European Medicinal Leech “Hirudo medicinalis.” Sucker is on the right, blood-feeding mouth is on the left. (Encyclopedia of Life image by Pavla Tochorová)

These three specimens of “M. sestertia” in the collections of the National Museum of Natural History (dorsal, top, and ventral views shown here) were collected in 1936 in New Hampshire and incorrectly identified as a different species.

During the 19th century, when bloodletting represented America's premier medical theory, leeches were employed by physicians on a massive scale. This fancy 19th-century display jar from the Smithsonian's National Museum of American History was used by a pharmacist to highlight his supply of medicinal leeches. Elaborate presentation indicates the high value leeches held as a commodity during this time.

Smithsonian leech expert Anna Phillips collecting leeches in a wetland in Maryland. (Photo by T.R. Kahn)

Leeches for sale in the pet markets beside the Egyptian Bazaar, Sultanahmet, Istanbul. (Flickr photo by RStacker)

Radio astronomers have used a radio telescope network the size of the Earth to zoom in on a unique phenomenon in a distant galaxy: a jet activated by a star being consumed by a supermassive black hole as seen in center of galaxy Messier 106 above. The record-sharp observations reveal a compact and surprisingly slowly moving source of radio waves, with details published in a paper in the journal Monthly Notices of the Royal Astronomical Society.

The artist's impression below shows the remains of a star that came too close to a supermassive black hole. Extremely sharp observations of the event Swift J1644+57 with the radio telescope network EVN (European VLBI Network) have revealed a remarkably compact jet, shown here in yellow. 

The international team, led by Jun Yang (Onsala Space Observatory, Chalmers University of Technology, Sweden), studied the new-born jet in a source known as Swift J1644+57 with the European VLBI Network (EVN), an Earth-size radio telescope array.

When a star moves close to a supermassive black hole it can be disrupted violently. About half of the gas in the star is drawn towards the black hole and forms a disc around it. During this process, large amounts of gravitational energy are converted into electromagnetic radiation, creating a bright source visible at many different wavelengths.
One dramatic consequence is that some of the star's material, stripped from the star and collected around the black hole, can be ejected in extremely narrow beams of particles at speeds approaching the speed of light. These so-called relativistic jets produce strong emission at radio wavelengths.

The first known tidal disruption event that formed a relativistic jet was discovered in 2011 by the NASA satellite Swift. Initially identified by a bright flare in X-rays, the event was given the name Swift J1644+57. The source was traced to a distant galaxy, so far away that its light took around 3.9 billion years to reach Earth.

Jun Yang and his colleagues used the technique of very long baseline interferometry (VLBI), where a network of detectors separated by thousands of kilometres are combined into a single observatory, to make extremely high-precision measurements of the jet from Swift J1644+57.

Three years of extremely precise EVN measurements of the jet from Swift J1644+5734 show a very compact source with no signs of motion. Lower panel: false colour contour image of the jet (the ellipse in the lower left corner shows the size of an unresolved source). Upper panel: position measurement with dates. One microarcsecond is one 3 600 000 000th part of a degree. Image credit: EVN/JIVE/J. Yang. Click for a full size image

"Using the EVN telescope network we were able to measure the jet's position to a precision of 10 microarcseconds. That corresponds to the angular extent of a 2-Euro coin on the Moon as seen from Earth. These are some of the sharpest measurements ever made by radio telescopes", says Jun Yang.

Thanks to the amazing precision possible with the network of radio telescopes, the scientists were able to search for signs of motion in the jet, despite its huge distance.

"We looked for motion close to the light speed in the jet, so-called superluminal motion. Over our three years of observations such movement should have been clearly detectable. But our images reveal instead very compact and steady emission - there is no apparent motion", continues Jun Yang.

The results give important insights into what happens when a star is destroyed by a supermassive black hole, but also how newly launched jets behave in a pristine environment. Zsolt Paragi, Head of User Support at the Joint Institute for VLBI ERIC (JIVE) in Dwingeloo, Netherlands, and member of the team, explains why the jet appears to be so compact and stationary.

"Newly formed relativistic ejecta decelerate quickly as they interact with the interstellar medium in the galaxy. Besides, earlier studies suggest we may be seeing the jet at a very small angle. That could contribute to the apparent compactness", he says.

The record-sharp and extremely sensitive observations would not have been possible without the full power of the many radio telescopes of different sizes which together make up the EVN, explains Tao An from the Shanghai Astronomical Observatory, P.R. China.

