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- Space elevator
A space elevator is a proposed non-rocket spacelaunch structure (a structure designed to transport material from a celestial body's surface into space). Many elevator variants have been suggested, all of which involve travelling along a fixed structure instead of using rocket-powered space launch, most often a cable that reaches from the surface of the Earth on or near the equator to geostationary orbit (GSO) and a counterweight outside of the geostationary orbit.
Discussion of a space elevator dates back to 1895 when Konstantin Tsiolkovsky proposed a free-standing "Tsiolkovsky Tower" reaching from the surface of Earth to geostationary orbit 35,786 km (22,236 mi) up. Like all buildings, Tsiolkovsky's structure would be under compression, supporting its weight from below. Since 1959, most ideas for space elevators have focused on purely tensile structures, with the weight of the system held up from above. In the tensile concepts, a space tether reaches from a large mass (the counterweight) beyond geostationary orbit to the ground. This structure is held in tension between Earth and the counterweight like a guitar string held taut. Space elevators have also sometimes been referred to as beanstalks, space bridges, space lifts, space ladders, skyhooks, orbital towers, or orbital elevators.
While some variants of the space elevator concept are technologically feasible, current technology is not capable of manufacturing tether materials that are sufficiently strong and light to build an Earth-based space elevator of the geostationary orbital tether type. Recent concepts for a space elevator are notable for their plans to use carbon nanotube or boron nitride nanotube based materials as the tensile element in the tether design, since the measured strength of carbon nanotubes appears great enough to make this possible. Technology as of 1978 could produce elevators for locations in the solar system with weaker gravitational fields, such as the Moon or Mars.
For human riders on an Earth-based elevator, adequate protection against radiation would likely need to be provided, depending on the transit time through the Van Allen belts. At the transit times expected for early systems, radiation due to the Van Allen belts would, if unshielded, give a dose well above permitted levels.
- 1 Geostationary orbital tethers
- 2 History
- 3 Physics of space elevators
- 4 Structure
- 5 Alternative concepts
- 6 Launching into deep space
- 7 Extraterrestrial elevators
- 8 Construction
- 9 See also
- 10 References
- 11 Further reading
- 12 External links
Geostationary orbital tethers
This concept, also called an orbital space elevator, geostationary orbital tether, or a beanstalk, is a subset of the skyhook concept, and is what people normally think of when the phrase 'space elevator' is used (although there are variants).
Construction would be a large project: the minimum length of an Earth-based space elevator is well over 36,000 km (22,369 mi) long. The tether would have to be built of a material that could endure tremendous stress while also being light-weight, cost-effective, and manufacturable in great quantities. Materials currently available do not meet these requirements, although carbon nanotube technology shows great promise. As with all leading-edge engineering projects, other novel engineering problems would also have to be solved to make a space elevator practical, and there are problems regarding feasibility that have yet to be addressed.
The key concept of the space elevator appeared in 1895 when Russian scientist Konstantin Tsiolkovsky was inspired by the Eiffel Tower in Paris to consider a tower that reached all the way into space, built from the ground up to an altitude of 35,790 kilometers (22,238 mi) above sea level (geostationary orbit). He noted that a "celestial castle" at the top of such a spindle-shaped cable would have the "castle" orbiting Earth in a geostationary orbit (i.e. the castle would remain over the same spot on Earth's surface).
Since the elevator would attain orbital velocity as it rode up the cable, an object released at the tower's top would also have the orbital velocity necessary to remain in geostationary orbit. Unlike more recent concepts for space elevators, Tsiolkovsky's (conceptual) tower was a compression structure, rather than a tension (or "tether") structure.
Building a compression structure from the ground up proved an unrealistic task as there was no material in existence with enough compressive strength to support its own weight under such conditions. In 1959 another Russian scientist, Yuri N. Artsutanov, suggested a more feasible proposal. Artsutanov suggested using a geostationary satellite as the base from which to deploy the structure downward. By using a counterweight, a cable would be lowered from geostationary orbit to the surface of Earth, while the counterweight was extended from the satellite away from Earth, keeping the cable constantly over the same spot on the surface of the Earth. Artsutanov's idea was introduced to the Russian-speaking public in an interview published in the Sunday supplement of Komsomolskaya Pravda in 1960, but was not available in English until much later. He also proposed tapering the cable thickness so that the stress in the cable was constant—this gives a thin cable at ground level, thickening up towards GSO.
In 1966, Isaacs, Vine, Bradner and Bachus, four American engineers, reinvented the concept, naming it a "Sky-Hook," and published their analysis in the journal Science. They decided to determine what type of material would be required to build a space elevator, assuming it would be a straight cable with no variations in its cross section, and found that the strength required would be twice that of any existing material including graphite, quartz, and diamond.
In 1975 an American scientist, Jerome Pearson, reinvented the concept yet again, publishing his analysis in the journal Acta Astronautica. He designed a tapered cross section that would be better suited to building the elevator. The completed cable would be thickest at the geostationary orbit, where the tension was greatest, and would be narrowest at the tips to reduce the amount of weight per unit area of cross section that any point on the cable would have to bear. He suggested using a counterweight that would be slowly extended out to 144,000 kilometers (90,000 miles, almost half the distance to the Moon) as the lower section of the elevator was built. Without a large counterweight, the upper portion of the cable would have to be longer than the lower due to the way gravitational and centrifugal forces change with distance from Earth. His analysis included disturbances such as the gravitation of the Moon, wind and moving payloads up and down the cable. The weight of the material needed to build the elevator would have required thousands of Space Shuttle trips, although part of the material could be transported up the elevator when a minimum strength strand reached the ground or be manufactured in space from asteroidal or lunar ore.
In 1977, Hans Moravec published an article called "A Non-Synchronous Orbital Skyhook", in which he proposed an alternative space elevator concept, using a rotating cable, in which the rotation speed exactly matches the orbital speed in such a way that the instantaneous velocity at the point where the cable was at the closest point to the Earth was zero. This concept is an early version of a space tether transportation system.
In 1979, space elevators were introduced to a broader audience with the simultaneous publication of Arthur C. Clarke's novel, The Fountains of Paradise, in which engineers construct a space elevator on top of a mountain peak in the fictional island country of Taprobane (loosely based on Sri Lanka, albeit moved south to the Equator), and Charles Sheffield's first novel, The Web Between the Worlds, also featuring the building of a space elevator. Three years later, in Robert A. Heinlein's 1982 novel Friday the principal character makes use of the "Nairobi Beanstalk" in the course of her travels. In Kim Stanley Robinson's 1993 novel Red Mars, colonists build a space elevator on Mars that allows both for more colonists to arrive and also for natural resources mined there to be able to leave for Earth. In David Gerrold's 2000 novel, Jumping Off The Planet, a family excursion up the Ecuador "beanstalk" is actually a child-custody kidnapping. Gerrold's book also examines some of the industrial applications of a mature elevator technology.
After the development of carbon nanotubes in the 1990s, engineer David Smitherman of NASA/Marshall's Advanced Projects Office realized that the high strength of these materials might make the concept of an orbital skyhook feasible, and put together a workshop at the Marshall Space Flight Center, inviting many scientists and engineers to discuss concepts and compile plans for an elevator to turn the concept into a reality. The publication he edited, compiling information from the workshop, "Space Elevators: An Advanced Earth-Space Infrastructure for the New Millennium", provides an introduction to the state of the technology at the time, and summarizes the findings.
Another American scientist, Bradley C. Edwards, suggested creating a 100,000 km (62,000 mi) long paper-thin ribbon using a carbon nanotube composite material. He chose a ribbon type structure rather than a cable because that structure might stand a greater chance of surviving impacts by meteoroids. Supported by the NASA Institute for Advanced Concepts, Edwards' work was expanded to cover the deployment scenario, climber design, power delivery system, orbital debris avoidance, anchor system, surviving atomic oxygen, avoiding lightning and hurricanes by locating the anchor in the western equatorial Pacific, construction costs, construction schedule, and environmental hazards. The largest holdup to Edwards' proposed design is the technological limit of the tether material. His calculations call for a fiber composed of epoxy-bonded carbon nanotubes with a minimal tensile strength of 130 GPa (19 million psi) (including a safety factor of 2); however, tests in 2000 of individual single-walled carbon nanotubes (SWCNTs), which should be notably stronger than an epoxy-bonded rope, indicated the strongest measured as 52 GPa (7.5 million psi). Multi-walled carbon nanotubes have been measured with tensile strengths up to 63 GPa (9 million psi).
To speed space elevator development, proponents are planning several competitions, similar to the Ansari X Prize, for relevant technologies. Among them are Elevator:2010, which will organize annual competitions for climbers, ribbons and power-beaming systems, the Robogames Space Elevator Ribbon Climbing competition, as well as NASA's Centennial Challenges program, which, in March 2005, announced a partnership with the Spaceward Foundation (the operator of Elevator:2010), raising the total value of prizes to US$400,000. The first European Space Elevator Challenge (EuSEC) to establish a climber structure took place in August 2011.
In 2005, "the LiftPort Group of space elevator companies announced that it will be building a carbon nanotube manufacturing plant in Millville, New Jersey, to supply various glass, plastic and metal companies with these strong materials. Although LiftPort hopes to eventually use carbon nanotubes in the construction of a 100,000 km (62,000 mi) space elevator, this move will allow it to make money in the short term and conduct research and development into new production methods. The goal was a space elevator launch in 2010."[dated info] On February 13, 2006 the LiftPort Group announced that, earlier the same month, they had tested a mile of "space-elevator tether" made of carbon-fiber composite strings and fiberglass tape measuring 5 cm (2 in) wide and 1 mm (approx. 6 sheets of paper) thick, lifted with balloons.
In 2007, Elevator:2010 held the 2007 Space Elevator games, which featured US$500,000 awards for each of the two competitions, (US$1,000,000 total) as well as an additional US$4,000,000 to be awarded over the next five years for space elevator related technologies. No teams won the competition, but a team from MIT entered the first 2-gram (0.07 oz), 100% carbon nanotube entry into the competition. Japan held an international conference in November 2008 to draw up a timetable for building the elevator.
In 2008 the book "Leaving the Planet by Space Elevator", by Dr. Brad Edwards and Philip Ragan, was published in Japanese and entered the Japanese best seller list. This has led to a Japanese announcement of intent to build a Space Elevator at a projected price tag of a trillion yen (£5 billion/ $8 billion). In a report by Leo Lewis, Tokyo correspondent of The Times newspaper in England, plans by Shuichi Ono, chairman of the Japan Space Elevator Association, are unveiled. Lewis says: "Japan is increasingly confident that its sprawling academic and industrial base can solve those [construction] issues, and has even put the astonishingly low price tag of a trillion yen (£5 billion/ $8 billion) on building the elevator. Japan is renowned as a global leader in the precision engineering and high-quality material production without which the idea could never be possible." In 2011, Google was revealed to be working on plans for a space elevator at its secretive Google X Lab location.
Physics of space elevators
Apparent gravitational field
A space elevator cable rotates along with the rotation of the Earth. Objects fastened to the cable will experience upward centrifugal force that opposes some, all, or more than, the downward gravitational force at that point. The higher up the cable, the stronger is the upward centrifugal force and the more it opposes the downward gravity. Eventually it becomes stronger than gravity above the geosynchronous level. Along the length of the cable, this (downward) actual gravity minus the (upward) centrifugal force is called the apparent gravitational field.
The apparent gravitational field can be represented this way:
- The downward force of actual gravity decreases with height:
- The upward centrifugal force due to the planet's rotation increases with height:
- Together, the apparent gravitational field is the sum of the two:
- g is the acceleration of actual gravity or apparent gravity down (negative) or up (positive) along the vertical cable (m s−2),
- a is the centrifugal acceleration up (positive) along the vertical cable (m s−2),
- G is the gravitational constant (m3 s−2 kg−1)
- M is the mass of the Earth (kg)
- r is the distance from that point to Earth's center (m),
- ω is Earth's rotation speed (radian/s).
At some point up the cable, the two terms (downward gravity and upward centrifugal force) equal each other, objects fixed to the cable there have no weight on the cable. This occurs at the level of the stationary orbit. This level (r1) depends on the mass of the planet and its rotation rate. Setting actual gravity and centrifugal acceleration equal to each other gives:
On Earth, this level is 35,786 km (22,236 mi) above the surface, the level of geostationary orbit.
Seen from a geosynchronous station, any object dropped off the tether from a point closer to Earth will initially accelerate downward. If dropped from any point above a geosynchronous station, the object would initially accelerate up toward space.
Historically, the main technical problem has been considered the ability of the cable to hold up, with tension, the weight of itself below any particular point. The vertical point with the greatest tension on a space elevator cable is at the level of geostationary orbit, 35,786 km (22,236 mi) above the Earth's equator. This means that the cable material combined with its design must be strong enough to hold up the weight of its own mass from the surface up to 35,786 km. By making any cable larger in cross section at this level compared to at the surface, it can better hold up a longer length of itself. For a space elevator cable, an important design factor in addition to the material is how the cross section area tapers down from the maximum at 35,786 km to the minimum at the surface. To maximize strength of the cable compared to its weight, the cross section area will need to be designed in such a way that at any given point, it is proportional to the force it has to withstand. For such an idealized design without climbers attached, without thickening at high space-junk altitudes, etc., the cross-section will follow this differential equation:
- g is the acceleration along the radius (m·s−2),
- S is the cross-area of the cable at any given point r, (m2) and dS its variation (m2 as well),
- ρ is the density of the material used for the cable (kg·m−3).
- σ is the stress the cross-section area can bear without yielding (N·m−2=kg·m−1·s−2), its elastic limit.
The value of g is given by the first equation, which yields:
the variation being taken between r1 (geostationary) and r0 (ground).
It turns out that between these two points, this quantity can be expressed simply as: , or
where is the ratio between the centrifugal force on the equator and the gravitational force.
The second technical problem is that the g0 r0 factor is quite large. Since its influence on the maximal cross-section is exponential, one needs to find materials where σ will be large enough to cancel our gravity. On Earth, we have:
- (or Joules per kg)
- for most solid materials, so that σ needs to be:
This corresponds to a cable capable of sustaining 30 tons with a cross-section of one square millimeter, under Earth's gravity.
The free breaking length can be used to compare materials: it is the length of a un-tapered cylindrical cable at which it will break under its own weight under constant gravity. For a given material, that length is σ/ρ/g0. The free breaking length needed is given by the equation
- , where
If one does not take into account the x factor (which reduces the strength needed by about 30%), this equation also says that the section ratio equals e (exponential one) when:
If the material can support a free breaking length of only one tenth this, the section needed at a geosynchronous orbit will be e10 times the ground section, which is more than a hundredfold in diameter.
There are a variety of space elevator designs. Almost every design includes a base station, a cable, climbers, and a counterweight. Earth's rotation creates upward centrifugal force on the counterweight. The counterweight is held down by the cable while the cable is held up and taut by the counterweight. The base station anchors the whole system to the surface of the Earth. Climbers climb up and down the cable with cargo.
The base station designs typically fall into two categories—mobile and stationary. Mobile stations are typically large oceangoing vessels. Stationary platforms would generally be located in high-altitude locations, such as on top of mountains, or even potentially on high towers.
Mobile platforms have the advantage of being able to maneuver to avoid high winds, storms, and space debris. While stationary platforms don't have these advantages, they typically would have access to cheaper and more reliable power sources, and require a shorter cable. While the decrease in cable length may seem minimal (no more than a few kilometers), the cable thickness could be reduced over its entire length, significantly reducing the total weight.
A space elevator cable must carry its own weight as well as the (smaller) weight of climbers. The required strength of the cable will vary along its length, since at various points it has to carry the weight of the cable below, or provide a centripetal force to retain the cable and counterweight above. In a 1998 report, NASA researchers noted that "maximum stress [on a space elevator cable] is at geosynchronous altitude so the cable must be thickest there and taper exponentially as it approaches Earth. Any potential material may be characterized by the taper factor – the ratio between the cable's radius at geosynchronous altitude and at the Earth's surface."
The cable must be made of a material with a large tensile strength/density ratio. For example, the Edwards space elevator design assumes a cable material with a specific strength of at least 100,000 kN/(kg/m). This value takes into consideration the entire weight of the space elevator. A space elevator would need a material capable of sustaining a length of 4,960 kilometers (3,080 mi) of its own weight at sea level to reach a geostationary altitude of 35,786 km (22,236 mi) without tapering and without breaking. Therefore, a material with very high strength and lightness is needed.
For comparison, metals like titanium, steel or aluminium alloys have breaking lengths of only 20–30 km. Modern fibre materials such as kevlar, fibreglass and carbon/graphite fibre have breaking lengths of 100–400 km. Quartz fibers have an advantage that they can be drawn to a length of hundreds of kilometers even with the present-day technology. Nanoengineered materials such as carbon nanotubes and, more recently discovered, graphene ribbons (perfect two-dimensional sheets of carbon) are expected to have breaking lengths of 5000–6000 km at sea level, and also are able to conduct electrical power.
Carbon is such a good candidate material (for high specific strength) because, as only the 6th element in the periodic table, it has very few of the nucleons which contribute most of the dead weight of any material (whereas most of the interatomic bonding forces are contributed by only the outer few electrons); the challenge now remains to extend to macroscopic sizes the production of such material that are still perfect on the microscopic scale (as microscopic defects are most responsible for material weakness). The current (2009) carbon nanotube technology allows growing tubes up to a few tens of centimeters only.
A space elevator cannot be an elevator in the typical sense (with moving cables) due to the need for the cable to be significantly wider at the center than the tips. While various designs employing moving cables have been proposed, most cable designs call for the "elevator" to climb up a stationary cable.
Climbers cover a wide range of designs. On elevator designs whose cables are planar ribbons, most propose to use pairs of rollers to hold the cable with friction.
Climbers must be paced at optimal timings so as to minimize cable stress and oscillations and to maximize throughput. Lighter climbers can be sent up more often, with several going up at the same time. This increases throughput somewhat, but lowers the mass of each individual payload.
The horizontal speed of each part of the cable increases with altitude, proportional to distance from the center of the Earth, reaching orbital velocity at geostationary orbit. Therefore as a payload is lifted up a space elevator, it needs to gain not only altitude but angular momentum (horizontal speed) as well. This angular momentum is taken from the Earth's own rotation. As the climber ascends it is initially moving slightly more slowly than the cable that it moves onto (Coriolis force) and thus the climber "drags" on the cable.
The overall effect of the centrifugal force acting on the cable causes it to constantly try to return to the energetically favourable vertical orientation, so after an object has been lifted on the cable the counterweight will swing back towards the vertical like an inverted pendulum. Space elevators and their loads will be designed so that the center of mass is always well-enough above the level of geostationary orbit to hold up the whole system. Lift and descent operations must be carefully planned so as to keep the pendulum-like motion of the counterweight around the tether point under control.
By the time the payload has reached GEO the angular momentum (horizontal speed) is enough that the payload is in orbit.
The opposite process would occur for payloads descending the elevator, tilting the cable eastwards and insignificantly increasing Earth's rotation speed.
It has also been proposed to use a second cable attached to a platform to lift payload up the main cable, since the lifting device would not have to deal with its own weight against Earth's gravity. Out of the many proposed theories, powering any lifting device also continues to present a challenge.
Another design constraint will be the ascending speed of the climber. As geosynchronous orbit is at 35,786 km (22,236 mi), assuming the climber can reach the speed of a very fast car or train of 300 km/h (180 mph) it will take 5 days to climb to geosynchronous orbit.
Both power and energy are significant issues for climbers—the climbers need to gain a large amount of potential energy as quickly as possible to clear the cable for the next payload.
Various methods have been proposed to get that energy to the climber:
- Transfer the energy to the climber through wireless energy transfer while it is climbing.
- Transfer the energy to the climber through some material structure while it is climbing.
- Store the energy in the climber before it starts – requires an extremely high specific energy such as nuclear energy.
- Solar power – power compared to the weight of panels limits the speed of climb.
Wireless energy transfer such as laser power beaming is currently considered the most likely method. Using megawatt powered free electron or solid state lasers in combination with adaptive mirrors approximately 10 m (33 ft) wide and a photovoltaic array on the climber tuned to the laser frequency for efficiency. For climber designs powered by power beaming, this efficiency is an important design goal. Unused energy must be re-radiated away with heat-dissipation systems, which add to weight.
Yoshio Aoki, a professor of precision machinery engineering at Nihon University and director of the Japan Space Elevator Association, suggested including a second cable and using the conductivity of carbon nanotubes to provide power.
Various mechanical means of applying power have also been proposed; such as moving, looped or vibrating cables.
Several solutions have been proposed to act as a counterweight:
- a heavy, captured asteroid;
- a space dock, space station or spaceport positioned past geostationary orbit; or
- a further upward extension of the cable itself so that the net upward pull is the same as an equivalent counterweight;
- parked spent climbers that had been used to thicken the cable during construction, other junk, and material lifted up the cable for the purpose of increasing the counterweight.
Extending the cable has the advantage of some simplicity of the task and the fact that a payload that went to the end of the counterweight-cable would acquire considerable velocity relative to the Earth, allowing it to be launched into interplanetary space. Its disadvantage is the need to produce greater amounts of cable material as opposed to using anything that has mass.
The original concept envisioned by Tsiolkovsky was a compression structure, a concept similar to an aerial mast. While such structures might reach the agreed altitude for space (100 km—62 mi), they are unlikely to reach geostationary orbit. The concept of a Tsiolkovsky tower combined with a classic space elevator cable has been suggested.
A mini version of the Space Elevator to access near-space altitudes of 20 km (12 mi) has been proposed by Canadian researchers. The structure would be pneumatically supported and free standing with control systems guiding the structure's center of mass. Proposed uses include tourism and commerce, communications, wind generation and low-cost space launch.
Launching into deep space
An object attached to a space elevator at a radius of approximately 53,100 km will be at escape velocity when released. Transfer orbits to the L1 and L2 Lagrangian points can be attained by release at 50,630 and 51,240 km, respectively, and transfer to lunar orbit from 50,960 km.
The velocities that might be attained at the end of Pearson's 144,000 km (89,000 mi) cable can be determined. The tangential velocity is 10.93 kilometers per second (6.79 mi/s), which is more than enough to escape Earth's gravitational field and send probes at least as far out as Jupiter. Once at Jupiter, a gravitational assist maneuver permits solar escape velocity to be reached.
A space elevator could also be constructed on other planets, asteroids and moons.
A Martian tether could be much shorter than one on Earth. Mars' surface gravity is 38% of Earth's, while it rotates around its axis in about the same time as Earth. Because of this, Martian areostationary orbit is much closer to the surface, and hence the elevator would be much shorter. Current materials are already sufficiently strong to construct such an elevator. However, building a Martian elevator would be complicated by the Martian moon Phobos, which is in a low orbit and intersects the Equator regularly (twice every orbital period of 11 h 6 min).[original research?]
A lunar space elevator can possibly be built with currently available technology about 50,000 kilometers (31,000 mi) long extending through the Earth-Moon L1 point from an anchor point near the center of the visible part of Earth's moon. However, the lack of an atmosphere allows for other, perhaps better, alternatives to rockets, such as mass driver systems.
On the far side of the moon, a lunar space elevator would need to be very long (more than twice the length of an Earth elevator) but due to the low gravity of the Moon, can be made of existing engineering materials.
Rapidly spinning asteroids or moons could use cables to eject materials to convenient points, such as Earth orbits; or conversely, to eject materials to send the bulk of the mass of the asteroid or moon to Earth orbit or a Lagrangian point. Freeman Dyson, a physicist and mathematician, has suggested using such smaller systems as power generators at points distant from the Sun where solar power is uneconomical. For the purpose of mass ejection, it is not necessary to rely on the asteroid or moon to be rapidly spinning. Instead of attaching the tether to the equator of a rotating body, it can be attached to a rotating hub on the surface. This was suggested in 1980 as a "Rotary Rocket" by Pearson and described very succinctly on the Island One website as a "Tapered Sling".
A space elevator using presently available engineering materials could be constructed between mutually tidally locked worlds, such as Pluto and Charon or the components of binary asteroid Antiope, with no terminus disconnect, according to Francis Graham of Kent State University. However, spooled variable lengths of cable must be used due to ellipticity of the orbits.
The construction of a space elevator is considered to be a large project. Like other historical large projects it entails technical risk: some advances in engineering, manufacturing and physical technology are required. Once a first space elevator is built, the second one and all others would have the use of the previous ones to assist in construction, making their costs considerably cheaper. Such follow-on space elevators would also benefit from the great reduction in technical risk achieved by the construction of the first space elevator.
Construction is conceived as the deployment of a long cable from a large spool. The spool is initially parked in a geostationary orbit above the planned anchor point. When a long cable is dropped "down" (toward Earth), it must be balanced by balancing mass being dropped "up" (away from Earth) for the whole system to remain on the geosynchronous orbit. Some designs imagine the balancing mass being another cable (with counterweight) extending upward, other designs elevate the spool itself as the main cable is paid out. When the lower end of the cable is so long as to reach the Earth, it can be anchored at some place. Once anchored, the center of mass is elevated upward more (by adding mass at the upper end or by paying out more cable). This adds more tension to the whole cable, which can then be used as an elevator cable.
Safety issues and construction challenges
Depending on transit times through the Van Allen radiation belts passengers will need to be protected from radiation by shielding, which adds mass to the climber and decreases payload. For early systems, transit times are expected to be long enough where, if unshielded, total exposure would be above levels considered safe.
A space elevator would present a navigational hazard, both to aircraft and spacecraft. Aircraft could be diverted by air-traffic control restrictions. All objects in stable orbits that have perigee below the maximum altitude of the cable that are not synchronous with the cable will impact the cable eventually, unless avoiding action is taken. For spacecraft one potential solution proposed by Edwards is to use a movable anchor (a sea anchor) to allow the tether to "dodge" any space debris large enough to track.
Impacts by space objects such as meteoroids, micrometeorites and orbiting man-made debris, pose another design constraint on the cable. A cable would need to be designed to maneuver out of the way of debris, or absorb impacts of small debris without breaking.
With a space elevator, materials might be sent into orbit at a fraction of the current cost. As of 2000, conventional rocket designs cost about $11,000 per pound ($25,000 per kilogram) for transfer to geostationary orbit. Current proposals envision payload prices starting as low as $100 per pound ($220 per kilogram), similar to the $5–$300/kg estimates of the Launch loop, but higher than the $310/ton to 500 km orbit quoted to Dr. Jerry Pournelle for an orbital airship system.
Philip Ragan, co-author of the book "Leaving the Planet by Space Elevator", states that "The first country to deploy a space elevator will have a 95 percent cost advantage and could potentially control all space activities."
- Elevator:2010 – a space elevator prize competitions
- Lunar space elevator for the moon variant
- Space elevator construction discusses alternative construction methods of a space elevator.
- Space elevator economics discusses capital and maintenance costs of a space elevator.
- Space elevator safety discusses safety aspects of space elevator construction and operation.
- Space elevators in fiction
- Tether propulsion – for other transportation methods using long cables
- Non-rocket spacelaunch:
- Launch loop – a hypervelocity belt system that forms a launch track at 80 km
- Lightcraft – an alternative method for moving materials or people
- Space gun or StarTram – among methods for launching materials
- Space fountain – very tall structures using fast moving masses to hold it up
- SpaceShaft – A atmospherically buoyant spar that could reach up to LEO and provide super-heavy lifting capacity.
- ^ Hirschfeld, Bob (2002-01-31). "Space Elevator Gets Lift". TechTV. G4 Media, Inc.. Archived from the original on 2005-06-08. http://web.archive.org/web/20050608080057/http://www.g4tv.com/techtvvault/features/35657/Space_Elevator_Gets_Lift.html. Retrieved 2007-09-13. "The concept was first described in 1895 by Russian author K.E. Tsiolkovsky in his "Speculations about Earth and Sky and on Vesta.""
- ^ Bradley C. Edwards IAC-04-IAA.3.8.2.01. THE SPACE ELEVATOR DEVELOPMENT PROGRAM
- ^ Non-Synchronous Orbital Skyhooks for the Moon and Mars with Conventional Materials Hans Moravec 1978
- ^ a b "Space elevators: 'First floor, deadly radiation!'". New Scientist. Reed Business Information Ltd.. 13 November 2006. http://www.newscientist.com/article/dn10520. Retrieved Jan 2, 2010.
- ^ a b "The Audacious Space Elevator". NASA Science News. http://science.nasa.gov/headlines/y2000/ast07sep_1.htm. Retrieved 2008-09-27.
- ^ a b c Geoffrey A. Landis and Craig Cafarelli (1999). Presented as paper IAF-95-V.4.07, 46th International Astronautics Federation Congress, Oslo Norway, 2–6 October 1995. "The Tsiolkovski Tower Reexamined". Journal of the British Interplanetary Society 52: 175–180.
- ^ Artsutanov, Yu (1960). "To the Cosmos by Electric Train" (PDF). Young Person's Pravda. http://www.liftport.com/files/Artsutanov_Pravda_SE.pdf. Retrieved 2006-03-05.
- ^ Isaacs, J. D.; A. C. Vine, H. Bradner and G. E. Bachus (1966). "Satellite Elongation into a True 'Sky-Hook'". Science 11 (3711): 682. Bibcode 1966Sci...151..682I. doi:10.1126/science.151.3711.682.
- ^ J. Pearson (1975). "The orbital tower: a spacecraft launcher using the Earth's rotational energy" (PDF). Acta Astronautica 2 (9–10): 785–799. doi:10.1016/0094-5765(75)90021-1. http://www.star-tech-inc.com/papers/tower/tower.pdf.
- ^ Hans P. Moravec, "A Non-Synchronous Orbital Skyhook," Journal of the Astronautical Sciences, Vol. 25, October–December 1977
- ^ Science @ NASA, Audacious & Outrageous: Space Elevators, September 2000
- ^ "Space Elevators: An Advanced Earth-Space Infrastructure for the New Millennium". http://www.affordablespaceflight.com/spaceelevator.html.
- ^ Bradley Edwards, Eureka Scientific, NIAC Phase I study
- ^ Bradley Edwards, Eureka Scientific, NIAC Phase II study
- ^ Yu, Min-Feng; Files, Bradley S.; Arepalli, Sivaram; Ruoff, Rodney S. (2000). "Tensile Loading of Ropes of Single Wall Carbon Nanotubes and their Mechanical Properties". Physical Review Letters 84 (24): 5552–5555. Bibcode 2000PhRvL..84.5552Y. doi:10.1103/PhysRevLett.84.5552. PMID 10990992.
- ^ Min-Feng Yu, Oleg Lourie, Mark J. Dyer, Katerina Moloni, Thomas F. Kelly, Rodney S. Ruoff (2000). "Strength and Breaking Mechanism of Multiwalled Carbon Nanotubes Under Tensile Load". Science 287 (5453): 637–640. Bibcode 2000Sci...287..637Y. doi:10.1126/science.287.5453.637. PMID 10649994.
- ^ Boyle, Alan. "Space elevator contest proposed". MSNBC. http://msnbc.msn.com/id/5792719/. Retrieved 2006-03-05.
- ^ "The Space Elevator – Elevator:2010". http://www.elevator2010.org/. Retrieved 2006-03-05.
- ^ "Space Elevator Ribbon Climbing Robot Competition Rules". Archived from the original on December 1, 2005. http://web.archive.org/web/20051201005853/http://robolympics.net/rules/climbing.shtml. Retrieved 2006-03-05.
- ^ "NASA Announces First Centennial Challenges' Prizes". 2005. http://www.nasa.gov/home/hqnews/2005/mar/HQ_m05083_Centennial_prizes.html. Retrieved 2006-03-05.
- ^ Britt, Robert Roy. "NASA Details Cash Prizes for Space Privatization". Space.com. http://www.space.com/news/050323_centennial_challenge.html. Retrieved 2006-03-05.
- ^ "What's the European Space Elevator Challenge?". European Space Elevator Challenge. http://eusec.warr.de/?eusec. Retrieved 2011-04-21.
- ^ "Space Elevator Group to Manufacture Nanotubes". Universe Today. 2005. http://www.universetoday.com/am/publish/liftport_manufacture_nanotubes.html?2742005. Retrieved 2006-03-05.
- ^ Groshong, Kimm (2006-02-15). "Space-elevator tether climbs a mile high". NewScientist.com (New Scientist). http://www.newscientistspace.com/article/dn8725.html. Retrieved 2006-03-05.
- ^ Elevator:2010 – The Space Elevator Challenge. spaceward.org
- ^ Spaceward Games 2007. The Spaceward Foundation
- ^ a b c Lewis, Leo (2008-09-22). "Japan hopes to turn sci-fi into reality with elevator to the stars". The Times (London). http://www.timesonline.co.uk/tol/news/uk/science/article4799369.ece. Retrieved 2010-05-23. Lewis, Leo; News International Group; accessed 2008-09-22.
- ^ "Leaving the Planet by Space Elevator". http://www.leavingtheplanet.com/. Edwards, Bradley C. and Westling, Eric A. and Ragan, Philip; Leasown Pty Ltd.; accessed 2008-09-26.
- ^ http://www.nytimes.com/2011/11/14/technology/at-google-x-a-top-secret-lab-dreaming-up-the-future.html
- ^ a b c "The Space Elevator NIAC Phase II Final Report" (PDF). NASA. http://www.spaceelevator.com/docs/521Edwards.pdf. Retrieved 2007-06-12.
- ^ Al Globus; David Bailey, Jie Han, Richard Jaffe, Creon Levit, Ralph Merkle, and Deepak Srivastava. "NAS-97-029: NASA Applications of Molecular Nanotechnology" (PDF). NASA. http://www.nas.nasa.gov/News/Techreports/1997/PDF/nas-97-029.pdf. Retrieved 2008-09-27.
- ^ "The Space Elevator: Phase I Study" by Bradley Carl Edwards
- ^ This 4,960 km "escape length" (calculated by Arthur C. Clarke in 1979) is much shorter than the actual distance spanned because centrifugal forces increase (and gravity decreases) dramatically with height: Clarke, A.C. (1979). "The space elevator: 'thought experiment', or key to the universe?". http://www.islandone.org/LEOBiblio/CLARK2.HTM.
- ^ World's Longest Laser – 270 Km Long – Created ScienceDaily, December 16, 2009
- ^ Wang, X.; Li, Q.; Xie, J.; Jin, Z.; Wang, J.; Li, Y.; Jiang, K.; Fan, S. (2009). "Fabrication of Ultralong and Electrically Uniform Single-Walled Carbon Nanotubes on Clean Substrates". Nano Letters 9 (9): 3137–3141. Bibcode 2009NanoL...9.3137W. doi:10.1021/nl901260b. PMID 19650638.
- ^ "Why the Space Elevator's Center of Mass is not at GEO" by Blaise Gassend. Gassend.com. Retrieved on 2011-09-30.
- ^ Cohen, Stephen S.; Misra, Arun K. (2009). "The effect of climber transit on the space elevator dynamics". Acta Astronautica 64 (5–6): 538–553. doi:10.1016/j.actaastro.2008.10.003.
- ^ Edwards. "NIAC Space Elevator Report – Chapter 4: Power Beaming". NASA. Archived from the original on 2007-10-13. http://web.archive.org/web/20071013160456/http://isr.us/Downloads/niac_pdf/chapter4.html. "Alternatives that have been suggested include running power up the cable, solar or nuclear power onboard and using the cable's movement in the environment's electromagnetic field. None of these methods are feasible on further examination due to efficiency or mass considerations. Another alternative is to run two cables, for carrying power (a high-voltage positive and a negative line) and each capable of holding the counterweight (system redundancy)."
- ^ Edwards BC, Westling EA. The Space Elevator: A Revolutionary Earth-to-Space Transportation System. San Francisco, USA: Spageo Inc.; 2002. ISBN 0-9726045-0-2.
- ^ Boucher, Marc. (2009-09-01) Canadian Mini Space Elevator Paper Available – The Space Elevator Reference. Spaceelevator.com. Retrieved on 2011-09-30.
- ^ Quine, B.M.; Seth, R.K.; Zhu, Z.H. (2009). "A free-standing space elevator structure: A practical alternative to the space tether". Acta Astronautica 65 (3–4): 365. Bibcode 2009AcAau..65..365Q. doi:10.1016/j.actaastro.2009.02.018. http://pi.library.yorku.ca/dspace/bitstream/handle/10315/2587/AA_3369_Quine_Space_Elevator_Final_2009.pdf.
- ^ "York U-designed space elevator would reach 20 km above Earth". York University. June 15, 2009. http://www.yorku.ca/mediar/archive/Release.php?Release=1695. Retrieved 2009-11-13.
- ^ Space Shaft: Or, the story that would have been a bit finer, if only one had known…, "Knight Science Journalism Tracker (MIT)", July 1, 2009
- ^ Kilian A. Engel. "IAC-04-IAA.3.8.3.04 Lunar transportation scenarios utilising the space elevator". www.spaceelevator.com. http://www.spaceelevator.com/docs/iac-2004/iac-04-iaa.3.8.3.04.engel.pdf.
- ^ P. K. Aravind (February 2007). "The physics of the space elevator". American Journal of Physics (American Association of Physics Teachers) 45 (2): 125. Bibcode 2007AmJPh..75..125A. doi:10.1119/1.2404957.
- ^ "Hans Moravec: SPACE ELEVATORS (1980)". http://www.frc.ri.cmu.edu/~hpm/project.archive/1976.skyhook/1982.articles/elevate.800322.
- ^ SPACE ELEVATORS Robert L. Forward Hans P. Moravec March 22, 1980 Copyright 1980 Dr. Robert L. Forward and Hans P. Moravec "Interestingly enough, they are already more than strong enough for constructing skyhooks on the moon and Mars."
- ^ a b Pearson, Jerome; Eugene Levin, John Oldson and Harry Wykes (2005). "Lunar Space Elevators for Cislunar Space Development Phase I Final Technical Report" (PDF). http://www.niac.usra.edu/files/studies/final_report/1032Pearson.pdf.
- ^ "Asteroid Retrieval by Rotary Rocket" (PDF). NASA. http://www.star-tech-inc.com/papers/asteroids/asteroids.pdf. Retrieved 2007-06-12.
- ^ "Tapered Sling". Island One Society. http://www.islandone.org/LEOBiblio/SPBI1SL.HTM. Retrieved 2007-06-12.
- ^ Graham FG "Preliminary Design of a Cable Spacecraft Connecting Mutually Tidally Locked Planetary Bodies" AIAA 2009-4906, 45th Joint Propulsion Conference.
- ^ "Delayed countdown". Fultron Corporation. The Information Company Pvt Ltd. 18 October 2002. http://www.domain-b.com/companies/companies_f/futron_corporation/20021018_countdown.html. Retrieved June 3, 2009.
- ^ The Spaceward Foundation. "The Space Elevator FAQ". Mountain View, CA. http://www.spaceward.org/elevator-faq. Retrieved June 3, 2009.
- ^ Pournelle, Jerry (23 April 2003). "Friday's VIEW post from the 2004 Space Access Conference". http://www.jerrypournelle.com/archives2/archives2view/view306.html#Friday. Retrieved Jan 1, 2010.
- ^ Ramadge, Andrew; Schneider, Kate (17 November 2008). "Race on to build world's first space elevator". http://www.news.com.au/technology/story/0,25642,24662622-5014239,00.html. Retrieved June 3, 2009. [dead link]
- Edwards BC, Ragan P. "Leaving The Planet By Space Elevator" Seattle, USA: Lulu; 2006. ISBN 978-1-4303-0006-9 See Leaving The Planet
- Edwards BC, Westling EA. The Space Elevator: A Revolutionary Earth-to-Space Transportation System. San Francisco, USA: Spageo Inc.; 2002. ISBN 0-9726045-0-2.
- Space Elevators – An Advanced Earth-Space Infrastructure for the New Millennium [PDF]. A conference publication based on findings from the Advanced Space Infrastructure Workshop on Geostationary Orbiting Tether "Space Elevator" Concepts, held in 1999 at the NASA Marshall Space Flight Center, Huntsville, Alabama. Compiled by D.V. Smitherman, Jr., published August 2000.
- "The Political Economy of Very Large Space Projects" HTML PDF, John Hickman, Ph.D. Journal of Evolution and Technology Vol. 4 – November 1999.
- The Space Elevator NIAC report by Dr. Bradley C. Edwards
- A Hoist to the Heavens By Bradley Carl Edwards
- Ziemelis K. (2001) "Going up". In New Scientist 2289: 24–27. Republished in SpaceRef. Title page: "The great space elevator: the dream machine that will turn us all into astronauts."
- The Space Elevator Comes Closer to Reality. An overview by Leonard David of space.com, published 27 March 2002.
- Krishnaswamy, Sridhar. Stress Analysis — The Orbital Tower (PDF)
- LiftPort's Roadmap for Elevator To Space SE Roadmap (PDF)
- Space Elevators Face Wobble Problem: New Scientist
- Peter Swan & Cathy Swan, "Space Elevator Systems Architecture." Lulu.com 2007. isbn 978-1-4303-1405-9 See ref. 555344 at www.lulu.com
- The Space Elevator Reference
- Space Elevator Engineering-Development wiki
- Audacious & Outrageous: Space Elevators
- Ing-Math.Net (Germany) – Ing-Math.Net (German Max-Born Space Elevator Team 2006) (German)
- Project of the Scientific Workgroup for Rocketry and Spaceflight(WARR) (German)
- The Economist: Waiting For The Space Elevator (June 8, 2006 – subscription required)
- CBC Radio Quirks and Quarks November 3, 2001 Riding the Space Elevator
- Times of London Online: Going up ... and the next floor is outer space
- The Space Elevator: 'Thought Experiment', or Key to the Universe?. By Sir Arthur C. Clarke. Address to the XXXth International Astronautical Congress, Munich, 20 September 1979.
Space elevator Main articles Concepts Technologies CompetitionsSpace elevator games · Elevator:2010 · European Space Elevator Challenge · Japan Space Elevator & Technical Competition People Organizations See also: Skyhook · Non-rocket spacelaunch · Spaceflight · Megascale engineering Non-rocket spacelaunch Spaceflight Static structuresCompressiveSpace towerTensileSpace elevator · Hypersonic skyhook · SpaceShaftBolusRotovators · Hypersonic bolusOtherEndo-atmospheric tethers Dynamic structures Projectile launchersElectricalChemicalMechanicalSlingatron Reaction drives Buoyant lifting See also: Rocket sled launch · Megascale engineering
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Saturn consists almost entirely of helium and hydrogen. Gas giant planets are thought to have accreted out of the solar nebula through collisions as a core of ice with a small component of rock, up to about 10 Earth masses, at which point the gas of the solar nebula began to be attracted to the protoplanets. Later differentiation may consist mainly of separation of helium and hydrogen.
Knowing that the planet must consist almost entirely of helium and hydrogen based on its density and the abundance of those elements in the solar system, models for the planet's interior can be made based on laboratory physics. The behavior of those elements can be predicted as pressure in the planet increases with depth. In the planet's interior, helium and hydrogen gas gradually become liquid with increasing pressure and depth. At a pressure of about 2.5 million atmospheres (250 GPa), hydrogen changes abruptly into a metallic state. In its metallic state the hydrogen atom's electrons flow freely among the nuclei, creating an electrically conductive region. Beneath the metallic zone probably lies a planet's dense ice-silicate core, thought to make up about one-third of its total mass and reach to about one-quarter of the planet's radius. Saturn's interior is thought to reach a pressure of 45 million atmospheres (4,500 GPa) and a temperature of about 22,000°F (12,000°C). Compare this to the Earth, which reaches only 8,700°F (4,800°C) and 3.5 million atmospheres (360 GPa) in the inner core.
The density of Saturn is low, consisting as it does mainly of helium and hydrogen. The shallow parts of the planet's temperature profile can be measured through stellar occultation: As a star's light is eclipsed behind Saturn, its light is extinguished gradually by the increasing density of Saturn's atmosphere. The rate of extinction of the star's light yields information on the density of the atmosphere, which in turn can be related to temperature (the higher the temperature, the less dense the atmosphere). Spectra obtained from a known constituent in the atmosphere, such as methane, can also give temperature information.
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June 8, 2018 9:30 am
TESS – new satellite discovers new worlds.
The Transiting Exoplanet Survey Satellite (TESS) was launched on 18 April on a mission to survey stars and discover thousands of new worlds beyond our solar system. TESS now takes over from Kepler – the previous satellite. This space telescope, equipped with four cameras, will scan almost the entire sky for at least two years, focusing its objectives on the nearest and brightest stars. Thus 85% of the sky will be photographed and analysed. Its goal is to find and identify exoplanets ranging from Earth-sized to gas giants, orbiting a wide range of stellar types and orbital distances. Hundreds of thousands of stars will be scanned, with the hope that many exoplanets will be revealed in our cosmic backyard. The primary goal of the mission is to detect small planets in the solar region, so that detailed accounts of the planets and their atmospheres can be performed.
“The sky will become more beautiful, more impressive. We are thrilled TESS is on its way to help us discover worlds we have yet to imagine, worlds that could possibly be habitable, or harbour life,” notes NASA’s highest scientific administrator, Thomas Zurbuchen. The discoveries of TESS and other missions, he said, will bring us closer to answering the questions we have been asking ourselves for thousands of years: does life exist elsewhere in the Universe? If so, is this life microbial, or more advanced? Once TESS has identified new planets, terrestrial and space telescopes will be able to study them more accurately. Before the Kepler telescope was launched, no one knew if exoplanets were rare or numerous in the galaxy. Thanks to Kepler and the scientific community, we now know that they could outnumber the stars. Now imagine the possibilities that TESS opens.
On 18th of April, TESS sent back its first stunning test image – a swathe of the southern sky, captured by one of the four cameras, with more than 200 000 bright stars of our galaxy. TESS is expected to cover more than 400 times the amount of sky shown in this image when using all four of its cameras during science operations.
As regards the EU’s competence in space, it was established by the Lisbon Treaty (Article 189 TFEU). There are some systems which the European Union is using for the benefit of EU citizens. For example, Copernicus, the European system for observing our planet and its environment, keeping an eye on the atmosphere, climate change, emergencies and civil security. Another system is Galileo, Europe’s own navigation satellite system. It consists of 30 satellites, providing a highly accurate, guaranteed global positioning service under civilian control.The first European satellite-based augmentation system is EGNOS, it stands for European Geostationary Navigation Overlay Service, which is used to improve the performance of global navigation satellite systems (GNSSs), such as GPS and Galileo.
Check out the entry for satellite in our IATE database:
We hope you found this article useful. Visit our website next time to discover the new IATE term of the week.
1) Claire Saravia (2018) NASA’s New Planet Hunter Snaps Initial Test Image, Swings by Moon Toward Final Orbit
Available at : https://www.nasa.gov/feature/goddard/2018/nasa-s-new-planet-hunter-snaps-initial-test-image-swings-by-moon-toward-final-orbit
2) ‘Out of this world: three things to know about Europe’s space policy’
Available at : http://www.europarl.europa.eu/news/en/headlines/security/20160606STO30624/out-of-this-world-three-things-to-know-about-europe-s-space-policy
3) ‘Andrew Griffin, TESS is expected to find thousand of alien world’
Available at: https://www.independent.co.uk/life-style/gadgets-and-tech/news/nasa-stars-picture-planet-hunting-best-images-tess-exoplanet-latest-a8361436.html
4) ‘Galileo is the European global satellite-based navigation system’
Available at: https://www.gsa.europa.eu/european-gnss/galileo/galileo-european-global-satellite-based-navigation-system
5) ‘The Search for Life and Exoplanets’
Available at : https://www.nasa.gov/tess-transiting-exoplanet-survey-satellite/
6) ‘What is Egnos?’
Available at : https://www.gsa.europa.eu/egnos/what-egnos
Written by Krystina Garibyan – Communication Study Visitor at the Terminology Coordination Unit of the European Parliament (Luxembourg) and a student of the Master Program in Learning and Communication in Multilingual and Multicultural Contexts at the University of Luxembourg. She holds a BA in Information and Communication in University of Nice. She speaks English, Russian, French and Spanish.
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Once again, a search for signs of dark matter outside its gravitational effect has turned up zilch – but this time it’s a little more controversial. Astronomers peering into empty space have not found an X-ray glow hypothesised to be the product of one particular dark matter candidate: the sterile neutrino.
It is, the researchers say, a result that throws a bit of a dampener on this candidate as a leading contender for dark matter – but doesn’t extinguish it entirely.
Dark matter is a huge old question mark. Although we can’t detect it directly, we know it’s out there because it’s having a really big gravitational effect on the stuff we can detect, also known as normal matter.
For instance, stuff on the outer edges of galaxies moves faster than it should if it were under the gravitational influence of normal matter alone. And gravitational lensing – the way gravity bends the path of light – is stronger than we would expect, too. From these effects, astronomers have calculated that as much as 85 percent of the matter in the Universe is dark matter.
Because we can’t detect it, though, we don’t know what it is. And there are a number of hypothetical candidates, with astronomers trying to come up with ways to detect these.
The sterile neutrino is a hypothetical particle. Normal neutrinos, the most abundant particles in the Universe, are very hard to detect at the best of times – they are similar to electrons, but with no charge and very little mass, so they barely interact with normal matter. A sterile neutrino, physicists have hypothesised, wouldn’t interact with normal matter at all, except maybe gravitationally.
But these hypothetical neutrinos are unstable, too. They should decay into normal neutrinos and electromagnetic radiation. And, if they are so decaying, then that radiation should be detectable. Very faint, but detectable.
That’s what a 2014 study claimed to have done – detected the faint X-rays from sterile neutrino decay from distant galaxies, an emission called the 3.5 KeV line. But then follow-up studies – one in 2016 on a dwarf galaxy 260,000 light-years away, and another in 2017 on a galaxy cluster 240 million light-years away – found no such thing.
So, a team of researchers decided to look a bit closer to home. We know the Milky Way has a substantial dark matter halo, so if sterile neutrinos are decaying in it, they should be detectable around the galaxy.
The team conducted a meta-analysis of 20 years of raw archival X-ray data of empty space around the Milky Way, where other glowing objects wouldn’t create interference, taken by the XMM-Newton space telescope, looking for signs of that 3.5 KeV emission. They didn’t find any.
“This 2014 paper and follow-up works confirmed the signal generated a significant amount of interest in the astrophysics and particle physics communities because of the possibility of knowing, for the first time, precisely what dark matter is at a microscopic level,” said physicist Ben Safdi of the University of Michigan.
“Our finding does not mean that the dark matter is not a sterile neutrino, but it means that – contrary to what was claimed in 2014 – there is no experimental evidence to-date that points towards its existence.”
The result suggests that something else was causing the 3.5 KeV glow seen in that 2014 study, the researchers said. But not everyone is convinced. Physicist Alexey Boyarsky of Leiden University in the Netherlands posted a similar survey to preprint server arXiv, looking at the blank sky of the Milky Way. His team believes they did find the 3.5 KeV line.
“I think this paper is wrong,” he said of the new research to Science Magazine. The different results could be the product of the two different analysis techniques; both teams believe their method is superior, although Boyarsky’s paper is yet to be peer-reviewed.
So it seems the question may still be somewhat open, and only more research can help to resolve it.
Meanwhile, there’s another direction that can be taken, too. Safdi says that his team’s conclusions open up a new avenue for further search on the matter.
“While this work does, unfortunately, throw cold water on what looked like what might have been the first evidence for the microscopic nature of dark matter, it does open up a whole new approach to looking for dark matter which could lead to a discovery in the near future,” he said.
The research has been published in Science. | 0.849193 | 4.113279 |
Black holes are the Universeâs ultimate garbage disposals: Stuff falls in, and never gets back out. It canât. To get out, youâd have to travel faster than the speed of light, which (as far as we know) is impossible.
Black holes grow by consuming matter, and in the centers of galaxies they can grow to huge size. In the gorgeous barred spiral galaxy NGC 1365 (shown below), thereâs one lurking in the core that has about two million times as much mass as our Sun. Not only that, it is actively gobbling down matter, and that allows us to measure some interesting properties of this cosmic monster, including its spin. Astronomers observed NGC 1365âs black hole using the NuSTAR and XMM-Newton observatories, and were surprised to find out itâs spinning so fast that the outer edge is moving at very nearly the speed of light!
This takes some explaining. Hang on tightly, and for your own safety please keep your arms inside the blog post at all times.
