space-spin has grown up, during Universe’s life, owing to tidal acceleration: i.e. remote inertia has been added to his/her local system, so that much of its proper inertia has been counterbalanced. Therefore any level local space tide is the complex and aggregate process that lead to minimize, at every era, both relativistic proper inertia, and relativistic remote inertia (since global net space-spin is to have the opposite direction than any local level net one). Some galaxy within a cluster may experiment low spin, but only because staying in a (relative) tidal node, whereas remote inertia is added by other galaxies, more accelerated, in its neighbourhood.
Rotational tide adds relative remote inertia, which is what we until now have named dark matter, with space spinning. For an observer who, this time, in order to see the redshift (the part due to the common space rotation) of an outer star in his/her galaxy, lets the near space go beyond him/herself, keeping him/herself backward, and then counter-accelerated (see my article Einstein is asked about dark matter), well we should say the same as before: attributing the measured redshift to the remote inertial mass of the star, or to his/her relative inverse acceleration (or proper inertia) is saying two identical things. But now he/she has changed his/her condition of free fall! Indeed, real observer’s need to change own condition from free fall to weight/like acceleration, in order to measure redshift, explains why Lambda/CDM model names either energy or matter its dark components, since the former implies a radial acceleration, as net component of local systems real trajectories, while the latter causes the spinning of local space, equivalent to a tidal acceleration (or gradient-balancing acceleration). Tide causes the relative lack of relativistic mass we have seen above: without this lack, due to space spins, our Universe would not have had any discrete structure (and any observer). Any scale discrete structures cause local gradients: so the phenomenon we describe is circular, and, as expected, needed gradient is no other than needed local heterogeneity. Therefore, it’s easy to think that mass and spin were born together.
The emergent property of the equivalence principle (see my “Einstein etc.”) is the real factory or forge of the Universe, leading both to the anytime observation of the cosmological principle, and to the anytime evolution of its discrete structures. Our entire argument is based on this eye-opening consideration: relative inertial mass is increasingly greater than gravitational one, but this is precisely what is enabling the equivalence principle, by its necessary emergence, to dynamically structure all we see in the sky.
Mass and space were born together: we have known for centuries the main features of space, “extension” (Descartes), and “dimensionality” (Newton); for one century the third one, “curvature” (Einstein); now we could have known the fourth, “spin”. So probably, the emergence of space spins is also the better explanation of the topic “flatness of space”, that is, the true reason why we do not succeed in measuring scale curvature outside (or above) space-comoving systems like the galactic one.
Besides the consideration of space/rotating systems and of the emergent property of the equivalence principle, a third main aspect characterizes our extension of General Relativity to a revisited role of inertia. In fact EGR does not foresee any gravitational singularity, or event horizon, given that a correlated space precession is combined with extreme curvatures of space-time. This feature could be predictive, since we are close to see for the first time the almost uniform radio emissions of Sagittarius A*, the centre of our galaxy, which is going to appear both a still supermassive monster and a very very dark winking superstar! Till now, VLBI technology has revealed that “its emission region is so small that the source may actually have to point directly at the direction of the Earth”: apart from the lack of blueshift effect related to that radio jet/bullet fired at us, everyone may value the probability of the phenomenon; see also the wonderful images: Lifting the veil on the black hole at the heart of our Galaxy“.
So this feature will be the subject of the next article. | 0.802179 | 4.070481 |
There are currently two enormous ‘bubbles’ of radiation expanding from the center of our galaxy. These are something we have never experienced in general and so scientists are baffled.
This part of our galaxy is something very full of mystery but things like this are completely mind-blowing. According to Business Insider scientists caught their first look at these bubbles back in the 1980s but were unable to see them since. If it were not for the newer MeerKAT telescope in South Africa, we would still be unable to see them or properly research them. While we do not know what caused them, in time we hope to better understand.
This supermassive black hole we have at the end of our galaxy basically seems to have gone into some kind of feeding frenzy several millions of years ago and through that time-period it swallowed up big lumps of gas and matter. From there this ‘burp’ of sorts came to be and written about in a somewhat recent study that was published in the journal Nature.
The Galactic Centre contains a supermassive black hole with a mass of four million Suns1 within an environment that differs markedly from that of the Galactic disk. Although the black hole is essentially quiescent in the broader context of active galactic nuclei, X-ray observations have provided evidence for energetic outbursts from its surroundings2. Also, although the levels of star formation in the Galactic Centre have been approximately constant over the past few hundred million years, there is evidence of increased short-duration bursts3, strongly influenced by the interaction of the black hole with the enhanced gas density present within the ring-like central molecular zone4 at Galactic longitude |l| < 0.7 degrees and latitude |b| < 0.2 degrees. The inner 200-parsec region is characterized by large amounts of warm molecular gas5, a high cosmic-ray ionization rate6, unusual gas chemistry, enhanced synchrotron emission7,8, and a multitude of radio-emitting magnetized filaments9, the origin of which has not been established. Here we report radio imaging that reveals a bipolar bubble structure, with an overall span of 1 degree by 3 degrees (140 parsecs × 430 parsecs), extending above and below the Galactic plane and apparently associated with the Galactic Centre. The structure is edge-brightened and bounded, with symmetry implying creation by an energetic event in the Galactic Centre. We estimate the age of the bubbles to be a few million years, with a total energy of 7 × 1052 ergs. We postulate that the progenitor event was a major contributor to the increased cosmic-ray density in the Galactic Centre, and is in turn the principal source of the relativistic particles required to power the synchrotron emission of the radio filaments within and in the vicinity of the bubble cavities.
For decades, we had no idea if these bubbles were still out there or where they were if so. While these bubbles are smaller and not as intense as the Fermi bubbles we’ve heard about in somewhat recent times, they are both different in their own ways. This kind of thing is quite interesting and the more that you look into it the more fascinating it becomes.
The bubbles are an unusual outburst for our galaxy’s black hole — compared to other galaxies’ central black holes, ours is comparatively inactive, according to research published Wednesday in the journal Nature.
As such, the University of Oxford and Rhodes University astronomers behind the new survey suspect the bubbles are akin to cosmic indigestion — the black hole likely had a feeding frenzy when clumps of cosmic dust passed nearby millions of years ago, just to spew it all back out in the form of the giant bubbles.
How do you feel about all of this? I for one am excited to see what we can uncover in regards. Could this be something much bigger than we assume? | 0.847954 | 3.748622 |
Astronomers have discovered a gigantic planet orbiting a puny star some 30 light-years away. And according to current theories, the planet shouldn’t exist. Dubbed GJ 3512 b, the gas giant is at least half the mass of Jupiter. But it orbits a red dwarf star that’s just one-tenth the mass of our Sun.
“Around such stars there should only be planets the size of the Earth or somewhat more massive Super-Earths,” said Christoph Mordasini of the University of Bern in a press release. “GJ 3512 b, however, is … at least one order of magnitude more massive than the planets predicted by theoretical models for such small stars.”
Bringing the universe to your door. We’re excited to announce Astronomy magazine’s new Space and Beyond subscription box — each one offers a hand-picked astronomy collection and a cosmic adventure. Learn More >>
Scientists thought that gas giants like Jupiter always started their lives by developing heavy, solid cores before quickly accumulating thick, gassy atmospheres. That’s what current models predict. But because of this new planet’s unusual heft compared to its host star, the new research suggests that’s not always the case.
GJ 3512 and its Planet(s)
The discovery is important because red dwarfs are thought to be the most common stars in the universe, accounting for roughly 75 percent of all stars. And typically, red dwarfs only have a few petite planets. This is because small stars shouldn’t have enough extra material left over from their formation to build large planets.
The planets found around red dwarfs typically range from about the mass of Earth to roughly the mass of Neptune. But they almost never approach the mass of Jupiter, like GJ 3512 b does. (For reference, Jupiter is about 300 times the mass of Earth and 20 times the mass of Neptune.)
Because GJ 3512 b is such a big fish in a little pond, the researchers say its host star shouldn’t have had enough material to form the gas giant in the first place — at least according to current models. So, simply the existence of GJ 3512 b is making researchers reconsider whether gas giant planets really must start their lives as nascent embryos of heavy particles before gobbling up copious amounts of gas (a process called core accretion).
“One way out would be a very massive disk that has the necessary building blocks in sufficient quantity,” said planet-formation expert Hubert Klahr from the Max Planck Institute for Astronomy (MPIA) in a press release.
The basic idea is that if the star GJ 3512 initially started its life surrounded by a particularly massive disk of both gas and dust, the gravity of the disk itself would be strong enough to trigger instabilities within it. Some regions of the disk would then directly collapse, ultimately forming large planets without undergoing the typical two-stage growth process.
This is called the gravitational disk collapse model, and so far, it’s been largely ignored when it comes to planets around red dwarfs. The major issue with this scenario is that researchers haven’t yet found examples of such oversized disks around young red dwarf stars.
But according to the study, the gravitational collapse scenario is the most logical way a planet as large as GJ 3512 b could have formed around a star so small.
And the case for gravitational collapse is made even more compelling by the fact that the astronomers also found evidence for a second large planet much farther out in the system — as well as hints that a third massive planet might have been ejected from the system long ago.
“With GJ 3512 b, we now have an extraordinary candidate for a planet that could have emerged from the instability of a disk around a star with very little mass,” said Klahr. “This find prompts us to review our models.”
The new research was published Thursday in Science. | 0.835756 | 3.838084 |
Like a ship cruising the seas or a fighter jet going supersonic, astronomic objects also make shock waves through the medium in which they travel. According to a video released by NASA, studying these interactions, called bow shocks, provides scientists with valuable information about the phenomena they see through their telescopes.
Bow shocks form as particles pile up in front of an object moving through them, the video explains. These could be water molecules in front of a boat, dust in front of a star, or ions in front of a magnetic field. The particles heat up as they compress, forming teardrop-shaped shock waves with the tail pointing downstream.
"Studying stellar bow shocks can reveal the secret motions of the underlying stars, telling us how fast they're moving, which way, and what they're moving through," the video explains. Likewise, investigating the Earth’s magnetic bow shock can help scientists better understand the solar wind.
Along with explaining this physical phenomenon, the NASA video includes gorgeous images of the cosmic shock waves. | 0.8239 | 3.135468 |
Solar System Sun
Terrestrial Planet Mercury, Venus, Earth (Moon), Mars
Asteroid Belt Ceres, Vesta
Jovian Planet Jupiter, Saturn, Uranus, Neptune
Kuiper Belt Pluto, Haumea, Makemake
Scattered Disc Eris, Sedna, Planet X
Oort Cloud Etc. Scholz’s Star
Small Body Comet, Centaur, Asteroid
These are organized by a classification scheme developed exclusively for Cosma. More…
Brown dwarf is a substellar object that occupies the mass range between the heaviest gas giant planets and the lightest stars, having masses between approximately 13 to 75–80 times that of Jupiter (MJ), or approximately 2.5×1028 kg to about 1.5×1029 kg. Below this range are the sub-brown dwarfs, and above it are the lightest red dwarfs (M9 V). Brown dwarfs may be fully convective, with no layers or chemical differentiation by depth.
Unlike the stars in the main sequence, brown dwarfs are not massive enough to sustain nuclear fusion of ordinary hydrogen (1H) to helium in their cores. They are, however, thought to fuse deuterium (2H) and to fuse lithium (7Li) if their mass is above a debated threshold of 13 MJ and 65 MJ, respectively. It is also debated whether brown dwarfs would be better defined by their formation processes rather than by their supposed nuclear fusion reactions.
Stars are categorized by spectral class, with brown dwarfs designated as types M, L, T, and Y.[ Despite their name, brown dwarfs are of different colors. Many brown dwarfs would likely appear magenta to the human eye, or possibly orange/red. Brown dwarfs are not very luminous at visible wavelengths.
There are planets known to orbit brown dwarfs: 2M1207b, MOA-2007-BLG-192Lb, and 2MASS J044144b.
At a distance of about 6.5 light years, the nearest known brown dwarf is Luhman 16, a binary system of brown dwarfs discovered in 2013. HR 2562 b is listed as the most-massive known exoplanet (as of December 2017) in NASA’s exoplanet archive, despite having a mass (30±15 MJ) more than twice the 13-Jupiter-mass cutoff between planets and brown dwarfs. — Wikipedia
Phys.org - latest science and technology news stories Phys.org internet news portal provides the latest news on science including: Physics, Nanotechnology, Life Sciences, Space Science, Earth Science, Environment, Health and Medicine.
Citizen scientists spot closest young brown dwarf...
on June 2, 2020 at 7:00 pm
Brown dwarfs are the middle child of astronomy, too big to be a planet yet not big enough to be a star. Like their stellar siblings, these objects form from the gravitational collapse of gas and dust. But rather than condensing into a star's fiery hot nuclear core, brown dwarfs find a more zen-like equilibrium, somehow reaching a stable, milder state compared to fusion-powered stars.
Astronomers create cloud atlas for hot,...
on May 26, 2020 at 5:21 pm
Giant planets in our solar system and circling other stars have exotic clouds unlike anything on Earth, and the gas giants orbiting close to their stars—so-called hot Jupiters—boast the most extreme.
Astronomers find Jupiter-like cloud bands on...
on May 5, 2020 at 5:34 pm
A team of astronomers has discovered that the closest known brown dwarf, Luhman 16A, shows signs of cloud bands similar to those seen on Jupiter and Saturn. This is the first time scientists have used the technique of polarimetry to determine the properties of atmospheric clouds outside of the solar system, or exoclouds.
NASA's Webb Telescope to unravel riddles of a...
on April 30, 2020 at 4:40 pm
A bustling stellar nursery in the picturesque Orion Nebula will be a subject of study for NASA's James Webb Space Telescope, scheduled to launch in 2021. A team led by Mark McCaughrean, the Webb Interdisciplinary Scientist for Star Formation, will survey an inner region of the nebula called the Trapezium Cluster. This cluster is home to a thousand or so young stars, all crammed into a space only 4 light-years across—about the distance from our Sun to Alpha Centauri.
10 years after BP spill: Oil drilled deeper;...
on April 18, 2020 at 8:27 pm
Ten years after an oil rig explosion killed 11 workers and unleashed an environmental nightmare in the Gulf of Mexico, companies are drilling into deeper and deeper waters, where the payoffs can be huge but the risks are greater than ever. | 0.938978 | 3.529971 |
This is an artist's concept of Saturn's rings and major icy moons.
Saturn's rings make up an enormous, complex structure. From edge-to-edge, the ring system would not even fit in the distance between Earth and the Moon. The seven main rings are labeled in the order in which they were discovered. From the planet outward, they are D, C, B, A, F, G and E.
The D ring is very faint and closest to Saturn. The main rings are A, B and C. The outermost ring, easily seen with Earth-based telescopes, is the A ring. The Cassini Division is the largest gap in the rings and separates the B ring from the A ring. Just outside the A ring is the narrow F ring, shepherded by tiny moons, Pandora and Prometheus. Beyond that are two much fainter rings named G and E. Saturn's diffuse E ring is the largest planetary ring in our solar system, extending from Mimas' orbit to Titan's orbit, about 1 million kilometers (621,370 miles).
The particles in Saturn's rings are composed primarily of water ice and range in size from microns to tens of meters. The rings show a tremendous amount of structure on all scales; some of this structure is related to gravitational interactions with Saturn's many moons, but much of it remains unexplained. One moonlet, Pan, actually orbits inside the A ring in a 330-kilometer-wide (200-mile) gap called the Encke Gap. The main rings (A, B and C) are less than 100 meters (300 feet) thick in most places, compared to their radial extent of 62,120 kilometers (38,600 miles). The main rings are much younger than the age of the solar system, perhaps only a few hundred million years old. They may have formed from the breakup of one of Saturn's moons or from a comet or meteor that was torn apart by Saturn's gravity.
The Cassini-Huygens mission is a cooperative project of NASA, the European Space Agency and the Italian Space Agency. The Jet Propulsion Laboratory, a division of the California Institute of Technology in Pasadena, manages the mission for NASA's Science Mission Directorate, Washington, D.C. The Cassini orbiter was designed, developed and assembled at JPL.
For more information about the Cassini-Huygens mission visit http://www.nasa.gov/cassini
and http://saturn.jpl.nasa.gov . | 0.89241 | 3.712555 |
June 6, 2017 – Boosted by natural magnifying lenses in space, NASA’s Hubble Space Telescope has captured unique close-up views of the universe’s brightest infrared galaxies, which are as much as 10,000 times more luminous than our Milky Way.
The galaxy images, magnified through a phenomenon called gravitational lensing, reveal a tangled web of misshapen objects punctuated by exotic patterns such as rings and arcs. The odd shapes are due largely to the foreground lensing galaxies’ powerful gravity distorting the images of the background galaxies. The unusual forms also may have been produced by spectacular collisions between distant, massive galaxies in a sort of cosmic demolition derby.
“We have hit the jackpot of gravitational lenses,” said lead researcher James Lowenthal of Smith College in Northampton, Massachusetts. “These ultra-luminous, massive, starburst galaxies are very rare. Gravitational lensing magnifies them so that you can see small details that otherwise are unimaginable. We can see features as small as about 100 light-years or less across. We want to understand what’s powering these monsters, and gravitational lensing allows us to study them in greater detail.”
The galaxies are ablaze with runaway star formation, pumping out more than 10,000 new stars a year. This unusually rapid star birth is occurring at the peak of the universe’s star-making boom more than 8 billion years ago. The star-birth frenzy creates lots of dust, which enshrouds the galaxies, making them too faint to detect in visible light. But they glow fiercely in infrared light, shining with the brilliance of 10 trillion to 100 trillion suns.
Gravitational lenses occur when the intense gravity of a massive galaxy or cluster of galaxies magnifies the light of fainter, more distant background sources. Previous observations of the galaxies, discovered in far-infrared light by ground- and space-based observatories, had hinted of gravitational lensing. But Hubble’s keen vision confirmed the researchers’ suspicion.
Lowenthal presented his results June 6 at the American Astronomical Society meeting in Austin, Texas.
According to the research team, only a few dozen of these bright infrared galaxies exist in the universe, scattered across the sky. They reside in unusually dense regions of space that somehow triggered rapid star formation in the early universe.
The galaxies may hold clues to how galaxies formed billions of years ago. “There are so many unknowns about star and galaxy formation,” Lowenthal explained. “We need to understand the extreme cases, such as these galaxies, as well as the average cases, like our Milky Way, in order to have a complete story about how galaxy and star formation happen.”
In studying these strange galaxies, astronomers first must detangle the foreground lensing galaxies from the background ultra-bright galaxies. Seeing this effect is like looking at objects at the bottom of a swimming pool. The water distorts your view, just as the lensing galaxies’ gravity stretches the shapes of the distant galaxies. “We need to understand the nature and scale of those lensing effects to interpret properly what we’re seeing in the distant, early universe,” Lowenthal said. “This applies not only to these brightest infrared galaxies, but probably to most or maybe even all distant galaxies.”
Lowenthal’s team is halfway through its Hubble survey of 22 galaxies. An international team of astronomers first discovered the galaxies in far-infrared light using survey data from the European Space Agency’s (ESA) Planck space observatory, and some clever sleuthing. The team then compared those sources to galaxies found in ESA’s Herschel Space Observatory’s catalog of far-infrared objects and to ground-based radio data taken by the Very Large Array in New Mexico. The researchers next used the Large Millimeter Telescope (LMT) in Mexico to measure their exact distances from Earth. The LMT’s far-infrared images also revealed multiple objects, hinting that the galaxies were being gravitationally lensed.
These bright objects existed between 8 billion and 11.5 billion years ago, when the universe was making stars more vigorously than it is today. The galaxies’ star-birth production is 5,000 to 10,000 times higher than that of our Milky Way. However, the ultra-bright galaxies are pumping out stars using only the same amount of gas contained in the Milky Way.
So, the nagging question is, what is powering the prodigious star birth? “We’ve known for two decades that some of the most luminous galaxies in the universe are very dusty and massive, and they’re undergoing bursts of star formation,” Lowenthal said. “But they’ve been very hard to study because the dust makes them practically impossible to observe in visible light. They’re also very rare: they don’t appear in any of Hubble’s deep-field surveys. They are in random parts of the sky that nobody’s looked at before in detail. That’s why finding that they are gravitationally lensed is so important.”
These galaxies may be the brighter, more distant cousins of the ultra-luminous infrared galaxies (ULIRGS), hefty, dust-cocooned, starburst galaxies, seen in the nearby universe. The ULIRGS’ star-making output is stoked by the merger of two spiral galaxies, which is one possibility for the stellar baby boom in their more-distant relatives. However, Lowenthal said that computer simulations of the birth and growth of galaxies show that major mergers occur at a later epoch than the one in which these galaxies are seen.
Another idea for the star-making surge is that lots of gas, the material that makes stars, is flooding into the faraway galaxies. “The early universe was denser, so maybe gas is raining down on the galaxies, or they are fed by some sort of channel or conduit, which we have not figured out yet,” Lowenthal said. “This is what theoreticians struggle with: How do you get all the gas into a galaxy fast enough to make it happen?”
The research team plans to use Hubble and the Gemini Observatory in Hawaii to try to distinguish between the foreground and background galaxies so they can begin to analyze the details of the brilliant monster galaxies.
Future telescopes, such as NASA’s James Webb Space Telescope, an infrared observatory scheduled to launch in 2018, will measure the speed of the galaxies’ stars so that astronomers can calculate the mass of these ultra-luminous objects.
“The sky is covered with all kinds of galaxies, including those that shine in far-infrared light,” Lowenthal said. “What we’re seeing here is the tip of the iceberg: the very brightest of all.”
The Hubble Space Telescope is a project of international cooperation between NASA and ESA (European Space Agency). NASA’s Goddard Space Flight Center in Greenbelt, Maryland, manages the telescope. The Space Telescope Science Institute (STScI) in Baltimore conducts Hubble science operations. STScI is operated for NASA by the Association of Universities for Research in Astronomy, Inc., in Washington, D.C. | 0.885746 | 4.028295 |
On 30 September, Rosetta will descend towards a smooth region in Ma’at, on the smaller of the two lobes of Comet 67P/Churyumov-Gerasimenko. It will target a region that is home to several active pits measuring over 100 m wide and over 50 m deep, with the hope to get some close-up glimpses of these fascinating features.
The target site is seen in the image below of three pits in Ma’at (first presented in a paper published in July 2015); Rosetta will target the smooth region between the pits labelled Ma’at 02 and 03.
The large, well-defined pit adjacent to the target site and identified in the image above as Ma’at 02 has now been named by the mission team as Deir el-Medina, after a pit in an ancient Egyptian town of the same name.
The pit bears resemblance in appearance to the pit in the Egyptian town that was home to many of the workers that built the pharaoh tombs in the Valley of the Kings.
The pit of Deir el-Medina, which measures about 50 m deep and 30 m wide, was originally dug by the town’s inhabitants in an attempt to find a local source water. They were unsuccessful, however, because the water table of the Nile River was much lower than it was possible to dig. Eventually the pit became the dumping ground for ‘ostraka’ the name given to discarded pieces of pottery that were used to record activities of daily life. These included, for example, short messages, love notes, medical prescriptions, receipts, recipes, and drawings.
Just as the historical ‘debris’ that filled the pit gives historians insight into working life in that ancient town, so the rubble that can be seen inside Ma’at 02 is helping scientists to understand the history of Comet 67P/C-G.
Indeed, in addition to the rubble seen inside the pit, the walls also exhibit intriguing metre-sized lumpy structures called ‘goosebumps’. Rosetta scientists believe these could be the signatures of early cometesimals that merged together to create the comet in the early phases of Solar System formation. Rosetta’s descent over this region therefore offers the chance to capture close-up images of these important features.
In an earlier detailed study of Deir el-Medina and its neighbouring pits, scientists concluded that their differences in appearance may reflect their history of activity. While pits 1 and 2 are active, no activity has been observed from pit 3. The young, active pits are particularly steep-sided, whereas pits without any observed activity are shallower, have degraded rims, and seem to be filled with dust – and perhaps were active in the past. Middle-aged pits, like Deir el-Medina, tend to exhibit boulders on their floors from mass-wasting of the sides.
The pits – along with Rosetta’s target site – can be identified in many OSIRIS and NAVCAM images in the archive, affording many varied and spectacular views from different angles, and under a range of illumination conditions, as can be seen in some of the images accompanying this post. | 0.810775 | 3.786307 |
This write-up will be primarily concerned with the concept
of a space-time singularity, for example the one that lies at the heart
of a black hole.
As noted above, the singularity is a region of space and time where
the current accepted physical models; relativity and the quantum mechanical standard model, can make no predictions and offer
no insight to what lies within that region.
When an object forms a black hole its gravity overwhelms its matter,
crushing it into a smaller and smaller region, and physics as yet provides
no mechanism for this collapse to stop. Logically the matter occupies a
smaller and smaller region of space-time, all the way down to
infinitely small. In 1965 Roger Penrose in fact proved that
singularities must occur in gravitational collapses, regardless of the
symmetry or other properties of the initial mass.
Right now physics has enough tools to model this collapse right down to
the Planck length.When you use a microscope to observe something small,
you are limited by the wavelength you are using. A light microscope can
only resolve details the size of the wavelength of visible light. Due to
the wave particle duality nature of quantum mechanics however, you can use
particles such as electrons to resolve smaller details. If you boost these
particles to higher energies, their frequency increases, and you can again
resolve smaller details. In a way that's what particle accelerators are
for; particles of such high energy are used, you can resolve the very
fundamental particles that make up everything else.
When you get down to regions the size of the Planck length however, the
wavelength you need has an mass/energy (E=mc^2) sufficiently
large enough to form a black hole! However, if there is (as relativity and the standard model suggest), no limit to the 'smallness' of space, then there is still (in the same way you have an infinite number of integers, and an infinite number of reals between zero and one), the planck volume has still has 'space' for an infinity of things to happen!
The next physical models (such as super-string theory, loop quantum gravity) do not have this problem, as space/time is quantised; there is a fundamental unit to everything, past which or course you can't see. In fact there's hints that the 'theory of everything' must be 'background independent', that is the physics doesn't take place on some abstract mathmatical background, called space/time, rather space/time is a patchwork of discreet entities. As you've defined what the smallest bit of space is, then this must be a singularity in this formulation.
Do Singularities really matter anyway?
As I said physics can offer no answers as to what lies within the
(possibly) infinitely large region from the Planck size to the singularity. For
a long time physicists hoped the question was irrelevant as it appears
anything massive enough to collapse its matter down to infinity will be a
black hole and therefore have an event horizon associated with it.
Originally this event horizon was a one-way membrane, you can put
matter, energy and information past it, but nothing can come back
out of it. Any singularity hidden inside the black hole can therefore never
affect the rest of the universe, ever, and can therefore be forgotten
about. This cosmic censorship hypothesis (suggested by Penrose in
1969) says you can never have a
naked singularity; it must always be clothed by an event horizon.
Sleeping dogs have a habit of waking up....
Of course really you can't just let the problem lie there, several
important hypothesis that stem from the accepted correct (if incomplete)
physics mean you have to seriously think about the consequences of
allowing physics to 'make' a singularity.
Firstly cosmology has long sought to explain the origin and
evolution of the universe. Observations by Edwin Hubble seemed to
suggest all the galaxies are moving away from each other, at a rate
proportional to their distance from us. This implied that once they were
very close together, in fact tracing backwards infinitely close
together...This lead to the formulation of the big bang theory, where
the entire universe essentially exploded from an infinitely small region; of course this is a singularity!. Every observation made has so far has
confirmed some kind of big bang occurred, refinements such as cosmological
inflation don't alter the fundamental fact that the theory must have
contain a singularity, a fact proved by Hawking.
As you can't see past the Planck length, you can't make predictions what
came out of the singularity at the dawn of time, in fact as I said above
you could regard the evolution of the universe from the singularity up
past the Planck length to have as rich a history as our own universe since
the Planck length. As what came before must determine what comes
after, cosmology has a real problem with singularities.....
Secondly work by Professor Stephen Hawking and other have shown black
holes are not in fact completely black, and do in fact radiate at a
wavelength proportional to their size. (Please see Hawking radiation
for more). A consequence of this is they might radiate away, (over
time) all their energy, which could leave a naked singularity
behind. What effect a naked singularity would have on the rest of the
universe, I don't think anybody knows, I'm pretty sure you can't in fact
calculate the effect of this space-time infinity.
Also it's just occurred to me, if you allow sizes smaller than the
Planck length to exist, (even if you can't measure them) then when a black
hole decays past a certain point, it can emit radiation/particles of
sufficient energy to again be black hole, containing a singularity.
This would be a self-perpetuating growth, a free lunch of infinite size,
something, which I personally do not believe, is possible.
Out with the old in with the new?
So the 'old' physics seems to predict singularities as a logical
consequence, but cannot offer any theories of their behaviour; the
mathematics simply breaks down. The current hot 'new' physics is
superstring theory and its partner m-theory. In these space-time is
quantised in that it can only come in 'packets' limited to
about the Planck length in size. These strings or branes do away with the
concept of infinitely small and in doing solve a lot of problems in
physics. In these theories (and there are many, and no-one knows how the one
that describes our universe came to be chosen) a black hole would collapse
to a string or a brane and no further. The question then arises can the string/brane that is the end product of the gravitational collapse a.k.a. the singularity, contain the necessary energy and information necessary to describe the black hole?
My own two-penneth
I think in this string/brane picture the cosmic censorship can be maintained, I believe
that the singularity becomes a topologically complicated knot
of 11 dimensional space-time. The emission of particles from the event
horizon represents decay of this 'singular' knot, as it decays, it loses
energy/mass and the horizon shrinks. At the point where the horizon
shrinks to nothing, the 'singularity' finally decays in a flash of
Hawking radiation. I think by redefining the singularity in such a way
might help some of the problems involved in black hole entropy also, (I
humbly refer to my node there...).
This w/u was done in response to the The content rescue team:nodes Largely of the top of my head, any errors/typos/glaring omissions please msg me!
Recent work in knot theory has shown that knots may in fact be quantised
also. This would mean that some modes of decay for knot/singularity might
well be forbidden, which could give rise to 'absorbance lines' in the
spectra of black hole radiation. If two cosmic rays of sufficient
energy were to collide they could form a black hole in the order of the
Planck size, and the above effect could be seen as it decays.... | 0.816654 | 3.996804 |
NASA is pitting two proposals against each other to win a contract worth $75 million. The goal of the contract is for the winning proposal to help discover the fundamental nature of the universe, which mainly involves the Sun’s heliosphere.