"While the largest radio telescopes in the network contribute to the great sensitivity, the larger field of view provided by telescopes like the 25-m radio telescopes in Sheshan and Nanshan (China), and in Onsala (Sweden) played a crucial role in the investigation, allowing us to simultaneously observe Swift J1644+57 and a faint reference source," he says.
Swift J1644+57 is one of the first tidal disruption events to be studied in detail, and it won't be the last.

"Observations with the next generation of radio telescopes will tell us more about what actually happens when a star is eaten by a black hole - and how powerful jets form and evolve right next to black holes", explains Stefanie Komossa, astronomer at the Max Planck Institute for Radio Astronomy in Bonn, Germany.

"In the future, new, giant radio telescopes like FAST (Five hundred meter Aperture Spherical Telescope) and SKA (Square Kilometre Array) will allow us to make even more detailed observations of these extreme and exciting events," concludes Jun Yang.

The Daily Galaxy via Chalmers University

Image credit: ESA/S. Komossa/Beabudai Design

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An open letter a "manifesto" of sorts, framed and singed by many of the great scientists and minds of our century --from Stephen Hawking to Frank Drake, Lord Martin Rees, to Caltech's Kip Thorne shown above-- was published this past April 2016 (and posted below), outlining the philosophical foundations that inspired the Breakthrough Starshot project and the search for the answer to the seminal question of the 21st Century: "Are we alone in the universe?"

As all the world knows by now, Yuri Milner, the Russian billionaire Internet investor, and Stephen Hawking, the famed astrophysicist, have revealed plans for an interstellar mission, $100 million Breakthrough Starshot, that would launch chip-sized robotic probes at more than 25 percent the speed of light for 20-year journeys on the 25-trillion mile trip our nearest star system, Alpha Centauri.

A huge ground-based laser will push the swarms of "laser sails" (up to tens of thousands of probes per year) propelled by light from the sun toward their exotic destination. Light exerts very little pressure, but prior projects have already successfully tested a number of solar sails — spacecraft propelled by light from the sun. As a prelude to the journey, Starshot could launch interplanetary missions to explore unsolved mysteries of our solar system — driving "space-chips" to Mars in roughly 30 minutes, or to the potential life bearing habitats of Enceladus, Titan, and Europa.

Scientists estimate the orange dwarf Alpha Centauri B system is slightly older than our 4.6-billion-year old solar system at anywhere from 4.8 billion to 6.5 billion years old. If life on a planet or moon in the habitable zone of Alpha Centauri B evolved similarly as it did on Earth, then primitive forms of life could already have flourished there when the young Earth collided with a Mars-sized object, forming our moon.

Jonathan McDowell from the Harvard-Smithsonian Center for Astrophysics said that Starshot is humanity's best chance of reaching Alpha Centauri, but has several hurdles to surmount. "The trick is accelerating with the pressure of light to accelerate a big, thin film of plastic that's shiny and catches the laser light so it goes faster," he said. "That's been demonstrated by the Japanese in interplanetary space a couple of years ago, but no one's got it really fast and we're talking about putting something a thousand times faster than any human artifact has ever done." McDowell said that it could take a decade to get a spacecraft to accelerate with a light sail, and longer to adapt the technology for the Starshot nanocraft. "I think 10 years to get to demonstrating something accelerated with a laser light sail, but a generation to be able to do it for real to Alpha Centauri."

Harvard physics professor Abraham Loeb said that the Starshot project is made possible by recent advances in the miniaturization of electronics: "This method we're talking about was conceived as soon as the laser was invented … The problem back then was that people thought that they needed to take humans along," he explained. "The big technological advance over the past decades has been the miniaturization of electronics, smart electronics. It was all driven by the cellphone industry. If you look at an iPhone and strip it from the case and the human interface, you're left with smart electronics that weigh roughly a gram, much lighter than anything else to use."

Loeb said that Starshot will be able to rapidly explore the Solar System. "Just to give you an example, to get to Pluto it would take three days instead of the 9½ years it took New Horizons to get there. If we launch at a fifth of the speed of light, it'll get there the same week," he said.

The seminal "Open Letter,"  the Alpha Centauri Manifesto,  below, lays down the foundational thinking behind the Breakthrough project.

