Astronomers report the discovery of a black hole with 100,000 solar masses hiding in a gas cloud near the heart of the Milky Way, ranking it as the second largest black hole ever seen in our galaxy.
Credit: Tomoharu Oka/Keio University
A team of Japanese astronomers, using the ALMA telescope in Chile, has published evidence of an intermediate-mass black hole lying near the centre of our Milky Way galaxy. If confirmed, it would be the first such object of this size class in our galaxy, and the second largest black hole overall.
It is estimated that 100 million black holes lie scattered around the Milky Way – but most are relatively small, ranging in size from about five, to several tens of solar masses. Only 60 have been identified so far. The nearest of these stellar black holes is 3,500 light years away.
Above the "stellar" size class are "intermediate-mass" black holes, which (until now) have only been found in galaxies other than our own. These start at roughly 100 solar masses, with an upper limit of several hundred thousand.
At the extreme end of the scale is the class of objects known as "supermassive" black holes. These monsters – with millions to billions of solar masses – lie in the centre of almost all currently known massive galaxies. In the case of our own galaxy, scientists have observed a bright and very compact astronomical radio source that is believed to be a supermassive black hole with 4.3 million solar masses and is named Sagittarius A*. This is so huge that if placed in our own Solar System, it would almost swallow the planet Mercury. Orbiting Sagittarius A* is a B-type star called "Source 2", which hurtles around at the astonishing speed of 5,000 km/s (11,000,000 mph, or 1/60th the speed of light), making it one of the fastest known stars.
The new intermediate-mass black hole discovered by the team at Keio University, Tokyo, is thought to be 200 light years from Sagittarius A*; which is relatively close in astronomical terms. It is hidden within a toxic gas cloud of hydrogen cyanide and carbon monoxide – moving at wildly different speeds. Observations from the ALMA telescope showed that molecules in the cloud are being pulled around by immense gravitational forces. According to the researchers' computer models, the most likely cause is a black hole of around 100,000 solar masses. Further evidence was later provided when they detected radio waves, matching the characteristics of a black hole, being emitted from the centre of the cloud.
"This is the first detection of an intermediate-mass black hole candidate in the Milky Way galaxy," said Tomoharu Oka, an astronomer at Keio University and lead author of the study, which appears in Nature Astronomy. "This may be the second-largest black hole in the Milky Way after Sagittarius A*."
Oka says the newly-found black hole might be the core remnant of an ancient dwarf galaxy that was cannibalised during the formation of the Milky Way billions of years ago. In the future, he suggests it could fall into the core of the Milky Way and merge with Sagittarius A*. "It supports the merging scenario of supermassive black hole formation," he says.
Oka and his colleagues now plan to observe the surrounding gas cloud in multiple wavelengths of light. They are also investigating other compact clouds of molecular gas that may contain large black holes.
Astronomers have detected 15 repeating Fast Radio Bursts coming from FRB 121102, located in a dwarf galaxy about 3 billion light-years away from Earth. The researchers note that FRB 121102 is presently in a "heightened activity state, and follow-on observations are encouraged, particularly at higher radio frequencies".
Breakthrough Listen – a $100 million program to look for evidence of extraterrestrial communications in the Universe – is the most comprehensive and detailed search ever undertaken for artificial radio and optical signals beyond Earth. The project was started in January 2016 by Russian entrepreneur, venture capitalist and physicist Yuri Milner, as part of his Breakthrough Initiatives program, and is expected to continue for 10 years.
Astronomers are studying radio wave observations from Green Bank Observatory (West Virginia, USA), Parkes Observatory (New South Wales, Australia) and the Automated Planet Finder (California, USA). They have just announced the detection of 15 fast radio bursts (or FRBs) emanating from the mysterious "repeater" known as FRB 121102.