Black holes are confusing, but the bottom line is that they are such highly-concentrated massive objects that their escape velocity is faster than lightâI wrote a somewhat more lengthier explanation on the old blog here and here if you want more details. Once something falls in, it cannot get out, but some of the properties of that material remain: specifically mass, spin, and charge. That last bit is literally electrical charge, like how an electron has a negative charge. Physically itâs very interesting, but in practical terms it hardly comes up, so we can ignore it here.
Mass is the critical one, because the more mass a black hole has, the bigger it gets and the stronger its gravity is as well. But spin is important too. Look at, for example, a black hole forming via the collapse of a starâs core when the outer layers explode in a supernova. The core is spinning since the star rotates. As the core collapses, that spin rate increases, in much the same way a skater can increase his or her spin by bringing their arms in close to their body. This is called conservation of angular momentum; objects spinning tend to stay spinning due to momentum, just like any object in motion tends to stay in motion due to momentum. The total angular momentum depends on the objectâs size and rate of spin. Increase one and the other must decrease; if you make something smaller itâll spin faster.
So by the time the core of our doomed star collapses all the way down to a back hole, the spin can be ferociously large.
But thereâs more. If there is material around the black hole falling in it can change the spin as well. If material fell straight into the black hole, the spin wouldnât change much (if anything it would decrease, because the added mass makes the black hole bigger, so, like the skater throwing out his/her arms, the spin slows). But if that material comes in at a slight angle, it can actually add to the spin of the black hole, increasing its angular momentum. That gives a kick to the spin rate, bumping it up.
And that brings us back to NGC 1365, located about 60 million light years from Earth. Astronomers used NuSTAR to look at X-rays pouring out of material falling into the black hole there. As that material falls in it heats up to millions of degrees, blasting out X-rays that are easily bright enough to see from Earth with the right equipment. Careful observations allowed astronomers to see these X-rays coming from matter just before it reached The Point Of No Return, at a position called the Innermost Stable Circular Orbit, or ISCO. If it gets any closer, blooop! It falls in, and itâs gone.
As the material swirls around the black hole, it emits X-rays at a very specific energyâthink of it as a color. But as it orbits that color gets smeared out due to the Doppler effect. The amount of smearing indicates how fast the material is moving, and that in turn can tell astronomers how fast the black hole is spinning. This can be complicated by the presence of dense clouds of material farther out from the black hole that absorb X-rays and mess up our observations. The new data from NuSTAR allowed astronomers to show that the smearing seen is definitely due to rotation and not obscuration, unambiguously revealing the black hole's tremendous spin: just a hair below the speed of light!
Most black holes spin far slower than that, so something ramped this holeâs spin way up. One possibility, as I mentioned above, is material falling in over time. Another is that it ate one or more other black holes, which is creepy but possible. Galaxies collide, and when they do their central black holes can merge, growing larger. If the geometry is just right, this can create a single black hole with more spin. Do this a few times, and you can spin one up to fantastic speeds.
Iâll note that NGC 1365 is a massive galaxy, easily twice as large as the Milky Way (and weâre one of the biggest galaxies in the Universe). Thatâs exactly what youâd expect from a galaxy thatâs spent a lifetime eating other ones. Cosmic cannibals grow fat when the huntingâs good.
This is a pretty amazing finding by the NuSTAR astronomers. It shows that extremely detailed X-rays observations are possible but are very difficult and painstaking to do. It also demonstrates that we can take a pretty close look at black holes and tease out details that were previously not possible to see. This in turn means we can test a lot of the hypotheses we have about these monsters and improve our understanding of them.
By themselves, black holes are invisible, dark, and nearly impossible to observe. But theyâre sloppy eaters, and this betrays many of their secrets. Even from 600 million trillion kilometers away. | 0.873052 | 3.92145 |
First there was the recent story about evidence for a possible subsurface ocean on Pluto, of all places. Now there is a new report regarding evidence for complex molecules on its surface, from scientists at Southwest Research Institute and Nebraska Wesleyan University. Little enigmatic Pluto is starting to get even more interesting…
The findings come from the Hubble Space Telescope, using the new and highly sensitive Cosmic Origins Spectrograph which indicate that there is a strong ultraviolet-wavelength absorber on the surface. This absorbing material is thought to likely be complex hydrocarbons and/or nitriles. The results have been published in the Astronomical Journal.
Pluto’s surface is known to be coated with ices composed of methane, carbon monoxide and nitrogen (it is extremely cold there!). The putative molecules can be produced by sunlight or cosmic rays interacting with those ices.
“This is an exciting finding because complex Plutonian hydrocarbons and other molecules that could be responsible for the ultraviolet spectral features we found with Hubble may, among other things, be responsible for giving Pluto its ruddy color,” said project leader Dr. Alan Stern.
The team also found evidence for surface changes in the ultraviolet spectrum, comparing current observations to those from the 1990s. The cause may be an increase in the pressure of Pluto’s tenuous atmosphere or different terrain which is being viewed at different times.
In a unique first for Universe Today, Dr. Alan Stern was the first researcher to be asked questions from readers via the comments section of this recent interview article by Ray Sanders. His answers to the top five questions (as ranked by “likes” on the discussion posts) will be posted soon in a subsequent article. Stern is also the principal investigator for the New Horizons spacecraft currently en route to Pluto.
A copy of the paper by Stern et al. is available here.
With all of the new discoveries already being made about Pluto, it should be very interesting when New Horizons gets there in 2015, providing us with the first close-up look of this fascinating little world. | 0.883471 | 3.487703 |
For the first time, astronomers created the detailed image of a gigantic star, which is 350 times larger than the Sun.
Its image resembles what our Sun will become at the end of its life in five billion years.
The object named π1Gruis, is located in the constellation Grus (Latin for the crane, a type of bird), which can be observed in the southern hemisphere. The image of the star reveals almost circular, dust-free atmosphere with complex areas of moving material, known as convection cells or granules, according to a recent study.
“This is the first time that we have such a giant star that is unambiguously imaged with that level of details,” said Dr. Fabien Baron, assistant professor in the Department of Physics and Astronomy at Georgia State University.
“The reason is there’s a limit to the details we can see based on the size of the telescope used for the observations. For this paper, we used an interferometer. The light from several telescopes is combined to overcome the limit of each telescope, thus achieving a resolution equivalent to that of a much larger telescope.”
This study provided astronomers with an excellent opportunity to look at the star’s convection cells (or granules) and compare it with that of our Sun.
NOTE: Convection, the transfer of heat due to the bulk movement of molecules within gases and liquids, plays a major role in astrophysical processes, such as energy transport, pulsation and winds.
The Sun has about two million convective cells that are typically 2,000 kilometers across.
The study showed that the the surface of the giant star π1Gruis had a complex convective pattern and the typical granule measured 1.2 x 10^11 meters horizontally or 27 percent of the diameter of the star. It means about a quarter of π1Gruis’s diameter, which is approximately 120 million kilometers across.
The star π1Gruis was observed with the ESO’s PIONIER instrument, which has four combined telescopes, in Chile.
“These images are important because the size and number of granules on the surface actually fit very well with models that predict what we should be seeing,” Baron said.”That tells us that our models of stars are not far from reality. We’re probably on the right track to understand these kinds of stars.”
The detailed images also showed different colors on the star’s surface, which correspond to varying temperatures. A star doesn’t have the same surface temperature throughout, and its surface provides our only clues to understand its internals.
As temperatures rise and fall, the hotter, more fluid areas become brighter colors (such as white) and the cooler, more dense areas become darker colors (such as red). | 0.81545 | 3.955933 |
If you’re a long-time astrobites reader with interests that extend to the fascinating and vibrant field of particle physics, you’ll love the work being published at our sister site particlebites. Like astrobites, particlebites authors are graduate students that cover the latest research in their field, particle physics, by posting concise and engaging summaries of newly published research and preprints. Below is an excerpt from a post by particlebites guest author Chris Karwin.
The center of the galaxy is brighter than astrophysicists expected. Could this be the result of the self-annihilation of dark matter? Chris Karwin, a graduate student from the University of California, Irvine presents the Fermi collaboration’s analysis.
Like other telescopes, the Fermi Gamma-Ray Space Telescope is a satellite that scans the sky collecting light. Unlike many telescopes, it searches for very high energy light: gamma-rays. The satellite’s main component is the Large Area Telescope (LAT). When this detector is hit with a high-energy gamma-ray, it measures the the energy and the direction in the sky from where it originated. The data provided by the LAT is an all-sky photon counts map:
In 2009, researchers noticed that there appeared to be an excess of gamma-rays coming from the galactic center. This excess is found by making a model of the known astrophysical gamma-ray sources and then comparing it to the data.
What makes the excess so interesting is that its features seem consistent with predictions from models of dark matter annihilation. | 0.81933 | 3.287513 |
A historic collaboration of scientists around the world, with contributions by a McGill physicist, has lifted the veil on a cosmic mystery by proving the existence of black holes.
The Event Horizon Telescope (EHT) — a planet-scale array of eight ground-based radio telescopes forged through international collaboration — was designed to capture images of a black hole. Today, in coordinated press conferences across the globe, EHT researchers reveal that they have succeeded, unveiling the first direct visual evidence of a supermassive black hole and its shadow.
This breakthrough was announced today in a series of six papers published in a special issue of The Astrophysical Journal Letters. The image reveals the black hole at the centre of Messier 87, a massive galaxy in the nearby Virgo galaxy cluster. This black hole resides 55 million light-years from Earth and has a mass 6.5-billion times that of the Sun.
Professor Daryl Haggard of the Department of Physics and the McGill Space Institute in Montreal contributed to two of the publications released today, as a member of the EHT’s Multi-wavelength Science Working Group. “The warping of spacetime around the massive black hole in M87 is so extreme that light captured by the EHT is showing us the space in front of and behind the black hole at the same time,” Haggard said. “Theorists predicted what this would look like – a concept simulated, for example, in the movie Interstellar – but we’re seeing it in real life for the very first time.”
The EHT links telescopes around the globe to form an Earth-sized virtual telescope with unprecedented sensitivity and resolution. The EHT is the result of years of international collaboration, and offers scientists a new way to study the most extreme objects in the Universe predicted by Einstein’s general relativity during the centennial year of the historic experiment that first confirmed the theory.
“We have taken the first picture of a black hole,” said EHT project director Sheperd S. Doeleman of the Center for Astrophysics | Harvard & Smithsonian. “This is an extraordinary scientific feat accomplished by a team of more than 200 researchers.”
Black holes are extraordinary cosmic objects with enormous masses but extremely compact sizes. The presence of these objects affects their environment in extreme ways, warping spacetime and super-heating any surrounding material.
“If immersed in a bright region, like a disc of glowing gas, we expect a black hole to create a dark region similar to a shadow — something predicted by Einstein’s general relativity that we’ve never seen before,” explained chair of the EHT Science Council Heino Falcke of Radboud University, the Netherlands. “This shadow, caused by the gravitational bending and capture of light by the event horizon, reveals a lot about the nature of these fascinating objects and allowed us to measure the enormous mass of M87’s black hole.”
Multiple calibration and imaging methods have revealed a ring-like structure with a dark central region — the black hole’s shadow — that persisted over multiple independent EHT observations.
“Once we were sure we had imaged the shadow, we could compare our observations to extensive computer models that include the physics of warped space, superheated matter and strong magnetic fields. Many of the features of the observed image match our theoretical understanding surprisingly well,” said Paul T.P. Ho, EHT Board member and Director of the East Asian Observatory. “This makes us confident about the interpretation of our observations, including our estimation of the black hole’s mass.”
Global network of telescopes
Creating the EHT was a formidable challenge which required upgrading and connecting a worldwide network of eight pre-existing telescopes deployed at a variety of challenging high-altitude sites. These locations included volcanoes in Hawai`i and Mexico, mountains in Arizona and the Spanish Sierra Nevada, the Chilean Atacama Desert, and Antarctica.
The EHT observations use a technique called very-long-baseline interferometry (VLBI) which synchronises telescope facilities around the world and exploits the rotation of our planet to form one huge, Earth-size telescope observing at a wavelength of 1.3mm. VLBI allows the EHT to achieve an angular resolution of 20 micro-arcseconds — enough to read a newspaper in New York from a sidewalk café in Paris.
The telescopes contributing to this result were ALMA, APEX, the IRAM 30-meter telescope, the James Clerk Maxwell Telescope, the Large Millimeter Telescope Alfonso Serrano, the Submillimeter Array, the Submillimeter Telescope, and the South Pole Telescope. Petabytes of raw data from the telescopes were combined by highly specialised supercomputers hosted by the Max Planck Institute for Radio Astronomy and MIT Haystack Observatory.
Achieving “the impossible”
The construction of the EHT and the observations announced today represent the culmination of decades of observational, technical and theoretical work. This example of global teamwork required close collaboration by researchers from around the world. Thirteen partner institutions worked together to create the EHT, using both pre-existing infrastructure and support from a variety of agencies. Key funding was provided by the US National Science Foundation (NSF), the EU’s European Research Council (ERC), and funding agencies in East Asia.
“We have achieved something presumed to be impossible just a generation ago,” concluded Doeleman.”Breakthroughs in technology, connections between the world’s best radio observatories, and innovative algorithms all came together to open an entirely new window on black holes and the event horizon.” | 0.877088 | 3.913736 |
Note: This is a 360° Video — press and hold to explore it!
Home Run Pictures, working with NASA scientists, visualized engineering concepts for a space station that would dive into the upper atmosphere of the planet Uranus.
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…
Uranus : the planet seventh in order from the sun — Webster
Uranus is the seventh planet from the Sun. It has the third-largest planetary radius and fourth-largest planetary mass in the Solar System. Uranus is similar in composition to Neptune, and both have different bulk chemical composition from that of the larger gas giants Jupiter and Saturn. For this reason, scientists often classify Uranus and Neptune as “ice giants” to distinguish them from the gas giants. Uranus’s atmosphere is similar to Jupiter’s and Saturn’s in its primary composition of hydrogen and helium, but it contains more “ices” such as water, ammonia, and methane, along with traces of other hydrocarbons. It is the coldest planetary atmosphere in the Solar System, with a minimum temperature of 49 K (−224 °C; −371 °F), and has a complex, layered cloud structure with water thought to make up the lowest clouds and methane the uppermost layer of clouds. The interior of Uranus is mainly composed of ices and rock.
Uranus is the only planet whose name is derived from a figure from Greek mythology, from the Latinised version of the Greek god of the sky Ouranos. Like the other giant planets, Uranus has a ring system, a magnetosphere, and numerous moons. The Uranian system has a unique configuration among those of the planets because its axis of rotation is tilted sideways, nearly into the plane of its solar orbit. Its north and south poles, therefore, lie where most other planets have their equators. In 1986, images from Voyager 2 showed Uranus as an almost featureless planet in visible light, without the cloud bands or storms associated with the other giant planets. Observations from Earth have shown seasonal change and increased weather activity as Uranus approached its equinox in 2007. Wind speeds can reach 250 metres per second (900 km/h; 560 mph). — Wikipedia
Cataclysmic collision shaped Uranus’ evolution (Durham University)
Consequences of Giant Impacts on Early Uranus for Rotation, Internal Structure, Debris, and Atmospheric Erosion (J. A. Kegerreis Et al., The Astrophysical Journal)
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.
Researchers observe protons 'playing hopscotch'...
on May 25, 2020 at 1:53 pm
An international team of researchers from University College Dublin (UCD) and University of Saskatchewan, Canada, have observed 'proton-hopping' movement in a high-pressure form of ice (Ice VII lattices).
Astronomers find formula for subsurface oceans in...
on April 23, 2020 at 2:47 pm
So far, the search for extraterrestrial life has focused on planets at a distance from their star where liquid water is possible on the surface. But within our Solar System, most of the liquid water seems to be outside this zone. Moons around cold gas giants are heated beyond the melting point by tidal forces. The search area in other planetary systems therefore increases if we also consider moons. Researchers from SRON and RUG have now found a formula to calculate the presence and depth of […]
Methane forms under space conditions in laboratory
on April 14, 2020 at 1:36 pm
An international team of astronomers has shown in a laboratory at Leiden University (the Netherlands) that methane can form on icy dust particles in space. The possibility had existed for quite some time, but because the conditions in space were difficult to simulate, it was not possible to prove this under relevant space conditions. The researchers will publish their findings Monday evening in the journal, Nature Astronomy.
What makes Saturn's atmosphere so hot
on April 7, 2020 at 7:08 am
The upper layers in the atmospheres of gas giants—Saturn, Jupiter, Uranus and Neptune—are hot, just like Earth's. But unlike Earth, the Sun is too far from these outer planets to account for the high temperatures. Their heat source has been one of the great mysteries of planetary science.
Origins of Uranus' oddities explained by Japanese...
on April 6, 2020 at 11:18 am
The ice giant Uranus' unusual attributes have long puzzled scientists. All of the planets in the solar system revolve around the sun in the same direction and in the same plane, which astronomers believe is a vestige of how our solar system formed from a spinning disc of gas and dust. Most of the planets also rotate in the same direction, with their poles orientated perpendicular to the plane in which the planets revolve. However, uniquely among all the planets, Uranus is tilted at about 98 […] | 0.902772 | 3.537071 |
A planet-hunting NASA spacecraft has detected no sign of moon-size black holes yet in the Milky Way galaxy, limiting the chances that such objects could make up most of the "dark matter" that has mystified scientists for decades.
Dark matter is one of the greatest scientific mysteries known — an invisible substance thought to constitute up five-sixths of all matter in the universe. It remains so mysterious that scientists are still uncertain as to whether dark matter is made of microscopic particles or far larger objects.
The consensus right now is that dark matter consists of a new type of particle, one that interacts very weakly at best with all the known forces of the universe except gravity. As such, dark matter is invisible and mostly intangible, with its presence only detectable via the gravitational pull it exerts. [Images: Black Holes of the Universe]
However, despite research from thousands of scientists relying on the most powerful particle accelerators on Earth and laboratories buried deep underground, no one has yet detected or created any particles that might be dark matter. This led Kim Griest, an astrophysicist at the University of California, San Diego, and his colleagues to investigate black holes as potential dark matter candidates.
Past research has discovered supermassive black holes millions to billions of times the mass of the sun in the heart of galaxies, but these are only detectable because they are so large, conspicuously disrupting matter around them. In theory, much smaller black holes could have formed in the early universe. These so-called primordial black holes would be far more difficult to detect, and they could potentially exist in large enough numbers to make up all dark matter.
But the new study finds no evidence to support this theory. Using NASA's Kepler space telescope, which launched in March 2009 to hunt for Earth-like planets around other stars, Griest and his colleagues have detected no sign of primordial black holes.
Over four years, Kepler monitored the brightness of more than 150,000 stars in the Milky Way to detect regular dimming caused by planets crossing in front of them. If a primordial black hole passed in front of one of these stars, the star would become temporarily brighter instead. That's because black holes warp light around them with their gravitational fields, a phenomenon known as gravitational lensing.
"Dark matter searches are normally very hard, involving experiments that take millions of dollars and decades to build," Griest said. "What's so cool and fun about this work is that we could use this experiment that was already built for completely different purposes to look for dark matter."
Until now, researchers had eliminated the chances that black holes that are approximately the mass of the moon could make up dark matter. Kepler's data show no evidence of black holes between 5 and 80 percent of the moon's mass, suggesting these black holes could not constitute most dark matter.
However, even smaller primordial black holes, ones less than 0.0001 percent the mass of Earth's moon, could still make up the entirety of dark matter, Griest said. Future missions — such as the European Space Agency's Euclid spacecraft or NASA's proposed WFIRST satellite — could look for smaller black holes than those identified by the Kepler data.
"We've ruled out a range of primordial black holes as dark matter, but have not ruled them out completely," Griest told SPACE.com. "They're still a viable candidate for dark matter."
Griest and his colleagues detailed their findings online Oct. 31 in the journal Physical Review Letters. | 0.88526 | 4.024212 |
The atmosphere of the ‘hot Saturn’ WASP-96b is cloud-free according to an international team of astronomers, led by Dr. Nikolay Nikolov from the University of Exeter.
With Europe’s 8.2 m Very Large Telescope in Chile, the team investigated the atmosphere of WASP-96b when the planet transited in front of its host star. This enabled the team to calculate the reduction of starlight caused by the planet and its atmosphere, and thus establish the planet’s atmospheric composition.
Similar to the fact that fingerprints of an individual are unique, atoms and molecules have a unique spectral feature that can be used to detect their existence in celestial objects. The spectrum of WASP-96b displays the whole fingerprint of sodium, which can only be seen in an atmosphere free of clouds.
The results have been published in the esteemed research journal Nature on May 7, 2018.
WASP-96b is a standard 1300 K hot gas giant similar to Saturn in mass and greater than the size of Jupiter by 20%. The planet occasionally transits a sun-like star 980 light years away in the southern constellation Phoenix, midway between the southern jewels Achernar (α Eridani) and Fomalhaut (α Piscis Austrini).
It has long been projected that sodium is present in the atmospheres of hot gas-giant exoplanets, and in a cloud-free atmosphere, it would form spectra that are similar in shape to the outline of a camping tent.
We’ve been looking at more than twenty exoplanet transit spectra. WASP-96b is the only exoplanet that appears to be entirely cloud-free and shows such a clear sodium signature, making the planet a benchmark for characterization.
Until now, sodium was revealed either as a very narrow peak or found to be completely missing. This is because the characteristic ‘tent-shaped’ profile can only be produced deep in the atmosphere of the planet and for most planet clouds appear to get in the way.
Nikolay Nikolov - Lead Author, University of Exeter
Hazes and clouds are said to be present in some of the coldest and hottest solar system planets and exoplanets. The absence or presence of clouds and their ability to obstruct light plays a key role in the total energy budget of planetary atmospheres.
"It is difficult to predict which of these hot atmospheres will have thick clouds. By seeing the full range of possible atmospheres, from very cloudy to nearly cloud-free like WASP-96b, we'll gain a better understanding of what these clouds are made of", explains Professor Jonathan J. Fortney, study co-author, based at the Other Worlds Laboratory (OWL) at the University of California, Santa Cruz (UCSC).
The sodium signature observed in WASP-96b indicates an atmosphere free of clouds. The observation enabled the team to measure how copious sodium is in the atmosphere of the planet, finding levels akin to those found in Earth’s own Solar System.
WASP-96b will also provide us with a unique opportunity to determine the abundances of other molecules, such as water, carbon monoxide and carbon dioxide with future observations.
Ernst de Mooij - Co-Author, Dublin City University.
Sodium is the Universe’s seventh most common element. On Earth, sodium compounds such as salt give the white color of salt pans in deserts and seawater its salty taste. In animal life, sodium is known to control metabolism and heart activity. Sodium can also be found in technology, such as in sodium-vapor street lights, where it creates yellow-orange light.
The team is focused on studying the signature of other atmospheric species, such as water, carbon dioxide, and carbon monoxide with the James Webb Space Telescope and the Hubble Telescope as well as telescopes on the ground. | 0.918071 | 3.961938 |
Jupiter’s icy moon Europa, home to a probable buried ocean, just added another twist to its exotic cool. The Hubble Space Telescope has spotted possible plumes of water spraying from Europa’s south pole.
The jets resemble the giant icy geyser seen on Saturn’s moon Enceladus. Plumes on Europa could be even more exciting because they hint at the ability to tap a subsurface habitat that might even harbour extraterrestrial life.
“If this pans out, it’s potentially the biggest news in the outer Solar System since the discovery of the Enceladus plume,” says Robert Pappalardo, a planetary scientist at the Jet Propulsion Laboratory in Pasadena, California, who was not involved in the research.
The work, reported today in Science1, comes with plenty of caveats. Although previous theoretical work suggested that plumes could exist on Europa, earlier tantalizing hints of them have come to nothing. This time, Hubble spotted the potential plumes in just one observation. And if they do turn out to be real, the plumes might not even be connected to the moon’s deep subsurface ocean.
“It’s a first-time discovery, and we need to go back and look some more,” says team member Joachim Saur, a planetary scientist at the University of Cologne in Germany.
Saur and his colleagues have looked for Europan plumes before, to no avail2. In 2012, the group decided to take another shot. Using an ultraviolet camera on Hubble, they scrutinized Europa once in November and once in December of that year. The November study found nothing, but the 2.7-hour exposure in December spotted blobs of hydrogen and oxygen near Europa’s south pole.
Their size, shape and chemical make-up is best explained by two plumes of water vapour roughly 200 kilometres high, says team leader Lorenz Roth, a planetary scientist at the Southwest Research Institute in San Antonio, Texas. That is many times the height of potential Europa plumes calculated by some theorists3. It would mean that Europa’s jets reach higher than the volcanic eruptions on Jupiter’s moon Io, but not as high as the towering plume that spouts from Enceladus.
Roth’s team spotted the plumes when Europa was at its greatest distance from Jupiter. Changing stresses in the moon’s crust, caused by tidal forces between the moon and planet, may explain why the researchers didn’t see any plumes in the November observation when Europa and Jupiter were close. “Maybe Europa is just burping once in a while,” Pappalardo says.
It is possible that the plumes may not tap into the deep subsurface, says Saur. The frictional heat of ice rubbing against itself might melt parts of the icy crust and feed the plumes.
Either way, the discovery could be a shot in the arm for upcoming missions. In 2022, the European Space Agency is planning to launch a probe that would explore Europa as well as Jupiter and its other moons. And Pappalardo leads a mission concept team at NASA that is outlining a possible US spacecraft to Europa.
Dear User/Visitor! Please, answer on our questions: tick off one of the positions – your answer will make us able to improve our site and make it more interesting and useful! | 0.881863 | 3.86301 |
Neptune has a new moon, and its existence is an enigma. The object, known for now as S/2004 N1, is the first Neptunian moon to be found in a decade. Its diminutive size raises questions as to how it survived the chaos thought to have created the giant planet’s other moons.
The faint moon was discovered in archived images from the Hubble Space Telescope. Mark Showalter of the SETI Institute in Mountain View, California, was poring over pictures of Neptune taken in 2009 to study segments of its rings.
The rings around our outermost planet are too faint to see without taking very long-exposure pictures. However, the rings orbit so fast that taking one long shot would smear them across the frame. Showalter and colleagues gathered multiple shorter-exposure images and developed a technique to digitally rewind the orbits to the same point in time. Then they could stack several images on top of each other to reveal details of the rings.
“I got nice pictures of the arcs, which was my main purpose, but I also got this little extra dot that I was not expecting to see,” says Showalter.
Stacking eight to 10 images together allowed the moon to show up plain as day, he says. When he went back and repeated the process using Hubble pictures taken in 2004, the moon was still there and moving as expected.
Daughters of Triton
The tiny addition to Neptune’s family is an added shock because it seems too small to have survived the formation of the other moons, according to accepted theories.
Neptune’s biggest moon, Triton, is 2705 kilometres wide and orbits backwards – travelling in the opposite direction to the planet’s spin. Its large size and wonky orbit led astronomers to believe that Triton was captured by Neptune’s gravity about 4 billion years ago and that it destroyed whatever moons the gas giant originally had as it was settling into its new home.
“The Neptune moons we see today were probably broken up and regenerated after the arrival of Triton,” says Showalter.
S/2004 N1 is about 20 kilometres across, and it has a nearly circular orbit that takes it around Neptune in 23 hours. Its orbit is squarely between Proteus, the outermost moon aside from Triton, and Larissa. These moons are 400 and 200 kilometres across, respectively. But in the post-Triton chaos, such a small rock should have been swept up to become part of Proteus, or broken up by interloping asteroids sometime after the system settled down.
“How you can have a 20-kilometre object around Neptune is a little bit of a puzzle,” says Showalter. “It’s far enough away that its orbit is stable. Once you put it there it will stay there. The question is, how did it get there?”
A more immediate question may be what to call this new and unusual moon. Neptune’s other natural satellites are named after minor water deities in Greek and Roman mythology, an official naming convention set up by the International Astronomical Union (IAU). Showalter and colleagues also recently discovered two new moons around Pluto and put their names to a public vote – although the IAU had the final say.
“Compared to work we recently did naming the moons of Pluto, there’s not quite as colourful a cast of characters to work with, but there is still an interesting list of sea creatures one can choose from,” he says.
For now, Showalter and the discovery team do not have a favourite in mind: “We don’t really have a name for it. It’s just ‘that little moon’, because S/2004 N1 does not roll off the tongue.”
More on these topics: | 0.810347 | 3.810732 |
Nothing more was ever seen of the light, so far as any record informs us, until 1865, when Grover, an English observer, caught sight of it again, under circumstances similar to those of its first apparition, and watched it for half an hour, when it once more disappeared. It should be said that, in the case of Dr. Gerling's observation, referred to by Prof. Holden, a "small, round, isolated, conical mountain" was found in the place where the light had been, on the evening following its appearance. It is altogether probable that the gray or black spot perceived by Schroeter was the shadow of a similar mountain, for it is well known that some of the lunar mountains and hills are hardly visible at all except when lateral illumination indicates their position and form by means of the shadows.
Herschel thought he had seen three active volcanoes. If Prof. Holden's discovery accounts for one of these, it is possible that the observations I have just described may give a clew to the others. The phenomenon seen by Schroeter and Grover was located fifty or sixty miles north of the point where Prof. Holden beheld the extraordinary blaze of light last July, and at a point where the mountains, drawing around a culminating peak, confront with tremendous buttresses the broad level of the Mare Imbrium.
The objection has been made by Messrs. Elger and Williams, two competent English observers, that Herschel's volcanoes can not be identical with the glittering peaks seen by either Holden or Gerling, because the latter were observed close to the line of sunrise, where the morning rays touched them, while the phenomena that attracted Herschel's attention were situated far within that part of the disk where the only light came from the earth. But Prof. Holden does not say that the illumination he witnessed was identical in place with those recorded by Herschel, but simply that it was identical in kind. Besides, it must be remembered that, if these luminous appearances are due to peculiar angles of reflection, a similar effect must be produced whether the reflecting surfaces are presented to the sunlight or only to the earth-shine. The difference would be simply in the degree of brightness of the phenomena.
But while the discovery with the Lick telescope may account for Herschel's mistake, it does not clear up the mystery of the cause of these extraordinary lights. In every case quoted above, the illumination was evidently very much greater than that of Aristarchus, the most brilliant of the shining mountains. Proctor estimated that the reflective power of Aristarchus must be equal to that of new-fallen snow. But the mountain-crest observed by Prof. Holden blazed with a dazzling brilliancy that it would be difficult to account for except upon the theory that nearly all of the sunlight falling upon it was reflected to the ob- | 0.811711 | 3.667739 |
May the fifth be with you. Mars InSight, the very first mission to study the deep interior of Mars, has launched. Below, 10 things to know as we head to the heart of the Red Planet.
1. What’s in a name? "Insight" is to see the inner nature of something, and InSight—a.k.a. Interior Exploration using Seismic Investigations, Geodesy and Heat Transport—will do just that. InSight will take the "vital signs" of Mars: its pulse (seismology), temperature (heat flow) and reflexes (radio science). It will be the first thorough check-up since the planet formed 4.5 billion years ago.
2. Marsquakes. You read that right: earthquakes, except on Mars. Scientists have seen a lot of evidence suggesting Mars has quakes, and InSight will try to detect marsquakes for the first time. By studying how seismic waves pass through the different layers of the planet (the crust, mantle and core), scientists can deduce the depths of these layers and what they're made of. In this way, seismology is like taking an X-ray of the interior of Mars.
Want to know more? Check out this one-minute video.
3. More than Mars. InSight is a Mars mission, but it’s also so much more than that. By studying the deep interior of Mars, we hope to learn how other rocky planets form. Earth and Mars were molded from the same primordial stuff more than 4.5 billion years ago, but then became quite different. Why didn’t they share the same fate? When it comes to rocky planets, we’ve only studied one in great detail: Earth. By comparing Earth's interior to that of Mars, InSight's team hopes to better understand our solar system. What they learn might even aid the search for Earth-like exoplanets, narrowing down which ones might be able to support life.
4. Robot testing. InSight looks a bit like an oversized crane game: When it lands on Mars this November, its robotic arm will be used to grasp and move objects on another planet for the first time. And like any crane game, practice makes it easier to capture the prize.
Want to see what a Mars robot test lab is like? Take a 360 tour.
5. The gang’s all here. InSight will be traveling with a number of instruments, from cameras and antennas to the heat flow probe. Get up close and personal with each one in our instrument profiles.
6. Trifecta. InSight has three major parts that make up the spacecraft: Cruise Stage; Entry, Descent, and Landing System; and the Lander. Find out what each one does here.
7. Solar wings. Mars has weak sunlight because of its long distance from the Sun and a dusty, thin atmosphere. So InSight’s fan-like solar panels were specially designed to power InSight in this environment for at least one Martian year, or two Earth years.
8. Clues in the crust. NASA scientists have found evidence that Mars’ crust is not as dense as previously thought, a clue that could help researchers better understand the Red Planet’s interior structure and evolution. “The crust is the end-result of everything that happened during a planet’s history, so a lower density could have important implications about Mars’ formation and evolution,” said Sander Goossens of NASA’s Goddard Space Flight Center in Greenbelt, Maryland.
9. Passengers. InSight won’t be flying solo—it will have two microchips on board inscribed with more than 2.4 million names submitted by the public. "It's a fun way for the public to feel personally invested in the mission," said Bruce Banerdt of JPL, the mission's principal investigator. "We're happy to have them along for the ride."
10. Tiny CubeSats, huge firsts. The rocket that will loft InSight beyond Earth will also launch a separate NASA technology experiment: two mini-spacecraft called Mars Cube One, or MarCO. These suitcase-sized CubeSats will fly on their own path to Mars behind InSight. Their goal is to test new miniaturized deep space communication equipment and, if the MarCOs make it to Mars, may relay back InSight data as it enters the Martian atmosphere and lands. This will be a first test of miniaturized CubeSat technology at another planet, which researchers hope can offer new capabilities to future missions. | 0.809372 | 3.363857 |
Along with Jupiter’s infamous moon Europa, Saturn’s moon Enceladus is one of the most fascinating places in the Solar System, with its huge geysers of water vapour erupting from cracks in the surface at the south pole. The massive plumes are now thought to originate in a subsurface ocean or sea of salty liquid water, similar perhaps to Europa’s underground ocean. Now, new analysis is providing a more detailed look at the chemical makeup of this unique alien environment and its potential to support life.
The Cassini spacecraft orbiting Saturn has made many close flybys of this intriguing moon, including directly through some of the saltwater spray in the plumes themselves (over 100 individual plumes counted to date), “tasting” them as it did so. So far, scientists know that the plumes contain water vapor, ice particles, salts, and organic material. This has already shown that the water below is similar in ways to the water in oceans on Earth. Needless to say, this has caused some excitement among planetary scientists, and the public as well, as it presents the possibility of some form of life existing in the Enceladian ocean. Cassini itself can’t confirm or deny that, but it can provide important clues as to the actual conditions in this strange environment and whether they could support life.
As it turns out, they could, although the ocean may be more salty than most ocean life on Earth is used to. From the press release:
“The model indicates that Enceladus’ ocean is a Na-Cl-CO3 solution with an alkaline pH of ~11-12. The dominance of aqueous NaCl is a feature that Enceladus’ ocean shares with terrestrial seawater, but the ubiquity of dissolved Na2CO3 suggests that soda lakes are more analogous to the Enceladus ocean.”
Basically, the water contains a lot of dissolved sodium carbonate (Na2CO3), a sodium salt. The pH level is higher than usual, about 11-12 (seawater on Earth is typically about 8.08 to 8.33). So, if as indicated by these preliminary studies, the water inside Enceladus is similar to soda lakes on Earth, which are highly alkaline (very salty).
This may sound like a rather inhospitable environment, but at least on Earth, that is not true. Such high-salinity soda lakes host complex ecosystems with a rich variety of prokaryotes (bacteria and archaeabacteria), eukaryotic algae, protists, and fungi. Brine shrimp and fish have also been found in some of the lesser alkaline soda lakes. Some species, known as alkaliphiles, have adapted specifically to the soda lakes and would be unable to live in a more neutral-pH environment. From the published paper:
“Knowledge of the pH dramatically improves our understanding of geochemical processes in Enceladus’ ocean. In particular, the high pH is interpreted to be a key consequence of serpentinization of chondritic rock, as predicted by prior geochemical reaction path models, although degassing of CO2 from the ocean may also play a role depending on the efficiency of mixing processes in the ocean. Serpentinization inevitably leads to the generation of H2, a geochemical fuel that can support both abiotic and biological synthesis of organic molecules such as those that have been detected in Enceladus’ plume.
Serpentinization and H2 generation should have occurred on Enceladus, like on the parent bodies of aqueously altered meteorites; but it is unknown whether these critical processes are still taking place, or if Enceladus’ rocky core has been completely altered by past hydrothermal activity. The presence of native H2 in the plume would provide strong evidence for contemporary aqueous alteration. The high pH also suggests that the delivery of oxidants from the surface to the ocean has been sporadic, and the rocky core did not experience partial melting and igneous differentiation. On the other hand, the deduced pH is completely compatible with life as we know it; indeed, life on Earth may have begun under similar conditions, and terrestrial serpentinites support thriving microbial communities that are centered on H2 that is provided by water-rock reactions. These considerations provide major motivation for future missions to explore Enceladus as a habitable world, whether past or present.”
On Earth, soda lakes tend to be found in arid and semi-arid regions and in connection to tectonic rifts. Photosynthesis is the primary energy source for the lakes’ inhabitants, although deeper down, anoxygenic photosynthesizers and sulfur-reducing bacteria are also common. Similar kinds of non-carbon dioxide energy sources, including sulfur or nitrogen, would be required in oceans such as those in Enceladus or Europa, where no sunlight can reach the water below due to the surface ice crust.
Such a high-salinity ocean might not be the most ideal environment as far as life as we know it is concerned, but it is by no means a show-stopper, as the soda lakes on Earth have shown. If life ever started in the Enceladus ocean, there is seemingly no reason why it couldn’t have evolved and adapted to its environment. Cassini has already found organics in the watery plumes; could there be life itself? The only way to know will be to return to this moon with a spacecraft able to search for biomarkers in the plumes or even microorganisms themselves, which might get ejected out from the water below. Either would, of course, be a fantastic discovery.
This article was first published on AmericaSpace. | 0.828133 | 3.899594 |
Four billion miles from the sun floats Ultima Thule, an icy celestial body that NASA scientists announced Wednesday is aptly shaped like a giant snowman.
The first detailed images beamed back from the US agency's New Horizons mission allowed scientists to confidently determine the body was formed when two spheres, or "lobes," slowly gravitated towards each other until they stuck together - a major scientific discovery.
The New Horizons spacecraft on Tuesday flew past Ultima Thule, which was discovered via telescope in 2014 and is the farthest and potentially oldest cosmic body ever observed by a spacecraft.
Before that flyby, the only image scientists had was a blurry one showing Ultima Thule's oblong shape, resembling something like a bowling pin or a peanut.
"That image is so 2018... Meet Ultima Thule!" said lead investigator Alan Stern, doing little to hide his joy as he revealed a new sharper image of the cosmic body, taken at a distance as close as 17,000 miles (about 27,000 kilometers) with a resolution of 140 meters per pixel.
"That bowling pin is gone - it's a snowman if anything at all," Stern said during a NASA briefing.
"What this spacecraft and this team accomplished is unprecedented."
Ultima Thule's surface reflects light about as much as "garden variety dirt," he said, as the sun's rays are 1,600 times fainter there than on Earth.
The body is roughly 19 miles long and completes its own rotation in about 15 hours. NASA dubbed the larger lobe Ultima, and the other, which is about three times smaller, Thule.
"This is the first object that we can clearly tell was born this way" Stern said, instead of evolving as a sort of "bi-lobe."
"This really puts the nail on the coffin now. We know that this is how these kinds of objects in many cases form."
'A time machine'
Some 4.5 billion years ago a cloud of frozen pebbles began to join forces, gradually forming two bodies - Ultima and Thule.
Slowing turning, they eventually touched at each other at what mission geology manager Jeff Moore called an "extremely slow speed" - maybe just one to a few miles per hour.
If such a meeting occurred between two cars in a parking lot, he said, no driver would bother writing it up. The lobes, according to Moore, are really just "resting on each other."
"New Horizons is like a time machine, taking us back to the birth of the solar system," Moore said. "We are seeing a physical representation of the beginning of planetary formation, frozen in time."
Carly Howett, another researcher of the mission, noted that "we can definitely say that Ultima Thule is red," perhaps due to irradiation of ice.
NASA researchers promised fresh announcements would drop Thursday, including on the composition and atmosphere of Ultima Thule, as new images with even more precise resolution have come through.
Follow Emirates 24|7 on Google News. | 0.916985 | 3.472271 |
In a finding that has given new and stronger clues on possibility of life on other planets, a group of scientists has found that the age of water present in the Earth’s ocean, meteorites and their frozen form in lunar craters much older than the birth of the solar system.
The issue of ‘origin of water in the solar system’ had been rigorously debated for so many years as the scientists were clueless about whether they came from ice ionized at the time of formation of the solar system or if the water was present much before the birth of the solar system and originated in the cold interstellar cloud of gas that led to the formation of the sun.
“It’s remarkable that these ices survived the entire process of stellar birth.” lead researcher Lauren Cleeves, from the University of Michigan said.
Cleeves, a doctoral student, have been researching on how galactic cosmic rays, radioactivity and other phenomena of high-energy impact planet-forming disks and contribute to the formation of celestial bodies.
According to Cleeves, 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 these ices could have come from was the chemically rich interstellar gas that led to the formation of the solar system.
For the in-depth study, the researchers ran computer models in order to compare ratios of hydrogen with deuterium, a heavier isotope of the gas (hydrogen) that has been enriching the water on the solar system over time.
Following the experiment, the researchers concluded that in order to reach the ratios present in the Earth’s ocean water as well as comets and meteorite samples, there is huge possibility that at least some of the water would have had to be formed before the birth of the sun.
The researchers highlighted that the finding’s conclusion provides strong evidence to the possibility of similar process on other solar systems too, making them ideal for supporting life.
Also this week, a second paper in Science notes the discovery of a branched carbon-containing molecule involved in the creation of stars.
Study researcher Arnaud Belloche, from Germany’s Max Planck Institute for Radio Astronomy, said, “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.”
The findings of the study were published in the latest issue of the journal Science. | 0.844605 | 3.79631 |
I remember that analogous findings have been made for spin directions of distant stars but now distances are indeed enormous, larger than the length scale .1 billion years for the large voids. Also the stars are aligned along lines.
TGD explanation is one of the oldest pieces of TGD inspired cosmology and was originally proposed as an explanation for why galaxies are arranged like pearls in necklace. Key players in the model are of course cosmic strings thickened to flux tubes during cosmic evolution so that their magnetic fields and energy densities reduced. Living matter would be full of them! This would be the new element needed to explain the findings.
The cosmic strings preceded the visible matter resulting in their partial decay when space-time in the usual sense formed from the soup of cosmic strings (string-like 4-D surfaces with only 2 big dimensions). String gas condensed to form space-time (analog of inflationary period) and radiation dominated cosmology emerged. Elementary particles emerged as energy of cosmic string. In inflation theory they are believed to emerge from inflation fields for which there is however no support.
Expanding cosmic strings would be still there ands since they carry topological monopole fluxes (made possible by CP2 geometry) give rise to magnetic fields in all scales without need for currents to create them: the existence of these magnetic fields is a mystery in standard cosmology. Their magnetic energy is the mysterious dark energy and their description in TGD framework requires small cosmological constant. Also galactic dark matter could be mostly dark magnetic energy assignable to the galactic dark string going through the galaxy: this explains elegantly the constant velocity spectrum of distant stars in galactic plane.
Quasars and also other matter in scale of billions of light years results as decay products of cosmic strings and quasars formed kind of pearls in necklaces defined by cosmic strings. The interactions of primordial quasars with cosmic strings and each other at time when they were near to each other implies strong correlations between spins of these objects. The main deviation from standard cosmology is that the seeds of stars existed already during transition to radiation dominated era.
The parallel spins of quasars could originate from that of cosmic string. The simplest cosmic string is at rest in comoving coordinates (Robertson-Walker coordinates) and is parallel to x axis as one goes to plus/minus infinity but has kink near origin (sigma curve) (see this). In local Minkowski coordinates it appears to be differentially rotating since cosmic radial coordinate r is expressible as r= rM/a, a the cosmic time, and therefore depends on time since angle coordinate Φ along string is function of r and thus of rM/a, and therefore of cosmic time.
The quasars could be generated in the region in two strings have made a close encounter: the center of Milky Way gives support for this. The angular momentum and energy lost by cosmic string goes to the quasars and they start to spin in the same direction as cosmic strin rotates locally. Analogous mechanism could explain why planets tend to rotate in same direction. | 0.815325 | 4.022644 |
- Title: Towards Building a Crowd-Sourced Sky Map
- Authors: Dustin Lang, David W. Hogg, Bernhard Schölkopf
- First Author’s Institution: Carnegie Mellon University
- Status: Presented at 17th Annual Conference on Artificial Intelligence and Statistics
I live in Northern Idaho, where it is very sparsely populated, a great place for star viewing. Recently I was so struck by the bright swath of the Milky Way that I took my fiancé’s camera and snapped a great picture of…nothing: it was too dim. I leaned over and showed her, and she did a little magic with a dial and a button and we took another. This time we set the camera on a rock, and the shutter stayed open for several minutes. The result was a clear field of stars–but still no lovely swath of galaxy, that would have required an even longer exposure.
Professional astronomers battle the same problem. In most cases, they’re trying to record much fainter sources of light than we were. Deep images of distant galaxies usually take several hours of exposure time. That’s hard to get, but the science is worth it. Take as an example recent observations by Martinez-Delgado and colleagues which have revealed previously unknown tidal streams around normal looking massive galaxies (Fig. 1). These images strengthen the case that all large spiral galaxies have had a history of mergers.
Today’s authors present a way to get deep images without telescope time. Their method involves a clever compilation of sky images from the Web. The algorithm, called Enhance, synthesizes a collection of (usually) short-exposure images gleaned from the Web to produce a deep image.
This is much harder than it sounds. Images have different noise backgrounds. Some have text on them. Some have saturated regions (pixel brightness is maxed out). They might be false-color, representing x-rays or radio light. Worst of all, most digital images have had nonlinear filters applied (like gamma correction), so that the luminosity of each patch of sky cannot be recovered from pixel values.
But Enhance circumvents all these problems by focusing on the pixels themselves, bringing out subtle contrasts in both bright areas and dark areas. Enhance allows a large pool of images to ‘vote’ for the rankings of each pixel’s brightness, whether or not that pixel is representing optical or infrared or some other wavelength of light. Color images are broken into red, green, and blue components and treated individually. The consensus image is built from the pixel ranking that most images ‘agree’ upon.
As a demonstration of their method, they gathered images of NGC 5907 from the Interweb, literally searching for “NGC 5907” and “NGC5907” on flickr, Bing, and Google. Then they used automated astrometry software to register each image to its celestial coordinates, discarding those that failed, or those that were images of different patches of sky. They resampled the remaining 298 unique images onto a rectangular grid centered on the galaxy, and finally histogram-matched them. An image histogram displays the distribution of brightness values across the image. So this last step sloshed pixels up and down in brightness until there was the same amount of light and dark in each image; but, note, each pixel preserved its original rank in order of brightness. The resulting images were fed to their voting algorithm.
Lang and coauthors chose this particular galaxy for their demonstration because it is known to host faint tidal streams, but only recently known. (Actually the discovery was made by Martinez-Delgado and colleagues from above.) To pour water on the altar, they manually removed any reproductions of the recent long-exposure images by Martinez-Delgado et al. from their input pool. As you can see in Fig. 2, Enhance readily uncovered the tidal streams from the 298 input images in which it is not, or only faintly visible!
There are some interesting technical details to the Enhance algorithm. For instance, as I mentioned, the images must be registered to their celestial coordinates. This is done by an automated web service called Astrometry.net. It was developed by two of the authors. You can use it too! In exchange for uploading an image to their server, you receive a version annotated with all the interesting objects in your field of view.
I’d still rather step outside to look at the Milky Way. But it’s exciting to discover that Enhance can build scientifically interesting images from all the bits laying around on Web. | 0.840147 | 3.817584 |
pulsational pair-instability supernova
abar-now-axtar-e nâpâydâri-ye tapeši-ye joft
Fr.: supernova à instabilité pulsationnelle de paires
A → supernova resulting from the → pair instability that generates several successive explosions. According to models, a first pulse ejects many solar masses of hydrogen layers as a shell. After the first explosion, the remaining core contracts and searches for a stable burning state. When the next explosion occurs a few years later, several solar masses of material are again ejected, which collide with the earlier ejecta. This collision can radiate 1050 erg of light, about a factor of ten more than an ordinary → core-collapse supernova. After each pulse, the remaining core contracts, radiates neutrinos and light, and searches again for a stable burning state. Later ejections have lower mass, but have higher energy. They quickly catch up with the first shell, where the collision dissipates most of their kinetic energy as radiation. The first SNe from → Population III stars are likely due to pulsational pair instability (Woosley et al. 2007, Nature 450, 390). See also → pair-instability supernova.
1) In the → eye, the apparently black opening in the center of the
→ iris that permits light to pass and be focused on the
From M.E. pupille, from O.Fr. pupille, from L. pupilla, originally "little girl-doll," diminutive of pupa "girl, doll" (Fr. poupée), so called from the tiny image one sees of himself reflected in the eye of another.
Mardomak "little man," the allusion being to the tiny image of himself reflected in the eye of another, from mardom "man, human being, mankind, people;" → people, + diminutive suffix -ak.
Fr.: masquage de pupille
A method for reaching the → diffraction-limited → angular resolution of a monolithic telescope by using an → interferometric technique. A mask with several small openings is placed in the telescope pupil plane or in a conjugated plane so as to only pass light from selected regions, thus transforming the telescope into an array of small subapertures without redundancy. When the light from each of these separate subapertures is combined, → interference fringes are formed which encode information on the spatial structure of the source (Haniff et al. 1987, Nature 328, 694). Coupled with a novel technique which filters the → atmospheric turbulence through fibers, pupil masking allows reaching a high dynamic range (Perrin et al. 2006, MNRAS 373, 747), which is necessary for detecting very faint objects, such as → exoplanets, adjacent to bright stars.
The Stern. One of the larger constellations of the southern hemisphere representing the stern of the ship Argo Navis, located at 7h 30m right ascension, 40° south declination. Its brightest star is → Naos. Abbreviation: Pup; genitive: Puppis.
From L. puppis "stern, poop, the rear, or aft part of a ship or boat."
Pasâl, from pas "behind" (e.g.: pas-e pardé
"behind the curtain"), variant pošt "back; the back;
behind" (Mid.Pers. pas "behind, before, after;"
O.Pers. pasā "after;" Av. pasca "behind (of space);
then, afterward (of time);" cf. Skt. paścā "behind,
after, later;" L. post, as above; O.C.S. po "behind,
after;" Lith. pas "at, by;" PIE *pos-, *posko-) +
-âl, → -al. → prow = farâl
Fr.: Puppis A
A → supernova remnant in the constellation → Puppis, and one of the brightest sources in the X-ray sky. The → supernova occurred about 4000 years ago at a distance of about 6,000 light-years. Also called SNR G260.4-03.4. Its X-ray designation is 2U 0821-42.
cahârtâ (#), cahârtâyi (#)
Fourfold; consisting of four parts.
M.E. from L. quadruplus, from quadru- + duple, from duplus, from du(o) "two" + -plus "fold."
Cahârtâ, from cahâr, → four, cognate with L. quattuor, + tâ "fold, plait, ply; piece, part" (Mid.Pers. tâg "piece, part").
Fr.: système quadruple
A stellar system consisting of four stars orbiting around a common → center of mass.
cahârqotbé (#), cahârqotbe-yi (#)
A set of either two → electric dipoles or two → magnetic dipoles in close proximity to each other arranged with alternating polarities and acting as a single unit. Quadrupole interactions are much smaller than dipole interactions, but can allow transitions forbidden in dipole moment transitions.
Fr.: anisotropie quadrupolaire
The → anisotropy which is at the origin of the → cosmic microwave background polarization. The quadrupole anisotropy could arise from three types of perturbations: → scalar perturbation, → vector perturbation, and → tensor perturbation
Fr.: lentille quadrupôle
Fr.: moment quadrupolaire
A quantity characterizing an electric charge distribution, determined by the product of the charge density, the second power of the distance from the origin, and a spherical harmonic over the charge distribution.
