LIGHT OF THE UNIVERSE - How Does Light Travel?

How Does Light Travel?:

Ever since Democritus - a Greek philosopher who lived between the 5th and 4th century's BCE - argued that all of existence was made up of tiny indivisible atoms, scientists have been speculating as to the true nature of light. Whereas scientists ventured back and forth between the notion that light was a particle or a wave until the modern, the 20th century led to breakthroughs that showed that it behaves as both.



These included the discovery of the electron, the development of quantum theory, and Einstein's Theory of Relativity. However, there remains many fascinating and unanswered questions when it comes to light, many of which arise from its dual nature. For instance, how is it that light can be apparently without mass, but still behave as a particle? And how can it behave like a wave and pass through a vacuum, when all other waves require a medium to propagate?

Theory of Light to the 19th Century:

During the Scientific Revolution, scientists began moving away from Aristotelian scientific theories that had been seen as accepted canon for centuries. This included rejecting Aristotle's theory of light, which viewed it as being a disturbance in the air (one of his four "elements" that composed matter), and embracing the more mechanistic view that light was composed of indivisible atoms.



In many ways, this theory had been previewed by atomists of Classical Antiquity - such as Democritus and Lucretius - both of whom viewed light as a unit of matter given off by the sun. By the 17th century, several scientists emerged who accepted this view, stating that light was made up of discrete particles (or "corpuscles"). This included Pierre Gassendi, a contemporary of René Descartes, Thomas Hobbes, Robert Boyle, and most famously, Sir Isaac Newton.







Newton's corpuscular theory was an elaboration of his view of reality as an interaction of material points through forces. This theory would remain the accepted scientific view for more than 100 years, the principles of which were explained in his 1704 treatise "Opticks, or, a Treatise of the Reflections, Refractions, Inflections, and Colours of Light". According to Newton, the principles of light could be summed as follows:

• Every source of light emits large numbers of tiny particles known as corpuscles in a medium surrounding the source.
• These corpuscles are perfectly elastic, rigid, and weightless.

This represented a challenge to "wave theory", which had been advocated by 17th century Dutch astronomer Christiaan Huygens. . These theories were first communicated in 1678 to the Paris Academy of Sciences and were published in 1690 in his “Traité de la lumière“ (“Treatise on Light“). In it, he argued a revised version of Descartes views, in which the speed of light is infinite and propagated by means of spherical waves emitted along the wave front.

Double-Slit Experiment:

By the early 19th century, scientists began to break with corpuscular theory. This was due in part to the fact that corpuscular theory failed to adequately explain the diffraction, interference and polarization of light, but was also because of various experiments that seemed to confirm the still-competing view that light behaved as a wave.



https://youtu.be/ZGoDK18b3LE



The most famous of these was arguably the Double-Slit Experiment, which was originally conducted by English polymath Thomas Young in 1801 (though Sir Isaac Newton is believed to have conducted something similar in his own time). In Young's version of the experiment, he used a slip of paper with slits cut into it, and then pointed a light source at them to measure how light passed through it.



According to classical (i.e. Newtonian) particle theory, the results of the experiment should have corresponded to the slits, the impacts on the screen appearing in two vertical lines. Instead, the results showed that the coherent beams of light were interfering, creating a pattern of bright and dark bands on the screen. This contradicted classical particle theory, in which particles do not interfere with each other, but merely collide.



The only possible explanation for this pattern of interference was that the light beams were in fact behaving as waves. Thus, this experiment dispelled the notion that light consisted of corpuscles and played a vital part in the acceptance of the wave theory of light. However subsequent research, involving the discovery of the electron and electromagnetic radiation, would lead to scientists considering yet again that light behaved as a particle too, thus giving rise to wave-particle duality theory.

Electromagnetism and Special Relativity:

Prior to the 19th and 20th centuries, the speed of light had already been determined. The first recorded measurements were performed by Danish astronomer Ole Rømer, who demonstrated in 1676 using light measurements from Jupiter's moon Io to show that light travels at a finite speed (rather than instantaneously).







By the late 19th century, James Clerk Maxwell proposed that light was an electromagnetic wave, and devised several equations (known as Maxwell's equations) to describe how electric and magnetic fields are generated and altered by each other and by charges and currents. By conducting measurements of different types of radiation (magnetic fields, ultraviolet and infrared radiation), he was able to calculate the speed of light in a vacuum (represented as c).



In 1905, Albert Einstein published "On the Electrodynamics of Moving Bodies”, in which he advanced one of his most famous theories and overturned centuries of accepted notions and orthodoxies. In his paper, he postulated that the speed of light was the same in all inertial reference frames, regardless of the motion of the light source or the position of the observer.



Exploring the consequences of this theory is what led him to propose his theory of Special Relativity, which reconciled Maxwell’s equations for electricity and magnetism with the laws of mechanics, simplified the mathematical calculations, and accorded with the directly observed speed of light and accounted for the observed aberrations. It also demonstrated that the speed of light had relevance outside the context of light and electromagnetism.



For one, it introduced the idea that major changes occur when things move close the speed of light, including the time-space frame of a moving body appearing to slow down and contract in the direction of motion when measured in the frame of the observer. After centuries of increasingly precise measurements, the speed of light was determined to be 299,792,458 m/s in 1975.

Einstein and the Photon:

In 1905, Einstein also helped to resolve a great deal of confusion surrounding the behavior of electromagnetic radiation when he proposed that electrons are emitted from atoms when they absorb energy from light. Known as the photoelectric effect, Einstein based his idea on Planck's earlier work with "black bodies" - materials that absorb electromagnetic energy instead of reflecting it (i.e. white bodies).



https://youtu.be/q74suqg5pCk



At the time, Einstein's photoelectric effect was attempt to explain the "black body problem", in which a black body emits electromagnetic radiation due to the object's heat. This was a persistent problem in the world of physics, arising from the discovery of the electron, which had only happened eight years previous (thanks to British physicists led by J.J. Thompson and experiments using cathode ray tubes).



At the time, scientists still believed that electromagnetic energy behaved as a wave, and were therefore hoping to be able to explain it in terms of classical physics. Einstein's explanation represented a break with this, asserting that electromagnetic radiation behaved in ways that were consistent with a particle - a quantized form of light which he named "photons". For this discovery, Einstein was awarded the Nobel Prize in 1921.

Wave-Particle Duality:

Subsequent theories on the behavior of light would further refine this idea, which included French physicist Louis-Victor de Broglie calculating the wavelength at which light functioned. This was followed by Heisenberg's "uncertainty principle" (which stated that measuring the position of a photon accurately would disturb measurements of it momentum and vice versa), and Schrödinger's paradox that claimed that all particles have a "wave function".



In accordance with quantum mechanical explanation, Schrodinger proposed that all the information about a particle (in this case, a photon) is encoded in its wave function, a complex-valued function roughly analogous to the amplitude of a wave at each point in space. At some location, the measurement of the wave function will randomly "collapse", or rather "decohere", to a sharply peaked function. This was illustrated in Schrödinger famous paradox involving a closed box, a cat, and a vial of poison (known as the "Schrödinger Cat" paradox).