Furthermore, the winning proposal will tag along with another mission with the Interstellar Mapping and Acceleration Probe that is scheduled to launch on October 2024.
For now, the space agency NASA wants to give the two chosen proposal developmental funding worth up to $400,000 each. Only the selected mission will receive up to $75 million to prepare for a journey to a Lagrangianpoint or L1, a stable gravitational location between Earth and the sun.
This mission would build on our knowledge about the Sun’s heliosphere— or the sun’s sphere of influence, particularly regarding the solar wind particles which steam from its surface.
Significantly, the heliosphere is considered as a safe zone from the harsh and penetrative forces of the universe. It is created by our Sun’s solar wind, which spread across the galaxy encompassing it like a bubble. This bubble offers the possibility for inside it to survive and thrive.
However, astronomers are not completely sure where the heliosphere exactly ends. Thus, they cannot, for certain, make ground assurances of up until what distance can a planet host life.
So far, only two spacecraft have ever ventured into the interstellar medium: Voyager 1 and Voyager 2. Unfortunately, these two spacecraft—launched in 1977—is set to stop functioning in 2020, which calls for a newer and more in-depth study into what NASA refers to as the fundamental nature of the universe and how certain celestial respond to planetary atmospheres, radiation from the Sun, and interstellar particles.
Thanks to the space agency’s new SMD Rideshare Initiative, which cuts costs by sending multiple missions on a single launch, at least one of the chosen proposals will advance NASA’s heliophysics program and could lead to better protection for both technology and humans as we travel farther from home.
The first two of the chosen proposals is SILHA or the Spatial/Spectral Imaging of Heliospheric Lyman Alpha whose principal investigator is Larry Paxton, who also currently serves as the head of the geospace and Earth science group at the Johns Hopkins University Applied Physics Laboratory in Maryland.
“SIHLA would map the entire sky to determine the shape and underlying mechanisms of the boundary between the heliosphere, the area of our sun’s magnetic influence, and the interstellar medium, a boundary known as the heliopause,” NASA said in a statement.
“The observations would gather far-ultraviolet light emitted from hydrogen atoms. This wavelength is key for examining many astrophysical phenomena, including planetary atmospheres and comets because so much of the universe is composed of hydrogen.”
Meanwhile, the second proposal, which Lara Waldrop is the principal investigator, would look at Earth’s upper atmosphere, also known as the exosphere, by looking at the ultraviolet light that hydrogen emits.
Waldrop is an assistant professor of electrical and computer engineering at the University of Illinois, Champaign-Urbana.
Her proposal, also known as the Global Lyman-alpha Imagers of the Dynamic Exosphere (GLIDE) are particularly interested in learning how “space weather,” or the Sun’s solar radiation and other effects, can interfere with radio communications in space. Since spacecraft generally use radio to communicate with Earth, predicting interference is vital to keeping science flowing across the solar system.
“The proposed mission would fill an existing measurement gap, as only a handful of such images previously have been made from outside the exosphere,” NASA said in the same statement. “The mission would gather observations at a high rate, with a view of the entire exosphere, ensuring a truly global and comprehensive set of data.”
Separately, this launch will also include a HeliophysicsTechnology Demonstration Mission of to test technologies that can enable future science missions, and the National Oceanic and Atmospheric Administration’s (NOAA) Space Weather Follow-On mission, which will expand that agency’s space weather forecasting capabilities. | 0.921577 | 3.50844 |
Planetary geology is the geology of astronomical objects apparently in orbit around one or more stellar objects within a few light years.
Planetary geology may also be thought of as the geology of an astronomical object that is due to its planetary nature:
- approximate hydrostatic equilibrium (apparently spherical shape),
- a cleared orbital path, and
- an orbit around one or more stellar objects.
Planetary geology, astrogeology or exogeology, are planetary sciences concerned with the geology of the celestial bodies such as the planets and their moons, asteroids, comets, and meteorites. It includes determining the internal structure of the terrestrial planets, planetary volcanism and surface processes such as impact craters, fluvial and aeolian processes.
Def. the intellectual and practical activity encompassing the systematic study through observation and experiment of the Earth's physical structure and substance, its history and origin, and the processes that act on it, especially by examination of its rocks, is called geology.
Def. "a celestial body that
(a) is in orbit around the Sun,
(b) has sufficient mass for its self-gravity to overcome rigid body forces so that it assumes a hydrostatic equilibrium (nearly round) shape, and
(c) has cleared the neighbourhood around its orbit" is called a planet.
Def. a wanderer that is a moving light in the sky is called a planet.
This is the original description meant by the word "planet".
Def. a celestial body "formed by accumulation of a rocky core, on a much longer timescale, ≳ 107 yr, with subsequent acquisition of a gaseous envelope if the circumstances allow this, and with an initially fractionated elemental composition" is called a planet.
Theoretical planetary geology
Def. a nearly round or spherically shaped, astronomical object that appears to have cleared its orbit around one or more stellar objects less than a few light years away is called a planet, or planet-like object.
Def. the geology of matching up objects on or in planetary, or planet-like, objects to suggest or infer parallel evolution is called planetary geology.
Def. the astronomy of observing on or in astronomical objects so as to geologically match up likely parallel evolution is called astrogeology.
Planetary geology is focused on the effects to an astronomical object, source, or entity from being in an orbit around any astronomical object, source, or entity less than a few light years away.
Def. any "considerable and connected part of a space or surface; specifically, a tract of land or sea of considerable but indefinite extent; a country; a district; in a broad sense, a place without special reference to location or extent but viewed as an entity for geographical, social or cultural reasons" is called a region.
Oblique images such as the one at the top right are taken by astronauts looking out from the ISS at an angle, rather than looking straight downward toward the Earth (a perspective called a nadir view), as is common with most remotely sensed data from satellites. An oblique view gives the scene a more three-dimension quality, and provides a look at the vertical structure of the volcanic plume. While much of the island is covered in green vegetation, grey deposits that include pyroclastic flows and volcanic mud-flows (lahars) are visible extending from the volcano toward the coastline. When compared to its extent in earlier views, the volcanic debris has filled in more of the eastern coastline. Urban areas are visible in the northern and western portions of the island; they are recognizable by linear street patterns and the presence of bright building rooftops. The silver-grey appearance of the Caribbean Sea surface is due to sun-glint, which is the mirror-like reflection of sunlight off the water surface back towards the hand-held camera on-board the ISS. The sun-glint highlights surface wave patterns around the island.
Slate is a fine-grained, foliated, homogeneous metamorphic rock derived from an original shale-type sedimentary rock composed of clay or volcanic ash through low-grade regional metamorphism. It is the finest grained foliated metamorphic rock. Foliation may not correspond to the original sedimentary layering, but instead is in planes perpendicular to the direction of metamorphic compression. Slate is frequently grey in color, especially when seen, en masse, covering roofs. However, slate occurs in a variety of colors even from a single locality; for example, slate from North Wales can be found in many shades of grey, from pale to dark, and may also be purple, green or cyan.
As the image at the right and those in the sources section shows, volcanoes are a source of emissions.
In contrast to the Proterozoic, Archean rocks are often heavily metamorphized deep-water sediments, such as graywackes, mudstones, volcanic sediments and banded iron formations.
Greenstone belts are typical Archean formations, consisting of alternating high- and low-grade metamorphic rocks. The high-grade rocks were derived from volcanic island arcs, while the low-grade metamorphic rocks represent deep-sea sediments eroded from the neighboring island arcs and deposited in a forearc basin. In short, greenstone belts represent sutured protocontinents.
Greenstone belts are zones of variably metamorphosed mafic to ultramafic volcanic sequences with associated sedimentary rocks that occur within Archaean and Proterozoic cratons between granite and gneiss bodies.
The name comes from the green hue imparted by the colour of the metamorphic minerals within the mafic rocks. Chlorite, actinolite and other green amphiboles are the typical green minerals.
A greenstone belt is typically several dozens to several thousand kilometres long and although composed of a great variety of individual rock units, is considered a 'stratigraphic grouping' in its own right, at least on continental scales.
"Greenstone belts" are distributed throughout geological history from the Phanerozoic Franciscan belts of California where blueschist, whiteschist and greenschist facies are recognised, through to the Palaeozoic greenstone belts of the Lachlan Fold Belt, Eastern Australia, and a multitude of Proterozoic and Archaean examples.
Archaean greenstones are found in the Slave craton, northern Canada, Pilbara craton and Yilgarn Craton, Western Australia, Gawler Craton in South Australia, and in the Wyoming Craton in the US. Examples are found in South and Eastern Africa, namely the Kaapvaal craton and also in the cratonic core of Madagascar, as well as West Africa and Brazil, northern Scandinavia and the Kola Peninsula (see Baltic Shield).
Phanerozoic ophiolite belts and greenstone belts occur in the Franciscan Complex of south-western North America, within the Lachlan Fold Belt, the Gympie Terrane of Eastern Australia, the ophiolite belts of Oman and around the Guiana Shield.
"Spectral properties of certain palagonitic soils found on Mauna Kea, Hawaii are similar to the spectral properties measured by earth-based telescopes for Martian soils [1,2,3]. ... Three layers with distinctly different colors (upper red, middle black, lower yellow) were sampled from hydrothermally altered basaltic tephra just below the summit of Mauna Kea."
"The clay fractions (< 2 µm) of three palagonite samples-MK11 (red), MK12 (black), and MK13 (yellow) collected at an elevation of 4145 meters near the summit of Mauna Kea volcano in Hawaii ... The fine fractions of the black (MK12) and yellow (MK13) samples were similar to those of martian bright regions in terms of their overall shape."
"Geologic evidence suggests that large amounts of water have likely flowed on Earth for the past 3.8 billion years—most of its existence. [It is] [b]elieved to have initially arrived on the surface through the emissions of ancient volcanoes".
Def. a "portion of land or territory which the eye can comprehend in a single view, including all the objects it contains" is called a landscape.
Def. each continuous surface of a landscape that is observable in its entirety and has consistence of form or regular change of form is called a landform.
Def. "[t]he study of landforms, their classification, origin, development, and history" is called geomorphology.
"A higher-reflectance [HR], relatively red material occurs [on Mercury] as a distinct class of smooth plains [P] that were likely emplaced volcanically; a lower-reflectance material with a lesser spectral slope may represent a distinct crustal component enriched in opaque minerals, possibly more common at depth."
"The distinctively red smooth plains (HRP) appear to be large-scale volcanic deposits stratigraphically equivalent to the lunar maria (20), and their spectral properties (steeper spectral slope) are consistent with magma depleted in opaque materials. The large areal extent (>106 km2) of the Caloris HRP is inconsistent with the hypothesis that volcanism was probably shallow and local (10); rather, such volcanism was likely a product of extensive partial melting of the upper mantle."
"Despite the dearth of ferrous iron in silicates, Mercury's surface nonetheless darkens and reddens with time like that of the Moon. This darkening and reddening has been interpreted to be the result of production of nanophase iron (e.g., Pieters et al., 2000; Hapke, 2001), which could be derived from an opaque phase in the crustal material or from delivery by micrometeorite impacts (Noble and Pieters, 2003). On the Moon, deposits that are brighter and redder than the average Moon spectrum appear to be lower in iron (e.g., highland material); deposits that are darker and redder than average are higher in iron (e.g., low-Ti mare material) (Lucey et al., 1995)."
Def. a solid, or rocky, surface of an astronomical rocky object is called land.
- a "single, distinctive rock formation",
- "an area having a preponderance of a particular rock or group of rocks", or
- an "area of land or the particular features of it"
is called a terrain.
A terrestrial planet, telluric planet or rocky planet is a planet that is composed primarily of silicate rocks or metals. Within the Solar System, the terrestrial planets are the inner planets closest to the Sun. The terms are derived from Latin words for Earth (Terra and Tellus), so these planets are, in a certain way, "Earth-like". Terrestrial planets have solid planetary surface making them substantially different from gas giants, which are composed mostly of some combination of hydrogen, helium, and water existing in various physical states.
Petrology is a branch of geology that studies rocks, and the conditions in which rocks form. Lithology focuses on macroscopic hand-sample or outcrop-scale description of rocks, while petrography deals with microscopic details. Petrology benefits from mineralogy, optical mineralogy, geochemistry, and geophysics. Three branches of petrology focus on the three major rock types: igneous petrology, metamorphic petrology, and sedimentary petrology.
Def. "[t]he study of ice and its effect on the landscape, especially the study of glaciers" is called glaciology.
The location of Mt. Hibok-Hibok volcano imaged at the right is on the Camiguin Island in the Philippines. This eruption produced an ashflow, which killed about 500 people.
The eruption in 1951 produced pyroclastic material and lava on the December 4, 1951. This encased bodies in gray material. Most of the people were found as if they were just asleep.
In the image at right, planetary geologist and NASA astronaut Harrison "Jack" Schmitt collects lunar samples during the Apollo 17 mission.
"NASA's Galileo spacecraft took this image of dark terrain within Nicholson Regio, near the border with Harpagia Sulcus on Jupiter's moon Ganymede. The ancient, heavily cratered dark terrain is faulted by a series of scarps."
"The faulted blocks form a series of "stair-steps" like a tilted stack of books. On Earth, similar types of features form when tectonic faulting breaks the crust and the intervening blocks are pulled apart and rotate. This image supports the notion that the boundary between bright and dark terrain is created by that type of extensional faulting."
"North is to the right of the picture and the Sun illuminates the surface from the west (top). The image is centered at -14 degrees latitude and 320 degrees longitude, and covers an area approximately 16 by 15 kilometers (10 by 9 miles). The resolution is 20 meters (66 feet) per picture element. The image was taken on May 20, 2000, at a range of 2,090 kilometers (1,299 miles)."
Def. the "physical structure of a particular region [or] terrain" is called geography.
"Historical geology is a study of life forms represented in the fossil record, as well as the chronology of geologic processes."
The image at the right shows two geochronologists and one paleontologist collecting ash at the Cretaceous-Paleogene Boundary in Wyoming, USA.
The prehistory period dates from around 7 x 106 b2k to about 7,000 b2k.
Archaeology "studies human cultures through the recovery, documentation and analysis of material remains and environmental data, including architecture, artifacts, ecofacts, human remains, and landscapes."
The recent history period dates from around 1,000 b2k to present.
Sedimentary rocks cover most of the Earth's surface, record much of the Earth's history, and harbor the fossil record. Sedimentology is closely linked to stratigraphy, the study of the physical and temporal relationships between rock layers or strata.
In the image at the right, geophysicists from the Department of Earth Science at Aarhus University perform electrical measurements (DC/IP) at Ulstrup in Denmark. Studerende fra Instituttet for Geologi ved Århus Universitet, der udfører geofysisk feltarbejde i Ulstrup nær Viborg.
The image at the right shows rock strata in Cafayate, Argentina, the subject of stratigraphy.
Structural geology is the study of the three-dimensional distribution of rock units with respect to their deformational histories.
- The geologic effects on an apparently spherical astronomical object, source, or entity of being in an orbit around one or more stellar objects is distinct from other geologic effects.
- Lars Lindberg Christensen (August 24, 2006). "IAU 2006 General Assembly: Result of the IAU Resolution votes" (PDF). International Astronomical Union. Retrieved 2011-10-30.
- Anthony Whitworth, Dimitri Stamatellos, Steffi Walch, Murat Kaplan, Simon Goodwin, David Hubber and Richard Parker (2009). R. de Grijs & J. R. D. Lépine. ed. The formation of brown dwarfs, In: Star clusters: basic galactic building blocks, Proceedings IAU Symposium No. 266. International Astronomical Union. pp. 264-71. doi:10.1017/S174392130999113X. http://arxiv.org/pdf/astro-ph/0602367. Retrieved 2011-10-30.
- wikt:User:Vildricianus:Vildricianus (25 March 2006). region. San Francisco, California: Wikimedia Foundation, Inc. Retrieved 2012-09-10.
- Essentials of Geology, 3rd Ed, Stephen Marshak
- Stanley 1999, pp. 302–303
- D. C. Golden, R. V. Morris, D. W. Ming, R. K. Vempati, and H. V. Lauer (March 1991). "Mineralogy of Palagonitic Soils from Hawaii". Abstracts of the Lunar and Planetary Science Conference 22 (03): 449-50. http://adsabs.harvard.edu/abs/1991LPI....22..449G. Retrieved 2013-09-14.
- D. C. Golden, D. W. Ming, R. V. Morris and H. V. Lauer Jr. (December 1992). Mars surface weathering products and spectral analogs: Palagonites and synthetic iron minerals, In: Workshop on the Martian Surface and Atmosphere Through Time. Lunar and Planetary Institute. pp. 59-60. http://adsabs.harvard.edu/full/1992msat.work...59G. Retrieved 2013-09-15.
- Steve Graham, Claire Parkinson, and Mous Chahine (October 1, 2010). The Water Cycle. Washington, DC USA: NASA. Retrieved 2013-05-29.CS1 maint: multiple names: authors list (link)
- "landscape, In: Wiktionary". San Francisco, California: Wikimedia Foundation, Inc. October 6, 2013. Retrieved 2013-11-09.
- "geomorphology, In: Wiktionary". San Francisco, California: Wikimedia Foundation, Inc. October 7, 2013. Retrieved 2013-11-09.
- Mark S. Robinson, Scott L. Murchie, David T. Blewett, Deborah L. Domingue, S. Edward Hawkins III, James W. Head, Gregory M. Holsclaw, William E. McClintock, Timothy J. McCoy, Ralph L. McNutt Jr., Louise M. Prockter, Sean C. Solomon, Thomas R. Watters (July 4, 2008). "Reflectance and Color Variations on Mercury: Regolith Processes and Compositional Heterogeneity". Science 321 (5885): 66-9. doi:10.1126/science.1160080. http://www.sciencemag.org/content/321/5885/66.short. Retrieved 2013-07-28.
- Laura Kerber, James W. Head, Sean C. Solomon, Scott L. Murchie, David T. Blewett, Lionel Wilson (2009). [http://www.sciencedirect.com/science/article/pii/S0012821X09002611 "Explosive volcanic eruptions on Mercury: Eruption conditions, magma volatile content, and implications for interior volatile abundances"]. Earth and Planetary Science Letters 285: 263-71. doi:10.1016/j.epsl.2009.04.037. http://www.sciencedirect.com/science/article/pii/S0012821X09002611. Retrieved 2013-07-28.
- "terrain, In: Wiktionary". San Francisco, California: Wikimedia Foundation, Inc. October 7, 2013. Retrieved 2013-11-09.
- "glaciology, In: Wiktionary". San Francisco, California: Wikimedia Foundation, Inc. 1 April 2014. Retrieved 2014-08-13.
- Autumn Burdick (December 16, 2000). PIA02582: Stair-step Scarps in Dark Terrain on Ganymede. Pasadena, California USA: NASA/JPL. Retrieved 2014-06-12.
- "geography, In: Wiktionary". San Francisco, California: Wikimedia Foundation, Inc. November 6, 2013. Retrieved 2013-11-09.
- JT Bradley (31 January 2011). COUNTY JANUARY JULY HIGH LOW HIGH LOW Charlotte 74 51 Lee 74 52 Collier 76 52 (PDF). library.fgcu.edu. Retrieved 2011-12-31.
- Crazedandinfused (September 6, 2007). Difference between revisions of "Topic:Archeology". Retrieved 2013-01-13.
- Raymond Siever, Sand, Scientific American Library, New York (1988), ISBN 0-7167-5021-X.
- P.E. Potter, J.B. Maynard, and P.J. Depetris, Mud and Mudstones: Introduction and Overview Springer, Berlin (2005) ISBN 3-540-22157-3.
- Georges Millot, translated [from the French] by W.R. Farrand, Helene Paquet, Geology Of Clays - Weathering, Sedimentology, Geochemistry Springer Verlag, Berlin (1970), ISBN 0-412-10050-9.
- Gary Nichols, Sedimentology & Stratigraphy, Wiley-Blackwell, Malden, MA (1999), ISBN 0-632-03578-1.
- African Journals Online
- Bing Advanced search
- Google Books
- Google scholar Advanced Scholar Search
- International Astronomical Union
- Lycos search
- NASA/IPAC Extragalactic Database - NED
- NASA's National Space Science Data Center
- NCBI All Databases Search
- Office of Scientific & Technical Information
- PubChem Public Chemical Database
- Questia - The Online Library of Books and Journals
- SAGE journals online
- The SAO/NASA Astrophysics Data System
- Scirus for scientific information only advanced search
- SDSS Quick Look tool: SkyServer
- SIMBAD Astronomical Database
- SIMBAD Web interface, Harvard alternate
- Spacecraft Query at NASA
- Taylor & Francis Online
- Universal coordinate converter
- Wiley Online Library Advanced Search
- Yahoo Advanced Web Search | 0.906038 | 3.581934 |
Scientists have observed how a magnetic dipole field can create what looks like a glowing, localised fireball inside a plasma chamber.
By placing a regular dipole bar magnet near the surface of the cathode, the researchers were able to generate an intense “glowing, fireball like structure”inside the plasma chamber, which varied in its brightness depending on how they positioned the magnet.
According to the team from the Saha Institute of Nuclear Physics in India, the localised glowing results from increased ionisation in the plasma chamber, due to the way electrons are confined by the magnetic field near the negatively charged cathode surface.
Scientists have previously conducted a range of research on how magnetism interacts with plasma using chambers just like this, but most of the time those experiments involve a magnet positioned inside the chamber – which means variations in the strength of the magnetic field don’t usually show up.
By placing and repositioning a mobile magnet on the outside of the chamber, however, it highlights a different effect of the magnetic field.
“Though bar magnets have been used in plasma experiments, the focus was mainly on the measurement of plasma equilibrium parameters like density, potential, and other fluctuation measurements,” says lead researcher Pankaj Kumar Shaw.
“In our opinion, this is the first effort to investigate nonlinear dynamical phenomena of the fluctuations under dipolar magnetic field.”
When a magnetic field is introduced to plasma, it induces fluctuations in the plasma, which become less ordered and more chaotic as the strength of the magnetic field increases.
While scientists already knew about this effect, the researchers here discovered that the transition from order to chaos in the plasma reflects what’s called period-doubling bifurcation – a mathematical equation that explains how systems can repeat in a doubling pattern in response to changes in parameters.
“Following a particular sequence from order to chaos via [a] period-doubling route was unexpected,” says Shaw.
“Changing position of the bar magnet varied the strength of magnetic field over 1–10G. This observation in such a low range of magnetic field was surprising.”
Aside from the cool fireball effect, the results may largely be of theoretical interest for other plasma researchers right now, but the team thinks that in the future the findings could impact the study of how magnetic anomalies affect solar wind interactions with planetary bodies.
Tbh, that’s a pretty academic area too, but it’s one that could also have massive repercussions on future space exploration and colonisation inside our Solar System – especially since NASA has indicated it wants to study the possibilities of launching a giant magnetic field to make Mars habitable again.
The idea there is that, over the passing of galactic eons, the Red Planet may have lost its once lush atmosphere, which was stripped away by high-energy particlesprojected from the Sun.
Understanding more about how plasma and magnetic fields play together could be a vital step in learning how to restore the Martian atmosphere, by reinstating the Red Planet’s own magnetic field.
Of course, that’s a pretty giant leap from the discovery we’re telling you about today – but it’s all part of a scientific continuum, folks.
One little fireball could help us heal the hurt created by a much bigger one.
The findings are reported in Physics of Plasmas. | 0.845047 | 4.036096 |
14,710 total views, 2 views today
Galileo is credited as the father of advanced observational space science. He created telescopes with amplification up to 30X, preceding crafted by Galileo about all space science was finished with the exposed eye.
Utilizing his telescopes he found the four biggest moons of Jupiter, watched sunspots, and affirmed the periods of Venus with his new innovation. He likewise upheld the heliocentric models of Copernicus, however he was pestered by the Pope, the Spanish Inquisition, and kindred space experts for doing as such.
At the point when not watching the night sky, Galileo examined the movement of bodies. This work would fill in as an antecedent to established mechanics created by Isaac Newton.
Isaac Newton’s work in the fields of material science and math are limitlessly essential to advanced information of room. His three all inclusive laws of movement shape the foundation of material science and he is one of two men credited with the advancement of math.
Newton demonstrated both Kepler’s laws of planetary movement and the heliocentric idea of the close planetary system. He likewise built up the primary reasonable reflecting telescope.
His work in the investigation of gravity would be instrumental in the advancement of future hypotheses concerning the working of astronomy. So, the material science that today enable us to dispatch a payload into space and to recognize what it will do when it arrives, began with crafted by Isaac Newton.
Ptolemy was one of the primary space experts. He created one of the soonest known models of the universe in light of his perceptions of the night sky. His model set earth at the focal point of a few “divine circles” to which the sun, stars, and different planets were settled.
His model was one of the first to represent the “meandering” of the planets in the night sky. His galactic treatises the Almagest and the Tetrabiblos classified 48 groups of stars and gave a table to cosmic forecasts that were utilized by future space experts. Crafted by Ptolemy shaped the premise of space science for more than a thousand years.
Copernicus is most celebrated for his advancement of one of the primary heliocentric models of the Universe. A heliocentric model is one in which the sun is the middle. Copernicus alluded to the perceptions of Ptolemy while building up his model.
Other than specifically promoting our insight into the universe, Copernicus’ thoughts are credited for beginning the logical upheaval. The logical insurgency prompted the advancement of about all cutting edge innovation and logical information.
Kepler is best known for his laws of planetary movement which portray the movement of the planets around the sun. His three laws would later be demonstrated by Isaac Newton.
His first and most basic law uncovered that the circles of the planets around the sun were not superbly round as beforehand accepted. They were in reality curved.
An oval is a stretched hover having of two foci or center focuses. Every planet ventures an oval around the sun which is situated on one of the two foci. Kepler likewise imagined an enhanced rendition of the refracting telescope utilized by Galileo.
Edwin Hubble is best known for his namesake law “Hubble’s Law,” which developed the marvel of “red-move.” Red-move is a wonder most promptly detectable in space whereby the light from sources voyaging far from us move towards the red end of the range.
The inverse of red-move is blue-move. This enables researchers to decide if questions in space, similar to cosmic systems and stars, are moving far from us or towards us and how quick they are going. Almost all discernible systems show red-move, which give prove that the universe is extending. The renowned Hubble Telescope is named after Edwin Hubble. | 0.902371 | 3.086642 |
NEAR Shoemaker was a NASA Discovery program spacecraft designed to
study near Earth asteroids. It completed its mission on February 28th, 2001, when it returned the last of its gamma-ray spectrometer data. NEAR, never designed to land, had touched down on 433 Eros on February 12, 2001, and was still able to gather a last few scientific readings and send them to Earth. NEAR was the first spacecraft ever to land on an asteroid.
NEAR, or the Near Earth Asteroid Rendezvous spacecraft, recently
renamed NEAR Shoemaker in honor of Gene Shoemaker, departed from
Earth aboard a Delta II Lite launch vehicle on February 17th, 1996,
bound for a rendezvous with near Earth asteroid 433 Eros. After a
successful DETUMBLE maneuver, performed after deploying its solar
panels, and five TCMs (trajectory correction maneuvers), NEAR was on
its way to a flyby of asteroid 253 Mathilde. The flyby of Mathilde
occurred on June 27th 1997, and on July 7th, the first major deep
space maneuver using the craft's LVA (large velocity adjust) thruster
was executed. Five more TCMs saw NEAR to its Earth swingby, which
occurred on January 23rd, 1998 UTC 07:22:56.6 at an altitude of 540
On December 20th 1998 at 22:00 UTC, after a successful 200 second
fuel settling burn, TCM 16 aborted after 0.2 seconds. A few seconds
later, all communication with the craft was lost. Contact was not
regained until 27 hours later, when it was discovered that NEAR had
experienced low-voltage conditions, lost 29 kg of fuel, and
encountered an attitude anomaly. The abort of TCM 16 meant that NEAR
would fly by Eros on December 23rd 1998 at 18:41:23 UTC, rather than
rendezvous with it. Mission controllers scrambled to find out what
went wrong and how the mission could be salvaged. On January 3rd
1999, TCM 17 occurred, which lasted for 24 minutes and enabled NEAR to
eventually rendezvous with Eros on February 14th 2000, thirteen months
behind schedule. An investigation team was formed to find the cause of
the December 20th burn abort, and the findings of that team are the
subject of the NEAR Burn Anomaly Report.
The OIM (orbital insertion maneuver), occurred on February 14th 2000
at 15:33:06 UTC. This event made NEAR the first craft to ever orbit an
asteroid. NEAR initially orbited in a 321 km by 366 km elliptical
path, but various maneuvers have since brought the spacecraft to within
50 km of Eros. A soft landing on Eros on February 12th, 2001, at 03:01:52 EST put NEAR in the history books as the first spacecrat ever to land on an asteriod. During its descent, NEAR was able to take 69 photographs which showed new detail never seen before. After its landing, NEAR was still able to communicate with Earth using its low gain antenna, and found itself in an excellent position to gather additional information about the composition of Eros with its gamma-ray spectrometer.
NEAR transmitted its final message to Earth on February 28th, 2001. NEAR's final resting place is just south of Himeros, a saddle shaped feature on Eros.
The primary goals of the NEAR mission are to study the
properties, composition, mineralogy, morphology, internal mass
distribution, and magnetic field of the near Earth asteroid
Eros. The secondary goals include the study of regolithic
properties, solar wind interactions, dust and gas activity, and the
spin rate of the asteroid.
The NEAR Shoemaker spacecraft has an octagonal prism shape, and is
about 1.7 meters long on each side. NEAR is three axis stabilized, it
has fixed solar panels and instruments, redundant critical
subsystems, and a passive thermal design. The overall mass of the
craft, including propellant, is 805 kg. Attitude control is
maintained through the use of reaction wheels and thrusters.
Four gallium arsenide solar panels in a windmill arrangement provide
power, 1800 watts at 1 AU. Power is stored in 9 amp, 22 cell
rechargeable batteries. A fixed 1.5 meter X-band high gain
radio antenna provides telemetry via the NASA deep space
The craft's large velocity adjust thruster uses a bipropellent of
hydrazine and nitrogen trioxide, and produces an output of 450
N. Four 21 N and seven 3.5 N hydrazine thrusters provide additional
thrust and attitude control. All thrusters combined give NEAR a Delta
V of 1450 m/s. 209 kg of hydrazine and 109 kg of oxidizer (nitrogen
trioxide) are stored in two oxide and three fuel tanks.