Fr.: amas du quintuplet
A bright → open cluster of stars located within 100 light-years of the center of the Milky Way Galaxy, and one of the three → Galactic center clusters. The Quintuplet cluster was originally noted for its five very bright stars, but it is now known to contain many luminous → massive stars that are not detected at visible wavelengths due to heavy extinction by dust along the line of sight. The cluster is about 4 million years old and had an initial mass over 104 solar masses. The five brighter stars of the cluster are dusty → WC Wolf-Rayet stars. The Quintuplet cluster also contains two → Luminous Blue Variables, the Pistol star and FMM362. The Pistol star has a luminosity 107 times solar making it one of the most luminous stars known. The Quintuplet cluster is more dispersed than the nearby → Arches cluster.
Quintuplet, from the five brightest stars originally observed; → cluster.
abarqul-e sorx (#)
Fr.: supergéante rouge
A supergiant star with spectral type K or M. Red supergiants are the largest stars in the Universe, but not necessarily the most massive. Betelgeuse and Antares are the best known examples of a red supergiant.
pâregi (#) , gosast (#)
From L. ruptura "the breaking (of an arm or leg), fracture," from p.p. of rumpere "to break."
jofteš-e Russell-Saunders, jafsari-ye ~
Fr.: couplage Russell-Saunders
A coupling scheme of → electron configuration, used mainly for the lighter atoms with → atomic number less than 30. In an atom when changes in energy states are produced by the action of two or more electrons, the value of the total angular momentum of these electrons results from the coupling between the total → orbital angular momenta of the electrons and the total → spin angular momenta of the electrons. In this scheme the orbital angular momenta and spin angular momenta of electrons are added separately to give the total angular momentum L = Σi li and the total electron spin angular momentum S = Σi si. These are then added to give J = L + S. Also called → LS coupling. See also → jj coupling.
After Henry Norris Russell (1877-1957) and Frederick Albert Saunders (1875-1963), American astronomers (1925, ApJ 61, 38); → coupling.
In computer science, to increase the processing power of the same node/system by increasing its resources (CPU, RAM, etc.). This is a type of → vertical scaling opposite to → scale down. For example, instead of a machine with a CPU running at speed of X and having Y gigabytes of memory, use a machine with a CPU running at speed of 4X and a memory of 4Y gigabytes. See also → scale in, → scale out.
Fr.: groupe du Sculpteur
The nearest group of galaxies to our → Local Group, lying near the south Galactic pole at about 10 million → light-years distance. The Sculptor Group is dominated by five galaxies, four spiral (NGC 247, 253, 300, and 7793) and one irregular (NGC 55). The brightest of the five is NGC 253. The nearest galaxy in this group is NGC 55 which at a distance of 5 million light-years lies on the border of the Local Group.
Fr.: deuxième dragage
A → dredge-up process that occurs after core helium burning, in which the convective envelope penetrates much more deeply, pushing hydrogen burning shell into close proximity with the helium burning shell (→ first dredge-up). This arrangement is unstable and leads to burning pulses. The reason is that the hydrogen shell burns out until there is enough helium for the helium combustion to occur and all the helium is rapidly burnt. Afterward the hydrogen shell again burns outward and the process repeats.
From sextuple, from L. sext(us) "sixth," → six, + et | 0.90362 | 3.948218 |
A 211-year-old mystery has finally been solved by an astronomy historian, who's identified the person responsible for naming those rocky objects orbiting between Mars and Jupiter.
The first years of the 19th century were glorious ones for astronomy. In 1800 William Herschel, already famous for spotting Uranus in 1781, found that the Sun emits infrared energy. The next year Johann Ritter followed with the discovery of ultraviolet light.
Meanwhile, Europe's scientific circles were abuzz about the realization that not one but two planet-like objects were orbiting the Sun between Mars and Jupiter. Astronomers had suspected as much — after all, the numerical orbit spacings produced by the Titius-Bode Law had predicted that a planet should be lurking there.
In fact, a dozen astronomers, handpicked by Baron Franz Xaver von Zach and nicknamed the "Celestial Police," were readying to search for this undiscovered world when, on January 1, 1801, Giuseppe Piazzi spotted the long-sought interloper using a small refractor atop the royal palace in Palermo, Italy. At first, Piazzi thought he'd found a comet, but it later proved to be Ceres. A second body in that same region, Pallas was found on March 28, 1802.
But neither was truly a planet. Herschel used a special projection system to estimate that Ceres was only 162 miles (260 km) across and Pallas just 147 miles (237 km).
So what were they? Herschel has long been credited with coining the term asteroids, derived from a Greek word meaning "starlike," because he introduced the term at a meeting of London's Royal Society in May 1802 and later published it in the Society's Philosophical Transactions.
But according to astronomy historian Clifford Cunningham (National Astronomical Research Institute of Thailand), "Asteroid was Herschel's choice, but it was not his creation." Documents found by Cunningham in Yale's Beinecke Rare Book and Manuscript Library show that credit instead goes to a little-known Greek specialist named Charles Burney Jr.
As Cunningham learned, Herschel was casting about for a suitable name for the new bodies and had reached out to Dr. Charles Burney Sr, a close friend and colleague. Burney in turn quickly wrote to his son, who at the time was one of England's preeminent Greek scholars. The correspondence between them shows that the father had proffered suggestions like stellula (the diminutive of stella) before concluding, "It must not be a big name for so small a star."
The son's reply didn't turn up during Cunningham's research. What did, however, was a later letter from the senior Burney to Frances Crewe, discussing Herschel's just-published report about Ceres and Pallas in Philosophical Transactions. "They are not allowed by Herschel to be either Planets or Comets," Burney writes, "but asteroids, italick, a kind of star — a name [which] my son, the Grecian, furnished."
Herschel chose asteroid over other contenders (such as planetkin, planeret, and planetling), but he wasn't thrilled with it. At one point he asked his close friend Sir Joseph Banks, then president of the Society, to come up with a better word. Banks, in turn, contacted Stephen Weston, who came up with the word aorate. "Herschel rejected this as well," Cunningham explains, "accepting asteroid as the best of a bad lot of ideas."
One problem is that Herschel's colleagues still thought of Ceres and Pallas as planets, so a new moniker simply wasn't needed. "The abuse heaped on Herschel for introducing the word asteroid was unparalleled in the history of astronomy," Cunningham says. "It was not just a rejection — it was outrage, ridicule and contempt." Only Wilhelm Olbers, who'd found Pallas, embraced Herschel's choice. Piazzi preferred planetoid, but by then Herschel's Royal Society paper had been published.
"It has taken me 30 years of research into Herschel and the asteroids to uncover this," notes Cunningham. (You can follow some of that quest in his 2001 book, The First Asteroid.) Cunningham presented his findings three weeks ago at a meeting of the American Astronomical Society's Division for Planetary Sciences.
Meanwhile, come February 2015 we'll know whether planetoid would have been the better choice. That's when NASA's Dawn spacecraft finally reaches Ceres (actually about 600 miles across) and begins several months of intense scrutiny of the asteroid belt's largest member. | 0.87026 | 3.806353 |
The accelerated expansion of the universe pushes resources away from us at an ever-growing speed. Once the universe will age by a factor of 10, all stars outside our Local Group of galaxies will not be accessible to us as they will be receding away faster than light. Is there something we can do to avoid this cosmic fate?
Following the lesson from Aesop’s fable “The Ants and the Grasshopper,” it would be prudent to collect as much fuel as possible before it is too late, for the purpose of keeping us warm in the frigid cosmic winter that awaits us. In addition, it would be beneficial for us to reside in the company of as many alien civilizations as possible with whom we could share technology, for the same reason that animals feel empowered by congregating in large herds.
After writing a few papers on the gloomy cosmic isolation that is expected in our long-term future (they appear here, here, here and here), I received an optimistic e-mail from Freeman Dyson in 2011 where he suggested contemplating a vast “cosmic engineering” project, in which we (in collaboration with any neighboring civilizations, if they exist and cooperate) will concentrate matter from a large-scale region around us to a small enough volume such that it will stay bound by its own gravity and not expand with the rest of the universe.
A similar idea was discussed very recently by Dan Hooper, who suggested using the energy output from sunlike stars to concentrate them across tens of millions of light years. Unfortunately, smaller stars do not produce sufficient power to traverse such distances fast enough. But there are additional limitations to this approach. First, we do not know of any technology that enables moving stars around, and moreover sunlike stars only shine for about 10 billion years (of order the current age of the universe) and cannot serve as nuclear furnaces that would keep us warm into the very distant future.
Fortunately, Mother Nature was kind to us as it spontaneously gave birth to the same massive reservoir of fuel that we would have aspired to collect by artificial means. Primordial density perturbations from the early universe led to the gravitational collapse of regions as large as tens of millions of light years, assembling all the matter in them into clusters of galaxies—each containing the equivalent of a thousand Milky Way galaxies.
Therefore, an advanced civilization does not need to embark on a giant construction project as suggested by Dyson and Hooper, but only needs to propel itself towards the nearest galaxy cluster and take advantage of the cluster resources as fuel for its future prosperity. The nearest cluster to us is Virgo, whose center is about 50 million light years away. Another massive cluster, Coma, is six times farther.
For the above reasons, advanced civilizations throughout the universe might have migrated towards clusters of galaxies in recent cosmic history, similarly to the movement of ancient civilizations towards rivers or lakes. Once settled in a cluster, a civilization could hop from one star to another and harvest their energy output just like a butterfly hovering over flowers in a hunt for their nectar.
The added benefit of naturally produced clusters is that they contain stars of all masses, much like a cosmic bag that collected everything from its environment. The most common stars weigh a tenth of the mass of the sun, but are expected to shine for a thousand times longer because they burn their fuel at a slower rate. Hence, they could keep a civilization warm for up to 10 trillion years into the future. The nearest examples of dwarf stars in the form of Proxima Centauri or TRAPPIST-1 are known to host habitable Earth-size planets around them, implying that these abundant stars offer attractive parking spots for civilizations that rely on liquid water.
Are there many advanced civilizations out there? Cosmic modesty would suggest an answer in the affirmative, as long as these civilizations do not destroy themselves too quickly (in which case, Darwinian evolution would favor those who are smart enough to sustain longevity). Can we see signs for their long journeys across the cosmic web as their spacecrafts flock collectively on their way towards clusters of galaxies? Probably not, unless they produce powerful beacons of light (for propulsion through lightsails or for communication) that are detectable across the vast cosmological scales.
Some lucky civilizations were born in clusters and inherited the resources around them without the need to travel. Could others develop the technology that would enable them to reach the nearest galaxy cluster fast enough? In order to traverse a hundred million light years within the age of the universe, their spacecrafts need to exceed a percent of the speed of light.
This is over a hundred times faster than the speed of all chemical rockets launched thus far by our civilization into space. The Starshot Initiative is the first well-funded attempt to develop the technology to propel a spacecraft to a significant fraction of the speed of light. If successful, our civilization could contemplate a future journey to the Virgo or Coma clusters.
This would be an impressive feat of long-term planning. When looking at photo albums that are billions of years old, our descendants might reminisce on the early millennia that their early technological civilization spent within the Milky Way galaxy. By then, that birth site will be receding away from them at an ever-increasing speed until its image will freeze and fade away for eternity. | 0.827652 | 3.781683 |
Canis Major is a constellation in the southern sky. Its name means “the greater dog” in Latin.
Canis Major represents the bigger dog following Orion, the hunter in Greek mythology. The dog is often depicted pursuing a hare, represented by the constellation Lepus. The smaller dog is represented by the neighboring constellation Canis Minor. Both constellations were first catalogued by Ptolemy in the 2nd century.
Canis Major is home to Sirius, the brightest star in the sky, as well as to several notable deep sky objects: the Canis Major Dwarf Galaxy, the open cluster Messier 41, the emission nebula NGC 2359 (also known as Thor’s Helmet), and the colliding spiral galaxies NGC 2207 and IC 2163.
FACTS, LOCATION & MAP
Canis Major is the 43rd biggest constellation in the sky, occupying an area of 380 square degrees. It is located in the second quadrant of the southern hemisphere (SQ1) and can be seen at latitudes between +60° and -90°. The neighboring constellations are Columba, Lepus, Monoceros, and Puppis.
Canis Major contains one Messier object, the star cluster Messier 41 (NGC 2287), and has four stars with known planets. The brightest star in Canis Major, Sirius (Alpha Canis Majoris), is also the brightest star in the night sky. There are no meteor showers associated with the constellation.
Canis Major is commonly taken to represent the “greater dog” following the hunter Orion in Greek myth. The constellation is depicted as a dog standing on its hind legs, pursuing a hare, represented by the constellation Lepus.
Canis Major was described by Manilius as “the dog with the blazing face” because the dog appears to hold Sirius, the brightest star in the sky, in its jaws.
In mythology, Canis Major is associated with Laelaps, the fastest dog in the world, one destined to catch anything it pursued. Zeus gave Laelaps to Europa as a present, along with a javelin that could not miss. The gift proved to be an unfortunate one, as Europa herself was killed accidentally by her husband Cephalus, who was out hunting with the javelin.
Cephalus took the dog to Thebes in Boeotia (a Greek province north of Athens) to hunt down a fox that was causing some trouble there. Like Laelaps, the fox was extremely fast and was destined never to be caught. Once the dog found the fox and started chasing it, the race did not appear to have an end in sight. Zeus himself finally ended it and turned both animals to stone. He placed the dog in the night sky as the constellation Canis Major.
MAJOR STARS IN CANIS MAJOR
Sirius – α Canis Majoris (Alpha Canis Majoris)
Sirius, also known as the Dog Star, is the brightest star in the sky and the fifth nearest star system to the Sun. Sirius is a binary star with an apparent magnitude of -1.42. It is only 8.6 light years distant.
The brighter component, Sirius A, is a white main sequence star and the companion, Sirius B, is a white dwarf that orbits the primary every 50 years. The distance between the two stars varies between 8.1 and 31.5 astronomical units. The companion is not visible to the naked eye.
Sirius A belongs to the spectral class A1V, and the dwarf to DA2. Sirius A has twice the mass of the Sun and is 25 more luminous. Sirius B is almost equal to the Sun in mass (0.98 solar masses) and is one of the most massive white dwarfs known.
Sirius A has an absolute visual magnitude of 1.42 and Sirius B, 11.18. The age of the star system is estimated to be between 200 and 300 million years.
The name Sirius comes from the Greek Σείριος (Seirios), which means “scorching,” “glowing” or “searing.” In ancient times, the star rose just before sunrise during the hottest summer period, the so-called Dog Days. Greeks and Romans believed the star was somehow responsible for the summer heat.
In Egypt, Sirius marked the flooding of the Nile. The star’s heliacal rising, just before the annual flooding and the summer solstice, played a crucial role in the Egyptian calendar during the Middle Kingdom era.
Along with the stars Rigel in Orion, Aldebaran in Taurus, Capella in Auriga, Pollux/Castor in Gemini, and Procyon in Canis Minor, Sirius forms the Winter Hexagon (or Winter Circle) asterism, which appears prominently in the northern sky between December and March.
Adhara – ε Canis Majoris (Epsilon Canis Majoris)
Adhara is the second brightest star in Canis Major and the 24th brightest star in the night sky. Its name comes from the Arabic aðāra, which means “virgins.” It is a binary star that lies about 430 light years from Earth.
The primary component belongs to the spectral class B2 and has an apparent magnitude of 1.5. It is one of the brightest known ultraviolet sources in the sky. The companion star has an apparent magnitude of 7.5 and is located 7.5’’ away from the primary.
About 4.7 million years ago, Adhara was the brightest star in the sky. It was only 34 light years distant and had a magnitude of -3.99. No other star has ever been as bright since, nor is one expected to be in the next five million years.
Wezen – δ Canis Majoris (Delta Canis Majoris)
Wezen is a yellow-white F-type supergiant approximately 1,800 light years distant. It has an apparent magnitude of 1.83. It is the third brightest star in Canis Major. Wezen can be found about 10 degrees southeast of Sirius. Its name is derived from the Arabic al-wazn“, meaning “the weight.” The star’s estimated age is 10 million years, which means that it will become a red supergiant within the next 100,000 years, and eventually a supernova.
Murzim – β Canis Majoris (Beta Canis Majoris)
Murzim (Al-Murzim, Mirzam) is a blue-white giant with brightness varying between magnitude 1.95 and 2.00. It is approximately 500 light years distant. The star’s name comes from the Arabic word for “the herald,” presumably referring to Murzim’s position in the sky. (The star rises before Sirius, i.e. it heralds it.)
Murzim is classified as a Beta Cephei variable, a star that exhibits variations in brightness as a result of pulsations of its surface.
Aludra – η Canis Majoris (Eta Canis Majoris)
Aludra is an Alpha Cygni type variable star, with luminosity varying between magnitude 2.38 and 2.48. It is a blue supergiant, approximately 3,000 light years distant, and already approaching the final stages of its life. It is expected to become a supernova within the next few million years.
The star’s name is derived from the Arabic al-‘aðrā, meaning “the virgin.” Along with Adhara, Wezen and Omicron-2 Canis Majoris, Aludra was one of the stars known as the Virgins.
τ Canis Majoris (Tau Canis Majoris)
Tau CMa is an eclipsing spectroscopic binary star about 3,200 light years from Earth. It is the brightest star of the open cluster NGC 2362 (Caldwell 64), which is why the cluster is sometimes called the Tau Canis Majoris Cluster.
The star is an O-type blue supergiant classified as a Beta Lyrae type variable. Its brightness varies between magnitude 4.32 and 4.37 with a period of 1.28 days.
Phurud – ζ Canis Majoris (Zeta Canis Majoris)
Phurud (or Furud) is a spectroscopic binary star. Its name comes from the Arabic phrase al-furud, which means “the solitary ones.” The star lies about 336 light years from Earth and has an apparent magnitude of 3.02.
The brighter component is a blue-white B-type main sequence dwarf. The companion is an unseen star. The two orbit around a common centre once every 675 days.
Muliphein – γ Canis Majoris (Gamma Canis Majoris)
Muliphein is a blue-white B-type right giant, approximately 402 light years distant. It has an apparent magnitude of 4.11.
DEEP SKY OBJECTS IN CANIS MAJOR
Messier 41 (M41, NGC 2287)
M41 is an open cluster located four degrees south of Sirius. It is 25-26 light years in diameter and between 190 and 240 million years old.
The cluster contains about 100 stars, with the brightest one being a K3-type giant located near the centre of the cluster. M41 also contains several red giants.
The cluster is approximately 2,300 light years distant. It has an apparent magnitude of 4.5. It was discovered by the Italian astronomer Giovanni Batista Hodierna in the 17th century.
Canis Major Dwarf Galaxy
The Canis Major Dwarf Galaxy (CMa Dwarf) is an irregular galaxy, roughly elliptical in shape, that is believed to be the nearest neighbouring galaxy to the solar system.
It is approximately 25,000 light years distant from Earth and 42,000 light years away from the Galactic Centre.
The Canis Major Dwarf Galaxy contains about a billion stars, among them a significant number of red giants. The galaxy was first discovered in 2003 by an international team of astronomers. It is a difficult object to observe because it lies behind the plane of the Milky Way, obscured by stars, dust and gas.
Because the galaxy’s main body is highly degraded, the Canis Major Dwarf is believed to be severely affected by the Milky Way’s gravitational field.
There are a number of globular clusters associated with the galaxy, among them NGC 1851, NGC 1904, and NGC 2808. These clusters are thought to be remnants of the dwarf’s globular cluster system before the galaxy started getting pulled apart and swallowed into the Milky Way.
NGC 2359 – Thor’s Helmet
NGC 2359 is an emission nebula in Canis Major. It is about 30 light years in size, and some 15,000 light years distant from Earth.
The nebula is formed around the central Wolf-Rayet star, an extremely hot giant which is about to explode as a supernova.
NGC 2207 and IC 2163
NGC 2207 and IC 2163 are colliding spiral galaxies in Canis Major. They are approximately 80 million light years distant. The galaxies were discovered by the English astronomer John Herschel in 1835. They have apparent magnitudes of 12.2 and 11.6, respectively.
Three supernovae have been observed in NGC 2207 in recent decades; SN 1975A in 1975, SN 1999ec in 1999, and SN 2003H in 2003.
The galaxies are in the process of tidal stripping, with the larger galaxy pulling stars and other material from the smaller one. | 0.825307 | 3.514168 |
Japan’s Hayabusa 2 spacecraft has begun the asteroid mining era with a bang. Earlier this morning, hovering 500 metres above the surface of the asteroid Ryugu, it shot a copper projectile packed with explosives towards the rocky landscape.
It is expected that when the projectile reached about 3.5 metres above the surface, it exploded and sent up debris into the asteroid’s orbit, creating a fresh crater. Mission scientists are waiting for confirmation, though images suggest the mission was a success (see below).
Before the explosion occurred, Hayabusa 2 manoeuvred around to the other side of the rock to avoid being blasted by the dust. Later, it will collect a sample for return to Earth.
The creation of this crater is just one part of the spacecraft’s mission. Since it arrived at Ryugu in June 2018, Hayabusa 2 has dropped two hopping landers, collectively known as MINERVA-II, onto the surface of the space rock to take pictures and measure the asteroid’s temperature. They sent back stunning images of light skimming over the rocky surface.
The main spacecraft also touched down on the asteroid in February and fired a bullet into the ground, spraying up dust that it collected as it ascended again.
The latest blast aimed to probe beneath the surface and toss up particles that haven’t been altered by millions or even billions of years of exposure to cosmic radiation.
Ryugu is small – less than a kilometre across – and a relic from the formation of our solar system. Studying the material that makes it, in as pure a form as possible, could help us learn about the make-up of early planets and sort out how water and other materials crucial for life came to Earth.
In July 2019, the spacecraft will release another set of rovers onto the asteroid, and in November it will begin its journey back to Earth.
More on these topics: | 0.851901 | 3.25054 |
Just as QM is the theory of the very small, Relativity is the theory of very large dimensions.
As usual, if this page gets to be too much, try the simpler version. This one is recommended, though.
In fact, there are two theories of relativity. The simpler, first one, called Special Relativity (SR), is about space-time, relative movement and the speed of light. It says:
- the equations of physics are the same (invariant, in math-physics speak) for all observers who are moving with uniform steady motion relative to each other1Such observers are said to be in inertial systems.;
- the speed of light in a vacuum is a constant, the same for all observers.
The first statement, the principle of relativity, means that if someone goes by you in a high-speed train on a straight track, then either you or she can consider herself to be stationary and the other moving. If you have traveled by train, you may have wondered sometimes whether your train was advancing or the one next to you was moving backwards.
The second statement means that if both you and your friend in the train measure the speed of a light beam, you both will find the same answer, about 300,000 km/sec. This is not intuitive.
From these two statements, lots of things follow, including.
the equivalence of mass and energy, expressed by everybody’s favorite (and perhaps only) equation, E=mc2;
the fact that only bodies without mass can travel at the speed of light;
curious distortions like the faster someone is moving relative to us,
the heavier she gets,
the shorter she gets in the direction of motion and
the slower her clock runs, including her body clock, the heart.
This last point is the origin of the famous twin “paradox”. If your twin takes off in a space ship and travels fairly fast compared to the speed of light, then when she gets back to Earth, she will be younger than you, the twin she left behind. Strange, but this has been tested (with particles) and found to be true.
All this comes out of the mathematics for describing relative motion, which is in turn due to the fact that space and time are not independent, but form a four-dimensional “thing” called space-time. What we see as space and time are aspects of space-time and can appear differently for different observers. And they can get mixed up together, especially if you are traveling at high speeds.
The other Relativity theory is called General Relativity (GR). Whereas Special Relativity is the theory of space-time and light, General Relativity is the theory of gravity. GR says that space-time is curved and that it is more curved where gravitational forces are stronger. In fact, gravity is the curvature of space-time. Think of a plane surface with a depression in it. Put a ball on it and the ball will roll into the depression. Try to visualize that in four dimensions (Good luck!) and you’ve got GR. Uh, sort-of …
There are also lots of things which follow from GR. One of the more interesting is that gravity can change the direction of light, since light travels through the space deformed by gravity. This and many other predictions have been observed to occur just as GR predicts.
Curiously enough, clocks run slower in a stronger gravitational field. A clock runs faster on top of a high building or in a satellite than it does on the surface of the Earth. For a satellite, this is opposite to the effect of high speeds on fast-moving clocks in SR, which makes them run slower. The two corrections are in opposite directions but do not cancel each other completely, so both must be applied to GPS systems in order for them to function correctly.
More recently, we have discovered that not only is space-time curved, but that space is expanding. This is because a gravitational field exerts not just a force, but a pressure. This pressure is considered to come from a term in the equations of GR called the Cosmological Constant. Unlike the force of gravity, which is always attractive, the pressure can be negative, in which case it is not attractive, but repulsive. It is the outward force of the negative pressure which drives the expansion of space. For the last 7 Gy2Gy means giga-years, or 109 years or 10 billion years., the expansion of space has been accelerating. More about that in the cosmology chapter.
QM and GR — an unhappy marriage
As far as they go, SR and GR are as true to nature as can be detected within their separate domains, and so constitute bodies of knowledge – theories. They must be taken into account practically for the technology of GPS systems.
The problem is that QM does not work on the scale of GR, nor the other way around. This is probably the biggest problem in contemporary physics, the resolution of which is the grail now pursued by theorists.
We live in a world where matter sometimes behaves like a particle and sometimes like a wave and where only probabilities can be calculated. All this is taking place in a curved four-dimensional space-time which is expanding at an accelerating rate! And this space is not an empty vacuum, it is something.
Now onto the the standard model of elementary particles.
Notes [ + ]
|1.||↑||Such observers are said to be in inertial systems.|
|2.||↑||Gy means giga-years, or 109 years or 10 billion years.| | 0.814831 | 3.864654 |
Comet ATLAS (formally known as C/2019 Y4) has disintegrated before our very eyes, and two new images from the Hubble Space Telescope show the comet has crumbled into 25 pieces.
After the comet was discovered on Dec. 29, 2019 by the ATLAS (Asteroid Terrestrial-impact Last Alert System) robotic survey system, it started to quickly brighten. However, in mid-March the comet started to abruptly dim and, as ATLAS later confirmed, its icy core started to break apart and disintegrate 91 million miles (146 million kilometers) from Earth.
Incredibly, Hubble was able to capture this comet's demise. On April 20, Hubble observed 30 fragments from the comet and, just a few days later on April 23, it spotted only 25 pieces.
"Their appearance changes substantially between the two days, so much so that it's quite difficult to connect the dots," David Jewitt, professor of planetary science and astronomy at the University of California, Los Angeles (UCLA) and leader of one of two teams that photographed Comet Atlas with Hubble, said in a NASA statement. "I don't know whether this is because the individual pieces are flashing on and off as they reflect sunlight, acting like twinkling lights on a Christmas tree, or because different fragments appear on different days."
"This is really exciting — both because such events are super cool to watch and because they do not happen very often," Quanzhi Ye, of the University of Maryland and the leader of a second Hubble observing team, said in the same statement. "Most comets that fragment are too dim to see. Events at such scale only happen once or twice a decade," she added.
But these observations have, in addition to showing the breakup of a comet in incredible detail, also helped scientists to better understand comets and how and why they break apart. In studying these observations, researchers have found that comets may break apart in this way more commonly than previously thought, according to the statement.
As the comet was brightening earlier this year, people were excited because, if it continued to glow brighter, it could have been visible to the naked eye during its closest approach to Earth on May 23, during which the comet is expected to fly within 72 million miles (116 million kilometers) of our planet. If any pieces of it remain, they should still make this close approach.
Earlier this month, on April 24, Hubble celebrated 30 years of being in space. The space telescope has made over 1.4 million observations in those 30 years, spotting and imaging over 47,000 objects in the cosmos. It has led to a multitude of incredible discoveries, including the discovery of dark energy, and its images have opened humankind's eyes to just how beautiful our universe really is.
- How the Hubble Space Telescope works (infographic)
- Hubble telescope snaps best-ever views of a comet's disintegration
- Interstellar comet Borisov shines in incredible new Hubble photos | 0.877355 | 3.711486 |
This shot of Spektr was taken after the collision with the Progress spacecraft. Note damage to solar arrays.
|Launch||May 20, 1995|
LC-81/23, Baikonur Cosmodrome, LC 81L, USSR
|Docked||June 1, 1995|
|Depressurized||June 25, 1997|
|Re-entry||March 23, 2001|
|Time in Orbit||2134 days, 2 hours |
|Diameter||4.35 m |
|Mass||43,290 lb (19,640 kg)|
- For the experimental black metal/black ambient band, see Spektr (band).
Spektr (Russian: Спектр; English: Spectrum) (TKM-O, 77KSO, 11F77O) was the fifth module of the Mir Space Station. The module was designed for remote observation of Earth's environment containing atmospheric and surface research equipment. Spektr also had four solar arrays which generated about half of the station's electrical power.
The Spektr module was originally developed as part of a top-secret military program code-named "Oktant". It was planned to carry experiments with space-borne surveillance and test antimissile defense. The surveillance instruments were mounted on the exterior of the module opposite the docking port. Also in this location were two launchers for artificial targets. The heart of the Spektr payload was an experimental optical telescope code-named "Pion” (Peony).
- 286K binocular radiometer
- Astra 2 – monitored atmospheric trace constituents, Mir environment
- Balkan 1 lidar – measures upper cloud altitude. Used a 5320-angstrom laser source, provided 4.5 m resolution
- EFO 2 photometer
- KOMZA – interstellar gas detector
- MIRAS absorption spectrometer – had to measure neutral atmospheric composition, but couldn't work due to a failure
- Phaza spectrometer – surface studies. Examined wavelengths between 0.340 and 285 micrometers, and provides 200 km resolution
- Taurus/Grif – monitored Mir's induced X/gamma-ray background
- VRIZ UV spectroradiometer
These experiments would have been a continuation of the research a top-secret TKS-M module, which docked to Salyut 7 in 1985. However, with the end of the Cold War and the shrinking of Russia's space budget, the module was stuck on the ground.
In the mid-1990s with the return of US-Russian cooperation in space, NASA agreed to provide funds to complete the Spektr and Priroda modules in exchange for having 600 to 700 kg of US experiments installed. The Oktava military component was replaced with a conical mounting area for two additional solar arrays. The airlock for the Oktava targets to be used instead to expose experiments to the vacuum of space.
Once in orbit, Spektr served as the living quarters for American astronauts until the collision in late June 1997.
On June 25, 1997, the Progress M-34 spacecraft crashed into Spektr while doing an experimental docking maneuver with the Kvant-1 module. The collision damaged one of Spektr's solar arrays and punctured the hull, causing a relatively slow leak. The crew had enough time to install a hatch cover and seal the module off to prevent depressurization of the entire Mir station. To seal the module, the crew had to remove the cables that were routed through the (open) hatchway, including the power cables from Spektr's solar panels.
An internal spacewalk in the Spektr module in August 1997 by cosmonauts Anatoly Solovyov and Pavel Vinogradov, from Soyuz TM-26, succeeded in restoring these power connections by installing a modified hatch cover to allow the power cables to pass through the hatch when it was in the closed position. In a second internal spacewalk in October they connected two of the panels to a computer system to allow the panels to be controlled remotely and align with the Sun. These modifications allowed power generation to return to approximately 70% of the pre-collision generation capability.
Spektr was left depressurized and isolated from the remainder of the Mir complex.
- Anikeev, Alexander. "Module "Spektr" of orbital station "Mir"". Manned Astronautics. Archived from the original on 2007-02-25. Retrieved 2007-04-16.
- Zak, Anatoly. "Spacecraft: Manned: Mir: Spektr". RussianSpaceweb.com. Retrieved 2007-04-16.
- Wade, Mark. "Spektr". Encyclopedia Astronautica. Archived from the original on 2007-04-07. Retrieved 2007-04-16.
- Россия. Полет орбитального комплекса "Мир" (in Russian). Novosti Kosmonavtiki. 1997. Archived from the original on 17 October 2010.
- Michael Foale (2016-06-22). "Mir Spacecraft: Worst collision in the history of space flight". Witness. BBC News.
- "Take a Tour of Mir: Spektr". WGBH Educational Foundation. November 2000. Archived from the original on 2007-04-07. Retrieved 2007-04-16.
|Wikimedia Commons has media related to Spektr.| | 0.863255 | 3.032915 |
World History Timeline
The importance of these findings will not be apparent without
an overview of accepted world history to date, for simply pushing back the date
of the first known civilisation by a few thousand years or so is meaningless in
It is now assumed that the universe itself burst into existence some 15
billion years ago. For the first few hundred thousand years matter and
radiation intermingled to form a thick fog. Then, around 300,000 years after
the ‘Big Bang’ temperatures fell and electrons began to bind into hydrogen
and helium nuclei to form the first stable atoms.
Soon the universe began to fill with gas clouds and these eventually formed
galaxies. Four billion years after the Big Bang, these galaxies spawned the
first stars and as these stars aged and collapsed, new generations of stars
were born from newly created elements.
After a further 10 billion years, a small star ignited on the
third spiral arm of our unremarkable galaxy. This star gave light and heat to
dust and rubble caught in its gravitational pull, and from this debris four
rocks formed in gravitational eddies, each attracting other space ‘leftovers’ as
their own gravitational pull developed. The star also led to the formation of
larger ‘gas’ planets further out in its ‘solar’ system.
The first of these rocks, Mercury, became a barren planet, similar to the size
of the Earth’s Moon. It was first photographed in
detail in March 1974 (above, left) by the Mariner 10
spacecraft and, although having craters mountains and ridges,
it’s massive temperature fluctuations, (which can be as high as 425° C on the
equator at noon, and plummeting to -180° C just before sunrise) make for the
existence of life there ‘as we know it’ being more than improbable.
The second rock
from the Sun is Venus. This planet is
the closest to Earth and the brightest object in the sky, apart from the Sun and
Moon. This light is due to its covering of dense clouds that reflect over
three-quarters of the sunlight received by the planet. These clouds actually conceal a deadly atmosphere, for although
the main atmospheric gas is carbon dioxide, traces of other substances have been
detected, including hydrogen sulphide, carbon monoxide, sulphur dioxide
and hydrochloric acid. The surface (above
right was photographed for the first time in
October 1975 by the then Soviet Spacecraft Venera 9). This showed the planet’s
surface to be rocky with stones scattered across it with what appears to be soil
in between. Conditions on Venus also suggest that it could not support life as
we know it.Then there is the third rock from the Sun. A planet different
from all others in the Solar System; for it is teeming with life, vegetation,
water, and incredible scenery (– at least to human eyes.) The blue planet is almost 8000 miles in diameter, and moves
around the sun in harness with its Moon at a distance of approximately 93
Images from space show the familiar face of the planet, however
the continents have not always occupied their current positions. Up to 225
million years ago, most of the land on the planet was combined into one
‘super-continent’ named ‘Pangaea’ by geologists. This composite land-mass made for the easy and rapid spreading
of life forms and vegetation. See opposite for how Pangaea broke up into our
current continental structure.
The planet’s historical periods have been broken down by geologists
into the pre-Cambrian period (4600-590 millions of years ago) when there were
few fossils. The Paleozoic (590-225 millions), by the end of which reptiles were
dominant. This period also saw a major extinction when many species of plants
and animals died out.
The Mesozoic period (225-65 millions) ended with the Earth
probably being struck by a huge asteroid that wiped out the dinosaurs and allowed
mammals to dominate through the subsequent Cenozoic period which ended two
million years ago with modern type animals scattered across the planet surface. Throughout its history, the planet has also seen many
ice-ages, with the Mendenhall Glacier in Alaska (right) formerly reaching well
into the United States and as far south as present day London, England during
the last of these periods.
Until the 18th
Century however, few were curious about the planet’s history, nor did many
question the tradition that all life on it had been created in 4004 BCE; a date
calculated by Archbishop Ussher, who merely added up the ages of figures in the
Christian Bible back to Adam and Eve. | 0.902805 | 3.468212 |
While hunting for comets in the skies above 18th century France, astronomer Charles Messier
diligently kept a list of the things he encountered that were definitely not comets. This is number 27 on his now famous not-a-comet list
. In fact, 21st century astronomers would identify it as a planetary nebula
, but it's not a planet either, even though it may appear round
and planet-like in a small telescope. Messier 27 (M27) is an excellent example of a gaseous emission nebula
created as a sun-like star runs out
of nuclear fuel in its core. The nebula forms as the star's outer layers are expelled into space, with a visible glow generated by atoms excited by the dying star's intense but invisible ultraviolet light
. Known by the popular name of the Dumbbell Nebula
, the beautifully symmetric interstellar gas cloud is over 2.5 light-years across and about 1,200 light-years away in the constellation Vulpecula
. This impressive color composite highlights details within the well-studied central region and fainter, seldom imaged features in the nebula's outer halo
. It incorporates broad and narrowband images recorded using
filters sensitive to emission from sulfur, hydrogen and oxygen atoms.
The center of the Lagoon Nebula is a whirlwind of spectacular star formation. Visible near the image center, at least two long funnel-shaped clouds, each roughly half a light-year long, have been formed by extreme stellar winds and intense energetic starlight. The tremendously bright nearby star, Herschel 36, lights the area. Walls of dust hide and redden other hot young stars. As energy from these stars pours into the cool dust and gas, large temperature differences in adjoining regions can be created generating shearing winds which may cause the funnels. This picture, spanning about 5 light years, combines images taken by the orbiting Hubble Space Telescope. The Lagoon Nebula, also known as M8, lies about 5,000 light years distant toward the constellation of Sagittarius.
An unusual type of solar eclipse occurred last year. Usually it is the Earth's Moon that eclipses the Sun. Last June, most unusually, the planet Venus took a turn. Like a solar eclipse by the Moon, the phase of Venus became a continually thinner crescent as Venus became increasingly better aligned with the Sun. Eventually the alignment became perfect and the phase of Venus dropped to zero. The dark spot of Venus crossed our parent star. The situation could technically be labeled a Venusian annular eclipse with an extraordinarily large ring of fire. Pictured above during the occultation, the Sun was imaged in three colors of ultraviolet light by the Earth-orbiting Solar Dynamics Observatory, with the dark region toward the right corresponding to a coronal hole. Hours later, as Venus continued in its orbit, a slight crescent phase appeared again. The next Venusian solar eclipse will occur in 2117.
Is that a cloud hovering over the Sun? Yes, but it is quite different than a cloud hovering over the Earth. The long light feature on the left of the above color-inverted image is actually a solar filament and is composed of mostly charged hydrogen gas held aloft by the Sun's looping magnetic field. By contrast, clouds over the Earth are usually much cooler, composed mostly of tiny water droplets, and are held aloft by upward air motions because they are weigh so little. The above filament was captured on the Sun about two weeks ago near the active solar region AR 1535 visible on the right with dark sunspots. Filaments typically last for a few days to a week, but a long filament like this might hover over the Sun's surface for a month or more. Some filaments trigger large Hyder flares if they suddenly collapse back onto the Sun.
Get out your red/blue glasses and float next to 4 Vesta. A 500 kilometer diameter world, Vesta lies in the main asteroid belt between the orbits of Mars and Jupiter. This stereo anaglyph was constructed from two separate images recorded on July 24 by the just arrived Dawn spacecraft's framing camera with a resolution of about 500 meters per pixel. The 3D view features Vesta's newly discovered terrain, including long equatorial ridges and troughs and the prominent string of three craters at the upper right dubbed Snowman. Highlighted in 3D, steep sides of many of the craters show streaks of both bright and dark material. Of course, the ion-driven Dawn spacecraft is not marooned off Vesta. After a year exploring the asteroid from orbit, Dawn is scheduled to depart, beginning its journey to Ceres.
Barred spiral galaxy NGC 1365 is truly a majestic island universe some 200,000 light-years across. Located a mere 60 million light-years away toward the chemical constellation Fornax, NGC 1365 is a dominant member of the well-studied Fornax galaxy cluster. This impressively sharp color image shows intense star forming regions at the ends of the bar and along the spiral arms, and details of dust lanes cutting across the galaxy's bright core. At the core lies a supermassive black hole. Astronomers think NGC 1365's prominent bar plays a crucial role in the galaxy's evolution, drawing gas and dust into a star-forming maelstrom and ultimately feeding material into the central black hole.
During July 22nd's solar eclipse, the Moon's dark shadow traced a narrow path as it raced eastward across India and China and on into the Pacific. Hong Kong was south of the shadow's path, so a total eclipse was not visible there, but a partial eclipse was still enjoyed by inhabitants of the populous city. And while many were (safely!) watching the sky, images of the partially eclipsed Sun adorned the city itself. In this downlooking photo, taken at 9:40am local time, a remarkable array of solar eclipse views was created by reflection in a grid of eastward facing skyscraper windows. The photographer's location was the 27th floor of Two Pacific Place.
The dark, inner shadow of planet Earth is called the umbra. Shaped like a cone extending into space, the umbra has a circular cross section that can be most easily seen during a lunar eclipse. For example, last Saturday the Full Moon slid across the northern edge of the umbra. Entertaining moon watchers throughout Earth's eastern hemisphere, the lunar passage created a deep but partial lunar eclipse. This composite image uses successive pictures recorded during the eclipse from Athens, Greece to trace out a large part of the umbra's curved edge. The result nicely illustrates the relative size of the umbra's cross section at the distance of the Moon, as well as the Moon's path through the Earth's shadow.
Huge clusters of galaxies are surely colliding in Abell 520 but astrophysicists aren't sure why the dark matter is becoming separated from the normal matter. The dark matter in the above multi-wavelength image is shown in false blue, determined by carefully detailing how the cluster distorts light emitted by more distant galaxies. Very hot gas, a form of normal matter, is shown in false red, determined by the X-rays detected by the Earth-orbiting Chandra X-ray Observatory. Individual galaxies dominated by normal matter appear yellowish or white. Conventional wisdom holds that dark matter and normal matter are attracted the same gravitationally, and so should be distributed the same in Abell 520. Inspection of the above image, however, shows a surprising a lack of a concentration of visible galaxies along the dark matter. One hypothetical answer is that the discrepancy is caused by the large galaxies undergoing some sort of conventional gravitational slingshots. A more controversial hypothesis holds that the dark matter is colliding with itself in some non-gravitational way that has never been seen before. Further simulations and study of this cluster may resolve this scientific conundrum.
Vesta is a huge rock 500 kilometers across that orbits out past Mars. In 1997, the above map of Vesta created using the Hubble Space Telescope was released showing a rugged surface highlighted by a single crater spanning nearly the entire length of the asteroid. The large crater dominates the lower part of the above false-color conglomerate image: blue indicates low terrain, while red indicates raised terrain. Evidence indicates that Vesta underwent a tremendous splintering collision about a billion years ago. In October 1960, a small chunk of this rock believed to have originated on Vesta fell to Earth and was recovered in Australia. Vesta is considered by some to be a candidate for reclassification into a planet.
Like grains of sand on a cosmic beach, individual stars of large spiral galaxy NGC 300 are resolved in this sharp image from the Hubble Space Telescope's Advanced Camera for Surveys (ACS). The inner region of the galaxy is pictured, spanning about 7,500 light-years. At its center is the bright, densely packed galactic core surrounded by a loose array of dark dust lanes mixed with the stars in the galactic plane. NGC 300 lies 6.5 million light-years away and is part of a group of galaxies named for the southern constellation Sculptor. Hubble's unique ability to distinguish so many stars in NGC 300 can be used to hone techniques for making distance measurements on extragalactic scales.
Comet dust rained down on planet Earth last week, streaking through dark skies in the annual Perseid meteor shower. So, while enjoying the anticipated space weather, astronomer Fred Bruenjes recorded a series of many 30 second long exposures spanning about six hours on the night of August 11/12 using a wide angle lens. Combining those frames which captured meteor flashes, he produced this dramatic view of the Perseids of summer. Although the comet dust particles are traveling parallel to each other, the resulting shower meteors clearly seem to radiate from a single point on the sky in the eponymous constellation Perseus. The radiant effect is due to perspective, as the parallel tracks appear to converge at a distance. Bruenjes notes that there are 51 Perseid meteors in the composite image, including one seen nearly head-on.
Several unusual strands of darkness are prominent toward the constellation of Aquila. This particular dark nebula is known as the E Nebula, for its evocative shape, or B142 and B143, for its position(s) on a list of such nebula compiled by Barnard. The E Nebula spans roughly the angle of a full Moon and lies about 2000 light years distant. The nebula can be seen with binoculars and is particularly visible during the summer months in Earth's northern hemisphere. Other names for dark nebula include absorption nebula, as they efficiently absorb visible light emitted behind them, and molecular clouds, as they frequently attain temperatures low enough so that several different types of stable molecules can exist. The low temperatures of these interstellar clouds facilitate the formation of dense knots of gas that may then collapse into bright stars.
Where is most of the normal matter in the Universe? Recent observations from the Chandra X-ray Observatory confirm that it is in hot gas filaments strewn throughout the universe. "Normal matter" refers to known elements and familiar fundamental particles. Previously, the amount of normal matter predicted by the physics of the early universe exceeded the normal matter in galaxies and clusters of galaxies, and so was observationally unaccounted for. The Chandra observations found evidence for the massive and hot intergalactic medium filaments by noting a slight dimming in distant quasar X-rays likely caused by hot gas absorption. The above image derives from a computer simulation showing an expected typical distribution of hot gas in a huge slice of the universe 2.7 billion light-years across and 0.3 billion light years thick. The distribution of much more abundant dark matter likely mimics the normal matter, although the composition of the dark matter remains mysterious. Both the distribution and the nature of the even more abundant dark energy also remain unknown.
The bright Lagoon Nebula is home to a diverse array of astronomical objects. Particularly interesting sources include a bright open cluster of stars and several energetic star-forming regions. When viewed by eye, cluster light is dominated by an overall red glow that is caused by luminous hydrogen gas, while the dark filaments are caused by absorption by dense lanes of dust. The above picture, from the Curtis-Schmidt Telescope, however, shows the nebula's emission in three exact colors specifically emitted by hydrogen, oxygen, and sulfur. The Lagoon Nebula, also known as M8 and NGC 6523, lies about 5000 light-years away. The Lagoon Nebula can be located with binoculars in the constellation of Sagittarius spanning a region over three times the diameter of a full Moon.
If sailing the hydrocarbon seas of Titan, beware of gasoline rain. Such might be a travel advisory issued one future day for adventurers visiting Titan, the largest moon of Saturn. New images of Titan's surface were released last week from the Canada-France Hawaii Telescope featuring the finest details yet resolved. Peering into Titan's thick smog atmosphere with infrared light, complex features interpreted as oceans, glaciers, and rock became visible. The high-resolution infrared image pictured above was made possible using an unblurring technique called adaptive optics. The interplanetary probe Cassini will reach Saturn and Titan in 2004 to better explore this unusual world.
This dramatic set of prominences looms beyond the edge of the sun. The image was captured by astrophotographer Bob Yen as he stood in the moon's shadow near Bagdere, Turkey on August 11 for the millennium's last total solar eclipse. Solar prominences consist of comparatively cool, dense ionized gas lofted above the sun's visible surface by intense magnetic fields. Prominences at the sun's edge or limb are easily seen during total solar eclipses when the moon precisely blocks the bright light from the sun's disk. While many other prominences were reported during the August 11 eclipse, this particular image focuses on ones along the sun's southeastern limb.
This complex composite image of an ominous and spectacular event - an expanding storm of energetic particles from the Sun - was constructed using data recorded by the SOHO spacecraft on November 6, 1997. Four images from two SOHO (Solar Orbiting Heliospheric Observatory) instruments have been nested to show the ultraviolet Sun at center and a large eruption of material from the right-hand solar limb. Known as a Coronal Mass Ejection or CME, the expanding cloud has become relatively cool and dark in the middle with bright edges still connected to the solar surface. High energy protons have peppered the SOHO detectors causing the crazed streaks and blemishes. The picture covers a region extending about 13.5 million miles from the Sun (32 Solar Radii).
On June 25, after successfully completing its planned mission, contact with SOHO was lost -- but has recently been re-established! Hopefully SOHO will soon be able to continue operating in an extended mission phase.
Has Orion the Hunter acquired a new weapon? If you turn your head sideways (counterclockwise) you might notice the familiar constellation of Orion, particularly the three consecutive bright stars that make up Orion's belt. But in addition to the stars that compose his sword, Orion appears to have added some sort of futuristic light-saber, possibly in an attempt to finally track down Taurus the Bull. Actually, the bright streak is a meteor from the Perseid Meteor Shower, a shower that put on an impressive display last Tuesday morning, when this photograph was taken. This meteor was likely a small icy pebble shed years ago from Comet Swift-Tuttle that evaporated as it entered Earth's atmosphere.
Ribbons of red-glowing gas and dark dust surround massive young stars in this close-up of the Lagoon Nebula taken by the Hubble Space Telescope. The Lagoon Nebula is relatively close and bright - it appears larger than the Full Moon and is visible even without a telescope. Light takes about 5000 years to reach here from there. The Lagoon Nebula houses the open star cluster M8. This photograph is combination of exposures taken in the red, green and ultraviolet. The unusual bright central part of the Lagoon Nebula (lower left in this image) is known as the Hourglass Nebula.
The pictured fuzzy patch may become one of the most spectacular comets this century. Although it is very hard to predict how bright a comet will become, Comet Hale-Bopp, named for its discoverers, was spotted farther from the Sun than any previous comet - a good sign that it could become very bright, easily visible to the naked eye. This picture was taken on July 25th 1995, only two days after its discovery. A comet bright enough to see without a telescope occurs only about once a decade. The large coma and long tail of bright comets are so unusual and impressive that they have been considered omens of change by many cultures. A comet does not streak by in few seconds - but it may change its position and structure noticeably from night to night. | 0.931725 | 3.967483 |
The chances of anything coming from Mars have taken a downward turn with the finding that the surface of the red planet contains a “toxic cocktail” of chemicals that can wipe out living organisms.
Experiments with compounds found in the Martian soil show that they are turned into potent bactericides by the ultraviolet light that bathes the planet, effectively sterilising the upper layers of the dusty landscape.
The discovery has wide-ranging implications for the hunt for alien life on the fourth rock from the sun and suggests that missions will have to dig deep underground to find past or present life if it lurks there. The most hospitable environment may lie two or three metres beneath the surface where the soil and any organisms are shielded from intense radiation. “At those depths, it’s possible Martian life may survive,” said Jennifer Wadsworth, a postgraduate astrobiologist at Edinburgh University.
Wadsworth’s research was driven by the discovery of powerful oxidants known as perchlorates in the Martian soil some years back. Hints of perchlorates first showed up in tests performed by Nasa’s Viking lander missions 40 years ago, but were confirmed recently by the space agency’s Phoenix lander and Mars rover, Curiosity. In 2015, the Mars Reconnaissance Orbiter spotted signs of perchlorates in what appeared to be wet and briny streaks that seeped down Martian gullies and crater walls.
Many scientists suspected that perchlorates would be toxic for microbial Martians, but in theory at least, alien bacteria might find a way to use the chemicals as an energy source. If life could thrive in perchlorate-rich brines, then aliens might be thriving in the damp patches on Mars.
Working with Charles Cockell, an astrobiologist at Edinburgh, Wadsworth looked at what happened to Bacillus subtilis, a common soil bacterium and regular Earthly contaminant found on space probes, when it was mixed with magnesium perchlorate and blasted with ultraviolet rays similar to those witnessed on Mars. She found that the bugs were wiped out twice as fast when perchlorate was present. Other perchlorates found on Mars had a similar bactericidal effect.
Further tests found that the UV rays broke down the perchlorate into other chemicals, namely hypochlorite and chlorite, and it is these that appear to be so destructive to the bacteria.
The scientists followed-up with another round of experiments that looked at the toxic effects of iron oxides and hydrogen peroxide, which are also found in Martian soil. These tests yielded even more bad news for microscopic Martians: when the bacteria were hit with UV rays in the presence of perchlorates, iron oxide and peroxide, the bugs were killed 11 times faster than with perchlorates alone. Writing in Scientific Reports, the researchers say that the inhospitable conditions on Mars are caused by a “toxic cocktail of oxidants, iron oxides, perchlorates and UV irradiation.”
The findings mean that damp streaks on the Martian surface that have been spotted from orbit may not be prime spots to find alien microbes. The briny patches would be likely to concentrate perchlorates, making the streaks even more toxic than the surrounding soil.
“I can’t speak for life in the past,” said Wadsworth. “As far as present life, it doesn’t rule it out but probably means we should look for life underground where it’s shielded from the harsh radiation environment on the surface.”