FRBs, are brief, bright pulses of radio emission from distant galaxies. First detected with the Parkes Telescope, FRBs have now been seen by several radio telescopes around the world. FRB 121102 was discovered on 2nd November 2012 (hence its name). In 2015, it was the first FRB seen to repeat, ruling out theories of the bursts' origins that involved the catastrophic destruction of the progenitor (at least in this particular instance). And in 2016, the repeater was the first FRB to have its location pinpointed with sufficient accuracy to allow its host galaxy to be identified. It is now confirmed to reside in a dwarf galaxy about 3 billion light years away from Earth.
Credit: Gemini Observatory/AURA/NSF/NRC
Attempts to understand the mechanism that generates FRBs have made this particular galaxy a target of ongoing monitoring campaigns by instruments around the world. Possible explanations for FRBs range from outbursts from rotating neutron stars with extremely strong magnetic fields, to more speculative ideas that they are directed energy sources used by extraterrestrial civilisations to power spacecraft.
In the early hours of Saturday, 26th August 2017, UC Berkeley's Dr. Vishal Gajjar observed the location of FRB 121102 using the Breakthrough Listen backend instrument at Green Bank Telescope in West Virginia. The instrument accumulated 400 TB of data on the object over a five hour observation of the entire 4 to 8 GHz frequency band. This huge dataset was searched for signatures of short pulses from the source over a broad range of frequencies, with a characteristic dispersion or delay as a function of frequency, caused by the presence of gas in space between us and the source. The distinctive shape that the dispersion imposes on the initial pulse is an indicator of the amount of material between us and the source, and hence an indicator of the distance to the host galaxy.
Analysis by Dr. Gajjar and his team revealed 15 new pulses from FRB 121102. As well as confirming that the source is in a newly active state, the high resolution of the data obtained by the Listen instrument will allow measurement of the properties of these mysterious bursts at a higher precision than ever possible before.
The observations also show, for the first time, that FRBs emit at higher frequencies (with the brightest emission occurring at around 7 GHz) than was previously observed. The extraordinary capabilities of the Listen backend, which can record several gigahertz of bandwidth at a time, split into billions of individual channels, enable a new view of the frequency spectrum of FRBs, and will shed additional light on the processes giving rise to FRB emission.
When the recently-detected pulses left their host galaxy, our Solar System was just two billion years old. Life on Earth was only single-celled organisms, and it would be another billion years before even the simplest multi-cellular life began to evolve. Whether or not FRBs eventually turn out to be signatures of extraterrestrial technology, Breakthrough Listen is helping to push the frontiers of a new and rapidly growing area of our understanding of the Universe.
These new results will be described in more detail by Dr. Gajjar in an upcoming scientific journal article.
Green Bank Telescope, West Virginia. By Geremia at English Wikipedia [Public domain], via Wikimedia Commons.
Astronomers using ESO's Very Large Telescope have produced the most detailed ever image of a star, the red supergiant Antares, and created the first map of surface motion on a star other than our Sun.
Credit: ESO/K. Ohnaka
Using the European Southern Observatory's (ESO's) Very Large Telescope, astronomers have produced the most detailed ever image of a star – the red supergiant Antares, which lies 550 light years from Earth and is the 15th brightest star in the night sky. They have also made the first map showing the velocities of material in the atmosphere of a star other than our Sun, revealing unexpected turbulence in Antares's huge extended atmosphere.
To the unaided eye, the bright star Antares shines with a strong red tint in the heart of the constellation of Scorpius (The Scorpion). It is a huge and comparatively cool red supergiant, only 12 million years old, but already in the late stages of its life on the way to becoming a supernova. It now has a mass about 12 times that of the Sun and a diameter 700 times larger. If placed in our Solar System, it would engulf the inner planets along with Jupiter and its atmosphere would even come close to reaching Saturn. Antares is thought to have ejected three solar masses of material during its life so far.