NEAR carries 56 kg of instrumentation, which consume 81 watts of
power. These instruments are an x-ray and gamma ray spectrometer, an
infared spectragraph, a multi-spectral camera (CCD detector), a
laser rangefinder, and a magnetometer.
Guidance data is provided by five digital solar attitude detectors,
an inertial measurement unit (IMU), and a star tracker
camera. Command and data processing functions are handled by two
redundant command and telemetry processors. The spacecraft carries two
solid state data recorders, which are 16 MBit Luna-C DRAMs.
NEAR was launched under NASA's discovery program. Construction,
launch, and 30 day operating cost of NEAR is estimated at $122 Million.
NEAR Shoemaker has gathered a lot of data during its time in
space. Much of this data is available at http://near.jhuapl.edu/, along
with a lot of other information about NEAR Shoemaker. | 0.860971 | 3.588566 |
Dust devil tracks. Image credit: NASA/JPL. Click to enlarge
Ah, Martian summer! Finally, the days are long, just like on dear old Earth. And daytime highs rocket all the way up to a balmy 20?C (68?F) from the summer nighttime low of -90?C (-130?F), meaning you and your fellow astronauts can warm up your machinery earlier to get a good start on mining operations.
Dust devils on Mars form the same way they do in deserts on Earth. “You need strong surface heating, so the ground can get hotter than the air above it,” explains Lemmon. Heated less-dense air close to the ground rises, punching through the layer of cooler denser air above; rising plumes of hot air and falling plumes of cool air begin circulating vertically in convection cells. Now, if a horizontal gust of wind blows through, “it turns the convection cells on their sides, so they begin spinning horizontally, forming vertical columns–and starting a dust devil.”
Hot air rising through the center of the column powers the whirling air ever faster–fast enough to begin picking up sand. Sand scouring the ground then dislodges flour-fine dust, and the central column of hot rising air buoys that dust high aloft. Once prevailing horizontal winds begin pushing the dust devil across the ground, look out!
“If you were standing next to the Spirit rover right now [in Gusev Crater] in the middle of the day, you might see half a dozen dust devils,” says Lemmon. Each Martian spring or summer day, dust devils begin appearing about 10 AM as the ground heats, and start abating about 3 PM as the ground cools (Mars’s solar day of 24 hours 39 minutes is only 39 minutes longer than Earth?s). Although the exact frequency and duration of Martian dust devils is unknown, photographs from Mars Global Surveyor in orbit reveal innumerable wandering tracks at all latitudes on the planet. These tracks crisscross the surface where dust devils have scoured away loose surface material to reveal different-colored soil beneath.
Moreover, actual dust devils have been photographed from orbit–some of them as large as 1 to 2 kilometers across at their base and (from their shadows) clearly towering 8 to 10 km high.
What intrigues Farrell from having chased dust devils in the Arizona desert, however, is the strange fact that terrestrial dust devils are electrically charged–and Martian dust devils might be, too.
Dust devils get their charge from grains of sand and dust rubbing together in the whirlwind. When certain pairs of unlike materials rub together, one material gives up some of its electrons (negative charges) to the other material. Such separation of electric charges is called triboelectric charging, the prefix “tribo” (pronounced TRY-bo) meaning “rubbing.” Triboelectric charging makes your hair stand on end when you rub a balloon against your head. Dust and sand, like plastic and hair, form a tribolelectric pair. (Dust and sand aren’t necessarily made of the same stuff, notes Lemmon, because “dust can be blown in from anywhere.”) Smaller dust particles tend to charge negative, taking away electrons from the larger sand grains.
Because the rising central column of hot air that powers the dust devil carries the negatively-charged dust upward and leaves the heavier positively-charged sand swirling near the base, the charges get separated, creating an electric field. “On Earth, with instruments we’ve measured electric fields on the order of 20 thousand volts per meter (20 kV/m),” Farrell says. That’s peanuts compared to the electric fields in terrestrial thunderstorms, where lightning doesn’t flash until electric fields get 100 times greater–enough to ionize (break apart) air molecules.
But a mere 20 kV/m “is very close to the breakdown of the thin Martian atmosphere,” Farrell points out. More significantly, Martian dust devils are so much bigger than their terrestrial counterparts that their stored electrical energy may be much higher. “How would those fields discharge?” he asks. “Would you have Martian lightning inside the dust devils?” Even if lightning wouldn’t ordinarily occur naturally, the presence of an astronaut or rover or habitat might induce filamentary discharges, or local arcing. “The thing you’d really have to watch out for is corners, where electric fields can get very strong,” he adds. “You might want to make your vehicle or habitat rounded.”
Another consideration for astronauts on Mars would be “radio static as charged grains hit bare-wire antennas,” Farrell warns. And after the dust devil passed over and was gone, a lasting souvenir of its passage would be an increased adhesion of dust to spacesuits, vehicles, and habitats via electrostatic cling–the same phenomenon that causes socks to stick together when pulled out of a clothes dryer–making cleanup difficult before reentering a habitat.
Because Martian dust devils can tower 8 to 10 kilometers high, planetary meteorologists now think the devils may be responsible for throwing so much dust high into the Martian atmosphere. Importantly for astronauts, that dust may be carrying negative charges high into the atmosphere as well. Charge building up at the storm top could pose a hazard to a rocket taking off from Mars, as happened to Apollo 12 in November 1969 when it lifted off from Florida during a thunderstorm: the rocket exhaust ionized or broke down the air molecules, leaving a trail of charged molecules all the way down to the ground, triggering a lightning bolt that struck the spacecraft.
“Early sea navigators, like Columbus, understood that their ships had to be designed for extreme weather conditions,” Farrell points out. “To design a mission to Mars, we need to know the extremes of Martian weather–and those extremes appear to be in the form of dust storms and devils.”
Original Source: NASA News Release | 0.844494 | 3.884176 |
After a 5-year interplanetary journey, which included a gravity assist from Earth, NASA’s spacecraft Juno was successfully inserted into orbit about Jupiter on July 4, 2016. Juno is NASA’s most remote spacecraft to be entirely solar-powered; its three 8.9 meter long solar panels are the largest of any on NASA’s deep-space probes. It houses 9 primary instruments enabling a close-up study of the planet’s gravitational field, its massive magnetic field and auroras, the chemical composition (including water) of its atmosphere, and providing detailed color images. During the next 20 months, Juno will slip under the planet’s intense radiation belts, approaching within 5000 km of its cloud cover, and execute approximately 40 tight orbits of period 14 days before burning up in the planet’s atmosphere. Astronomers believe that Jupiter was the first planet to form in the Solar System, and so it must have played a critical role in the formation of the remaining planets. Juno’s mission is to learn how Jupiter was formed, to help us understand how Earth came to be.
Shortly before Juno‘s orbit insertion, Dr. Philip Blanco of Grossmont College mined NASA’s press releases and other on-line tools for solid numerical data on the spacecraft’s past and planned trajectory, to make the orbit insertion maneuver a “teachable moment” for introductory physics students. Using his data, he kindly wrote a “guest post” (presented below) for use by physics instructors in their introductory mechanics classes. I edited it just a bit, but all credit for the real work belongs to Phil. We hope you will find it useful!
Eyes on Juno for Jupiter Orbit Insertion
by Philip Blanco, Grossmont College
The Juno spacecraft has reached Jupiter after an epic journey that began with launch from Cape Canaveral in August, 2011. At the end of May, 2016, when Jupiter’s gravity dominated its motion, mission planners began preparations for the Jupiter Orbit Insertion (JOI) phase of the mission. (See this melodramatic NASA video.) In this post, we’ll see how mission information provided by NASA’s Eyes on the Solar System online application can be used along with some introductory mechanics to calculate the velocity change required to put the spacecraft into its first “capture” orbit.
NASA provided some dynamical information about JOI in a Press Kit. However, non-metric units and vague statements about speed and distance appearing in the kit made it frustrating for this educator to extract “hard numbers.” (An alternate source with more details is Spaceflight 101.) Fortunately, NASA provides a much better resource for our purposes: JPL’s Eyes on the Solar System uses real mission data to simulate solar system and spacecraft motions, in the past, (predicted) present, and near-future. Eyes gets its data from SPICE format files produced by the mission teams themselves. Once downloaded (PC and Mac versions are both available), select the Advanced mode and find your favorite mission to “fly along” with. After first switching to metric units (under Visual Controls on the right of the screen), I found an option under Cool Tools that allows the user to display relative distance and speed between any two selected objects. I chose Jupiter and Juno, and noted that the distance shown in km appears to be from Jupiter’s cloud tops, not its center, so I added Jupiter’s equatorial radius to the distances displayed by the tool.
A. Juno’s Approach Energy and Speed
I used the following physical characteristics of Jupiter: , and equatorial radius (used here because the initial approach and subsequent capture orbits pass over the poles with perijove – the closest distance from Jupiter’s center – above the equator).
For simplicity I analyzed Juno‘s motion relative to Jupiter starting at noon on July 3, 2016. Although one could say that the Sun’s gravitational pull can be neglected at this point, it is more accurate to say that we can neglect the difference between Juno‘s and Jupiter’s freefall acceleration toward the Sun, i.e., we can treat the Jovian frame of reference as inertial for calculating Juno‘s subsequent motion relative to the planet.
Approximating Jupiter as a spherical body, and ignoring all other influences, Juno‘s orbital mechanical energy per unit mass ε is conserved during its unpowered approach to perijove, and is expressed as:
Juno‘s incoming speed and distance relative to Jupiter’s center on 2016 July 3.5 were and , for which . The fact that confirms that Juno was on an (unbound) hyperbolic trajectory which would continue around and away from Jupiter unless ε is corrected to a negative value consistent with a bound elliptical orbit. (Although this value of looks huge, in fact it is tiny compared to the kinetic energy per unit mass needed for escape from the Jovian surface: .)
Rearranging Eqn. 1, Juno‘s uncorrected incoming perijove speed is
NASA’s Press Kit and Eyes give different values for the perijove distance , which I derived from their stated altitudes above the Jovian cloud tops. Let’s take , or 1.06 Jupiter radii, for which Eqn. 2 yields . Compare this to the local escape speed . To enter a capture orbit, the speed must be reduced by at least 0.26 km/s.
B. Required Speed at Perijove for Capture Orbit
NASA’s Press Kit states that, after firing its main engine, Juno‘s path will be converted from an unbound hyperbolic trajectory to an elliptical “capture” orbit with period . What instantaneous change of speed (a.k.a. specific impulse) at perijove is required to achieve this new orbit?
Kepler’s 3rd law states that , where a is the orbital semi-major axis. Solving for a, we obtain , or about 57.2 Jovian radii. The orbital energy per unit mass of a body in elliptical orbit is given by (See PPE, Eqn. 10.13)
which for the values given above yields , negative for the bound orbit. Substituting and into Eqn. 2 gives the perijove speed for this orbit: , just below the local escape speed given above.
Therefore, Juno‘s required change in speed is
very close to the figure of 541 m/s stated in advance by NASA! The figure below shows the incoming hyperbolic path and the capture orbit predicted by our simple model.
Questions for students
Instructors might ask students to perform some or all of the calculations given above. Here are a few additional questions related to the Juno mission.
1. Juno‘s main engine is a British-built Leros 1b which burns a mixture of hydrazine (N2H4) and nitrogen tetroxide (N2O4). A rocket engine’s efficiency is characterized by its specific impulse , which is (different from the earlier use of this term) the ratio between the rocket thrust (see PPE, section 6.14) and the weight (on Earth) of fuel consumed per second:
where . The Leros 1b is advertised as having a nominal thrust of 635 N and a specific impulse of 317 s.
a. What is the exhaust velocity? (Ans: 3.1 km/s)
b. What mass of fuel is consumed per second ()? How much fuel was consumed in the 35 minute JOI burn? (Ans: 0.2 kg/s, 430 kg)
c. Verify that your answers are consistent with the value of calculated above.
2. Following two 53.5 day capture orbits, Juno will execute a Period Reduction Maneuver at perijove to enter its “science” orbit of period 13.965 days = 1206.6 ks. Assuming that this maneuver does not change the perijove distance, calculate the required . (Ans: 400 m/s. This answer is higher than NASA’s “published” value of 350 m/s. But the uncertainty in the perijove distance (± 200 km) propagates to an uncertainty in the perijove speed of nearly 100 m/s. Students might be asked to calculate this uncertainty.) | 0.847973 | 3.661724 |
A stellar monster lurks in heart of the Centaur.
A recent analysis of a star in the south hemisphere constellation of Centaurus has highlighted the role that amateurs play in assisting with professional discoveries in astronomy.
The find used of the European Southern Observatory’s Very Large Telescope based in the Atacama Desert in northern Chile — as well as data from observatories around the world — to reveal the nature of a massive yellow “hypergiant” star as one of the largest stars known.
The stats for the star are impressive indeed: dubbed HR 5171 A, the binary system weighs in at a combined 39 solar masses, has a radius of over 1,300 times that of our Sun, and is a million times as luminous. Located 3,600 parsecs or over 11,700 light years distant, the star is 50% larger than the famous red giant Betelgeuse. Plop HR 5171 A down into the center of our own solar system, and it would extend out over 6 astronomical units (A.U.s) past the orbit of Jupiter.
Researchers used observations going back over 60 years – some of which were collected by dedicated amateur astronomers – to pin down the nature of this curious star. A variable star just below naked eye visibility spanning a magnitude range from +6.1 to +7.3, HR 5171 A also has a relatively small companion star orbiting across our line of sight once every 1300 days. Such a system is known as an eclipsing binary. Famous examples of similar systems are the star Algol (Alpha Persei), Epsilon Aurigae and Beta Lyrae. The companion star for HR 5171 is also a large star in its own right at around six solar masses and 400 solar radii in size. The distance from center-to-center for the system is about 10 A.U.s – the distance from Sol to Saturn – and the surface-to-surface distance for the A and B components of the system are “only” about 2.8 A.U.s apart. This all means that these two massive stars are in physical contact, with the expanded outer atmosphere of the bloated primary contacting the secondary, giving the pair a distorted peanut shape.
“The companion we have found is very significant as it can have an influence on the fate of HR 5171 A, for example stripping off its outer layers and modifying its evolution,” said astronomer Olivier Chesneau of the Observatoire de la Côte d’Azur in Nice France in the recent press release.
Knowing the orbital period of a secondary star offers a method to measure the mass of the primary using good old Newtonian mechanics. Coupled with astrometry used to measure its tiny parallax, this allows astronomers to pin down HR 5171 A’s stupendous size and distance.
Along with luminous blue variables, yellow hypergiants are some of the brightest stars known, with an absolute magnitude of around -9. That’s just 16x times fainter than the apparent visual magnitude of a Full Moon but over 100 times brighter than Venus – if you placed a star like HR 5171 A 32 light years from the Earth, it would easily cast a shadow.
Astronomers used a technique known as interferormetry to study HR 5171 A, which involves linking up several telescopes to create the resolving power of one huge telescope. Researchers also culled through over a decade’s worth data to analyze the star. Though much of what had been collected by the American Association of Variable Star Observers (the AAVSO) had been considered to be too noisy for the purposes of this study, a dataset built from 2000 to 2013 by amateur astronomer Sebastian Otero was of excellent quality and provided a good verification for the VLT data.
The discovery is also crucial as researchers have come to realize that we’re catching HR 5171 A at an exceptional phase in its life. The star has been getting larger and cooling as it grows, and this change can be seen just over the past 40 year span of observations, a rarity in stellar astronomy.
“It’s not a surprise that yellow hypergiants are very instable and lose a lot of mass,” Chesneau told Universe Today. “But the discovery of a companion around such a bright star was a big surprise since any ‘normal’ star should at least be 10,000 times fainter than the hypergiant. Moreover, the hypergiant was much bigger than expected. What we see is not the companion itself, but the regions gravitationally controlled and filled by the wind from the hypergiant. This is a perfect example of the so-called Roche model. This is the first time that such a useful and important model has really been imaged. This hypergiant exemplifies a famous concept!”
Indeed, you can see just such photometric variations as the secondary orbits its host in the VLTI data collected by the AMBER interferometer, backed up by observations from GEMINI’s NICI chronograph:
The NIGHTFALL program was also used for modeling the eclipsing binary components.
These latest measurements place HR 5171 A firmly in the “Top 10” for largest stars in terms of size known, as well as the largest yellow hypergiant star known This is due mainly to tidal interactions with its companion. Only eight yellow hypergiants have been identified in our Milky Way galaxy. HR 5171 A is also in a crucial transition phase from a red hypergiant to becoming a luminous blue variable or perhaps even a Wolf-Rayet type star, and will eventually end its life as a supernova.
HR 5171 A is also known as HD 119796, HIP 67261, and V766 Centauri. Located at Right Ascension 13 Hours 47’ 11” and declination -62 degrees 35’ 23,” HR 5171 culminates just two degrees above the southern horizon at local midnight as seen from Miami in late March.
HR 5171 A is a fine binocular object for southern hemisphere observers.
But the good news is, there’s another yellow hypergiant visible for northern hemisphere observers named Rho Cassiopeiae:
Rho Cass is one of the few naked eye examples of a yellow hypergiant star, and varies from magnitude +4.1 to +6.2 over an irregular period.
It’s amusing read the Burnham’s Celestial Handbook entry on Rho Cass. He notes the lack of parallax and the spectral measurements of the day — the early 1960s — as eluding to a massive star with a “true distance… close to 3,000 light years!” Today we know that Rho Cassiopeiae actually lies farther still, at over 8,000 light years distant. Robert Burnham would’ve been impressed even more by the amazing nature of HR 5171 as revealed today by ESO astronomers! | 0.933017 | 3.957187 |
NASA launched a messenger to Mercury on Tuesday, the first spacecraft in 30 years to head to the sun's closest planet.
The probe, named Messenger, rocketed away in the pre-dawn moonlight on what will be a 5 billion-mile, 6.5-year journey to Mercury. The trip should have started a day earlier, but clouds from Tropical Storm Alex postponed liftoff.
"A voyage of mythological proportions," a flight controller announced as soon as Messenger shed its final rocket stage.
Applause erupted in launch control. "That looked wonderful," said launch director Chuck Dovale. "We bid Messenger farewell."
Scientists have been yearning to study Mercury up-close ever since Mariner 10 zoomed by three times in the mid-1970s.
If all goes well, come 2011, Messenger will be the first spacecraft to orbit Mercury.
The spacecraft cannot fly straight to Mercury; it does not carry nearly enough fuel. So it will fly once past Earth, twice past Venus and three times past Mercury for gravity assists – and make 15 loops around the sun – before slowing enough to slip into orbit around the small, hot planet.
Its seven scientific instruments will collect data for a full year in orbit around Mercury, an average 36 million miles from the sun. That's 2.5 times closer to the sun than Earth – it would be as though 11 suns were beating down on Earth.
Messenger will be blasted by up to 700-degree heat once it reaches Mercury, but its instruments will operate at room temperature, protected by a custom-built ceramic-fabric sunshade just one-quarter of an inch thick. All Mariner 10 had was a quaintly old-fashioned umbrella.
That's why, in large part, it's taken so long to return to Mercury. Scientists had to figure out how to beat the heat.
Technology and opportunity converged only recently via NASA's low-cost, planetary-science Discovery program. The entire tab for the Messenger mission, developed and run by Johns Hopkins University, is $427 million.
Mariner 10 provided "a glimpse of this planet of extremes," said Orlando Figueroa, director of NASA's solar system exploration division. Because it only flew by Mercury and did not circle the planet, Mariner 10 observed less than half the orb.
Messenger will view Mercury from all sides.
"I say we are long overdue for another visit with some permanence to help us unveil the secrets of this planet, the innermost and least understood of the terrestrial planets," Figueroa said. | 0.84117 | 3.292431 |
Abstract. The results of extensive mathematical observations of the manifestation of astrometric-geodetic parameters of the Earth and the Moon in the parameters of rectangular triangles with legs 10 and 19, 3 and 4, 81 and 100, as well as in the English system of measures of length are described. The purpose of the description is to show the unknown numerical regularities of the space-time (s-t) values of the bodies of adjacent space, reflected in the ancient system of knowledge. Analysis of the composition of the numbers of angles and sides of three triangles made it possible to detect in them a compact manifestation of the principal s-t values of the Earth and the Moon.
In the first triangle, s-t values and their ratios in simple terms correspond with one of the royal cubits (measure of length) of Ancient Egypt with base value of 0.526315789 (real meter), or the reciprocal value of the number 1.9. This cubit is considered the standard of the sarcophagi of the First and Second pyramids of Giza. S-t values appear in the triangle so that their values correlate with a series of royal cubit numbers approaching its base value, which allowed using the cubit as one of the universal measures on the Earth. Together with the number of the cubit in the triangle, the Meton number (6939.63515) is displayed, as well as in the triangle 3 : 4 : 5 this number (6939.495) is found, which represents the time cycles of the Moon and the Earth and their ratios.
The second and third triangles are included as triangles of the apothem, respectively, into the Second and Third (smaller) pyramids of Giza. In the triangle of the apothem of the Second Pyramid, a parametric model of the orbital motion of the Moon and its synodic day was found, as in the adjacent triangles of the face and edge of the Second Pyramid, parametric models of the orbital motion of the Earth and its day were previously discovered. This establishes that the parameters of the time cycles of the Earth and the Moon are geometrically related to each other by the sector of the Second Pyramid, consisting of three adjacent right-angled triangles.
In the Third Pyramid, the apothem triangle with the legs 81 and 100 with its hypotenuse represents the ancient cosmic principle of yonilinga, expressed in terms of the product of the polar radius of the Earth and its angular rate of rotation. The length of the hypotenuse, which is 83.8 real meters, seems to be used as another universal measure on Earth. In the pyramid, a wide range of numbers representing the astrometric-geodetic parameters of the Earth, related to its axial rotation, to the motion along the orbit and the precession of the axis, to the spheroid of the Earth, as well as to the rotations of the Moon (around its axis and the Earth) is also found. In the parameters of the pyramid, numbers from the English system of measures of length appear numerically, which indicates the origin of this system of measures. The geometry of the apothem triangles, as well as edges and faces of the pyramid determine a number close to the value of the modern English foot, and this number of real meters can be considered a universal earthly measure of length.
It is still too early to talk about the complete and final decoding-recognition of the geometry of the pyramids of Giza, but on the basis of the studies carried out, it can be asserted that the choice of the pyramids’ geometry is due to certain relationships and interrelations of the s-t values of, first and foremost, the Earth and the Moon, the numbers of which form a definite astronomical numerical network, and it is studies precisely in the astrometric-geodesic direction that can result in complete decoding. In a preliminary way, we can point to the possible existence of a single cosmic concept of the three pyramids, consisting in the displayed in them principle of triplicity referred to space, time and their interaction, according to the model from Nothing. On the whole, it can be argued that a single key has been found for the recognition of the geometry of the Giza pyramidal complex and, as a consequence, for the recognition of the English system of measures. This recognition can mean not only a historical value and the fact of establishing contact with the preceding civilization. Detection of series of numbers of s-t values and their manifestation in the geometry of pyramids indicates the existence of certain fundamental laws of the world order, and these triangles, representing some of the initiating principles, can be fragments of the geometry of the model from Nothing. Superseries of the numbers of s-t values are also found.
Perceptions of numbers of cosmogenic and technogenic civilizations are compared. The conclusion is drawn that in the first case the numbers are perceived more in collectivistic and qualitative aspects, and in the second case in individualistic and quantitative aspects.
Keywords: right-angled triangle, astrometric parameter, geodesic parameter, Giza pyramidal complex, English system of length measures, astronomical series of numbers, astronomical numerical network, universal astronomical number, universal space-time measure, Meton cycle, cosmic principle of yonilinga, astrogeometronumerology, model from Nothing, the fetish of numbers. | 0.832887 | 3.304702 |
|Adjectives||Saturnian //, Cronian / Kronian //|
|Aphelion||1,514.50 million km (10.1238 AU)|
|Perihelion||1,352.55 million km (9.0412 AU)|
|1,433.53 million km (9.5826 AU)|
Average orbital speed
|9.68 km/s (6.01 mi/s)|
|Known satellites||82 with formal designations; innumerable additional moonlets.|
|58,232 km (36,184 mi)[a]|
|0.687 g/cm3 (0.0248 lb/cu in)[b] (less than water)|
|35.5 km/s (22.1 mi/s)[a]|
Sidereal rotation period
| 10h 33m 38s + 1m 52s|
− 1m 19s
Equatorial rotation velocity
|9.87 km/s (6.13 mi/s; 35,500 km/h)[a]|
|26.73° (to orbit)|
North pole right ascension
|40.589°; 2h 42m 21s|
North pole declination
|−0.55 to +1.17|
|14.5″ to 20.1″ (excludes rings)|
|59.5 km (37.0 mi)|
|Composition by volume||by volume:
Saturn is the sixth planet from the Sun and the second-largest in the Solar System, after Jupiter. It is a gas giant with an average radius of about nine times that of Earth. It only has one-eighth the average density of Earth; however, with its larger volume, Saturn is over 95 times more massive. Saturn is named after the Roman god of wealth and agriculture; its astronomical symbol (♄) represents the god's sickle.
Saturn's interior is most likely composed of a core of iron–nickel and rock (silicon and oxygen compounds). Its core is surrounded by a deep layer of metallic hydrogen, an intermediate layer of liquid hydrogen and liquid helium, and finally a gaseous outer layer. Saturn has a pale yellow hue due to ammonia crystals in its upper atmosphere. An electrical current within the metallic hydrogen layer is thought to give rise to Saturn's planetary magnetic field, which is weaker than the Earth's, but has a magnetic moment 580 times that of Earth due to Saturn's larger size. Saturn's magnetic field strength is around one-twentieth of Jupiter's. The outer atmosphere is generally bland and lacking in contrast, although long-lived features can appear. Wind speeds on Saturn can reach 1,800 km/h (1,100 mph; 500 m/s), higher than on Jupiter, but not as high as those on Neptune. In January 2019, astronomers reported that a day on the planet Saturn has been determined to be 10h 33m 38s + 1m 52s
− 1m 19s , based on studies of the planet's C Ring.
The planet's most famous feature is its prominent ring system, which is composed mostly of ice particles, with a smaller amount of rocky debris and dust. At least 82 moons are known to orbit Saturn, of which 53 are officially named; this does not include the hundreds of moonlets in its rings. Titan, Saturn's largest moon, and the second-largest in the Solar System, is larger than the planet Mercury, although less massive, and is the only moon in the Solar System to have a substantial atmosphere.
Saturn is a gas giant because it is predominantly composed of hydrogen and helium. It lacks a definite surface, though it may have a solid core. Saturn's rotation causes it to have the shape of an oblate spheroid; that is, it is flattened at the poles and bulges at its equator. Its equatorial and polar radii differ by almost 10%: 60,268 km versus 54,364 km. Jupiter, Uranus, and Neptune, the other giant planets in the Solar System, are also oblate but to a lesser extent. The combination of the bulge and rotation rate means that the effective surface gravity along the equator, 8.96 m/s2, is 74% that at the poles and is lower than the surface gravity of Earth. However, the equatorial escape velocity of nearly 36 km/s is much higher than that for Earth.
Saturn is the only planet of the Solar System that is less dense than water—about 30% less. Although Saturn's core is considerably denser than water, the average specific density of the planet is 0.69 g/cm3 due to the atmosphere. Jupiter has 318 times Earth's mass, and Saturn is 95 times Earth's mass. Together, Jupiter and Saturn hold 92% of the total planetary mass in the Solar System.
Despite consisting mostly of hydrogen and helium, most of Saturn's mass is not in the gas phase, because hydrogen becomes a non-ideal liquid when the density is above 0.01 g/cm3, which is reached at a radius containing 99.9% of Saturn's mass. The temperature, pressure, and density inside Saturn all rise steadily toward the core, which causes hydrogen to be a metal in the deeper layers.
Standard planetary models suggest that the interior of Saturn is similar to that of Jupiter, having a small rocky core surrounded by hydrogen and helium, with trace amounts of various volatiles. This core is similar in composition to Earth, but is more dense. The examination of Saturn's gravitational moment, in combination with physical models of the interior, has allowed constraints to be placed on the mass of Saturn's core. In 2004, scientists estimated that the core must be 9–22 times the mass of Earth, which corresponds to a diameter of about 25,000 km. This is surrounded by a thicker liquid metallic hydrogen layer, followed by a liquid layer of helium-saturated molecular hydrogen that gradually transitions to a gas with increasing altitude. The outermost layer spans 1,000 km and consists of gas.
Saturn has a hot interior, reaching 11,700 °C at its core, and it radiates 2.5 times more energy into space than it receives from the Sun. Jupiter's thermal energy is generated by the Kelvin–Helmholtz mechanism of slow gravitational compression, but such a process alone may not be sufficient to explain heat production for Saturn, because it is less massive. An alternative or additional mechanism may be generation of heat through the "raining out" of droplets of helium deep in Saturn's interior. As the droplets descend through the lower-density hydrogen, the process releases heat by friction and leaves Saturn's outer layers depleted of helium. These descending droplets may have accumulated into a helium shell surrounding the core. Rainfalls of diamonds have been suggested to occur within Saturn, as well as in Jupiter and ice giants Uranus and Neptune.
The outer atmosphere of Saturn contains 96.3% molecular hydrogen and 3.25% helium by volume. The proportion of helium is significantly deficient compared to the abundance of this element in the Sun. The quantity of elements heavier than helium (metallicity) is not known precisely, but the proportions are assumed to match the primordial abundances from the formation of the Solar System. The total mass of these heavier elements is estimated to be 19–31 times the mass of the Earth, with a significant fraction located in Saturn's core region.
Trace amounts of ammonia, acetylene, ethane, propane, phosphine and methane have been detected in Saturn's atmosphere. The upper clouds are composed of ammonia crystals, while the lower level clouds appear to consist of either ammonium hydrosulfide (NH
4SH) or water. Ultraviolet radiation from the Sun causes methane photolysis in the upper atmosphere, leading to a series of hydrocarbon chemical reactions with the resulting products being carried downward by eddies and diffusion. This photochemical cycle is modulated by Saturn's annual seasonal cycle.
Saturn's atmosphere exhibits a banded pattern similar to Jupiter's, but Saturn's bands are much fainter and are much wider near the equator. The nomenclature used to describe these bands is the same as on Jupiter. Saturn's finer cloud patterns were not observed until the flybys of the Voyager spacecraft during the 1980s. Since then, Earth-based telescopy has improved to the point where regular observations can be made.