Chris McKay, a planetary scientist at Nasa Ames Research Center in California, said the study was “a big step forward” in understanding the ramifications of finding high levels of perchlorate on Mars. From a Mars exploration point of view, he said the results were both good and bad news. On the plus side, it means that any microbes that hitch a ride on landers sent to Mars will be swiftly destroyed on the surface, alleviating concerns about contaminating a potentially inhabited planet. “This should greatly reduce planetary protection concerns as well as any concerns about infection of astronauts,” he said. “But the bad news is that this means we have to dig to quite some depth to reach a biological record of early life that is not completely destroyed by the reactive UV-activated perchlorates.”
In 2020, the European Space Agency plans to send its ExoMars rover to the red planet on a mission to search for alien life. The rover is equipped with a drill that can bore two metres into the ground to retrieve soil samples in which microscopic Martians may be found.
Andrew Coates, a planetary scientist at UCL who leads the ExoMars panoramic camera team, said the work shows that the surface of Mars today is more hostile to life than thought. “This, combined with the solar and galactic particle radiation environment at the Martian surface, makes it all the more important to sample underneath the surface in the search for biomarkers,” he said.
“With the ExoMars rover, we will drill to retrieve and analyse samples from up to 2m under the surface,” he added. “This is important as a millimetre or two will get us below the harmful ultraviolet, one metre will get us below the oxidants such as perchlorates, and 1.5m gets us below the ionising radiation from the sun and galaxy.” | 0.856482 | 3.634661 |
The first image captured by LROC from lunar orbit was acquired on 30 June 2009. When the LROC team first glimpsed that image, some twelve days after LRO’s launch from Cape Canaveral, there was a mix of pride that all of the hard work to build and calibrate LROC was coming to fruition, relief that the cameras were in perfect working order, and anticipation for the adventures to come. Now, on the fifth anniversary of LROC’s first image, we examine it again, with the insights that come with five years of knowledge gained.
As it happens, this first image shows off one of the most interesting lunar science and exploration sites, Shackleton crater. Shackleton is located at the Moon’s South Pole, with a portion of its rim just grazing 90° south latitude. One of LROC’s primary objectives, defined as the mission was being conceived, was to map regions of permanent shadow or permanent illumination. Because the Moon is just barely tilted on its spin axis (1.5 degrees compared to the 28.5 degrees that give us our seasons on Earth), any low point near the pole has the potential to be forever shaded from the Sun and peaks could forever poke above the horizon to catch grazing rays from the Sun.
Why do we care about lighting conditions at the poles? For any future long-duration missions to the lunar surface, it’s easy to see the benefit of finding a spot with near-continuous illumination to provide solar power. With that also comes a reprieve from the cold lunar night, which lasts a full two weeks at lower latitudes. Because LRO has been in orbit for 5 years, we can now map with great precision how much sunlight each portion of the surface sees by examining repeat imaging as the illumination from the Sun changes in the sky. In the image above, a four-km2 region on Shackleton’s rim (near the boulders) is illuminated over 70% of the time. LROC has shown there are no true regions of perpetual sunlight, but within small areas the surface is in sunlight nearly 94% of the year, with the longest periods of darkness lasting just 43 hours.
Over the last five years, an even bigger revolution in our understanding concerns what happens in those areas that never see the Sun – regions of true permanent shadow like the floor of Shackleton crater. Before LRO’s launch, and really since the Apollo days, the canonical thinking was that the Moon was completely dry. There was some evidence in the form of neutron spectrometer and radar data that regions of permanent shadow may harbor water ice, but no definitive answer. Thus many of LRO’s instruments were designed to provide a fuller picture, so to speak, of these shadowed regions. LROC has undertaken long-exposure images to see inside the shadows, Diviner has measured temperatures below -238° C (-397°F) to show a host of ices are stable, LEND has found evidence for abundant hydrogen, Mini-RF has shown that radar properties within shadowed regions are consistent with the presence of water ice, LAMP and LOLA have demonstrated that there are variations in the reflectance of materials within craters at the poles, possibly indicating ice is present at the surface. And other spacecraft, including LCROSS, Chandrayaan-I, Deep Impact, and Cassini, have shown that hydrated materials are not necessarily limited to the poles. But as this wealth of new data has been gathered, synthesizing it into a consistent story to explain how the volatiles were deposited, migrated, and evolved over time has proved more complicated. Seemingly conflicting results (for example, LROC does not see strong reflectance contrasts within permanent shadow, but LOLA and LAMP indicate frosts may be there; LEND sees abundant hydrogen outside of regions of permanent shadow, which is a bit mysterious) have led to more questions and the need for future missions to land in these enigmatic areas. Hopefully, in a second extended mission, LRO will have the time to gather the data to give us insight to find the best landing sites.
This first image from LROC provides just one example of how our view of the Moon has been altered by LRO’s five years in orbit. Long-outstanding questions are being answered, and new questions are being raised as we examine the abundant data from LRO. This vast trove of data and wealth of new knowledge will be LRO’s legacy for decades to come.
Back to Images | 0.813289 | 3.832175 |
Science magazine published a list of the greatest scientific achievements of humanity is slowly ending 2,019 years. It was full of many exciting discoveries, but only one of them was truly groundbreaking.Of course, it could not be anything else, as the first in the history of space exploration of a powerful black hole located in the center of the galaxy M87, which is the largest and brightest object in the constellation Virgo. That’s why the researchers decided to indent a closer look at this fascinating part of the space.The discoveries made by the project Event Horizont Telescope. It is a network spread all over the world approx. 20 radio antennas that are coupled together in such a way that they form one big antenna dish size of the entire Earth. Only in this way can be made effective observation and recording the shadow of the black hole event horizon. Now we know that a supermassive black hole located in the center of the galaxy M87, has a mass of 6.5 billion solar masses and away from us is 55 million light years. As for the shadow (dark area in the middle of the image below), it acquires the 40 billion kilometers, the event horizon is within approx. 2.5 times smaller. Astronomers working on the project Event Horizont Telescope, received over $3 million to continue its work. This is great news, because it will allow them to prepare another astronomical surprise in the next year. Then our eyes to appear razor-sharp images combined into a movie, which we see as one of the powerful black holes devouring the surrounding matter. Researchers ensure that the view will be spectacular and will be made in our memory for a long time. But that’s not all, astronomers from Radboud University and the European Space Agency propose to build a network of radio telescopes, this time on the Earth’s orbit, so that we see these extraordinary objects in such detail, in which up to now was not given to us.In the scientific journal Astronomy & Astrophysics article appeared in which we read that just two or three satellites dedicated exclusively to the observation of black holes. Scientists have even gave the name of your project, namely the Event Horizon Imager (EHI). In space EHI will have a resolution five times higher than the EHT on Earth. Fig. Radboud University.Most interestingly, the researchers have even prepared graphics, thanks to which we can see how they will look and shadow images of the event horizon Sagittarius A *, the powerful black hole, located in the center of our galaxy from the new observation system. Admittedly, that they will deny breathtaking, and astronomers will be an extremely valuable source of information about these objects, as well as the object of research on the issues various theories.The domain of cosmic Event Horizon imager is to be working at a much higher frequency than Earth Event Horizon Telescope. The latter made the images of the black hole lying in Messier 87, a massive galaxy in the Virgo Cluster, at a frequency of 230 GHz. Meanwhile, the ETI will even 690 GHz. This means that the images are full of details that can not be obtained by ground-based systems, and yet these are the key data on issues of research being functioning of these facilities.
Chinese Big Brother every day is growing in strength. Recently presented a camera that can recognize objects from a distance of 45 kilometers, and now a new device perfectly identify every face in a big crowd. 60000000 Big Brother cameras in China is based on artificial intelligence technology in terms of facial recognition passers-by. This is important because the system detects the criminals and notes any illegal activities. Bottleneck all the technology, however, are cameras in the low resolution image. If the paintings is the little details, the artificial intelligence has a problem with a quick and correct identification of the face.This is especially problematic when the service they want to identify individuals at major demonstrations, for example. Organized in the evening or at night. Here, with the help of engineers just came from Fudan University and Changchun Institute of Optics. They have designed from scratch and built a 500-megapixel camera that can identify a human face, even in a crowd numbering tens of thousands of people.This invention has been presented for the first time at the International Industrial Fair in China, which took place a few days ago. The entire system consists of the entire fleet of this type of cameras. The more there are, the more increases the effectiveness of the detection of specific individuals. Engineers revealed that the device is more than 5 times more effective in terms of face detection information from the human eye. The government already plans to implement new technology to the existing city surveillance systems. Thanks detection or tracking wanted persons selected citizens will become as easy as a piece of cake. The authorities plan to expand in the coming years, a network of cameras Big Brother in China to well over 100 million. It is a great number of them, which people are not physically able to embrace. Therefore, the government rely on artificial intelligence.
It all started at the beginning of last year, when the chief designer of the new console, Mark Cerny, informed about the work on the successor to the PS4 – from the time when we all wonder, at what price and with what specification next-gen Sony hits the market.It is true that a large part of the information we learned thanks to numerous leaks, but now lived to the official presentation. At the beginning of the release date, which for most of us it is no surprise, because since Microsoft announced its Xbox X Series for Christmas next year, Sony does not have too much room for maneuver. Therefore, the PlayStation 5 follows in the footsteps competitor and will debut at the same time, the “magic” Holiday 2020, which could mean any time between October and December next year, but certainly sufficiently early so that we could buy yourself this console as a gift holiday season.Unfortunately still not met the price console, but the recent leak suggested approx. US $499 during its debut in the United States, which seems to be relatively low (especially in the face of the early reports suggesting nearly $1,000, which Sony fortunately denied), although the likely amount – it $100 more than the previous version and that we stick to. With the conference we learned at CES this logo for a new device, though, and here, there were no major surprises, because Sony has a habit combined as Microsoft. Had wanted in this way to note that once again puts on what he does best?By the way, we lived to also confirm some information on the specifications of the console, and even mentioned a super-fast SSD, so that we can forget about burdensome loadings. The only question is at what capacity, because disk space is a serious problem for many users PS4, and the price of $ 499 will not allow too much in this regard. Sony has also provided that the PlayStation 5 will support ray tracing in real time, although recent rumors have suggested that ray tracing is for the equipment too much. We can also count on the support for 3D surround sound audio, drive Ultra HD Blu-Ray, which will enable 4K UHD video playback at 60 frames per second, and backward compatibility with games from the PlayStation 4. Previously, Sony and praised the official information on the new version of the DualShock controller, which will see a few improvements. The first is the implementation of haptic technology to replace the worn-out already “shock” and will allow for a wider range of feedback. This system will be able to create the impression of different textures and areas, allowing you to feel the difference, eg. Between the grassy field and mud. The second novelty is the adaptation triggers is connected to L2 and R2, which enable programming of resistance, giving the possibility of gradation developers depending on their activities. Sony also boast the latest sales results, so we know that since the launch has sold over 5 million headset VR 104 million PlayStation 4, which means the second result in the history of gaming consoles, behind the PS2 and 158 million devices. | 0.906354 | 3.462704 |
Our Solar System has remained largely unchanged for billions of years, and it’s likely to remain that way for a long time to come, but that hasn’t stopped astronomers from looking far into the future in an attempt to forecast some major changes happening to our home galaxy, the Milky Way.
A new research effort supports the idea that the Milky Way is headed for a massive collision, and when that happens it could dramatically affect our Solar System and perhaps even Earth itself. The good news is that humanity will probably be gone by then, one way or another.
The study, conducted by scientist with Durham University, focuses on the relationship between the Milky Way and a satellite galaxy known as the Large Magellanic Cloud (LMC for short). The LMC is current moving away from our galaxy at a high speed, and at present it’s around 63,000 light years away. However, that’s about to change, and computer models suggest that the LMC will eventually collide with our galaxy in a chaotic, swirling mess that might even throw our Solar System out into space.
In the paper, the researchers explain that an initial glancing blow between the two galaxies could fling our Solar System out into space and potentially even affect the habitability of Earth itself. After the collision, the supermassive black hole thought to rest in the center of the Milky Way could grow up to ten times its current size.
But what does all this mean for humanity? Well, not much at the moment. The event isn’t expected to take place for another 2.5 billion years or so, and if mankind hasn’t already turned Earth into an uninhabitable wasteland on its own, we’ll surely have had long enough to come up with an exit strategy if one is needed. Hopefully.
Image Source: NASA/ESA | 0.808921 | 3.251394 |
You probably that planets go around the sun in elliptical orbits. But do you know why?
In fact, they’re moving in circles in 4 dimensions. But when these circles are projected down to 3-dimensional space, they become ellipses!
This animation by Greg Egan shows the idea:
The plane here represents 2 of the 3 space dimensions we live in. The vertical direction is the mysterious fourth dimension. The planet goes around in a circle in 4-dimensional space. But down here in 3 dimensions, its ‘shadow’ moves in an ellipse!
What’s this fourth dimension I’m talking about here? It’s a lot like time. But it’s not exactly time. It’s the difference between ordinary time and another sort of time, which flows at a rate inversely proportional to the distance between the planet and the sun.
The movie uses this other sort of time. Relative to this other time, the planet is moving at constant speed around a circle in 4 dimensions. But in ordinary time, its shadow in 3 dimensions moves faster when it’s closer to the sun.
All this sounds crazy, but it’s not some new physics theory. It’s just a different way of thinking about Newtonian physics!
Physicists have known about this viewpoint at least since 1980, thanks to a paper by the mathematical physicist Jürgen Moser. Some parts of the story are much older. A lot of papers have been written about it.
But I only realized how simple it is when I got this paper in my email, from someone I’d never heard of before:
• Jesper Göransson, Symmetries of the Kepler problem, 8 March 2015.
I get a lot of papers by crackpots in my email, but the occasional gem from someone I don’t know makes up for all those.
The best thing about Göransson’s 4-dimensional description of planetary motion is that it gives a clean explanation of an amazing fact. You can take any elliptical orbit, apply a rotation of 4-dimensional space, and get another valid orbit!
Of course we can rotate an elliptical orbit about the sun in the usual 3-dimensional way and get another elliptical orbit. The interesting part is that we can also do 4-dimensional rotations. This can make a round ellipse look skinny: when we tilt a circle into the fourth dimension, its ‘shadow’ in 3-dimensional space becomes thinner!
In fact, you can turn any elliptical orbit into any other elliptical orbit with the same energy by a 4-dimensional rotation of this sort. All elliptical orbits with the same energy are really just circular orbits on the same sphere in 4 dimensions!
Jesper Göransson explains how this works in a terse and elegant way. But I can’t resist summarizing the key results.
The Kepler problem
Suppose we have a particle moving in an inverse square force law. Its equation of motion is
where is its position as a function of time, is its distance from the origin, is its mass, and says how strong the force is. From this we can derive the law of conservation of energy, which says
for some constant that depends on the particle’s orbit, but doesn’t change with time.
Let’s consider an attractive force, so and elliptical orbits, so Let's call the particle a 'planet'. It's a planet moving around the sun, where we treat the sun as so heavy that it remains perfectly fixed at the origin.
I only want to study orbits of a single fixed energy This frees us to choose units of mass, length and time in which
This will reduce the clutter of letters and let us focus on the key ideas. If you prefer an approach that keeps in the units, see Göransson’s paper.
Now the equation of motion is
and conservation of energy says
The big idea, apparently due to Moser, is to switch from our ordinary notion of time to a new notion of time! We’ll call this new time and demand that
This new kind of time ticks more slowly as you get farther from the sun. So, using this new time speeds up the planet’s motion when it’s far from the sun. If that seems backwards, just think about it. For a planet very far from the sun, one day of this new time could equal a week of ordinary time. So, measured using this new time, a planet far from the sun might travel in one day what would normally take a week.
This compensates for the planet’s ordinary tendency to move slower when it’s far from the sun. In fact, with this new kind of time, a planet moves just as fast when it’s farthest from the sun as when it’s closest.
Amazing stuff happens with this new notion of time!
To see this, first rewrite conservation of energy using this new notion of time. I’ve been using a dot for the ordinary time derivative, following Newton. Let’s use a prime for the derivative with respect to So, for example, we have
Using this new kind of time derivative, Göransson shows that conservation of energy can be written as
This is the equation of a sphere in 4-dimensional space!
I’ll prove that conservation of energy can be written this way later. First let’s talk about what it means. To understand it, we should treat the ordinary time coordinate and the space coordinates on an equal footing. The point
moves around in 4-dimensional space as the parameter changes. What we’re seeing is that the velocity of this point, namely
moves around on a sphere in 4-dimensional space! It’s a sphere of radius one centered at the point
With some further calculation we can show some other wonderful facts:
These are the usual equations for a harmonic oscillator, but with an extra derivative!
I’ll prove these wonderful facts later. For now let’s just think about what they mean. We can state both of them in words as follows: the 4-dimensional velocity carries out simple harmonic motion about the point
That’s nice. But since also stays on the unit sphere centered at this point, we can conclude something even better: must move along a great circle on this sphere, at constant speed!
This implies that the spatial components of the 4-dimensional velocity have mean while the component has mean
The first part here makes a lot of sense: our planet doesn’t drift ever farther from the Sun, so its mean velocity must be zero. The second part is a bit subtler, but it also makes sense: the ordinary time moves forward at speed 1 on average with respect to the new time parameter , but its rate of change oscillates in a sinusoidal way.
If we integrate both sides of
for some constant vector This says that the position oscillates harmonically about a point Since doesn’t change with time, it’s a conserved quantity: it’s called the Runge–Lenz vector.
Often people start with the inverse square force law, show that angular momentum and the Runge–Lenz vector are conserved, and use these 6 conserved quantities and Noether’s theorem to show there’s a 6-dimensional group of symmetries. For solutions with negative energy, this turns out to be the group of rotations in 4 dimensions, SO(4). With more work, we can see how the Kepler problem is related to a harmonic oscillator in 4 dimensions. Doing this involves reparametrizing time.
I like Göransson’s approach better in many ways, because it starts by biting the bullet and reparametrizing time. This lets him rather efficiently show that the planet’s elliptical orbit is a projection to 3-dimensional space of a circular orbit in 4d space. The 4d rotational symmetry is then evident!
Göransson actually carries out his argument for an inverse square law in n-dimensional space; it’s no harder. The elliptical orbits in n dimensions are projections of circular orbits in n+1 dimensions. Angular momentum is a bivector in n dimensions; together with the Runge–Lenz vector it forms a bivector in n+1 dimensions. This is the conserved quantity associated to the (n+1) dimensional rotational symmetry of the problem.
He also carries out the analogous argument for positive-energy orbits, which are hyperbolas, and zero-energy orbits, which are parabolas. The hyperbolic case has the Lorentz group symmetry and the zero-energy case has Euclidean group symmetry! This was already known, but it’s nice to see how easily Göransson’s calculations handle all three cases.
Checking all this is a straightforward exercise in vector calculus, but it takes a bit of work, so let me do some here. There will still be details left to fill in, and I urge that you give it a try, because this is the sort of thing that’s more interesting to do than to watch.
There are a lot of equations coming up, so I’ll put boxes around the important ones. The basic ones are the force law, conservation of energy, and the change of variables that gives
We start with conservation of energy:
and then use
With a little algebra this gives
This shows that the ‘4-velocity’
stays on the unit sphere centered at
The next step is to take the equation of motion
and rewrite it using primes ( derivatives) instead of dots ( derivatives). We start with
and differentiate again to get
Now we use our other equation for and get
To go further, it’s good to get a formula for as well. First we compute
and then differentiating again,
Plugging in our formula for , some wonderful cancellations occur and we get
But we can do better! Remember, conservation of energy says
and we know So,
So, we see
Can you get here more elegantly?
Since this instantly gives
Next let’s get a similar formula for We start with
and differentiate both sides to get
Then plug in our formulas for and Some truly miraculous cancellations occur and we get
I could show you how it works—but to really believe it you have to do it yourself. It’s just algebra. Again, I’d like a better way to see why this happens!
Integrating both sides—which is a bit weird, since we got this equation by differentiating both sides of another one—we get
for some fixed vector the Runge–Lenz vector. This says undergoes harmonic motion about It’s quite remarkable that both and its norm undergo harmonic motion! At first I thought this was impossible, but it’s just a very special circumstance.
The quantum version of a planetary orbit is a hydrogen atom. Everything we just did has a quantum version! For more on that, see
• Greg Egan, The ellipse and the atom.
For more of the history of this problem, see:
• John Baez, Mysteries of the gravitational 2-body problem.
This also treats quantum aspects, connections to supersymmetry and Jordan algebras, and more! Someday I’ll update it to include the material in this blog post. | 0.837243 | 3.687993 |
Much to the amazement and delight of scientists, the latest findings about Pluto reveal it possesses hazy blue skies and numerous red colored patches of water ice exposed on the surface of a world also now known as “The Other Red Planet.”
With each passing day, significant discoveries about Pluto continue piling up higher and higher as more and more data gathered and stored from this past summer’s historic flyby by NASA’s New Horizons reaches ground stations back here on Earth.
“Blue skies–Pluto is awesome!” says Alan Stern, New Horizons principal investigator from Southwest Research Institute (SwRI), Boulder, Colorado.
The bluish tint to Pluto’s skies were unexpectedly discovered after researchers examined the first color images of the high altitude atmospheric hazes returned by New Horizons last week that were taken by the probes Ralph/Multispectral Visible Imaging Camera (MVIC).
“Who would have expected a blue sky in the Kuiper Belt?” Stern said in a NASA statement.
During New Horizons flyby on July 14, 2015, it discovered that Pluto is the biggest object in the outer solar system and thus the ‘King of the Kuiper Belt.”
The Kuiper Belt comprises the third and outermost region of worlds in our solar system.
“It’s gorgeous!” exclaims Stern.
Moreover, the source of Pluto’s blue haze is different from Earth’s and more related to Titan, Saturn’s largest moon – currently being explored by NASA’s Cassini mission orbiting Saturn since 2004.
On Earth, the blue sky is caused by light scattering off tiny particles of nitrogen molecules. Whereas on Titan its related to soot-like particles called tholins.
Tholins are generated by a series of very complex sunlight-initiated chemical reactions between nitrogen and methane (CH4) high in the atmosphere. This eventually produces relatively small, soot-like particles of complex hydrocarbons.
“That striking blue tint tells us about the size and composition of the haze particles,” said New Horizons science team researcher Carly Howett, of SwRI, in a statement.
“A blue sky often results from scattering of sunlight by very small particles. On Earth, those particles are very tiny nitrogen molecules. On Pluto they appear to be larger — but still relatively small — soot-like particles we call tholins.”
As the tholins rain down on Pluto, they add to the widespread red surface coloring.
The Ralph instrument was also key in another discovery announced by New Horizons researchers.
Numerous small, exposed regions of water ice on Pluto’s surface were discovered by combining measurements from the Ralph MVIC spectral composition mapper and infrared spectroscopy from the Linear Etalon Imaging Spectral Array (LEISA) instrument.
The strongest signatures of water ice were found in the Virgil Fossa and Viking Terra regions berby the western edge of Pluto’s huge heart-shaped Tombaugh Regio feature – see image below.
Water ice is only found in certain zones of Pluto for reasons yet to be understood. There may also be a relationship to the tholins, that likewise is yet to be gleaned.
“I’m surprised that this water ice is so red,” says Silvia Protopapa, a science team member from the University of Maryland, College Park. “We don’t yet understand the relationship between water ice and the reddish tholin colorants on Pluto’s surface.”
As of today, New Horizons remains healthy and is over 3.1 billion miles (5 billion kilometers) from Earth.
The team hopes to fire up the thrusters later this fall to propel the spacecraft toward a second Kuiper Belt Object (KBO) in 2019 tentativley named PT1, for Potential Target 1. It is much smaller than Pluto and was recently selected based on images taken by NASA’s Hubble Space Telescope.
Stay tuned here for Ken’s continuing Earth and planetary science and human spaceflight news. | 0.898483 | 3.791207 |
Energy loss gives unexpected insights in evolution of quasar
An international team of astrophysicists observed for the first time that the jet of a quasar is less powerful on long radio wavelengths than earlier predicted. This discovery gives new insights in the evolution of quasar jets. They made this observation using the international Low Frequency Array (LOFAR) telescope, which produced high-resolution radio images of quasar 4C+19.44, located over 5 billion light-years from Earth.
Supermassive black holes many millions of times more massive than the sun reside in the central regions of galaxies. They grow even larger by attracting and consuming nearby gas and dust. If they consume material rapidly, the infalling matter shines brightly and the source is known as a quasar. Some of this infalling matter is not digested, but instead is ejected in the form of so-called jets that punch through the surrounding galaxy and into intergalactic space for millions of light years. These jets, shining brightly at radio wavelengths, are composed of particles accelerated up to nearly the speed of light, but exactly how these particles achieve energies not attainable on the Earth is yet to be completely solved.
The discovery on quasar 4C+19.44 gives new insights to the balance between the energy in the field surrounding the quasar and that residing in the quasar jet. This finding indicates the phenomenon arises from an intrinsic property of the source rather than absorption effects. It implies that the energy budget available to accelerate particles and the balance between energy stored in particles and in the magnetic field is less than expected.
"This is an important discovery that will be used for years to come to improve simulations of jets. We observed for the first time a new signature of particle acceleration in the power emitted by quasar jets at long radio wavelengths—an unexpected behaviour that changes our interpretation of their evolution," said Prof. Francesco Massaro from University of Turin. "This was already discovered in other cosmic sources, but it was never before observed in quasars."
The international team of astrophysicists observed the jet of the quasar 4C+19.44 at short radio wavelengths, in visible light, and X-ray wavelengths. The addition of the LOFAR images allowed astrophysicists to make this discovery. LOFAR is the first radio facility operating at long radio wavelengths, which produces sharp images with a resolution similar to that of the Hubble Space Telescope.
"We have been able to perform this experiment thanks to the highest resolution ever achieved at these long radio wavelengths, made possible by LOFAR." Said Dr. Adam Deller, an astrophysicist of the Swinburne University of Technology who contributed to the LOFAR data analysis and imaging of 4C +19.44 while at ASTRON in the Netherlands, heart of the LOFAR collaboration.
Dr. Raymond Oonk, an astronomer at ASTRON and Leiden University and Dr. Javier Moldon, astronomer at the University of Manchester, explained that "We have developed new calibration techniques for LOFAR and this has allowed us to separate compact radio structures in the quasar jet known as radio knots, and measure their emitted light. This result was unexpected, and demands deeper investigations. New insights and clues on particle acceleration will come soon, thanks to the international stations of LOFAR."
The observation performed on the radio jet of 4C+19.44 was designed by Dr. D. E. Harris, supervisor of Prof. Francesco Massaro, while working at the Harvard-Smithsonian Center for Astrophysics several years ago. He performed the observation in collaboration with Dr. Raffaella Morganti and his friends and colleagues at ASTRON. He only got the opportunity to see preliminary results, as he passed away on 6 December 2015. This publication, published in the first March issue of the Astrophysical Journal, is in memory of his career, which spanned much of the history of radio astronomy. | 0.805248 | 4.108714 |
Credit: CC0 Public Domain Space. The final frontier. And on Nov. 2, 2018, NASA’s Voyager 2 spacecraft crossed into the vastness of interstellar space, following Voyager 1, which made the leap six years earlier. Since their launch in 1977, the two probes have traveled more than 11 billion miles across the solar system, lasting much longer than scientists anticipated.
Powered by plutonium and drawing 400 watts of power each to run their electronics and heat, the probes still snap photos and send them back to NASA. After 42 years, though, only six of Voyager 2’s 10 instruments still work, and NASA scientists expect the probe will go dark in 2025, well before it leaves our Solar system.
But what if Voyager 2 needed only a couple of watts of power? Could it survive long enough to continue its explorations far into the future?
These are the types of questions that scientists are asking at the U.S. Department of Energy’s (DOE) Argonne National Laboratory. Here, Angel Yanguas-Gil, principal materials scientist in the Applied Materials division, is leading an interdisciplinary team that is rethinking the design of computer chips to not only perform and adapt better, but to do so using a minuscule amount of power—around one watt.
For inspiration, the team is looking to the brains of insects, such as ants, bees, and fruit flies—which offer a new frontier in a type of artificial intelligence known as neuromorphic computing . What they have found could turn artificial intelligence on its artificial head. This team took steps in physics, computer science and materials science in order to design and test a new computer chip that can perform and adapt well on a minuscule amount of power.
The soft underbelly of artificial intelligence
Artificial intelligence pervades our lives, providing countless benefits such as powering voice-activated digital assistants, guiding self-driving cars, recognizing our faces, and helping us automatically respond to texts and emails. AI, however, has some limitations: it relies on reams of data and ever-faster hardware—to which it must always be connected—demands a great deal of power and has limited flexibility.
How is artificial intelligence inflexible? The answer lies in how a popular form of AI, called a neural network , spots meaningful arrangements in data. Most neural networks, which uncover patterns and relationships in data without explicit programming, are static, designed for a specific task, such as recognizing images. Once a network learns that task, it can’t switch gears and start driving a car.
“The scene changes, the distribution of data is slightly different than before, and what you learned no longer applies,” explained Sandeep Madireddy, a computer scientist in Argonne’s Mathematics and Computer Science (MCS) division, who has joined Yanguas-Gil’s team.
Insects, on the other hand, are versatile and can solve problems in different ways, said Yanguas-Gil.
“In a biological system, the network can learn by itself and offers a much higher degree of flexibility,” he said. “Evolutionary pressure on insects produces very efficient, adaptive computing machines. Bees, for instance, exhibit half the number of distinct cognitive behaviors of dolphins, just in a much smaller volume.”
Accurate under pressure
To prove this point, Yanguas-Gil and Argonne chemists Jeff Elam and Anil Mane designed and simulated a new neuromorphic chip inspired by the tiny brain structure of bees, fruit flies and ants. The team created a network from scratch that contains two pivotal discoveries: Dynamic filters and weights that change the strength of various neural connections, depending on what the system finds important in real time.
Tungsten‐aluminum oxide, an award-winning nanocomposite material created by Elam and Mane, which would allow the chip to operate at power levels far below one watt. (By contrast, graphics processing units [GPUs], based on conventional silicon semiconductor processing, can consume 100 watts or more per chip.)
Testing of the new chip design revealed that it was as accurate as the standard design, but it learned much more quickly and retained its accuracy—even under 60 percent error rates in its internal operation.
“With neural networks, error rates of 20 percent erode the system’s accuracy,” said Yanguas-Gil. “Our system can tolerate much higher error rates and sustain the same accuracy as a perfect system. This makes it a good candidate for machines that spend 30 years in space.”
With these results, the team won the Best Paper Award in August at the 2019 Institute of Electrical and Electronics Engineers (IEEE) Computer Society’s Space Computing Conference.
Building the hive mind
After his team developed the blueprint for the neuromorphic chip, Yanguas-Gil enlisted Madireddy and Prasanna Balaprakash, also a computer scientist in the lab’s MCS division, and tapped Argonne’s powerful computing tools to maximize its performance.
Using the Theta supercomputer at the Argonne Leadership Computing Facility—a DOE Office of Science User Facility—the duo ran the neuromorphic blueprint through a software package they developed called DeepHyper, which performs automated machine learning for neural networks. DeepHyper tests thousands of different insect brain configurations, generating better variations until it identifies the right one for a particular task.
With each set of configurations, DeepHyper learns—evaluating and then generating the next configuration set based on what it has seen. “It works in much the same way humans learn to play a game, “said Balaprakash. “You play, you get a score, and then—based on the feedback and your mistakes—you slowly get better and better.”
In a production scenario, all of this learning will be encoded onto the neuromorphic chip, and the chip itself will be able to adapt, shifting gears to solve each type of task.
How to change the game
These advances are only the beginning. Once Yanguas-Gil and his team uncover the best-performing chip design, they must agree on its best uses. Fortunately, there seems to be endless demand for a chip that combines computer intelligence—right where it’s needed—with low power requirements.
What if, for instance, scientists could place low-power sensors in national forests to act as an alert for wildfires?
Both Yanguas-Gil and Balaprakash also point to urban areas, where the chip might monitor for potential dangerous chemicals. Argonne, in partnership with the University of Chicago and the City of Chicago, has already installed 120 smart sensing devices around the city to measure factors such as air quality, traffic and climate—a National Science Foundation-funded project known as the Array of Things.
These smart devices use Argonne’s Waggle technology platform, which include remotely programmable high performance computing devices so that AI capabilities can be embedded with the sensors. In this way, for instance, image analysis can yield insights into the amount and character of street activities and even human interactions. In a real sense, these devices can use AI techniques to “learn” about their environments in order to detect new or unusual events or patterns.
“Imagine if those sensors could learn in real time and detect poisonous gas?” asked Balaprakash.
In theory, Yanguas-Gil agrees that neuromorphic chips could act as mass spectrometers to learn in real time to recognize different molecule fragments without being explicitly programmed. “That would be a game changer,” he said.
Provided by Argonne National Laboratory | 0.825648 | 3.087675 |
You can see another galaxy with the naked eye: the Andromeda Galaxy, which is 2.2 million light years away.
There's a 30,000 kilometer hexagonal cloud at Saturn’s north pole.
The core of a star reaches 16 million degrees Celsius. A grain of sand this hot would kill someone from 150 kilometers away.
The sun accounts for 99.86% of the mass of our entire solar system.
The 40,000 kilometer wide Great Red Spot on Jupiter is a persistent storm estimated to be between 200 and 300 years old. To put this in perspective, Earth could fit inside the Great Red Spot 3 times over.
The moon is the only other world humans have ever set foot on. Because the moon has no atmosphere or wind, the footprints planted on it's dusty surface in 1969 by the Apollo astronauts are still there today, perfectly preserved.
Mars is home to Olympus Mons, the largest volcano in our solar system. At 21 kilometers high and 60 kilometers wide, Olympus Mons is roughly the same size as Ireland.
Only three people have ever died outside of the bounds of Earth's atmosphere.
Jupiter is two and a half times bigger than all the other solar system planets combined.
It takes the average photon 170,000 years to travel from the Sun’s core to its surface.
It takes that same photon only 8 minutes to travel from the Sun’s surface to Earth.
In the last 20 years, we’ve discovered more than a thousand planets outside our solar system.
Contrary to popular belief, the Earth has more than one moon. Cruithne (“the Earth’s second moon”) is one of six "quasi-satellite" asteroids that rotate in a near identical orbit to the Earth.
Mercury, Venus, Mars, Jupiter, Saturn, Uranus, and Neptune could all fit in the space between Earth and the Moon.
More than 1,300 Earths could fit inside of Jupiter, the largest planet in our solar system.
More solar energy reaches Earth’s surface in an hour and a half than we used in all of 2001.
Astronomer Frank Drake proposed the Drake Equation to estimate how many civilizations could exist in our galaxy. The figure is in the millions!
Astronauts left a mirror on the Moon’s surface during the Moon landing. Scientists used this mirror to reflect a laser beam which measured the distance between the Moon and the Earth with amazing accuracy.
Scientists recently discovered a star that had been lost in the glare of a supernova for 21 years.
The Sun is more than 300,000 times bigger than the Earth.
The Sun’s surface temperature is around 5,500 degrees Celsius (9,941 degrees Fahrenheit).
An object the size of Mars crashed into Earth 4.5 billion years ago.
The Moon is very hot during the day but very cold at night: the average surface temperature of the Moon is 107 degrees Celsius during the day and -153 degrees Celsius at night.
The Sun travels around the galaxy--a journey of 100,000 light years--once every 200 million years.
A tablespoon of neutron star would weigh about ten billion tons.
If you fell into a black hole, you would get stretched out like spaghetti.
Venus is the hottest planet in our solar system with an average surface temperature of over 450 degrees Celsius.
The Sun weighs 2,000 trillion trillion tons – about 300,000 times as much as the Earth – even though it is made almost entirely of hydrogen and helium, the lightest gases in the universe.
Winds reaching up to 1,100 kilometers per hour--ten times stronger than the fastest recorded on Earth--swirl around Saturn’s equator. | 0.846592 | 3.202807 |
Skip to 0 minutes and 8 secondsNARRATOR: This course introduces and celebrates the amazing diversity of moons in our Solar System, drawing on the unique teaching and research expertise of the Open University.
Skip to 0 minutes and 19 secondsJOHAN ZARNECKI: Every time I see Titan, I find it incredible to think that something we designed and built is sitting there on the surface. It's there now. It will always be there.
Skip to 0 minutes and 30 secondsNARRATOR: With specially filmed contributions from moon experts from around the world.
Skip to 0 minutes and 35 secondsCHRISTIEN SHUPLA: When you get to the gas giants - the large, bloated planets that go around our Sun - they have immense amounts of gravity, and their wide orbits have enabled them to pick up many moons. Some of them probably formed in orbit around the planets. Others are captured asteroids and comets.
Skip to 0 minutes and 52 secondsMICHELE DOUGHERTY: This is the image that we took when went really close to Enceladus, and you can clearly see this large plume of water vapour coming off from the south pole. There are ice crystals, and there are organic compounds, the basic building blocks of life.
Skip to 1 minute and 6 secondsNARRATOR: Having examined a variety of very different moons, their origin, and their past and present activity, the course goes on to investigate the different ways that scientists study moons from highly sophisticated technology used on space probes to the incredible Apollo missions that sent 12 human beings to explore our own Moon.
Skip to 1 minute and 28 secondsSARAH NOBLE: I always remember coming home one night, I had been working late in the lab dealing with lunar samples, and I looked down and saw that my hands were sparkling in the moon light, and I realized that it was moon dust on my hands. And I looked up, and I thought, this dirt came from there.
Skip to 1 minute and 44 secondsNARRATOR: Accessible even if you're new to the subject, the course includes special, interactive elements allowing you to study Moon rocks using a virtual microscope and even to challenge the computer to a game of Moon Trumps. Towards the end of the eight weeks, the course asks some of the big questions about the likelihood of any moons hosting habitable environments as well as exploring the remarkable discovery of water on our own Moon.
Skip to 2 minutes and 14 secondsPAUL SPUDIS: Finding water, it not only enables human life to have a foothold in space, it also permits you to create a space transportation system that's reusable and extensible.
Skip to 2 minutes and 23 secondsNARRATOR: Finishing the course, will leave you with insights into the often dramatic processes that shape the moons of our Solar System and the ingenious ways that scientists can study them. | 0.816927 | 3.223138 |
Spanish scientists discovered an exoplanet of the so-called super-Earth type. It is by 2.1 times larger than the Earth and orbits its host star, a red dwarf, within the habitability zone, also known as the Goldilocks zone. According to the researchers, this exoplanet could have liquid water on its surface, an indispensable condition for alien life to develop.
The finding, made by researchers from the University of Oviedo and the “Instituto de Astrofisica de Canarias,” was made with data from the Kepler Space Telescope, designed to discover exoplanets by using the so-called transit method. In addition to that, the OSIRIS and HARPS-N instruments installed in the Gran Telescopio Canarias (GTC) and the Telescopio Nazionale Galileo (TNG), respectively, located in the “Roque de Los Muchachos Observatory in Las Palma, in the Canary Islands.
Potentially Habitable Super-Earth Exoplanet, Found By Spanish Scientists
The finding will soon be published in the specialized journal Monthly Notices of the Royal Astronomical Society, said Javier de Cos, a professor at the University of Oviedo and co-author of the paper. This super-Earth exoplanet, named K2-286b, orbits around a red dwarf star, the most abundant type in the galaxy. The star, located in the constellation Libra at 244 light years away from us, has a radius of 0.62 solar radii and a temperature of 3,650 degrees Celsius, as the study details.
The super-Earth exoplanet has a radius of 2.1 times larger than the Earth and orbits its star in 27.36 days. The exoplanet might also boast a temperature of about 60 degrees Celsius.
“We have verified that the activity of the star is moderate compared with other stars of similar characteristics which would increase the possibilities of the planet being habitable”, says Javier de Cos.
As the planet is within the Goldilocks zone, it could have the right conditions for alien life as it might possess liquid water, also a prerequisite for the development of life as we know it. | 0.805628 | 3.459326 |
News: Scientists have discovered a new black hole but this time it is the closest known black hole to Earth. This new find is about 1,000 light-years from our solar system.
Is that close? Well, lets see. A light-year is defined as the distance light travels in one Earth year which is about 6 trillion miles (9 trillion km). So technically a black hole that sits 1,000 light-years away may not seem very close but astronomers who work with distance on a larger scale say it is just around the corner.
A black hole is a place in space where gravity pulls so hard that even light cannot get out. The gravity is so strong because matter has been packed into a tiny space. Because no light can get out, people can’t see black holes. They are invisible. Space telescopes with special tools can help find black holes based on their interaction with surrounding objects in space.
How did they find this black hole?
Scientists from the European Southern Observatory using a huge telescope in the Atacama Desert, Chile found this black hole by accident. They were studying two stars in a system called HR 6819. They observed that some object was causing the stars to move in mysterious ways. As per their calculations this object had to be four times heavier than the Sun. Still, they couldn’t see anything.
Thomas Rivinius led the study from Chile and explained, “An invisible object with a mass at least four times that of the Sun can only be a black hole.” The calculations confirmed that there had to be a small black hole by the two stars.
Why is this black hole unique? People in the Southern Hemisphere can for the first time see the two star system with the newly discovered black hole with their naked eye!
The study also explains that this black hole was formed when a star about 10 times as massive as the Sun exploded and caused a giant explosion called a supernova. This probably happened 65 million years ago around the time dinosaurs became extinct. But now this black hole is about 15 miles (24 km) across and its moving around one of the two nearby stars.
Most black holes that have been discovered have some activity around it. Their strong gravitational pull starts to draw in nearby stars leaving a luminous glow and bunch of gas and dust scattered around them. But this black hole appears to be truly black and super quiet so far.
What next? Scientists will keep studying this black hole — and looking for others. They believe there are many, many more black holes like this in our own Milky Way Galaxy. | 0.896522 | 3.673628 |
Want to see a star cluster? Then just look for nighttime’s brightest star, Sirius, in the constellation Canis Major the Greater Dog. A lovely star cluster – called Messier 41 or M41 – lies near Sirius. If you can’t see the star cluster, it’s probably because your sky isn’t dark enough. Try binoculars.
Sirius is easy to spot. It’s bright, brighter than any other star you’ll see in the evening sky now. Just don’t mistake Sirius for the planet Venus, which is even brighter and low in the west after sunset on these January 2020 evenings. What’s more, Sirius is easy to see because the three prominent Belt stars in the constellation Orion the Hunter – three stars in a short, straight row – always point to it.
M41 lies about four degrees almost exactly south of Sirius. The cluster looks fuzzy, not like a pinpoint star. M41 can be seen with the eye alone in a dark sky. It’s likely been spotted by individuals with particularly good vision throughout human history. Sometime before 1654, the early astronomer Giovanni Battista Hodierna noticed M41 and placed it in his catalog of comets of other celestial objects. In the late 1700s, M41 was one of the objects that astronomer Charles Messier (1730-1817) thought could be mistaken for a comet. He was looking for comets, and so compiled a list of these objects to avoid in his now-famous Messier Catalog.
M41 is also sometimes called the Little Beehive, after the other famous Beehive star cluster, also known as M44, in the constellation Cancer.
Both M41 and M44 are what astronomers call open star clusters. They are loose collections of stars, located in the flat disk of our Milky Way galaxy, born from a single cloud of gas and dust in space. These sibling stars still move together through space. They are very beautiful when viewed through binoculars or a small telescope.
Like most open star clusters of its type, M41 is relatively young, probably between 190 and 240 million years old. By contrast, our sun is thought to be 4 1/2 billion years old.
The cluster – whose true diameter in space covers about 25 light-years – contains about 100 stars including several red giants.
At mid-northern latitudes, Sirius and M41 stay out until roughly 3 a.m. local time at this time of year.
So enjoy Orion, the star Sirius and M41 on these January and February evenings. And by the way, there are over 100 of the so-called Messier objects or M-objects known today. Today’s amateur astronomers consider them among the most prized objects to be viewed through binoculars and small telescopes. Here’s a list of M-objects. Advanced amateurs can observe them all and can earn a Messier certificate from the Astronomical League.
Bottom line: No matter where you are on Earth, look for the sky’s brightest star, Sirius, in the month of January. If your sky is dark enough, notice the faint fuzzy object near the bright star Sirius. This object is called M41, and it’s a distant cluster of stars. | 0.837698 | 3.766097 |
At night when you look at the star sky, what do you often think about? Are we really alone in this universe? Ultimately, where is the frontier of the universe?
The truth is that the vast space outside our planet contains many secrets that science cannot yet know. But in contrast, there are also some interesting surprises that after thousands of years of astronomical research, people have used their intelligence to observe, infer and conclude.
What are the most unexpected things you can tell yourself when you look up into the night sky?
1. Why the neutron can spin at 600 rpm
When a star reaches the neutron star stage, it has reached one of the last points of the evolutionary journey. These massive stars were born during supernova explosions, but they collapsed themselves into their cores by a radial gravitational force, which then rotated extremely fast as a physical consequence. of that process.
Normally, neutron stars can spin up to 60 revolutions per second after being born. But in a special case, this speed can be increased to more than 600 rpm.
2. The universe is completely still
In order for sound waves to reach your ears and bounce off your eardrum, it needs an environment to spread. But because there was no air in the vacuum of space, there was always a strange, strange silence.
In contrast, on Earth there is atmosphere and air pressure that allows sound to travel. That explains why there is so much noise on the ground.
3. The number of stars in the universe is an uncountable number
Basically, we don’t know exactly how many stars are in the universe. But scientists can use estimates to answer the question: How many stars are in our galaxy, the Milky Way? They then multiply that number by the best estimate of the number of galaxies in the universe.
After all these calculations, NASA can only confidently say that the number of stars in this universe is immeasurable, so much that it cannot be counted.
A study by the Australian National University estimates that there are 70,000 million million stars in the universe.
4. The footprint that astronauts on the Apollo mission leave on the Moon will probably last for at least 100 million more years.
The moon has no atmosphere, no wind or water to wash away or fade away the marks of Apollo astronauts. That means footprints, rover wheel tracks, traces left by human spacecraft will be stored on the moon for a very long time.
The only thing that can erase these traces is the deposition of cosmic dust being sucked onto the surface of the Moon. Those are the “micrometer meteor “ repeatedly attack the Moon, but the process will take place very very slowly.
5. The Sun makes up 99% of the mass of the Solar System
Our star, the Sun, is so dense that it accounts for 99% of the mass of the entire Solar System. Mass is what allows the Sun to dominate all the planets, sucking them around.
Technically, our Sun is a G-type main-sequence star, meaning that every second, it will merge about 600 million tons of hydrogen with helium. It also converts about 4 million tons of matter into energy as a by-product.
When the Sun dies, it will become a red giant, bulging and devouring the Earth and everything on it. But don’t worry: It won’t be possible within 5 billion years.
6. The total amount of solar energy hitting the Earth every hour is more than the total energy the planet uses throughout the year
In the past century and a half, people are increasingly exploiting more solar energy to serve their lives. According to the 360 degree Yale Environment Magazine, in 2017, the world increased by 30% of solar power capacity, equivalent to 98.9 gigawatts of solar energy has been produced.
Even so, this is only 0.7% of the world’s annual electricity use.
7. If two metal elements of the same element touch each other in space, they will stick together and stick together forever
This amazing effect is called cold welding. It happens because the atoms on either side of two pure (undoped) metal fragments can no longer distinguish where they belong. Therefore, these atoms automatically bind to nearby atoms, which belong to the nearby metal fragment that makes them stick together.
The interesting thing is that cold welding never happens in Earth’s atmosphere, because there are always water and air molecules separating the two metal pieces, no matter how close they are to each other. .
Cold welding occurring in vacuum is an effect that has a lot of significance for the construction and repair of spacecraft and the future of vacuum construction.
8. The largest asteroid in our Solar System is a giant piece of space rock called Ceres
Ceres asteroid – sometimes called a dwarf planet – has a diameter of about 950 km. So far, Ceres is known to be the largest asteroid in the asteroid belt between Mars and Jupiter. It alone accounted for a third of the weight of the belt. The surface area of Ceres is approximately the area of India or Argentina.
There’s a human spaceship approaching and flying around Ceres, helping us discover its mysteries. Dawn, or the Dawn ship, was launched into space in 2007 and it took eight years to reach Ceres.
9. A day on Venus is longer than a year on Earth
Venus has an extremely slow axis rotation speed, taking about 243 days on Earth for it to complete an entire cycle. Ironically, a year on Venus is shorter than the period around its own axis. Venus only takes 226 Earth days to orbit the Sun.
If you lived on Venus, you would see the Sun rise every 117 days on Earth. That means the Sun will only grow twice in Venus’ year. In addition, because Venus rotates clockwise, the Sun will rise in the west and set in the east.
10. The Great Red Spot of Jupiter is shrinking
The giant storm on Jupiter, which can be seen through a telescope from the Earth like a Great Red Spot, is shrinking. At nearly 11 times the diameter of Earth, Jupiter may have storms that devour the three Earths in its heart. The Great Red Spot has been such a storm, but so far, its size has shrunk to just a third.
11. One of Saturn’s moons has two distinct tones
Iapetus, one of 62 moons of Saturn, is actually a rather unique celestial body. This moon has two very specific tones, with one side much darker than the other. This feature does not appear on any other moon in the Solar System.
Iapetus’s color must be related to its position relative to the rest of Saturn’s moons. Iapetus is located outside the Saturn belt and therefore, it is subjected to a lot of space debris that shoots to the surface, causing dark colors on one side of it.
12. The location of the North Star will change
It would be strange for a North Star to no longer be a North Star. But in about 13,000 years, scientists predict this will happen. In case you didn’t know, the Earth axis has undergone a movement called “precession”, meaning that it will gradually tilt to draw a cone, similar to the spinning top when it is about to fall.
When this happens, the stellar position of the North Star will deviate from the Earth, leaving it no longer stationary in the night sky in the northern hemisphere. At that time, we will have a new North Star. | 0.907232 | 3.749791 |
One of our closest galactic neighbors is M33, also known as the Triangulum Galaxy. It is a member of what's known as the Local Group of galaxies.
A new infrared image from NASA's Spitzer Space Telescope reveals the colorful M33 to be surprising large -- bigger than its visible-light appearance would suggest, astronomers said in a recent statement.
With its ability to detect cold, dark dust, Spitzer sees emission from cooler material well beyond the visible range of M33's disk. Exactly how this cold material moved outward from the galaxy is still a mystery, but winds from giant stars or supernovas may be responsible, Spitzer astronomers said.
Along with our own Milky Way, galaxies in the the Local Group are all bound by gravity. This binding can create collisions. The Milky Way has absorbed many smaller galaxies, and eventually we'll have a wrenching head-on with the Andromeda Galaxy, a match for us size-wise and recently found to be much larger than was known.
M33, the third largest galaxy in our group, is also moving toward the Milky Way (which is about 100,000 light-years in diameter). Nothing to worry about, however. This galactic cousin is presently some 2.9 million light-years away in the constellation Triangulum.
A light-year is the distance light travels in one year, about 6 trillion miles (10 trillion kilometers).
While M33 is a spiral galaxy like our own, it is quite different. It has little or no central bulge of stars, and astronomers figure if it has a central black hole, the mass of it is probably no more than 3,000 times that of our sun. Our Milky Way's central black hole, on the other hand, is a few million solar masses.
- Video: When Galaxies Collide
- Gallery of Galactic Collisions
- Milky Way Image Gallery | 0.815829 | 3.565338 |
The Sun is not the live coal that Anaxagoras described. We can imagine hell in its interior, and we know that there are darker spots on its surface which, when discovered, were shown to be incompatible with the Aristotelian principle of the perfection of the heavenly bodies. We have learned a great deal about our star since then, but even now we do not know the answer to some important questions about the source of energy of our Solar System, the main source of life. These were the words of Jeffrey R. Kuhn, doctor in Physics from Princeton University, and currently Professor at the Institute of Astronomy at the University of Hawaii, who gave a talk at the Instituto de Astrofísica de Canarias (IAC) about the observations of the solar corona which will be made with the Daniel K. Inouye Solar Telescope (DKIST) planned for Hawaii. This is the astronomer who is in charge of that telescope, which will be used to measure the magnetic field in the solar corona. As well as obtaining a better understanding of the Sun, Kuhn also thinks, as he said in his colloquium to researchers at the IAC, that we are likely to find life outside the Solar System within a decade, although this will need optical telescopes which can make direct images of expolanets, such as specialized telescopes with diameters in the range 20-100 metres.
1. You were one of the speakers of the IAC Winter School of 1994 dedicated to the structure of the Sun. What have we learned from the Sun since then and what do we have left to learn?