According to his theory, wave function also evolves according to a differential equation (aka. the Schrödinger equation). For particles with mass, this equation has solutions; but for particles with no mass, no solution existed. Further experiments involving the Double-Slit Experiment confirmed the dual nature of photons. where measuring devices were incorporated to observe the photons as they passed through the slits.



When this was done, the photons appeared in the form of particles and their impacts on the screen corresponded to the slits - tiny particle-sized spots distributed in straight vertical lines. By placing an observation device in place, the wave function of the photons collapsed and the light behaved as classical particles once more. As predicted by Schrödinger, this could only be resolved by claiming that light has a wave function, and that observing it causes the range of behavioral possibilities to collapse to the point where its behavior becomes predictable.



The development of Quantum Field Theory (QFT) was devised in the following decades to resolve much of the ambiguity around wave-particle duality. And in time, this theory was shown to apply to other particles and fundamental forces of interaction (such as weak and strong nuclear forces). Today, photons are part of the Standard Model of particle physics, where they are classified as boson - a class of subatomic particles that are force carriers and have no mass.



So how does light travel? Basically, traveling at incredible speeds (299 792 458 m/s) and at different wavelengths, depending on its energy. It also behaves as both a wave and a particle, able to propagate through mediums (like air and water) as well as space. It has no mass, but can still be absorbed, reflected, or refracted if it comes in contact with a medium. And in the end, the only thing that can truly slow down or arrest the speed of light is gravity (i.e. a black hole).



https://youtu.be/jFvT2YPJQeM



What we have learned about light and electromagnetism has been intrinsic to the revolution which took place in physics in the early 20th century, a revolution that we have been grappling with ever since. Thanks to the efforts of scientists like Maxwell, Planck, Einstein, Heisenberg and Schrodinger, we have learned much, but still have much to learn.



For instance, its interaction with gravity (along with weak and strong nuclear forces) remains a mystery. Unlocking this, and thus discovering a Theory of Everything (ToE) is something astronomers and physicists look forward to. Someday, we just might have it all figured out!



We have written many articles about light here at Universe Today. For example, here's How Fast is the Speed of Light?, How Far is a Light Year?, What is Einstein's Theory of Relativity?



If you'd like more info on light, check out these articles from The Physics Hypertextbook and NASA's Mission Science page.



We've also recorded an entire episode of Astronomy Cast all about Interstellar Travel. Listen here, Episode 145: Interstellar Travel.

The post How Does Light Travel? appeared first on Universe Today.

New Horizons Sends Back First Science On Distant Kuiper Belt Object

New Horizons Sends Back First Science On Distant Kuiper Belt Object:

Even the most curmudgeonly anti-space troll has to admit that the New Horizons mission to Pluto has been an overwhelming success.



It's not like New Horizons discovered life or anything, but it did bring an otherwise cold, distant lump to life for humanity. Vivid images and detailed scientific data revealed Pluto as a dynamic, changing world, with an active surface and an atmosphere. And we haven't even received all of the data from New Horizons' mission to Pluto yet.



Fresh off its historic visit to Pluto, New Horizons is headed for the Kuiper Belt, and just sent back its first science on one of the denizens of the distant belt of objects. The target in this case is 1994 JR1, a 145 km (90 mi.) wide Kuiper Belt Object (KBO). that orbits the Sun at a distance greater than 5 billion km. (3 billion mi.) New Horizons has now observed 1994 JR1 twice, and the team behind the mission has garnered new insights into this KBO based on these observations.



The spacecraft's Long Range Reconnaissance Imager (LORRI) captured images of 1994 JR1 on April 7th-8th from a distance of 111 million km. (69 million mi.). That's far closer than the images New Horizons captured in November 2015 from a distance of 280 million km (170 million miles).







New Horizons science team member Simon Porter, of the Southwest Research Institute (SwRI) in Boulder Colorado, commented on the importance of these images. "Combining the November 2015 and April 2016 observations allows us to pinpoint the location of JR1 to within 1,000 kilometers (about 600 miles), far better than any small KBO," Porter said.



Porter added that this accurate measurement of the KBO's orbit allows New Horizons science team members to quash the idea that JR1 is a quasi-satellite of Pluto.



The team was also able to determine, by measuring the light reflected from the surface, that JR1's rotational period is only 5.4 hours. That's fast for a KBO. John Spencer, another New Horizons science team member from SwRI, said "This is all part of the excitement of exploring new places and seeing things never seen before."







KBOs are ancient remnants of the early days of the Solar System. Whereas the inner regions of the Solar System were largely swept clean as the planets formed, the Kuiper Belt remained mostly as it is, untouched by the gravity of the planets.



There are trillions of objects in this cold, distant part of the Solar System. The Kuiper Belt itself spans a distance that is 30 to 50 times greater than the distance from the Earth to the Sun. It's similar to the asteroid belt between Mars and Jupiter, but Kuiper Belt objects are icy, whereas asteroid belt objects are rocky, for the most part.



The New Horizons team has requested a mission extension, and if that extension is approved, the target is already chosen. In August 2015, NASA selected the KBO 2014 MU69, which resides in an orbit almost a billion miles beyond Pluto. There were two potential destinations for the spacecraft after it departed Pluto, and 2014 MU69 was recommended by the New Horizons team, and chosen by NASA.







Choosing New Horizons' next target early was important for fuel use. Fuel conservation allows the spacecraft to perform the maneuvers necessary to reach 2014 MU69. If all goes well, New Horizons should reach its next target by January 2019.



According to Alan Stern, New Horizons Principal Investigator, there are good reasons to visit 2014 MU69. “2014 MU69 is a great choice because it is just the kind of ancient KBO, formed where it orbits now, that the Decadal Survey desired us to fly by,” he said. “Moreover, this KBO costs less fuel to reach [than other candidate targets], leaving more fuel for the flyby, for ancillary science, and greater fuel reserves to protect against the unforeseen.”



The Decadal Survey in 2003 strongly recommended that flybys of Pluto and small KBOs should be conducted. The KBO is an unexplored region, and these flybys will allow us to sample the diversity of objects in the belt.



If New Horizons makes it to its next target, 2014 MU69, and delivers the types of results it has so far in its journey, it will be an unprecedented success. The kind of success that will make it harder and harder to be a curmudgeonly anti-space troll.



Wait. Who am I kidding.



Haters gonna hate.



The post New Horizons Sends Back First Science On Distant Kuiper Belt Object appeared first on Universe Today.

EARTH PLANET - What is the Closest Planet to Earth?

What is the Closest Planet to Earth?:

A common question when looking at the Solar System and Earth's place in the grand scheme of it is "which planet is closest to Earth?" Aside from satisfying a person's general curiosity, this question is also of great importance when it comes to space exploration. And as humanity contemplates mounting manned missions to neighboring planets, it also becomes one of immense practicality.