The composition of the clouds varies with depth and increasing pressure. In the upper cloud layers, with the temperature in the range 100–160 K and pressures extending between 0.5–2 bar, the clouds consist of ammonia ice. Water ice clouds begin at a level where the pressure is about 2.5 bar and extend down to 9.5 bar, where temperatures range from 185–270 K. Intermixed in this layer is a band of ammonium hydrosulfide ice, lying in the pressure range 3–6 bar with temperatures of 190–235 K. Finally, the lower layers, where pressures are between 10–20 bar and temperatures are 270–330 K, contains a region of water droplets with ammonia in aqueous solution.
Saturn's usually bland atmosphere occasionally exhibits long-lived ovals and other features common on Jupiter. In 1990, the Hubble Space Telescope imaged an enormous white cloud near Saturn's equator that was not present during the Voyager encounters, and in 1994 another smaller storm was observed. The 1990 storm was an example of a Great White Spot, a unique but short-lived phenomenon that occurs once every Saturnian year, roughly every 30 Earth years, around the time of the northern hemisphere's summer solstice. Previous Great White Spots were observed in 1876, 1903, 1933 and 1960, with the 1933 storm being the most famous. If the periodicity is maintained, another storm will occur in about 2020.
The winds on Saturn are the second fastest among the Solar System's planets, after Neptune's. Voyager data indicate peak easterly winds of 500 m/s (1,800 km/h). In images from the Cassini spacecraft during 2007, Saturn's northern hemisphere displayed a bright blue hue, similar to Uranus. The color was most likely caused by Rayleigh scattering. Thermography has shown that Saturn's south pole has a warm polar vortex, the only known example of such a phenomenon in the Solar System. Whereas temperatures on Saturn are normally −185 °C, temperatures on the vortex often reach as high as −122 °C, suspected to be the warmest spot on Saturn.
A persisting hexagonal wave pattern around the north polar vortex in the atmosphere at about 78°N was first noted in the Voyager images. The sides of the hexagon are each about 13,800 km (8,600 mi) long, which is longer than the diameter of the Earth. The entire structure rotates with a period of 10h 39m 24s (the same period as that of the planet's radio emissions) which is assumed to be equal to the period of rotation of Saturn's interior. The hexagonal feature does not shift in longitude like the other clouds in the visible atmosphere. The pattern's origin is a matter of much speculation. Most scientists think it is a standing wave pattern in the atmosphere. Polygonal shapes have been replicated in the laboratory through differential rotation of fluids.
HST imaging of the south polar region indicates the presence of a jet stream, but no strong polar vortex nor any hexagonal standing wave. NASA reported in November 2006 that Cassini had observed a "hurricane-like" storm locked to the south pole that had a clearly defined eyewall. Eyewall clouds had not previously been seen on any planet other than Earth. For example, images from the Galileo spacecraft did not show an eyewall in the Great Red Spot of Jupiter.
Cassini observed a series of cloud features nicknamed "String of Pearls" found in northern latitudes. These features are cloud clearings that reside in deeper cloud layers.
Saturn has an intrinsic magnetic field that has a simple, symmetric shape – a magnetic dipole. Its strength at the equator – 0.2 gauss (20 µT) – is approximately one twentieth of that of the field around Jupiter and slightly weaker than Earth's magnetic field. As a result, Saturn's magnetosphere is much smaller than Jupiter's. When Voyager 2 entered the magnetosphere, the solar wind pressure was high and the magnetosphere extended only 19 Saturn radii, or 1.1 million km (712,000 mi), although it enlarged within several hours, and remained so for about three days. Most probably, the magnetic field is generated similarly to that of Jupiter – by currents in the liquid metallic-hydrogen layer called a metallic-hydrogen dynamo. This magnetosphere is efficient at deflecting the solar wind particles from the Sun. The moon Titan orbits within the outer part of Saturn's magnetosphere and contributes plasma from the ionized particles in Titan's outer atmosphere. Saturn's magnetosphere, like Earth's, produces aurorae.
The average distance between Saturn and the Sun is over 1.4 billion kilometers (9 AU). With an average orbital speed of 9.68 km/s, it takes Saturn 10,759 Earth days (or about 29 1⁄2 years) to finish one revolution around the Sun. As a consequence, it forms a near 5:2 mean-motion resonance with Jupiter. The elliptical orbit of Saturn is inclined 2.48° relative to the orbital plane of the Earth. The perihelion and aphelion distances are, respectively, 9.195 and 9.957 AU, on average. The visible features on Saturn rotate at different rates depending on latitude and multiple rotation periods have been assigned to various regions (as in Jupiter's case).
Astronomers use three different systems for specifying the rotation rate of Saturn. System I has a period of 10 hr 14 min 00 sec (844.3°/d) and encompasses the Equatorial Zone, the South Equatorial Belt and the North Equatorial Belt. The polar regions are considered to have rotation rates similar to System I. All other Saturnian latitudes, excluding the north and south polar regions, are indicated as System II and have been assigned a rotation period of 10 hr 38 min 25.4 sec (810.76°/d). System III refers to Saturn's internal rotation rate. Based on radio emissions from the planet detected by Voyager 1 and Voyager 2, System III has a rotation period of 10 hr 39 min 22.4 sec (810.8°/d). System III has largely superseded System II.
A precise value for the rotation period of the interior remains elusive. While approaching Saturn in 2004, Cassini found that the radio rotation period of Saturn had increased appreciably, to approximately 10 hr 45 min 45 sec (± 36 sec). The latest estimate of Saturn's rotation (as an indicated rotation rate for Saturn as a whole) based on a compilation of various measurements from the Cassini, Voyager and Pioneer probes was reported in September 2007 is 10 hr 32 min 35 sec.
In March 2007, it was found that the variation of radio emissions from the planet did not match Saturn's rotation rate. This variance may be caused by geyser activity on Saturn's moon Enceladus. The water vapor emitted into Saturn's orbit by this activity becomes charged and creates a drag upon Saturn's magnetic field, slowing its rotation slightly relative to the rotation of the planet.
An apparent oddity for Saturn is that it does not have any known trojan asteroids. These are minor planets that orbit the Sun at the stable Lagrangian points, designated L4 and L5, located at 60° angles to the planet along its orbit. Trojan asteroids have been discovered for Mars, Jupiter, Uranus, and Neptune. Orbital resonance mechanisms, including secular resonance, are believed to be the cause of the missing Saturnian trojans.
Saturn has 82 known moons, 53 of which have formal names. In addition, there is evidence of dozens to hundreds of moonlets with diameters of 40–500 meters in Saturn's rings, which are not considered to be true moons. Titan, the largest moon, comprises more than 90% of the mass in orbit around Saturn, including the rings. Saturn's second-largest moon, Rhea, may have a tenuous ring system of its own, along with a tenuous atmosphere.
Many of the other moons are small: 34 are less than 10 km in diameter and another 14 between 10 and 50 km in diameter. Traditionally, most of Saturn's moons have been named after Titans of Greek mythology. Titan is the only satellite in the Solar System with a major atmosphere, in which a complex organic chemistry occurs. It is the only satellite with hydrocarbon lakes.
On 6 June 2013, scientists at the IAA-CSIC reported the detection of polycyclic aromatic hydrocarbons in the upper atmosphere of Titan, a possible precursor for life. On 23 June 2014, NASA claimed to have strong evidence that nitrogen in the atmosphere of Titan came from materials in the Oort cloud, associated with comets, and not from the materials that formed Saturn in earlier times.
Saturn's moon Enceladus, which seems similar in chemical makeup to comets, has often been regarded as a potential habitat for microbial life. Evidence of this possibility includes the satellite's salt-rich particles having an "ocean-like" composition that indicates most of Enceladus's expelled ice comes from the evaporation of liquid salt water. A 2015 flyby by Cassini through a plume on Enceladus found most of the ingredients to sustain life forms that live by methanogenesis.
Saturn is probably best known for the system of planetary rings that makes it visually unique. The rings extend from 6,630 to 120,700 kilometers (4,120 to 75,000 mi) outward from Saturn's equator and average approximately 20 meters (66 ft) in thickness. They are composed predominantly of water ice with trace amounts of tholin impurities, and a peppered coating of approximately 7% amorphous carbon. The particles that make up the rings range in size from specks of dust up to 10 m. While the other gas giants also have ring systems, Saturn's is the largest and most visible.
There are two main hypotheses regarding the origin of the rings. One hypothesis is that the rings are remnants of a destroyed moon of Saturn. The second hypothesis is that the rings are left over from the original nebular material from which Saturn was formed. Some ice in the E ring comes from the moon Enceladus's geysers. The water abundance of the rings varies radially, with the outermost ring A being the most pure in ice water. This abundance variance may be explained by meteor bombardment.
Beyond the main rings at a distance of 12 million km from the planet is the sparse Phoebe ring, which is tilted at an angle of 27° to the other rings and, like Phoebe, orbits in retrograde fashion.
Some of the moons of Saturn, including Pandora and Prometheus, act as shepherd moons to confine the rings and prevent them from spreading out. Pan and Atlas cause weak, linear density waves in Saturn's rings that have yielded more reliable calculations of their masses.
The observation and exploration of Saturn can be divided into three main phases. The first era was ancient observations (such as with the naked eye), before the invention of the modern telescopes. Starting in the 17th century, progressively more advanced telescopic observations from Earth have been made. The third phase is visitation by space probes, by either orbiting or flyby. In the 21st century, observations continue from Earth (including Earth-orbiting observatories like the Hubble Space Telescope) and, until its 2017 retirement, from the Cassini orbiter around Saturn.
Saturn has been known since prehistoric times and in early recorded history it was a major character in various mythologies. Babylonian astronomers systematically observed and recorded the movements of Saturn. In ancient Greek, the planet was known as Φαίνων Phainon, and in Roman times it was known as the "star of Saturn". In ancient Roman mythology, the planet Phainon was sacred to this agricultural god, from which the planet takes its modern name. The Romans considered the god Saturnus the equivalent of the Greek god Cronus; in modern Greek, the planet retains the name Cronus—Κρόνος: Kronos.)
The Greek scientist Ptolemy based his calculations of Saturn's orbit on observations he made while it was in opposition. In Hindu astrology, there are nine astrological objects, known as Navagrahas. Saturn is known as "Shani" and judges everyone based on the good and bad deeds performed in life. Ancient Chinese and Japanese culture designated the planet Saturn as the "earth star" (土星). This was based on Five Elements which were traditionally used to classify natural elements.
In ancient Hebrew, Saturn is called 'Shabbathai'. Its angel is Cassiel. Its intelligence or beneficial spirit is 'Agȋȇl (Hebrew: אגיאל, romanized: ʿAgyal), and its darker spirit (demon) is Zȃzȇl (Hebrew: זאזל, romanized: Zazl). Zazel has been described as a great angel, invoked in Solomonic magic, who is "effective in love conjurations". In Ottoman Turkish, Urdu and Malay, the name of Zazel is 'Zuhal', derived from the Arabic language (Arabic: زحل, romanized: Zuhal).
Saturn's rings require at least a 15-mm-diameter telescope to resolve and thus were not known to exist until Christiaan Huygens saw them in 1659. Galileo, with his primitive telescope in 1610, incorrectly thought of Saturn's appearing not quite round as two moons on Saturn's sides. It was not until Huygens used greater telescopic magnification that this notion was refuted, and the rings were truly seen for the first time. Huygens also discovered Saturn's moon Titan; Giovanni Domenico Cassini later discovered four other moons: Iapetus, Rhea, Tethys and Dione. In 1675, Cassini discovered the gap now known as the Cassini Division.
No further discoveries of significance were made until 1789 when William Herschel discovered two further moons, Mimas and Enceladus. The irregularly shaped satellite Hyperion, which has a resonance with Titan, was discovered in 1848 by a British team.
In 1899 William Henry Pickering discovered Phoebe, a highly irregular satellite that does not rotate synchronously with Saturn as the larger moons do. Phoebe was the first such satellite found and it takes more than a year to orbit Saturn in a retrograde orbit. During the early 20th century, research on Titan led to the confirmation in 1944 that it had a thick atmosphere – a feature unique among the Solar System's moons.
Pioneer 11 made the first flyby of Saturn in September 1979, when it passed within 20,000 km of the planet's cloud tops. Images were taken of the planet and a few of its moons, although their resolution was too low to discern surface detail. The spacecraft also studied Saturn's rings, revealing the thin F-ring and the fact that dark gaps in the rings are bright when viewed at high phase angle (towards the Sun), meaning that they contain fine light-scattering material. In addition, Pioneer 11 measured the temperature of Titan.
In November 1980, the Voyager 1 probe visited the Saturn system. It sent back the first high-resolution images of the planet, its rings and satellites. Surface features of various moons were seen for the first time. Voyager 1 performed a close flyby of Titan, increasing knowledge of the atmosphere of the moon. It proved that Titan's atmosphere is impenetrable in visible wavelengths; therefore no surface details were seen. The flyby changed the spacecraft's trajectory out from the plane of the Solar System.
Almost a year later, in August 1981, Voyager 2 continued the study of the Saturn system. More close-up images of Saturn's moons were acquired, as well as evidence of changes in the atmosphere and the rings. Unfortunately, during the flyby, the probe's turnable camera platform stuck for a couple of days and some planned imaging was lost. Saturn's gravity was used to direct the spacecraft's trajectory towards Uranus.
The probes discovered and confirmed several new satellites orbiting near or within the planet's rings, as well as the small Maxwell Gap (a gap within the C Ring) and Keeler gap (a 42 km wide gap in the A Ring).
The Cassini–Huygens space probe entered orbit around Saturn on 1 July 2004. In June 2004, it conducted a close flyby of Phoebe, sending back high-resolution images and data. Cassini's flyby of Saturn's largest moon, Titan, captured radar images of large lakes and their coastlines with numerous islands and mountains. The orbiter completed two Titan flybys before releasing the Huygens probe on 25 December 2004. Huygens descended onto the surface of Titan on 14 January 2005.
Starting in early 2005, scientists used Cassini to track lightning on Saturn. The power of the lightning is approximately 1,000 times that of lightning on Earth.
In 2006, NASA reported that Cassini had found evidence of liquid water reservoirs no more than tens of meters below the surface that erupt in geysers on Saturn's moon Enceladus. These jets of icy particles are emitted into orbit around Saturn from vents in the moon's south polar region. Over 100 geysers have been identified on Enceladus. In May 2011, NASA scientists reported that Enceladus "is emerging as the most habitable spot beyond Earth in the Solar System for life as we know it".
Cassini photographs have revealed a previously undiscovered planetary ring, outside the brighter main rings of Saturn and inside the G and E rings. The source of this ring is hypothesized to be the crashing of a meteoroid off Janus and Epimetheus. In July 2006, images were returned of hydrocarbon lakes near Titan's north pole, the presence of which were confirmed in January 2007. In March 2007, hydrocarbon seas were found near the North pole, the largest of which is almost the size of the Caspian Sea. In October 2006, the probe detected an 8,000 km diameter cyclone-like storm with an eyewall at Saturn's south pole.
From 2004 to 2 November 2009, the probe discovered and confirmed eight new satellites. In April 2013 Cassini sent back images of a hurricane at the planet's north pole 20 times larger than those found on Earth, with winds faster than 530 km/h (330 mph). On 15 September 2017, the Cassini-Huygens spacecraft performed the "Grand Finale" of its mission: a number of passes through gaps between Saturn and Saturn's inner rings. The atmospheric entry of Cassini ended the mission.
The continued exploration of Saturn is still considered to be a viable option for NASA as part of their ongoing New Frontiers program of missions. NASA previously requested for plans to be put forward for a mission to Saturn that included an atmospheric entry probe and possible investigations into the habitability and possible discovery of life on Saturn's moons Titan and Enceladus.
Saturn is the most distant of the five planets easily visible to the naked eye from Earth, the other four being Mercury, Venus, Mars and Jupiter. (Uranus and occasionally 4 Vesta are visible to the naked eye in dark skies.) Saturn appears to the naked eye in the night sky as a bright, yellowish point of light. The mean apparent magnitude of Saturn is 0.46 with a standard deviation of 0.34. Most of the magnitude variation is due to the inclination of the ring system relative to the Sun and Earth. The brightest magnitude, −0.55, occurs near in time to when the plane of the rings is inclined most highly, and the faintest magnitude, 1.17, occurs around the time when they are least inclined. It takes approximately 29.5 years for the planet to complete an entire circuit of the ecliptic against the background constellations of the zodiac. Most people will require an optical aid (very large binoculars or a small telescope) that magnifies at least 30 times to achieve an image of Saturn's rings, in which clear resolution is present. When Earth passes through the ring plane, which occurs twice every Saturnian year (roughly every 15 Earth years), the rings briefly disappear from view because they are so thin. Such a "disappearance" will next occur in 2025, but Saturn will be too close to the Sun for observations.
Saturn and its rings are best seen when the planet is at, or near, opposition, the configuration of a planet when it is at an elongation of 180°, and thus appears opposite the Sun in the sky. A Saturnian opposition occurs every year—approximately every 378 days—and results in the planet appearing at its brightest. Both the Earth and Saturn orbit the Sun on eccentric orbits, which means their distances from the Sun vary over time, and therefore so do their distances from each other, hence varying the brightness of Saturn from one opposition to the next. Saturn also appears brighter when the rings are angled such that they are more visible. For example, during the opposition of 17 December 2002, Saturn appeared at its brightest due to a favorable orientation of its rings relative to the Earth, even though Saturn was closer to the Earth and Sun in late 2003.
From time to time Saturn is occulted by the Moon (that is, the Moon covers up Saturn in the sky). As with all the planets in the Solar System, occultations of Saturn occur in "seasons". Saturnian occultations will take place monthly for about a 12-month period, followed by about a five-year period in which no such activity is registered. The Moon's orbit is inclined by several degrees relative to Saturn's, so occultations will only occur when Saturn is near one of the points in the sky where the two planes intersect (both the length of Saturn's year and the 18.6-Earth year nodal precession period of the Moon's orbit influence the periodicity).
The Greek name of the planet Saturn is Kronos. The Titan Cronus was the father of Zeus, while Saturn was the Roman God of agriculture.See also the Greek article about the planet.
Latin: Angel summoned for love invocations
a Solomonic angel of love rituals | 0.897729 | 3.298246 |
If you lived on one of Pluto’s moons, you might have a hard time determining when, or from which direction, the sun will rise each day. Comprehensive analysis of data from NASA’s Hubble Space Telescope shows that two of Pluto’s moons, Nix and Hydra, wobble unpredictably.
“Hubble has provided a new view of Pluto and its moons revealing a cosmic dance with a chaotic rhythm,” said John Grunsfeld, associate administrator of NASA’s Science Mission Directorate in Washington. “When the New Horizons spacecraft flies through the Pluto system in July we’ll get a chance to see what these moons look like up close and personal.”
The moons wobble because they’re embedded in a gravitational field that shifts constantly. This shift is created by the double planet system of Pluto and Charon as they whirl about each other. Pluto and Charon are called a double planet because they share a common center of gravity located in the space between the bodies. Their variable gravitational field sends the smaller moons tumbling erratically. The effect is strengthened by the football-like, rather than spherical, shape of the moons. Scientists believe it’s likely Pluto’s other two moons, Kerberos and Styx, are in a similar situation.
The astonishing results, found by Mark Showalter of the SETI Institute in Mountain View, California and Doug Hamilton of the University of Maryland at College Park, will appear in the June 4 issue of the journal Nature.
Showalter also found three of Pluto’s moons are presently locked together in resonance, meaning there is a precise ratio for their orbital periods. “If you were sitting on Nix, you would see that Styx orbits Pluto twice for every three orbits made by Hydra,” noted Hamilton. | 0.881172 | 3.447093 |
By the end of this section, you will be able to:
- Provide an overview of the composition of the giant planets
- Chronicle the robotic exploration of the outer solar system
- Summarize the missions sent to orbit the gas giants
The giant planets hold most of the mass in our planetary system. Jupiter alone exceeds the mass of all the other planets combined (Figure 1). The material available to build these planets can be divided into three classes by what they are made of: “gases,” “ices,” and “rocks” (see Table 1). The “gases” are primarily hydrogen and helium, the most abundant elements in the universe. The way it is used here, the term “ices” refers to composition only and not whether a substance is actually in a solid state. “Ices” means compounds that form from the next most abundant elements: oxygen, carbon, and nitrogen. Common ices are water, methane, and ammonia, but ices may also include carbon monoxide, carbon dioxide, and others. “Rocks” are even less abundant than ices, and include everything else: magnesium, silicon, iron, and so on.
|Table 1. Abundances in the Outer Solar System|
|Type of Material||Name||Approximate % (by Mass)|
|Rock||Magnesium (Mg), iron (Fe), silicon (Si)||0.3|
In the outer solar system, gases dominate the two largest planets, Jupiter and Saturn, hence their nickname “gas giants.” Uranus and Neptune are called “ice giants” because their interiors contain far more of the “ice” component than their larger cousins. The chemistry for all four giant planet atmospheres is dominated by hydrogen. This hydrogen caused the chemistry of the outer solar system to become reducing, meaning that other elements tend to combine with hydrogen first. In the early solar system, most of the oxygen combined with hydrogen to make H2O and was thus unavailable to form the kinds of oxidized compounds with other elements that are more familiar to us in the inner solar system (such as CO2). As a result, the compounds detected in the atmosphere of the giant planets are mostly hydrogen-based gases such as methane (CH4) and ammonia (NH3), or more complex hydrocarbons (combinations of hydrogen and carbon) such as ethane (C2H6) and acetylene (C2H2).
Exploration of the Outer Solar System So Far
Eight spacecraft, seven from the United States and one from Europe, have penetrated beyond the asteroid belt into the realm of the giants. Table 2 summarizes the spacecraft missions to the outer solar system.
|Table 2. Missions to the Giant Planets|
|Jupiter||Pioneer 10||December 1973||Flyby|
|Pioneer 11||December 1974||Flyby|
|Voyager 1||March 1979||Flyby|
|Voyager 2||July 1979||Flyby|
|Ulysses||February 1992||Flyby during gravity assist|
|Galileo||December 1995||Orbiter and probe|
|New Horizons||February 2007||Flyby during gravity assist|
|Saturn||Pioneer 11||September 1979||Flyby|
|Voyager 1||November 1980||Flyby|
|Voyager 2||August 1981||Flyby|
|Cassini||July 2004 (Saturn orbit injection 2000)||Orbiter|
|Uranus||Voyager 2||January 1986||Flyby|
|Neptune||Voyager 2||August 1989||Flyby|
The challenges of exploring so far away from Earth are considerable. Flight times to the giant planets are measured in years to decades, rather than the months required to reach Venus or Mars. Even at the speed of light, messages take hours to pass between Earth and the spacecraft. If a problem develops near Saturn, for example, a wait of hours for the alarm to reach Earth and for instructions to be routed back to the spacecraft could spell disaster. Spacecraft to the outer solar system must therefore be highly reliable and capable of a greater degree of independence and autonomy. Outer solar system missions also must carry their own power sources since the Sun is too far away to provide enough energy. Heaters are required to keep instruments at proper operating temperatures, and spacecraft must have radio transmitters powerful enough to send their data to receivers on distant Earth.
The first spacecraft to investigate the regions past Mars were the NASA Pioneers 10 and 11, launched in 1972 and 1973 as pathfinders to Jupiter. One of their main objectives was simply to determine whether a spacecraft could actually navigate through the belt of asteroids that lies beyond Mars without getting destroyed by collisions with asteroidal dust. Another objective was to measure the radiation hazards in the magnetosphere (or zone of magnetic influence) of Jupiter. Both spacecraft passed through the asteroid belt without incident, but the energetic particles in Jupiter’s magnetic field nearly wiped out their electronics, providing information necessary for the safe design of subsequent missions.
Pioneer 10 flew past Jupiter in 1973, after which it sped outward toward the limits of the solar system. Pioneer 11 undertook a more ambitious program, using the gravity of Jupiter to aim for Saturn, which it reached in 1979. The twin Voyager spacecraft launched the next wave of outer planet exploration in 1977. Voyagers 1 and 2 each carried 11 scientific instruments, including cameras and spectrometers, as well as devices to measure the characteristics of planetary magnetospheres. Since they kept going outward after their planetary encounters, these are now the most distant spacecraft ever launched by humanity.
Voyager 1 reached Jupiter in 1979 and used a gravity assist from that planet to take it on to Saturn in 1980. Voyager 2 arrived at Jupiter four months later, but then followed a different path to visit all the outer planets, reaching Saturn in 1981, Uranus in 1986, and Neptune in 1989. This trajectory was made possible by the approximate alignment of the four giant planets on the same side of the Sun. About once every 175 years, these planets are in such a position, and it allows a single spacecraft to visit them all by using gravity-assisted flybys to adjust course for each subsequent encounter; such a maneuver has been nicknamed a “Grand Tour” by astronomers.
Engineering and Space Science: Teaching an Old Spacecraft New Tricks
By the time Voyager 2 arrived at Neptune in 1989, 12 years after its launch, the spacecraft was beginning to show signs of old age. The arm on which the camera and other instruments were located was “arthritic”: it could no longer move easily in all directions. The communications system was “hard of hearing”: part of its radio receiver had stopped working. The “brains” had significant “memory loss”: some of the onboard computer memory had failed. And the whole spacecraft was beginning to run out of energy: its generators had begun showing serious signs of wear.
To make things even more of a challenge, Voyager’s mission at Neptune was in many ways the most difficult of all four flybys. For example, since sunlight at Neptune is 900 times weaker than at Earth, the onboard camera had to take much longer exposures in this light-starved environment. This was a nontrivial requirement, given that the spacecraft was hurtling by Neptune at ten times the speed of a rifle bullet.
The solution was to swivel the camera backward at exactly the rate that would compensate for the forward motion of the spacecraft. Engineers had to preprogram the ship’s computer to execute an incredibly complex series of maneuvers for each image. The beautiful Voyager images of Neptune are a testament to the ingenuity of spacecraft engineers.
The sheer distance of the craft from its controllers on Earth was yet another challenge. Voyager 2 received instructions and sent back its data via on-board radio transmitter. The distance from Earth to Neptune is about 4.8 billion kilometers. Over this vast distance, the power that reached us from Voyager 2 at Neptune was approximately10–16 watts, or 20 billion times less power than it takes to operate a digital watch. Thirty-eight different antennas on four continents were used by NASA to collect the faint signals from the spacecraft and decode the precious information about Neptune that they contained.
Enter the Orbiters: Galileo and Cassini
The Pioneer and Voyager missions were flybys of the giant planets: they each produced only quick looks before the spacecraft sped onward. For more detailed studies of these worlds, we require spacecraft that can go into orbit around a planet. For Jupiter and Saturn, these orbiters were the Galileo and Cassini spacecraft, respectively. To date, no orbiter missions have been started for Uranus and Neptune, although planetary scientists have expressed keen interest.
The Galileo spacecraft was launched toward Jupiter in 1989 and arrived in 1995. Galileo began its investigations by deploying an entry probe into Jupiter, for the first direct studies of the planet’s outer atmospheric layers.
The probe plunged at a shallow angle into Jupiter’s atmosphere, traveling at a speed of 50 kilometers per second—that’s fast enough to fly from New York to San Francisco in 100 seconds! This was the highest speed at which any probe has so far entered the atmosphere of a planet, and it put great demands on the heat shield protecting it. The high entry speed was a result of acceleration by the strong gravitational attraction of Jupiter.
Atmospheric friction slowed the probe within 2 minutes, producing temperatures at the front of its heat shield as high as 15,000 °C. As the probe’s speed dropped to 2500 kilometers per hour, the remains of the glowing heat shield were jettisoned, and a parachute was deployed to lower the instrumented probe spacecraft more gently into the atmosphere (Figure 2). The data from the probe instruments were relayed to Earth via the main Galileo spacecraft.
The probe continued to operate for an hour, descending 200 kilometers into the atmosphere. A few minutes later the polyester parachute melted, and within a few hours the main aluminum and titanium structure of the probe vaporized to become a part of Jupiter itself. About 2 hours after receipt of the final probe data, the main spacecraft fired its retro-rockets so it could be captured into orbit around the planet, where its primary objectives were to study Jupiter’s large and often puzzling moons.
The Cassini mission to Saturn (Figure 3), a cooperative venture between NASA and the European Space Agency, was similar to Galileo in its two-fold approach. Launched in 1997, Cassini arrived in 2004 and went into orbit around Saturn, beginning extensive studies of its rings and moons, as well as the planet itself. In January 2005, Cassini deployed an entry probe into the atmosphere of Saturn’s large moon, Titan, where it successfully landed on the surface. (We’ll discuss the probe and what it found in the chapter on Rings, Moons, and Pluto.)
Key Concepts and Summary
The outer solar system contains the four giant planets: Jupiter, Saturn, Uranus, and Neptune. The gas giants Jupiter and Saturn have overall compositions similar to that of the Sun. These planets have been explored by the Pioneer, Voyager, Galileo, and Cassini spacecraft. Voyager 2, perhaps the most successful of all space-science missions, explored Jupiter (1979), Saturn (1981), Uranus (1986), and Neptune (1989)—a grand tour of the giant planets—and these flybys have been the only explorations to date of the ice giants Uranus and Neptune. The Galileo and Cassini missions were long-lived orbiters, and each also deployed an entry probe, one into Jupiter and one into Saturn’s moon Titan.
- Both the Ulysses and the New Horizons spacecraft (designed to study the Sun and Pluto, respectively) flew past Jupiter for a gravity boost (gaining energy by “stealing” a little bit from the giant planet’s rotation). ↵ | 0.862049 | 4.004269 |
Theory of relativity
The theory of relativity, or simply relativity in physics, usually encompasses two interrelated theories by Albert Einstein: special relativity and general relativity. Special relativity applies to elementary particles and their interactions, describing all their physical phenomena except gravity. General relativity explains the law of gravitation and its relation to other forces of nature. It applies to the cosmological and astrophysical realm, including astronomy.
The theory transformed theoretical physics and astronomy during the 20th century, superseding a 200-year-old theory of mechanics created primarily by Isaac Newton. It introduced concepts including spacetime as a unified entity of space and time, relativity of simultaneity, kinematic and gravitational time dilation, and length contraction.
- [T]he program which Immanuel Kant proposed back in the 1760s... was this: our knowledge of the outside world depends on our modes of perception... Unfortunately, a great revolution took place in or about the year 1768, when he read a paper by Euler which intended to show that space was indeed absolute as Newton had suggested and not relative as Leibnitz suggested. (...in the eighteenth century the question of whether Newton's... or Leibnitz's view of the world was right profoundly affected all philosophy.) After reading Euler's argument... Kant... for the first time proposed that... we must be conscious of [absolute space] a priori. ...Kant died in 1804, long before new ideas about space... had been published... And since one of the things that happened in [our] lifetime has been the substitution of... a Leibnitz universe, the universe of relativity, for Newton's universe... we should think that out again.