A team of astronomers, led by Keiichi Ohnaka from the Universidad Católica del Norte in Chile, has now used ESO's Very Large Telescope Interferometer (VLTI) at the Paranal Observatory in Chile to map Antares's surface and measure the motions of its surface material. This is the best ever image of the surface and atmosphere of any star other than our Sun. The VLTI is a unique facility, able to combine the light from up to four telescopes to create a "virtual" telescope equivalent to a single mirror up to 200m (656 ft) across. This allows it to resolve fine details, far beyond what can be seen with a single telescope alone.
"How stars like Antares lose mass so quickly in the final phase of their evolution has been a problem for over half a century," said Ohnaka, who is also the lead author of a paper on the study. "The VLTI is the only facility that can directly measure the gas motions in the extended atmosphere of Antares – a crucial step towards clarifying this problem. The next challenge is to identify what's driving the turbulent motions."
Using the new results, the team has created the first two-dimensional velocity map of the atmosphere of a star other than the Sun. They did this using the VLTI with three of the Auxiliary Telescopes and an instrument called AMBER to make separate images of the surface of Antares over a small range of infrared wavelengths. They then used these data to calculate the difference between the speed of the atmospheric gas at different positions on the star and the average speed over the entire star. This resulted in a map of the relative speed of atmospheric gas across the entire disc of Antares – the first ever created for a star other than our Sun.
The astronomers found turbulent, low-density gas much further from the star than predicted, and concluded that the movement could not result from convection; that is, from large-scale movement of matter which transfers energy from the core to the outer atmosphere of many stars. They reason that a new, currently unknown, process may be needed to explain these movements in the extended atmospheres of red supergiants like Antares.
"In the future, this observing technique can be applied to different types of stars to study their surfaces and atmospheres in unprecedented detail," concludes Ohnaka. "Our work brings stellar astrophysics to a new dimension and opens an entirely new window to observe stars."
The team's work is published in the journal Nature.
If the potential for intelligent life to exist somewhere in the universe is so large, then where is everybody? In a new paper, an astrophysicist argues that species such as ours go extinct soon after attaining high levels of technology.
Credit: T.A.Rector and B.A.Wolpa/NOAO/AURA/NSF
The universe is incomprehensibly vast, with billions of other planets circling billions of other stars. The potential for intelligent life to exist somewhere out there should be enormous.
So, where is everybody?
That's the Fermi paradox in a nutshell. Daniel Whitmire, a retired astrophysicist who teaches mathematics at the University of Arkansas, once thought the cosmic silence indicated we as a species lagged far behind.
"I taught astronomy for 37 years," he says. "I used to tell my students that by statistics, we have to be the dumbest guys in the galaxy. After all we have only been technological for about 100 years while other civilisations could be more technologically advanced than us by millions or billions of years."
Recently, however, he's changed his mind. By applying a statistical concept called the principle of mediocrity – the idea that in the absence of any evidence to the contrary, we should consider ourselves typical, rather than atypical – Whitmire has concluded that instead of lagging behind, our species may be average. That's not good news.
In a paper published this month in the International Journal of Astrobiology, Whitmire argues that if we are typical, it follows that species such as ours go extinct soon after attaining technological knowledge.
This argument is based on two observations: (1) We are the first technological species to evolve on Earth, and (2) We are early in our technological development. (He defines "technological" as a biological species that has developed electronic devices and can significantly alter the planet.)
The first observation seems obvious, but as Whitmire notes in his paper, researchers believe the Earth should be habitable for animal life for at least another billion years into the future. Based on how long it took proto-primates to evolve into a technological species, that leaves enough time for it to happen again up to 23 times. On that time scale, there could have been others before us, but there's nothing in the geologic record to indicate we weren't the first: "We'd leave a heck of a fingerprint if we disappeared overnight," Whitmire notes.
By Whitmire's definition we became "technological" after the Industrial Revolution and the invention of radio, or roughly 100 years ago. According to the principle of mediocrity, a bell curve of the ages of all extant technological civilisations in the universe would put us in the middle 95%. In other words, technological civilisations that last millions of years, or longer, would be highly atypical. Since we are first, other typical technological civilisations should also be first. The principle of mediocrity allows no second acts. The implication is that once species become technological, they flame out and take the biosphere with them.