If, someday, we hope to explore, settle, and colonize other worlds, which would make for the shortest trip? Invariable, the answer is Venus. Often referred to as "Earth's Twin", Venus has many similarities to Earth. It is a terrestrial planet, it orbits within the Sun's habitable zone, and it has an atmosphere that is believed to have once been like Earth's. Combined with its proximity to us, its little wonder we consider it our twin.

Venus' Orbit:

Venus orbits the Sun at an average distance (semi-major axis) of 108,208,000 km (0.723 AUs), ranging between 107,477,000 km (0.718 AU) at perihelion and 108,939,000 km (0.728 AU) at aphelion. This makes Venus' orbit the least eccentric of all the planets in the Solar System. In fact, with an eccentricity of less than 0.01, its orbit is almost circular.







When Venus lies between Earth and the Sun, it experiences what is known as an inferior conjunction. It is at this point that it makes its closest approach to Earth (and that of any planet) with an average distance of 41 million km (25,476,219 mi). On average, Venus achieves an inferior conjunction with Earth every 584 days.



And because of the decreasing eccentricity of Earth's orbit, the minimum distances will become greater over the next tens of thousands of years. So not only is it Earth's closest neighbor (when it makes its closest approach), but it will continue to get cozier with us as time goes on!

Venus vs. Mars:

As Earth's other neighbor, Mars also has a "close" relationship with Earth. Orbiting our Sun at an average distance of 227,939,200 km (1.52 AU), Mars' highly eccentric orbit (0.0934) takes it from a distance of 206,700,000 km (1.38 AU) at perihelion to 249,200,000 km (1.666 AU) at aphelion. This makes its orbit one of the more eccentric in our Solar System, second only to Mercury



For Earth and Mars to be at their closest, both planets needs to be on the same side of the Sun, Mars needs to be at its closest distance from the Sun (perihelion), and Earth needs to be at its farthest (aphelion). This is known as opposition, a time when Mars appears as one of the brightest objects in the sky (as a red star), rivaling that of Venus or Jupiter.







But even at this point, the distance between Mars and Earth ranges considerably. The closest approach to take place occurred back in 2003, when Earth and Mars were only 56 million km (3,4796,787 mi) apart. And this was the closest they’d been in 50,000 years. The next closest approach will take place on July 27th, 20178, when Earth and Mars will be at a distance of 57.6 million km (35.8 mi) from each other.



It has also been estimated that the closest theoretical approach would take place at a distance of 54.6 million km (33.9 million mi). However, no such approach has been documented in all of recorded history. One would be forced to wonder then why so much of humanity's exploration efforts (past, present and future) are aimed at Mars. But when one considers just how horrible Venus' environment is in comparison, the answer becomes clear.

Exploration Efforts:

The study and exploration of Venus has been difficult over the years, owing to the combination of its dense atmosphere and harsh surface environment. Its surface has been imaged only in recent history, thanks to the development of radar imaging. However, many robotic spacecraft and even a few landers have made the journey and discovered much about Earth's closest neighbor.



The first attempts were made by the Soviets in the 1960s through the Venera Program. Whereas the first mission (Venera-1) failed due to loss of contact, the second (Venera-3) became the first man-made object to enter the atmosphere and strike the surface of another planet (on March 1st, 1966). This was followed by the Venera-4 spacecraft, which launched on June 12th, 1967, and reached the planet roughly four months later (on October 18th).







NASA conducted similar missions under the Mariner program. The Mariner 2 mission, which launched on December 14th, 1962, became the first successful interplanetary mission and passed within 34,833 km (21,644 mi) of Venus’ surface. Between the late 60s and mid 70s, NASA conducted  several more flybys using Mariner probes - such as the Mariner 5 mission on Oct. 19th, 1967 and the Mariner 10 mission on Feb. 5th, 1974.



The Soviets launched six more Venera probes between the late 60s and 1975, and four additional missions between the late 70s and early  80s. Venera-5, Venera-6, and Venera-7 all entered Venus' atmosphere and returned critical data to Earth. Venera 11 and Venera 12 detected Venusian electrical storms; and Venera 13 and Venera 14 landed on the planet and took the first color photographs of the surface. The program came to a close in October 1983, when Venera 15 and Venera 16 were placed in orbit to conduct mapping of the Venusian terrain with synthetic aperture radar.



By the late seventies, NASA commenced the Pioneer Venus Project, which consisted of two separate missions. The first was the Pioneer Venus Orbiter, which inserted into an elliptical orbit around Venus (Dec. 4th, 1978) to study its atmosphere and map the surface. The second, the Pioneer Venus Multiprobe, released four probes which entered the atmosphere on Dec. 9th, 1978, returning data on its composition, winds and heat fluxes.







In 1985, the Soviets participated in a collaborative venture with several European states to launch the Vega Program. This two-spacecraft initiative was intended to take advantage of the appearance of Halley’s Comet in the inner Solar System, and combine a mission to it with a flyby of Venus. While en route to Halley on June 11th and 15th, the two Vega spacecraft dropped Venera-style probes into Venus' atmosphere to map its weather.



NASA’s Magellan spacecraft was launched on May 4th, 1989, with a mission to map the surface of Venus with radar. In the course of its four and a half year mission, Magellan provided the most high-resolution images to date of the planet, was able to map 98% of the surface and 95% of its gravity field. In 1994, at the end of its mission, Magellan was sent to its destruction into the atmosphere of Venus to quantify its density.



Venus was observed by the Galileo and Cassini spacecraft during flybys on their respective missions to the outer planets, but Magellan was the last dedicated mission to Venus for over a decade. It was not until October of 2006 and June of 2007 that the MESSENGER probe would conduct a flyby of Venus (and collect data) in order to slow its trajectory for an eventual orbital insertion of Mercury.



The Venus Express, a probe designed and built by the European Space Agency, successfully assumed polar orbit around Venus on April 11th, 2006. This probe conducted a detailed study of the Venusian atmosphere and clouds, and discovered an ozone layer and a swirling double-vortex at the south pole before concluding its mission in December of 2014. Since December 7th, 2015, Japan's Akatsuki has been in a highly elliptical Venusian orbit.



https://youtu.be/oet63vzBvkg



Because of its hostile surface and atmospheric conditions, Venus has proven to be a tough nut to crack, despite its proximity to Earth. In spite of that, NASA, Roscosmos, and India's ISRO all have plans for sending additional missions to Venus in the coming years to learn more about our twin planet. And as the century progresses, and if certain people get their way, we may even attempt to send human colonists there!



We have written many articles about Earth and its closest neighbor here at Universe Today. Here's The Planet Venus, Venus: 50 Years Since Our First Trip, And We're Going Back, Interesting Facts About Venus, Exploring Venus By Airship, Colonizing Venus With Floating Cities, and How Do We Terraform Venus?



If you'd like more info on Earth, check out NASA's Solar System Exploration Guide on Earth. And here's a link to NASA's Earth Observatory.



Astronomy Cast also has an interesting episode on the subject. Listen here, Episode 50: Venus.

The post What is the Closest Planet to Earth? appeared first on Universe Today.