- Jacob Bronowski, The Origins of Knowledge and Imagination (1978)
- Riemann has shewn that as there are different kinds of lines and surfaces, so there are different kinds of space of three dimensions; and that we can only find out by experience to which of these kinds the space in which we live belongs. In particular, the axioms of plane geometry are true within the limits of experiment on the surface of a sheet of paper, and yet we know that the sheet is really covered with a number of small ridges and furrows, upon which (the total curvature not being zero) these axioms are not true. Similarly, he says although the axioms of solid geometry are true within the limits of experiment for finite portions of our space, yet we have no reason to conclude that they are true for very small portions; and if any help can be got thereby for the explanation of physical phenomena, we may have reason to conclude that they are not true for very small portions of space.
- I hold in fact
(1) That small portions of space are in fact of a nature analogous to little hills on a surface which is on the average flat; namely, that the ordinary laws of geometry are not valid in them.
(2) That this property of being curved or distorted is continually being passed on from one portion of space to another after the manner of a wave.
(3) That this variation of the curvature of space is what really happens in that phenomenon which we call the motion of matter, whether ponderable or etherial.
(4) That in the physical world nothing else takes place but this variation, subject possibly to the law of continuity.
- William Kingdon Clifford, "On the Space-Theory of Matter," Abstract (read Feb 21, 1870) from the Cambridge Philosophical Society's Proceedings II (1876) pp. 157-158
- No mathematician can give any meaning to the language about matter, force, inertia used in current text-books of mechanics.
- We may... be treating merely as physical variations effects which are really due to changes in the curvature of our space; whether, in fact, some or all of those causes which we term physical may not be due to the geometrical construction of our space. There are three kinds of variation in the curvature of our space which we ought to consider as within the range of possibility.
(i) Our space is perhaps really possessed of a curvature varying from point to point, which we fail to appreciate because we are acquainted with only a small portion of space, or because we disguise its small variations under changes in our physical condition which we do not connect with our change of position. The mind that could recognise this varying curvature might be assumed to know the absolute position of a point. For such a mind the postulate of the relativity of position would cease to have a meaning. It does not seem so hard to conceive such a state of mind as the late Professor Clerk-Maxwell would have had us believe. It would be one capable of distinguishing those so-called physical changes which are really geometrical or due to a change of position in space.
(ii) Our space may be really same (of equal curvature), but its degree of curvature may change as a whole with the time. In this way our geometry based on the sameness of space would still hold good for all parts of space, but the change of curvature might produce in space a succession of apparent physical changes.
(iii) We may conceive our space to have everywhere a nearly uniform curvature, but that slight variations of the curvature may occur from point to point, and themselves vary with the time. These variations of the curvature with the time may produce effects which we not unnaturally attribute to physical causes independent of the geometry of our space. We might even go so far as to assign to this variation of the curvature of space 'what really happens in that phenomenon which we term the motion of matter.'
- The modern theory of relativity, on its mathematical side, is merely an elaboration of Riemann's analysis.
- Julian Lowell Coolidge, A History of Geometrical Methods (1940)
- It is the reciprocity of these appearances—that each party should think the other has contracted—that is so difficult to realise. Here is a paradox beyond even the imagination of Dean Swift. Gulliver regarded the Lilliputians as a race of dwarfs; and the Lilliputians regarded Gulliver as a giant. That is natural. If the Lilliputians had appeared dwarfs to Gulliver, and Gulliver had appeared a dwarf to the Lilliputians—but no! that is too absurd for fiction, and is an idea only to be found in the sober pages of science. ...It is not only in space but in time that these strange variations occur. If we observed the aviator carefully we should infer that he was unusually slow in his movements; and events in the conveyance moving with him would be similarly retarded—as though time had forgotten to go on. His cigar lasts twice as long as one of ours. ...But here again reciprocity comes in, because in the aviator's opinion it is we who are travelling at 161,000 miles a second past him; and when he has made all allowances, he finds that it is we who are sluggish. Our cigar lasts twice as long as his.
- ...The present revolution of scientific thought follows in natural sequence on the great revolutions at earlier epochs in the history of science. Einstein's special theory of relativity, which explains the indeterminateness of the frame of space and time, crowns the work of Copernicus who first led us to give up our insistence on a geocentric outlook on nature; Einstein's general theory of relativity, which reveals the curvature or non-Euclidean geometry of space and time, carries forward the rudimentary thought of those earlier astronomers who first contemplated the possibility that their existence lay on something which was not flat. These earlier revolutions are still a source of perplexity in childhood, which we soon outgrow; and a time will come when Einstein's amazing revelations have likewise sunk into the commonplaces of educated thought.
- If you don't take my words too seriously, I would say this: If we assume that all matter would disappear from the world, then, before relativity, one believed that space and time would continue existing in an empty world. But, according to the theory of relativity, if matter and its motion disappeared there would no longer be any space or time.
- Another topic deserving discussion is Einstein’s modification of Newton’s law of gravitation. In spite of all the excitement it created, Newton’s law of gravitation is not correct! It was modified by Einstein to take into account the theory of relativity. According to Newton, the gravitational effect is instantaneous, that is, if we were to move a mass, we would at once feel a new force because of the new position of that mass; by such means we could send signals at infinite speed. Einstein advanced arguments which suggest that we cannot send signals faster than the speed of light, so the law of gravitation must be wrong. By correcting it to take the delays into account, we have a new law, called Einstein’s law of gravitation. One feature of this new law which is quite easy to understand is this: In the Einstein relativity theory, anything which has energy has mass—mass in the sense that it is attracted gravitationally. Even light, which has an energy, has a “mass.” When a light beam, which has energy in it, comes past the sun there is an attraction on it by the sun. Thus the light does not go straight, but is deflected. During the eclipse of the sun, for example, the stars which are around the sun should appear displaced from where they would be if the sun were not there, and this has been observed.
For over 200 years the equations of motion enunciated by Newton were believed to describe nature correctly, and the first time that an error in these laws was discovered, the way to correct it was also discovered. Both the error and its correction were discovered by Einstein in 1905.
Newton’s Second Law, which we have expressed by the equation : was stated with the tacit assumption that m is a constant, but we now know that this is not true, and that the mass of a body increases with velocity. In Einstein’s corrected formula m has the value : where the “rest mass” m0 represents the mass of a body that is not moving and c is the speed of light, which is about 3×105 km⋅sec−1 or about 186,000 mi⋅sec−1.
- One clock stayed on the ground; its double flew. / And it ran slow. So, then. The mad thing's true.
- What makes writing relativity so tricky is this: Built into ordinary language — in its use of tenses, for example — are many implicit assumptions about the nature of temporal relations that we now know to be false. Most importantly, we have known since 1905 that when you say that two events in different places happen at the same time you are not referring to anything inherent in the events themselves. You are merely adopting a conventional way of locating them that can differ from other equally valid conventional assignments of temporal order which do not have the events happening at the same time.
- It was the space doctor who figured out the answer. He said that if our ideas about light were right, then our ideas about distance and seconds must be wrong. He said that time doesn’t pass the same for everyone. When you go fast, he said, the world around you changes shape, and time outside starts moving slower.
The doctor came up with some numbers for how time and space must change to make the numbers for light work. With his idea, everyone would see light moving the right distance every second. This idea is what we call his special idea.
The special idea is really, really strange, and understanding it can take a lot of work. Lots of people thought it must be wrong because it’s so strange, but it turned out to be right. We know because we’ve tried it out. If you go really fast, time goes slower. If you’re in a car, you see watches outside the car go slower. They only go a little slower, so you wouldn’t notice it in your normal life; it takes the best watches in the world to even tell that it’s happening. But it really does happen.
- Randall Munroe, "The Space Doctor’s Big Idea" (Nov 18, 2015)
- After the doctor figured out the special idea, he started thinking about weight. Things with weight pull on each other. Earth pulls things down toward it, which is why you can’t jump to space. Earth also pulls on the moon, keeping it near us, and the sun pulls on Earth in the same way. It turns out that light gets pulled by weight, too. (People weren’t sure about this for a while, because it moves so fast that it only gets pulled a little.)
Someone very careful might notice that this gives us a new problem: How can light turn? The numbers that explain how light moves also say that it can only go forward. It can’t change direction in empty space. That’s just what the numbers for light say—the same numbers that say it always moves a certain distance every second.
If a light wave is pulled down, it has to turn to point down, since it can’t travel to the side. To turn, the bottom part of the wave has to go slower than the top part, since it’s going a shorter distance in the same time. But that can’t be right, because the numbers say that light can’t go faster or slower. We’re in trouble again. And, once again, the space doctor has an answer.
The space doctor figured out that to explain how weight pulls things like light, we have to play around with time again. He showed that if time itself goes slower near heavy things, then the side of the light near the heavy thing won’t go as far every second. This lets the light turn toward the heavy thing.
The doctor’s idea was that weight slows down time, and it explained how light could bend. But to figure out how much light bends, we need to look at the other part of the doctor’s big idea. To talk about that part, let’s forget about light and instead visit another world.
- Randall Munroe, "The Space Doctor’s Big Idea" (Nov 18, 2015)
- There is a point of view according to which relativity theory is the end-point of "classical physics", which means physics in the style of Newton-Faraday-Maxwell, governed by the "deterministic" form of causality in space and time, while afterwards the new quantum-mechanical style of the laws of Nature came into play. This point of view seems to me only partly true, and does not sufficiently do justice to the great influence of Einstein, the creator of the theory of relativity, on the general way of thinking of the physicists of today. By its epistemological analysis of the consequences of the finiteness of the velocity of light (and with it, of all signal-velocities), the theory of special relativity was the first step away from naive visualization. The concept of the state of motion ,of the "luminiferous aether", as the hypothetical medium was called earlier, had to be given up, not only because it turned out to be unobservable, but because it became superfluous as an element of a mathematical formalism, the group-theoretical properties of which would only be disturbed by it.
- Wolfgang Pauli (1956), Preface of Theory of Relativity
- By the widening of the transformation group in general relativity the idea of distinguished inertial coordinate systems could also be eliminated by Einstein as inconsistent with the group-theoretical properties of the theory. Without this general critical attitude, which abandoned naive visualizations in favour of a conceptual analysis of the correspondence between observational data and the mathematical quantities in a theoretical formalism, the establishment of the modern form of quantum theory would not have been possible.
- Wolfgang Pauli (1956), Preface of Theory of Relativity
- I consider the theory of relativity to be an example showing how a fundamental scientific discovery, sometimes even against the resistance of its creator, gives birth to further fruitful developments, following its own autonomous course.
- Wolfgang Pauli (1956), Preface of Theory of Relativity
- Einstein's famous theory of relativity states that while phenomena appear different to someone close to a black hole, traveling close to the speed of light, or in a falling elevator here on earth, scientists in profoundly different environments will nevertheless always discover the same underlying laws of nature.
- F. David Peat, From Certainty to Uncertainty (2002)
- Relativity distorted classical expectations in a way that Clavain still did not find entirely intuitive. Slam two objects towards each other, each with individual velocities just below light-speed, and the classical result for their closing velocity would be the sum of their individual speeds: just under twice the speed of light. Yet the true result, confirmed with numbing precision, was that the objects saw each other approach with a combined speed that was still just below the speed of light. Similarly, the relativistic closing velocity for two objects moving towards each other with individual speeds of one-half of light-speed was not light-speed itself, but eight-tenths of it. It was the way the universe was put together, and yet it was not something the human mind had evolved to accept.
- There is another side to the theory of relativity. ...the development of science is in the direction to make it less subjective, to separate more and more in the observed facts that which belongs to the reality behind the phenomena, the absolute, from the subjective element, which is introduced by the observer, the relative. Einstein's theory is a great step in that direction. We can say that the theory of relativity is intended to remove entirely the relative and exhibit the pure absolute.
- Willem de Sitter, "Relativity and Modern Theories of the Universe," Kosmos (1932)
- This is the mathematical formulation of the theory of relativity. The metric properties of the four-dimensional continuum are described... by a certain number (ten, in fact) of quantities denoted by gαβ, and commonly called "potentials." The physical status of matter and energy, on the other hand, is described by ten other quantities, denoted by Tαβ, the set of which is called the "material tensor." This special tensor has been selected because it has the property which is mathematically expressed by saying that its divergence vanishes, which means that it represents something permanent. The fundamental fact of mechanics is the law of inertia, which can be expressed in its most simple form by saying that it requires the fundamental laws of nature to be differential equations of the second order. Thus the problem was to find a differential equation of the second order giving a relation between the metric tensor gαβ and the material tensor Tαβ. This is a purely mathematical problem, which can be solved without any reference to the physical meaning of the symbols. The simplest possible equation (or rather set of ten equations, because there are ten g's) of that kind that can be found was adopted by Einstein as the fundamental equation of his theory. It defines the space-time continuum, or the "field." The world-lines of material particles and light quanta are the geodesics in the four-dimensional continuum defined by the solutions gαβ of these field-equations. The equations of the geodesic thus are equivalent to the equations of motion of mechanics. When we come to solve the field-equations and substitute the solutions in the equations of motion, we find that in the first approximation, i.e. for small material velocities (small as compared with the velocity of light), these equations of motion are the same as those resulting from Newton's theory of gravitation. The distinction between gravitation and inertia has disappeared; the gravitational action between two bodies follows from the same equations, and is the same thing, as the inertia of one body. A body, when not subjected to an extraneous force (i.e. a force other than gravitation), describes a geodesic in the continuum, just as it described a geodesic, or straight line, in the absolute space of Newton under the influence of inertia alone.
The field-equations and the equations of the geodesic together contain the whole science of mechanics, including gravitation.
- Willem de Sitter, "Relativity and Modern Theories of the Universe," Kosmos (1932)
- Two points should be specially emphasized in connection with the general theory of relativity.
First, it is a purely physical theory, invented to explain empirical physical facts, especially the identity of gravitational and inertial mass, and to coordinate and harmonize different chapters of physical theory, especially mechanics and electromagnetic theory. It has nothing metaphysical about it. Its importance from a metaphysical or philosophical point of view is that it aids us to distinguish in the observed phenomena what is absolute, or due to the reality behind the phenomena, from what is relative, i.e. due to the observer.
Second, it is a pure generalization, or abstraction, like Newton's system of mechanics and law of gravitation. It contains no hypothesis, as contrasted with the atomic theory or the theory of quanta, which are based on hypothesis. It may be considered as the logical sequence and completion of Newton's Principia. The science of mechanics was founded by Archimedes, who had a clear conception of the relativity of motion, and may be called the first relativist. Galileo, who was inspired by the reading of the works of Archimedes, took the subject up where his great predecessor had left it. His fundamental discovery is the law of inertia, which is the backbone of Newton's classical system of mechanics, and retains the same central position in Einstein's relativistic system. Thus one continuous line of thought can be traced through the development of our insight into the mechanical processes of nature... characterized by the sequence... Archimedes, Galileo, Newton, Einstein.
- Willem de Sitter, The Astronomical Aspect of the Theory of Relativity (1933)
- The best presentation of the general theory [of relativity] is still Eddington's book of 1923, The Mathematical Theory of Relativity. For the planetary motion and the motion of the moon, see: de Sitter, "On Einstein's theory of gravitation and and its astronomical consequences," Monthly Notices, R. Astr. Soc. London, 76:699; 77:155. The mathematical foundation, the calculus of tensors, is given very completely in Eddington's book. For an exhaustive treatment see: Levi-Cevita, The Absolute Differential Calculus, translated by Dr. E. Perisco (1927).
- Willem de Sitter, The Astronomical Aspect of the Theory of Relativity (1933) footnote
- It did not last: the Devil howling 'Ho!
Let Einstein be!' restored the status quo.
- Einstein's theory of relativity has advanced our ideas of the structure of the cosmos a step further. It is as if a wall which separated us from Truth has collapsed. Wider expanses and greater depths are now exposed to the searching eye of knowledge, regions of which we had not even a presentiment. It has brought us much nearer to grasping the plan that underlies all physical happening.
- Hermann Weyl, Space—Time—Matter (1922)
The Evolution of Scientific Thought from Newton to Einstein (1927)Edit
- A. D'Abro, book at archive.org
- With the new views advocated by Riemann... the texture, structure or geometry of space is defined by the metrical field, itself produced by the distribution of matter. Any non-homogeneous distribution of matter would then entail a variable structure of geometry for space from place to place. ...
Riemann's exceedingly speculative ideas on the subject of the metrical field were practically ignored in his day, save by the English mathematician Clifford, who translated Riemann's works, prefacing them to his own discovery of the non-Euclidean Clifford space. Clifford realised the potential importance of the new ideas and suggested that matter itself might be accounted for in terms of these local variations of the non-Euclidean space, thus inverting in a certain sense Riemann's ideas. But in Clifford's day this belief was mathematically untenable. Furthermore, the physical exploration of space seemed to yield unvarying Euclideanism. ...it was reserved for the theoretical investigator Einstein, by a stupendous effort of rational thought, based on a few flimsy empirical clues, to unravel the mystery and to lead Riemann's ideas to victory. (In all fairness to Einstein... he does not appear to have been influenced directly by Riemann.) Nor were Clifford's hopes disappointed, for the varying non-Euclideanism of the continuum was to reveal the mysterious secret of gravitation, and perhaps also of matter, motion, and electricity. ...
Einstein had been led to recognize that space of itself was not fundamental. The fundamental continuum whose non-Euclideanism was fundamental was... one of Space-Time... possessing a four-dimensional metrical field governed by the matter distribution. Einstein accordingly applied Riemann's ideas to space-time instead of to space... He discovered that the moment we substitute space-time for space (and not otherwise), and assume that free bodies and rays of light follow geodesics no longer in space but in space-time, the long-sought-for local variations in geometry become apparent. They are all around us, in our immediate vicinity... We had called their effects gravitational effects... never suspecting that they were the result of those very local variations in the geometry for which our search had been in vain....the theory of relativity is the theory of the space-time metrical field.
- Einstein's definition... does not differ in spirit from the definitions in classical science; its sole advantage is that it entails a minimum of assumptions, and is susceptible of being realised in a concrete way permitting a high degree of accuracy in our measurements. Einstein's definition, is then, as follows: If we consider a ray of light passing through a Galilean frame, its velocity in the frame will be the same regardless of the relative motion of the luminous source and frame, and regardless of the direction of the ray. ...when it was found that contrary to the anticipations of classical science not the slightest trace of anisotropy could be detected even by ultra-precise experiment, the objections which classical science may might have presented... lost all force. ...ether drift appeared to exert no influence one way or the other. ...
Isotropy signifies that the velocity of light is the same in all directions. And how can we ascertain the equality of a velocity in all directions when we do not yet know how to measure time? Experimenters solved the difficulty by appealing to the observation of coincidences. ...
Waves of light leaving the centre of a sphere simultaneously are found to return to the centre also in concidence, after having suffered a reflection against a highly polished inner surface of the sphere. ...the light waves have thus covered equal distances in the same time; whence we conclude that their speed is the same in all directions.
Inasmuch as this experiment has been performed, yielding the results we have just described, even though the ether drift caused by the earth's motion should have varied in direction and intensity, the isotropy of space to luminous propogations was thus established. (The experiment described constitutes but a schematic form of Michelson's.) It is to be noted that in this experiment the observation of coincidences is alone appealed to (even spatial measurements can be eliminated). This is because in Michelson's experiment it is not necessary to consider a sphere. The two arms of the apparatus may be of different lengths; and all that is observed is the continued coincidence of the interference-bands with markings on the instrument. When it is realised that coincidences constitute the most exact form of observation, we understand why it is that Einstein's definition is justified
- The most precise experiments have proved the correctness of the Einsteinian laws of mechanics and...Bucherer's experiment proving the increase in mass of an electron in rapid motion is a case in point.
Very important differences distinguish the theory of Einstein from that of Lorentz. Lorentz also had deduced from his theory that the mass of the electron should increase and grow infinite when its speed neared that of light; but the speed in question was the speed of the electron through the stagnant ether; whereas in Einstein's theory it is merely the speed with respect to the observer. According to Lorentz, the increase in mass of the moving electron was due to its deformation or Fitzgerald contraction. The contraction modified the lay of the electromagnetic field round the electron; and it was from this modification that the increase in mass observed by Bucherer was assumed to arise. In Einstein's theory, however, the increase in mass is absolutely general and need not be ascribed to the electromagnetic field of the electron in motion. An ordinary unelectrified lump of matter like a grain of sand would have increased in mass in exactly the same proportion; and no knowledge of the microscopic constitution of matter is necessary in order to predict these effects, which result directly from the space and time transformations themselves.
Furthermore, the fact that this increase in mass of matter in motion is now due to relative motion and not to motion through the stagnant ether, as in Lorentz's theory, changes the entire outlook considerably. According to Lorentz, the electron really increased in mass, since its motion through the ether remained a reality. According to Einstein, the electron increases in mass only in so far as it is in relative motion with respect to the observer. Were the observer to be attached to the flying electron no increase in mass would exist; it would be the electron left behind which would now appear to have suffered the increase. Thus mass follows distance, duration and electromagnetic field in being a relative and having no definite magnitude of itself and being essentially dependent on the conditions of observation.
Owing to the general validity of the Lorentz-Einstein transformations, it becomes permissible to apply them to all manner of phenomena.. ...temperature, pressure and many other physical magnitudes turned out to be relatives. ...entropy, electric charge and the velocity of light in vacuo were absolutes transcending the observer's motion. ...a number of other entities are found to be absolutes, the most important of which is that abstract mathematical quantity called the Einsteinian interval, which plays so important a part in the fabric of the new objective world of science, the world of four-dimensional space-time.
- Consider two observers, one... moving uniformly along a straight line, the other [stationary] on the embankment. At the precise instant these two observers pass each other at a point P, a flash of light is produced at the point P. The light wave produced by the instantaneous flash will present the shape of an expanding sphere. Since the invariant velocity of light holds equally for either observer, we must assume that either observer will find himself at all times situated at the centre of the expanding sphere.
Our first reaction might be to say: "What nonsense! How can different people, travelling apart, all be at the centre of the same sphere?" Our objection, however, would be unjustified.
- If our world-line and that of the body which is being observed are parallel, the body is said to be at rest. But if the two world-lines are not parallel, then, when interpreting things in terms of space and time, the body will be said to be in relative motion.
- Hendrik Lorentz, The Einstein Theory of Relativity: A Concise Statement (1920)
- Albert Einstein, Relativity: The Special and General Theory (1920)
- Arthur Eddington, Space, Time and Gravitation: An Outline of the General Relativity Theory (1921) | 0.817899 | 3.76634 |
We know you’re all fired up about Mars lately, but closer to home, NASA still has a lot of work to do on the moon — Earth’s moon. And some of that work starts today with the GRAIL mission.
GRAIL stands for Gravity Recovery and Interior Laboratory (GRAIL); it’s a moon-orbiting pair of spacecraft that’s collecting data between now and the end of the year.
The mission’s equipment was turned on just hours ago; its purpose is to map the moon’s gravity field and how topical features of the moon’s crust affect the moon’s gravity. That map will give scientists an even better understanding of the moon’s internal makeup as well as its evolution through time.
Right now, the twin spacecraft, named Ebb and Flow (presumably after the moon’s gravitational effect on Earth’s tidal activity), are orbiting 19 miles above the Oceanus Procellarum, the largest of the moon’s seas.
“The data collected during GRAIL’s primary mission team are currently being analyzed and hold the promise of producing a gravity field map of extraordinary quality and resolution,” said MIT principle GRAIL investigator Maria Zuber in a release on the news.
“Mapping at a substantially lower altitude during the extended mission and getting an even more intimate glimpse of our nearest celestial neighbor, provides the unique opportunity to globally map the shallow crust of a planetary body beyond Earth.”
To take measurements, Ebb and Flow transmit radio signals between themselves to capture the rate of change of distance between them. As gravity on the spacecraft fluctuates due to craters, mountains, and sub-surface geological features, the distance between Ebb and Flow will change. | 0.883827 | 3.438287 |
Black holes are regions of spacetime that form when massive stars collapse at the end of their life cycles and can continue to grow by absorbing stars and merging with other black holes. This interaction allows scientists to identify their presence, as electromagnetic radiation is given off as visible light across space. But, they could one day pose a problem.
History’s “10 Ways the World Will End” revealed how these space anomalies could one day pose a problem to life on Earth.
The series detailed earlier this month: “There are 100,000,00 black holes in our galaxy, with vicious gravitational forces, that devour everything in their path.
“If one headed straight for Earth, and we were sucked into its deadly vortex, what would happen to our planet? Would mankind survive?
“Of all the objects in space, this lethal mass possesses the strongest gravitational pull, earning its name, because nothing, not even light, can escape the grasp.
Black holes pose a threat to Earth, according to scientists
“Anything or anyone that crosses its outer edge – an invisible boundary known as the event horizon – will never be seen again.
“A black hole coming towards Earth has cruised through the universe for billions of years, growing larger as it swallows stars, planets and everything else in its path.”
American theoretical physicist Michio Kaku revealed how scientists were stunned to discover that rogue black holes do inhabit the Milky Way.
He said: “Some people compare a black hole to a celestial zombie, it comes to life when anything comes too close.
“It grabs that object in its clutches and never lets go.
“We used to think that black holes were stationary, but we were shocked to find that there are rogue black holes that wander across the galaxy.
“If you get so close to a back hole that you are in the grip of its gravitational field, then no matter what you do, you are doomed to fall into the black hole.”
Greg Laughlin, an astrophysicist from the University of California, then painted a dim picture for life on Earth should a black hole spring to life.
He said: “Every black hole is capable of reanimating itself when it is in the vicinity of matter, so every black hole has the capability to suddenly spring to life as a truly vicious killer.
“Nobody on Earth is safe or secure once the event horizon of a supermassive black hole has been breached.
Black hole shock: Scientist's dire warning to humans [VIDEO]
Asteroid apocalypse: Scientist warns of ‘city-destroying’ space rock [OPINION]
Why ‘Trillion tonne rock hurtling towards Earth’ was 'bad news' [EXPLAINED
“But, for a while, life would go on.”
The series then detailed how humans would suffer a torrid time on their final days on Earth, before the inevitable doomsday.
He added: “As the Earth finally passes through the event horizon, it’s majestic, instead of a big bang, there is light.
“This cosmic light show may be amazing, but it’s also confirmation that our planet has entered a black hole and we’re being pulled closer to the doomsday point at its centre, known as the singularity.
“With the Earth close to the singularity, buildings, bridges and the Earth’s surface itself violently buckle.
“The black hole’s gravity is now so strong, that it can bend, twist or tear our planet like a sheet of paper.” | 0.861393 | 3.086696 |
For model, the animations shown here oscillate roughly once every two seconds. In these seasonably disconcert, space had not yet become "limpid", so observations supported upon light, radio waves, and other electromagnetic radiation that remote back into opportunity are circumscribed or unavailable. The more information we can muster by developing ever more sophistichated theoretical design, the finisher we will get to communicate the genuine quality of neutron bespangle.
Gravitational waves are uniformly passing Earth; However, even the strongest have a small operation and their spring are comprehensively at a big ceremoniousness. The period, distribution, and makeup of the stars in a galaxy trace the history, dynamics, and evolution of that galaxy. For case, the waves given off by the cataclysmic decisive fusion of GW150914 extent Earth after journey over a billion day-ages, as a ripple in spacetime that changed the roll of a 4 km LIGO arm by a minute of the size of a proton, proportionally analogous to vary the discrepancy to the proximal star outside the Solar System by one hair's tread. This tiny expression from even excessive gravitic waves cause them remarkable on Earth only with the most adulterated detectors. This would correspond to a throng of 0.5 Hz, and a wavelength of about 600 000 km, or 47 times the caliber of the Earth.
Stars are the most far allow astronomical opposed, and depict the most basilar building blocks of galaxies. The velocity, wavelength, and frequency of a gravitic wave are related by the equation c = λ f, just like the equality for a publicity wave. Therefore, gravitic waves are think in postulate to have the possible to provide a wealth of observational data about the very early macrocosm.
Co-lead occasion, Dr Patricia Schmidt, added: "Almost three years after the first gravitational-waves from a base 2 neutron bespangle were observed, we are still maintenance novel ways to descent more advertisement concerning them from the extraordinary. In especial, gravitational waves are expected to be genuine by the dullness of the very soon universe. Moreover, bespangle are accountable for the devise and distribution of heavy elements such as carbon, propellant, and oxygen, and their characteristics are intimately bond to the characteristics of the revolving systems that may united near them. Consequently, the study of the birth, animation, and extinction of bespangle is central to the field of astrology.
Due to the weakness of the coupling of gravity to matter, gravitational waves experience very little engagement or scattering, even as they parturition over astronomic distances. | 0.809026 | 3.848976 |
The Lunar Cherenkov Technique: From Parkes Onwards
The lunar Cherenkov technique, which aims to detect the coherent Cherenkov radiation produced when UHE particles interact in the lunar regolith, was first attempted with the Parkes radio-telescope in 1995, though the theory was not sufficiently developed at this time to calculate a limit on the UHE neutrino flux from the non-observation. Since then, the technique has evolved to include experiments utilising lower frequencies, wider bandwidths, and entire arrays of antenna. We develop a simulation to analyse the full range of experiments, and calculate the UHE neutrino flux limit from the Parkes experiment, including the directional dependence. Our results suggest a methodology for planning future observations, and demonstrate how to utilise all available information on the nature of radio pulses from the Moon for the detection of UHE particles.
The Lunar Cherenkov Technique: From Parkes Onwards
C. W. James, R. D. Ekers, R. A. McFadden, R. J. Protheroe
School of Chemistry & Physics, Univ. of Adelaide, SA, Australia
Australia Telescope National Facility, Epping, NSW, Australia
University of Melbourne, Vic., Australia
The lunar Cherenkov technique aims to detect ultra-high energy (UHE: EeV) cosmic rays and neutrinos via the coherent Cherenkov radiation emitted in the radio regime by their interactions in the outer layers of the Moon. The radiation is detected via ground-based radio-telescopes, as first proposed by Dagkesamanskii & Zheleznykh and attempted at Parkes .