Very interesting question, so 1994, it has been more than 20 years now. Those were the early days of Helioseismology and the big change since then is that Helioseismology is a mature field now and not only is it a complete tool for the sun but it has become a complete tool for understanding other stars. Back then we had no idea that we would be able to use these tools to extend our knowledge of the interiors, not just of the sun, but the interiors of other stars. So I think one of the most exciting developments was that transition. For the sun we now know very well about the interior rotation that we did not know very well before. We have begun, and most people would say we have solved, the problem of why the sun rotates differentially, we understand the interaction of convection and rotation. There are still some mysteries, the mystery of what happens with the rotation of the surface of the sun and why it slows down is a very large mystery and there are now many problems that remain in trying to understand how the magnetic field makes its way out into the corona. So there are still plenty of problems to deal with but I would say that the subject of that one school was very important because it was the early days of the field of Helioseismology which played a very big role in the development of, I think, the IAC and what the IAC does.
2. A recent study by Queen's University and the IAC published in Nature Astronomy gave an explanation of why the solar corona is hotter than the surface? Has one of the enigmas that for decades brought head-to-head physicists been solved?
I think that that they are on the right track but I would say that we still have not completely unraveled that problem. We know that it is magnetic energy that is heating the corona and we know that it is related to the waves, but I think that the verdict is still out on exactly how the magnetic energy gets converted into heat and so, I think, that this is a very important step forward but it is not finished.
3. To what extent will what we know about the Sun depend on instrumentation and large telescopes?
There is a very large jump in our ability to study the Sun coming hopefully from here with the European Solar Telescope but on the other side of the world the Daniel K. Inouye telescope that will come on line in about 6 months and it will be open for business. That telescope is unusual in that it has really been designed to look at the corona, it has the capabilities of being a chronograph blocking the light of the disk of the sun and seeing the very faint corona and one of the first light instruments is an instrument I am responsible for called the Cryogenic Near Infrared Spectrograph and its job is to measure the magnetism, its primary science goal, will be from the beginning to measure the magnetic field of the corona of the sun and understand how it actually does create the transfer, the energy of magnetism into the energy of heat. I think that when the European, and other solar telescopes come online, they will be focused on very detailed questions related to the magnetism of the disk of the Sun. And those are things that we still are struggling with because the difficulty of the magnetic field problem is that the magnetism exists on all spatial scales which are all interconnected, and the interconnection has proved to be difficult. So we need what is going on both over in Hawaii and in this other telescope here.
4. What is expected of the Daniel K. Inouye Solar Telescope that will be in operation soon and how will it be complemented by the European Solar Telescope EST, which will be installed in the Canary Islands?
Because they are 10 or 11 time zones apart, they give us the opportunity of tracing and following the dynamic magnetic structure essentially continuously. The Sun unfortunately continues to work at night when we cannot see it in Hawaii and so the ability, when we do look at the disk of the Sun, to combine what happens here with what we can see over there I think this is going to be a wonderful development.
5. The colloquium you gave here covered the future of exoplanet research with the generation of telescopes that will follow the TMT, EELT and GMT. Will we get direct images of an exoplanet? And proof of life beyond the Solar System?
I think that in our lifetime we are going to wake up some morning up to the news that w have discovered life. And it is my personal view that life is not very rare at all. You know in astronomy and life, we spend our lives thinking that were very special. From the time our mothers and our fathers cradle us in their arms, we think the world is small and that we are the center of it. We spend our lives thinking on we are special and, in this way, it is not very different in astronomy. In astronomy we have learned how unspecial the Earth was. When I was a graduate student I was told by my professors that conditions to form planets were so rare that it is very unlikely that there are other planets in the galaxy or even the universe and of course that´s wrong. Around most stars there is at least one planet and I think we should take that lesson to heart and recognize that life probably also is not very rare and unusual and the only reason why we have not seen it is because we have not had that capability, even the biggest telescopes we are building now, the EELT or the TMT or the GMT, will have a very difficult time finding signatures of life.
We should be building a telescope which is not directed to doing all astronomy but which is directed at forming, basically, images of exoplanets. The telescope can be big enough that it can make a picture directly but the combination of using what we call inversion tools and separating the light of the planet from the star will allow us to make pictures of exoplanets. And I think that is going to happen and the technology for those telescopes is different because it is not a telescope that does everything for everybody, it will not do supernova research, it is not optimal. The TMT or the EELT will cover that, but this is a telescope that would spend all of its time to understand exoplanets, understand life. And it would be different in the way that it works through several different technologies that are just becoming available now. I would say that the technologies are there but they haven´t been demonstrated, so a very important step is to build a precursor, we call it a Hybrid Optical Telescope, it is a telescope that combines elements of a conventional telescope like the Gran Telescopio Canarias (GTC) with elements of interferometry and we have simulated and demonstrated how that could work, but we really need to go to the sky and demonstrate it and I think we could do that within a couple of years if we dedicate the energy and resolve. And that is what we are trying to do.
6. Do you think that the problems in Hawaii will be solved in order to install the TMT there or that this telescope will finally be installed on La Palma?
That is difficult, so I am old enough to know and understand that the hardest problems in doing science are related to people, it is not the technology and it is not even the theory or the calculations or the data analysis are its problems, it is the people. And I would say that none of the astronomers, I do not spend much time on Maunakea but you are right I work with the astronomers that do, none of us anticipated that the people problems would be so difficult with the TMT. I do not know the answer; I think right now the entire situation is a stalemate. So you have this side and the other side staring at one another and they are just waiting for someone to back down. I do not think that the Hawaiian groups that are camped on the mountain are going to back down. And I also do not understand or believe that the governor of the state of Hawaii is going to go away, so I do not know what that means. It could mean that the telescope will be built somewhere else. Then the situation in Hawaii is very complicated and I think none of us, the problem was that none of us in the astronomy world knew how complicated it really was and we kind of discovered that as it took place. I am just grateful that on Haleakala, we have completed this major solar telescope and that we were delayed for 4-5 years when the environment would have been much more difficult to finish it.
7. To what extent is the conflict with the Hawaiian indigenous population affecting other facilities present and future in Hawaii?
My belief is that this will be resolved in time, and regardless of the future of the TMT I think people will, with some time, find common ground and realize that there is respect on both sides. The university of Hawaii is very much an inclusive university of the Hawaiian culture and the local cultures that have been there only over the last 100 years. I think it is a matter of time and everyone is working towards that understanding. So I am optimistic. | 0.85022 | 3.712476 |
Shining 60 million light-years away all serene-looking is NGC 1316 (left) and a smaller galaxy NGC 1317. This new picture from the European Southern Observatory’s La Silla Observatory in Chile, however, reveals “battle scars” of ancient fights, the observatory stated.
“Several clues in the structure of NGC 1316 reveal that its past was turbulent. For instance, it has some unusual dust lanes embedded within a much larger envelope of stars, and a population of unusually small globular star clusters. These suggest that it may have already swallowed a dust-rich spiral galaxy about three billion years ago,” the European Southern Observatory stated.
“Also seen around the galaxy are very faint tidal tails — wisps and shells of stars that have been torn from their original locations and flung into intergalactic space. These features are produced by complex gravitational effects on the orbits of stars when another galaxy comes too close. All of these signs point to a violent past during which NGC 1316 annexed other galaxies and suggest that the disruptive behavior is continuing.”
You might better known NGC 1316 as Fornax A, the brightest radio source in the constellation Fornax and the fourth-brightest source in the sky. This is due to its supermassive black hole sucking up material in the area — and could actually be stronger because of the close encounters with other galaxies.
This image is a composite of archival pictures from the telescope. If you look closely, you can spot some fainter galaxies in the background, too. | 0.813674 | 3.571687 |
In the past two decades, exoplanet hunters have discovered almost 1800 planets beyond the Solar System, and there is more than twice that number of potential candidates still awaiting further confirmation. Of the known alien systems, astronomers have found a substantial number of planets travel around their parent stars in truly unusual orbits, unexplainable by any planetary formation mechanism.
The list of peculiar cases includes bodies that travel along completely different orbital planes to one another, worlds that take millennia to complete an orbit, and those that possess extreme comet-like eccentricities. Even more extreme are the rogue planets out there that orbit no star, presumably having been ejected from their solar systems altogether. However, the most inexplicable bodies are hot Jupiters, which orbit their parent stars in a matter of hours to days at a fraction of the distance that Mercury lies from the Sun. At such close proximity to the star, temperatures would simply be too high for a massive planet to retain its gaseous envelope during formation.
If these bodies cannot have formed at their current locations this may mean that planetary orbits are subject to dramatic change throughout the evolution of a system; meaning that where we observe a body now may not be where it formed, or where it will eventually end up. This reordering is referred to by scientists as planetary migration.
There are three ways in which planetary migration is understood to occur: the first describes a gas driven process in which the planetary disk effectively pushes or pulls the planet to a new position; the second arises as a result of gravitational interactions between neighbouring bodies, where a large object can scatter a smaller one and thereby create an equal and opposite resulting force back onto itself; and the third is due to another gravitational effect, tidal forces, which mainly occur between the star and the planet and tend to result in more circular orbits.
Surprising as it may seem to some, it is widely accepted that planetary migration has shaped and influenced the architecture of the Solar System quite dramatically. In fact, its dynamic past actually explains the existence and properties of several Solar System entities, and shows that our planetary system might not be as unique as once thought. So how have the planets moved since their birth?
It all began with the inward migration of the largest planet in the Solar System, Jupiter. The gas giant, weighing more than all the other planets combined, is believed to have travelled right up to the orbit of Mars, 1.5 AU from the Sun, before travelling back out to its present location almost four times as far. Luckily for Mars this occurred some 600 million years into the birth of the Solar System (around 4 billion years ago) before any of the terrestrial planets had formed and only four gas giants ruled the skies. At this time, Jupiter, Saturn, Uranus and Neptune possessed much more compact orbits and were surrounded by a dense disk of small icy objects.
Jupiter was drawn towards the Sun by the first type of planetary migration, gas driven, whose effects work differently depending on the mass of the planet. For low-mass planets, like the Earth, the mechanism occurs when the planet’s orbit perturbs the surrounding gas or planetesimal disk driving spiral density waves into it. An imbalance can occur between the strength of the interaction with the spirals inside and outside the planet’s orbit, causing the planet to gain or lose angular momentum. If angular momentum is lost the planet migrates inwards, and if it is gained it travels outwards. This is known as Type I migration and occurs on a short timescale relative to the lifetime of the accretion disk.
In the case of high mass planets, like Jupiter, their strong gravitational pull clears a sizeable gap in the disk which ends Type I migration and allows Type II to take over. Here the material enters the gap and in turn moves the planet and gap inwards over the accretion timescale of the disk. This migration mechanism is thought to explain why hot Jupiters are found in such close proximity to their stars in other planetary systems. The third type of gas driven migration is sometimes referred to as runaway migration, where large-scale vortices in the disk rapidly draw the planet in towards the star in a few tens of orbits.
The best understanding of how the planets have moved in throughout our system’s evolution arose from the Nice Model, proposed by an international collaboration of scientists in 2005. This model suggests that at the inner edge of the icy disk, some 35 AU from the Sun, the outermost planet began interacting with icy planetesimals, influencing the second sort of migration to occur: gravitational scattering. Comets were slingshotted from one planet to the next, which gradually caused Uranus, Neptune, Saturn and the belt to migrate outwards. Jupiter’s powerful gravity flung the icy objects that reached it into highly elliptical orbits or out of the Solar System entirely, which in order to conserve angular momentum, further propelled its journey inwards.
An extension to this theory is the ‘Grand Tack model‘, which is named after the unusual course of Jupiter’s migration towards the Sun before stopping and migrating outwards again, like a sailboat tacking about a buoy. At the distance that Mars would later coalesce, material had been swept away due to Jupiter’s presence. This resulted in the stunted growth of Mars and a material-rich region from which the Earth and Venus formed, explaining their respective sizes. The gas giant’s travels also prevented the rocky material in the asteroid belt from accreting into larger bodies due to its strong gravitational influence. Although Jupiter swapped positions with the asteroid belt twice the movements were so slow that collisions were minimal, resulting in more of a gentle displacement.
But why did Jupiter’s migration to the Sun’s fiery depths cease? For that it has Saturn to thank. As the two planets moved further away from each other, it was believed they became temporarily locked in a 2:1 orbital resonance. That meant that for every orbit of the Sun Saturn made, Jupiter made two. The Nice Model showed that the planetary coupling increased their orbital eccentricities and rapidly destabilised the entire system. Jupiter forced Saturn outwards, pushing Neptune and Uranus into extremely elliptical orbits where they gravitationally scattered the dense icy disk far into the inner and outer Solar System. This disruption in turn scattered almost the entire primordial disk. Some models also show Neptune to have been propelled past Uranus to become the farthest planet from the Sun as we now know it. Over time the orbits of the outermost planets settled back into the near circular paths we observe today.
The Nice Model explains the present day absence of a dense trans-Neptunian population and the positions of the Kuiper belt and Oort cloud. It also accounts for the mixture of icy and rocky objects in the asteroid belt, like water-rich dwarf planet, Ceres, which likely originated from the icy belt. The rapid scattering of icy objects, around 4 billion years ago, dates with the onset of the late heavy bombardment period, which is predominantly recorded from the Moon’s well-preserved surface.
However, there are problems with the original Nice Model, where some simulations found that the gradual 2:1 resonant coupling of Jupiter and Saturn would have resulted in an extremely unstable inner Solar System from which Mars would have been ejected. Later research has since resulted in the ‘Nice 2 Model‘, which in part suggests that the gradual scattering of planetesimals caused the two gas giants to fall into a 3:2 orbital resonance (not the originally proposed 2:1), allowing for the Nice Model to work with a stable inner Solar System.
The final mechanism for planetary migration occurs through tidal interactions between different celestial bodies. Unlike gas driven migration and gravitational scattering, tidal forces act over a much longer timescale of billions of years. The process begins due to the Kozai mechanism, which is suggested to pump eccentricity into a planet’s orbit. As the tidal forces correct this effect by re-circularising its orbit the planet moves closer in. Whilst the orbits of the terrestrial planets are thought to have remained fairly stable throughout the evolution of the Solar System, this gradual process is likely to have slightly altered their paths and will remain to do so.
The knowledge of how our own planetary system evolved has helped answer many questions about unusual exoplanet orbits, but there is still a lot left to uncover. One such question asks why we observe so many hot Jupiters unfathomably close to their star, as without another large body’s influence, should it not eventually be swallowed up? Perhaps planet-disk interactions decouple at such close proximities to the star and tidal forces prevail, or perhaps we are capturing a snapshot in time just before the planet meets its fate. For now only time, further observations and, most importantly, more exoplanet discoveries will tell! | 0.925316 | 4.055551 |
Ryugu’s interaction with the sun changes what we know about asteroid history.
In February and July of 2019, the Hayabusa2 spacecraft briefly touched down on the surface of near-Earth asteroid Ryugu. The readings it took with various instruments at those times have given researchers insight into the physical and chemical properties of the 1-kilometer-wide asteroid. These findings could help explain the history of Ryugu and other asteroids, as well as the solar system at large.
When our solar system formed around 5 billion years ago, most of the material it formed from became the sun, and a fraction of a percent became the planets and solid bodies, including asteroids. Planets have changed a lot since the early days of the solar system due to geological processes, chemical changes, bombardments, and more. But asteroids have remained more or less the same as they are too small to experience those things, and are therefore useful for researchers who investigate the early solar system and our origins.
“I believe knowledge of the evolutionary processes of asteroids and planets are essential to understand the origins of the Earth and life itself,” said Associate Professor Tomokatsu Morota from the Department of Earth and Planetary Science at the University of Tokyo. “Asteroid Ryugu presents an amazing opportunity to learn more about this as it is relatively close to home, so Hayabusa2 could make a return journey relatively easily.”
Hayabusa2 launched in December 2014 and reached Ryugu in June 2018. At the time of writing, Hayabusa2 is on its way back to Earth and is scheduled to deliver a payload in December 2020. This payload consists of small samples of surface material from Ryugu collected during two touchdowns in February and July of 2019. Researchers will learn much from the direct study of this material, but even before it reaches us, Hayabusa2 helped researchers to investigate the physical and chemical makeup of Ryugu.
“We used Hayabusa2’s ONC-W1 and ONC-T imaging instruments to look at dusty matter kicked up by the spacecraft’s engines during the touchdowns,” said Morota. “We discovered large amounts of very fine grains of dark-red colored minerals. These were produced by solar heating, suggesting at some point Ryugu must have passed close by the sun.”
Morota and his team investigated the spatial distribution of the dark-red matter around Ryugu as well as its spectra or light signature. The strong presence of the material around specific latitudes corresponded to the areas that would have received the most solar radiation in the asteroid’s past; hence, the belief that Ryugu must have passed by the sun.
“From previous studies we know Ryugu is carbon-rich and contains hydrated minerals and organic molecules. We wanted to know how solar heating chemically changed these molecules,” said Morota. “Our theories about solar heating could change what we know of orbital dynamics of asteroids in the solar system. This in turn alters our knowledge of broader solar system history, including factors that may have affected the early Earth.”
When Hayabusa2 delivers material it collected during both touchdowns, researchers will unlock even more secrets of our solar history. Based on spectral readings and albedo, or reflectivity, from within the touchdown sites, researchers are confident that both dark-red solar-heated material and gray unheated material were collected by Hayabusa2. Morota and his team hope to study larger properties of Ryugu, such as its many craters and boulders.
“I wish to study the statistics of Ryugu’s surface craters to better understand the strength characteristics of its rocks, and history of small impacts it may have received,” said Morota. “The craters and boulders on Ryugu meant there were limited safe landing locations for Hayabusa2. Finding a suitable location was hard work and the eventual first successful touchdown was one of the most exciting events of my life.”
Reference: “Sample collection from asteroid (162173) Ryugu by Hayabusa2: Implications for surface evolution” by T. Morota, S. Sugita, Y. Cho, M. Kanamaru, E. Tatsumi, N. Sakatani, R. Honda, N. Hirata, H. Kikuchi, M. Yamada, Y. Yokota, S. Kameda, M. Matsuoka, H. Sawada, C. Honda, T. Kouyama, K. Ogawa, H. Suzuki, K. Yoshioka, M. Hayakawa, N. Hirata, M. Hirabayashi, H. Miyamoto, T. Michikami, T. Hiroi, R. Hemmi, O. S. Barnouin, C. M. Ernst, K. Kitazato, T. Nakamura, L. Riu, H. Senshu, H. Kobayashi, S. Sasaki, G. Komatsu, N. Tanabe, Y. Fujii, T. Irie, M. Suemitsu, N. Takaki, C. Sugimoto, K. Yumoto, M. Ishida, H. Kato, K. Moroi, D. Domingue, P. Michel, C. Pilorget, T. Iwata, M. Abe, M. Ohtake, Y. Nakauchi, K. Tsumura, H. Yabuta, Y. Ishihara,§, R. Noguchi, K. Matsumoto, A. Miura, N. Namiki, S. Tachibana, M. Arakawa, H. Ikeda, K. Wada, T. Mizuno, C. Hirose, S. Hosoda, O. Mori, T. Shimada, S. Soldini, R. Tsukizaki, H. Yano, M. Ozaki, H. Takeuchi, Y. Yamamoto, T. Okada, Y. Shimaki, K. Shirai, Y. Iijima, H. Noda, S. Kikuchi, T. Yamaguchi, N. Ogawa, G. Ono, Y. Mimasu, K. Yoshikawa, T. Takahashi, Y. Takei, A. Fujii, S. Nakazawa, F. Terui, S. Tanaka, M. Yoshikawa, T. Saiki, S. Watanabe and Y. Tsuda, 8 May 2020, Science. | 0.856239 | 3.991144 |
Most of us learn that black holes are such potent concentrations of mass and gravity that everything around them gets sucked in, willingly or not. This should especially true near the supermassive black hole, weighing in at some 3½ million Suns, that lurks at the center of our galaxy.
But within the last decade astronomers have come to realize that swarms of stars are buzzing around that cosmic maw in precariously tight orbits. Many of these appear to be quite massive and therefore young, no older than several million years.
Cosmologists have scratched their heads in collective disbelief over this observation. Either these fat stars form elsewhere and somehow migrate inward (improbable, given their youthfulness), or else they condense from great clouds of molecular gas that sweep through the core region. Yet shouldn't the black hole's gravitational force rip the clouds to smithereens as they're dragged to their doom?
Apparently not, based on the results of a new computer simulation that appear in the August 22nd issue of Science. Ian Bonnell (University of St. Andrews) and Ken Rice (University of Edinburgh) followed the evolution of massive gas clouds as they fell into the Milky Way's core. It turns out that some of the gas isn't gobbled up by the supermassive black hole but instead forms an elliptical disk around it — and stars then form in the disk.
Remarkably, many suns end up in orbits no more than 0.1 light-year in radius. And apparently a new burst of star formation occurs whenever a gas cloud dives through the core.
It just goes to show what you can do with more than a year of number-crunching using one of the world's most powerful supercomputers — in this case the Scottish Universities Physics Alliance (SUPA) SGI Altix supercomputer. As Rice notes in an online press release, the key was careful modeling of the gas's heating and cooling during its ordeal. "This tells us how much mass is needed for part of the gas to have enough gravity to overcome its own gas pressure," he says, "and thus form a star." | 0.828916 | 3.850452 |
In the early 1960s improved observations of distant radio sources revealed that the radio emission was often coming from two regions in space located on opposite sides of a faint, visible galaxy. The double radio source might be a minute of arc or so in extent with a much smaller (in angular size) galaxy located between the radio "blobs." Double radio sources were duly found to be common, but because of the poor resolution of those early radio telescopes little more could be said than that the radio source was a double. I recall endless discussions over lunch at Jodrell Bank in which we wondered why radio sources might be double. It soon became fashionable to invoke explosive events inside galaxies, which for some unknown reason ejected material in two directions. The central galaxy, if one could be seen at all, was often observed to have very active nucleus, inferred from the Doppler shifts of their light emission that implied chaotic motion.
An alternative explanation to account for the chaos in those distant radio sources was that galaxies were in collision, with each being torn asunder by their interaction.
Whichever idea one favored, it became apparent that in these radio galaxies immense amounts of radio, light, and even X-ray energy were being generated by dramatic events in the nucleus of what was usually the most massive member of a dense cluster of galaxies.
As a teenager I used to listen to the BBC on shortwave radio and one evening heard a talk about radio astronomy by Bernard Lovell, the Director at Jodrell Bank in England. I had never heard of radio astronomy, Jodrell Bank, or Lovell. During his talk he played a tape recording of what he claimed was the sound of colliding galaxies. 1 listened to the hiss of receiver noise, which gradually grew stronger and then weaker as the radio source Cyg A passed through the beam of the Jodrell Bank telescope. This stirred my imagination and about 8 years later I began working at Jodrell Bank as a graduate student.
Was this article helpful? | 0.812124 | 3.702484 |
Astronomers Use New Methods in Search of Life in Our Universe
Astronomers are continuing their search for life in the universe with new methods. Recently they have started to pinpoint stars that have planets where life may be found. As there are billions of such stars outside our solar system there may be a chance of finding life. Every star has, on average, 1.6 planets orbiting them.
Up to now astronomers have located about 400 stars that have the building blocks of life - primarily the existence of liquid water. Only a handful has already been examined but, up to now, nothing has been found.
One of them, Gliese 581, is currently under observation by astronomers. It is a red dwarf star, one of the most common in the Milky Way, about 20 light years away from Earth. Gliese 581 is about 10 billion years old and has a mass that is only a third of our sun’s. Of the six planets orbiting around the star, two of them may have Earth-like features. One of them is about three or four times as big as our Earth and the right distance away from its sun to have life.
Australian astronomers have started to take a closer look at Gliese 581 by combining radio signals of several telescopes that are far apart from each other. Although the result was negative, the astronomers found out that this method provided an effective way of scanning the universe, one small section at a time. It allows them to observe the area with great accuracy.
Patience is required by astronomers because hundreds of thousands of searches of this kind must be done before there may be a positive result.
Radio Telescope in Mount Pleasant, Australia - Noodle snacks
- The Solar System
- The Milky Way
- First Planet From Outside Our Galaxy Found
- World's Largest Telescope to be Built in Chile
- Stars - Great Balls of Gas in our Universe
- accuracy = correctness; very exact
- although = while
- astronomer = a scientist who studies the stars and the planets
- billion = a thousand million
- building blocks = the pieces which together make it possible for something to exist
- combine = put together
- common = widespread; exists very often
- distance = space
- dwarf = very small
- effective = something that really works
- examine = to look at very closely
- existence = if something can be found
- feature = characteristic , quality
- light year = the distance that light travels in a year
- liquid = fluid, watery
- mass = large amount
- observe = watch
- on average = usually, normally
- orbit = to go around
- patience = to be able to do something for a long time before you get positive results
- pinpoint = to find the exact location of something
- primarily = mainly, most importantly
- provide = offer, give
- recently = shortly
- required = needed
- scan = look at carefully but very quickly
- several = many
- solar system = the sun and the planets that go around it | 0.849119 | 3.35718 |
Donald Savage/Dolores Beasley
Headquarters, Washington, DC
Goddard Space Flight Center, Greenbelt, MD
Space Telescope Science Institute, Baltimore, MD
Breaking up is hard to do, even for a comet. When such a cosmic break-up occurred last year, scientists watched it happen and came away with new insights and new questions.
Teams of scientists, using telescopes ranging from the W. M. Keck Observatory and NASA's Infrared Telescope Facility, both on Mauna Kea, HI, to the European Southern Observatory's (ESO) Very Large Telescope in Chile, the NASA/European Space Agency (ESA) SOHO satellite and NASA's Hubble Space Telescope, have been studying Comet LINEAR (C/1999 S4). This spectacular comet last year broke apart as it circled the Sun. The researchers' results will appear tomorrow in a special issue of the journal Science dedicated to studies of the comet.
One team, led by Dr. Michael Mumma of NASA's Goddard Space Flight Center, Greenbelt, MD, used the NASA/ESA Solar and Heliospheric Observatory (SOHO) to examine LINEAR. These scientists found the first evidence ever seen that supports the theory that comet impacts may have played a significant role in the formation of life on Earth by providing most of the water in Earth's oceans, as well as organic material. LINEAR is the first comet observed to have a composition that would allow it to carry the same type of water found in oceans on Earth.
"The idea that comets seeded life on Earth with water and essential molecular building blocks is dramatic, and for the first time, we have seen a comet with the right composition to do the job," Mumma said.
A separate announcement, also to appear in Science, is a unique observation that reveals just how much water comets of this type can carry. LINEAR, with a nucleus estimated at 2,500 to 3,300 feet (about 750 to 1,000 meters) in diameter, carried about 3.6 million tons (3.3 billion kilograms) of water within its bulk, according to astronomers who used the Solar Wind Anisotropies instrument on the SOHO spacecraft to observe water vapor released as the comet fragmented.
Pictures and more information about these findings can be found on the Internet at:
A second team, led by Dr. Hal Weaver, an astronomer at the Johns Hopkins University in Baltimore, MD, studied the broken fragments of LINEAR with the Hubble Space Telescope, the Very Large Telescope (VLT) and other ground-based telescopes. The researchers found there is not as much material in the fragments as there was in LINEAR before it broke apart. The leftover material just wouldn't add up to a comet as large as LINEAR.
Information about the Hubble and VLT observations are available on the Web at:
There are no new Hubble pictures, but previously released Hubble Space Telescope images of Comet LINEAR's breakup are available at:
Comet LINEAR completely disintegrated late last July as it made its closest approach to the Sun, at a cozy 71 million miles. Hubble tracked the comet, finding at least 16 fragments that resembled "mini-comets" with tails. Now LINEAR is little more than a trail of debris orbiting the Sun. The comet is believed to have wandered into the inner solar system from its home in the Oort Cloud, a reservoir of space debris on the outskirts of the solar system. It took comet LINEAR about 60,000 years to travel once around the Sun.
Comet LINEAR was named for the program that first spotted it, the Lincoln Near Earth Asteroid Research (LINEAR), headquartered at the Massachusetts Institute of Technology's Lincoln Labs, Lexington, MA. LINEAR is a highly successful NASA-funded program to search for near-Earth objects, which has also become a premier discoverer of comets. | 0.889312 | 3.839732 |
Federico Lelli on what dwarf galaxies tell us about the cosmological model
- What dwarf galaxies are
- How they can be used to test the standard cosmological model
- The results of exciting research on dwarf galaxies in the Centaurus group
Q: Firstly, what is a dwarf galaxy and why did you want to study them?
A: Dwarf galaxies are the most numerous and most common types of galaxies in the Universe, but they are smaller and less massive than galaxies like our own Milky Way. The Milky Way, for example, contains about 100 billion stars, while dwarf galaxies may contain anywhere from a few thousand to “only” a billion stars. One famous example of a dwarf galaxy is the Small Magellanic Cloud, which is visible to the naked eye from the Southern Hemisphere. Dwarf galaxies are important in many aspects of astronomy, but to me they are particularly interesting because they can be used to test the currently most popular cosmological model, the Lambda Cold Dark Matter (LCDM) model, in which the mysterious dark matter and dark energy constitute more than 95% of the total mass-energy budget of the Universe.
Q: How can dwarf galaxies test the cosmological model?
A: First of all, dwarf galaxies are thought to be heavily dominated by dark matter because they show large mass discrepancies. Let me explain what that means. By studying the motions of stars and gas within dwarf galaxies and using Newton’s gravitational law, we can estimate their total mass. But when we compare this number to the actual mass we see in stars and gas, the two numbers are vastly different — by a large factor, from tens to thousands depending on the object. We interpret this as evidence for large amounts of unseen dark matter inside dwarf galaxies. These galaxies are therefore prime natural laboratories to test different dark matter models or alternative gravity theories.
Over the past ten years, however, people realised that we can also test our current cosmological model by looking at the distribution of dwarf satellites around their “host” galaxies and comparing that with the prediction of computer simulations based on the LCDM model.
Q: Can you explain in more detail how this is done?
A: According to the LCDM model, galaxies form at the centres of halos of dark matter. Using supercomputers, theoreticians can simulate the formation and growth of dark matter halos over time, from the Big Bang to the present day. It turns out that massive dark matter halos, which host bright galaxies, are generally surrounded by many smaller dark matter halos, which should host dwarf galaxies. The small halos are distributed in a random, nearly spherical fashion around the big one and move in a chaotic way, like bees around a hive. This is a neat prediction that can be tested by actually looking at the motions and positions of dwarf galaxies out in the Universe.
Q: Have other researchers looked at this before?
A: Sure, and the first results raised a big scientific debate. Arguably, the best-studied galaxies in the Universe are the Milky Way and its big neighbour, the Andromeda Galaxy. Both galaxies are surrounded by several dwarf satellites. But early research realised that these dwarfs are not distributed in a random way, as predicted by cosmological simulations. It was found that the satellites of the Milky Way lie in a narrow plane, which is perpendicular to the Milky Way’s disc, and they also seem to rotate within this plane — sort of like the planets around the Sun, except the orbits of dwarf galaxies are way more complex and uncertain. Imagine a pancake-like disc of dwarf galaxies, spinning around the Milky Way.
Co-rotating planes of satellite galaxies are rare in cosmological simulations, occurring in less than 1% of simulated central dark matter halos, so people naturally thought that the Milky Way must be a bit of a weirdo. It was later discovered that the Andromeda Galaxy also hosts a plane of satellites, making this galaxy just as much of a weirdo as our own. At this point, people started to wonder whether the cosmological predictions are actually correct, or whether the Local Group of galaxies — including the Milky Way and the Andromeda Galaxy — is atypical and shouldn’t be used to test cosmology.
Q: How have you and your collaborators tried to answer these questions?
A: We decided to look at satellite galaxies outside the Local Group to test whether the Milky Way and Andromeda are indeed atypical. We started with Centaurus A (also known as Cen A), which is a big elliptical galaxy in the constellation of Centaurus, about 13 million light-years away. It’s surrounded by 31 dwarf satellites, plus another 15 candidates awaiting confirmation.
The lead author of our Science paper — Oliver Müller from the University of Basel — has previously studied the Cen A system and found that the dwarf satellites are aligned along a plane. However, this specific planar geometry of Cen A occurs about 20% of the time in cosmological simulations (one out of five), so it didn’t seem too odd at first glance. But the picture changed drastically when we looked at the motions of the satellite galaxies.
Q: What did you find?
A: It turns out that the velocities of the satellite galaxies aren’t random, as we expected from cosmological simulations. After subtracting the so-called “recession velocity” due to the expansion of the Universe, the satellite galaxies to the south of Cen A are moving away from us, while the ones to the north of Cen A are approaching us. This is consistent with coherent rotation within the plane, similar to how the satellite dwarfs are moving around the Milky Way and the Andromeda Galaxy. When we consider both the distribution and the motions of the satellite dwarfs, a configuration like Cen A becomes extremely rare in cosmological simulations: it has a probability of only 0.1%. In other words, we didn’t actually pick up a “weird” system out of thousands of “normal” ones — this can’t just be a coincidence. Instead, it seems likely that Cen A, Andromeda, and the Milky Way are normal galaxies after all, and that satellite planes are the rule rather than the exception. Perhaps there are many more planes of satellite galaxies out there just waiting to be discovered.
Q: What are the major implications of this discovery?
A: Essentially, our observations challenge the simulations. Planes of satellite dwarfs have been observed in all three major galaxies in the nearby Universe: the Milky Way, the Andromeda Galaxy, and now Cen A. This pattern is telling us something: since state-of-the-art cosmological simulations can’t explain how these planar structures are formed, perhaps we should start looking at alternatives.
For example, there is an old idea from the Swiss astrophysicist Fritz Zwicky: dwarf galaxies may form during the encounter of two large galaxies, out of small debris that is ejected by tidal forces during the interaction. This idea was proposed again by the British astrophysicist Donald Lynden-Bell in the 1970s; he was one of the first to note the planar distribution of dwarf galaxies around the Milky Way and to point out that galaxy encounters may naturally explain such geometries and coherent motions. Dwarf galaxies formed in this way, however, should be free of dark matter, so people lost interest in such an idea as the predominant dark matter paradigm took over. Our results indicate that such “old” ideas deserve a closer look.
Q: Did you face any challenges in your research?
A: The observational aspect of this work was relatively easy because we used existing data. The velocities of the dwarf satellites were measured before by other authors using various facilities and techniques. We “only” had to collect and analyse them. The challenging part was to compare reality with simulations, taking into account possible observational biases and uncertainties. In particular, we considered two large public simulations. One — called Millennium II — uses only dark matter particles and neglects the possible effect of “baryonic processes”, like the formation of stars, supernova explosions, and so on. The other — called Illustris — tries to model these complex baryonic processes to form actual galaxies inside dark matter halos. However, both simulations give essentially the same result as far as the distribution and kinematics of dwarf satellites are concerned.
Q: What do you personally find most exciting about this research topic?
A: The current cosmological model is quite successful in explaining the Universe on large scales. However, it needs to postulate two unknown substances: dark matter and dark energy. Challenging the cosmological model on small scales is one way to move forward with our understanding of dark matter and fundamental physics.
Q: So what’s your next step?
A: Next, we will measure distances and velocities of more candidate dwarf galaxies around Cen A. This will improve our statistics and allow for a more accurate comparison with cosmological simulations. We will also look for similar planar structures around other large galaxies in the Universe.
Numbers in this article
|0.1||The probability in % that the satellite system of Cen A has its current configuration, according to the standard model of dark matter|
|31||The number of dwarf galaxies currently known to orbit Centaurus A|
|95||The percentage of the mass-energy budget of the Universe taken up by dark matter and dark energy|
|13 million||The distance of Centaurus A from Earth in light-years.|
Biography Federico Lelli
Federico Lelli is an ESO Fellow in Germany. He grew up in a small Italian town called Castelferretti and studied at the University of Bologna. He obtained his PhD from the University of Groningen in the Netherlands, where his thesis on starburst dwarf galaxies was considered among the top 5% theses from the university in 2013. After a postdoc position at Case Western Reserve University in Cleveland, Ohio, he moved to Garching to join ESO as a Fellow in January 2017. | 0.856169 | 4.093586 |
The NASA Dawn spacecraft has spent more than a month on the dark side of dwarf planet Ceres as it performs a complicated dance with Ceres' gravity before entering into a circular orbit around the dwarf planet. On April 10, with the limb of the Ceres coming into view, Dawn captured several images of the Ceres' north polar region. Taken at a distance of 33,000 km (21,000 mi), they represent the highest-resolution views of Ceres to date; Future images of Ceres will show surface features at increasingly higher resolutions.
Ceres has an average diameter of about 950 km (590 mi), and is the most massive object in the main asteroid belt. Ceres comprises about 1/3 the total mass of all the bodies in the main asteroid belt, and its composition is similar to the icy moons of Jupiter and Saturn.
Using its ion propulsion system, Dawn is slowly maneuvering into its first science orbit at Ceres, which it achieve on April 23. The spacecraft will orbit at a distance of 13,500 km (8,400 mi) from the Ceres until May 9. Afterward, it will make its way to consecutively lower orbits.
Source: JPL News & Events | 0.816842 | 3.034561 |
We have no way of identifying where the Sun was born, what the surrounding environment was, or where the Sun's siblings are right now. This is easy to see from some bare numbers: the Sun's current orbital period around the Milky Way is some 250 million years, and it's been around for some 4.5 billion years, making for some 20 orbits around the galaxy since its birth. There's a lot of stellar-movement dynamics that can happen over those twenty orbits, and any siblings have long parted ways. Similarly, any stellar remnants that are close to us right now are close because we're passing by, not because we were born in their neighbourhood.
As such, whatever the source of the heavy elements in the solar system, it's several billions of years too late to figure out any individual sources.
That said, it is important to emphasize that there is no such unique source to begin with. As explained in the answer you linked to, there are plenty of such predecessors:
There are grains of material trapped inside meteorites that consist of solids that were already present in the pre-solar material. These are important because these grains were thought to have formed in individual stellar events and their isotopic compositions can be studied. These tell us that the Sun formed from material that has been inside many different stars of different types.
Moreover, if you want to place those predecessors, you are fighting against the internal mixing of the interstellar gas on a galactic scale:
Mixing in the interstellar medium is reasonably effective. The material spewed out from supernovae and stellar winds 5-12 billion years ago has had plenty of time to mix throughout the Galaxy before the Sun's birth. Turbulence and shear instabilities should distribute material on galactic length scales in a billion years or less.
This means that the Sun was not born out of the ashes of its neighbours. Instead, it was born out of the ashes of stars that might have died on the opposite side of the galaxy, several billion years before the Sun's birth, whose ashes then got thoroughly distributed by the mixing of the interstellar medium. | 0.858219 | 3.70966 |
Gliese 581g may be the new Earth.
A team of astronomers from the University of California and the Carnegie Institute of Washington say they've found a planet like ours, 20 light years (120 trillion miles) from Earth, where the basic conditions for life are good.
"The chances for life on this planet are 100 percent," Steven Vogt, a UC professor of astronomy and astrophysics says. "I have almost no doubt about it."
The planet is three times the size of Earth, but the gravity is similar.
Dr. Elizabeth Cunningham, planetarium astronomer at the Royal Observatory in Greenwich, says the discovery is a huge deal.
"It could have liquid water on the surface," she said. "That's the first step to find life."
There are hundreds of known extrasolar planets that have been discovered in the Milky Way, but this is the first that could support life.
Earthlings won't be traveling to Gliese 581g any time soon unfortunately. Scientists say a spaceship traveling close to the speed of light would take 20 years to make this journey.
But if we did - we'd find some other things familiar. The atmosphere and gravity are similar to Earth, and if you're from the polar regions, you'd definitely feel right at home. Scientists say the highest average temperature is about -12 degrees Celcius (10 Fahrenheit), but they point out that the planet doesn't have a night and day - one side continually faces the star and the other side faces the darkness of space. This means one side is blazing hot and the other freezing cold.
Gliese orbits a red dwarf star called Gliese 581. Cunningham says "it's a Goldilocks planet."
"It's not too hot, it's not too cold, it's just right" for water to form, Cunningham said.
The area is called the "Goldilocks zone."
Other planets near Gliese 581g have been discovered, but they are not habitable and are mainly comprised of gas. Gliese 581g, however, is a rocky planet.
It was discovered using the Keck telescope in Hawaii which has been observing the star Gliese 581 for 11 years.
"Keck's long-term observations of the wobble of nearby stars enabled the detection of this multi-planetary system," said Mario R. Perez, Keck program scientist at NASA headquarters in Washington.
Astronomers are excited this new planet was discovered so fast and relatively close by.
"I'm surprised we found one so fast," Cunningham said. "The implication is either we were very lucky or these planets could be relatively common."
Gliese 581g is in the constellation of Libra. While Earth takes 365 days to orbit our star, the sun, Gliese 581g orbits its star in 37 days. | 0.892822 | 3.600729 |
We still do not fully understand where all the water on this planet, including that in the ocean, originally came from. At a fundamental level we know how water in the universe comes into existence: when stars reach the end of their lives in a violent explosion called a supernova, there is enough heat and pressure to bring oxygen and hydrogen together to form water. When The Solar System was forming, 9 billion years after the big bang, there is no doubt that water would have been an ingredient in the dust cloud that went on to form The Sun and its planets. But scientists think that Earth would have been a lot hotter than it is today; and with no atmosphere any water hanging around would have simply evaporated into space. That means that The Earth must have gained its water sometime after it was formed.
The first major source of water probably came from within the Earth itself. Water trapped inside rocks and the Earth’s mantle would have been liberated through volcanic activity, eventually condensing in the atmosphere and falling as rain. However, scientists have their doubts whether this would have supplied enough water, and for this reason think that a “top-up” was probably required. The most likely source of this “top-up” is from outer space. Comets, asteroids and meteorites all contain water in the form of ice. As the Earth was maturing, collisions with these objects would have been very common. Scientists have looked at the chemical composition of the water in a number of comets, asteroids and meteorites. The closest match comes from a type of meteorite called a carbonaceous chondrite.
Not all scientists agree that the water on this planet came from space. Some say that the water released from volcanic activity would have been enough to fill the oceans on its own, while others have proposed more outlandish theories: a team in Japan believes that a thick layer of hydrogen may have once covered the Earth’s surface, eventually interacting with oxides in the Earth’s crust to form our planet’s oceans. Personally, I like the idea that every time I drink a glass of water, I am drinking defrosted ice from a meteorite that collided with the Earth billions of years ago.
This post is an excerpt from “Do Fish Sleep?: and 38 other ocean mysteries”, by David Aldridge. It is available to buy on kindle here for the reduced price of $1.46 (99p) until the end of January. To read it, you do not need to own a Kindle device, just the Kindle App which is a free download for smartphones or tablets. It can also be read with“Kindle Cloud Reader” on a PC or Laptop. | 0.824141 | 3.522012 |
First water clouds outside our solar system spotted just 7.2 light years from Earth
- WISE 0855 is the coldest known object outside of our solar system
- Conditions on the brown dwarf are similar to those on Jupiter
- Strong evidence for the existence of clouds of water or water ice
It is one of the most unusual astronomical finds ever.
First spotted in 2014, the brown dwarf known as WISE 0855 is the coldest known object outside of our solar system.
Just barely visible at infrared wavelengths with the largest ground-based telescopes, astronomers have now made another amazing find - the existence of clouds of water or water ice.
WISE 0855, the coldest known object outside, shows 'strong evidence' for the existence of clouds of water or water ice, the first detected outside of our solar system.
WHAT IS A BROWN DWARF?
A brown dwarf is essentially a failed star, having formed the way stars do through the gravitational collapse of a cloud of gas and dust, but without gaining enough mass to spark the nuclear fusion reactions that make stars shine.
The team, led by astronomers at UC Santa Cruz, succeeded in obtaining an infrared spectrum of WISE 0855 using the Gemini North telescope in Hawaii, providing the first details of the object's composition and chemistry.
Among the findings is strong evidence for the existence of clouds of water or water ice, the first such clouds detected outside of our solar system.
'We would expect an object that cold to have water clouds, and this is the best evidence that it does,' said Andrew Skemer, assistant professor of astronomy and astrophysics at UC Santa Cruz.
The research, to be published in Astrophysical Journal Letters, found conditions on the brown dwarf are similar to those on jupiter.
With about five times the mass of Jupiter, WISE 0855 resembles that gas giant planet in many respects.
Its temperature is about 250 degrees Kelvin, or minus 10 degrees Fahrenheit, making it nearly as cold as Jupiter, which is 130 degrees Kelvin.
'WISE 0855 is our first opportunity to study an extrasolar planetary-mass object that is nearly as cold as our own gas giants,' Skemer said.
Previous observations of the brown dwarf, published in 2014, provided tentative indications of water clouds based on very limited photometric data.
Skemer, a coauthor of the earlier paper, said obtaining a spectrum (which separates the light from an object into its component wavelengths) is the only way to detect an object's molecular composition.
WISE 0855 is too faint for conventional spectroscopy at optical or near-infrared wavelengths, but thermal emission from the deep atmosphere at wavelengths in a narrow window around 5 microns offered an opportunity where spectroscopy would be 'challenging but not impossible,' he said.
This diagram illustrates the locations of the star systems closest to the sun. The year when the distance to each system was determined is listed after the system's name.
The team used the Gemini-North telescope in Hawaii and the Gemini Near Infrared Spectrograph to observe WISE 0855 over 13 nights for a total of about 14 hours.
'It's five times fainter than any other object detected with ground-based spectroscopy at this wavelength,' Skemer said.
'Now that we have a spectrum, we can really start thinking about what's going on in this object.
'Our spectrum shows that WISE 0855 is dominated by water vapor and clouds, with an overall appearance that is strikingly similar to Jupiter.'
JUPITER'S GIANT AURORA
Jupiter's auroras were first discovered by the Voyager 1 spacecraft in 1979.
A thin ring of light on Jupiter's nightside looked like a stretched-out version of our own auroras on Earth.
But later, astronomers discovered the auroras were best visible in the ultraviolet. Scientists also discovered the planet has X-ray aurora too.
Jupiter's aurora are larger than our entire planet and unlike those on Earth, occur almost continuously.
This suggests that the mechanism causing this light show is different from that on Earth.
While Earth's Northern and Southern lights are triggered by energetic particles from the sun slamming into gas atoms high in the atmosphere, Jupiter appears to have another source.
Scientists are using the Hubble Space Telescope to watch Jupiter's aurora (pictured) for more than a month in the hope of trying to unravel what causes these enormous light shows. The ultraviolet and X-ray aurora on Jupiter occur continuously on the giant planet and are the size of the entire planet Earth
Scientists believe its powerful magnetic field accellerates charged particles from the space around it towards its poles, to cause similar interactions.
The volcanic moon Io spews oxygen and sulfur ions into Jupiter's spinning magnetic field, which sends them hurtling towards the planet below.
Upon entering the atmosphere, their electrons are first stripped away by molecules they run into, but as they slow down they start grabbing electrons back. The 'charge exchange reaction' produces intense X-ray auroras.
Yet scientists have been baffled as to how Jupiter's magnetic field accelerates these particles.
The researchers developed atmospheric models of the equilibrium chemistry for a brown dwarf at 250 degrees Kelvin and calculated the resulting spectra under different assumptions, including cloudy and cloud-free models.
The models predicted a spectrum dominated by features resulting from water vapor, and the cloudy model yielded the best fit to the features in the spectrum of WISE 0855.
Comparing the brown dwarf to Jupiter, the team found that their spectra are strikingly similar with respect to water absorption features.
One significant difference is the abundance of phosphine in Jupiter's atmosphere.
Phosphine forms in the hot interior of the planet and reacts to form other compounds in the cooler outer atmosphere, so its appearance in the spectrum is evidence of turbulent mixing in Jupiter's atmosphere.
The absence of a strong phosphine signal in the spectrum of WISE 0855 implies that it has a less turbulent atmosphere.
'The spectrum allows us to investigate dynamical and chemical properties that have long been studied in Jupiter's atmosphere, but this time on an extrasolar world,' Skemer said.
Nasa's Jupiter probe Juno arrived at its destination last week - and experts say the brown dwarf has similar conditions.
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Why is this discovery important?
Unlike earlier discoveries of exo-planets, all seven planets could possibly have liquid water — a key to life as we know it on Earth — with three planets having the greatest chance.
This is by far the largest collection of Earth-like planets in the habitable ‘Goldilocks’ zone of a star — neither too close nor too far from a star, which raises the possibility of liquid water being present on the surface. Only Earth has liquid water in the solar system.
Why is this name given?
NASA has named the system of planets after the ‘Transiting Planets and Planetesimals Small Telescope,’ which is located in Chile. This telescope first discovered three of the planets in May 2016. These exoplanets are located outside of our solar system and orbit a star.
Why is the discovery of these Exoplanets such a big deal, and what should you know about them?
1. The star in TRAPPIST-1 is classified as an ultra-cool dwarf, which NASA points out is in contrast to our Sun. The ultra-cool dwarf has a lower mass than the Sun, and also much lower temperatures. What this means is even if planets are orbiting close to the dwarf sun, it is so cool that liquid water will be able to survive on these planets.
2. The planets are Earth-sized. The seven wonders of TRAPPIST-1 are the first Earth-size planets that have been found orbiting this kind of star.
3. Scientists said they need to study the atmospheres before determining whether these rocky, terrestrial planets could support some sort of life.
4. TRAPPIST-1 holds the record for the greatest number of habitable-zone planets found around a single star outside our solar system.
What are habitable zones/goldilocks?
In astronomy and astrobiology, the circumstellar habitable zone (CHZ), or simply the habitable zone , is the range of orbits around a star within which a planetary surface can support liquid water given sufficient atmospheric pressure. | 0.879673 | 3.396586 |
The Pinwheel Galaxy, as taken by Hubble Space Telescope
|Observation data (J2000 epoch)|
|Right ascension||14h 03m 12.6s|
|Declination||+54° 20′ 57″|
|Helio radial velocity||241 ± 2 km/s|
|Distance||20.9 ± 1.8 Mly (6.4 ± 0.5 Mpc)|
|Apparent magnitude (V)||7.86|
|Number of stars||1 trillion (1012)|
|Size||~170,000 ly in diameter|
|Apparent size (V)||28′.8 × 26′.9|
|Messier 101, M101, NGC 5457, UGC 8981, PGC 50063, Arp 26|
The Pinwheel Galaxy (also known as Messier 101, M101 or NGC 5457) is a face-on spiral galaxy distanced 21 million light-years (six megaparsecs) away from Earth in the constellation Ursa Major. It was discovered by Pierre Méchain on March 27, 1781, it was communicated to Charles Messier who verified its position for inclusion in the Messier Catalogue as one of its final entries.
On February 28, 2006, NASA and the European Space Agency released a very detailed image of the Pinwheel Galaxy, which was the largest and most detailed image of a galaxy by Hubble Space Telescope at the time. The image was composed of 51 individual exposures, plus some extra ground-based photos.
Pierre Méchain, the discoverer of Messier 101, described it as a "nebula without star, very obscure and pretty large, 6' to 7' in diameter, between the left hand of Bootes and the tail of the great Bear. It is difficult to distinguish when one lits the [grating] wires."
William Herschel noted in 1784 that "...in my 7, 10, and 20-feet [focal length] reflectors shewed a mottled kind of nebulosity, which I shall call resolvable; so that I expect my present telescope will, perhaps, render the stars visible of which I suppose them to be composed."
Lord Rosse observed M101 in his 72-inch diameter Newtonian reflector during the second half of the 19th century. He was the first to make extensive note of the spiral structure and made several sketches.
To observe the spiral structure in modern instruments requires a fairly large instrument, very dark skies, and a low power eyepiece.
Structure and composition
M101 is a large galaxy, with a diameter of 170,000 light-years. By comparison, the Milky Way has a diameter of 100,000 light years. It has around a trillion stars, twice the number in the Milky Way. It has a disk mass on the order of 100 billion solar masses, along with a small central bulge of about 3 billion solar masses.
M101 has a high population of H II regions, many of which are very large and bright. H II regions usually accompany the enormous clouds of high density molecular hydrogen gas contracting under their own gravitational force where stars form. H II regions are ionized by large numbers of extremely bright and hot young stars; those in M101 are capable of creating hot superbubbles. In a 1990 study, 1264 H II regions were cataloged in the galaxy. Three are prominent enough to receive New General Catalogue numbers - NGC 5461, NGC 5462, and NGC 5471.