Whitmire argues that the principle holds for two standard deviations, or in this case about 200 years. But because the distribution of ages on a bell curve skews older (there is no absolute upper limit, but the age can't be less than zero), he doubles that figure and comes up with 500 years, give or take. Assuming a bell-shaped curve is not absolutely necessary – other assumptions give roughly similar results.
There's always the possibility that we are atypical and our species' lifespan will fall somewhere in the outlying 5% of the bell curve. If that's the case, we're back to the nugget of wisdom Whitmire taught his astronomy students for more than three decades.
"If we're not typical, then my initial observation would be correct," he said. "We would be the dumbest guys in the galaxy by the numbers."
An international team of astronomers has found that four Earth-sized planets orbit the nearest Sun-like star, Tau Ceti, which lies 12 light years away and is visible to the naked eye. These planets have masses as low as 1.7 Earth mass, making them among the smallest planets ever to be detected around G-type stars near our Solar System. Two are super-Earths located in the habitable zone, meaning they could support liquid surface water.
The planets were detected by observing tiny wobbles in the movement of Tau Ceti. This required techniques sensitive enough to detect variations in the movement of the star as small as 30 centimetres (12 inches) per second.
"We are now finally crossing a threshold where, through very sophisticated modelling of large combined data sets, we can disentangle the noise due to stellar surface activity from very tiny signals generated by the gravitational tugs of Earth-sized orbiting planets," said the study co-author, Steven Vogt, Professor of Astronomy and Astrophysics at the University of California, Santa Cruz.
Illustration courtesy of Fabo Feng
According to lead author Fabo Feng at the University of Hertfordshire, UK, researchers are now tantalisingly close to the 10-centimetre-per-second limit required for detecting Earth analogues: "Our detection of such weak wobbles is a milestone in the search for Earth analogues and the understanding of the Earth's habitability through comparison with these analogues," said Feng. "We have introduced new methods to remove the noise in the data in order to reveal the weak planetary signals."
As shown in the diagram above, the outer two planets around Tau Ceti are likely to be candidate habitable worlds – although a massive debris disc around the star probably reduces their habitability, due to intensive bombardment by asteroids and comets.
The same team also investigated Tau Ceti in 2013, when co-author Mikko Tuomi from the University of Hertfordshire led an effort in developing data analysis techniques and using the star as a benchmark case: "We came up with an ingenious way of telling the difference between signals caused by planets and those caused by a star's activity," he explains. "We realised that we could see how a star's activity differed at different wavelengths and use that information to separate this activity from signals of planets."
The team painstakingly improved the sensitivity of their method and were able to rule out two signals they had identified in 2013 as planets: "But no matter how we look at the star, there seem to be at least four rocky planets orbiting it," Tuomi says. "We are slowly learning to tell the difference between wobbles caused by planets, and those caused by stellar active surface. This enabled us to essentially verify the existence of the two outer, potentially habitable planets in the system."
Sun-like stars are thought to be the best targets in the search for habitable Earth-like planets, due to their similarity to our Sun. Unlike more common smaller stars, such as the red dwarf stars Proxima Centauri and Trappist-1, they are not so faint that planets would be tidally locked, showing the same side to the star at all times. Tau Ceti is very similar to the Sun in its size and brightness, and both stars host multi-planet systems.
A paper on these new findings was accepted for publication in the peer-reviewed Astronomical Journal and is available online. The data was obtained by using the HARPS spectrograph (European Southern Observatory, Chile) and Keck-HIRES (W. M. Keck Observatory, Mauna Kea, Hawaii).
The Sun (left) and Tau Ceti (right). Both are G-type stars.
Credit: R.J. Hall [CC-BY-SA-3.0], via Wikimedia Commons
Astronomers have announced the surprise detection of a large rock, possibly up to 93 m (305 ft) in size, which hurtled past Earth last week.