ORBITAL ATK Proposes Man-Tended Lunar-Orbit Outpost by 2020 for Link Up with NASA’s Orion

Orbital ATK Proposes Man-Tended Lunar-Orbit Outpost by 2020 for Link Up with NASA’s Orion:

Orbital ATK has unveiled a practical new proposal to build a near term man-tended outpost in lunar orbit that could launch by 2020 and be operational in time for a lunar link-up with NASA’s Orion crew module during its maiden mission, when American astronauts finally return to the Moon’s vicinity in 2021 - thus advancing America’s next giant leap in human exploration of deep space.



The intrepid offer by Orbital could be carried out rather quickly because it utilizes an evolved version of the company’s already proven commercial Cygnus space station resupply freighter as “the building block … in cislunar space,” said Frank DeMauro, Orbital ATK Vice President for Human Spaceflight Systems, in an exclusive interview with Universe Today. See an artist concept in the lead image.



“Our Cygnus spacecraft is the building block to become a vehicle for exploration beyond low Earth orbit,” Orbital ATK’s Frank DeMauro told Universe Today.



“We are all about supporting NASA’s Mission to Mars. We feel that getting experience in cislunar space is critical to the buildup of the capabilities to go to Mars."



NASA’s agency wide goal is to send astronauts on a ‘Journey to Mars’ in the 2030s - and expeditions to cislunar space in the 2020s serve as the vital ‘proving ground’ to fully develop, test out and validate the robustness of crucial technologies upon which the astronauts lives will depend on later Red Planet missions lasting some 2 to 3 years.



Orbital ATK’s lunar-orbit outpost proposal was announced at an official hearing of the US House of Representatives Subcommittee on Space on Wednesday, May 18, by former NASA Astronaut and Orbital ATK President of the Space Systems Group, Frank Culbertson.



“A lunar-orbit habitat will extend America’s leadership in space to the cislunar domain," said Orbital ATK President of the Space Systems Group, Frank Culbertson.



“A robust program to build, launch and operate this initial outpost would be built on NASA’s and our international partners’ experience gained in long-duration human space flight on the International Space Station and would make use of the agency’s new Space Launch System (SLS) and Orion deep-space transportation system.”



The idea is to assemble an initial crew-tended habitat with pressurized work and living volume for the astronauts based on a Cygnus derived vehicle, and have it pre-positioned and functioning in lunar-orbit by 2020.



As envisioned by Orbital ATK, the habitat would be visited during NASA’s first manned mission of SLS and Orion to the Moon known as Exploration Mission-2 (EM-2).



The three week long EM-2 lunar test flight could launch as early as August 2021 - if sufficient funding is available.



The goals of EM-2 and following missions could be significantly broadened via docking with a lunar outpost. And Orion mission durations could be extended to 60 days.



The initial lunar habitat envisioned by Orbital ATK would be comprised of two upgraded Cygnus pressurized vehicles - provisionally dubbed as Exploration Augmentation Modules (EAM). They would be attached to a multi-port docking module very similar in concept and design to the docking Nodes already flying in orbit as integral components of the ISS.









The lunar Cygnus vehicles would be upgraded from the enhanced cargo ships currently being manufactured and launched to the ISS.



“There are additional capabilities that we can put into the Cygnus module. We can make them longer and bigger so they can carry more logistics and carry more science,” DeMauro elaborated.



A variety of supplementary subsystems would also need to be enhanced.



“We looked at what systems we would need to modify to make it a long term habitation module. Since we would not be docked to the ISS, we would need our own Environmental Control and Life Support Systems (ECLSS) out at lunar orbit to support the crew.”



“The service module would also need to be improved due to the high radiation environment and the longer time.”



“We also need to look at the thermal protection subsystem, radiation protection subsystem and power subsystems to support the vehicle for many years as opposed to the short time spent at the ISS. More power is also needed to support more science. We also need a propulsion system to get to the Moon and maintain the vehicle.”



“All that work is getting looked at now - to determine what we need to modify and upgrade and how we would do all that work,” DaMauro told me.



The habitat components would be launched to the Moon on a commercial launch vehicle.



High on the list of candidate launchers would be the United Launch Alliance Atlas V rocket which recently already successfully delivered two Cygnus cargo ships to the ISS in Dec. 2015 and March 2016.



Other potential boosters include the ULA Delta IV and even ESA’s Ariane V as a way to potentially include international participation.













The habitat components could be manufactured and launched about three years after getting a ‘Go Ahead’ contract from NASA.



“Since many aspects of operations in deep space are as yet untested, confidence must be developed through repeated flights to, and relatively long-duration missions in, cislunar space,” says Culbertson.



“Orbital ATK continues to operate our Cygnus cargo logistics vehicle as a flagship product, so we are ready to quickly and affordably implement an initial Cygnus-derived habitat in cislunar space within three years of a go-ahead.”







Over time, the outpost could be expanded with additional habitat and research modules delivered by Orion/SLS, commercial or international rockets.



Cygnus is suitable for wide ranging science experiments and gear. It could also launch cubesats - like the current Cygnus berthed at the ISS is equipped with a cubesat deployer.



Potential lunar landers developed by international partners could dock at the cislunar habitats open docking ports.



“We are doing science now on Cygnus and we would expect to carry along science experiments on the new Cygnus vehicle. The vehicle is very attractive to science experiments,” DeMauro explained.



“There really is no limit to what the outpost could become.”







“What we put out is very exciting,” DeMauro noted.



“As a company we are looking forward to working in this arena. Our suggested plans are in line with where NASA wants to go. And we think we are the right company to play a big part in that!”



By incorporating commercial companies and leveraging the considerable technology development lessons learned from Cygnus, NASA should realize significant cost savings in implementing its human exploration strategy. Although Orbital ATK is not divulging a cost estimate for the lunar habitat at this time, the cost savings from a commercial partner should be considerable. And the 3 year time frame to launch is very attractive.



Orion is designed to send astronauts deeper into space than ever before, including missions to the Moon, asteroids and the Red Planet. Cygnus derived modules and/or other augmenting hardware components will be required to carry out any round trip human missions to the Martian surface.



NASA is now building the next Orion capsule at the Kennedy Space Center. It will launch unpiloted atop the first SLS rocket in late 2018 on the EM-1 mission.









Stay tuned here for Ken's continuing Earth and Planetary science and human spaceflight news.



Ken Kremer





The post Orbital ATK Proposes Man-Tended Lunar-Orbit Outpost by 2020 for Link Up with NASA’s Orion appeared first on Universe Today.

MARS PLANET - Hubble Telescope Zooms In On Mars

Hubble Telescope Zooms In On Mars:

We're in store for an exciting weekend as the Earth and Mars get closer to each other than at any time in the last ten years. To take advantage of this special opportunity, the Hubble Space Telescope, normally busy eyeing remote galaxies, was pointed at our next door neighbor to capture this lovely close-up image.

As Universe Today writer David Dickinson described in his excellent Mars guide, the planet reaches opposition on Sunday morning May 22. That's when the planet will be directly opposite the Sun in the sky and rise in the east around the same time the Sun sets in the west. Earth sits squarely in between. Opposition also marks the planet’s closest approach to Earth, so that Mars appears bigger and brighter in the sky than usual. A perfect time for detailed studies whether through both amateur and professional telescopes.