M101 is asymmetrical due to the tidal forces from interactions with its companion galaxies. These gravitational interactions compress interstellar hydrogen gas, which then triggers strong star formation activity in M101's spiral arms that can be detected in ultraviolet images.
In 2001, the x-ray source P98, located in M101, was identified as an ultra-luminous X-ray source - a source more powerful than any single star but less powerful than a whole galaxy - using the Chandra X-ray Observatory. It received the designation M101 ULX-1. In 2005, Hubble and XMM-Newton observations showed the presence of an optical counterpart, strongly indicating that M101 ULX-1 is an x-ray binary. Further observations showed that the system deviated from expected models - the black hole is just 20 to 30 solar masses, and consumes material (including captured stellar wind) at a higher rate than theory suggests.
M101 has six prominent companion galaxies: NGC 5204, NGC 5474, NGC 5477, NGC 5585, UGC 8837 and UGC 9405. As stated above, the gravitational interaction between M101 and its satellites may have triggered the formation of the grand design pattern in M101. M101 has also probably distorted the companion galaxy NGC 5474. M101 and its companion galaxies comprise most or possibly all of the M101 Group.
On August 24, 2011, a Type Ia supernova, SN 2011fe, initially designated PTF 11kly, was discovered in M101. The supernova was visual magnitude 17.2 at discovery and reached magnitude 9.9 at its peak. This was the fourth supernova recorded in M101. The first, SN 1909A, was discovered by Max Wolf in January 1909 and reached magnitude 12.1. SN 1951H reached magnitude 17.5 in September 1951 and SN 1970G reached magnitude 11.5 in January 1970.
- Messier 74 – a similar face-on spiral galaxy
- Messier 83 – a similar face-on spiral galaxy that is sometimes called the Southern Pinwheel Galaxy
- Messier 99 – a similar face-on spiral galaxy
- Triangulum Galaxy – another galaxy sometimes called the Pinwheel Galaxy
- NASA Content Administrator, ed. (31 May 2012). "The Pinwheel Galaxy". NASA. Retrieved 4 March 2017.
- "NED results for object MESSIER 101". NASA/IPAC Extragalactic Database. Retrieved 2006-12-06.
- Shappee, Benjamin; Stanek, Kris (June 2011). "A New Cepheid Distance to the Giant Spiral M101 Based on Image Subtraction of Hubble Space Telescope/Advanced Camera for Surveys Observations". Astrophysical Journal. 733 (2): 124. arXiv:1012.3747. Bibcode:2011ApJ...733..124S. doi:10.1088/0004-637X/733/2/124.
- R. W. Sinnott, ed. (1988). The Complete New General Catalogue and Index Catalogue of Nebulae and Star Clusters by J. L. E. Dreyer. Sky Publishing Corporation / Cambridge University Press. ISBN 978-0-933346-51-2.
- "Distance Results for Messier 101". NASA/IPAC Extragalactic Database. Retrieved 2010-05-01.
- "M 101". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2009-11-29.
- Armando, Gil de Paz; Boissier; Madore; Seibert; et al. (2007). "The GALEX Ultraviolet Atlas of Nearby Galaxies". Astrophysical Journal Supplement. 173 (2): 185–255. arXiv:astro-ph/0606440. Bibcode:2007ApJS..173..185G. doi:10.1086/516636.
- "Hubble's Largest Galaxy Portrait Offers a New High-Definition View". NASA. 28 February 2006. Retrieved 4 February 2018.
- Hartmut Frommert. "Messier 101". SEDS Messier Database. Retrieved 4 March 2018.
- "M 101". Messier Objects Mobile — Charts, Maps & Photos. 2016-10-11. Retrieved 4 March 2018.
- Shappee, Benjamin J.; Stanek, K. Z. (2018). "Evidence for an Intermediate-Mass Milky Way from Gaia DR2 Halo Globular Cluster Motions". The Astrophysical Journal. 873 (2): 118. arXiv:1804.11348. doi:10.3847/1538-4357/ab089f.
- Plait, Phil (2006-02-28). "Hubble delivers again: M101". Slate. ISSN 1091-2339. Retrieved 2018-05-04.
- Comte, G.; Monnet, G. & Rosado, M. (1979). "An optical study of the galaxy M 101 - Derivation of a mass model from the kinematic of the gas". Astronomy and Astrophysics. 72: 73–81. Bibcode:1979A&A....72...73C.
- Immler, Stefan & Wang, Q. Daniel (2001). "ROSAT X-Ray Observations of the Spiral Galaxy M81". The Astrophysical Journal. 554 (1): 202. arXiv:astro-ph/0102021. Bibcode:2001ApJ...554..202I. doi:10.1086/321335.
- Hodge, Paul W.; Gurwell, Mark; Goldader, Jeffrey D.; Kennicutt, Robert C., Jr. (August 1990). "The H II regions of M101. I - an atlas of 1264 emission regions". Astrophysical Journal Supplement Series. 73: 661–670. Bibcode:1990ApJS...73..661H. doi:10.1086/191483.
- Giannakopoulou-Creighton, J.; Fich, M.; Wilson, C. D. (1999). "Star formation in the giant HII regions of M101". The Astrophysical Journal. 522 (1): 238–249. arXiv:astro-ph/9903334. Bibcode:1999ApJ...522..238G. doi:10.1086/307619.
- Waller, William H.; Bohlin, Ralph C.; Cornett, Robert H.; Fanelli, Michael N.; et al. (20 May 1997). "Ultraviolet Signatures of Tidal Interaction in the Giant Spiral Galaxy M101". The Astrophysical Journal. 481 (1): 169. arXiv:astro-ph/9612165. Bibcode:1997ApJ...481..169W. doi:10.1086/304057.
- Kuntz, K.D.; et al. (10 February 2005). "The Optical Counterpart of M101 ULX-1". The Astrophysical Journal. 620 (1): L31–L34. Bibcode:2005ApJ...620L..31K. doi:10.1086/428571. hdl:2060/20050123916.
- Liu, Jifeng; Bregman, Joel N.; Bai, Yu; Justham, Stephen; et al. (2013). "Puzzling accretion onto a black hole in the ultraluminous X-ray source M101 ULX-1". Nature. 503 (7477): 500–3. arXiv:1312.0337. Bibcode:2013Natur.503..500L. doi:10.1038/nature12762. PMID 24284727.
- Chandar, Rupali; Whitmore, Bradley; Lee, Myung Gyoon (2004-08-10). "The Globular Cluster Systems of Five Nearby Spiral Galaxies: New Insights fromHubble Space TelescopeImaging". The Astrophysical Journal. 611 (1): 220–244. doi:10.1086/421934. ISSN 0004-637X.
- A. Sandage; J. Bedke (1994). Carnegie Atlas of Galaxies. Carnegie Institution of Washington. ISBN 978-0-87279-667-6.
- R. B. Tully (1988). Nearby Galaxies Catalog. Cambridge University Press. ISBN 978-0-521-35299-4.
- P. Fouque; E. Gourgoulhon; P. Chamaraux; G. Paturel (1992). "Groups of galaxies within 80 Mpc. II – The catalogue of groups and group members". Astronomy and Astrophysics Supplement (2nd ed.). 93: 211–233. Bibcode:1992A&AS...93..211F.
- A. Garcia (1993). "General study of group membership. II – Determination of nearby groups". Astronomy and Astrophysics Supplement. 100: 47–90. Bibcode:1993A&AS..100...47G.
- Giuricin, G.; Marinoni, C.; Ceriani, L.; Pisani, A. (2000). "Nearby Optical Galaxies: Selection of the Sample and Identification of Groups". Astrophysical Journal. 543 (1): 178–194. arXiv:astro-ph/0001140. Bibcode:2000ApJ...543..178G. doi:10.1086/317070.
- Nugent, Peter; et al. (24 August 2011). "Young Type Ia Supernova PTF11kly in M101". The Astronomer's Telegram. 3581: 1. Bibcode:2011ATel.3581....1N. Retrieved 25 August 2011.
- Nugent, Peter; et al. "Supernova Caught in the Act". Retrieved 7 September 2011.
- Hartmut Frommert & Christine Kronberg (15 Sep 2011). "Supernova 2011fe in M101". Retrieved 17 Sep 2011.
- Stoyan, Ronald Atlas of the Messier Objects, Cambridge University Press 2008 page 329
- "Transient object followup reports". Central Bureau for Astronomical Telegrams.
|Wikimedia Commons has media related to Pinwheel Galaxy.|
- SEDS: Spiral Galaxy M101
- The Pinwheel Galaxy on WikiSky: DSS2, SDSS, GALEX, IRAS, Hydrogen α, X-Ray, Astrophoto, Sky Map, Articles and images
- Harutyunyan, Avet; Merrifield, Mike; Dhillon, Vik. "M101 – Pinwheel Galaxy". Deep Space Videos. Brady Haran.
- Nemiroff, R.; Bonnell, J., eds. (14 April 2009). "M101: The Pinwheel Galaxy". Astronomy Picture of the Day. NASA. Retrieved 4 March 2018.
- "Pinwheel Galaxy – Messier 101". Constellation Guide. 31 May 2013.
- Yoshida, Takayuki. "Spiral Galaxy, M101". Astrophotography by Takayuki Yoshida. | 0.869454 | 3.789242 |
The nature of dark matter, observed to date only through its gravitational interactions on galactic and cosmological scales, remains a profound mystery. The indirect evidence for dark matter includes galactic matter orbital rates inconsistent with visible and invisible baryonic matter, gravitational lensing of galaxies, lensing of the cosmic microwave background (CMB), and cosmological scale observations including CMB temperature fluctuation angular power spectra and CMB polarization distributions. All observations are consistent with the now-standard LCDM cosmological model of so-called cold (nonrelativistic) relic dark matter, relic standard-model matter, and dark energy characterized by a cosmological constant. The WMAP data constrains the matter density, baryonic matter density, and neutrino density to 0.136, 0.023, and 0.003 of the critical density implying the dark component dominates the matter in the universe.
Relic weakly interacting massive particles (WIMPs) may be a significant dark matter component according to models motivated by both the galactic and cosmological observations and beyond-the-standard-model elementary particle ideas such as supersymmetry (SUSY). The simplest SUSY WIMP model assumes a single relic lightest supersymmetric particle protected from decay to known matter particles by R-parity symmetry. If such particles interact with each other with weak-scale cross sections, implying their interactions are mediated by particles with weak scale (~TeV) or heavier masses, the density of the relics can be similar to that inferred from indirect measurements. In a naïve model, WIMP interactions are spin-independent and coherent amongst nucleons in a nucleus. Their detection therefore favors a high Z target. In some models, WIMP interactions may be suppressed because the interactions are spin-dependent and largely cancel amongst nucleons . Other suppression mechanisms may be imagined .
Direct searches for dark matter attempt to observe signals of WIMP elastic interactions with normal matter (nuclei). The velocity distribution of cold dark matter particles in the Milky Way relative to a target nucleus on Earth and the (essentially unconstrained) mass of the relic particle governs the mean energy transfer. Sensitive direct search measurements based on nuclear recoil have probed masses as low as a few GeV. At low WIMP mass, the energy transfer is difficult to observe. At high masses, the expected flux, constrained by the measured dark matter density, limits sensitivity. Additional searches for axion-like light weight dark matter particles require other techniques.
Direct searches complement searches for WIMP production in the form of anomalous missing energy events in collider experiments like CMS and ATLAS, and complement indirect astrophysical annihilation signatures investigated by the space-based and terrestrial cosmic ray/gamma ray detection experiments. A concordance of observations of missing energy events ascribable to WIMPS of a certain mass in colliders, of new mediators or standard model mediated interactions, along with direct observations of WIMP elastic collisions with recoil energies consistent with that mass and with a cross section consistent with predictions, and finally of galactic scale annihilation or other dark matter interactions could provide a compelling picture of dark matter.
The search for direct signals of dark matter was identified by 2014 Particle Physics Project Prioritization Panel [P5] as a priority for research . The direct dark matter search field has been active for some years and a variety of technologies have been deployed or tested including cryogenic crystal devices with low thresholds but also low target size, gaseous detectors with directional sensitivity but also low mass, and liquid noble gas scintillation and ionization detectors. The latter, while lacking directionality, may be pushed to the multi-ton scale as recognized by P5. Presently in operation, the LUX experiment uses a 370-kg liquid-xenon target as a time projection chamber to search for high mass WIMP dark matter. Limits from the initial LUX run have led the field. A factor of ten in collection time during the run due to end in 2016 will improve these limits or possibly provide first evidence.
The LUX-Zeplin (LZ) liquid-xenon WIMP dark matter direct search project concept was selected by the DOE Office of High Energy Physics for support as one 2nd generation direct dark matter search for the Cosmic Frontier Program. The LZ experiment will scale up proven two-phase liquid xenon detection technology to significantly extend previous searches and discover or provide the best limits on WIMP dark matter for WIMP mass above a few GeV. Our proposal is focused upon the LZ project.
A signal for WIMP dark matter would be the first direct evidence for physics beyond the standard model. The next step would be a further scale up and experiments dedicated to providing directional information to validate the WIMP wind model. The indication of the mass scale and interaction cross section would focus searches for signatures at colliders. The LZ experiment can search for WIMPS without background approaching a “floor” represented by interactions of solar and galactic neutrinos. These signals will be of interest as well as searches for axionic dark matter and other exotic phenomena.
The figure at left from the LZ Conceptual Design Report (CDR) compares the projected sensitivity of the LZ to existing and expected LUX limits along with some SUSY motivated models. The figure shows the projected 90% confidence level (CL) sensitivity for the SI WIMP-nucleon cross sections for LZ (solid blue) along with the current world’s-best limits from LUX (dashed blue), the LUX 300-day projection (dotted blue), and the final ZEPLIN result (dot-dashed blue). Regions above the curves are excluded. The green and yellow bands display the 68% (1s) and 95% (2s) ranges of the expected LZ 90% CL limit. The grey small-dashed line is an estimate of the 90% CL for the S2-only technique. The grey long-dashed line indicates the potential improved low-mass reach if the lower energy threshold is lowered. The regions where background NRs from cosmic neutrinos emerge, and an ultimate neutrino floor, are shown. The grey-colored regions are favored by recent scans of the five-parameter CMSSM, which include the most current constraints from LHC results. The purple and blue points are pMSSM models, where 15 parameters are scanned. The number of standard deviations (s) that quantify consistency are higher for models that are more inconsistent with very recent LHC data. Further explanation and references are provided in the CDR. | 0.838571 | 4.288608 |
Because more massive, closely-orbiting planet exert much greater gravitational forces on their host star than smaller, more distant planets, there is a significant observational bias. We are much more likely to detect these planets (i.e. "hot Jupiters") because their observable effects (Doppler wobble, gravitational lensing, etc) are more significant.
The below image (from here) shows you that we're still mostly unable to detect planets like those in our own Solar system (the gray circles are our Solar planets). It's just too hard.
I don't study planetary formation (yet!), so I can't speak well for the theoretical side of things. All we've managed to collect so far is the very lowest-hanging fruit, so it is highly likely that there are is a large number of Earth-like planets out there too.
The authors of this article on the Kepler-10 system (you'll need MNRAS access) suggest planet-planet gravitational scattering or collision-merger events. The Scholarpedia article provides a bit more brief reading on these mechanisms. Here is a review article from 2009, and a more in-depth review from 2006. | 0.843776 | 3.232574 |
The dawn of gravitational wave astronomy
The first detection of gravitational waves announced earlier this year by the LIGO-Virgo Team has quickly been honoured with many of the most prestigious prizes in physics and science and is widely regarded as one of the scientific breakthroughs of the decade.
At the University of Birmingham, we have long operated at the cutting edge of science and have now invested £6 million in a new Institute of Gravitational Wave Astronomy, recognising the great opportunities in this exciting new field of science.
Our institute's launch coincided with further recognition of Birmingham's place on the front line of science, with this week witnessing the awarding of 2016's Nobel Prize in Physics to three British scientists for their work in topological properties of matter. Two of this illustrious trio - Professors David Thouless and Mike Kosterlitz - are former University of Birmingham academics. Alongside this, Professor Sir Fraser Stoddart, former Head of School of Chemistry, is one of the three joint winners of this year's Nobel Prize in Chemistry for his work into the design and synthesis of molecular machines.
But what is it that makes this detection of gravitational wave, using the Laser Interferometer Gravitational-Wave Oberservatories (LIGO) instruments in Louisiana and Washington, so important and why did this scientific achievement resonate so much with an audience outside of science?
Gravitational waves are distortions in space and time itself that are produced by violent events in our Universe. According to Einstein's theory of gravity, such waves were generated by the Big Bang at the very beginning of our Universe, and are creating by colliding compact objects such as black holes and neutron stars, and by star explosions. By measuring these waves we can learn about these events and the Universe as a whole: we can do astronomy but in a transformative new way.
Astronomy is a fundamental science. It seeks to answer fundamental questions, for example, what is the shape and evolution of the Universe, where do planets and stars come from and how has everything evolved from the very beginning of time? By studying the night sky with telescopes, we have found answers and can study new worlds. But much more remains hidden and new questions have arisen, sometimes literally in dark places into which we cannot probe using ordinary telescopes.
Gravitational waves are a completely different kind of radiation, emitted by dark objects and not absorbed by gas or dust in-between stars. With gravitational wave detectors we can now pierce the veil that obscures many fascination cosmic objects. We have already discovered the first pair of black holes and as the detectors become better and better we will make many more exciting discoveries.
We have just had the first glimpse of the gravitational wave sky. To go beyond that we will improve the instruments that can measure these waves, the modeling of the complex physical processes that generate them, and the techniques to identify these cosmic signals in the data. By making use of the interaction of light and matter at the quantum level, we will develop new laser detectors with record-breaking sensitivity, on the ground and in space.
Gravitational wave astronomy emerges at the intersection of many research areas, such as optics, metrology, interferometry, quantum macroscopic systems, big-data and theoretical physics. By successfully bringing together expertise for a common purpose, we can push the boundaries of knowledge at the most fundamental level. The world-wide scientific community has recognised the huge and transformational potential inherent in this new area, from fundamental physics to transfer technology, for wider impact and the training of the new generations in STEM subjects through cutting-edge research.
Looking to the future, our new Gravitational Wave Institute aims to gather experts from many different research fields and to to strengthen the links across research groups and technology centres to shape the future of astronomy and fundemental physics. The first detection of a gravitational wave was just the beginning; we have opened a new window to the Universe. From now on we will detect many gravitational waves, but what we are going to discover next is anybody's guess. Expect more news and big surprises!
Professor Andreas Freise and Professor Alberto Vecchio
School of Physics and Astronomy, University of Birmingham | 0.817558 | 3.938767 |
Old as the M4 Planet
In the universe, we may or may not be alone, but at least there seem to be plenty of planets. Over the last decade, extra-solar planet-finding has become a growth industry, with some 100 already identified by their effect on the motion of their central star (see Far Out Planets). The pull of the planet’s gravity makes the star wobble back and forth as the planet orbits, and the more massive the planet, the larger and more easily detected is the wobble. Consequently, the extrasolar planets that astronomers can find tend to be large, some with more than four times the mass of Jupiter.
When did the first planets form? Astronomers had predicted that planet formation would occur only in a solar system with heavy elements. Since the early universe was almost entirely hydrogen and helium, planet formation was expected only after supernova explosions had seeded the universe with the heavier elements. To test this idea, the Hubble Space Telescope looked for large, close-in planets, known as “hot Jupiters,” in the globular cluster 47 Tucanae, a densely-packed region in our galaxy containing some of the oldest stars in the universe (see image). Rather than observing a star’s wobble, the Hubble scanned many stars repeatedly, looking for a reduction in brightness due to a planet passing in front of the star (making a “transit”). The Hubble found nothing, which supported the existing theory of planet formation, but a different investigation would eventually yield surprising results.
The Hubble Space Telescope, which searched for planets in the globular cluster 47 Tucanae
(image courtesy of NASA).
In 1999, astronomers searched for extrasolar planets with the Hubble Space Telescope by looking for planetary "shadows" passing in front of stars. No large, Jupiter-like planets were detected at that time in this globular cluster of 35,000 stars. Image courtesy of Hubble Space Telescope (STScI and NASA).
In a study begun in 1988, astronomers had been timing the radio pulses from a pulsar, a collapsed supernova remnant (see Black Holes). The pulsar is located in our galaxy in a globular cluster, M4 (see image), which formed about 13 billion years ago. Precise timing of its pulses showed that the pulsar is wobbling, and that the companion is a white dwarf, a collapsed star about the size of Earth. Further study revealed a second companion, with less mass—either a small star or a planet.
The globular cluster M4, consisting of about 100,000 stars, which formed within the first billion years of the Big Bang; the green rectangle shows the location of the newly-discovered planetary system. (image courtesy of NOAO/AURA/NSF)
Hubble space telescope image of the white dwarf (indicated by the arrow), one of the two stellar remnants in the ancient planetary system in the globular cluster M4 (image courtesy of NASA/H Richter UBC).
Then a new team of investigators analyzed detailed images of this system taken by the Hubble Space Telescope in the 1990s. The Hubble cameras are so sensitive that they could detect this white dwarf, even though its brightness is about the equivalent of a 100 watt light bulb seen at the distance from Earth to the moon. Astronomers identified the white dwarf (see image), studied its spectrum, and deduced its mass. The result was that the second companion turned out to have a mass of 2.5 times Jupiter’s, so small that it had to be a planet, not a star.
This exotic system has a Jupiter-like planet in orbit around a pair of stellar remnants. The planet is several billion miles from these dead stars, about the distance of Uranus from the sun, and takes about a century to make one revolution. The artist’s conception shows the two central stars as seen from the vicinity of the planet.
Could this planet have supported life so early in the history of the universe? Probably not, because as a first-generation planet, it was composed of mostly hydrogen and helium and lacked carbon, nitrogen, sulfur, oxygen, and various other essential elements, at least for life as we know it. Also, this gas giant had no solid surface to provide an environment for large, advanced life forms like those on Earth.
Even so, the discovery of this new planet is exciting, because it shows that planets did indeed form early in the history of the universe. Now the planet-finders can investigate more stars in globular clusters for additional first-generation planets.
Artist’s conception of the Jupiter-like planet in orbit around a pulsar and a white dwarf in the globular cluster M4 (image courtesy of NASA).
Hubble Space Telescope
Two views of the globular cluster 74 Tucanae, one from a ground-based telescope and one from the Hubble. (image courtesy of NASA/H Richter UBC) | 0.898111 | 4.010836 |
- Astronomers are building a space telescope to study the nearby stars.
- the telescope will be small along with a camera attached to it.
- Studying these nearby stars will help astronomers help study the way planets orbit around the stars.
Astronomers are in the process of building a small space telescope to explore the flares and sunspots of small nearby stars to assess how habitable the space environment is for planets orbiting them.
The telescope with a diameter of 9 centimetres, or 3.6 inches, will be fitted on a spacecraft known as the Star-Planet Activity Research CubeSat, or SPARCS to be launched in 2021, to focus on stars that are small, dim and cool by comparison to the sun.
These stars — known as M dwarfs — are less than half the sun’s size and temperature and they shine with barely one per cent of its brightness.
The telescope will be built alongside a camera with two ultraviolet (UV)-sensitive detectors to be optimised for observations using UV light, which strongly affects the planet’s atmosphere and its potential to harbour life on the surface.
“People have been monitoring M dwarfs as best they can in visible light. But the stars’ strongest flares occur mainly in the ultraviolet, which Earth’s atmosphere mostly blocks,” said Evgenya Shkolnik, Assistant Professor at the Arizona State University.
Although the orbiting Hubble Space Telescope can view stars at ultraviolet wavelengths unhindered, its overcrowded observing schedule would let it dedicate only the briefest of efforts to M dwarfs.
The telescope uses a mirror system with coatings optimized for ultraviolet light. Together with the camera, the system can measure very small changes in the brightness of M dwarf stars to carry out the primary science of the mission.
M dwarfs are exceedingly common that they make up three-quarters of all the stars in our Milky Way galaxy as well as nearly 40 billion rocky planets in habitable zones around these stars, meaning that most of the habitable-zone planets in our galaxy orbit M dwarfs.
Capturing lengthy observations of M dwarfs will let astronomers study how stellar activity affects planets that orbit the star. IANS | 0.859263 | 3.921459 |
A reader who saw my earlier post on the Vortex math talk at a TEDx conference sent me a link to an absolutely dreadful video that features some more crackpottery about the magic of vortices.
The old heliocentric model of our solar system,
planets rotating around the sun, is not only boring,
but also incorrect.
Our solar system moves through space at 70,000km/hr.
Now picture this instead:
(Image of the sun with a rocket/comet trail propelling
it through space, with the planets swirling around it.)
The sun is like a comet, dragging the planets in its wake.
Can you say “vortex”?
The science of this is terrible. The sun is not a rocket. It does not propel itself through space. It does not have a tail. It does not leave a significant “wake”. (There is interstellar material, and the sun moving through it does perturb it, but it’s not a wake: the interstellar material is orbiting the galactic center just like the sun. Gravitational effects do cause pertubations, but it’s not like a boat moving through still water, producing a wake.) Even if you stretch the definition of “wake”, the sun certainly does not leave a wake large enough to “drag” the planets. In fact, if you actually look at the solar system, the plane the ecliptic – the plane where the planets orbit the sun – is at a roughly 60 degree angle to the galactic ecliptic. If planetary orbits were a drag effect, then you would expect the orbits to be perpendicular to the galactic ecliptic. But they aren’t.
If you look at it mathematically, it’s even worse. The video claims to be making a distinction between the “old heliocentric” model of the solar system, and their new “vortex” model. But in fact, mathematically, they’re exactly the same thing. Look at it from a heliocentric point of view, and you’ve got the heliocentric model. Look at the exact same system from point that’s not moving relative to galactic center, and you get the vortex. They’re the same thing. The only difference is how you look at it.
And that’s just the start of the rubbish. Once they get past their description of their “vortex” model, they go right into the woo. Vortex is life! Vortex is sprirituality! Oy.
If you follow their link to their website, it gets even sillier, and you can start to see just how utterly clueless the author of this actually is:
(In reference to a NASA image showing the interstellar “wind” and the heliopause)
Think about this for a minute. In this diagram it seems the Solar System travel to the left. When the Earth is also traveling to the left (for half a year) it must go faster than the Sun. Then in the second half of the year, it travels in a “relative opposite direction” so it must go slower than the Sun. Then, after completing one orbit, it must increase speed to overtake the Sun in half a year. And this would go for all the planets. Just like any point you draw on a frisbee will not have a constant speed, neither will any planet.
See, it’s a problem that the planets aren’t moving at a constant speed. They speed up and slow down! Oh, the horror! The explanation is that they’re caught by the sun’s wake! So they speed up when they get dragged, until they pass the sun (how does being dragged by the sun ever make them faster than the sun? Who knows!), and then they’re not being dragged anymore, so they slow down.
This is ignorance of physics and of the entire concept of frame of reference and symmetry that is absolutely epic.
There’s quite a bit more nonsense, but that’s all I can stomach this evening. Feel free to point out more in the comments! | 0.906341 | 3.578304 |
A group of English astronomers (from the University of Warwick in the UK) and American astronomers (from the University of Colorado, Boulder, Wesleyan University) studying dying stars call their field of study necro-planetology. Necro is a Greek prefix for death.
Back in 2015, white dwarf WD 1145+017 started to act bizarre, dimming one every 5 hours. So, the scientists concluded it might be due to tidal disruption. Necro-planetology is using WD 1145+017’s death to prove it is a valid concept.
WD 1145+017 is called a white dwarf because is in its final evolutionary state. It is dying. And because it iv very dense about 10 solar masses. It is giving its lasts breath 570 light-years away from us, in the Virgo constellation. To be precise, this last breath stared 175 million years ago. But if it is indeed in a tidal disruption process, then it might actually be dying.
Necroplanetology Could Reveal More Secrets Of The Space
The tidal disruption event is a planet’s spaghettification. That’s a scientific word, even if it doesn’t seem possible. And it means exactly what it says. Remember the scene in Lady and the Trump, when Lady and the Trump eat spaghetti? Sorry, when they slurp spaghetti and end up kissing?
It’s the same in space when a blackhole slurps a star. Or when a dying white dwarf such as WD 1145+017 is slurping the surrounding planets’ mantles. It’s like a death kiss. The necro-planetology scientists made some simulations that revealed this disruptive behavior is what caused the unusual dimming.
WD 1145+017 is not a very nice star. It’s like a mean moribund clinging on healthy people that stood with them through the entire process. And it looks like it isn’t a singular case. KIC 8462852, AKA Tabby’s star, ZTF J0139+5245, and WD J0914+1914 were also doing it.
But necro-planetology scientists seem to be quite excited about these findings. “This multi-pronged approach would use the death of these planetary systems in action to study fundamental properties of exoplanetary bodies that are otherwise inaccessible: a study in necro-planetology,” they say. | 0.859948 | 3.263723 |
Scientists Have Captured the First Ever Image of a Black Hole
Scientists at the National Science Foundation announced Wednesday morning they have captured the very first image of a black hole. Using a global network of telescopes over the course of more than a decade, scientists were able to locate and photograph the supermassive black hole at the center of a galaxy known as M87.
While we have known for some time black holes exist, direct visual evidence of one has been elusive. Black holes are some of the most mysterious objects in the universe, due to the extreme gravitational pull they exhibit, making it impossible for even light to escape its pull. The point where all matter and light crosses the point of no return is known as the event horizon, which is what you see in this photo. The dark circular part of the photo is the area where no light can escape from the pull of the black hole, while the reddish area is superheated matter and gas being sucked in by extreme gravitational forces.
The galaxy in which it was found is 55-million years from Earth near the Virgo galaxy cluster. This particular supermassive black hole is estimated to have a mass that is 6.5 billion times that of our sun.
“We have seen what we thought was unseeable,” said Sheperd Doeleman, director of the Event Horizon Telescope Collaboration. “We have seen and taken a picture of a black hole.”
The network of telescopes to make this incredible discovery are known as the Event Horizon Telescope Collaboration, and more than 200 researchers were involved in pulling off this project. The project is aptly named for its goal of photographing the part of a black hole where light is about to cross the point of no return.
By using the combined power of eight telescopes across the world, scientists were able to create a virtual telescope around the same size as the Earth itself. The process involved a highly coordinated sequence of positioning from observatories originating in different locations around the globe.
Scientists are still working on imaging Sagittarius A*, the supermassive black hole at the center of our own galaxy, though they say it’s a harder image to source when compared to the one located in M87.
With this discovery, we are making significant progress in understanding one of the most strange complexities in the entire universe. Black holes “have exotic properties and are mysterious to us, yet with more observations like this one they are yielding their secrets,” said National Science Foundation director France Cordova. | 0.85249 | 3.373112 |
Hubble’s view of the Deep Impact collision. Image credit: Hubble. Click to enlarge.
The NASA/ESA Hubble Space Telescope captured the dramatic effects of the collision early on 4 July between the Deep Impact impactor spacecraft and Comet 9P/Tempel 1.
This sequence of images shows the comet before and after the impact. The image at left shows the comet just minutes before the impact. The encounter occurred at 07:52 CEST (05:52 UT/GMT).
In the middle image, captured 15 minutes after the collision, Tempel 1 appears four times brighter than in the pre-impact photograph.
Astronomers noticed that the inner cloud of dust and gas surrounding the comet’s nucleus increased by about 200 kilometres in size.
The impact caused a brilliant flash of light and a constant increase in the brightness of the inner cloud of dust and gas.
Hubble continued to monitor the comet, snapping another image (at right) 62 minutes after the encounter. In this photograph, the gas and dust ejected during the impact are expanding outward in the shape of a fan.
The fan-shaped debris is travelling at about 1800 kilometres an hour, or twice as fast as the speed of a commercial jet. The debris extends about 1800 kilometres from the nucleus.
The potato-shaped comet is 14 kilometres wide and 4 kilometres long. Tempel 1’s nucleus is too small even for the Hubble telescope to resolve.
The visible-light images were taken by the high-resolution camera on Advanced Camera for Surveys instrument. The Hubble Space Telescope is a project of international co-operation between ESA and NASA.
Original Source: ESA/Hubble News Release | 0.835101 | 3.090752 |
The search for neutrinos from deep space gives us a new vista on some of the most violent processes in the universe, says astrophysicist Ray Jayawardhana
What’s so interesting about neutrinos?
They are elementary particles with rather quirky properties. They hardly ever interact with matter, and that makes them really difficult to pin down. Trillions pass through your body every second but there’s only maybe a 25 per cent chance that one will interact with an atom in your body in your whole lifetime.
Where do they come from?
Some come from the heart of the sun; others are produced in the upper atmosphere when cosmic rays hit atoms. Then there are geoneutrinos that are produced in the Earth’s interior as radioactive elements decay. The vast majority of neutrinos that pass through Earth are from those three sources. But there’s a great deal of interest in detecting neutrinos that come from much farther away – cosmic neutrinos.
Why are cosmic neutrinos such a big deal?
Some of the more violent phenomena in the universe produce neutrinos. So there are some really fundamental questions that cosmic neutrinos allow us to probe. So far, though, only two batches have been detected. The first were from the supernova 1987A, a star that exploded in a satellite galaxy of the Milky Way. More recently, the IceCube neutrino observatory in Antarctica reported some 28 energetic neutrinos that are almost certainly cosmic in origin.
How significant was the IceCube detection?
It marks the beginnings of neutrino astronomy. Astronomy is not like other sciences; we usually don’t get to put our quarry under the microscope or analyse it in the lab. We have to depend on feeble light from distant sources. By now, we’ve fairly well explored the electromagnetic spectrum. There are only two other potential cosmic messengers that we know of. One is gravitational waves, which still have not been detected directly. The other is cosmic neutrinos.
Do the IceCube scientists know the precise origins of the neutrinos they saw?
Not yet. But the two candidate sources are the supermassive black holes at the hearts of galaxies and gamma-ray bursts, which are most likely produced by the deaths of incredibly massive stars.
What else could cosmic neutrinos reveal?
There should have been neutrinos produced seconds after the big bang. With existing astronomy we can only look back to about 380,000 years after the big bang. If we could detect these “relic” neutrinos, we could look back to within seconds of the birth of the universe. The problem is that they are now low in energy, and therefore extremely difficult to detect. Present detectors are nowhere close to being sensitive enough to see them.
Can neutrinos capture the public imagination in the same way as the Higgs boson?
The Higgs has been a terrific story. But neutrinos allow us to probe some really profound questions and I think that makes them truly interesting. They’re ready to take centre stage.
Ray Jayawardhana is professor of astrophysics at the University of Toronto, Canada, and author of The Neutrino Hunters (Oneworld/Farrar, Straus and Giroux). He will be speaking at London’s Royal Institution on 21 January
This article appeared in print under the headline “Cosmic messengers”
More on these topics: | 0.87253 | 4.125597 |
A double star system has been flipping between two alter egos, according to observations with NASA's Chandra X-ray Observatory and the National Science Foundation's Karl F. Jansky Very Large Array (VLA). Using nearly a decade and a half worth of Chandra data, researchers noticed that a stellar duo behaved like one type of object before switching its identity, and then returning to its original state after a few years. This is a rare example of a star system changing its behavior in this way.
Astronomers found this volatile double, or binary, system in a dense collection of stars, the globular cluster Terzan 5, which is located about 19,000 light years from Earth in the Milky Way galaxy. This stellar duo, known as Terzan 5 CX1, has a neutron star (the extremely dense remnant left behind by a supernova explosion) in close orbit around a star similar to the Sun, but with less mass.
In this new image of Terzan 5 (right), low, medium and high-energy X-rays detected by Chandra are colored red, green and blue respectively. On the left, an image from the Hubble Space Telescope shows the same field of view in optical light. Terzan 5 CX1 is labeled as CX1 in the Chandra image.
In binary systems like Terzan 5 CX1, the heavier neutron star pulls material from the lower-mass companion into a surrounding disk. Astronomers can detect these so-called accretion disks by their bright X-ray light, and refer to these objects as "low-mass X-ray binaries."
Spinning material in the disk falls onto the surface of the neutron star, increasing its rotation rate. The neutron star can spin faster and faster until the roughly 10-mile-wide sphere, packed with more mass than the Sun, is rotating hundreds of times per second. Eventually, the transfer of matter slows down and the remaining material is swept away by the whirling magnetic field of the neutron star, which becomes a millisecond pulsar. Astronomers detect pulses of radio waves from these millisecond pulsars as the neutron star's beam of radio emission sweeps over the Earth during each rotation.
While scientists expect the complete evolution of a low-mass X-ray binary into a millisecond pulsar should happen over several billion years, there is a period of time when the system can switch rapidly between these two states. Chandra observations of Terzan 5 CX1 show that it was acting like a low-mass X-ray binary in 2003, because it was brighter in X-rays than any of the dozens of other sources in the globular cluster. This was a sign that the neutron star was likely accumulating matter.
In Chandra data taken from 2009 to 2014, Terzan 5 CX1 had become about ten times fainter in X-rays. Astronomers also detected it as a radio source with the VLA in 2012 and 2014. The amount of radio and X-ray emission and the corresponding spectra (the amount of emission at different wavelengths) agree with expectations for a millisecond pulsar. Although the radio data used did not allow a search for millisecond pulses, these results imply that Terzan 5 CX1 underwent a transformation into behaving like a millisecond pulsar and was blowing material outwards. By the time Chandra had observed Terzan 5 CX1 again in 2016, it had become brighter in X-rays and changed back to acting like a low-mass X-ray binary again.
To confirm this pattern of "Jekyll and Hyde" behavior, astronomers need to detect radio pulses while Terzan 5 CX1 is faint in X-rays. More radio and X-ray observations are planned to search for this behavior, along with sensitive searches for pulses in existing data. Only three confirmed examples of these identity-changing systems are known, with the first discovered in 2013 using Chandra and several other X-ray and radio telescopes.
The study of this binary was led by Arash Bahramian of the International Centre for Radio Astronomy Research (ICRAR), Australia and was published in the September 1st, 2018 issue of The Astrophysical Journal. A preprint is available here.
Two other recent studies have used Chandra observations of Terzan 5 to study how neutron stars in two different low-mass X-ray binaries recover after having had large amounts of material dumped on their surface by a companion star. Such studies are important for understanding the structure of a neutron star's outer layer, known as its crust.
In one of these studies, of the low-mass X-ray binary Swift J174805.3–244637 (T5 X-3 for short), material dumped onto the neutron star during an X-ray outburst detected by Chandra in 2012 heated up the star's crust. The crust of the neutron star then cooled down, taking about a hundred days to fall back to the temperature seen before the outburst. The rate of cooling agrees with a computer model for such a process.
In a separate Chandra study of a different low-mass X-ray binary in Terzan 5, IGR J17480–2446 (T5 X-2 for short) the neutron star was still cooling when its temperature was taken five and a half years after it was known to have an outburst. These results show this neutron star's crust ability to transfer, or conduct, heat may be lower than what astronomers have found in other cooling neutron stars in low-mass X-ray binaries. This difference in the ability to conduct heat may be related to T5 X-2 having a higher magnetic field compared to other cooling neutron stars, or being much younger than T5 X-3.
Both T5 X-3 and T5 X-2 are labeled in the image.
The work on the rapidly cooling neutron star, led by Nathalie Degenaar of the University of Amsterdam in the Netherlands, was published in the June 2015 issue of the Monthly Notices of the Royal Astronomical Society and a preprint is available here. The study of the slowly cooling neutron star, led by Laura Ootes, then of the University of Amsterdam, was published in the July 2019 issue of the Monthly Notices of the Royal Astronomical Society and a preprint is available here.
NASA's Marshall Space Flight Center manages the Chandra program. The Smithsonian Astrophysical Observatory's Chandra X-ray Center controls science and flight operations from Cambridge and Burlington, Massachusetts. | 0.880661 | 3.983577 |
An air-mass thunderstorm, also called an "ordinary","single cell", or "garden variety" thunderstorm, is a thunderstorm that is generally weak and usually not severe. These storms form in environments where at least some amount of Convective Available Potential Energy (CAPE) is present, but very low levels of wind shear and helicity. The lifting source, which is a crucial factor in thunderstorm development, is usually the result of uneven heating of the surface, though they can be induced by weather fronts and other low-level boundaries associated with wind convergence. The energy needed for these storms to form comes in the form of insolation, or solar radiation. Air-mass thunderstorms do not move quickly, last no longer than an hour, and have the threats of lightning, as well as showery light, moderate, or heavy rainfall. Heavy rainfall can interfere with microwave transmissions within the atmosphere.
Lightning characteristics are related to characteristics of the parent thunderstorm, and could induce wildfires near thunderstorms with minimal rainfall. On unusual occasions there could be a weak downburst and small hail. They are common in temperate zones during a summer afternoon. Like all thunderstorms, the mean-layered wind field the storms form within determine motion. When the deep-layered wind flow is light, outflow boundary progression will determine storm movement. Since thunderstorms can be a hazard to aviation, pilots are advised to fly above any haze layers within regions of better visibility and to avoid flying under the anvil of these thunderstorms, which can be regions where hail falls from the parent thunderstorm. Vertical wind shear is also a hazard near the base of thunderstorms which have generated outflow boundaries.
The trigger for the lift of the initial cumulus cloud can be insolation heating the ground producing thermals, areas where two winds converge forcing air upwards, or where winds blow over terrain of increasing elevation. The moisture rapidly cools into liquid drops of water due to the cooler temperatures at high altitude, which appears as cumulus clouds. As the water vapor condenses into liquid, latent heat is released which warms the air, causing it to become less dense than the surrounding dry air. The air tends to rise in an updraft through the process of convection (hence the term convective precipitation). This creates a low-pressure zone beneath the forming thunderstorm, otherwise known as a cumulonimbus cloud. In a typical thunderstorm, approximately 5×108 kg of water vapor is lifted into the Earth's atmosphere.As they form in areas of minimal vertical wind shear, the thunderstorm's rainfall creates a moist and relatively cool outflow boundary with undercuts the storm's low level inflow, and quickly causes dissipation. Waterspouts, small hail, and strong wind gusts can occur in association with these thunderstorms.
Also known as single cell thunderstorms, these are the typical summer thunderstorms in many temperate locales. They also occur in the cool unstable air which often follows the passage of a cold front from the sea during winter. Within a cluster of thunderstorms, the term "cell" refers to each separate principal updraft. Thunderstorm cells occasionally form in isolation, as the occurrence of one thunderstorm can develop an outflow boundary which sets up new thunderstorm development. Such storms are rarely severe and are a result of local atmospheric instability; hence the term "air mass thunderstorm". When such storms have a brief period of severe weather associated with them, it is known as a pulse severe storm. Pulse severe storms are poorly organized due to the minimal vertical wind shear in the storm's environment and occur randomly in time and space, making them difficult to forecast. Between formation and dissipation, single cell thunderstorms normally last 20–30 minutes.
The two major ways thunderstorms move are via advection of the wind and propagation along outflow boundaries towards sources of greater heat and moisture. Many thunderstorms move with the mean wind speed through the Earth's troposphere, or the lowest 8 kilometres (5.0 mi) of the Earth's atmosphere. Younger thunderstorms are steered by winds closer to the Earth's surface than more mature thunderstorms as they tend not to be as tall. If the gust front, or leading edge of the outflow boundary, moves ahead of the thunderstorm, the thunderstorm's motion will move in tandem with the gust front. This is more of a factor with thunderstorms with heavy precipitation (HP), such as air-mass thunderstorms. When thunderstorms merge, which is most likely when numerous thunderstorms exist in proximity to each other, the motion of the stronger thunderstorm normally dictates future motion of the merged cell. The stronger the mean wind, the less likely other processes will be involved in storm motion. On weather radar, storms are tracked by using a prominent feature and tracking it from scan to scan.
Convective rain, or showery precipitation, occurs from cumulonimbus clouds. It falls as showers with rapidly changing intensity. Convective precipitation falls over a certain area for a relatively short time, as convective clouds such as thunderstorms have limited horizontal extent. Most precipitation in the tropics appears to be convective. GHz.Graupel and hail are good indicators of convective precipitation and thunderstorms. In mid-latitudes, convective precipitation is intermittent and often associated with baroclinic boundaries such as cold fronts, squall lines, and warm fronts. High rainfall rates are associated with thunderstorms with larger raindrops. Heavy rainfall leads to fading of microwave transmissions starting above the frequency of 10 gigahertz (GHz), but is more severe above frequencies of 15
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Relationships between lightning frequency and the height of precipitation within thunderstorms have been found. Thunderstorms which show radar returns above 14 kilometres (8.7 mi) in height are associated with storms which have more than ten lightning flashes per minute. There is also a correlation between the total lightning rate and the size of the thunderstorm, its updraft velocity, and amount of graupel over land. The same relationships fail over tropical oceans, however. Lightning from low precipitation (LP) thunderstorms is one of the leading causes of wildfires.
In areas where these thunderstorms form in isolation and horizontal visibility is good, pilots can evade these storms rather easily. In more moist atmospheres which become hazy, pilots navigate above the haze layer in order to get a better vantage point of these storms. Flying under the anvil of thunderstorms is not advised, as hail is more likely to fall in such areas outside the thunderstorm's main rain shaft.When an outflow boundary forms due to a shallow layer of rain-cooled air spreading out near ground level from the parent thunderstorm, both speed and directional wind shear can result at the leading edge of the three-dimensional boundary. The stronger the outflow boundary is, the stronger the resultant vertical wind shear will become.
Hail is a form of solid precipitation. It is distinct from ice pellets, though the two are often confused. It consists of balls or irregular lumps of ice, each of which is called a hailstone. Ice pellets fall generally in cold weather while hail growth is greatly inhibited during cold surface temperatures.
Cumulonimbus is a dense, towering vertical cloud, forming from water vapor carried by powerful upward air currents. If observed during a storm, these clouds may be referred to as thunderheads. Cumulonimbus can form alone, in clusters, or along cold front squall lines. These clouds are capable of producing lightning and other dangerous severe weather, such as tornadoes and hailstones. Cumulonimbus progress from overdeveloped cumulus congestus clouds and may further develop as part of a supercell. Cumulonimbus is abbreviated Cb.
A thunderstorm, also known as an electrical storm or a lightning storm, is a storm characterized by the presence of lightning and its acoustic effect on the Earth's atmosphere, known as thunder. Relatively weak thunderstorms are sometimes called thundershowers. Thunderstorms occur in a type of cloud known as a cumulonimbus. They are usually accompanied by strong winds, and often produce heavy rain and sometimes snow, sleet, or hail, but some thunderstorms produce little precipitation or no precipitation at all. Thunderstorms may line up in a series or become a rainband, known as a squall line. Strong or severe thunderstorms include some of the most dangerous weather phenomena, including large hail, strong winds, and tornadoes. Some of the most persistent severe thunderstorms, known as supercells, rotate as do cyclones. While most thunderstorms move with the mean wind flow through the layer of the troposphere that they occupy, vertical wind shear sometimes causes a deviation in their course at a right angle to the wind shear direction.
A supercell is a thunderstorm characterized by the presence of a mesocyclone: a deep, persistently rotating updraft. For this reason, these storms are sometimes referred to as rotating thunderstorms. Of the four classifications of thunderstorms, supercells are the overall least common and have the potential to be the most severe. Supercells are often isolated from other thunderstorms, and can dominate the local weather up to 32 kilometres (20 mi) away. They tend to last 2–4 hours.
A mesocyclone is storm-scale region of rotation (vortex), typically around 2 to 6 mi in diameter, within a thunderstorm. In the northern hemisphere it is particularly found in the right rear flank of a supercell or often on the eastern, or front, flank of an HP storm. The circulation of a mesocyclone covers an area much larger than the tornado that may develop within it.
A squall is a sudden, sharp increase in wind speed lasting minutes, contrary to a wind gust lasting seconds. They are usually associated with active weather, such as rain showers, thunderstorms, or heavy snow. Squalls refer to the increase to the sustained winds over that time interval, as there may be higher gusts during a squall event. They usually occur in a region of strong sinking air or cooling in the mid-atmosphere. These force strong localized upward motions at the leading edge of the region of cooling, which then enhances local downward motions just in its wake.
In meteorology, precipitation is any product of the condensation of atmospheric water vapour that falls under gravity from clouds. The main forms of precipitation include drizzle, rain, sleet, snow, ice pellets, graupel and hail. Precipitation occurs when a portion of the atmosphere becomes saturated with water vapor, so that the water condenses and "precipitates". Thus, fog and mist are not precipitation but suspensions, because the water vapor does not condense sufficiently to precipitate. Two processes, possibly acting together, can lead to air becoming saturated: cooling the air or adding water vapor to the air. Precipitation forms as smaller droplets coalesce via collision with other rain drops or ice crystals within a cloud. Short, intense periods of rain in scattered locations are called "showers."
A squall line or quasi-linear convective system (QLCS) is a line of thunderstorms forming along or ahead of a cold front. In the early 20th century, the term was used as a synonym for cold front. It contains heavy precipitation, hail, frequent lightning, strong straight-line winds, and possibly tornadoes and waterspouts. Strong straight-line winds can occur where the squall line is in the shape of a bow echo. Tornadoes can occur along waves within a line echo wave pattern (LEWP), where mesoscale low-pressure areas are present. Some bow echoes which develop within the summer season are known as derechos, and they move quite fast through large sections of territory. On the back edge of the rainband associated with mature squall lines, a wake low can be present, sometimes associated with a heat burst.
An outflow boundary, also known as a gust front, is a storm-scale or mesoscale boundary separating thunderstorm-cooled air (outflow) from the surrounding air; similar in effect to a cold front, with passage marked by a wind shift and usually a drop in temperature and a related pressure jump. Outflow boundaries can persist for 24 hours or more after the thunderstorms that generated them dissipate, and can travel hundreds of kilometers from their area of origin. New thunderstorms often develop along outflow boundaries, especially near the point of intersection with another boundary. Outflow boundaries can be seen either as fine lines on weather radar imagery or else as arcs of low clouds on weather satellite imagery. From the ground, outflow boundaries can be co-located with the appearance of roll clouds and shelf clouds.
This is a list of meteorology topics. The terms relate to meteorology, the interdisciplinary scientific study of the atmosphere that focuses on weather processes and forecasting.
A weather front is a boundary separating two masses of air of different densities, and is the principal cause of meteorological phenomena outside the tropics. In surface weather analyses, fronts are depicted using various colored triangles and half-circles, depending on the type of front. The air masses separated by a front usually differ in temperature and humidity.
An overshooting top is a dome-like protrusion shooting out of the top of the anvil of a thunderstorm and into the lower stratosphere. When an overshooting top is present for 10 minutes or longer, it is a strong indication that the storm is severe.
A multicellular thunderstorm cluster is a thunderstorm that is composed of multiple cells, each being at a different stage in the life cycle of a thunderstorm. It appears as several anvils clustered together. A cell is an updraft/downdraft couplet. These different cells will dissipate as new cells form and continue the life of the multicellular thunderstorm cluster with each cell taking a turn as the dominant cell in the group.
In meteorology, the various types of precipitation often include the character or phase of the precipitation which is falling to ground level. There are three distinct ways that precipitation can occur. Convective precipitation is generally more intense, and of shorter duration, than stratiform precipitation. Orographic precipitation occurs when moist air is forced upwards over rising terrain, such as a mountain.
Atmospheric convection is the result of a parcel-environment instability, or temperature difference layer in the atmosphere. Different lapse rates within dry and moist air masses lead to instability. Mixing of air during the day which expands the height of the planetary boundary layer leads to increased winds, cumulus cloud development, and decreased surface dew points. Moist convection leads to thunderstorm development, which is often responsible for severe weather throughout the world. Special threats from thunderstorms include hail, downbursts, and tornadoes.
Convective storm detection is the meteorological observation, and short-term prediction, of deep moist convection (DMC). DMC describes atmospheric conditions producing single or clusters of large vertical extension clouds ranging from cumulus congestus to cumulonimbus, the latter producing thunderstorms associated with lightning and thunder. Those two types of clouds can produce severe weather at the surface and aloft.
A storm cell is an air mass that contains up and down drafts in convective loops and that moves and reacts as a single entity, functioning as the smallest unit of a storm-producing system. An organized grouping of thunder clouds will thus be considered as a series of storm cells with their up/downdrafts being independent or interfering one with the other.
Atmospheric instability is a condition where the Earth's atmosphere is generally considered to be unstable and as a result the weather is subjected to a high degree of variability through distance and time. Atmospheric stability is a measure of the atmosphere's tendency to discourage or deter vertical motion, and vertical motion is directly correlated to different types of weather systems and their severity. In unstable conditions, a lifted thing, such as a parcel of air will be warmer than the surrounding air at altitude. Because it is warmer, it is less dense and is prone to further ascent.