The story of humanity is a story of great leaps out of Africa, across oceans, to the skies and into space. Since Apollo 11's ‘moonshot', we have been sending our machines ahead of us to planets, comets, even interstellar space. A mature civilization, like a mature individual, must ask itself this question. Is humanity defined by its divisions, its problems, its passing needs and trends? Or do we have a shared face, turned outward to the Universe?

In 1990, Voyager 1 swiveled its camera and captured the ‘Pale Blue Dot' - an image of Earth from six billion kilometers away. It was a mirror held up to our planet - home of water, life, and minds. A reminder that we share something precious and rare. But how rare, exactly? The only life? The only minds?

For the last half-century, small groups of scientists have listened valiantly for signs of life in the vast silence. But for government, academia, and industry, cosmic questions are astronomically far down the list of priorities. And that lengthens the odds of finding answers. It is hard enough to comb the Universe from the edge of the Milky Way; harder still from the edge of the public consciousness.

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Yet millions are inspired by these ideas, whether they meet them in science or science fiction. Because the biggest questions of our existence are at stake. Are we the Universe's only child - our thoughts its only thoughts? Or do we have cosmic siblings - an interstellar family of intelligence? As Arthur C. Clarke said, “In either case the idea is quite staggering.”

That means the search for life is the ultimate ‘win-win' endeavor. All we have to do is take part. Today we have search tools far surpassing those of previous generations. Telescopes can pick out planets across thousands of light years. The magic of Moore's law lets our computers sift data orders of magnitude faster than older mainframes - and ever quicker each year.

These tools are now reaping a harvest of discoveries. In the last few years, astronomers and the Kepler Mission have discovered thousands of planets beyond our solar system. It now appears that most stars host a planetary system. Many of them have a planet similar in size to our own, basking in the ‘habitable zone' where the temperature permits liquid water. There are likely billions of earth-like worlds in our galaxy alone. And with instruments now or soon available, we have a chance of finding out if any of these planets are true Pale Blue Dots home to water, life, even minds.

There has never been a better moment for a large-scale international effort to find life in the Universe. As a civilization, we owe it to ourselves to commit time, resources, and passion to this quest.

But as well as a call to action, this is a call to thought. When we find the nearest exo-Earth, should we send a probe? Do we try to make contact with advanced civilizations? Who decides? Individuals, institutions, corporations, or states? Or can we as species - as a planet - think together?

Three years ago, Voyager 1 broke the sun's embrace and entered interstellar space. The 20th century will be remembered for our travels within the solar system. With cooperation and commitment, the present century will be the time when we graduate to the galactic scale, seek other forms of life, and so know more deeply who we are.

But with current rocket propulsion technology, it would take tens or hundreds of millennia to reach our neighboring star system, Alpha Centauri. The stars, it seems, have set strict bounds on human destiny. Until now. In the last decade and a half, rapid technological advances have opened up the possibility of light-powered space travel at a significant fraction of light speed. This involves a ground-based light beamer pushing ultra-light nanocrafts miniature space probes attached to lightsails to speeds of up to 100 million miles an hour. Such a system would allow a flyby mission to reach Alpha Centauri in just over 20 years from launch, and beam home images of possible planets, as well as other scientific data such as analysis of magnetic fields.

Breakthrough Starshot aims to demonstrate proof of concept for ultra-fast light-driven nanocrafts, and lay the foundations for a first launch to Alpha Centauri within the next generation. Along the way, the project could generate important supplementary benefits to astronomy, including solar system exploration and detection of Earth-crossing asteroids.

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January 2016 also saw ‘first light' for Breakthrough Listen, with observations marking the start of the 10-year effort announced in July 2015 at London's Royal Society by Yuri Milner, Stephen Hawking, Lord Martin Rees, Ann Druyan, and Frank Drake. Hundreds of hours of observations have taken place using the Green Bank Radio Telescope in West Virginia and Lick Observatory's Automated Planet Finder in Mt. Hamilton, California.

Breakthrough Listen is the largest ever scientific research program aimed at finding evidence of civilizations beyond Earth. The scope and power of the search are on an unprecedented scale: The program includes a survey of the 1,000,000 closest stars to Earth. It scans the center of our galaxy and the entire galactic plane. Beyond the Milky Way, it listens for messages from the 100 closest galaxies to ours.

The instruments used are among the world's most powerful. They are 50 times more sensitive than existing telescopes dedicated to the search for intelligence.