On May 12, Hubble took advantage of this favorable alignment and turned its gaze towards Mars to take an image of our rusty-hued neighbor, From this distance the telescope could see Martian features as small as 18.6 miles (30 kilometers) across. The image shows a sharp, natural-color view of Mars and reveals several prominent geological features, from smaller mountains and erosion channels to immense canyons and volcanoes.







The orange area in the center of the image is Arabia Terra, a vast upland region. The landscape is densely cratered and heavily eroded, indicating that it could be among the oldest features on the planet.







South of Arabia Terra, running east to west along the equator, is the long dark feature named Sinus Sabaeus that terminates in a larger, dark blob called and Sinus Meridiani. These darker regions are covered by bedrock from ancient lava flows and other volcanic features. An extended blanket of clouds can be seen over the southern polar cap where it's late winter. The icy northern polar cap has receded to a comparatively small size because it's now late summer in the northern hemisphere.







So the question now is how much will you see as we pull up alongside the Red Planet this weekend? With the naked eye, Mars looks like a fiery "star" in the head of Scorpius the scorpion not far from the similarly-colored Antares, the brightest star in the constellation. It's unmistakable. Even through the haze it caught my eye last night, rising in the southeast around 10 o'clock with its signature hue.



Through a 4-inch or larger telescope, you can see limb hazes/clouds and prominent dark features such as Syrtis Major, Utopia, clouds over Hellas, Mare Tyrrhenum (to the west of Syrtis Major) and Mare Cimmerium (west of M. Tyrrhenum).







These features observers across the America will see this week and early next between about 11 p.m. and 2 a.m. local time. As Mars rotation period is 37 minutes longer than Earth's, these markings will gradually rotate out of view, and we'll see the opposite hemisphere in the coming weeks. You can use the map to help you identify particular features or Sky & Telescope's handy Mars Profiler to know which side of the planet's visible when.







To top off all the good stuff happening with Mars, the Full Flower Moon will join up with that planet, Saturn and Antares Saturday night May 21 to create what I like to call a "diamond of celestial lights" visible all night. Don't miss it!



Italian astronomer Gianluca Masi will offer up two online Mars observing sessions in the coming week, on May 22 and 30, starting at 5 p.m. CDT (22:00 UT). Yet another opportunity to get acquainted with your inner Mars.

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JUPITER PLANET - How Long Does it Take Jupiter to Orbit the Sun?

How Long Does it Take Jupiter to Orbit the Sun?:

When it comes to the other planets that make up our Solar System, some pretty stark differences become apparent. In addition to being different in terms of their sizes, composition and atmospheres from Earth, they also differ considerably in terms of their orbits. Whereas those closest to the Sun have rapid transits, and therefore comparatively short years, those farther away can take many Earth to complete a single orbit.



This is certainly the case when it comes to Jupiter, the Solar System largest and most massive planet. Given its considerable distance from the Sun, Jupiter spends the equivalent of almost twelve Earth years completing a single circuit of our Sun. Orbiting at this distance is part of what allows Jupiter to maintain its gaseous nature, and led to its formation and peculiar composition.

Orbit and Resonance:

Jupiter orbits the Sun at an average distance (semi-major axis) of 778,299,000 km (5.2 AU), ranging from 740,550,000 km (4.95 AU) at perihelion and 816,040,000 km (5.455 AU) at aphelion. At this distance, Jupiter takes 11.8618 Earth years to complete a single orbit of the Sun. In other words, a single Jovian year lasts the equivalent of 4,332.59 Earth days.



https://youtu.be/pnHc_87A7_U



However, Jupiter's rotation is the fastest of all the Solar System's planets, completing a rotation on its axis in slightly less than ten hours (9 hours, 55 minutes and 30 seconds to be exact. Therefore, a single Jovian year lasts 10,475.8 Jovian solar days. This orbital period is two-fifths that of Saturn, which means that the two largest planets in our Solar System form a 5:2 orbital resonance.

Seasonal Changes:

With an axial tilt of just 3.13 degrees, Jupiter also has one of the least inclined orbits of any planet in the Solar System. Only Mercury and Venus have more vertical axes, with a tilt of 0.03° and 2.64° respectively. As a result, Jupiter does not experience seasonal changes the way the other planets do - particularly Earth (23.44°), Mars (25.19°) and Saturn (26.73°).



As a result, temperatures do not vary considerably between the northern or southern hemispheres during the course of its orbit. Measurements taken from the top of Jupiter’s clouds (which is considered to be the surface) indicate that surface temperatures vary between 165 K and 112 K (-108 °C and -161 °C). However, temperatures vary considerably due to depth, increasing drastically as one ventures closer to the core.

Formation:

Jupiter's composition and position in the Solar System are interrelated. According to Nebular Theory, the Sun and all the planets of our Solar System began as a giant cloud of molecular gas and dust (called a solar nebula). Then, about 4.57 billion years ago, something happened that caused the cloud to collapse, which could have been the result of anything from a passing star to shock waves from a supernova.







From this collapse, pockets of dust and gas began to collect into denser regions. As the denser regions pulled in more and more matter, conservation of momentum caused them to begin rotating, while increasing pressure caused them to heat up. Since temperatures across this protoplanetary disk were not uniform, this caused different materials to condense at different temperatures, leading to different types of planets forming.



The dividing line for the different planets in our solar system is known as the "Frost Line", a point in the Solar System beyond which volatiles (such as water, ammonia, methane, carbon dioxide and carbon monoxide) are able to exist in a frozen state. As a result, planets like Jupiter, which are located beyond the Frost Line, condensed out of denser materials first (like silicate rock and minerals), then were able to accumulate gases in a liquid state.



In addition to ensuring that Jupiter was able to become the massive gas giant it is today, its distance from the Sun is also what makes its orbital period much longer than that of Earth's.



We have written many articles about Jupiter here at Universe Today. Here's The Gas Giant Jupiter, Ten Interesting Facts About Jupiter, Jupiter Compared to Earth, How Long Does it Take to get to Jupiter?, Could We Terraform Jupiter?



If you'd like more information on Jupiter, check out Hubblesite's News Releases about Jupiter. And here's an article about Jupiter on the NASA Solar System Exploration Guide.



We have also recorded an episode of Astronomy Cast about Jupiter. You can listen here, Episode 56: Jupiter.

The post How Long Does it Take Jupiter to Orbit the Sun? appeared first on Universe Today.

UNIVERSE TODAY - SpaceX Calls In The Lawyers For 2018 Mars Shot

SpaceX Calls In The Lawyers For 2018 Mars Shot:

A manned mission to Mars is a hot topic in space, and has been for a long time. Most of the talk around it has centred on the required technology, astronaut durability, and the overall feasibility of the mission. But now, some of the talk is focussing on the legal framework behind such a mission.