The following is a glossary of tornado terms. It includes scientific as well as selected informal terminology.
This glossary of meteorology is a list of terms and concepts relevant to meteorology and atmospheric science, their sub-disciplines, and related fields. | 0.827051 | 3.705058 |
‘Smiley face’ – when you hear that, most likely you would think of an emoticon, not planets aligning to form one!
The moon, Jupiter and Venus are going to be showing off for us on the 16th of May 2020, by aligning in a rare position that will form a smiley face in the sky!
This rare spectacle is called conjunction and is not to be missed, as the last time this happened was 12 years ago in 2008, so not a regular occurrence. In 2007 this also happened in the Philippines when the sky lit up at night.
An explanation by Space.com of alignment, or occultation is it “happens when one object passes in front of another from an observer’s perspective. A simple example is a solar eclipse. From a certain area on Earth, the Moon passes in front of the sun and either partially or totally blocks the light. So, we can say that the sun is eclipsed or occulted.”
Venus passed in front of Jupiter in 1818 and more than likely this occultation will happen again in 2065.
Even thought this occurrence that will take place in May might seem to be an occultation, it is actually a conjunction, RMG explains “In astronomy, a conjunction occurs when any two astronomical objects (such as asteroids, Moons, planets, and stars) appear to be close together in the sky, as observed from Earth.”
What is particularly interesting with this special event is how the human brain identifies with it. As when we see this phenomenon, our minds are geared to ‘take a picture’ of it to give it a ‘label’ and in this scenario, it will be a smiley face. Actually it is just planets aligning during their usual cycle around the sun, but forming a smiley face sounds appealing!
What is rare, is that Jupiter does not usually align so close to the moon as Venus regularly does once a month. So now when Jupiter does, it will look like it and Venus are two eyes and the moon is the big mouth with a delightful smile.
#HeadlineChallenge: The world needs reasons to smile – and the solar system is about to give us a helping hand. On May 16, a crescent moon, beneath Venus & Jupiter, will form a smiley face in the sky…@PeteBarronMedia goes with PUT ON A HAPPY SPACE. pic.twitter.com/G6Tmz0Lx34
— BBC Radio Tees (@BBCTees) March 30, 2020
Australia saw this event in 2008 at nighttime between 20h00 and 23h00 with Jupiter being the right eye and Venus being the left one. The next time they will see this happen again in in 2036.
So if you would like to see the skies smiling down on you, remember to look up on the 16th of May 2020!
Via healthy life box | 0.805028 | 3.26491 |
10 Hypothetical Astronomical Objects That Could Actually Exist
Space has undoubtedly been a fascinating part of reality for humanity. Ever since we were able to understand our surroundings, we’ve looked up at the stars in search for answers, inspiration, and constancy. Space has been the muse for hundreds of movies and thousands of books. It has inspired calendars and horoscopes that detail how the arrangement of astronomical objects can predict personality traits and major life events.
Space has also inspired numerous visions of the future. We’ve conjured up scenarios of interplanetary travel, alien communication, and even time travel via wormholes. The items on this list look like they have been taken from an old science fiction book. However, numerous scientists believe these objects could exist somewhere in the vastness of space. Here are the top ten hypothetical astronomical objects that could actually exist.
10 Zombie Star
As the name suggests, this type of star is one that, in a way, comes back from the dead. We’ve all heard of a supernova being referred to as the “death” of a star. In most cases, supernovae do mark the end of stars’ lives, since, during those grand explosions, the star is completely obliterated. However, scientists at NASA now believe that a faint supernova could leave behind a surviving portion of the dying dwarf star.
Astronomers first thought about the possibility of zombie stars when they observed a faint blue star feeding energy to its larger companion star. This process ignited a relatively small supernova, a Type Iax, which is low in brightness and does not spew out as much stellar mass as its cousin, the Type Ia supernova. So far, this is the only known way a white dwarf can explode. Typically, stars that explode at the end of their lifetimes are large, massive, and have very short life spans. White dwarfs, on the other hand, are cooler and tend to live longer, since they do not typically explode. Instead, they tend to expel their mass and create a planetary nebula. NASA scientists believe they have identified 30 of these Type Iax supernovae that leave behind a surviving white dwarf, but additional evidence is needed to safely say that they exist.
9 White Hole
White holes were theorized by scientists who were working with black holes. While they were working through the complex mathematics associated with black holes, they found that by assuming the singularity at the center of a black hole had no mass, or by assuming that there was no mass within the event horizon, a white hole could be created.
The math explains that if white holes are real, they would behave exactly unlike black holes. That is, instead of sucking up all the matter around them, they would eject matter into the universe. However, the math also states that white holes could only exist if there was absolutely no matter inside the event horizon, not even a tiny cookie crumb. In the instance one atom of matter enters the white hole’s event horizon, it would collapse and disappear, so even if these white holes existed in the beginning of our universe, their life spans would have been incredibly short, since our universe is filled with matter.
8 Dyson Sphere
The concept of a Dyson sphere was first introduced by Freeman Dyson, a physicist and astronomer who explored the idea through a thought experiment. He imagined a solar system–sized solar power collector. He believed a civilization could enclose its star in a cloud of satellite-type objects (or a “shell” or “ring of matter” in Dyson’s words) in order to beam 100 percent of the star’s radiation to a planet. Dyson created this thought experiment as a way to identify possible alien life in the universe. If we were to find a Dyson sphere, it could indicate the presence of a highly advanced alien civilization.
Here’s a cool fact: If we had the technology to create a Dyson sphere around the Sun, we would generate 384 yottawatts of energy, aka the total power output of the Sun. (Yotta- is the largest decimal unit prefix. It is equal to ten to the 24th power, or one septillion, or one million million million million.)
7 Black Dwarf
Black dwarf—the name itself does not invoke sci-fi vibes as “zombie star” does. However, the concept behind a black dwarf is equally as interesting as all the other hypothetical objects on this list. So far, astronomers have found white dwarfs, brown dwarfs, and red dwarfs. However, black dwarfs have never been seen and are purely theoretical. Astronomers believe they could be formed from white dwarfs that have cooled for a sufficiently long time, to the point where their temperature matches the temperature of the Cosmic Microwave Background. The CMB is the radiation left over from the Big Bang that fills up the entire universe. It currently has an average temperature of 2.7 Kelvin.
These black dwarfs are thought to be invisible, since their temperature is so low and they have no internal source of energy. Theoretically, if a 5-Kelvin white dwarf was to turn into a black dwarf, it would take 1015 years. Therefore, the universe is still too young to have created any black dwarfs!
6 Quark Star
Quark stars, also called strange stars, are thought to be composed of a soup of quarks—the fundamental constituents of matter. Astronomers believe that these stars can be created after a medium-sized star (about 1.44 times the size of our Sun) has run out of fuel and has entered the collapsing stage of its lifetime. As it collapses, it squeezes protons and electrons together, eventually forming neutrons. However, scientists think that if the star is heavy enough and continues collapsing after this stage, the neutrons that were created could break down into their component quarks under the immense pressure, creating an incredibly dense type of matter.
A paper published in 2012 delves into the hypothetical nature of these strange quark stars. The authors of the paper explain that these stars could be enveloped in a thin nuclear “crust,” consisting of heavy ions immersed in an electron gas. However, they could also exist without the crust. In that case, the quark stars would possess ultra-high electric fields that could reach up to 1019 Volts per centimeter!
5 Ocean Planet
As the name suggests, ocean planets, or water worlds, are thought to be composed entirely of vast, uninterrupted oceans. The idea of water worlds became popular when NASA announced the existence of two planets outside of our solar system: Kepler-62e and Kepler-62f. These planets are thought to be water worlds that could harbor a wealth of aquatic life.
A paper published in June 2004 explains how these types of planets could be formed. It is believed that they form relatively far away from their parent star and slowly migrate toward it (over a time period of about a million years). The planet would have to come five to ten times closer to the star, depending on how far away it initially formed. The paper delves into the internal structure of the planets as well as how deep their oceans could be and what their atmospheres could be composed of. Interesting read!
4 Chthonian Planets
The idea of Chthonian planets became popular thanks to an extrasolar planet nicknamed Osiris. NASA scientists were baffled when they detected carbon and oxygen for the first time in an atmosphere outside of our solar system. However, Osiris’s atmosphere was seen to be rapidly evaporating.
Scientists have designated a new class of worlds called Chthonian planets, which are created when gas giants, like Jupiter, enter a critical distance from their parent star. When they get too close, their outer layers begin to rapidly evaporate. Chthonian planets are thus the remnants of these gas giants, which have been stripped of their outer layers, leaving behind a dense central core.
3 Preon Star
A preon star is something that could follow a quark star. As a star is compressed to the point where it becomes a quark star and is still massive enough to continue its collapse, scientists believe that the quarks themselves could break down into these theoretical preons.
So far, scientists have not found a way to break down quarks, so they remain the main constituents of matter. However, if quarks are made of other individual particles—these so-called preons—stars could technically achieve this even denser state, one of matter created entirely of a soup of hyper-dense preons.
2 Ghost Galaxy
Ghost galaxies, also called dark galaxies, are galaxies that have very few stars. They’re so inefficient at making stars that they’re thought to be mostly composed of gas and dust, making them basically invisible. As of now, they remain theoretical for this very fact, but astronomers believe that dark galaxies are likely to exist. An international team of scientists even thinks they have found the first dark galaxy. However, more data analysis needs to be done before it is confirmed.
Astronomers believe they have also found a different type of ghost galaxy, one that is 99 percent dark matter. They named it Dragonfly 44, and it seems to be the Milky Way’s dark doppelganger in mass, but it contains very few stars and is different in its structure. If this galaxy is ever observed or analyzed in enough detail, it could change how astronomers perceive galaxy formation and dark matter.
1 Cosmic Strings
Cosmic strings are an insane idea, but the craziest part about them is that they could actually exist. Cosmic strings are slight defects in the fabric of space and time that were created at the beginning of time, left over from the formation of the universe. If one were to interact with one of these defects, one could create a “closed time-like curve,” which would allow for backward time travel. Scientists have speculated how they can make time machines out of these cosmic strings. They believe that by putting two of them close enough together, or one string and one black hole, they could create an array of these closed time-like curves.
To better visualize this, picture the cosmic strings as loops of space-time. Imagine picking up one loop and throwing it across space directly toward another loop. Then, imagine jumping on a space ship and flying around them in a perfect figure eight. This would allow you to emerge at any random point in space and time!
Although these objects are purely theoretical, astronomers believe that, if they exist, they would be very small “lines” in the fabric of space, and their effects would be incredibly strange. It is also believed that their existence could explain bizarre effects observed in faraway galaxies.
I’m a physics student at the University of Pennsylvania. | 0.906466 | 3.211805 |
Potentially helping to answer the question of how did we all get here, scientists have found evidence of ideal conditions for the formation of microbial life on Earth – sodium-rich, alkaline fluids present in the early Solar System.
And where did they find this evidence? In a meteorite formed billions of years ago in the system's asteroid belt, and found on our planet in 2000. It turns out the rock contains mineral grains forged in a sodium-rich, alkaline liquid, conditions that, according to McMaster University in Canada, are "preferential for the synthesis of amino acids – the building blocks of life – opening the door for microbial life to form as early as 4.5 billion years ago."
The sample, known as Tagish Lake meteorite and discovered in Yukon, Canada, was analysed by researchers at various organizations including the Royal Ontario Museum (ROM), McMaster, and York University in the North American nation. They managed to pick out features a few nanometres in size on the rock using atom probe tomography.
Calcium, magnesium, and sodium gathered on the meteorite when it was in the Solar System's asteroid belt some 4.5 billion years ago. The unique framboidal structure of these chemicals reveals our system was once a wet alkaline environment that contained large amounts of sodium, the boffins concluded in a study published in America's Proceedings of the National Academy of Sciences this week.
From the Reg archives: Bubbly meteor hints at seeds of lifeREAD MORE
In effect, these structures are a link between the chemical environment of the early Solar System and the microbial life that emerged on our world. Scientists believe the Earth was pelted by asteroids billions of years ago, and not only did these rocks bring water, they also carried the necessary molecules needed to kickstart the chemical reactions that led to amino acids and life. Now we have a better understanding of where some of these essential molecules came from.
“Amino acids are essential building blocks of life on Earth, yet we still have a lot to learn about how they first formed in our Solar System," said Beth Lymer, co-author of the paper and a PhD student at York University.
"The more variables that we can constrain, such as temperature and pH, allows us to better understand the synthesis and evolution of these very important molecules into what we now know as biotic life on Earth."
“We know water was abundant in the early solar system," Lee White, lead author of the study and a postdoctoral researcher at the ROM, added. “But there is very little direct evidence of the chemistry or acidity of these liquids, even though they would have been critical to the early formation and evolution of amino acids and, eventually, microbial life."
The latest analysis of the Tagish Lake rock helped eggheads answer some of those questions. For example, the acidity level of the early Solar System was low, and liquids were kept at around 80 degrees Celsius.
The team hopes to piece together a more detailed history of the system, and how life emerged on Earth, by studying asteroid samples retrieved from space. “Atom probe tomography gives us an opportunity to make fantastic discoveries on bits of material a thousand times thinner than a human hair," said White.
"Space missions are limited to bringing back tiny amounts of material, meaning these techniques will be critical to allowing us to understand more about the Solar System while also preserving material for future generations." ®
Sponsored: Ransomware has gone nuclear | 0.83223 | 3.582363 |
Since historic times, we have wondered where we came from and where life originated. As it became apparent that the Earth was just one planet orbiting the Sun, that the Sun was just one star among ∼1011 in our galaxy, and that the Galaxy itself was only one such object among ∼1011 similar systems populating the Universe out to a cosmic horizon, with perhaps countless more lying beyond, it became clear that life on other planets, near some other star, in some other galaxy was possible. The cosmological principle also makes this idea philosophically attractive. It would suggest that life is some general state of matter that prevails throughout the Universe. The probability of finding some form of life, however primitive, on other planets either within the Solar System or around nearby stars seems very high from this point of view. Nevertheless, we are unable to predict where life should exist, mainly because we do not yet understand the thermodynamics of living organisms and what different forms life may take.
As we know, things to be in equilibrium they should follow some permitted rules. Likewise, thermodynamics distinguishes between three types of systems. Isolated systems exchange neither energy nor matter with their surroundings. Closed systems exchange energy but not matter, and open systems exchange both matter and energy with the surroundings. Biological systems are always open, but in carrying out some of their functions, they may act as closed systems. Biological processes also exhibit a well-defined time dependence. Some physical processes could take place equally well whether time runs forward or backward. If we viewed a film of a clock’s pendulum, we would not be sure whether the film was running forward or back. Only if the film also showed the ratchet mechanism that advances the hands of the clock, would we be able to tell whether it was running in the right direction. The pendulum motion is reversible but the action of a ratchet is an irreversible process. Biological processes are invariably irreversible. In an irreversible process, entropy, a measure of disorder, always increases. If a cool interstellar grain absorbs visible starlight and re-emits the radiation thermally it does so by giving off a large number of low-energy photons.
The Universe is fundamentally biological. Even the Urey-Miller experiment that simulated the theorized early pre-life conditions on Earth, and produced amino acids, suggests this. The ammonia used was obtained by a process involving hydrogen of bio-origin, and the methane was also biological in origin. Non-biological catalysts would be poisoned almost instantaneously by sulfur gases under pre-life conditions. What this means is that most of the material in interstellar grains must be organic or life itself would have been impossible. The spectrum for all grains along the line of sight from the galactic center to the Earth is very much like that of dry bacteria. Either the grains are bacteria or are organic grains in proportions like bacteria (amino acids, nucleic acids, lipids and polysaccharides). Therefore, both theoretically and observationally, organic constituents fit the observations. Organic materials or bacteria would easily align in magnetic fields, and could produce superconducting surfaces that would generate filaments. Organic materials or bacteria could more easily produce the variety of objects in the Universe than inorganic or non-biological materials. As with so much of its constituents, the Universe itself is fundamentally biological. In fact, so much is this the case that life constitutes a physical law; it had to arise, it was an inevitable complexity of the real world is even more extraordinary with a hierarchy of living things.
Life result of the laws of physics as they exist. Moreover, the evidence indicates that the variety and permeates all of space, it is built into the very substance of the Universe, and has even brought about its own self-consciousness we humans. Yet, we have done little, in the scientific realm, to ask one ‘open’ question: Why? And the reason is that most scientists are afraid to admit that the Universe is purposeful and fundamentally biological. If electromagnetism did not exist then there would be no atoms, no chemistry, no life, and no heat and light from the Sun. If there were no strong force then nuclei would not have formed, and therefore, nothing would be. Likewise, if the weak force and gravity did not exist, then you would not be reading this, nor would any form of life be here
Yet, these four very different forces (and no others), each vital to all of the complex structures that make up the Universe, are so fine-tuned that they all combine to make a single super-force. Granted that we do not specifically know how to search for exotic forms of life, could we not find indications of extraterrestrial life in a form familiar on Earth? All terrestrial living matter contains organic molecules of some complexity proteins and nucleic acids, for example and we might expect to find either traces of such molecules or at least of their decay products. We know of two quite distinct locations in which complex molecules are found. There may be many more. First, observations of interstellar molecules by means of their microwave spectra have revealed the existence of such organic molecules as hydrogen cyanide, methyl alcohol, formaldehyde, and formic acid. Larger molecules, such as the sugar glycol- aldehyde, CH2OHCHO, have also been found to be quite prevalent in interstellar space. Infrared observations similarly have shown the existence of the even larger, polycyclic aromatic hydrocarbon molecules.
Choudhuri A. R, Astrophysics for Physicists, Cambridge University Press (2010)
Gagnon, E. et al. Soft X-ray-driven femto-second molecular Dynamic. | 0.833959 | 3.75974 |
The universe is expanding much faster than scientists predicted, and nobody knows why.
A team of researchers have confirmed this dilemma with data gathered using a new telescope technology that relies on shape-shifting mirrors. According to their study, which was published last month in the Monthly Notices of the Royal Astronomical Society, precise measurements of the rate at which the universe is expanding don't match the standard model that scientists have been using for decades.
"Therein lies the crisis in cosmology," Chris Fassnacht, an astrophysicist and co-author of the study, said in a press release.
Other studies published earlier this year reached similar conclusions.
"This mismatch has been growing and has now reached a point that is really impossible to dismiss as a fluke. This disparity could not plausibly occur just by chance," Adam Riess, the Nobel Prize-winning scientist behind a study that came out in April, said in a press release at the time.
He added that these findings "may be the most exciting development in cosmology in decades."
The mystery of the Hubble Constant
The universe is always getting bigger, stretching galaxies farther apart. For decades, scientists have attempted to measure how fast the universe is growing — a number called the Hubble Constant.
Researchers piece together the universe's history by studying the glow of radiation left over from the Big Bang about 13.8 billion years ago, called the cosmic microwave background (CMB).
When scientists study the CMB, they're looking both far into the distance and far into the past, since light travels at a constant speed. When we look at the sun, for example, what we see on Earth is the sun as it appeared 8 minutes ago, since it's about 8 light-minutes away. So when scientists look at objects far enough in the distance, they see them as they were at the beginning of the universe.
Based on those observations, scientists have found that after the Big Bang, the universe at first expanded very quickly. Then the expansion slowed as the gravity of dark matter — a mysterious, invisible force that makes up about 85% of all matter in the universe — pulled back.
But recently, they've run into a problem.
Measurements of the contemporary universe show it's expanding much faster than the standard model predicts. Riess' April study found that the universe is expanding 9% faster than predicted by calculations based on the CMB.
"This is not just two experiments disagreeing," he said at the time. "We are measuring something fundamentally different. One is a measurement of how fast the universe is expanding today, as we see it. The other is a prediction based on the physics of the early universe and on measurements of how fast it ought to be expanding. If these values don't agree, there becomes a very strong likelihood that we're missing something."
New technology confirmed the dilemma — but we're no closer to solving it
For the new study, the researchers used a cutting-edge mirror system at the Keck Observatory telescope in Hawaii. The device uses flexible mirrors that can correct for distortions caused by Earth's atmosphere and return extra-sharp images of objects in the sky.
The researchers pointed the telescope toward three systems of bright, highly active galaxies called quasars.
They studied the quasars using a process called gravitational lensing, which measures the way light gets bent as it travels around massive objects on its way toward Earth. A massive object (like a giant galaxy, say) bends light in a variety of directions, which allows scientists to see different, distorted versions of the same quasar from slightly different times in its past. They can then compare those various images to calculate how long a quasar's light takes to reach us and gather information about how much the universe expanded during that travel time.
Like the previous studies, the new results showed that the universe is expanding more rapidly than the standard model predicts. The researchers compared their results to data from the Hubble Space Telescope, and the findings were consistent.
"A difference in the Hubble constant between early and late-time universe means that there is something missing in our current standard model," astrophysicist Sherry Suyu said in a press release about the recent study. "For example, it could be exotic dark energy, or a new relativistic particle, or some other new physics yet to be discovered."
Scientists don't yet know what that missing piece could be. Some think the culprit could be dark energy, the term for the mysterious, unseen force that makes up about 68% of the universe. This energy could have sped up expansion as it pushed outward and overwhelmed the gravity of dark matter.
Fassnacht said he hopes scientists will continue to employ this new telescope technology to gather more precise data as they search for missing pieces in their understanding of the universe.
"Perhaps this will lead us to a more complete cosmological model of the universe," he said. | 0.813454 | 3.931234 |
July 18, 2019 report
Mass estimated for two binary pulsars
By performing timing observations, an international group of astronomers has measured the mass of two binary millisecond pulsars designated PSR J1949+3106 and PSR J1950+2414. The results could be essential in order to unveil the evolutionary status of these two objects. The research is detailed in a paper published July 11 on arXiv.org.
Pulsars are highly magnetized rotating neutron stars that emit beams of electromagnetic radiation. The most rapidly rotating pulsars, with rotation periods below 30 milliseconds, are known as millisecond pulsars (MSPs).
Astronomers believe that MSPs are formed in binary systems when the initially more massive component turns into a neutron star that is then spun up due to accretion of matter from the secondary star. To date, more than a half of known MSPs have been found to have stellar companions.
Nearly 200 pulsars have been discovered by PALFA, a large-scale survey for radio pulsars at 1.4 GHz using the Arecibo 305-meter telescope and the ALFA multibeam receivers. Recently, a team of astronomers led by Weiwei Zhu of the Max Planck Institute for Radio Astronomy in Bonn, Germany, decided to take a closer look at two MSPs from this survey, namely PSR J1949+3106 and PSR J1950+2414, detected in 2012 and 2013 respectively. The main aim of the study was to measure the proper motions of these two systems more precisely and to measure masses of these objects and their companions.
"In this paper, we present the results of timing observations of PSRs J1949+3106 and J1950+2414, two binary millisecond pulsars discovered in data from the Arecibo ALFA pulsar survey (PALFA)," the astronomers wrote in the paper.
Initial observations of the two pulsars made by Zhu's team confirmed that with adequate timing data, it could be possible to perform accurate mass measurements. By analyzing the dataset from Arecibo Observatory and from the North American Nanohertz Observatory for Gravitational Waves (NANOGrav), the astronomers were able to conduct precise calculations of proper motions of both pulsars, what resulted in uncovering the masses of the two systems.
According to the paper, the pulsar PSR J1949+3106 was found to have a mass of about 1.34 solar masses, while its companion has an estimated mass of approximately 0.81 solar masses. The observations revealed that PSR J1950+2414 is more massive than PSR J1949+3106, which has a mass at a level of around 1.5 solar masses. However, its companion turned out to have a relatively low mass—only about 0.28 solar masses.
The derived masses, together with calculations of proper motions, allowed the team to draw initial conclusions regarding the evolutionary history of both objects.
"PSR J1949+3106 is likely the product of a low-kick supernova; PSR J1950+2414 is a member of a new class of eccentric millisecond pulsar binaries with an unknown formation mechanism," the researchers concluded.
© 2019 Science X Network | 0.890061 | 3.805723 |
Scientists accurately quantify dust around planets in search for life
(Phys.org)—A new study from the Keck Interferometer, a former NASA project that combined the power of the twin W. M. Keck Observatory telescopes atop Mauna Kea, Hawaii, has brought exciting news to planet hunters. After surveying nearly 50 stars from 2008 to 2011, scientists have been able to determine with remarkable precision how much dust is around distant stars – a big step closer into finding planets than might harbor life. The discovery is being published in the Astrophysical Journal online, on December 8th.
"This was really a mathematical tour de force," said Peter Wizinowich, Interferometer Project Manager for Keck Observatory. "This team did something that we seldom see in terms of using all the available statistical techniques to evaluate the combined data set. They were able to dramatically reduce all the error bars, by a factor of 10, to really understand the amount of dust around these systems."
The Keck Interferometer was built to seek out this dust, and to ultimately help select targets for future NASA Earth-like planet-finding missions.
Like planets, dust near a star is hard to see. Interferometry is a high-resolution imaging technique that can be used to block out a star's light, making the region easier to observe. Light waves from the precise location of a star, collected separately by the twin 10-meter Keck Observatory telescopes, are combined and canceled out in a process called nulling.
"If you don't turn off the star, you are blinded and can't see dust or planets," said co-author Rafael Millan-Gabet of NASA's exoplanet Science Institute at the California Institute of Technology in Pasadena, California, who led the Keck Interferometer's science operations system.
"Dust is a double-edged sword when it comes to imaging distant planets," explained Bertrand Mennesson, lead author of the study who works at NASA's Jet Propulsion Laboratory, Pasadena, California. "The presence of dust is a signpost for the planet formation process, but too much dust can block our view." Mennesson has been involved in the Keck Interferometer project since its inception more than 10 years ago, both as a scientist and as the optics lead for one of its instruments.
"Using the two Keck telescopes in concert and interfering their light beams, it is possible to distinguish astronomical objects much closer to each other than when using a single Keck telescope," Mennesson said. "However, there is an additional difficulty when searching for warm dust in the immediate stellar environment: it generally contributes very little emission compared to the star, and that is when nulling interferometry comes into play."
In addition to requiring high performance from a large number of hardware and software subsystems, the nuller mode requires them to work smoothly together as a single, integrated system, according to Mark Colavita, the Keck Interferometer System Architect. "The nulling mode of the interferometer uses starlight across a wide range of wavelengths, including visible light for the adaptive optics to correct the telescope wave-fronts, near-infrared light to stabilize the path-lengths, and mid-infrared light for the nulling science measurements."
Ground- and space-based telescopes have already captured images of exoplanets, or planets orbiting stars beyond our sun. These early images, which show giant planets in cool orbits far from the glow of their stars, represent a huge technological leap. The glare from stars can overwhelm the light of planets, like a firefly buzzing across the sun. So, researchers have developed complex instruments to block the starlight, allowing information about a planet's shine to be obtained.
The next challenge is to image smaller planets in the "habitable" zone around stars where possible life-bearing Earth-like planets outside the solar system could reside. Such a lofty goal may take decades, but researchers are already on the path to get there, developing new instruments and analyzing the dust kicked up around stars to better understand how to snap crisp planetary portraits. Scientists want to find out: Which stars have the most dust? And how dusty are the habitable zones of sun-like stars?
In the latest study, nearly 50 mature, sun-like stars were analyzed with high precision to search for warm, room-temperature dust in their habitable zones. Roughly half of the stars selected for the study had previously shown no signs of cool dust circling in their outer reaches. This outer dust is easier to see than the inner, warm dust due to its greater distance from the star. Of this first group of stars, none were found to host the warm dust, making them good targets for planet imaging, and a good indication that other relatively dust-free stars are out there.
The other stars in the study were already known to have significant amounts of distant cold dust orbiting them. In this group, many of the stars were found to also have the room-temperature dust. This is the first time a link between the cold and warm dust has been established. In other words, if a star is observed to have a cold belt of dust, astronomers can make an educated guess that its warm habitable zone is also riddled with dust, making it a poor target for imaging smaller planets in the 'habitable zone' around stars, or exo-Earths.
"We want to avoid planets that are buried in dust," said Mennesson.
Like a busy construction site, the process of building planets is messy. It's common for young, developing star systems to be covered in dust. Proto-planets collide, scattering dust. But eventually, the chaos settles and the dust clears – except in some older stars. Why are these mature stars still laden with warm dust in their habitable zones?
The newfound link between cold and warm dust belts helps answer this question.
"The outer belt is somehow feeding material into the inner warm belt," said Geoff Bryden of JPL, a co-author of the study. "This transport of material could be accomplished as dust smoothly flows inward, or there could be larger cometary bodies thrown directly into the inner system."
The Keck Interferometer began construction in 1997, and finished its mission in 2012. It was developed by JPL, the Keck Observatory and the NASA Exoplanet Science Institute at Caltech. It was funded by NASA as a part of the Exoplanet Exploration Program with telescope and instrument operations managed by the W. M. Keck Observatory. | 0.810536 | 3.761998 |
From: European Space Agency
Posted: Wednesday, April 8, 2009
ESA's spaceborne X-ray observatory, XMM-Newton, has carried out an exclusive observation of the galaxy Messier 82, for the '100 Hours of Astronomy' cornerstone project for the International Year of Astronomy 2009.
The observatory was featured in the 'Around the World in 80 Telescopes' live webcast last week. This European space telescope has been studying the sky in X-ray, optical and ultraviolet wavelengths simultaneously, since its launch in December 1999.
The image is composed of several different XMM-Newton observations of Messier 82, adding up to 52.5 hours of observing time in total. The observations were carried out in X-ray, ultraviolet and visible wavelengths and include the special observation for the International Year of Astronomy 2009.
Messier 82 has several names including: M82, the Cigar Galaxy and NGC 3034. Located in the constellation Ursa Major at a distance of about 12 million light-years, it is the nearest and one of the most active starburst galaxies, i.e. it shows an exceptionally high rate of star formation. M82 is interacting gravitationally with its neighbour, the spiral galaxy Messier 81, which is most probably the cause for the violent starburst activity in the region around its centre, or the circumnuclear region.
The active star formation taking place in its interior and its effect on the gas and dust in its interstellar medium can be observed very well from Earth. This makes M82 is one of the best-studied galaxies in the sky.
The optical, ultraviolet and X-ray images from which this image has been derived are visible on the panels to the left and right of the image. The emission at different wavelengths is colour-coded as seen in each figure.
The optical and ultraviolet images show the very bright starry disc of the galaxy with striking dust lanes. The central image shows plumes of hot gas glowing in X-rays bursting out of the galactic disc (in blue). This results from very intense bursts of star formation in the circumnuclear region.
The last X-ray and ultraviolet observation of this galaxy was carried out on 3 April for the 100 Hours of Astronomy project. This last observation will also be made available for a scientific project led by Dr Feng from the University of Iowa, US.
// end // | 0.860389 | 3.521023 |
Every second, intense beams of maser emission (like laser emission but at radio frequencies) arrive on Earth from clouds of water vapor orbiting supermassive black holes (SMBHs), millions to billions of times the mass of the Sun, at centers of galaxies hundreds of millions of light years away. Ingyin Zaw, assistant professor of Physics at NYU Abu Dhabi, is using the largest and best radio telescopes in both the Northern and Southern hemispheres to tease out information from these maser systems in the attempt to unravel the nature and behavior of their host SMBHs.
Although SMBHs are only a small fraction of the total mass of the galaxies they inhabit, their growth and evolution are intimately linked with that of their host galaxies across cosmic time. A key in regulating this relationship is the process of accretion — how gas and dust from the galaxy falls into the SMBH — and outflows — material that is driven from the vicinity of the SMBH. Both accretion and outflows influence physical processes, like star formation, in the host galaxy.
Water masers occupy a unique location within a few light months to a few light years of the SMBH. They are in a region where the gravity of the SMBH dominates over that of the galaxy. From their location and motion, many properties of the SMBH and surrounding material can be deduced, including the mass of the SMBH, the geometry and temperature of the material around the SMBH, the shape of outflows, and the distance to the host galaxy.
"I'm amazed at how well we can study objects so far away," said the Burmese-born, Harvard-educated Zaw. The maser emission, up to hundreds of millions times weaker than the average TV signal, is discovered by large single-dish telescopes, approximately 100-meter versions of rooftop satellite dishes. Then, using very long baseline interferometry — a group of telescopes that spread out over the Earth but act as one — astronomers are able to image the individual maser clumps. The resolution produced by this method is the equivalent on Earth of being able to see the face of a person standing on the moon.
In addition, Zaw wants to combine this information with data of light emitted at other frequencies, since different physical processes at different locations near the SMBH emit at different frequencies. This way, she will be able to disentangle the complex physical conditions near the SMBH, then build models and compare them to theoretical predictions.
I'm amazed at how well we can study objects so far away.
Zaw was in Australia in April 2014 to work with the Southern Hemisphere's largest radio telescope, the 70-meter Tidbinbilla antenna, a part of NASA's Deep Space Network, near Canberra. She and Lincoln Greenhill, a senior researcher at the Harvard-Smithsonian Center for Astrophysics, are co-principal investigators on the Tidbinbilla AGN Maser Survey, known as TAMS. The seven-person team, which spans three continents, comprises Zaw's postdoctoral researcher Aquib Moin and collaborators at Australian National University's Jet Propulsion Laboratory and the Canberra Deep Space Communication Complex. The arrangement is ideal for splitting up observing sessions that can be scheduled for any time, day or night, said Zaw. She is also excited to supervise research projects of NYUAD students using the data from the TAMS project.
Zaw and two other NYUAD Physics faculty, Visiting Professor of Practice of Physics Mallory Roberts and Assistant Professor of Physics Joseph Gelfand, are also working on a partnership with the National Radio Astronomy Observatory's 100-meter Green Bank Telescope in Green Bank, West Virginia, to conduct maser and pulsar observations.
The Australian project has been allotted 1,200 hours of telescope time to be spread out over the next few years. During her April 2014 trip, Zaw calibrated the instrument and prepared to begin the first year of study, designated as a pilot phase. "We need cold dry nights," she said, and the Australian winter fits that requirement.
"When it's all set up," she added, her tone revealing her enthusiasm for the project, "I'll be able to sit in my office at NYU Abu Dhabi and control the telescope remotely. It is truly a privilege."
Zaw cites a quote from the poem "Planetarium" by Adrienne Rich that inspires her:
I am bombarded yet I stand
I have been standing all my life in the
direct path of a battery of signals
the most accurately transmitted most
untranslatable language in the universe
I am an instrument in the shape
of a woman trying to translate pulsations
into images for the relief of the body
and the reconstruction of the mind.
This article originally appeared in NYUAD's 2013-14 Research Report (13MB PDF). | 0.882054 | 4.133022 |
Chandra X-Ray view of Mira AB; a red giant star probably orbiting a white dwarf. Image credit: Chandra. Click to enlarge.
For the first time an X-ray image of a pair of interacting stars has been made by NASA’s Chandra X-ray Observatory. The ability to distinguish between the interacting stars – one a highly evolved giant star and the other likely a white dwarf – allowed a team of scientists to observe an X-ray outburst from the giant star and find evidence that a bridge of hot matter is streaming between the two stars.
“Before this observation it was assumed that all the X-rays came from a hot disk surrounding a white dwarf, so the detection of an X-ray outburst from the giant star came as a surprise,” said Margarita Karovska of the Harvard-Smithsonian Center for Astrophysics in Cambridge, Mass., and lead author article in the latest Astrophysical Journal Letters describing this work. An ultraviolet image made by the Hubble Space Telescope was a key to identifying the location of the X-ray outburst with the giant star.
X-ray studies of this system, called Mira AB, may also provide better understanding of interactions between other binary systems consisting of a “normal” star and a collapsed star such as a white dwarf, black hole or a neutron star, where the stellar objects and gas flow cannot be distinguished in an image.
The separation of the X-rays from the giant star and the white dwarf was made possible by the superb angular resolution of Chandra, and the relative proximity of the star system at about 420 light years from Earth. The stars in Mira AB are about 6.5 billion miles apart, or almost twice the distance of Pluto from the Sun.
Mira A (Mira) was named “The Wonderful” star in the 17th century because its brightness was observed to wax and wane over a period of about 330 days. Because it is in the advanced, red giant phase of a star’s life, it has swollen to about 600 times that of the Sun and it is pulsating. Mira A is now approaching the stage where its nuclear fuel supply will be exhausted, and it will collapse to become a white dwarf.
The internal turmoil in Mira A could create magnetic disturbances in the upper atmosphere of the star and lead to the observed X-ray outbursts, as well as the rapid loss of material from the star in a blustery, strong, stellar wind. Some of the gas and dust escaping from Mira A is captured by its companion Mira B.
In stark contrast to Mira A, Mira B is thought to be a white dwarf star about the size of the Earth. Some of the material in the wind from Mira A is captured in an accretion disk around Mira B, where collisions between rapidly moving particles produce X-rays.
One of the more intriguing aspects of the observations of Mira AB at both X-ray and ultraviolet wavelengths is the evidence for a faint bridge of material joining the two stars. The existence of a bridge would indicate that, in addition to capturing material from the stellar wind, Mira B is also pulling material directly off Mira A into the accretion disk.
Chandra observed Mira with its Advanced CCD Imaging Spectrometer on December 6, 2003 for about 19 hours. NASA’s Marshall Space Flight Center, Huntsville, Ala., manages the Chandra program for NASA’s Science Mission Directorate, Washington. Northrop Grumman of Redondo Beach, Calif., was the prime development contractor for the observatory. The Smithsonian Astrophysical Observatory controls science and flight operations from the Chandra X-ray Center in Cambridge, Mass.
Additional information and images are available at:
Original Source: Chandra News Release | 0.805784 | 3.994314 |
NASA wants to develop a giant radio telescope that will fly in space. The telescope will operate through the six small satellites which will work concurrently with each other. This mission name is SunRISE (Sun Radio Interference Interferometer Space Experiment), and there are plans for launching it in July 2023 or earlier than that year. The main Aim of SunRise is to help the scientist to understand the compound relationship between the sun and other phenomena around the earth which are looks so dangerous. The common name given to the hazardous space phenomena is the space weather.
The SUNRISE mission comes when there is a burst in solar science, and there is more emphasis on the mission, which will incorporate space weather forecast plans for spaceflight to go past low Earth orbit for humans. NASA Heliophysics Division director, Nicky Fox in a statement he said that they are happy to have an additional mission to the spacecraft fleet to help them understand the sun in totality and its influence on the environment among the planets. He added many people to know about the sun eruptions with the weather events in the space. The purpose is to mitigate the effects of the space weather on the spacecraft and astronauts.
Some of the scientists watched the sun fling energy with the materials towards the earth in the outburst. The same scientists have seen the impacts of movements on the satellites moving on the orbit, particularly on those that contain communication and instruments for navigation. The awkward moment is that the scientists have no knowledge of nitty-gritty details and the connection between the space weather phenomena and the solar outburst that will help them to forecast the space weather.
The SunRISE mission costs 63 million U.S dollars and will help to bridge the difference. The six telescopes that are in the purpose will study the waves ejected from the sun during the solar particle outburst—the mission target Coronal mass ejections which have the capacity to through a large amount of plasma. The liquid of the plasma charged particles makes the sun to function across the solar system.
The satellite with the size of the toaster-sized spreads out across for about 10 kilometers and orbits the earth at 22,000 miles altitude. The earth orbit keeps the SUnRISE missions above the ionosphere of the earth that blocks radio waves of objects with such high speed from entering into the earth. | 0.857851 | 3.122 |
Astronomy has always been a “big data science”. Astronomy is an observational science: we just have to wait, watch, see and interpret what happens somewhere on the sky. We can’t control it, we can’t plan it, we can just observe in any kind of radiation imaginable and hope that we understand enough of the physics that governs the celestial objects to make sense of it. In recent years, more and more tools that are so very common in the world of data science have also penetrated the field of astrophysics. Where observational astronomy has largely been a hypothesis driven field, data driven “serendipitous” discoveries have become more commonplace in the last decade, and in fact entire surveys and instruments are now designed to be mostly effective through statistics, rather than through technology (even though it is still stat of the art!).
In order to illustrate how astronomy is leading the revolutions in data streams, this infographic was used by the organizers of a hackathon I went to nearing the end of April:
The Square Kilometer Array will be a gigantic radio telescope that is going to result in a humongous 160 TB/s rate of data coming out of antennas. This needs to be managed and analysed on the fly somehow. At ASTRON a hackathon was organized to bring together a few dozen people from academia and industry to work on projects that can prepare astronomers for the immense data rates they will face in just a few years.
As usual, and for the better, smaller working groups split up and started working on different projects. Very different projects, in fact. Here, I will focus on the one I have worked on, but by searching for the right hash tag on twitter, I’m sure you can find info on many more of them!
We jumped on two large public data sets on galaxies and AGN (Active Galactic Nuclei: galaxies with a supermassive black hole in the center that is actively growing). One of them was a very large data set with millions of galaxies, but not very many properties of every galaxy (from SDSS), the other, out of which the coolest result (in my own, not very humble opinion) was distilled was from the ZFOURGE survey. In that data set, there are “only” just under 400k galaxies, but there were very many properties known, such as brightnesses through 39 filters, derived properties such as the total mass in stars in them, the rate at which stars were formed, as well as an indicator whether or not the galaxies have an active nucleus, as determined from their properties in X-rays, radio, or infrared.
I decided to try something simple and take the full photometric set of columns, so the brightness of the objects in many many wavelengths as well as a measure of their distance to us into account and do some unsupervised machine learning on that data set. The data set had 45 dimensions, so an obvious first choice was to do some dimensionality reduction on it. I played with PCA and my favorite bit of magic: t-SNE. A dimensionality reduction algorithm like that is supposed to reveal if any substructure in the data is present. In short, it tends to conserve local structure and screw up global structure just enough to give a rather clear representation of any clumping in the original high dimensional data set, in two dimensions (or more, if you want, but two is easiest to visualize). I made this plot without putting in any knowledge about which galaxies are AGN, but colored the AGNs and made them a bit bigger, just to see where they would end up:
To me, it was absolutely astonishing to see how that simple first try came up with something that seems too good to be true. The AGN cluster within clumps that were identified without any knowledge of the galaxies having an active nucleus or not. Many galaxies in there are not classified as AGN. Is that because they were simply not observed at the right wavelengths? Or are they observed but would their flux be just below detectable levels? Are the few AGN far away from the rest possible mis-classifications? Enough questions to follow up!
On the fly, we needed to solve some pretty nasty problems in order to get to this point, and that’s exactly what makes these projects so much fun to do. In the data set, there were a lot of null values, no observed flux in some filters. This could either mean that the observatory that was supposed to measure that flux didn’t point in the direction of the objects (yet), or that there was no detected flux above the noise. Working with cells that have no number at all or only upper limits on the brightness in some of the features that were fed to the machine learning algorithm is something most ML models are not very good at. We made some simple approximations and informed guesses about what numbers to impute into the data set. Did that have any influence on the results? Likely! Hard to test though… For me, this has sprung a new investigation on how to deal with ML on data with upper or lower limits on some of the features. I might report on that some time in the future!
The hackathon was a huge success. It is a lot of fun to gather with people with a lot of different backgrounds to just sit together for two days and in fact get to useful results, and interesting questions for follow-up. Many of the projects had either some semi-finished product, or leads into interesting further investigation that wouldn’t fit in two days. All the data is available online and all code is uploaded to github. Open science for the win! | 0.839121 | 3.672971 |
1,000,000,000 years ago is the date of the actual beginning of Urantia history. The planet had attained approximately its present size. And about this time it was placed upon the physical registries of Nebadon and given its name, Urantia.
The atmosphere, together with incessant moisture precipitation, facilitated the cooling of the earth’s crust. Volcanic action early equalized internal-heat pressure and crustal contraction; and as volcanoes rapidly decreased, earthquakes made their appearance as this epoch of crustal cooling and adjustment progressed.
The real geologic history of Urantia begins with the cooling of the earth’s crust sufficiently to cause the formation of the first ocean. Water-vapor condensation on the cooling surface of the earth, once begun, continued until it was virtually complete. By the end of this period the ocean was world-wide, covering the entire planet to an average depth of over one mile. The tides were then in play much as they are now observed, but this primitive ocean was not salty; it was practically a fresh-water covering for the world. In those days, most of the chlorine was combined with various metals, but there was enough, in union with hydrogen, to render this water faintly acid.
At the opening of this faraway era, Urantia should be envisaged as a water-bound planet. Later on, deeper and hence denser lava flows came out upon the bottom of the present Pacific Ocean, and this part of the water-covered surface became considerably depressed. The first continental land mass emerged from the world ocean in compensatory adjustment of the equilibrium of the gradually thickening earth’s crust.
950,000,000 years ago Urantia presents the picture of one great continent of land and one large body of water, the Pacific Ocean. Volcanoes are still widespread and earthquakes are both frequent and severe. Meteors continue to bombard the earth, but they are diminishing in both frequency and size. The atmosphere is clearing up, but the amount of carbon dioxide continues large. The earth’s crust is gradually stabilizing.
It was at about this time that Urantia was assigned to the system of Satania for planetary administration and was placed on the life registry of Norlatiadek. Then began the administrative recognition of the small and insignificant sphere which was destined to be the planet whereon Michael would subsequently engage in the stupendous undertaking of mortal bestowal, would participate in those experiences which have since caused Urantia to become locally known as the “world of the cross.”
900,000,000 years ago witnessed the arrival on Urantia of the first Satania scouting party sent out from Jerusem to examine the planet and make a report on its adaptation for a life-experiment station. This commission consisted of twenty-four members, embracing Life Carriers, Lanonandek Sons, Melchizedeks, seraphim, and other orders of celestial life having to do with the early days of planetary organization and administration.
After making a painstaking survey of the planet, this commission returned to Jerusem and reported favorably to the System Sovereign, recommending that Urantia be placed on the life-experiment registry. Your world was accordingly registered on Jerusem as a decimal planet, and the Life Carriers were notified that they would be granted permission to institute new patterns of mechanical, chemical, and electrical mobilization at the time of their subsequent arrival with life transplantation and implantation mandates.
In due course arrangements for the planetary occupation were completed by the mixed commission of twelve on Jerusem and approved by the planetary commission of seventy on Edentia. These plans, proposed by the advisory counselors of the Life Carriers, were finally accepted on Salvington. Soon thereafter the Nebadon broadcasts carried the announcement that Urantia would become the stage whereon the Life Carriers would execute their sixtieth Satania experiment designed to amplify and improve the Satania type of the Nebadon life patterns.
Shortly after Urantia was first recognized on the universe broadcasts to all Nebadon, it was accorded full universe status. Soon thereafter it was registered in the records of the minor and the major sector headquarters planets of the superuniverse; and before this age was over, Urantia had found entry on the planetary-life registry of Uversa.
This entire age was characterized by frequent and violent storms. The early crust of the earth was in a state of continual flux. Surface cooling alternated with immense lava flows. Nowhere can there be found on the surface of the world anything of this original planetary crust. It has all been mixed up too many times with extruding lavas of deep origins and admixed with subsequent deposits of the early world-wide ocean.
Nowhere on the surface of the world will there be found more of the modified remnants of these ancient preocean rocks than in northeastern Canada around Hudson Bay. This extensive granite elevation is composed of stone belonging to the preoceanic ages. These rock layers have been heated, bent, twisted, upcrumpled, and again and again have they passed through these distorting metamorphic experiences.
Throughout the oceanic ages, enormous layers of fossil-free stratified stone were deposited on this ancient ocean bottom. (Limestone can form as a result of chemical precipitation; not all of the older limestone was produced by marine-life deposition.) In none of these ancient rock formations will there be found evidences of life; they contain no fossils unless, by some chance, later deposits of the water ages have become mixed with these older prelife layers.
The earth’s early crust was highly unstable, but mountains were not in process of formation. The planet contracted under gravity pressure as it formed. Mountains are not the result of the collapse of the cooling crust of a contracting sphere; they appear later on as a result of the action of rain, gravity, and erosion.
The continental land mass of this era increased until it covered almost ten per cent of the earth’s surface. Severe earthquakes did not begin until the continental mass of land emerged well above the water. When they once began, they increased in frequency and severity for ages. For millions upon millions of years earthquakes have diminished, but Urantia still has an average of fifteen daily.
850,000,000 years ago the first real epoch of the stabilization of the earth’s crust began. Most of the heavier metals had settled down toward the center of the globe; the cooling crust had ceased to cave in on such an extensive scale as in former ages. There was established a better balance between the land extrusion and the heavier ocean bed. The flow of the subcrustal lava bed became well-nigh world-wide, and this compensated and stabilized the fluctuations due to cooling, contracting, and superficial shifting.
Volcanic eruptions and earthquakes continued to diminish in frequency and severity. The atmosphere was clearing of volcanic gases and water vapor, but the percentage of carbon dioxide was still high.
Electric disturbances in the air and in the earth were also decreasing. The lava flows had brought to the surface a mixture of elements which diversified the crust and better insulated the planet from certain space-energies. And all of this did much to facilitate the control of terrestrial energy and to regulate its flow, as is disclosed by the functioning of the magnetic poles.
800,000,000 years ago witnessed the inauguration of the first great land epoch, the age of increased continental emergence.
Since the condensation of the earth’s hydrosphere, first into the world ocean and subsequently into the Pacific Ocean, this latter body of water should be visualized as then covering nine tenths of the earth’s surface. Meteors falling into the sea accumulated on the ocean bottom, and meteors are, generally speaking, composed of heavy materials. Those falling on the land were largely oxidized, subsequently worn down by erosion, and washed into the ocean basins. Thus the ocean bottom grew increasingly heavy, and added to this was the weight of a body of water at some places ten miles deep.
The increasing downthrust of the Pacific Ocean operated further to upthrust the continental land mass. Europe and Africa began to rise out of the Pacific depths along with those masses now called Australia, North and South America, and the continent of Antarctica, while the bed of the Pacific Ocean engaged in a further compensatory sinking adjustment. By the end of this period almost one third of the earth’s surface consisted of land, all in one continental body.
With this increase in land elevation the first climatic differences of the planet appeared. Land elevation, cosmic clouds, and oceanic influences are the chief factors in climatic fluctuation. The backbone of the Asiatic land mass reached a height of almost nine miles at the time of the maximum land emergence. Had there been much moisture in the air hovering over these highly elevated regions, enormous ice blankets would have formed; the ice age would have arrived long before it did. It was several hundred millions of years before so much land again appeared above water.
750,000,000 years ago the first breaks in the continental land mass began as the great north-and-south cracking, which later admitted the ocean waters and prepared the way for the westward drift of the continents of North and South America, including Greenland. The long east-and-west cleavage separated Africa from Europe and severed the land masses of Australia, the Pacific Islands, and Antarctica from the Asiatic continent.
700,000,000 years ago Urantia was approaching the ripening of conditions suitable for the support of life. The continental land drift continued; increasingly the ocean penetrated the land as long fingerlike seas providing those shallow waters and sheltered bays which are so suitable as a habitat for marine life.
650,000,000 years ago witnessed the further separation of the land masses and, in consequence, a further extension of the continental seas. And these waters were rapidly attaining that degree of saltiness which was essential to Urantia life.
It was these seas and their successors that laid down the life records of Urantia, as subsequently discovered in well-preserved stone pages, volume upon volume, as era succeeded era and age grew upon age. These inland seas of olden times were truly the cradle of evolution.
[Presented by a Life Carrier, a member of the original Urantia Corps and now a resident observer.] | 0.851608 | 3.264467 |
Greetings, fellow Stargazers! Have you been enjoying the rain? Then keep your eyes open for a “celestial shower” as meteoritic activity picks up over the next few nights, culminating in the peak of the Ophiuchid meteor Saturday night through Sunday morning. While you’re out relaxing, be sure to spare some time for lunacy and take a look some interesting features on the Moon. Need a test of your telescope’s resolving power? Then I “double dare” you to take on Gamma Virginis! Whenever you’re ready, I’ll see you in the back yard….
Friday, June 18, 2010 – Let’s begin the day by recognizing the 1799 birth on this date of William Lassell, telescope maker and discoverer of Triton (a moon of Neptune), and Ariel and Umbriel (satellites of Uranus). As often happens, great astronomers share birth dates, and this time it’s 187 years later for Allan Rex Sandage. A Bruce Medalist, Dr. Sandage is best known for his 1960 optical identification of a quasar, with his junior colleague, Thomas Matthews.