The use of existing radio-telescopes has meant that the choice of observational parameters such as frequency, bandwidth, and length of run has been limited. A ‘next-generation’ radio-array, the SKA (Square Kilometre Array, ), is currently in the planning stages, providing a unique opportunity to optimise a powerful instrument for this technqiue. The ultimate goal of the lunar Cherenkov technique is to determine the energy and arrival directions of the highest energy cosmic rays and neutrinos. Here, we propose how observations might be tailored to achieve this, by examining the frequency- and directional-dependence of the sensitivity of both the Parkes experiment and a nominal SKA to UHE neutrinos.
The program used to simulate the lunar Cherenkov technique was a Monte Carlo code described in James et al. . This code, like previous simulations, only included a single layer in which detectable UHE particle interactions were allowed. However, as the regolith properties are expected to reflect that of the underlying material, we modified the code to allow UHE neutrino interactions in the sub-regolith layer, modelled with density g/cm. This layer was treated simply as denser regolith, with refractive index and absorption length scaled by density as per Olhoeft & Strangway to and .
The effect of including only the classical regolith was to artificially limit the aperture to neutrinos of energies sufficiently large that interactions at the base of this (typically m deep) layer were being readily detected, especially at low frequencies, where attenuation within the regolith is minimal. Including two layers is more appropriate than extending a single layer to greater depths, since some radiation losses are to be expected during the transmission of radio-waves from the underlying material (be it lava flows in the mare or megaregolith in the highlands) to the regolith.
The parameters used to simulate the Parkes experiment are also described James et al. For the nominal SKA, we use an effective collecting area of km, a system temperature = K, and uniform coverage of the Moon over all frequencies. Detection required an integrated signal strength in V/m over the full bandwidth of times the RMS noise voltage.
1.2 Results – Frequency Dependence
The first lunar Cherenkov experiments observed at frequencies in the GHz range, as the power radiated at the Cherenkov angle scales with until the turnover frequency ( GHz in the regolith ), above which decoherence effects from within the particle cascade become important. Recently, focus has been on observations at lower frequencies, as proposed by Scholten et al. . At low frequencies, the Cherenkov cone is broader, and the radiation suffers less attenuation in propagating to the surface, allowing signals from a wider range of interaction geometries at greater depths in the regolith to be detected. For a simulated experiment with LOFAR, assuming a bandwidth of MHz, Scholten et al. found an optimum frequency range in the MHz band, below which (in the MHz band) the effect of increasing sky temperature on sensitivity became significant.
High-frequency experiments have a lower energy detection threshold, since the signal from geometrically favourable events peaks in the GHz regime. How this impacts upon event rates depends on the shape of the UHE particle spectrum, and the aperture at these energies. Another reason to not limit observations to low frequencies only is that to perform true UHE particle astronomy, the type, energy, and arrival direction of any detected particles will need to be determined. The sensitivity of the high frequency component to interaction geometry means it could be used to resolve ambiguities between interaction energy, interaction depth, and orientation of the shower axis with respect to the observer, which would likely remain unresolved in an experiment with a low frequency range.
The range of spectra plotted in Fig. 1 shows the dilemma. Any single choice of bandwidth over which to trigger results in reduced sensitivity to some fraction of events, since noise from the frequency range over which the signal is weakest will force a higher detection threshold. To detect the full range of events, it will be essential to observe across the entire frequency range. However, the design of an appropriate trigger algorithm is non-trivial, and as discussed by McFadden et al. , is a work in progress. Here we restrict our results to ‘small’ () bandwidths, which necessarily underestimates the SKA’s potential, but gives a good indication of the relative importance of the frequency ranges examined.
We run our simulation for the range of frequencies from MHz to GHz, using bandwidths set at a fixed fraction () of the central frequency, reflecting that instruments designed to observed at higher frequencies tend to have a higher available bandwidth. The results, together with the recalculated Parkes aperture, are shown in Fig. 2.
For neutrino energies eV (i.e. well above threshold), and frequencies between MHz and GHz, the total effective aperture varies approximately as , in agreement with that of Scholten et al. However, this dependence weakens at lower energies, and as neutrino energy decreases below the effective detection threshold, the aperture peaks at higher and higher frequencies. Therefore, the choice of an optimal aperture depends on the assumed UHE neutrino flux, about which little is known.
1.3 Results – Directional Sensitivity
Including geometrical tags in the simulation allows the sensitivity to be determined as a function of particle arrival direction, relative to the lunar center and beam pointing position. Fig. 3 shows the instantaneous aperture of the Parkes experiment in limb-pointing configuration. The total fraction of the sky seen at any one instant is small; the Moon’s opacity to neutrinos at UHE creates a ‘shadow’ much larger than its apparent size () on the (left) side opposite the beam pointing position.
We define the ‘directionality’, , to be the ratio of peak over mean directional sensitivity, which measures the ratio of potential point-source sensitivity over the sensitivity to an isotropic flux. For Parkes in limb-pointing configuration, this is 28; should a point-like neutrino-source be suspected/discovered, a careful choice of observation times and beam pointing positions would enable a much stronger limit to be placed.
For experiments (eg. with the SKA) which observe the Moon uniformly, the sensitivity forms an annulus around the Moon, as shown in Fig. 4. Similar results would be obtained by placing multiple smaller beams around the limb of the Moon, as might be achieved with a focal plane array. Unlike the total aperture, the directional properties vary slowly with observation frequency, with the annular sensitivity increasing in width with reduced frequency. An important result is that for energies well above threshold, the aperture to all arrival directions is greater at low frequencies.
Fig. 5 plots the long-term directional sensitivity to eV neutrinos of a low- to mid-frequency SKA ( MHz) placed at the equator. Evidently, there exists a significant overlap between the nominal ANITA and SKA apertures, and large regions of the sky to which neither experiment is sensitive. SKA coverage will be more uniform at lower frequencies. Fortuitously, the sinusoidal ‘wobble’ of the lunar orbit about has phase aligned approximately with the supergalactic plane, from which we might expect to see an excess of UHE particles. Since the SKA will be sited in either South Africa or Australia, the sensitivity will be greater to any Southern Hemisphere sources (eg the Galactic Centre), since the Moon will be visible for longer when it is in negative declinations.
The highly directional sensitivity of the Parkes experiments suggests that current limits on the UHE neutrino flux are a strong function of celestial coordinates. The current strongest limits on an isotropic flux below eV come from ANITA-lite , which had little sensitivity beyond from zero declination. Limits from other lunar Cherenkov experiments observing at higher frequencies at Goldstone and Kalyazin will be more directional than those at Parkes, and thus large areas of the sky would still be left unprobed. This leaves ample scope for experiments with different directional sensitivities to make useful observations to further constrain the UHE neutrino flux.
The future of the lunar Cherenkov technique as a means to determine the flux of the highest energy cosmic rays and neutrinos hinges on the ability to turn positive detections into useful information on particle energy and arrival direction. This requires taking full advantage of the wide frequency range available to instruments such as the SKA, and will likely require multiple detection algorithms, optimised for various pulse spectra, to be used in parallel. The optimisation must take into account the steepness and degree of anisotropy in the (known or expected) UHE particle flux, as well as the sensitivites of other experiments. The already high signal processing requirements of de-dispersion and sub-nanosecond time resolution over a large array will make further innovation in pulse detection technology a necessity.
We have found the lunar Cherenkov technique to be highly directionally sensitive, especially at high frequencies. We have also demonstrated that observations over a broad frequency range with the SKA will be a very powerful technique for UHE particle astronomy. With further improvements in simulation methods, and knowledge of the lunar near-surface, it will be possible to devise advanced pulse detection and reconstruction algorithms, based on the methodology presented here.
This research was supported under the Australian Research Council’s Discovery funding scheme (project # DP0559991). Professor R. D. Ekers is the recipient of an Australian Research Council Federation Fellowship (project # FF0345330).
- R. D. Dagkesamanskii, & I. M. Zheleznykh, Sov. Phys. JETP Let., 50, 233, 1989.
- T. H. Hankins, R. D. Ekers, J. D. O’Sullivan MNRAS, 283, 1027, 1996.
- Y. Terzian and J. Lazio. In L. M. Stepp, ed, Ground-based and Airborne Telescopes. Proc. of the SPIE, 6267, 2006.
- C. W. James et al. MNRAS, 379,3, 2007.
G. R. Olhoeft & D. W. Strangway.
Earth and Planetary Sci. Lett. , 24, 394, 1975.
- J. Alvarez-Muñiz, Phys. Rev. D, 74, 2, 023007, 2006
- O. Scholten et al. Astropart. Phys. , 26, 219, 2006.
- R. A. McFadden et. al., 30 ICRC Proc., Contribution 0434, 2007.
- P. Miočinović et al., astro-ph/0503304 v1, 2005
- S. Barwick et al., Phys. Rev. Lett., 96, 171101, 2006
- Gorham P. W. et al., Phys. Rev. Lett., 93, 041101, 2004
- A. R. Beresnyak et al., Astronomy Reports, 49, 127, 2005 | 0.865457 | 4.053553 |
This story popped up yesterday, and I can imagine it will go far, since it talks about life in the universe. I get it, it’s what people are interested in, and at least this story is focused on the science of why this is the best place to look for intelligent civilizations, instead of “Oh hey there’s a strange ring of material around a star, must be an alien superstructure.” But I digress.
So where is the best place to look for life in the universe? The answer is in a Globular Cluster.
A globular cluster is one of the oldest structures in the universe. Consisting of ancient stars, most of them formed about 10 Billion years ago, and contain millions of stars in a densely packed space only 100 light years across. The Milky Way is host to about 150 of these clusters, but some larger galaxies can have thousands.
So why are they such good places for life to develop?
Because they are very old, they tend to be lacking in the heavy elements that life needs, like Iron and Silicon, since their stars haven’t died and enriched the surrounding interstellar medium. This should make them very unlikely to host planets and subsequently life. In fact, only one planet has ever been discovered within a globular cluster.
But this could be a premature assessment. When looking at exoplanets in general, there is definitely a preference for Jupiter size planets developing in metal-rich environments, but so far there is no preferential environment for Earth-like exoplanets.
The other cause for concern in a globular cluster is the fact that stars are packed so close together, any gravitational interactions from a star that passes by could send planets flying out into the cold of interstellar space. And yes space is very cold, even in the densely packed globular clusters.
But here’s the thing, the more massive stars in a globular cluster would have died out long ago since they would burn through their fuel more quickly, and so most stars are smaller and redder, giving them less ‘muscle’ when interacting with other stars gravitationally. They would also have a habitable zone (range of distances from a star where water could be liquid) closer to their star, meaning any habitable planets would orbit closer and be much harder to perturb. Maybe globular clusters are good places for life.
If life formed in a globular cluster, the nearest star would be about 20 times closer than the nearest star to the Sun. This means that any advanced civilization could master interstellar travel and communication much more easily than we can. If this is possible, they could get to higher levels of technology in a shorter period of time. Maybe we have to start looking for signals from intelligent life in a globular cluster. Maybe the first step is trying to find planets and showing that they are plentiful in such an environment. Or maybe we will never know. | 0.828021 | 3.633327 |
It's worth noting that in many cases, if not most, we simply don't know the exact answer to such excellent questions as the one you ask.
Note that the book you mention (ISBN-13: 978-0471409762) was written around 2000 and appeared in 2002: that's a really long time ago in terms of all the amazing new instruments which have become available.
For example, while the Hubble telescope was operational when that book was written, the amazing GAIA telescope (link), which would perhaps be relevant to your question, only started operating around 2014.
The youtube video you mention seems to be more up to date - a couple years ago. But then, the author (even if he's an expert) may not especially be keeping up with the latest research and thinking on the particular star system you mention.
So it's worth bearing in mind that many of these questions, we just don't know - it's something that is being actively studied now!
An interesting point to consider: we're not even really sure of the distance to the Polaris system - for goodness sake! That may be a surprise. It looks like estimates of the distance - and they are just estimates - range from roughly 350 to 450 light years. We could be out by a hundred light years.
Regarding your specific question: how many stars are in the system. Don't forget when you look at a specific star, X, let's say it is 500 ly away. In the same "shot" you see a vast number of stars right next to star X. Some of those may be "next door to us" and some may be tremendously further away. It is by no means a "sure thing" to determine if two stars which appear right next to each other, are actually anywhere near each other.
(A good example of that is ... you know the Andromeda Galaxy, which you can even see with your eye. At first, astronomers had no clue if it was a thing (sort of like a star, but cloudy), and as close to us as the other stars, or, if it was an enormous object an incredible distance away. Obviously we now know it is truly huge thing an unbelievably long way away ... but, we only learned that in about 1920 - !!! Not even 100 years ago.)
For a short point on your specific question: note that the book by Plait is some 15+ years old, and the video talk is more recent; in the first instance you can go with the info in the video talk. It's a good example of how astronomy knowledge is dramatically changing all the time. | 0.82597 | 3.28977 |
They Just Keep Going and Going and Going…
NASA’s Voyager spacecrafts were initially launched in 1977, and 40 years later, NASA can confirm that both Voyager 1 and Voyager 2 are still functioning and making their way through space. Neither is showing any signs of slowing, and it’s unlikely they’ll need to be shut down anytime soon.
Everyday, the pair of spacecrafts send information back to NASA regarding the conditions of their current locations, which includes areas where our Sun has minimal to no influence. Voyager 1, which is 13 billion miles away from Earth, travels through interstellar space, moving northward out of the plane containing our planets. Voyager 2, meanwhile, is 11 billion miles away from Earth, and moving southward.
Both have seen a lot over the years, including Voyager 2’s flyby of the four outer planets — Jupiter, Saturn, Uranus, and Neptune — volcanoes on Jupiter’s moon Io, an Earth-like atmosphere on Saturn’s moon Titan, and geysers of icy cold nitrogen on Neptune’s moon Triton. Voyager 1 was the first to reach interstellar space, and is currently the only spacecraft to do so, though Voyager 2 is expected to do the same relatively soon.
“I believe that few missions can ever match the achievements of the Voyager spacecraft during their four decades of exploration,” said Thomas Zurbuchen, associate administrator for NASA’s Science Mission Directorate (SMD) at NASA Headquarters. “They have educated us to the unknown wonders of the universe and truly inspired humanity to continue to explore our solar system and beyond.”
Thanks to the two probes and their opposing trajectories, NASA scientists have been able to gather invaluable information on the heliosphere — the bubble of solar wind containing our system’s planets. When Voyager 2 reaches interstellar space within the next few years, scientists will be able to see how the heliosphere interacts with the interstellar medium from multiple locations simultaneously; this medium being a region in which the magnetic field is being affected by nearby solar wind. The existence of this medium was first noticed by NASA in 2015, three years after Voyager 1 made it to interstellar space. | 0.819069 | 3.062033 |
But all this attention only led Heim to retreat from the public eye. This was partly because of his severe multiple disabilities, caused by a lab accident when he was still in his teens. But Heim was also reluctant to disclose his theory without an experiment to prove it. He never learned English because he did not want his work to leave the country. As a result, very few people knew about his work and no one came up with the necessary research funding. In 1958 the aerospace company Bölkow did offer some money, but not enough to do the proposed experiment.
While Heim waited for more money to come in, the company’s director, Ludwig Bölkow, encouraged him to develop his theory further. Heim took his advice, and one of the results was a theorem that led to a series of formulae for calculating the masses of the fundamental particles – something conventional theories have conspicuously failed to achieve. He outlined this work in 1977 in the Max Planck Institute’s journal Zeitschrift für Naturforschung, his only peer-reviewed paper. In an abstruse way that few physicists even claim to understand, the formulae work out a particle’s mass starting from physical characteristics, such as its charge and angular momentum.
Yet the theorem has proved surprisingly powerful. The standard model of physics, which is generally accepted as the best available theory of elementary particles, is incapable of predicting a particle’s mass. Even the accepted means of estimating mass theoretically, known as lattice quantum chromodynamics, only gets to between 1 and 10 per cent of the experimental values.
But in 1982, when researchers at the German Electron Synchrotron (DESY) in Hamburg implemented Heim’s mass theorem in a computer program, it predicted masses of fundamental particles that matched the measured values to within the accuracy of experimental error. If they are let down by anything, it is the precision to which we know the values of the fundamental constants. Two years after Heim’s death in 2001, his long-term collaborator Illobrand von Ludwiger calculated the mass formula using a more accurate gravitational constant. “The masses came out even more precise,” he says.
After publishing the mass formulae, Heim never really looked at hyperspace propulsion again. Instead, in response to requests for more information about the theory behind the mass predictions, he spent all his time detailing his ideas in three books published in German. It was only in 1980, when the first of his books came to the attention of a retired Austrian patent officer called Walter Dröscher, that the hyperspace propulsion idea came back to life. Dröscher looked again at Heim’s ideas and produced an “extended” version, resurrecting the dimensions that Heim originally discarded. The result is “Heim-Dröscher space”, a mathematical description of an eight-dimensional universe.
From this, Dröscher claims, you can derive the four forces known in physics: the gravitational and electromagnetic forces, and the strong and weak nuclear forces. But there’s more to it than that. “If Heim’s picture is to make sense,” Dröscher says, “we are forced to postulate two more fundamental forces.” These are, Dröscher claims, related to the familiar gravitational force: one is a repulsive anti-gravity similar to the dark energy that appears to be causing the universe’s expansion to accelerate. And the other might be used to accelerate a spacecraft without any rocket fuel.
This force is a result of the interaction of Heim’s fifth and sixth dimensions and the extra dimensions that Dröscher introduced. It produces pairs of “gravitophotons”, particles that mediate the interconversion of electromagnetic and gravitational energy. Dröscher teamed up with Jochem Häuser, a physicist and professor of computer science at the University of Applied Sciences in Salzgitter, Germany, to turn the theoretical framework into a proposal for an experimental test. The paper they produced, “Guidelines for a space propulsion device based on Heim’s quantum theory”, is what won the AIAA’s award last year.
Claims of the possibility of “gravity reduction” or “anti-gravity” induced by magnetic fields have been investigated by NASA before (New Scientist, 12 January 2002, p 24). But this one, Dröscher insists, is different. “Our theory is not about anti-gravity. It’s about completely new fields with new properties,” he says. And he and Häuser have suggested an experiment to prove it.
This will require a huge rotating ring placed above a superconducting coil to create an intense magnetic field. With a large enough current in the coil, and a large enough magnetic field, Dröscher claims the electromagnetic force can reduce the gravitational pull on the ring to the point where it floats free. Dröscher and Häuser say that to completely counter Earth’s pull on a 150-tonne spacecraft a magnetic field of around 25 tesla would be needed. While that’s 500,000 times the strength of Earth’s magnetic field, pulsed magnets briefly reach field strengths up to 80 tesla. And Dröscher and Häuser go further. With a faster-spinning ring and an even stronger magnetic field, gravitophotons would interact with conventional gravity to produce a repulsive anti-gravity force, they suggest. | 0.808895 | 3.341251 |
For the first time ever, astronomers have managed to discern the colour of a planet outside of our solar system. The exoplanet, HD 189733b,* is thought to be blue in colour. They achieved this remarkable discovery by measuring light from the planet when exposed then measuring again when it slipped behind the star. They noticed a substantial drop of wavelengths corresponding to the colour blue when this happened. Unfortunately for the possibilities of finding life, this is unlikely to be water. The planet is thought to be a gas giant which practically hugs its star, giving it a temperature of around 1,000C. The blue colour probably comes from silicate precipitating in the atmosphere, which reflects light from the star. That’s right – the planet contains glass rain. Molten silicate rains horizontally in a sideways direction at around 7,000 km/h. Just imagine the geographical processes of that planet! The geology, the chemistry, the…
Every now and then a phrase or an idea leaps out from an astronomical discovery which excites the imagination; ‘glass rain’ is one of those. I don’t suppose molten silicate is even a particularly unusual occurrence, but it does indicate just how vast and diverse the Universe must be. This planet is only 63 light years away and scarcely observable as it is – what wonders could exist beyond our reach? If scientists expand on this technology and method, the possibilities of future discoveries are breathtaking. It’s moments like these I wish I had become an astrophysicist.
*And scientists wonder why exoplanets never enter the public imagination. | 0.806351 | 3.19701 |
19 May 2003 - UCL
scientists look for water on Mars with Mars Express and Beagle 2
launch date has now been set for Europe's first mission to Mars. On the 2
June 2003 at 18:45 BST, the Mars Express orbiter, together with the Beagle
2 lander, will soar above the steppes of Kazakhstan on a Soyuz-Fregat rocket.
The launch window lasts until 21 June and the arrival at Mars is just before
Christmas 2003. UCL-MSSL scientists are eagerly awaiting the launch for three
reasons: they are involved in instruments on both the lander and orbiter
- and they wish to study water in the Martian environment.
is important on Mars as it is a key ingredient for life. Scientists think
that 3.8 billion years ago Mars had flowing water on the surface, a thick
atmosphere and a protecting magnetic shield like the Earth's. Now, all
that is gone and Mars is dry and barren, has a thin carbon dioxide rich
atmosphere, and has no large scale magnetic field. However recent discoveries
by other spacecraft have shown that there may still be water, probably
in the form of permafrost, within a metre of the surface in the Martian
polar regions. There may even be water covered by snow packs on the surface.
All this points to better conditions for life on Mars 3.8 billion years
ago - and a very slim chance now too.
Mars Express Orbiter
Coates, UCL-MSSL's lead scientist for Beagle 2 and Mars Express says 'We
are in a pivotal position to look for water on Mars at UCL, as we are one
of only very few scientific groups are involved in lander and orbiter. With
our stereo camera system on the surface we will look for water in the atmosphere,
and our involvement with an experiment on the orbiter will allow us to measure
how quickly water escapes from the atmosphere, scavenged away by the solar
wind. Combined with other instruments on the orbiter which can look for water
up to 5km under the surface, Europe is going to make vital new discoveries
about water on Mars with this mission. We will have a key role in this'.
Beagle 2 lander
lead the international stereo camera team for the Beagle 2 camera. These
are the 'eyes' of Beagle 2 - and as well as making three dimensional
maps of the landing site, vital for Beagle's other instruments, the cameras
will study the Martian geology, measure water and dust in the atmosphere
and even do some astronomy. Images soon after landing will help scientists
steer by the stars as they locate the lander precisely on the surface.
for the surface of Mars has been a challenge. Stereo camera system project
manager Dr Andrew Griffiths says 'Our cameras and filter wheels will have
to survive huge temperature swings, from -100 to 0 degrees between night
and day on the surface. We also have to cope with dust and have installed,
and tested, windscreen wipers for the cameras to reduce this. Everything
is working fine and we can't wait for Beagle 2 to land on the surface'.
is also co-investigator on the ASPERA experiment on the orbiter. This will
measure how much material escapes from the Martian atmosphere at present.
This can then be extrapolated back 3.8 billion years to understand whether
the solar wind scavenging is sufficient to explain Mars' atmospheric loss
Andrew Coates - Beagle 2 Stereo Camera System lead investigator, and Mars
Express ASPERA co-investigator
Andrew Griffiths - Beagle 2 Stereo Camera System project manager
of the Mars Express Orbiter and the Beagle 2 Lander
- links to Mars Express and Beagle 2 at MSSL-UCL
www.beagle2.com - more information
about Beagle 2
- ESA Mars Express page | 0.845585 | 3.405769 |
Crescent ♓ Pisces
Moon phase on 21 April 2036 Monday is Waning Crescent, 24 days old Moon is in Pisces.Share this page: twitter facebook linkedin
Previous main lunar phase is the Last Quarter before 2 days on 18 April 2036 at 14:06.
Moon rises after midnight to early morning and sets in the afternoon. It is visible in the early morning low to the east.
Moon is passing first ∠4° of ♓ Pisces tropical zodiac sector.
Lunar disc appears visually 6.7% narrower than solar disc. Moon and Sun apparent angular diameters are ∠1784" and ∠1909".
Next Full Moon is the Flower Moon of May 2036 after 18 days on 10 May 2036 at 08:09.
There is medium ocean tide on this date. Sun and Moon gravitational forces are not aligned, but meet at very acute angle, so their combined tidal force is moderate.
The Moon is 24 days old. Earth's natural satellite is moving from the second to the final part of current synodic month. This is lunation 448 of Meeus index or 1401 from Brown series.
Length of current 448 lunation is 29 days, 12 hours and 36 minutes. It is 2 hours and 52 minutes longer than next lunation 449 length.
Length of current synodic month is 8 minutes shorter than the mean length of synodic month, but it is still 6 hours and 1 minute longer, compared to 21st century shortest.
This lunation true anomaly is ∠258.5°. At the beginning of next synodic month true anomaly will be ∠292.8°. The length of upcoming synodic months will keep decreasing since the true anomaly gets closer to the value of New Moon at point of perigee (∠0° or ∠360°).
2 days after point of apogee on 18 April 2036 at 17:40 in ♑ Capricorn. 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 1 May 2036 at 08:26 in ♋ Cancer.
Moon is 401 704 km (249 607 mi) away from Earth on this date. Moon moves closer next 9 days until perigee, when Earth-Moon distance will reach 369 111 km (229 355 mi).
1 day after its descending node on 20 April 2036 at 16:14 in ♒ Aquarius, the Moon is following the southern part of its orbit for the next 12 days, until it will cross the ecliptic from South to North in ascending node on 3 May 2036 at 21:32 in ♌ Leo.
14 days after beginning of current draconic month in ♌ Leo, the Moon is moving from the second to the final part of it.
4 days after previous South standstill on 16 April 2036 at 20:29 in ♑ Capricorn, when Moon has reached southern declination of ∠-19.540°. Next 9 days the lunar orbit moves northward to face North declination of ∠19.658° in the next northern standstill on 30 April 2036 at 19:06 in ♋ Cancer.
After 4 days on 26 April 2036 at 09:33 in ♉ Taurus, the Moon will be in New Moon geocentric conjunction with the Sun and this alignment forms next Sun-Moon-Earth syzygy. | 0.848363 | 3.129956 |
The Lunar Atmosphere and Dust Environment Explorer (LADEE) is designed to study the Moon's thin exosphere and the lunar dust environment. An "exosphere" is an atmosphere that is so thin and tenuous that molecules don't collide with each other. Studying the Moon's exosphere will help scientists understand other planetary bodies with exospheres too, like Mercury and some of Jupiter's bigger moons. The orbiter will determine the density, composition and temporal and spatial variability of the Moon's exosphere to help us understand where the species in the exosphere come from and the role of the solar wind, lunar surface and interior, and meteoric infall as sources. The mission will also examine the density and temporal and spatial variability of dust particles that may get lofted into the atmosphere.
The mission also will test several new technologies, including a modular spacecraft bus that may reduce the cost of future deep space missions and demonstrate two-way high rate laser communication for the first time from the Moon. | 0.816184 | 3.564432 |
April 8, 2020 heralds yet another super moon, and this one is being dubbed a 'pink moon'. So what does that mean, and just how rare is this phenomenon? Here's what you need to know about April's super moon in Australia, as well as other notable celestial events this month.
What is a super moon?
The term "super moon" simply refers to a full moon at its closest point in orbit to the Earth, and it's more common than you think — there's already been two super moons this year alone, making April's one the third and final one for 2020, and the third month in a row we've had one.
The technical term for a super moon, in scientific speak, is a "perigee" or "apogee" moon.
What is a pink moon?
A pink moon is just a full moon that occurs around spring time (April) each year in the Northern Hemisphere.
Unlike a 'blood moon', which appears rusty-red, a 'pink moon' doesn't actually sport a pink hue. According to astronomer Professor Fred Watson, the name derives from North American indigenous folklore and has little basis in astronomy.
"It's spring time of course in April, and I think there's a pink moss plant that actually is one of the first things to flower."
In fact, the April full moon has been adorned with a number of colourful names over the centuries, including: sprouting grass moon, egg moon, fish moon, pesach or passover moon.
Of course, this month's will be slightly more significant as it'll be a super moon as well, and compared to previous perigee cycles, will get as close as 356,907 kms to Earth, making it one of the biggest and brightest super moons to grace our night skies this year.
Pink moon meaning
In Native American culture a pink moon signified birth and renewal, and tribes along the east coast would name the different moons for time-keeping purposes. In this way, the lunar phases would mark seasonal shifts.
When will the April super moon happen?
Although the moon will record its full phase on April 8 at 12:35pm, Prof Watson recommends peering at the sky at any time after sunset, when you'll see the moon rising.
"It will look big, but that's partly an optical illusion — it always looks big on the horizon — but that's the best time to see it because you've got a nearly full moon and nearly at it's nearest [point in orbit]."
How can Australians see the April super moon during lockdown?
With recent COVID-19 lockdown restrictions Australians won't be able to travel to view the spectacle this year. But the good news is, you don't have to worry about your location for this one — nor having to view it through a telescope, according to Prof Watson.
"The super moon will be happening throughout the night, wherever you are in Australia... a full moon is essentially in the sky all night."
However, he says that those who live inland, as opposed to on the coast, may get a better glimpse.
"A good place to go [to view it] might be away from the coast because we've got a bit of coastal cloud at the moment and, of course, if it's cloudy you won't see it at all.
"It will still look really big the night after though, but it won't be quite the full moon."
April planet alignment
There are a few notable astronomical spectacles to watch out for aside from a super moon this month, according to Prof Watson.
Planets Jupiter, Saturn and Mars will be visible in a lovely line for a week or so, from now until mid-April.
But for something extra special, you may be able to catch a glimpse of this phenomenon as the moon moves past them.
"On the 15th [of April] the moon is right next to Jupiter, on the 16th it's between Saturn and Mars — and that makes for a really nice appearance.
"For a few days either side of those dates you're going to get Jupiter, Saturn and Mars in this lovely line up in the morning sky."
So time your morning walk before the sun rises to catch this sky show.
April meteor shower
The Lyrid Meteor Shower occurs around mid-April for just over a week every year, tending to peak around April 22 or 23.
It's named after the constellation Lyra, and are credited as being among the oldest recorded meteor showers in history. This year, the shower is expected to peak from around April 23, midnight to 6am Australian Eastern Standard Time (AEST).
You don't need a telescope to view the Lyrids, just a clear sky and a secluded vantage point away from light pollution. For the most accurate radiant direction, consult timeanddate.com's Interactive Meteor Shower Sky Map.
Professor Fred Watson has launched a webinar series Cosmic Relief, with the next episode 'Should we colonise Mars?' dropping next Wednesday April 15 at 7.30am (AEST). | 0.931009 | 3.602911 |
NASA has announced a bold mission to send a nuclear-powered drone to Titan, Saturn’s largest moon, to search for evidence of life.