In April 2016, SpaceX announced their plans for a 2018 mission to Mars. Though astronauts will not be part of the mission, several key technologies will be demonstrated. SpaceX's Dragon capsule will make the trip to Mars, and will conduct a powered, soft landing on the surface of the red planet. The capsule itself will be launched by another new piece of technology, SpaceX's Falcon Heavy rocket.



It's a fascinating development in space exploration; a private space company, in cooperation with NASA, making the trip to Mars with all of its own in-house technology. But above and beyond all of the technological challenges, there is the challenge of making the whole endeavour legal.



Though it's not widely known or talked about, there are legal implications to launching things into space. In the US, each and every launch by a private company has to have clearance from the Federal Aviation Administration (FAA).

That's because the US signed the Outer Space Treaty in 1969, a treaty that sets out the obligations and limitations to activities in space. The FAA has routinely given their ascent to commercial launches, but things may be starting to get a little tricky in space.



The most recent Humans To Mars Summit, a conference focussed on Mars missions and explorations, just wrapped up on May 19th. At that conference, George Nield, associate administrator for commercial space transportation at the FAA, addressed the issue. “That’ll be an FAA licensed launch as well,” said Nield of the SpaceX mission to Mars. “We’re already working with SpaceX on that mission," he added. "There are some interesting policy questions that have to do with the Outer Space Treaty,” said Nield.



The Outer Space Treaty was signed in 1967, and has some sway over space exploration and colonization. Though it gives wide latitude to governments that are exploring space, how it will affect commercial activity like resource exploitation, and installations like settlements in other planets, is not so clear.







According to Nield, the FAA is interested in Article VI of the treaty and how it might impact SpaceX's planned mission to Mars. Article VI states that all signees to the treaty “shall bear international responsibility for national activities in outer space, including the Moon and other celestial bodies, whether such activities are carried on by governmental agencies or by non-governmental entities.”



Article VI also says, "the activities of non-governmental entities in outer space, including the Moon and other celestial bodies, shall require authorization and continuing supervision by the appropriate State Party to the Treaty."



What this language means is that the US government itself will bear responsibility for the SpaceX Mars mission. Obviously, this kind of treaty obligation is important. There isn't exactly a huge list of private companies exploring space, but that will change as the years pass. It seems likely that the bulk of commercial space exploration and resource utilization will be centred in the US, so how the US deals with their treaty obligations will be of immense interest now and in the future.



The treaty itself is mostly focused on avoiding military activity in space. It prohibits things like weapons of mass destruction in space, and weapons testing or military bases on the Moon or other celestial bodies. The treaty also states that the Moon and other planets and bodies cannot be claimed by any nation, and that these and other bodies "are the common heritage of mankind." Good to know.



Taken as a whole, it's easy to see why the Treaty is important. Space can't become a free-for-all like Earth has been in the past. There has to be some kind of framework. “A government needs to oversee these non-governmental activities,” according to Nield.



There's another aspect to all of this. Governments routinely sign treaties, and then try to figure out ways around them, while hoping their rivals won't do the same. It's a sneaky, tactical business, because governments can't grossly ignore treaties, else the other co-signatories abandon said treaty completely. A case in point is last year's law, signed by the US Congress, which makes it legal for companies to mine asteroids. This law could be interpreted as violating the Treaty.







Governments can claim, for instance, that their activities are scientific rather than military. Geo-political influence depends greatly on projecting power. If one nation can project power into space, while claiming their activities are scientific rather than military, they will gain an edge over their rivals. Countries also seek to bend the rules of a treaty to satisfy their own interests, while preventing other countries from doing the same. Just look at history.



We're not in that type of territory yet. So far, no nation has had an opportunity to really violate the treaty, though the asteroid mining law passed by the US Congress comes close.



The SpaceX mission to Mars is a very important one, in terms of how the Outer Space Treaty will be tested and adhered to. More and more countries, and private companies, are becoming space-farers. The legality of increasingly complex missions in space, and the eventual human presence on the Moon and Mars, is a fascinating one not usually addressed by the space science community.



We in the space science community are primarily interested in technological advances, and in the frontiers of human knowledge. It might be time for us to start paying attention to the legal side of things. Space exploration could turn out to have an element of courtroom drama to it.

















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BEAUTIFUL HALO IN THE SKY - Halo from Atacama

Halo from Atacama:

Discover the cosmos! Each day a different image or photograph of our fascinating universe is featured, along with a brief explanation written by a professional astronomer.

2016 May 18

Halo from Atacama

Image Credit & Copyright: Yuri Beletsky (Carnegie Las Campanas Observatory, TWAN)


Explanation: Influenced by the strong Pacific El Nino, cloudy skies have more often come to Chile's high Atacama Desert this season, despite its reputation as an astronomer's paradise. Located in one of the driest, darkest places on planet Earth, domes of the region's twin 6.5 meter Magellan telescopes of Carnegie Las Campanas Observatory were closed on May 13. Still, a first quarter Moon and bright stars shine through in this panoramic night skyscape, the lunar disk surrounded by a beautiful, bright halo. The angular radius of the halo is 22 degrees. Not determined by the brightness or phase of the Moon itself, the angle is set by the hexagonal geometry of atmospheric ice crystals that reflect and refract the moonlight. On that night, the brilliant star just inside the halo's radius was really planet Jupiter. The brightest star flanking the halo to the far left is Canopus, with Arcturus on the halo's right.

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UFO ? Super Bright Fireball Spotted Across U.S. Northeast

Super Bright Fireball Spotted Across U.S. Northeast:

It came from outer space—literally! On Tuesday, May 17, 2016, the early morning sky briefly lit up with the brilliant flash of a fireball—that is, an extremely bright meteor—over much of eastern New England states and even parts of southeastern Canada.



The event, which occurred around 12:50 a.m. EDT (04:50 UTC), was reported by witnesses from Maine, New Hampshire, Massachusetts, Rhode Island, Connecticut, New York, Ontario, and Québec, and captured on several automated cameras like a webcam in Portsmouth, NH (seen above) and a police dashcam in Plattsburgh, NY (below).







The fireball appeared to be moving from southwest to northeast and for some witnesses created an audible sonic boom, heard (and felt) several minutes later.



See more videos of this event from local news stations WMTW and WGME (Maine) and WMUR (New Hampshire) and from the Ogunquit police department on Twitter.



Meteors are the result of debris in space rapidly entering Earth's upper atmosphere, compressing the air and causing it to quickly release energy in the form of heat and optical light. If the entering object is massive enough it may violently disintegrate during its fall, creating both light and sound. This particular meteor technically classifies as a bolide, due to its brightness, eruption, and visible fragmentation. Learn more about the various types of meteors here.



No reports of a meteorite impact at ground level have been made although I must assume there will be individuals who go on the hunt—meteorite fragments, especially those associated with witnessed events, can be quite valuable.







Did you witness the event or capture it on camera? Report your sighting of this or any other fireballs on the AMS site and be sure to send your fireball videos or images to the American Meteor Society here.



Source: American Meteor Society

The post Super Bright Fireball Spotted Across U.S. Northeast appeared first on Universe Today.