The radio surveys cover 10 times more of the sky than previous programs. They also cover at least 5 times more of the radio spectrum and do it 100 times faster. They are sensitive enough to hear a common aircraft radar transmitting to us from any of the 1000 nearest stars.

They are also carrying out the deepest and broadest ever search for optical laser transmissions. These spectroscopic searches are 1000 times more effective at finding laser signals than ordinary visible light surveys. They could detect a 100 watt laser (the energy of a normal household bulb) from 25 trillion miles away.

Breakthrough Listen is releasing the first batch of data for public access at the Breakthrough Initiatives website. Data from the Green Bank Telescope is also available to users of UC Berkeley's SETI@home software.

Observations made so far by Breakthrough Listen include most of the stars within 16 light years of Earth (including stars such as 51 Pegasi that are known to host extra-solar planets), and a sample of stars between 16 and 160 light years away. This included nearby sun-like and giant stars as well as numerous binary stars. The search also targeted around 40 of the nearest spiral galaxies, including members of the Maffei Group in the direction of the constellation Cassiopeia. Stars within 16 light years accessible only from the Southern Hemisphere, such as Alpha Centauri, will be observed by the end of the year with the Parkes Telescope.

This year's Observation Plan for all three telescopes has been published and can be found at breakthroughinitiatives.org/OpenDataSearch

The Daily Galaxy via breakthroughinitiatives.org

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"This is just the tip of the iceberg," says Andrew Glikson from The Australian National University (ANU). "We've only found evidence for 17 impacts older than 2.5 billion years, but there could have been hundreds. Asteroid strikes this big result in major tectonic shifts and extensive magma flows. They could have significantly affected the way the Earth evolved."

This May, 2016, scientists have found evidence of a huge asteroid 20 to 30 kilometers across that struck the what is today Australia, creating a 400 kilometer-wide impact zone after breaking in two moments before it slammed into the Earth. The impact crater has long since disappeared. But a team of Aussie geophysicists has found the twin scars of the impacts the largest impact zone ever found on Earth hidden deep in the earth's crust.

Tiny glass beads called spherules, found in north-western Australia were formed from vaporized material from the asteroid impact, said Glikson. “Large impacts like these may have had a far more significant role in the Earth's evolution than previously thought,” Glikson said.

The exact date of the impacts remains unclear. The surrounding rocks are 300 to 600 million years old, but evidence of the type left by other meteorite strikes is lacking. “It's a mystery we can't find an extinction event that matches these collisions. I have a suspicion the impact could be older than 300 million years,” he added.

“There are two huge deep domes in the crust, formed by the Earth's crust rebounding after the huge impacts, and bringing up rock from the mantle below,” Glikson said. The two impact zones total more than 400 kilometres across, in the Warburton Basin in Central Australia. They extend through the Earth's crust, which is about 30 kilometres thick in this area.

"The impact would have triggered earthquakes orders of magnitude greater than terrestrial earthquakes, it would have caused huge tsunamis and would have made cliffs crumble," said Glikson, from the ANU Planetary Institute. "Material from the impact would have spread worldwide. These spherules were found in sea floor sediments that date from 3.46 billion years ago."

About 3.8 to 3.9 billion years ago the moon was struck by numerous asteroids, which formed the craters, called mare, that are still visible from Earth "Exactly where this asteroid struck the earth remains a mystery," Glikson said. "Any craters from this time on Earth's surface have been obliterated by volcanic activity and tectonic movements."

Glikson and Arthur Hickman from Geological Survey of Western Australia found the glass beads in a drill core from Marble Bar, in north-western Australia, in some of the oldest known sediments on Earth. The sediment layer, which was originally on the ocean floor, was preserved between two volcanic layers, which enabled very precise dating of its origin.

Glikson has been searching for evidence of ancient impacts for more than 20 years and immediately suspected the glass beads originated from an asteroid strike. Subsequent testing found the levels of elements such as platinum, nickel and chromium matched those in asteroids. There may have been many more similar impacts, for which the evidence has not been found, said Glikson.

The Daily Galaxy via Australian National University

Image credit: Top of page with thanks to Shutterstock

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Jupiter watchers have long known that the giant planet's ever-present polar auroras thousands of times brighter and many times bigger than Earth are powered by both electrically charged particles from the Sun colliding with Jupiter's magnetic field and a separate interaction between Jupiter and one of its many moons, called Io. But there are also auroral explosions on Jupiter, or periods of dazzling brightening, similar to auroral storms on Earth, that no one could definitively trace back to either of those known causes.