The drone which has eight rotors will take advantage of Titan’s dense atmosphere – four times denser than Earth’s – to become the first vehicle ever to fly its entire science payload to new places for repeatable and targeted access to surface materials.
The mission will launch in 2026 and arrive in 2034 and will fly a number of sorties exploring environments ranging from organic dunes to the floor of an impact crater where liquid water and complex organic materials that are key to life once existed, possibly tens of thousands of years ago.
Titan is of huge interest to scientists because its abundant organic material and dense atmosphere, which supports an Earth-like hydrological cycle of methane, clouds, rain and liquid flowing across the surface to fill lakes and seas. Scientists hope that studying the surface in more detail could advance our understanding of how life evolved on earth and even detect signs of past or existing life on Titan itself.
“Visiting this mysterious ocean world could revolutionise what we know about life in the universe,” said NASA Administrator Jim Bridenstine. “This cutting-edge mission would have been unthinkable even just a few years ago, but we’re now ready for Dragonfly’s amazing flight.”
The mission has used data from NASA’s Cassini probe which arrived at Titan in 2004 and made more than 100 close flybys, carrying out detailed studies of the moon’s atmosphere and mapping much of its surface.
The Dragonfly drone will initially land at the equatorial “Shangri-La” dune fields, which are similar to the linear dunes in Namibia in southern Africa. It will explore this region in short flights, building up to a series of longer “leapfrog” flights of up to five miles (8km), stopping along the way to take samples from compelling areas with diverse geography.
It will finally reach the Selk impact crater, where there is evidence of past liquid water, organics – the complex molecules that contain carbon, combined with hydrogen, oxygen, and nitrogen – and energy, which together make up the recipe for life. The lander will eventually fly more than 108 miles (175km) – nearly double the distance travelled to date by all the Mars rovers combined.
The Dragonfly drone, which is being led by scientists Johns Hopkins Applied Physics Laboratory, was selected as part of NASA’s New Frontiers program, a series of missions – aimed at advancing our understanding of the solar system. Other missions include the New Horizons mission to Pluto and the Kuiper Belt, Juno to Jupiter, and OSIRIS-REx to the asteroid Bennu. | 0.886568 | 3.703703 |
November 27, 2017 – Scientists have been studying the near-Earth environment for the better part of a century, but many mysteries — like where the energetic particles that pervade the area originate and become energized — still remain. In a new type of collaborative study, scientists combined data from 16 separate NASA and Los Alamos National Laboratory (LANL) spacecraft to understand how a particle phenomenon in the magnetic environment around Earth occurs. These events, called substorms, can cause auroras, disrupt GPS communications and, at their most intense, damage power grids.
To get a global picture, the scientists used data from four individual NASA missions — the Magnetospheric Multiscale mission, Van Allen Probes mission, Geotail, and the Time History of Events and Macroscale Interactions during Substorms mission — plus the LANL-GEO spacecraft. This research showcases how NASA heliophysics missions — heliophysics being the study of the nature of charged particles and energy in space, as well as how they are affected by the Sun — can work together.
The scientists chose an event during a quiet period in the near-Earth space environment, which they assumed would provide a simple case that would be easy to model. What they found proved otherwise.
“Even for this small event, it’s tremendously complex,” said Drew Turner, research scientist at The Aerospace Corporation in El Segundo, California. “What this shows is we don’t yet have a good global picture for what’s happening during small substorms, let alone during the big whoppers.”
Data from each individual mission is only able to provide a snapshot of what the environment looks like at a specific place and a specific time. While this allows scientists to understand some space plasma phenomena in detail, it is difficult to get a comprehensive picture of where the particles came from and where they’re going. However, by combining datasets from spacecraft situated in locations spread around Earth, Turner and his team were able to address big-picture questions about particle movement.
“Each spacecraft plays a unique role,” Turner said. “As we move forward and continue shaping the future of magnetospheric physics, the global picture of substorms and other important phenomena will become clearer as more spacecraft are deployed using innovative orbital configurations and instrumentation.”
In addition to getting a view of how complicated the system can be, the results also helped the researchers learn about substorm structure.
“We often consider substorms to be the ‘building blocks’ of the solar wind and magnetosphere interaction — the fundamental element,” said David Sibeck, THEMIS project scientist and Van Allen Probes mission scientist at NASA’s Goddard Space Flight Center in Greenbelt, Maryland. “That’s one reason why we study them.”
The researchers, using ground-based magnetometers, found a signature of what’s known as a substorm current wedge — one of the major features of a classic substorm. This result, combined with the spacecraft data, showed there is activity around Earth for more than an hour leading up to wedge formation, a process that has been hotly debated in the past. Their results have been published in the Journal of Geophysical Research.
Turner and his team are already looking at more events to see if what they’ve found in the first event is typical of substorms. Now that one of the missions — the Magneotspheric Multiscale mission — is in a new orbit that takes it father from Earth, the team expects to be able to see the point of origin of the events and hopefully capture a complete start-to-finish picture of a substom event.
The four NASA missions used in this study are a part of NASA’s Heliophysics fleet of missions under NASA’s Solar Terrestrial Probes, Living with a Star and Explorers programs, which aim to understand fundamental plasma physics questions and the dynamic Earth-Sun environment we live in. | 0.808942 | 3.730191 |
On December 2nd, Prof. Dr. Sherry Suyu (TUM Department of Physics) will give a talk entitled “New Measurement of the Universe’s Expansion Rate Using Cosmic Lenses”.
Knowing the precise value for the Hubble constant, a measure for how fast the universe expands, is important for determining the age, size and fate of our cosmos. Unravelling this mystery is one of the greatest challenges in astrophysics. Using cosmic lenses, Professor Suyu and her team determined the universe’s expansion rate, completely independent of any previous method. This latest value for the Hubble constant represents the most precise measurement yet using gravitational lensing, where the gravity of a foreground galaxy acts like a giant magnifying lens, amplifying and distorting light from background objects. Through the lensing effect, multiple images of the same background object appear around the foreground galaxy. Depending on the position of the object behind the foreground galaxy, the light of the different images has to travel over unlike distances to reach the observer. Brightness fluctuations of the background object therefore arrive at different times for each of the multiple images. The time delay can be measured in lensed quasar systems, where quasars are extremely distant cosmic streetlights produced by active black holes.
Professor Suyu and her team’s result further strengthens a troubling discrepancy between the expansion rate calculated from measurements of the local universe and the rate as predicted from background radiation of the early universe. The new study adds evidence to the idea that new theories may be needed to explain the underlying physics (TUM press release).
THE WEDNESDAY COFFEE TALKS AT THE TUM-IAS
Would you like to receive regular updates on our Wednesday Coffee Talk? Just contact us via the contact formular.
An overview on upcoming and past Wednesday Coffee Talks can be found at the Wednesday Coffee Talk Overview. | 0.868117 | 3.557625 |
Charting Young Stars’ Ultraviolet Light with Hubble
The Hubble Space Telescope’s Ultraviolet Legacy Library of Young Stars as Essential Standards (ULLYSES) is a Director’s Discretionary program of approximately 1,000 orbits that will produce an ultraviolet spectroscopic library of young high- and low-mass stars in the local universe. The ULLYSES program will uniformly sample the fundamental astrophysical parameter space for each mass regime, including spectral type, luminosity class, and metallicity for massive stars, and the mass, age, and disk accretion rate in low-mass stars. The program is expected to execute over a three-year period, from Cycle 27 to Cycle 29.
The design and targets of these observations were selected in partnership with the astronomical community, allowing researchers from around the world to help develop the final program as well as have the opportunity to organize coordinated observations by other space- and ground-based telescopes. Staff at the Space Telescope Science Institute (STScI), in charge of implementing this project, will generate public data sets and provide technical support to ensure these data enable, support, and stimulate a broad range of transformative research. The sum of these collaborative efforts will be a unique ultraviolet legacy data set with lasting value.
The ULLYSES program was specifically selected to leverage HST’s unique ultraviolet capabilities in this area of research since both high- and low-mass stars feature different complex ultraviolet emission processes that strongly impact their surroundings and are difficult to model. The ultraviolet emission from star formation is central to a wide range of vital astrophysical problems, including cosmic reionization and the formation of planets.
ULLYSES observations will be carried out over three cycles with periodic data releases as new observations are made.
|Fall 2019||Release of targets to the community|
|Spring 2020||First observations of massive stars in the Magellanic Clouds|
|Summer 2020||First data release and launch of external website|
|Fall 2020||First observations of low mass stars|
|Summer 2020 – Summer 2023||Quarterly data releases|
For inquiries, contact the ULLYSES team. | 0.83275 | 3.376734 |
After spending nearly eight years floating through deep space, NASA’s Dawn spacecraft finally reached its destination Friday, a dwarf planet in the asteroid belt called Ceres.
NASA confirmed that its spacecraft slid into dwarf planet Ceres’ orbit at 4:39 a.m. today with no complications. “Dawn” will spend the next 16 months in the dwarf planet’s gravitational pull, photographing the largest known object in the asteroid belt.
“Since its discovery in 1801, Ceres was known as a planet, then an asteroid and later a dwarf planet,” said Marc Rayman, chief engineer of director of the $473-million mission, in a statement. “Now, after a journey of 3.1 billion miles and 7.5 years, Dawn calls Ceres home.”
Video by Jet Propulsion Laboratory
After making a first stop at asteroid Vesta, another resident of the rocky belt between Mars and Jupiter, Dawn continued onward to Ceres, whose composition remained nebulous to scientists ever since the Hubble Space Telescope captured the earliest images of the dwarf planet.
“[Ceres] is sort of just staying hidden from our eyes, more than I had expected it to be,” Chris Russell, lead investigator of the mission, told the NewsHour in February.
But as Dawn edged closer to Ceres, the dwarf planet’s icy surface came into view. And what scientists saw from a distance was puzzling. A bright spot, then a smaller shiny companion, appeared on Ceres’ surface.
Last month, within 29,000 miles of the dwarf planet, Dawn revealed that Ceres’ bright white spot was actually two located in a large crater. What could the sun be reflecting off the surface of Ceres? Speculations are abound: Is it the crater of an icy volcano? A salt flat? A subsurface ocean? Until more concrete measurements become available, Ceres’ composition will remain an extraterrestrial cliffhanger.
Whatever the case, scientists do think Ceres shows signs of life-sustaining water.
“Ceres is actually the largest water reservoir in the inner solar system other than the Earth,” Jian-Yang Li, of the Planetary Science Institute in Tucson, Arizona, told Space.com.
Li said estimates water makes up nearly 40 percent of Ceres’ volume, although it’s unclear how much of the water is liquid, which is necessary for life.
Ceres, along with Vesta, is a proto-planet that can offer clues to the solar system’s beginning and understanding the formation of its larger counterparts.
Ahead of Dawn’s reappearance from Ceres’ shadow, we put together a timeline of the spacecraft’s 3-billion-mile journey. It is the first mission to reach the orbit of a dwarf planet and also the first to orbit two celestial bodies during a mission.
Dawn mission milestones and accomplishments:
Sept. 27, 2007
Dawn uses Mars to slingshot on to Vesta and Ceres, and tests its equipment.
The spacecraft returns its first pictures of Vesta.
First science data from Vesta reveals:
- One of the largest mountains in the solar system.
- The surface is much rougher than other asteroids, and there’s a greater diversity in the composition of surface
- Craters in the southern hemisphere that are 1-2 billion years old, and younger than the northern hemisphere
- Vesta’s “color palette” shows that its composition is more varied than an asteroid, but not quite like Earth or Mars. That means it represents a transitional period in the formation of our solar system.
Vesta could have ice water beneath the surface.
Dawn mission finds that Vesta is more like the Earth’s moon or an early planet than it is an asteroid. It once had a subsurface magma ocean, and about 6 percent of the meteorites on Earth came from Vesta.
August 30, 2012
Dawn leaves Vesta to head on to Ceres, and takes a good-bye shot of Vesta as it leaves.
Video by NASA Jet Propulsion Laboratory
Studying the data from Vesta further suggests that Vesta is a “stunted planet”; a planet that could have been, but was halted early in its development.
It appears to have been bombarded by other asteroids early in its life, but the shapes of its gullies, craters and troughs still leave questions for astronomers. How did they form? Why do they look different from those on the Moon or Mars?
Color-coded images of the minerals on Vesta show the proto-planet’s brilliant colors.
Dawn has mechanical problems and goes into safe mode.
Dawn gets closer to Ceres, and sees mysterious bright spots on the surface. The bright spots could be ice volcanoes, salt, surface ice or water, but until Ceres gets closer we won’t know for sure. | 0.908276 | 3.402173 |
It’s likely that sometime in your education career, an English teacher had you enjoy (or suffer through, depending on your tastes) at least part of that classic of classics, Homer’s Odyssey. It tells the story of Odysseus, a Greek general, who embarks on a 10-year journey back home after battling in the fall of Troy. The tale is filled with imagery that is referenced often in contemporary films and books. As old as it is, one would think that we’ve learned pretty much all we can from the book, but a new analysis of celestial events referenced in the Odyssey reveals that Homer may have documented a total solar eclipse.
Here’s a little background on the epic: Odysseus fights in the battle of Troy, which is believed to have occurred in approximately 1200 B.C. After the battle, he must find his way back to Ithaca in Greece, and the journey home is a harrowing one in which he is captured by the nymph Calypso, drifts on a raft at sea, battles a cyclops, resists the temptation of the Sirens and in general has hard luck. While he is away, his wife Penelope is living at his house with 108 suitors who are trying to convince her that she should accept her husband as dead and marry one of them.
Near the end of the story, a seer named Theoclymenus foretells the death of all the suitors, saying:
Poor men, what terror is this that overwhelms you so? Night shrouds your heads, your faces, down to your knees — cries of mourning are bursting into fire — cheeks rivering tears — the walls and the handsome crossbeams dripping dank with blood! Ghosts, look, thronging the entrance, thronging the court, go trooping down to the realm of death and darkness! The sun is blotted out of the sky — look there — a lethal mist spreads all across the Earth.
The reference to the Sun being blotted out of the sky on the day Odysseus returns home to retake his house and slaughter the suitors has been thought for a long time to be a reference to an actual eclipse, and was debated by astronomers, historians and classicists until it was finally decided that there was not enough evidence in the book to pinpoint a specific date for the event.
An analysis of overlooked passages in the book by Marcelo O. Magnasco, who heads the Laboratory of Mathematical Physics at Rockefeller, and Constantino Baikouzis of the Proyecto Observatorio at the Observatorio Astronómico in La Plata, Argentina reveals that there is enough evidence – if their interpretation of the events is correct – to place the eclipse on April 16th of 1178 B.C. Magnasco and Baikouzis reported their findings in this week’s Proceedings of the National Academy of Sciences.
There are four celestial clues in the Odyssey that individually happen rather often, but rarely coincide within a short period of time. As Odysseus is making his way home on a raft, he navigates by the use of the constellations Bootes and the Pleiades, which only appear together in the sky in March and September. The Moon is new when Odyesseus returns home, and on that day Venus rises before dawn, which only happens during one-third of new moons. The most important clue, though, is that Homer refers to the god Hermes flying west to the island of Ogygia about a month earlier. This reference is likely to the planet Mercury, which is low in the sky and experiences retrograde motion – seems to go backward in the sky relative to the stars – every 116 days.
Magnasco said, “Not only is this corroborative evidence that this date might be something important but if we take it as a given that the death of the suitors happened on this particular eclipse date, then everything else described in The Odyssey happens exactly as is described.”
Baikouzis and Magnasco analyzed all 1,684 new moons between 1250 and 1125 B.C. with commercial astronomy software for any dates that would match this confluence of events and came up with April 16th, 1178 B.C. Given that Homer matched the story to events in reality, this could help historians date the fall of Troy and shows that this great poet may also have had a penchant for astronomy. | 0.804788 | 3.068807 |
It has been a year now since the Dawn spacecraft first reached the dwarf planet Ceres in the main asteroid belt between Mars and Jupiter, and during that time has shown Ceres to be a unique and complex little world. At first glance, Ceres just seems to be a heavily battered place, covered in craters like the Moon or Mercury, but a closer look reveals something more interesting: a small rocky world with large fractures, unusual “bright spots” randomly dispersed across the surface and an odd conical “mountain” which sits in isolation with nothing else like it around. Dawn has already acquired an enormous amount of data about Ceres, but now, in its lowest possible orbit, will continue to do for some time to come.
The intriguing features seen on Ceres’ surface suggest that it has been, or perhaps still is, geologically active, not just a solid ball of inert rock and ice.
“Ceres has defied our expectations and surprised us in many ways, thanks to a year’s worth of data from Dawn. We are hard at work on the mysteries the spacecraft has presented to us,” said Carol Raymond, deputy principal investigator for the mission, at NASA’s Jet Propulsion Laboratory in Pasadena, Calif.
Ceres is referred to as a dwarf planet, in between large asteroids and planets, and is the largest object in the main asteroid belt.
“Ceres is so big compared to all the other asteroids that it’s really different,” said Andrew Rivkin, a planetary scientist at the Johns Hopkins University Applied Physics Laboratory in Laurel, Md. “It’s sort of the penultimate step before a planet.”
It was March 6, 2015, when Dawn first arrived at Ceres and entered orbit to begin a long study of this fascinating place. Dawn recently entered the lowest orbit that it can go – 385 kilometres (240 miles) above the surface – and the images sent back so far have been incredible.
One of the most interesting features seen is the so-called “lonely mountain,” Ahuna Mons, a conical hill which is unusual due to its appearance as well as the fact that there is nothing else like it on Ceres. Scientists do not yet know how it formed, but the newest high-resolution images of it taken by Dawn show a steeply sloped surface with a relatively flat summit. There are also numerous “ridges” of bright material running downhill. When first seen from a distance in February 2015, the mound had a bit more of a pyramid-appearing shape to it, but close-up images showed it to actually be conical. So no, not an alien base, but an intriguing feature just the same. There is a large crater adjacent to it, almost touching, which is roughly about the same size as the base of the mound, but whether it is related to the formation of the mountain is unknown. This unusual mound stands out very noticeably from the surrounding cratered, but otherwise relatively flat, terrain. Mountains of any kind weren’t really anticipated on Ceres, since it is so small and far from the Sun, with little, if any, geological activity expected to be seen.
As noted by Chris Russell, Dawn’s principal investigator at the University of California in Los Angeles: “No one expected a mountain on Ceres, especially one like Ahuna Mons. We still do not have a satisfactory model to explain how it formed.”
“As we take the highest-resolution data ever from Ceres, we will continue to examine our hypotheses and uncover even more surprises about this mysterious world,” he added.
Ahuna Mons is about 5 kilometres (3 miles) tall and 20 kilometres (12 miles) across at the base. It is higher than Mount Rainier in Washington and Mount Whitney in California, for comparison.
Some other now well-known oddities on Ceres are the “bright spots” found in various locations across the dwarf planet, with more than 130 counted so far. They stand out as white-ish against the more grey surrounding terrain. The most famous are the brightest and largest spots, in Occator crater, which can be easily seen from some distance away from Ceres. They initially appear as one or two bright spots, but when seen close-up they can be seen to consist of a cluster of multiple spots, at least 10, near the center of the crater. The others appear to be similar, but less pronounced than those in Occator.
Like the mountain, the origin of these spots is still unclear, although they do seem to be composed of salts, not water ice as first theorized. Studies of data from Dawn show that they are consistent with a type of magnesium sulfate called hexahydrite. They might be deposits left over from when briny water or ice came to the surface from below, perhaps excavated by impacts, and subsequently sublimated in the airless space around Ceres; Ceres is thought to have a water-ice mantle surrounding a rocky core. They might even be deposits from cryovolcanoes, where ice was vented to the surface geologically. Haze has been inside Occator crater, which may be related to the spots.
“The global nature of Ceres’ bright spots suggests that this world has a subsurface layer that contains briny water-ice,” said Andreas Nathues at the Max Planck Institute for Solar System Research in Göttingen, Germany. “The whole picture we do not have yet,” he added.
The images sent back by Dawn of the spots in Occator have already been fantastic, but the best ones are expected to be released sometime this month, taken from the lowest orbit. As mentioned in the Dawn twitter feed on Feb. 28:
“Re: Occator bright spots & mountain: New images are being processed and are expected next month. Stay tuned!”
The new mountain images have now been released, so it shouldn’t be too long until we have our best view so far of the bright spots in Occator.
“Dawn began mapping Ceres at its lowest altitude in December, but it wasn’t until very recently that its orbital path allowed it to view Occator’s brightest area. This dwarf planet is very large and it takes a great many orbital revolutions before all of it comes into view of Dawn’s camera and other sensors,” said Marc Rayman, Dawn’s chief engineer and mission director at JPL.
Dawn has also found ammonia on Ceres, suggesting it may have formed farther out in the Solar System before migrating inward.
From a recently published paper:
“Our measurements indicate widespread ammoniated phyllosilicates across the surface, but no detectable water ice. Ammonia, accreted either as organic matter or as ice, may have reacted with phyllosilicates on Ceres during differentiation. This suggests that material from the outer Solar System was incorporated into Ceres, either during its formation at great heliocentric distance or by incorporation of material transported into the main asteroid belt.”
As also noted by Maria Cristina De Sanctis at the National Institute of Astrophysics in Rome: “The presence of ammonia-bearing species suggests that Ceres is composed of material accreted in an environment where ammonia and nitrogen were abundant. Consequently, we think that this material originated in the outer cold Solar System.”
Dawn was the first spacecraft ever to visit a dwarf planet (before New Horizons reached Pluto) and the first to orbit two different Solar System bodies – initially the asteroid Vesta from 2011-2012 and now Ceres in 2015-2016.
Ceres will be in the news again later this month, as there will also be a press briefing on March 22 with further updates, during the 47th Lunar and Planetary Science Conference in The Woodlands, Texas.
“Ceres continues to amaze, yet puzzle us, as we examine our multitude of images, spectra and now energetic particle bursts,” said Russell.
More information about the Dawn mission is available here.
This article was first published on AmericaSpace. | 0.89806 | 3.885211 |
A new study has predated the origin of Earth’s ocean, their frozen form in lunar craters and meteorites, saying they are much older than the birth of the solar system.
The new findings have provided stronger clues over the possibility of life on other planets. The origin of water in the solar system had been largely debated by the global scientist community for a long time. The scientists worldwide have been clueless about the fact that whether water came from ice ionized at the time of the solar system formation or if they were present before the birth of the solar system and originated in the cold interstellar cloud of gas that led to the formation of the sun.
Lead study researcher Lauren Cleeves, from the University of Michigan said, “It’s remarkable that these ices survived the entire process of stellar birth.”
Cleeves has been doing rigorous research work on how radioactivity, galactic cosmic rays and other phenomena of high-energy influence planet-forming disk, contributing to the formation of celestial bodies.
Cleeves said that the study showed that the conditions in the early solar system weren’t ideal for the synthesis of new water molecules.
“Without any new water creation, the only place where these ices could have come from was the chemically rich interstellar gas that resulted into the formation of the solar system,” the researchers said.
For the study, the researchers conducted an experiment by running computer models that helped them to compare ratios of hydrogen with its heavier isotope called deuterium, which has been enriching the water on the solar system over the long period.
Concluding the study, the researchers said that in order to reach the ratios present in the ocean water of the Earth as well as samples of comets and meteorites, a huge possibility of life persists that show at least some of the water would have formed before the birth of the sun.
“Understanding the production of organic material at the early stages of star formation is critical to piecing together the gradual progression from simple molecules to potentially life-bearing chemistry,” Arnaud Belloche from Germany’s Max Planck Institute for Radio Astronomy, who conducted the study, said.
The study was detailed in were published in the latest issue of the journal Science. | 0.853059 | 3.588214 |
There are monsters lurking in space, which are called Black Holes. Anything that gets too close to a Black Hole is pulled to it with such a strong force that it has no chance of escape. The monster will gobble it up!
Even light – the fastest thing in the Universe – is doomed if it goes near one of these monsters. This is why Black Holes are black. However, they are not really holes and they are not empty. Black Holes are actually filled with a lot of material that is crammed into an extremely small region.
Astronomers know that some Black Holes are giants and that they live in the centres of most galaxies – including our own galaxy, the Milky Way! These giant monsters are called ‘Super-massive Black Holes’. Don’t panic: The Earth and the rest of our Solar System is far enough away that they are not in any danger from our galaxy’s Super-massive Black Hole.
Some of the Super-massive Black Holes don’t have any material nearby to eat. But others have a buffet table of cosmic goodies within reach. The Super-massive Black Holes that are currently eating are easier to find in the Universe, as the doomed space material shines brightly before it disappears forever into the monster’s mouth. Some galaxies that contain this type of Super-massive Black Hole are marked with red crosses in the picture above.
Astronomers had expected to find most of the monsters that are currently feeding at the centres of medium-size galaxies. However, new observations have shown that they are mostly in the centres of galaxies that are 20 times bigger than what they had expected.
This surprising discovery means that astronomers might have to go back to the blackboard and figure out why their prediction was wrong. Sometimes, even astronomers don’t get the answer right first time!
To make a small Black Hole you would have to squash something with the same mass as the Earth into a tiny ball that is only a few millimetres wide! | 0.814684 | 3.174399 |
Stars, like people, do not live forever. After a star has used up its necessary supply of hydrogen fuel in its searing-hot nuclear fusing heart, it has reached the tragic end of that long stellar road, and is about to meet its doom. Even though it is well-known that newborn baby stars, or protostars, are born surrounded by a swirling, whirling disk of planet-building gas and dust, new observations indicate that elderly stars may also be surrounded by similar 3d mink eyelashes manufacture–and may even get a second chance at having a new family of planets! In March 2016, astronomers announced that the Very Large Telescope Interferometer (VLTI) at the European Southern Observatory’s (ESO’s) Paranal Observatory in Chile has obtained the clearest view ever of the dusty disk swirling around an elderly, aging star. For the very first time such features can be compared to those surrounding baby stars–and they appear to be amazingly similar–perhaps giving the old star the opportunity to create a second generation of planet-children!Thrur
As stars come to the end of their “lives”, a large number of them form stable disks of gas and dust around them. This material is ejected by fierce stellar winds, while the elderly star is passing through the red giant phase of its evolution. These disks hauntingly resemble those that form planets orbiting young stars. But up until now, astronomers have not been able to compare the two types–one formed at the star’s birth, and the second at the end of its brilliant stellar “3d mink eyelashes manufacture”.
Even though there are numerous disks observed to be associated with baby stars that are sufficiently close to Earth for astronomers to study in depth, up until now there have been no corresponding elderly stars with disks that are close enough for detailed images to be obtained.
But this has now changed. A team of astronomers led by Dr. Michel Hillen and Dr. Hans Van Winckel of the Instituut voor Sterrenkunde in Leuven, Belgium, has used the power of the VLTI, armed with the Precision Integrated-optics Near-Infrared Imaging ExpeRiment (PIONIER) instrument, and the freshly upgraded Revolutionary Fast Low Noise Detector (RAPID) detector on PIONIER, to spy these elusive, whirling objects.
The Life And Death Of A Star
When an enormous, dark, frigid molecular cloud condenses, a rotating baby star forms within an especially dense blob embedded within the folds of the cloud. The dusty material encircling the neonatal star is also moving, and it will ultimately flatten into a pancake-like disk around the protostar’s equator. This dusty disk material is the stuff of planets, moons, asteroids, and comets!
Some astronomers suggest that planet birth can be compared to the way snowballs form. Over the passage of millions of years, tiny and inherently “sticky” dust motes merge together to create ever larger and larger objects–from boulder size, to mountain size, to moon size. At last, some of those colliding rocks grow to become planets, like our own Earth–or, alternatively, the cores of gaseous giant planets like Jupiter, Saturn, Uranus, and Neptune that reign majestically in our Solar System’s outer domain. Large objects that fail to contribute to the formation of baby planets frequently evolve into asteroids and comets.
Within the mysterious, dark, and blanketing folds of these enormous molecular clouds composed of gas and dust, fragile threads of material twist around one another and then merge together–continuing to grow ever larger and larger for hundreds of millions of years. The crush of relentless gravity, at long last, becomes so powerful that the hydrogen atoms–that are jumping around within these eerie, dense, and dark blobs–suddenly and dramatically fuse. This sets the baby star on fabulous fire, and these furious flames will 3d mink eyelashes manufacture and glare with great brilliance for as long as the star “lives”.
The process of nuclear fusion is what lights the baby star’s stellar fire. Brilliant and very, very hot protostars fight for their “lives” by balancing two eternally battling enemies in order to reach sparkling stellar adulthood. Indeed, all stars on the hydrogen-burning main-sequence of the Hertzsprung-Russell Diagram of stellar evolution, regardless of their age, must spend their “lives” maintaining a precious, precarious balance between the two enemies: gravity and radiation pressure. While the powerful, relentless pull of gravity tugs everything in, the push of radiation pressure forces everything out and away from the star! This necessary balance between the two enemies keeps the star “alive”, and on the main-sequence. Alas, stars, like people, grow old. When an elderly star has burned up its necessary supply of fuel in its nuclear-fusing heart, this core experiences an inevitable, tragic collapse–and the star perishes. Small stars, like our Sun, die with relative peacefulness–and great beauty. Small Sun-like stars gently toss their multicolored, shimmering outer gaseous layers into interstellar space. The lingering remnant core of a small Sun-like star evolves into a stellar ghost called a white dwarf. However, before the small star enters the white dwarf stage, it swells up to monstrous proportions, and becomes a red giant star. When our Sun enters its red giant stage, it will become a fiery red, enormous monstrosity, that engulfs some of its own planet-children in the seething furnace of its outer gaseous layers–first, Mercury, then Venus, and then–possibly–Earth. However, this will not happen for billions of years. Our Sun is about 4.56 billion years old, and is still a middle-aged star. Stars of our Sun’s mass “live” for about 10 billion years.
It is easier for astronomers to observe dust surrounding a star than it is for them to spot rocks or planets. Swirling dust, dancing around a distant star, blankets more area than a planet, asteroid, or comet. As the tiny dust motes absorb heat from their stellar-parent, they re-emit most of their light at long infrared wavelengths. In a way that is similar to burners on an electric stove top that turn from “red” to “white” as they grow increasingly hotter and hotter, the distant dust in a disk will possess different temperatures depending on its separation from its parent-star. This information can then be used to determine the structure and age of the disk, and provide valuable information about whether or not planets are in the process of forming–or if they have already been born. Astronomers quantify the color of the dust by measuring its spectrum, or brightness, with the heat-sensitive, infrared vision of telescopes like NASA’s Spitzer Space Telescope. Infrared detecting technologies are perfect for observing distant planet-birthing disks around distant stars, and characterizing exoplanets, which are planets belonging to a star beyond our own Sun.