NASA IMAGE - The Orion Nebula in Visible and Infrared

The Orion Nebula in Visible and Infrared:

Discover the cosmos! Each day a different image or photograph of our fascinating universe is featured, along with a brief explanation written by a professional astronomer.

2016 May 17

The Orion Nebula in Visible and Infrared

Image Credit & Copyright: Infrared: NASA, Spitzer Space Telescope; Visible: Oliver Czernetz, Siding Spring Obs.


Explanation: The Great Nebula in Orion is a colorful place. Visible to the unaided eye, it appears as a small fuzzy patch in the constellation of Orion. Long exposure, multi-wavelength images like this, however, show the Orion Nebula to be a busy neighborhood of young stars, hot gas, and dark dust. This digital composite features not only three colors of visible light but four colors of infrared light taken by NASA's orbiting Spitzer Space Telescope as well. The power behind much of the Orion Nebula (M42) is the Trapezium - four of the brightest stars in the nebula. Many of the filamentary structures visible are actually shock waves - fronts where fast moving material encounters slow moving gas. The Orion Nebula spans about 40 light years and is located about 1500 light years away in the same spiral arm of our Galaxy as the Sun.

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Tomorrow's picture: halo everybody

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Messier 14 (M14) – the NGC 6402 Globular Cluster

Messier 14 (M14) – the NGC 6402 Globular Cluster:

Welcome back to Messier Monday! Today, in our ongoing tribute to Tammy Plotner, we take a look at the M14 globular cluster!





In the 18th century, French astronomer Charles Messier began cataloging all the “nebulous objects” he had come to find while searching the night sky. Having originally mistook these for comets, he compiled a list these objects in the hopes of preventing future astronomers from making the same mistake. In time, the list would include 100 objects, and would come to be known as the Messier Catalog to posterity.



One of these objects was the globular cluster which he would designate as M14. Located in the southern constellation Ophiuchus, this slightly elliptically-shaped stellar swarm contains several hundred thousand stars, a surprising number of which are variables. Despite these stars not being densely concentrated in the central region, this object is not hard to spot for amateur astronomers that are dedicated to their craft!

Description:

Located some 30,000 light years from Earth and measuring 100 light years in diameter, this globular cluster can be found in the southern Ophiuchus constellation, along with several other Messier Objects. Although it began its life some 13.5 billion years ago, it is far from being done changing. It is still shaking intracluster dust from its shoes.







What this means is that M14, like many globular clusters, contains a good deal of matter that it picked up during its many times orbiting the center of our Galaxy. According to studies done by N. Matsunaga (et al):

"Our goal is to search for emission from the cold dust within clusters. We detect diffuse emissions toward NGC 6402 and 2808, but the IRAS 100-micron maps show the presence of strong background radiation. They are likely emitted from the galactic cirrus, while we cannot rule out the possible association of a bump of emission with the cluster in the case of NGC 6402. Such short lifetime indicates some mechanism(s) are at work to remove the intracluster dust... (and) its impact on the chemical evolution of globular clusters."

Another thing that makes Messier 14 unusual is the presence of CH stars, such as the one that was discovered in 1997. CH stars are a very specific type of Population II carbon stars that can be identified by CH absorption bands in the spectra. Middle aged and metal poor, these underluminous suns are known to be binaries. Patrick Cote, the chief author of the research team that discovered the star, wrote in their research report to the American Astronomical Society:

"We report the discovery of a probable CH star in the core of the Galactic globular cluster M14 (=NGC 6402 = C1735-032), identified from an integrated-light spectrum of the cluster obtained with the MOS spectrograph on the Canada-France-Hawaii telescope. Both the star's location near the tip of the red giant branch in the cluster color-magnitude diagram and its radial velocity therefore argue for membership in M14. Since the intermediate-resolution MOS spectrum shows not only enhanced CH absorption but also strong Swan bands of C2, M14 joins Centaurus as the only globular clusters known to contain "classical" CH stars. Although evidence for its duplicity must await additional radial velocity measurements, the CH star in M14 is probably, like all field CH stars, a spectroscopic binary with a degenerate (white dwarf) secondary."

Messier 14 was also the site of a nova that appeared in 1938. However, it was not registered until 1964, when Amelia Wehlau of the University of Western Ontario surveyed a collection of photographic plates taken by Helen Sawyer Hogg between 1932 and 1963. NASA's Hubble Space Telescope (HST) took a look for the nova' remnants, too, planning for more than a decade to obtain images and spectra of this region.



The Hubble team, which was led by Bruce Margon of the University of Washington, used the European Space Agency's Faint Object Camera (FOC) onboard HST to observe space in the vicinity of the nova. As the indicated in the research paper - titled "Faint Camera Observations Of A Globular Cluster Nova Field":

"The results are tremendously encouraging not only with respect to locating the quiescent nova, but also as a preview of the use of HST cameras in crowded, faint regions such as globular clusters. It is already clear even from this preliminary stage of the analysis that we have learned much. The brightness today of the nova remnant must be considerably less than suggested by the ground-based data, which we now know to have summed at least five separate stars."

History of Observation:

M14 is one of the original discoveries of Charles Messier, who cataloged it on June 1st, 1764. In his notes, he wrote of the object:

"In the same night of June 1 to 2, 1764, I have discovered a new nebula in the garb which dresses the right arm of Ophiuchus; on the charts of Flamsteed it is situated on the parallel of the star Zeta Serpentis: that nebula is not considerable, its light is faint, yet it is seen well with an ordinary [non-achromatic] refractor of 3 feet and a half [FL]; it is round, and its diameter can be 2 minutes of arc; above it and very close to it is a small star of the nineth magnitude. I have employed for seeing this nebula nothing but the ordinary refractor of 3 feet & a half with which I have not noticed any star; maybe with a larger instrumentone could perceive one. I have determined the position of that nebula by its passage of the Meridian, comparing it with Gamma Ophiuchi, it has resulted for its right ascension 261d 18' 29", and for its declination 3d 5' 45" south. I have marked that nebula on the chart of the apparent path of the Comet which I have observed last year [the comet of 1769]."

But as usual, it was Admiral Smyth who historically recorded it best when he said:

"A large globular cluster of compressed minute stars, on the Serpent-bearer's left arm. This fine object is of a lucid white colour, and very nebulous in aspect; which may be partly owing to its being situated in a splendid field of stars, the lustre of which interferes with it. By diminishing the field under high powers, some of the brightest of these attendants are excluded, but the cluster loses its definition. It was discovered by Messier in 1764, and thus described: "A small nebula, no star; light faint; form round; and may be seen with a telescope 3 1/2 feet long." The mean apparent place is obtained by differentiation from Gamma Ophiuchi, from which it is south-by-west about 6deg 1/2, being nearly midway between Beta Scorpii and the tail of Aquila, and 16deg due south of Rasalague [Alpha Ophiuchi]. Sir William Herschel resolved this object in 1783, with his 20-foot reflector, and he thus entered it: "Extremely bright, round, easily resolvable; with [magnification] 300 I can see the stars. The heavens are pretty rich in stars of a certain size [magnitude, brightness], but they are larger [brighter] than those in the cluster, and easily to be distinguished from them. This cluster is considerably behind the scattered stars, as some of them are projected upon it." He afterwards added: "From the observations with the 20-foot telescope, which in 1791 and 1799 had the power of discering stars 75-80 times as far as the eye, the profundity of this cluster must be of the 900th order." "It resembles the 10th Connoissance des temps [M10], which probably would put on the same appearance as this, were it removed half its distance farther from us."