Our telescope lunar challenge tonight will be Hadley Rille. Find Mare Serenitatis and look for the break along its western shoreline that divides the Caucasus and Apennine mountain ranges. South of this break is the bright peak of Mons Hadley, which is of great interest for several reasons, so power up as much as possible.
Impressive Mons Hadley measures about 24 by 48 kilometers at its base and reaches up an incredible 4,572 meters. If volcanic activity had created it, Mons Hadley would be comparable to some of the very highest volcanically formed peaks on Earth, like Mount Shasta and Mount Rainer. South is the secondary peak, Mons Hadley Delta. It is home to the Apollo 15 landing site just a breath north of where it extends into the cove created by Palus Putredinus. Along this ridge line and smooth floor, look for a major fault line, winding its way across 120 kilometers of lunar surface; this is Hadley Rille. In places, the Rille spans 1,500 meters in width and drops to a depth of 300 meters below the surface. Believed to have been formed by volcanic activity 3.3 billion years ago, we can see the impact lower gravity has on this type of formation. Earthly lava channels are usually less than 10 kilometers long, and only around 100 meters wide. During the Apollo 15 mission, Hadley Rille was visited at a point where it was only 1.6 kilometers wide, still a considerable distance. Over a period of time, the Rille’s lava may have continued to flow through this area, yet it remains forever buried beneath years of regolith.
Saturday, June 19, 2010 – Tonight on the Moon we’ll be looking for another challenging feature and the craters that conjoin it—Stofler and Faraday. Located along the terminator to the south, crater Stofler was named for Dutch mathematician and astronomer Johan Stofler.
Consuming lunar landscape with an immense diameter of 126 kilometers, and dropping 2,760 meters below the surface, Stofler is a wonderland of small details in an eroded surrounding. Breaking its wall on the north is Fernelius, but sharing the southeastern boundary is Faraday. Named for English physicist and chemist Michael Faraday, this crater is more complex and deeper (4,090 meters) but far smaller in diameter (70 kilometers). Look for myriad smaller strikes that bind the two together!
When you’re done, let’s have a look at a delightful pair—Gamma Virginis (RA 12 41 41 Dec +01 26 54). Better knownas Porrima , this is one cool binary whose components are of almost equal spectral type and brightness. Discovered by Bradley and Pound in 1718, John Herschel was the first to predict this pair’s orbit in 1833, and stated that one day they would become inseparable to all but the very largest of telescopes—and he was right. In 1920 the A and B stars had reached their maximum separation, and during 2007 they were as close together as they ever can be. Observed as a single star in 1836 by William Herschel, its 171-year orbit puts Porrima in almost the same position now as it was when Sir William saw it!
Sunday, June 20, 2010 – In the predawn hours, we welcome the ‘‘shooting stars’’ as we pass through another portion of the Ophiuchid meteor stream. The radiant for this pass lies nearer Sagittarius, and the fall rate varies from 8 to 20 per hour, but the Ophiuchids can sometimes produce more than expected! Perhaps the sky acknowledges the 1966 passing of Georges Lemaitre on this date? Lemaitre researched cosmic rays and the three-body problem and in 1927 formulated the Big Bang theory using Einstein’s theories.
Are you ready to explore some more history? Then tonight have a look at the Moon and identify Alphonsus; it’s the centermost in a line of rings and looks much like the Theophilus, Cyrillus, and Catharina trio.
Alphonsus is a very old Class V crater, spans 118 kilometers in diameter, drops below the surface to about 2,730 meters, and contains a small central peak. Eugene Shoemaker had studied this partially flooded crater and found dark haloes on the floor. Again, this could be attributed to volcanism. Shoemaker believed they were maar volcanoes, and the haloes were dark ash. Power up and look closely at the central peak, for not only did Ranger 9 hard land just northeast, but this is the only area on the Moon where an astronomer has observed a change and backed up that observation with photographic proof.
On November 2, 1958, Nikolai Kozyrev long and arduous study of Alphonsus was about to be rewarded. Some two years earlier Dinsmore Alter had taken a series of photographs from the Mt. Wilson 60’’ reflector that showed hazy patches in this area that could not be accounted for. Night after night, Kozyrev continued to study at the Crimean Observatory, but with no success. During the process of guiding the scope for a spectrogram, the unbelievable happened—a cloud of gaseous molecules containing carbon had been captured! Selected as the last target for the Ranger series of photographic missions, Ranger 9 delivered 5,814 spectacular high-resolution images of this mysterious region before it crashed nearby. Capture it yourself tonight!
Until next time? Ask for the Moon… But keep on reaching for the stars!
This week’s awesome images are (in order of appearance): Dr. Alan Sandage courtesy of Dr. Sandage, Hadley Rille, courtesy of Wes Higgins, Stoffler and Faraday courtesy of Wes Higgins, Porrima – Palomar Observatory courtesy of Caltech, Georges Lemaitre and Albert Einstein (historical image), Ranger 9 Image of Alphonsus taken 3 minutes before impact courtesy of NASA, Alphonsus’ central peak taken 54 seconds before Ranger 9 impact courtesy of NASA. We thank you so much! | 0.911329 | 3.312115 |
M94 (mag 9.0) , a spiral galaxy in Canes Venatici will be well placed, high in the sky. It will reach its highest point in the sky at around midnight local time.
At a declination of +41°07', it is easiest to see from the northern hemisphere but cannot be seen from latitudes much south of 28°S.
From Ashburn, it will be visible all night. It will become visible around 20:42 (EDT) as the dusk sky fades, 40° above your north-eastern horizon. It will then reach its highest point in the sky at 01:11, 87° above your northern horizon. It will be lost to dawn twilight around 05:45, 38° above your north-western horizon.
At magnitude 8.2, M94 is quite faint, and certainly not visible to the naked eye, but can be viewed through a pair of binoculars or small telescope.
The position of M94 is as follows:
|Object||Right Ascension||Declination||Constellation||Magnitude||Angular Size|
The coordinates above are given in J2000.0.
|The sky on 04 April 2017|
7 days old
All times shown in EDT.
The circumstances of this event were computed using the DE405 planetary ephemeris published by the Jet Propulsion Laboratory (JPL).
This event was automatically generated by searching the ephemeris for planetary alignments which are of interest to amateur astronomers, and the text above was generated based on an estimate of your location. | 0.903643 | 3.161634 |
Concurrent observation of electromagnetic emission launches gravitational-wave multi-messenger astronomy.
August 17, 2017 saw a major breakthrough in astronomy, when gravitational waves from a pair of colliding neutron stars were detected for the first time by the US-based Laser Interferometer Gravitational-Wave Observatory (LIGO) and the Europe-based Virgo detector. The detection was confirmed by a large number of telescopes around the world that studied various forms of radiation from the merger, marking the beginning of gravitational wave multi-messenger astronomy.
More info: http://www.gw.iucaa.in/news/gw170817/
One Event – Two Breakthroughs!
17 August 2017 saw a major breakthrough in astronomy, when gravitational waves from a pair of colliding neutron stars were detected for the first time by the US-based Laser Interferometer Gravitational-Wave Observatory (LIGO) and the Europe-based Virgo detector. This happens to be the strongest gravitational-wave signal detected so far, owing to the relatively close location of about 130 million light-years from the earth and the signal duration in the detector band is much longer than what it is for black hole signals. The detection was also confirmed by a large number of telescopes around the world that studied various forms of radiation from the merger. This is a new milestone in the success saga of advanced gravitational wave detectors, which have announced the discoveries of four black hole mergers to date. The effort was recognised with the Nobel prize in physics this year.
Neutron stars are the smallest, densest stars known to exist and are formed when massive stars explode in supernovas. Typical neutron stars are heavier than the sun, but have a diameter of just about 20 kilometers: objects so dense that a teaspoon of neutron star material weighs more than Mount Everest. Scientists could track these neutron stars, weighing about 1.1 to 1.6 times the mass of the sun, for about 100 seconds as they spiraled towards each other in a final deadly dance and collided. These observations contain important clues about the nature of the dense matter that constitute these stars.
Let there be light
The collision created a flash of gamma rays that was detected by earth-orbiting satellites just two seconds after the gravitational waves. This is the first conclusive evidence that short gamma ray bursts, often seen by orbiting satellites, are indeed created by colliding neutron stars — something that had only been speculated for decades. The near-simultaneous arrival of gravitational waves and gamma rays from a source that is 130 million light years away confirms that gravitational waves indeed travel with the speed of light, as predicted by Einstein’s theory. These joint observations also provided scientists an independent way of measuring the expansion rate of the universe.
In the days that followed, astronomers pinpointed the source on the sky and studied it extensively in various forms of electromagnetic radiation, including X-ray, ultraviolet, optical, infrared, and radio waves. These joint observations clearly show that at least some short gamma-ray bursts, the energetic flashes of gamma rays, are generated by the merging of neutron stars — something that was only theorized before. These studies showed signatures of newly synthesized elements, confirming that such mergers are indeed the birthplaces of half of the elements heavier than iron – including most of the gold and platinum in the universe.
Indian scientists have made pioneering contributions to the gravitational-wave science over the last three decades. 40 scientists from 13 Indian institutions are part of the LIGO-Virgo discovery paper. Indian scientists contributed to the fundamental algorithms crucial to search for inspiraling binaries in noisy data from multiple detectors, in computing waveforms for these signals by solving Einstein’s equations, in separating astrophysical signals from numerous instrumental and environmental artefacts, in interpretation of joint gravitational-wave and gamma-ray observations, tests of Einstein’s theory and many other aspects of the data analysis. In addition, several Indian telescopes such as AstroSat, Giant Metrewave Radio Telescope (GMRT) and the Himalayan Chandra Telescope (HCT) participated in the search for electromagnetic flashes. The sensitive CZTI instrument on AstroSat helped narrow down the location of the gamma-ray flashes. HCT obtained optical images at locations of neutrinos detected by other telescopes at the same time as the burst, and showed that they were unrelated to the gravitational-wave trigger. GMRT played a key role in understanding jet physics and refining models of radio emission from the remnant formed by the merging neutron stars.
The Indian team in LIGO includes scientists from CMI Chennai, ICTS-TIFR Bangalore, IISER Kolkata, IISER Trivandrum, IIT Bombay, IIT Gandhinagar, IIT Hyderabad, IIT Madras, IPR Gandhinagar, IUCAA Pune, RRCAT Indore, TIFR Mumbai and UAIR Gandhinagar. Astronomers from IISER Pune, IIT Bombay, IUCAA Pune, TIFR Mumbai, PRL Ahmedabad, IIT Hyderabad, IIA Bangalore, NCRA-TIFR Pune, ARIES Nainital and IIST Trivandrum participated in the electromagnetic follow-up of this event using a variety of telescopes.
IUCAA scientists have made pioneering contributions to the gravitational-wave science over the last three decades. 11 researchers are part of the LIGO-Virgo discovery paper. They are Anirban Ain, Sukanta Bose, Sanjeev Dhurandhar, Bhooshan Gadre, Sharad Gaonkar, Sanjit Mitra, Nikhil Mukund, Abhishek Parida, Jayanti Prasad, Tarun Souradeep, Jishnu Suresh. They collaborated with other members in the LIGO Scientific Collaboration and contributed to the fundamental algorithms crucial to search for inspiraling binaries in noisy data from multiple detectors, in separating astrophysical signals from numerous instrumental and environmental artefacts, and in understanding the properties of neutron star matter.
IUCAA scientists were also instrumental in searching for electromagnetic emission from the binary. They include Dipankar Bhattacharya, Javed Rana, Gulab Dewangan, Ajay Vibhute and Rupak Roy. The sensitive CZTI instrument on AstroSat was used to help narrow down the location of the gamma-ray flash. AstroSat was launched in 2015 by the Indian Space Research Organisation. Additionally, Rana contributed to the finding of radio emission with the Very Large Array radio observatory in New Mexico and Roy contributed to follow up with the extended-Public ESO Spectroscopic Survey for Transient Objects (ePESSTO) in Chile.
The planned LIGO-India detector, to be funded by the Department of Atomic Energy (DAE) and the Department of Science & Technology (DST), will increase the sensitivity of the international gravitational-wave network and produce many fold improvement to the localisation of the sources. Astronomers will then be able to identify the exact location of the cosmic explosion a lot quicker, and study right from the first moments in every frequency band of the electromagnetic spectrum.
The LIGO-Virgo results are published today in the journal Physical Review Letters; additional papers from the LIGO and Virgo collaborations and the astronomical community have been either submitted or accepted for publication in various journals. A partial list of publications where IUCAA members are authors will be available at: www.gw.iucaa.in/news/gw170817
LIGO is funded by the NSF, and operated by Caltech and MIT, which conceived of LIGO and led the Initial and Advanced LIGO projects. Financial support for the Advanced LIGO project was led by the NSF with Germany (Max Planck Society), the U.K. (Science and Technology Facilities Council) and Australia (Australian Research Council) making significant commitments and contributions to the project. More than 1,200 scientists and some 100 institutions from around the world participate in the effort through the LIGO Scientific Collaboration, which includes the GEO Collaboration and the Australian collaboration OzGrav. Additional partners are listed at http://ligo.org/partners.php
The Virgo collaboration consists of more than 280 physicists and engineers belonging to 20 different European research groups: six from Centre National de la Recherche Scientifique (CNRS) in France; eight from the Istituto Nazionale di Fisica Nucleare (INFN) in Italy; two in the Netherlands with Nikhef; the MTA Wigner RCP in Hungary; the POLGRAW group in Poland; Spain with the University of Valencia; and the European Gravitational Observatory, EGO, the laboratory hosting the Virgo detector near Pisa in Italy, funded by CNRS, INFN, and Nikhef.
Sukanta Bose <[email protected]> Tel. +91 98198 63224
Dipankar Bhattacharya <[email protected]> Tel. +91 99236 97158
Sanjit Mitra <[email protected]>, Tel. +91 82750 67686
Tarun Souradeep <[email protected]>, Tel. +91 94226 44463
More information at: | 0.818644 | 3.907709 |
Radioactive carbon from nuclear bomb tests finds its way to deepest ocean trenches
A new study led by the Chinese Academy of Sciences in Guangzhou indicates that radioactive carbon-14 produced by above-ground nuclear weapons tests in the mid-20th century has been found in the muscle tissues of crustaceans in the deepest parts of the ocean. The presence of the nuclear isotopes in animals living up to seven mi (11 km) down shows that pollutants may be reaching the deep ocean much faster than previously thought.
Carbon 14 is a rare isotope of carbon that every living creature on Earth absorbs. It's produced in the Earth's atmosphere when cosmic ray neutrons strike nitrogen atoms in the upper atmosphere. The naturally radioactive form of carbon is absorbed by every organism in the form of food or respiration until it dies.
The rate at which carbon-14 breaks down has been used by archaeologists for decades to date ancient organic artifacts because it has a half-life of 5,568 years ± 30 years, which means that every 5,568 years there's half as much carbon-14 as there was to begin with, then half as much again in 5,568 years, and so on.
One reason why this dating system works is that scientists can, by taking into account the effects of solar activity on cosmic rays, calculate how much carbon-14 is being produced, therefore what the ratio of C-14 to non-radioactive C-13 is, and how old the artifact is. Unfortunately, future archaeologists are going to have a much harder time because atmospheric nuclear tests from 1945 to 1980 doubled the amount of C-14 in the air.
This peaked in the 1960s, when the United States, the Soviet Union, and Britain abandoned atmospheric tests and by the 1990s the excess had dropped to only 20 percent more than the pre-atomic levels. However, manmade C-14 has since been absorbed by plants and animals, making it an excellent trace isotope to learn more about how chemical compounds move through the environment.
But what has this to do with the deep ocean? If you look at how slowly water circulates in the deep hadal trenches over four mi (six km) beneath the surface, it looks like a C-14 peak should be irrelevant because none of it should get down there for hundreds or even thousands of years.
According to the Chinese Academy team, the answer to this question lies in the life that lives at these tremendous depths. It's a very odd place to find any kind of life because, outside of a few volcanic vents, there's no source of energy to sustain life. Sunlight is unable to penetrate such depths, so it's cold, and it's dark.
But there is life, such as a small crustacean called an amphipod that the team, led by geochemist Ning Wang Wang, collected in 2017 from the Mariana, Mussau, and New Britain Trenches in the tropical West Pacific Ocean. In shallow waters, the amphipods live only about two years and grow to a size of about 20 mm (0.8 in), but in the deep trenches, they live for 10 years and grow to 91 mm (3.6 in) long.
According to the team, this is because in the low-temperature and high-pressure environment, the crustaceans develop a very slow metabolism and cell turnover. It's also because the amphipods share a similar lifestyle with other deep-living creatures. There's very little food, so they have become incredible opportunists. Instead of actively swimming about and hunting for prey, the amphipods sit quietly and conserve energy until some tasty morsel comes along.
This poses another question, where does the food come from? Ultimately, it comes from the one big source that's available – the surface. What happens is that, over time, the fish and plankton in the shallower, sunlit waters send food drifting down into the deepest areas in the form of scraps, dead plants and animals, and wastes that the bottom dwellers feed on.
What this means for the Chinese Academy study is that this rain of food is a shortcut to transport the C-14 to the bottom. The organisms at the top ingest it, and then it rains down for the amphipods and others in turn. By analyzing the crustaceans, they not only found excess C-14 in the muscle tissues, but also in their gut contents, which matches samples taken in the shallows.
This, in itself, doesn't pose an environmental hazard, but it does show how pollutants can reach the deepest corners of the abyss in a very short time.
"Besides the fact that material mostly comes from the surface, the age-related bioaccumulation also increases these pollutant concentrations, bringing more threat to these most remote ecosystems," says Wang.
The findings were published in Geophysical Research Letters.
Source: American Geophysical Union | 0.807142 | 3.063865 |
The Ursids is a minor meteor shower producing about 5-10 meteors per hour. It is produced by dust grains left behind by comet Tuttle, which was first discovered in 1790. The shower runs annually from December 17-25. It peaks this year on the night of the 21st and morning of the 22nd.
The second quarter moon will block many of the fainter meteors but if you are patient, you might still be able to catch a few of the brighter ones. Best viewing will be just after midnight from a dark location far away from city lights. The Meteors will appear to radiate from the constellation Ursa Minor, but can appear anywhere in the sky.
Why are they named the Ursids?
The shower is named the Ursids because the meteors seem to radiate from the direction of the constellation Ursa Minor in the sky.
There isn’t a lot of skill involved in watching a meteor shower. Here are some tips on how to maximize your time looking for the Ursids:
- Get out of the city to a place where city and artificial lights do not impede your viewing
- If you are out viewing the shower during its peak, you will not need any special equipment. You should be able to see the shower with your naked eyes.
- Carry a blanket or a comfortable chair with you – viewing meteors, just like any other kind of star gazing is a waiting game, and you need to be comfortable. Plus, you may not want to leave until you can’t see the majestic celestial fireworks anymore.
- Check the weather and moonrise and moonset timings for your location before you leave, and plan your viewing around it. | 0.827591 | 3.026012 |
Proper motion is the astrometric measure of the observed changes in the apparent places of stars or other celestial objects in the sky, as seen from the center of mass of the Solar System, compared to the abstract background of the more distant stars.
The components for proper motion in the equatorial coordinate system (of a given epoch, often J2000.0) are given in the direction of right ascension (μα) and of declination (μδ). Their combined value is computed as the total proper motion (μ). It has dimensions of angle per time, typically arcseconds per year or milliarcseconds per year. Knowledge of the proper motion, distance, and radial velocity allows calculations of true stellar motion or velocity in space in respect to the Sun, and by coordinate transformation, the motion in respect to the Milky Way. Proper motion is not entirely intrinsic to the celestial body or star, because it includes a component due to the motion of the Solar System itself.
Over the course of centuries, stars appear to maintain nearly fixed positions with respect to each other, so that they form the same constellations over historical time. Ursa Major or Crux, for example, look nearly the same now as they did hundreds of years ago. However, precise long-term observations show that the constellations change shape, albeit very slowly, and that each star has an independent motion.
This motion is caused by the movement of the stars relative to the Sun and Solar System. The Sun travels in a nearly circular orbit (the solar circle) about the center of the Milky Way at a speed of about 220 km/s at a radius of 8 kPc from the center, which can be taken as the rate of rotation of the Milky Way itself at this radius.
The proper motion is a two-dimensional vector (because it excludes the component in the direction of the line of sight) and is thus defined by two quantities: its position angle and its magnitude. The first quantity indicates the direction of the proper motion on the celestial sphere (with 0 degrees meaning the motion is due north, 90 degrees meaning the motion is due east, and so on), and the second quantity is the motion's magnitude, typically expressed in arcseconds per year (symbol arcsec/yr, as/yr) or milliarcsecond per year (mas/yr).
where δ is the declination. The factor in cos2δ accounts for the fact that the radius from the axis of the sphere to its surface varies as cosδ, becoming, for example, zero at the pole. Thus, the component of velocity parallel to the equator corresponding to a given angular change in α is smaller the further north the object's location. The change μα, which must be multiplied by cosδ to become a component of the proper motion, is sometimes called the "proper motion in right ascension", and μδ the "proper motion in declination".
If the proper motion in right ascension has been converted by cosδ, the result is designated μα*. For example, the proper motion results in right ascension in the Hipparcos Catalogue (HIP) have already been converted. Hence, the individual proper motions in right ascension and declination are made equivalent for straightforward calculations of various other stellar motions.
For the majority of stars seen in the sky, the observed proper motions are usually small and unremarkable. Such stars are often either faint or are significantly distant, have changes of below 10 milliarcseconds per year, and do not appear to move appreciably over many millennia. A few do have significant motions, and are usually called high-proper motion stars. Motions can also be in almost seemingly random directions. Two or more stars, double stars or open star clusters, which are moving in similar directions, exhibit so-called shared or common proper motion (or cpm.), suggesting they may be gravitationally attached or share similar motion in space.
Barnard's Star has the largest proper motion of all stars, moving at 10.3 seconds of arc per year (arcsec/a). Large proper motion is usually a strong indication that a star is relatively close to the Sun. This is indeed the case for Barnard's Star, located at a distance of about 6 light-years. After the Sun and the Alpha Centauri system, it is the nearest known star to Earth. Because it is a red dwarf with an apparent magnitude of 9.54, it is too faint to see without a telescope or powerful binoculars. Of the stars visible to the naked eye (by convention, limiting visual magnitude of 6.0), 61 Cygni A (magnitude V=5.20) has the highest proper motion at 5.281 arcsec/a, although Groombridge 1830 (magnitude V=6.42), proper motion 7.058 arcsec/a, might be visible for an observer with exceptionally keen vision.
A proper motion of 1 arcsec per year at a distance of 1 light-year corresponds to a relative transverse speed of 1.45 km/s. Barnard's Star's transverse speed is 90 km/s and its radial velocity is 111 km/s (which is at right angles to the transverse velocity), which gives a true motion of 142 km/s. True or absolute motion is more difficult to measure than the proper motion, because the true transverse velocity involves the product of the proper motion times the distance. As shown by this formula, true velocity measurements depend on distance measurements, which are difficult in general.
Usefulness in astronomy
Stars with large proper motions tend to be nearby; most stars are far enough away that their proper motions are very small, on the order of a few thousandths of an arcsecond per year. It is possible to construct nearly complete samples of high proper motion stars by comparing photographic sky survey images taken many years apart. The Palomar Sky Survey is one source of such images. In the past, searches for high proper motion objects were undertaken using blink comparators to examine the images by eye, but modern efforts use techniques such as image differencing to automatically search through digitized image data. Because the selection biases of the resulting high proper motion samples are well understood and well quantified, it is possible to use them to construct an unbiased census of the nearby stellar population — how many stars exist of each true brightness, for example. Studies of this kind show that the local population of stars consists largely of intrinsically faint, inconspicuous stars such as red dwarfs.
Measurement of the proper motions of a large sample of stars in a distant stellar system, like a globular cluster, can be used to compute the cluster's total mass via the Leonard-Merritt mass estimator. Coupled with measurements of the stars' radial velocities, proper motions can be used to compute the distance to the cluster.
Stellar proper motions have been used to infer the presence of a super-massive black hole at the center of the Milky Way. This black hole is suspected to be Sgr A*, with a mass of 4.2 × 106 M☉, where M☉ is the solar mass.
Proper motions of the galaxies in the Local Group are discussed in detail in Röser. In 2005, the first measurement was made of the proper motion of the Triangulum Galaxy M33, the third largest and only ordinary spiral galaxy in the Local Group, located 0.860 ± 0.028 Mpc beyond the Milky Way. The motion of the Andromeda Galaxy was measured in 2012, and an Andromeda–Milky Way collision is predicted in about 4 billion years.[failed verification] Proper motion of the NGC 4258 (M106) galaxy in the M106 group of galaxies was used in 1999 to find an accurate distance to this object. Measurements were made of the radial motion of objects in that galaxy moving directly toward and away from us, and assuming this same motion to apply to objects with only a proper motion, the observed proper motion predicts a distance to the galaxy of 7.2±0.5 Mpc.
Proper motion was suspected by early astronomers (according to Macrobius, AD 400) but a proof was not provided until 1718 by Edmund Halley, who noticed that Sirius, Arcturus and Aldebaran were over half a degree away from the positions charted by the ancient Greek astronomer Hipparchus roughly 1850 years earlier.
The term "proper motion" derives from the historical use of "proper" to mean "belonging to" (cf, propre in French and the common English word property). "Improper motion" would refer to "motion" common to all stars, such as due to axial precession.
Stars with high proper motion
The following are the stars with highest proper motion from the Hipparcos catalog. It does not include stars such as Teegarden's star, which are too faint for that catalog. A more complete list of stellar objects can be made by doing a criteria query at the SIMBAD astronomical database.
|μα · cos δ
|5||Gliese 1 (CD −37 15492) (GJ 1)||5634.68||−2337.71||+25.38||230.42|
|7||61 Cygni A & B||4133.05||3201.78||−65.74||286|
The figure for HIP 67593 is almost certainly an error, probably because the star has a relatively nearby brighter visual binary companion; the movement between the DSS2 and SDSS9 images is not consistent with the high proper motion. Gaia measured a much smaller proper motion for DR2, but also a parallax difference of a factor fifteen between the star and its nearby apparently common-proper-motion companion HIP 67594. A resolution of this will have to wait for Gaia DR3; generally very-high-proper-motion stars do not show up in Gaia DR2.
- Celestial coordinate system
- Galaxy rotation curve
- Leonard–Merritt mass estimator
- Milky Way
- Peculiar velocity
- Radial velocity
- Relative velocity
- Solar apex
- Space velocity (astronomy)
- Very-long-baseline interferometry
- Theo Koupelis; Karl F. Kuhn (2007). In Quest of the Universe. Jones & Bartlett Publishers. p. 369. ISBN 978-0-7637-4387-1.
- D. Scott Birney; Guillermo Gonzalez; David Oesper (2007). Observational Astronomy. p. 75. ISBN 978-0-521-85370-5.
- Simon F. Green; Mark H. Jones (2004). An Introduction to the Sun and Stars. Cambridge University Press. p. 87. ISBN 978-0-521-54622-5.
- D. Scott Birney; Guillermo Gonzalez; David Oesper (2007). Observational Astronomy. Cambridge University Press. p. 73. ISBN 978-0-521-85370-5.
- Horace A. Smith (2004). RR Lyrae Stars. Cambridge University Press. p. 79. ISBN 978-0-521-54817-5.
- M Reid; A Brunthaler; Xu Ye; et al. (2008). "Mapping the Milky Way and the Local Group". In F Combes; Keiichi Wada (eds.). Mapping the Galaxy and Nearby Galaxies. Springer. ISBN 978-0-387-72767-7.
- Y Sofu & V Rubin (2001). "Rotation Curves of Spiral Galaxies". Annual Review of Astronomy and Astrophysics. 39: 137–174. arXiv:astro-ph/0010594. Bibcode:2001ARA&A..39..137S. doi:10.1146/annurev.astro.39.1.137.
- Abraham Loeb; Mark J. Reid; Andreas Brunthaler; Heino Falcke (2005). "Constraints on the proper motion of the Andromeda galaxy based on the survival of its satellite M33" (PDF). The Astrophysical Journal. 633 (2): 894–898. arXiv:astro-ph/0506609. Bibcode:2005ApJ...633..894L. doi:10.1086/491644.
- William Marshall Smart; Robin Michael Green (1977). Textbook on Spherical Astronomy. Cambridge University Press. p. 252. ISBN 978-0-521-29180-4.
- Charles Leander Doolittle (1890). A Treatise on Practical Astronomy, as Applied to Geodesy and Navigation. Wiley. p. 583.
- Simon Newcomb (1904). The Stars: A study of the Universe. Putnam. pp. 287–288.
- Matra Marconi Space, Alenia Spazio (September 15, 2003). "The Hipparcos and Tycho Catalogues : Astrometric and Photometric Star Catalogues derived from the ESA Hipparcos Space Astrometry Mission" (PDF). ESA. p. 25. Archived from the original (PDF) on Mar 3, 2016. Retrieved 2015-04-08.
- See Majewski, Steven R. (2006). "Stellar motions: parallax, proper motion, radial velocity and space velocity". University of Virginia. Archived from the original on 2013-07-07. Retrieved 2008-12-31.
- See lecture notes by Steven Majewski.
- Hipparcos: Catalogues: The Millennium Star Atlas: The Top 20 High Proper Motion, European Space Agency, retrieved 2019-06-27
- Lemay, Damien (1992). "Book-Review – Sky Catalogue 2000.0 – V.1 – Stars to Magnitude 8.0 ED.2". Journal of the Royal Astronomical Society of Canada. 86: 221. Bibcode:1992JRASC..86..221L.
- Ghez, Andrea M.; et al. (2003). "The First Measurement of Spectral Lines in a Short-Period Star Bound to the Galaxy's Central Black Hole: A Paradox of Youth". Astrophysical Journal. 586 (2): L127–L131. arXiv:astro-ph/0302299. Bibcode:2003ApJ...586L.127G. doi:10.1086/374804.
- Andreas Brunthaler (2005). "M33 – Distance and Motion". In Siegfried Röser (ed.). Reviews in Modern Astronomy: From Cosmological Structures to the Milky Way. Wiley. pp. 179–194. ISBN 978-3-527-40608-1.
- A. Brunthaler; M.J. Reid; H. Falcke; L.J. Greenhill; C. Henkel (2005). "The Geometric Distance and Proper Motion of the Triangulum Galaxy (M33)". Science. 307 (5714): 1440–1443. arXiv:astro-ph/0503058. Bibcode:2005Sci...307.1440B. doi:10.1126/science.1108342. PMID 15746420.
- Sangmo Tony Sohn; Jay Anderson; Roeland van der Marel (Jul 1, 2012). "The M31 velocity vector. I. Hubble Space Telescope proper-motion measurements". The Astrophysical Journal. 753 (1): 7. arXiv:1205.6863. Bibcode:2012ApJ...753....7S. doi:10.1088/0004-637X/753/1/7.
- Steven Weinberg (2008). Cosmology. Oxford University Press. p. 17. ISBN 978-0-19-852682-7.
- J. R. Herrnstein; et al. (1999). "A geometric distance to the galaxy NGC4258 from orbital motions in a nuclear gas disk". Nature. 400 (6744): 539–541. arXiv:astro-ph/9907013. Bibcode:1999Natur.400..539H. doi:10.1038/22972.
- Otto Neugebauer (1975). A History of Ancient Mathematical Astronomy. Birkhäuser. p. 1084. ISBN 978-3-540-06995-9.
- Staff (September 15, 2003). "The 150 Stars in the Hipparcos Catalogue with Largest Proper Motion". ESA. Retrieved 2007-07-21.
- "SIMBAD". Centre de Données astronomiques de Strasbourg. Retrieved 2016-04-13.
- Fabricius, C.; Makarov, V.V. (May 2000). "Hipparcos astrometry for 257 stars using Tycho-2 data". Astronomy and Astrophysics Supplement. 144: 45–51. Bibcode:2000A&AS..144...45F. doi:10.1051/aas:2000198. | 0.909495 | 4.147217 |
Pluto's a dog. How can a dog have underground oceans?
Pluto may contain a colossal underground ocean, say New Horizons mission scientists. Two new Letters in Nature, Reorientation of Sputnik Planitia implies a subsurface ocean on Pluto and Reorientation and faulting of Pluto due to volatile loading within Sputnik Planitia considers the icy heart-shaped “lava lamp” found on the …
"Pluto may contain a colossal underground ocean"
It seems very unlikely that Pluto still has an underground ocean but it may well have had one a few billions years ago when the Sputnik Planitia was formed.
The assertion that there are two reasons why Pluto could currently have a liquid underground ocean is flawed. Firstly, tectonic activity is a consequence of internal heat, not a cause of it, and secondly, Pluto is so small that after ~4 billion years there will be hardly any radioactivity left.
Hold on, this is not an assertion but one of two different theories that have been offered to explain the observed data from New Horizons.
Your observations about the conditions on Pluto may indeed be correct, but there is evidence of the movement of the Sputnik Planitia within recent geological timescales. That and the visual absence of cratering on the surface of the Planitia, which is accepted as evidence of the activity of some sort of process that has recently (geologically speaking again) reshaped the area, leaving a smooth surface.
Some sort of activity is happening out there, that is apparent, and that implies a source of energy to drive it. This is just an attempt to explain that, not proof.
1)The impact that cause Sputnik Planitia created the heat required to cause the effects we now observe.
2) The impact crater looks as if the impact may have been slow - this may have been a moon whose eccentric orbit caused heating of Pluto before impact
Half life of Uranium is 3.8 billion years, half life of Thorium is 13 billion years, however, these are
TERRESTIAL EARTH ARTIFACTS, and vary with temperature, pressure and particle bombardment.
Bridgemann Effect, under 100 atmospheres, with Hydrogen, every metallic element is radioactive.
Although Pluto and Charon are tidally locked and Charon's orbit is pretty circular could the fact that the barycenter lies outside of Pluto cause a form of tidal heating since the gravitational pull of Charon will vary as they both orbit around the barycenter or would the effect be much too small ?
The most important point is that Pluto is phase locked to Charon; i.e. Pluto always presents the same face to Charon. For that to happen, there must be body tides in Pluto. How much heating they cause is another matter.
I'd be tempted to say the heating would be greater if the barycentre was inside Pluto, and Charon's orbit was more eccentric and less coplanar. But maybe Charon's mass (12% of Pluto's) more than makes up for that.
Biting the hand that feeds IT © 1998–2020 | 0.801262 | 3.685071 |
Julian, quite a challenging question. I will only be trying to answer the first part – the Sun-Earth distance and the Earth-Stars distance.? Even then as my team suggests, I might be introducing mathematical terms that you have not met yet, but I have included links to other sources of help.
To answer the first question I recommend you read a Universe Today article It is an excellent historical review of the problems that the early scientists had in determining the Earth-Sun distance. The answer finally came from observations of the movement of the planet Venus across the face of the Sun. In it the writer refers to a Nasa document that tries to explain the methods used. In present times the distance to the Sun is measured by ‘bouncing’ a radar pulse of of it.
Determining the distance to the other stars becomes possible once the Earth-Sun distance was known. It uses a technique called parallax. I would like to illustrate this with a question which tackles a simpler problem. ‘How far is my finger away from my nose?’
Try this little experiment, put a finger in an upright position in front of your nose. Now close one eye and note the position of the finger. Close that eye and open the other one. The finger moves! Now suppose, with help, you could measure the amount of movement. You could end up with diagrams like those below. Did you make a note of the position of your finger relative to your nose? No – you can now see how you could work this out.
Now let’s do a little geometry and add an axis
We can then measure the angle of the apparent movement
You end with a right angled triangle ABC, knowing the angle x AND the distance between your eyes you should be able to do a bit of trigonometry using TAN x = opposite/adjacent (Tan x = AB/BC) and work out the distance of your finger from your face. For an introduction to trigonometry please look at this site.
Amazingly this is (in a crude way) the same process by which astronomers can measure the distance to the stars. Instead of using the distance between your eyes they use the orbit of the Earth. They look at a star and make a note of it’s position and then do the same thing 6 months later when the Earth is at the opposite side of the Sun. They therefore have AB (the distance between the Sun and the Earth and they have the angle through which the star has apparently moved.
This gives the route to determining the distance between the Earth and a Star. | 0.839167 | 3.529618 |
Dust from meteorites that crash-landed on Earth have revealed that Earth's precursor, known as proto-Earth, formed much faster than previously thought, a new study finds.
An analysis of this meteorite dust showed that proto-Earth formed within about 5 million years, which is extremely fast, astronomically speaking.
Put another way, if the entire 4.6 billion years of the solar system's existence were compressed into a 24-hour period, proto-Earth formed in just 1 minute and 30 seconds, the researchers said.
The new finding breaks with the previously held idea that proto-Earth formed when larger and larger planetary bodies randomly slammed into one another, a process that would have taken several tens of millions of years, or about 5 to 15 minutes in the fictional 24-hour timescale.
In contrast, the new idea holds that planets formed through the accretion of cosmic dust, a process in which dust attracts more and more particles through gravity. "We start from dust, essentially," study lead researcher Martin Schiller said in a statement. Schiller is an associate professor of geochemistry at the Centre for Star and Planet Formation (StarPlan) at the University of Copenhagen's Globe Institute, in Denmark.
With accretion, millimeter-size particles would have come together, "raining down on the growing body and making the planet in one go," Schiller said.
Schiller and his colleagues made the finding by studying iron isotopes, or different versions of the element iron, in meteorite dust. After looking at iron isotopes in different types of meteorites, they realized that only one type had an iron profile that was similar to Earth's: the CI chondrites, which are stony meteorites. (The "C" stands for carbonaceous and the "I" stands for Ivuna, a place in Tanzania where some CI meteorites are found.)
The dust in these CI chondrites is the best approximation out there for the solar system's overall composition, the researchers said. In the solar system's early days, dust like this joined with gas and both were funneled into a accretion disk orbiting the growing sun.
Over the course of 5 million years, the solar system's planets formed. According to the new study, the proto-Earth's iron core also formed during this time, snatching up accreted iron from the proto-planet's mantle. Eventually, this proto-planet became the Earth we know today.
Message from Mars
Meteorites from Mars tell scientists that, in the beginning, the composition of iron isotopes in the material making up Earth were different than they were later on. This likely happened because heat from the young growing sun altered them, the researchers said.
After a few hundred thousand years passed, the area where Earth was forming became cold enough for unheated CI dust that came from farther away to become part of proto-Earth's accretion disc.
Given that iron from this far away dust is found in Earth's mantle today, it makes sense that "most of the previous iron was already removed into the core," Schiller said. "That is why the core formation must have happened early."
The other idea — that Earth formed when planetary bodies randomly collided with one another — doesn't hold, he said. "If the Earth's formation was a random process where you just smashed bodies together, you would never be able to compare the iron composition of the Earth to only one type of meteorite," Schiller said. "You would get a mixture of everything."
The new finding may also apply to other planets in the universe, the researchers noted. In essence, this means that other planets may grow much faster than previously realized. In fact, there is already evidence that this is likely the case, according to data on thousands of exoplanets in other galaxies, said study co-researcher Martin Bizzarro, a professor at StarPlan.
"Now we know that planet formation happens everywhere," Bizzarro said in the statement. "When we understand these mechanisms in our own solar system, we might make similar inferences about other planetary systems in the galaxy."
This process may even explain when and how often water is accreted during planet formation.
"If the theory of early planetary accretion really is correct, water is likely just a by-product of the formation of a planet like the Earth," Bizzarro said. "Making the ingredients of life, as we know it, [is] more likely to be found elsewhere in the universe."
The study was published online Feb. 12 in the journal Science Advances.
- Crash! 10 biggest impact craters on Earth
- Earth's 8 biggest mysteries
- Photo timeline: How the Earth formed
Originally published on Live Science. | 0.866071 | 3.800992 |
6:15 PM - 7:30 PM
[PPS21-P09] The possibility of the homogeneization of the isotopic ratio in the primordial solar nebula
Star and planetary systems are formed through gravitational collapse of molecular cloud cores. Since molecular clouds consist of materials from various super novae and red giant stars, it is naturally considered that dust particles in molecular cloud cores have various isotopic ratios. On the other hand, it is known that solid materials in our solar system, especially materials of the Earth, moon, mars, and meteorites, have almost identical isotopic ratios. To homogenize isotopic ratios in solid materials, it seems that the material should be evaporated completely once, mixed well, and re-solidified. So, the homogeneous isotopic ratio in the current solar system suggests that our solar system experienced some massive evaporation events in its formation phase. However, it is not well understood which process can be responsible for such a high temperature event in the solar nebula.
Goal of this study:
We clarify if the homogenization of the isotopic ratio among all the solid materials in the solar nebula can be realized in the course of the formation and evolution of the solar nebula.
We suppose a molecular cloud core whose mass is one solar mass. The core is assumed to rotate rigidly and to consist of gas and dust particles. Dust particles have various isotopic ratios, but they are mechanically well mixed in the core.The collapse of the molecular cloud core, and the following formation and evolution of the solar nebula are modeled based on Cassen & Moosman (1981). Landing places of infalling materials from the core is estimated depending on the angular momentum. Turbulence is present in the solar nebula and the viscous torque due to the turbulence works. Also, the gravitational torque produced by the self-gravity of the solar nebula is taken into account (Nakamoto & Nakagawa 1995). The motion of dust particles relative to the gas is calculated using the turbulence diffusion model (Wherstedt & Gail 2002). The temperature of the solar nebula is obtained based on the balance between the viscous heating and the radiative cooling. The model parameters are the initial temperature and the angular velocity of the molecular cloud core.We assume that dust particles evaporate completely at the temperature of 2,000 K, and when the gas temperature becomes less than that, isotopically homogeneous dust particles are produced.
The temperature of the solar nebula becomes a decreasing function of the distance from the Sun. So, when the initial temperature of the core is high, and the initial rotation velocity of the core is low, the radius of the solar nebula becomes small and the fraction of isotopically homogeneous dust particles becomes high. For example, almost all the solid materials in the solar nebula becomes isotopically identical, when the initial temperature of the core is 15 K and the angular velocity is (2-3)x10^14 s^-1.
According to observations, angular velocities of molecular cloud cores are around from 10^-14 s^-1 to 10^-13 s^-1 (Goodman et al. 1993). So, it is implied that the molecular cloud core that formed our solar system might have a smaller angular velocity compared to typical values. This may be consistent with a fact that our Sun is a single star: it is shown that molecular cloud cores having higher angular momentum tend to form binary systems, while those having lower angular momentum tend to form single star (Matsumoto & Hanawa 2003).
We investigated the formation and evolution of our solar nebula following the gravitational collapse of the molecular cloud using numerical simulations. And we found that isotopic ratio of solid materials in the solar nebula can be completely homogenized, if the radius of the solar nebula is small enough due to the high temperature or the low angular velocity of the initial molecular cloud core. | 0.81595 | 4.05038 |
Anneila I. Sargent
Research InterestsStar Formation and Evolution
My research focuses mainly on how stars are born and evolve in our own Milky Way and in other galaxies. How are new stars created in the cores of dense molecular clouds of dust and gas? How do the new stars emerge from this obscuring material? How is the material itself dissipated? Could planetary systems form around some of these stars? Direct millimeter, submillimeter, and infrared observations of the dust and gas associated with collapsing clouds, or surrounding newly-born stars, provide important information about the physical and chemical properties of these interstellar and circumstellar regions. I am especially interested in the circumstellar disks of gas and dust that appear to be an integral part of very early stellar evolution and are potential sites for planet formation. Studies of these disks need very high resolution measurements; some of the very first detections were made with Caltech's millimeter-wave array in California's Owens Valley.
Credit: Stephen White
In recent years, seeking more and more details of disk properties, I have become heavily involved in combining the Caltech instrument with other U.S. university arrays to create a larger and more powerful interferometer, called CARMA, at a higher site. Caltech students and postdocs played a major role in the CARMA commissioning and are critical to its successful operation. It is an observatory where students can get real hands-on experience while tackling key astronomical questions. Nowadays, I also spend quite a bit of time on the planning of new submillimeter facilities like the international submillimeter-wave array, ALMA, being built in northern Chile. ALMA will revolutionize our understanding of star and planet formation, and CARMA is a great place to get a head start on the latest problems.
An aspect of my job that I have enjoyed has been the opportunity to do lots of different things: teaching and research, getting new instruments built, and also advising on astronomy policy and funding. I am currently Vice President for Student Affairs at the Institute and that's a completely new area for me.
[Image credits: Norman Seeff; Stephen White] | 0.883324 | 3.145973 |
When it comes to the search for extra-terrestrial intelligence (SETI) in the Universe, there is the complicated matter of what to be on the lookout for. Beyond the age-old question of whether or not intelligent life exists elsewhere in the Universe (statistically speaking, it is very likely that it does), there’s also the question of whether or not we would be able to recognize it if and when we saw it.
Given that humanity is only familiar with one form of civilization (our own), we tend to look for indications of technologies we know or which seem feasible. In a recent study, a researcher from the Instituto de Astrofísica de Canarias (IAC) proposed looking for large bands of satellites in distant star systems – a concept that was proposed by the late and great Arthur C. Clarke (known as a Clarke Belt).
The study – titled “Possible Photometric Signatures of Moderately Advanced Civilizations: The Clarke Exobelt” – was conducted by Hector Socas-Navarro, an astrophysicist with the IAC and the Universidad de La Laguna. In it, he advocates using next-generation telescopes to look for signs of massive belts of geostationary communication satellites in distant star systems.
This proposal is based in part on a paper written by Arthur C. Clarke in 1945 (titled “Peacetime Uses for V2“), in which he proposed sending “artificial satellites” into geostationary orbit around Earth to create a global communications network. At present, there are about 400 such satellites in the “Clarke Belt” – a region named in honor of him that is located 36,000 km above the Earth.
This network forms the backbone of modern telecommunications and in the future, many more satellites are expected to be deployed – which will form the backbone of the global internet. Given the practicality of satellites and the fact that humanity has come to rely on them so much, Socas-Navarro considers that a belt of artificial satellites could naturally be considered “technomarkers” (the analogues of “biomarkers”, which indicate the presence of life).
As Socas-Navarro explained to Universe Today via email:
“Essentially, a technomarker is anything that we could potentially observe which would reveal the presence of technology elsewhere in the Universe. It’s the ultimate clue to find intelligent life out there. Unfortunately, interstellar distances are so great that, with our current technology, we can only hope to detect very large objects or structures, something comparable to the size of a planet.”
In this respect, a Clarke Exobelt is not dissimilar from a Dyson Sphere or other forms of megastructures that have been proposed by scientists in the past. But unlike these theoretical structures, a Clarke Exobelt is entirely feasible using present-day technology.
“Other existing technomarkers are based on science fiction technology of which we know very little,” said Socas-Navarro. “We don’t know if such technologies are possible or if other alien species might be using them. The Clarke Exobelt, on the other hand, is a technomarker based on real, currently existing technology. We know we can make satellites and, if we make them, it’s reasonable to assume that other civilizations will make them too.”
According to Socas-Navarro, there is some “science fiction” when it comes to Clarke Exobelts that would actually be detectable using these instruments. As noted, humanity has about 400 operational satellites occupying Earth’s “Clarke Belt”. This is about one-third of the Earth’s existing satellites, whereas the rest are at an altitude of 2000 km (1200 mi) or less from the surface – the region known as Low Earth Orbit (LEO).
This essentially means that aliens would need to have billions more satellites within their Clarke Belt – accounting for roughly 0.01% of the belt area – in order for it to be detectable. As for humanity, we are not yet to the point where our own Belt would be detectable by an extra-terrestrial intelligence (ETI). However, this should not take long given that the number of satellites in orbit has been growing exponentially over the past 15 years.
Based on simulations conducted by Socas-Navarro, humanity will reach the threshold where its satellite band will be detectable by ETIs by 2200. Knowing that humanity will reach this threshold in the not-too-distant future makes the Clarke Belt a viable option for SETI. As Socas-Navarro explained:
“In this sense, the Clarke Exobelt is interesting because it’s the first technomarker that looks for currently existing technology. And it goes both ways too. Humanity’s Clarke Belt is probably too sparsely populated to be detectable from other stars right now (at least with technology like ours). But in the last decades we have been populating it at an exponential rate. If this trend were to continue, our Clarke Belt would be detectable from other stars by the year 2200. Do we want to be detectable? This is an interesting debate that humanity will have to resolve soon.
As for when we might be able to start looking for Exobelts, Socas-Navarro indicates that this will be possible within the next decade. Using instruments like the James Webb Space Telescope (JWST), the Giant Magellan Telescope (GMT), the European Extremely Large Telescope (E-ELT), and the Thirty Meter Telescope (TMT), scientists will have ground-based and space-based telescopes with the necessary resolution to spot these bands around exoplanets.
As for how these belts would be detected, that would come down to the most popular and effective means for finding exoplanets to date – the Transit Method (aka. Transit Photometry). For this method, astronomers monitor distant stars for periodic dips in brightness, which are indications of an exoplanet passing in front of the star. Using next-generation telescopes, astronomers may also be able to detect reflected light from a dense band of satellites in orbit.
“However, before we point our supertelescopes to a planet we need to identify good candidates,” said Socas-Navarro. “There are too many stars to check and we can’t go one by one. We need to rely on exoplanet search projects, such as the recently launched satellite TESS, to spot interesting candidates. Then we can do follow-up observations with supertelescopes to confirm or refute those candidates.”
In this respect, telescopes like the Kepler Space Telescope and the Transiting Exoplanet Survey Telescope (TESS) will still serve an important function in searching for technomarkers. Whereas the former telescope is due to retire soon, the latter is scheduled to launch in 2018.
While these space-telescopes would search for rocky planets that are located within the habitable zones of thousands of stars, next-generation telescopes could search for signs of Clarke Exobelts and other technomarkers that would be otherwise hard to spot. However, as Socas-Navarro indicated, astronomers could also find evidence of Exobands by sifting through existing data as well.
“In doing SETI, we have no idea what we are looking for because we don’t know what the aliens are doing,” he said. “So we have to investigate all the possibilities that we can think of. Looking for Clarke Exobelts is a new way of searching, it seems at least reasonably plausible and, most importantly, it’s free. We can look for signatures of Clarke Exobelts in currently existing missions that search for exoplanets, exorings or exomoons. We don’t need to build costly new telescopes or satellites. We simply need to keep our eyes open to see if we can spot the signatures presented in the simulation in the flow of data from all of those projects.”
Humanity has been actively searching for signs of extra-terrestrial intelligence for decades. To know that our technology and methods are becoming more refined, and that more sophisticated searches could begin within a decade, is certainly encouraging. Knowing that we won’t be visible to any ETIs that are out there for another two centuries, that’s also encouraging!
And be sure to check out this cool video by our friend, Jean Michael Godier, where he explains the concept of a Clarke Exobelt: | 0.885708 | 3.77112 |
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Newborn giant planet discovered 330 light-years away
Published Thursday, February 13, 2020 7:23AM EST
Artist's conception of a massive planet orbiting a cool, young star. (NASA / JPL-Caltech / R. Hurt)
Most planets found by astronomers are "old" -- they're fully formed after millions of years pulling together elements around their star.
But researchers just located a baby giant exoplanet orbiting a young star just 330 light-years from Earth, making it the closest of its kind to us.
The planet is known as 2MASS 1155-7919 b, and it's located in Epsilon Chamaeleontis Association, a young group of stars seen in our southern sky near the Chameleon constellation.
Researchers from the Rochester Institute of Technology made the discovery using data collected by the European Space Agency's Gaia space observatory.
The discovery was published recently in the Research Notes of the American Astronomical Society.
The planet orbits a five million-year-old star, which is a thousand times younger than our own sun. But, unusually, it's very distant from the star, orbiting at 600 times the distance from the Earth to the sun.
"The dim, cool object we found is very young and only 10 times the mass of Jupiter, which means we are likely looking at an infant planet, perhaps still in the midst of formation," said Annie Dickson-Vandervelde, lead study author and astrophysical sciences and technology Ph.D. student at Rochester Institute of Technology.
Future observations could tell scientists how the planet ended up at such a distance from its star. This could provide greater insight about wide orbits of massive planets. But the discovery itself helps astronomers study the process of gas giant formation.
"Though lots of other planets have been discovered through the Kepler mission and other missions like it, almost all of those are 'old' planets," Dickson-Vandervelde said.
"This is also only the fourth or fifth example of a giant planet so far from its 'parent' star, and theorists are struggling to explain how they formed or ended up there." | 0.816863 | 3.090426 |
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