Terrestrial planets–which are rocky planets like our Earth–form around many, if not most of the nearby Sun-like stars in our Milky Way Galaxy. This indicates that the potential for life might be considerably more common than once thought. Indeed, the Spitzer Space Telescope has found observational hints of planet formation around dead stars, and stars as young as a “mere” one million years old–which is very young for a star. Future 3d mink eyelashes manufacture will follow-up on many of Spitzer’s observations to determine whether planets like our own Earth exist in any of these systems.
Dusty Disks Around Old Stars May Give Them A Second Chance
The team of astronomers, who discovered the disk circling an elderly star, had targeted an old binary star system dubbed IRAS 08544-4431, which resides about 4,000 light-years from Earth in the southern constellation Vela (The Sails). This binary star is composed of a bloated red giant star, which was responsible for shedding the material in the surrounding dusty disk, and a less-evolved main-sequence, normal star orbiting close to it.
Dr. Jacques Kluska explained in a March 9, 2016 ESO Press Release that “By combining light from several telescopes of the Very Large Telescope Interferometer, we obtained an image of stunning sharpness–equivalent to what a telescope with a diameter of 150 meters would see. The resolution is so high that, for comparison, we could determine the size and shape of a one euro coin seen from a distance of two thousand kilometers.” Dr. Kluska is a team member from the University of Exeter in the United 3d mink eyelashes manufacture.
Because of the unprecedented sharpness of the images derived from the VLTI, and a new imaging technique that is able to eliminate central stars from the image to unveil what lies around them, the team could determine all of the building blocks of the IRAS 08544-4431 system for the first time.
The most prominent feature seen on the images is the clearly resolved ring. The inner edge of the dusty ring, observed for the first time, corresponds very well with the predicted beginning of the dusty disk: closer to the stellar duo, the dust would evaporate in the shower of ferocious radiation rushing out from the 3d mink eyelashes manufacture.
“We were also surprised to find a fainter glow that is probably coming from a small accretion disk around the companion star. We knew the star was double, but were’nt expecting to see the companion directly. It is really thanks to the jump in performance now provided by the new detector in PIONIER,” explained study lead author, Dr. Hillen, in the March 9, 2016 ESO Press Release.
The team discovered that the disks swirling around elderly stars are indeed very similar to the planet-birthing ones that surround young stars. Could a second generation of baby planets really be born around these old stars? That is the question, and the answer is yet to be determined. Nevertheless, it is certainly an interesting 3d mink eyelashes manufacture.
“Our observations and modeling open a new window to study the physics of these disks, as well as stellar evolution in double 3d mink eyelashes manufacture. For the first time the complex interactions between close binary systems and their dusty environments can now be resolved in space and time,” concluded Dr. Hans Van Winckel in the ESO Press Release. | 0.89414 | 3.844828 |
A quasar with the brightness of about 600 trillion suns – the brightest ever seen in the early universe – has been discovered by the Hubble Telescope.
Astronomers used data from the Nasa/European Space Agency's telescope to find the ancient quasar – the extremely bright nucleus of an active galaxy created by energy released by gas falling towards the supermassive black hole at its centre.
They believe the quasar can provide an insight into galaxies' birth, when the universe was about a billion years old.
Astronomers said it is by far the brightest quasar discovered so far in the early universe.
Catalogued as J043947.08+163415.7, it is so old the light being received from it started its journey when the universe was only about a billion years old.
In 2012 the universe was estimated to be more than 13-billion years old by Nasa's Wilkinson Microwave Anisotrophy Probe.
Astronomers said the quasar's brightness is equivalent to about 600 trillion suns, and the supermassive black hole powering it is several million times as massive as our sun.
The data shows the quasar may be producing up to 10,000 stars a year and the supermassive black hole is accreting matter to itself at an extremely high rate, scientists said.
In comparison, the Milky Way produces about one new star a year.
Lead author Xiaohui Fan, from the University of Arizona, said he did not expect to find many quasars brighter than this in the entire universe.
"That's something we have been looking for a long time," he said.
"We don't expect to find many quasars brighter than that in the whole observable universe."
Co-author Fabian Walter, of the Max Planck Institute for Astronomy in Germany, said it was a prime candidate for further investigation.
He added: "Its properties and its distance make it a prime candidate to investigate the evolution of distant quasars and the role supermassive black holes in their centres had on star formation."
Strong gravitational lensing caused by a dim galaxy between the quasar and the earth enabled the Hubble to spot the quasar, making it appear three times as large and 50 times as bright than without.
More from NASA
Data will now be gathered on the quasar with the use of the European Southern Observatory's Very Large Telescope to try to identify its chemical composition and temperatures of intergalactic gas in the early universe.
Astronomers also hope to use the Atacama Large Millimetre/Submillimetre Array and Nasa/ESA/CSA James Webb Space Telescope, which wil be launched in 2021, to look at the supermassive black hole and measure the influence of its gravity on the surrounding gas and star formation. | 0.857174 | 3.884536 |
Israelian explores distant objects in the universe using spectroscopy. By looking at the spectral signature of distant object, he can infer the qualities and behaviors of the objects. He thinks spectroscopy will be how we finally discover whether there is life elsewhere outside of our solar system.
Israelian discovered that stars sometimes swallow their planets — not by direct observation of the event, but by looking at the spectral signature of a star, which indicated that lithium was present in the star. (Lithium, we know from physics, is not normally present in stars without them having devoured another type of object.) “The power of spectroscopy was actually discovered by Pink Floyd,” he joked.
We do not yet understand the spectrum of the Sun. 15% of the spectral lines we see from the Sun are not understood.
Supernovae, the largest disasters in space, are the only places where the elements required for planets — and for life itself — are created. We owe our existence to the existence of supernovas.
A colleague showed Israelian an interesting spectrum that included a huge amount of oxygen. This amount of oxygen had never been seen before. And the conclusion was that a supernova had occurred in a star system, and that explosion had created a black hole.
Our galaxy also includes some “alien” stars — they are stars that have come from other galaxies. When galaxies collide, some stars are left behind, and spectroscopy allows us to detect which ones are “foreign.”
He also looks at a binary star with a phenomenon called a “super flare.” What causes extremely large super flares? No one knows — but he hopes that the mystery of super flares will be finally explained by spectroscopy.
But first, we need to understand the whole evolution of the universe, and how the objects have been producing and recycling various chemical elements. It’s an extraordinarily complex study, and occasionally some anomalies appear. Those anomalies, Israelian thinks, may help us discover other life elsewhere in the universe. Biomarkers such as oxygen and ozone may indicate whether a planet is hospitable to life. In fact, water and methane have already been detected on distant planets outside of our solar system.
Photo: Garik Israelian at TEDGlobal 2009, Session 6: “Curious and curiouser,” July 22, 2009, in Oxford, UK. Credit: TED / James Duncan Davidson | 0.812234 | 3.920187 |
We live in a solar system filled with water. Not only does liquid water cover 72% of our planet Earth, we have also found ice water in asteroids and comets, on the Moon, on Mars, and even in the shadows of craters on Mercury; while Europa and other moons of Jupiter and Saturn almost certainly harbor liquid oceans beneath their surfaces.
A team led by graduate student Ilse Cleeves at the University of Michigan has determined that all other planetary systems should also have water just like our solar system by investigating how the solar system was able to produce all of the water that we see in the solar system today. Simply put, it could not. There is no way the solar system could have produced all of the regular water (H2O) in the solar system, because they cannot account for the production of all of the heavy water (D2O) that we see today in our oceans. Since the solar system could not have produced it, the majority of the water in our solar system – or at the very least, a decent amount – must have been left over from before the solar system formed.
Astronomers have had two simple ideas to explain the origin of the solar system’s water. Either, our water is left over from where the Sun was born or the solar system was capable of producing that water by itself. (1) The Sun was born in a cold, giant molecular cloud. If you like astronomy pictures, you have probably seen some of these before, like the Horsehead Nebula shown above. These clouds have very rich chemistry, including water in the form of ice – very, very cold ice at temperatures of -263°C. It is possible that this water may have survived until today. (2) But, some have doubts that this water could have survived the formation of the solar system. The collapse of a cloud to form the Sun and the rest of the solar system is a very violent process that may have had the power to destroy most, if not all of the leftover cloud water. If this were true, the solar system would have to start all over and reproduce all of the water that the cloud once had.
Ilse Cleeves and her collaborators thought they could test whether the second idea is even possible since they knew that heavy water (D2O) is difficult to produce. H2O and D2O are both made up of 2 hydrogen and 1 oxygen, but the hydrogen is a little different. All hydrogen atoms have 1 proton. The fundamental properties of all atoms are determined by the number of protons they have. But, hydrogen atoms in H2O do not have any neutrons, while the two hydrogen in D2O each have 1 neutron. To distinguish the two types – or, isotopes – of hydrogen, the isotope with one neutron is called deuterium and labeled ‘D’ instead of ‘H’. Though, really it is still ‘H’ – specifically isotope ‘2H’ instead of isotope ‘1H.’ An ‘H’ atom in a molecule can always be replaced by a ‘D’ atom, but the way that ‘D’-enriched molecule can chemically react will be different. As an aside, studying isotope ratios is a common tool in science. Both ‘H’ and ‘D’ are stable. But with other atoms that have unstable isotopes, you can take advantage of knowing how quickly the isotopes radioactively decay and use the isotope ratios to figure out the ages of objects made up of those isotopes.
Where there is regular water (H2O), there is also heavy water (D2O). On Earth, roughly 1 in 6400 water molecules is not regular water, but heavy water. That is not a lot, but it is not zero either. In an 8 ounce glass of water, there are over 1024 water molecules. With 1 in 6400 of those being D2O, that is over 1020 D2O molecules – literally hundreds of billions of billions of heavy water molecules. (In general, Avagadro’s number – 6×1023 – is a good estimate of the number of molecules in most small objects you can hold in your hand.) That D2O had to come from somewhere.
H2O is relatively easy to produce. Hydrogen is the most common element in the universe, while oxygen is rather common as well. Thus, it is no surprise that water in general is very common, even if it cannot always manifest in liquid form. There are multiple ways to create H2O in the realm of interstellar space. It has one way of forming in “warm” gas at temperatures above 220 Kelvin (-53°C). It has another way of forming in “cold” gas at temperatures below 220 K. However, D2O is not so simple to produce.
Producing D2O requires 3 special conditions. (1) You need to have even “colder” gas at temperatures below 50 K (-223°C) since one of the intermediate reactions can only happen with a lot of input energy. (2) You need oxygen gas. That tends to be the easy one. (3) You need something energetic to strip electrons from molecules to make them ionized.
Producing D2O in the Sun’s birth cloud is easy since you have all 3 conditions. (1) Clouds are very, very cold at 10 K (-263°C!!). (2) You have oxygen. (3) Annoying little, but high-energy nuclei known as “cosmic rays” that exist throughout space can easily ionize molecules.
Unfortunately in the early solar system, the last condition – ionization – is not so simple. Now that you are in the solar system, the Sun does exist (unlike before) and the Sun has the power to deflect cosmic rays with the solar wind. With fewer cosmic rays, fewer molecules will end up ionized. Even worse, the early solar system is much denser than our birth cloud. If you have more molecules, a smaller percentage, or ratio, of them will be ionized. That is bad since the ratio of D2O to H2O is what matters.
Can you also produce D2O in the early solar system even with less ionization? Until this study, we did not know. This is the main question Ilse Cleeves and her collaborators wanted to answer. If the answer were to be ‘no,’ then at least some of the water would have had to come from the cold molecular cloud where the Sun was born.
Cleeves and her team simulated all major sources of ionization in the early solar system to see if D2O could be produced without cosmic rays. The Sun existing interferes with cosmic ray ionization, but its own radiation can also help ionize molecules. In the end though, this is not enough to produce all of the D2O. Even the oxygen gas from condition number 2 isn’t always free to react in the denser early solar system. From these simulations, Cleeves and her collaborators determine that at least 7% of our ocean water and at least 14% of comet water originated from the Sun’s birth cloud. Those numbers are a significant percentage, but they are conservative. Less conservative numbers suggest that up to 50% of ocean water and 100% of comet water is from our Sun’s birth cloud, originating before the solar system formed.
Planetary systems can be very different from each other. If our solar system were responsible for creating all of our water, then we may have been lucky that the right conditions occurred. However, star-forming clouds are very similar. As far as we know, there is nothing special about our Sun’s birth cloud and its chemical composition or conditions. Thus, if our birth cloud could produce a solar system with water, so could all of the other birth clouds that produced each of the thousands of planetary systems that we have already discovered as well as the ones that we have yet to discover.
There are many reasons why other planets in other solar systems may not have life, but a lack of water in the system should not be one of them.
The corresponding paper was published in Science and can be found here: http://arxiv.org/pdf/1409.7398.pdf | 0.820506 | 3.85905 |
SOMETHING is amiss with the otherwise well-behaved planets in the solar system. They all line up with each other obediently enough, but their orbital plane is slightly offset from the sun’s equator.
Now there is a clue to what caused this rebellious streak: it’s possible the baby planets strayed while trying to keep up with their jet-setting parent.
Computer simulations show that asymmetrical jets on the young sun may have pushed it around in such a way that its family of planets became tilted.
Stars are thought to form out of collapsing clouds of gas and dust. The leftover material from star formation flattens out as it spins and clumps together to make planets. We would expect this disc to settle around the star’s middle, so planets in our solar system ought to orbit in line with the sun’s equator.
Planets around other stars have been found with wildly tilted orbits, or “obliquities”. A favourite explanation is planet-on-planet violence, with bigger worlds tossing the smaller ones away and altering their own orbits.
In our backyard, though, the planets are tilted by just 6 degrees. This suggests that a gentler process must have been at work, says Fathi Namouni of the University of Nice in France. The answer may lie not in scattering planets, but in moving the sun.
Hubble observations in the past 10 years have revealed that young stars with planet-forming discs can shoot jets of material from their poles. Often one jet can carry up to twice as much material as the other. Whichever jet is stronger pushes on the star.
“It’s like you’re mounting a huge rocket on the star and accelerating it away from the disc,” Namouni says. In trying to keep up with the moving star, the disc and any young planets can end up tilted, he says.
That can’t be the whole story, though, says exoplanet expert Daniel Fabrycky of the University of California in Santa Cruz. The acceleration caused by the jets is so small – about a millionth of a metre per second squared – that the star would have to move in the same direction for a million years to create obliquity.
To complicate matters, stars’ magnetic poles switch direction regularly, which means the more powerful jet would sometimes point in the opposite direction.
However, Namouni suggests that his model can still work if the young sun flipped its poles at the same rate as the bulk of the mass in the disc orbited.
He ran 2000 supercomputer simulations of the orbits of Jupiter and Saturn, which hold most of the solar system’s planetary mass, over the lifetime of the sun. In most cases, the simulations that included the asymmetric jets produced planets with a 6-degree tilt (arxiv.org/abs/1208.1432).
No one knows why star jets are asymmetrical, and several factors, such as the sun’s polar flips, would have to be timed just right for Namouni’s model to work. But Fabrycky says the idea has merit.
“I think it’s a cool mechanism to generate obliquities,” he says.
More on these topics: | 0.883523 | 3.859717 |
When two Solar System objects arrive at their closest approach to one another as viewed from Earth, they are said to be in conjunction. This month I will examine the Moon’s close approaches to all five of the visible planets that were known to the ancients. As both the Moon and the planets are in constant motion, the actual conjunction is represented by an instant in time. Because of their slow apparent motion, the close approaches (visits?) can be observed for many hours before or after a conjunction.
As previously mentioned, the planets and the Moon never wander far from the ecliptic. One implication of this fact is that as the Moon completes its 28-day orbit around the Earth, it will be in conjunction with each of the planets once. This month, the young (thin) crescent Moon will first visit Jupiter near the western horizon in Gemini on May 3rd (closest) and 4th. Try to observe on both evenings and note that the Moon has moved eastward. Also note Jupiter’s position among Gemini’s stars, perhaps by making a sketch of Gemini that indicates Jupiter’s position. This sketch will come in handy near the end of the month.
Next up is a very interesting series of close encounters with three bright and colorful objects (Mars, Spica and Saturn) in the east at dusk on May 10th through the 14th. There are lots of things to observe over the course of these five evenings. First, the waxing gibbous Moon will grow larger each evening until it reaches full Moon on May 14th. Next, note that its location is a little farther east each evening. These two phenomena are the result of the Moon moving along its orbital path around the Earth, which changes its angle relative to the Sun. Also note that the point at which the Moon became full last month was closer to Mars (read about the lunar eclipse in April’s Scope Out), and this month the full Moon occurs closer to Saturn. This eastward slide of the full Moon from one month to the next happens because of the Earth moving along its orbital path around the Sun. And finally, note the distinct colors of the three objects: Mars is red, Spica is blue, and Saturn is yellow. The Moon will be near Mars on May 10th, and between Mars and Spica on May 11th. It will be between Spica and Saturn, but closer to Spica on the 12th, and closer to Saturn on the 13th. And finally it will be on the eastward side of Saturn on May 14th, the last evening of this string of encounters.
Another rewarding and challenging opportunity to observe the Moon arrives near month’s end as it transitions from a thin waning crescent in the eastern sky at morning, to a thin waxing crescent in the evening sky in the evening. First, observe the Moon as a thin waning crescent on the eastern horizon during its close encounter with Venus just before sunrise in the pre-dawn hours of May 25th. A careful observer might see an even thinner crescent very low on the horizon and closer to the sunrise point the next morning. After this, the Moon cannot be seen because it is lost in the Sun’s glare as it approaches new Moon (conjunction with the Sun) on May 28th. A young Moon (thin waxing crescent) emerges from the Sun’s glare on May 30th, and can be seen very low on the western horizon near Mercury. On the next evening, it will appear a little higher above the horizon, and it will once again visit Jupiter. Check the sketch that you made at the beginning of the Month. Has Jupiter moved among the stars since its last visit with the Moon on May 3rd and 4th? | 0.817286 | 3.643234 |
Diamonds In The Sky
“Most white dwarfs are made mostly of carbon and oxygen and, at that temperature (2700° Celsius),
given the density of the white dwarf, those elements would have crystallized.”
Prof. David Kaplan, University of Wisconsin-Milwaukee
“People ask me how you can really tell. Because there's no way you can go and observe it. It all boils down to chemistry.
We think we're pretty certain.”
Dr Kevin Baines, University of Wisconsin-Madison
Prof. Kaplan and his colleagues have identified the coldest, faintest white dwarf ever detected. It is an invisible
companion to a pulsar named PSR J2222-0137. Because it is practically impossible to detect this white dwarf using optical and infrared light, the researchers calculated that its temperature must be no more than 2700° Celsius, by which temperature its mostly carbon and oxygen mass would have crystallized, not unlike a diamond.
Calculations made by Dr Baines and his colleagues suggest that diamonds are likely to have formed in the atmospheres of the Solar System’s gas giants (Saturn and Jupiter), which would fall to the rocky surface like hail.
In my work I use these theories as a starting point, mimicking the promise of instant wealth typically associated with the 19th century gold rushes. The three arrow shaped neon signs – “Earth-sized Chunk of Diamond ≈8238782500000000km” (the approximate distance to PSR J2222-0137), “Diamond Hail ≈1549798272km” (the approximate distance to Saturn) and “Diamond Hail ≈777313152 km” (the approximate distance to Jupiter) - are mounted on top of celestial object trackers. When switched on, these devices begin to track the celestial objects in the sky (sometimes pointing to the ground when they are below the horizon) and point the arrows in their directions. In this way the signs always show the way to these immense treasures. That is, if the theories are correct. | 0.809946 | 3.781487 |
Since scientists have been able to send instruments into space to encounter comets and receive data directly, they have been constantly surprised and mystified, as most of what they think they know about comets and other celestial bodies is being challenged and new unexpected questions continually arise.
No less challenging are the findings of the unintentional encounter of a comet's tail by Ulysses space craft, which had previously flown through a comet's tail and failed to register what this time was registered as no less than the effects of the magnetic field of the comet. This was indicated by the ‘solar wind’ meeting a significant resistance and charge, as would be expected when the 'solar wind' encounters a magnetosphere of a planet. (See below for reference). "The region around a planet where the magnetic field is strong enough to slow down or even repel the solar wind is called the magnetosphere".
What was detected was the magnetosphere of the comet at least 160 million miles from its nucleus! This is an extraordinary revelation to scientists, since even the tail end of the magnetosphere of a decent sized planet such as Earth is nowhere near that length. And the idea that a comet has a magnetosphere challenges the foundation of what scientists believe is the cause of a magnetosphere.
Less than 50 years ago, scientists believed that the tail of the comet was formed solely by the heating of icy particles as the comet travelled closer to the sun. But the direction of the comet tail whether it was travelling toward the sun or away from the sun indicated there was some force travelling from the sun outward, pushing the tail before it, because the tail streamed away from the sun even though the comet itself was moving away from the sun. This observation led to the discovery of the `solar wind'. But what they didn't know up until now, was that the 'solar wind' met resistance of the tail of a comet so far away from its visible tail - some 160 million miles from the nucleus of the comet! This means that a magnetic field extended an enormous distance from the centre of a small chunk of material only a few kilometres in diameter!
And here again is Oahspe confirmed in the extensive advanced information provided about vortices, only a fraction of which is quoted here. A comet, being in the first stages in planetary formation, is within a vortex in the early stage when it is long and extended as in the primary vortex shown in the image below. The shape of the primary vortex is long and extended, needle-like, but the shape of a more mature vortex changes, first spiralling upon itself, winding up its tail to become conical and then globular.
Bk of Cosmogony and Prophecy, 2.
Book of Lika, 7.
||4. Then the course of Lika's airavagna changed, by his commands,
sent through the comet Yo-to-gactra, a new condensing world, already with a head of fire four thousand miles broad; a very ball of melted
corpor, whirling like the spindle of a filling spool, forever winding unto itself the wide extending nebulae (the tail). Here were coursing along, hundreds of
thousands of school-ships, with students and visitors to view the scenes,
most grand in rolling on, now round, now broken, now outstretched, this
ball of liquid fire, whirling in the vortex, thirty million miles long.
To balance against which vortex many of the ships tossed and rolled,
dangerously, had they not been in skilled hands; and, as they were,
causing millions of the students on many a ship to fear and tremble,
perceiving how helpless and stupid they were compared to the very
Gods who had them in charge.||
The ratio of Yo-to-gactra’s nucleus and tail (the nucleus being four thousand miles diameter and the tail 30 million miles long), and its tail reducing in size as it progesses in the secondary stage of a vortex, indicates its vortex would appear like that of the smaller top image in plate 26. (The two lower images being even more advanced, the cone being a side on view and the “spiral pinwheel” being a cross sectional view.)
For comparison below are some figures for the length of magnetosphere of the earth and Jupiter:
||The measurements from many space missions have been combined to reveal
that the Earth's magnetosphere is blown out by the solar wind into
a teardrop shape. The head of the drop extends only about
10 Earth radii, or about 65,000 kilometers (40,000 miles) "upwind"
toward the Sun. The tail of the drop stretches away in the direction opposite the Sun,
actually reaching beyond the Moon's orbit. This long magnetotail extends more
than 600,000 kilometers (370,000 miles) from the Earth.||
||The Galileo tour will include a large looping orbit that provides two
months in the near-planetary regions of the tail where evidence of
similar processes will be sought. (Jupiter's tail may extend as far as
Saturn, over 650 million kilometers (390 miles) distant, but Galileo will go only
about 11 million kilometers (7 million miles) down the tail.)||
The actual length of the tail of Jupiter's Magnetosphere is not known, and the estimates given for earth's vary greatly, therefore it is difficult to compare ratios as to size between earth and Jupiter, but the ratio between earth and a comet, there is such a great distance in size that the ratios are obvious. And so, the length of the magnetosphere of the comet tail being more than 160 million miles compared to earth's being estimated from 370,000 to 6 million miles in length indicates the great difference in the shape of their magnetic fields which to some extent indicate the shape of the vortex. The earth's being in the mature globular stage (beyond the Fourth Stage, as shown in Oahspe, Plate 28 [1882 Ed.])has a relatively short m'vortexya (North and South Dipole).
For the first time at a comet, researchers detected O3+ oxygen ions (atoms of oxygen with a
positive charge because they have five electrons instead of eight). This suggests that the solar wind
ions, originally missing most of their electrons, picked up some of their missing electrons when
they passed through McNaught's atmosphere. The comet served as a source of electrons, said
Michael Combi, a U-M space science professor who is an author of the paper.
SWICS also found that even at 160 million miles from the comet's
nucleus, the tail had slowed
the solar wind to half its normal speed. The solar wind would usually be about 435 miles
per second at that distance from the sun, but inside the comet's ion tail, it was less
than 249 miles per second.
"This was very surprising to me," Combi said. "Way past the orbit of Mars, the solar wind
felt the disturbance of this little comet. It will be a serious challenge for us theoreticians and
computer modelers to figure out the physics."......what happened when we caught the tail of a comet
that happened to pass very near the sun.||
Hale Bop 1997, view from Spaceshuttle Columbia | 0.862871 | 4.02199 |
Jupiter is freaking massive. It’s over 1,300 times the size of Earth. As such, it’s usually pretty easy to see in the night sky. But tonight the gas giant will show itself most brilliantly to Earth-based beings because it’s at opposition to Earth. That’s good news for amateur astronomers because it means Jupiter will be brilliant and visible from sunset to sunrise.
Opposition is the position at which Jupiter passes most closely to Earth, and tonight Earth will be directly between Jupiter and the sun. The actual moment of opposition is 6 p.m. Eastern, but fear not. Even if, at that point the sun’s not down yet where you live, Jupiter will be visible all night.
Look to the southeastern sky, and it will be the brightest object in the heavens — besides Venus and the moon — so you won’t need a telescope to see it. If you do have a telescope, though, you’ll be in for an even better view. With even a cheap telescope, you can see Jupiter’s cloud bands and the planet’s Galilean moons, Io, Europa, Ganymede, and Callisto, shifting their positions around the planet over the course of the night.
Without a telescope, Jupiter is still quite distinct, with a characteristic orangey glow. You might not be able to see its famous red spot though.
Throughout the night, Jupiter will arc high in the sky. By midnight, it will be overhead. Jupiter will be near Spica, the brightest star in the constellation Virgo, but it will shine brighter than the star. It will set around sunrise, at 6:59 a.m. Eastern.
Jupiter comes into opposition with Earth every 13 months, so each year it seems to come a month later. Last year it happened in March, and next year it will happen in May.
The planet’s position relative to Earth and the sun is what allowed NASA to capture such a great picture this week with the Hubble Space Telescope.
Tonight’s event provides a great planetary viewing opportunity, a bright spot in a shitty year for Mars viewing. And even if you miss tonight, the following week should still provide great views of Jupiter.
If you live in a city or it’s just cloudy where you live, check out the live webcast from Slooh, either on the group’s website or right here. That way you can watch Jupiter in opposition all night, from the comfort of your home, through a network of telescopes. | 0.819838 | 3.330866 |
Laying The Ground For Emirates Mars Mission
Earth and Mars have a lot more in common than you may realize. Both have polar ice caps, seasonable weather changes and observable weather patterns. The planets’ similarities and differences offer a unique research opportunity as they relate to climate change, and how each planet evolved given their unique circumstances.
The Martian atmosphere is of particular interest to the scientific community, as it relates to issues of meteorology, atmospheric origin and evolution, atmospheric dynamics, and chemical stability. The atmosphere on Mars is composed mostly of carbon dioxide and has far less pressure than that of earth – equivalent to only about 1% of Earth’s pressure at sea level. The pressure, temperature, vapour, and atmospheric composition result in a constantly dusty atmosphere.
Being able to gather and assess high quality and detailed data on critical parameters of the Martian atmosphere would allow scientists to compare Mars with Earth, which could help us understand the atmospheric evolution of not only Mars, also of Earth. That is why Mars is of particular interest to the international scientific community, and is a focus of the Emirates Mars Mission (EMM), which has a goal of sending an unmanned probe to Mars by 2020.
In response to the great scientific value of Mars and expected data produced from UAE’s successful probe, Khalifa University’s Research Center for Renewable Energy Mapping and Assessment (ReCREMA) is concentrating on the Martian lower atmosphere and meteorology as part of the center’s focus on planetary and interstellar research.
In particular, we are responding to the technical goals of the mission, which intends to use three imagers and spectrometers — Emirates eXploration imager (EXI), Emirates Mars Infrared Spectrometer (EMIRS) and Emirates Mars Ultraviolet Spectrometer (EMUS) — to characterize the state of the Martian lower atmosphere by measuring its key constituents. We are working to develop the skills and insights required to analyse the data obtained from EMM’s imagers/spectrometers. We hope to optimise the use and analysis of these data for the characterisation of the spatial structure and variability of the Martian atmospheric constituents.
The EMM instrumentation are scheduled to undertake extensive and continuous imaging of the Martian atmosphere, which would allow us to advance identification of the dust-loading mechanisms, quantification and characterisation of the mass of Martian airborne material. This would facilitate a better understanding of the color differences resulting from the solar phase angle when using reflectance spectroscopic from EMIRS and EMUS and multicolour imaging from EXI in applying corrections when inferring composition measurements.
The temperature profiles of Martian latitudes throughout its seasons will also be obtained, which, when analysed and integrated with analog, seasonal and spatial thermal tidal amplitudes, can be synthesized into Mars global climate and circulation models. Data that will be obtained over continuous and long periods of time would inform on the interannual climatic variability, quasi-periodic climate variations, and long-term climate change. This would result in an improved knowledge of the Martian climate, which is expected to significantly improve predictions of Mars’ atmospheric circulation and meteorology.
Our goal is to build local capacity in atmospheric modelling methodologies for the Martian lower atmosphere, to extend the satellite image processing knowledge developed at Khalifa University to the specific characteristics the Martian land cover and atmosphere. Given the in-house expertise developed at ReCREMA in dust mapping and modelling, special focus has also been given to broaden the acquired knowledge to the modelling of dust storms on planet Mars and relate them to the surface mineralogy and meteorology.
By developing these capabilities, the planetary and interstellar research at the ReCREMA is expected to contribute to the development of the science and technology sector in the UAE and enhance UAE’s contribution to the international and global space science community. | 0.866788 | 3.771538 |
Subsets and Splits
No community queries yet
The top public SQL queries from the community will appear here once available.