Locating Messier 14:

Because M14 is rather small and on the faint side for small optics, it isn't easy to find in binoculars or a finderscope. The best way to start is to identify Delta Ophiuchi and begin about a handspan east. If you have difficulty, try about one third the distance between Beta and Eta Ophiuchi. Because of its relative size, it will appear almost stellar - but if you look closely, you'll notice that it's a "star" that won't quite come to a sharp focus.



With a minimum of 10X magnification, you can easily see that Messier 14 is a deep sky object and it will appear "fuzzy" to smaller telescopes and begin resolution with aperture of around 6". Large telescopes can fully resolve this loosely structured globular and can even distinguish some ellipticity in its general shape.



Here are the quick facts to help you get started. And as always, we hope that you enjoy your observations!



Object Name: Messier 14

Alternative Designations: M14, NGC 6402

Object Type: Class VIII Globular Cluster

Constellation: Ophiuchus

Right Ascension: 17 : 37.6 (h:m)

Declination: -03 : 15 (deg:m)

Distance: 30.3 (kly)

Visual Brightness: 7.6 (mag)

Apparent Dimension: 11.0 (arc min)



We have written many interesting articles about Messier Objects here at Universe Today. Here’s Tammy Plotner’s Introduction to the Messier Objects, , M1 – The Crab Nebula, M8 – The Lagoon Nebula, and David Dickison’s articles on the 2013 and 2014 Messier Marathons.



Be to sure to check out our complete Messier Catalog. And for more information, check out the SEDS Messier Database.

The post Messier 14 (M14) – the NGC 6402 Globular Cluster appeared first on Universe Today.

NASA IMAGE - Clouds of the Carina Nebula

Clouds of the Carina Nebula:

Discover the cosmos! Each day a different image or photograph of our fascinating universe is featured, along with a brief explanation written by a professional astronomer.

2016 May 16

Clouds of the Carina Nebula

Image Credit & Copyright: John Ebersole


Explanation: What forms lurk in the mists of the Carina Nebula? The dark ominous figures are actually molecular clouds, knots of molecular gas and dust so thick they have become opaque. In comparison, however, these clouds are typically much less dense than Earth's atmosphere. Featured here is a detailed image of the core of the Carina Nebula, a part where both dark and colorful clouds of gas and dust are particularly prominent. The image was captured last month from Siding Spring Observatory in Australia. Although the nebula is predominantly composed of hydrogen gas -- here colored green, the image was assigned colors so that light emitted by trace amounts of sulfur and oxygen appear red and blue, respectively. The entire Carina Nebula, cataloged as NGC 3372, spans over 300 light years and lies about 7,500 light-years away in the constellation of Carina. Eta Carinae, the most energetic star in the nebula, was one of the brightest stars in the sky in the 1830s, but then faded dramatically.

Tomorrow's picture: colorful orion

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NASA IMAGE OF THE DAY - Stargazing From the International Space Station

Stargazing From the International Space Station: Astronauts aboard the International Space Station (ISS) see the world at night on every orbit — that’s 16 times each crew day. An astronaut took this broad, short-lens photograph of Earth’s night lights while looking out over the remote reaches of the central equatorial Pacific Ocean.

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Milky Way Over Quiver Tree Forest

Milky Way Over Quiver Tree Forest:

Discover the cosmos! Each day a different image or photograph of our fascinating universe is featured, along with a brief explanation written by a professional astronomer.

2016 May 15

Explanation: In front of a famous background of stars and galaxies lies some of Earth's more unusual trees. Known as quiver trees, they are actually succulent aloe plants that can grow to tree-like proportions. The quiver tree name is derived from the historical usefulness of their hollowed branches as dart holders. Occurring primarily in southern Africa, the trees pictured in the above 16-exposure composite are in Quiver Tree Forest located in southern Namibia. Some of the tallest quiver trees in the park are estimated to be about 300 years old. Behind the trees is light from the small town of Keetmanshoop, Namibia. Far in the distance, arching across the background, is the majestic central band of our Milky Way Galaxy. Even further in the distance, visible on the image left, are the Large and Small Magellanic Clouds, smaller satellite galaxies of the Milky Way that are prominent in the skies of Earth's southern hemisphere.

What Is The Strongest Force In The Universe?

What Is The Strongest Force In The Universe? (Synopsis):

“The world is the great gymnasium where we come to make ourselves strong.” -Swami Vivekananda

But what does it truly mean to be strong? We have four fundamental forces in the Universe: the strong, electromagnetic, weak and gravitational forces. You might think that, by virtue of its name, the strong force is the strongest one. And you’d be right, from a particular point of view: at the smallest distance scales, 10^-16 meters and below, no other force can overpower it.

Image credit: Sloan Digital Sky Survey, of IC 1101, the largest known individual galaxy in the Universe.

But under the right circumstances, each of the forces can shine. Up until recently, on the largest scales, we thought that gravitation — by and large the weakest of the forces — was the only force that mattered. And yet, when we look on the very largest scales, many billions of light years in size, even gravitation doesn’t win the day.

Image credit: NASA & ESA, of possible models of the expanding Universe.

There are four possible answers depending on how you look at the question. Come find out who’s the strongest of them all!

Why does gravity move at the speed of light?

Why does gravity move at the speed of light? (Synopsis):

“The fact that gravitational damping is measured at all is a strong indication that the propagation speed of gravity is not infinite.  If the calculational framework of general relativity is accepted, the damping can be used to calculate the speed, and the actual measurement confirms that the speed of gravity is equal to the speed of light to within 1%.” -Steve Carlip

According to General Relativity, the speed of gravity must be equal to the speed of light. Since gravitational radiation is massless, it therefore must propagate at c, or the speed of light in a vacuum. But given that the Earth orbits the Sun, if it were attracted to the Sun’s position some 8 minutes ago instead of its present position, the planetary orbits would disagree with what we observe!

Image credit: David Champion, Max Planck Institute for Radio Astronomy.

What, then, is the resolution to this? It turns out that in relativity itself, what we experience as gravitation is also dependent on both speed and changes in the gravitational field, both of which play a role. From observations of binary pulsars, a gravitationally lensed quasar and, most recently, direct gravitational waves themselves, we can constrain the speed of gravity to be very close to the speed of light, with remarkable precision.

The quasar QSO J0842+1835, whose path was gravitationally altered by Jupiter in 2002, allowing an indirect confirmation that the speed of gravity equals the speed of light. Image credit: Fomalont et al. (2000), ApJS 131, 95-183, via http://www.jive.nl/svlbi/vlbapls/J0842+1835.htm.

Come get the full story, only over on Forbes!