In the aurora-making interaction of Jupiter and Io, volcanoes on the small moon blast clouds of electrically charged atoms (ions) and electrons into a region surrounding Jupiter that's permeated by the planet's powerful magnetic field, thousands of times stronger than Earth's. Rotating along with its rapidly spinning planet, the magnetic field drags the material from Io around with it, causing strong electric fields at Jupiter's poles. The acceleration of the ions and electrons produce intense auroras that shine in almost all parts of the electromagnetic spectrum but most brightly in high-energy bands, like ultraviolet light and X-rays, that are invisible to unaided human eyes.

Io is the only known place in the Solar System with volcanoes erupting extremely hot lava like that seen on Earth. Because of Io's low gravity, large volcanic eruptions produce an umbrella of debris that rises high into space. Such outbursts can send material hundreds of miles above the surface.

The recent eruptions resemble past events that spewed tens of cubic miles of lava over hundreds of square miles in a short period of time. All three events, including the largest, most powerful eruption of the trio on 29 August, 2013, were likely characterized by “curtains of fire," as lava blasted out of fissures perhaps several miles long.

The 29 August, 2013, outburst on Io shown below was among the largest ever observed on the most volcanically active body in the solar system. Infrared image taken by Gemini North telescope. Image credit: Katherine de Kleer, UC Berkeley.

The brightest eruption at a caldera named Rarog Patera, was calculated to have produced a 50 square-mile, 30ft thick lava flow, while another close to a caldera called Heno Patera, produced flows covering 120 square miles. Both were located in Io's southern hemisphere, near its limb, and were nearly gone when imaged five days later.

Now, new observations of the planet's extreme ultraviolet emissions show that bright explosions of Jupiter's aurora likely also get kicked off by the planet-moon interaction, not by solar activity. A new scientific paper about these observations by Tomoki Kimura of the Japan Aerospace Exploration Agency (JAXA), in Sagamihara, Kanagawa, Japan, and his colleagues, was published online today in Geophysical Research Letters, a journal of the American Geophysical Union.

Io produces about 100 times more lava each year than all the volcanoes on Earth. While Earth's volcanoes occur in localized hotspots like the "Ring of Fire" around the Pacific Ocean, Io's volcanoes are distributed all over its surface. A global magma ocean about 30 to 50 kilometers (20 to 30 miles) beneath Io's crust helps explain the moon's activity.

"It has been suggested that both the Earth and its moon may have had similar magma oceans billions of years ago at the time of their formation, but they have long since cooled," said Torrence Johnson, a former Galileo project scientist based at NASA's Jet Propulsion Laboratory in Pasadena, Calif. He was not directly involved in the study. "Io's volcanism informs us how volcanoes work and provides a window in time to styles of volcanic activity that may have occurred on the Earth and moon during their earliest history."

NASA's Voyager spacecraft discovered Io's volcanoes in 1979, making that moon the only body in the solar system other than Earth known to have active magma volcanoes. The energy for the volcanic activity comes from the squeezing and stretching of the moon by Jupiter's gravity as Io orbits the largest planet in the solar system.

Starting in January 2014, a telescope aboard the JAXA's Hisaki satellite, which focused on Jupiter for two months, recorded intermittent brightening of the giant planet's aurora. The telescope detected sudden flare-ups on days when the usual flow of charged particles from the Sun, known as the solar wind, was relatively weak.

Additional space and ground-based telescopes, including the Hubble Space Telescope, also viewed Jupiter during these lulls in the solar wind. Both Hisaki and Hubble witnessed explosions of the planet's aurora despite the solar wind's calm, suggesting that it's the Jupiter-Io interaction driving these explosions, not charged particles from the Sun, according to the new study. The new research does not address exactly what is happening in the Jovian magnetosphere to cause the temporary brightening of auroral explosions.

The Daily Galaxy via NASA/JPL and AGU

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Citizens of London in the UK, Düsseldorf in Germany, and Bern in Switzerland will soon be able to order packages, groceries and food and have it delivered by a self-driving robot. 

Starting in July, it's a test program by robot maker Starship Technologies (co-founded by Skype co-founders Ahti Heinla and Janus Friis), an Estonian startup who has partnered with several food and package delivery companies to make the program a reality. 

Currently the partners include London food delivery startup Pronto.co.uk, European food delivery company Just Eat, German package delivery firm Hermes and German retailer Metro Group. Read more...