Images courtesy of the Minor Planet Center. The green line indicates the object's apparent motion relative to the Earth, and the bright green dots are the object's location at approximately one hour intervals. The Moon's orbit is grey. The blue arrow points in the direction of Earth's motion and the yellow arrow points toward the Sun.
At just one-third the Earth-moon distance, or 76,448 mi (123,031 km), the asteroid now named 2017 OO1 came within a whisker – in astronomical terms – of colliding with our planet. The object flew by at 23,200 mph (10.3 km/s) on 21st July at 03:33 UTC. However, it was only detected by the ATLAS-MLO telescope in Hawaii on 23rd July, two days after its closest approach. The object, with a very faint magnitude of 17.9, is very dark and likely to have a non-reflective surface that made it very difficult to spot.
While asteroids of this size are too small to cause an extinction-level event, their speed and kinetic energy can still do enormous damage. Inputting the figures into an impact calculator shows that 2017 OO1 would enter our atmosphere with a force equivalent to 11.6 megatons of TNT. Breaking up at an altitude of 29.3 mi (47.1 km), it would hit the ground at 13,400 mph (6 km/s), with a blast of 3.32 megatons. That is over 200 times more powerful than the Hiroshima bomb of 1945.
If on land, the impactor would produce a crater with radius of 2,132 ft (650 m) and depth of 820 ft (250 m). All buildings and most bridges within a radius of 1.6 mi (2.5 km) would be destroyed, with glass shattering up to 31 mi (50 km) away. If landing in the ocean, a megatsunami would be produced with waves of up to 500 ft (150 m) within a radius of 1 mile (1.6 km). These would decrease rapidly in height, to 62 ft (19 m) at a distance of 6.2 mi (10 km) but would have enough momentum to continue at 7 ft (2 m) height for over 62 mi (100 km).
We may sometimes joke and make light of such catastrophes – they are a popular staple of science fiction. But asteroids can also be very real, as the Chelyabinsk event of 2013 made clear. That involved a rock that was much smaller than 2017 OO1, with only 1/7th as much energy. It is surely only a matter of time before such an incident occurs again somewhere in the world; perhaps in a major urban region. Indeed, the B612 Foundation showed in a presentation that asteroid impacts are more common than previously thought. Over 10,000 near-Earth objects have been discovered to date, of which nearly ten percent are larger than 3,280 ft (1,000 m). There are possibly ten times as many still waiting to be found within our Solar System.
In related news, NASA will be using its network of observatories and scientists to track and characterise a small asteroid known as TC4 that will pass close to Earth on 12th October. Yesterday the agency provided more details of the initiative, which aims to test its worldwide asteroid detection and tracking abilities – assessing the capability of scientists to work together in response to a potential real asteroid threat.
"Asteroids," Neil deGrasse Tyson once tweeted, "are nature's way of asking: 'How's that space program coming along?'"
Astrophysicists report that tardigrade micro-animals may be one of the most resilient lifeforms on Earth, able to withstand global mass extinctions due to astrophysical events, such as supernovae, gamma-ray bursts, large asteroid impacts, and passing-by stars.
The world's most indestructible species, the tardigrade – an eight-legged micro-animal, also known as the water bear – will survive until the Sun dies, according to a new collaboration between Harvard and Oxford University.
Although much attention has been given to the potential impact of astrophysical events on human life, very little has been published about what it would take to kill the tardigrade and wipe out life on our planet. The new research implies that life will persist for as long as the Sun continues to shine. It also reveals that once life emerges, it is surprisingly resilient and difficult to destroy, boosting the odds of life on other planets.
The study, published in Scientific Reports, shows that the tiny creatures will survive the risk of extinction from all astrophysical catastrophes, and be around for billions of years – far longer than the human race.
Tardigrades are the toughest, most resilient animals on Earth – able to survive for up to 30 years without food or water, and endure temperature extremes of up to 150 degrees Celsius, the deep sea and even the frozen vacuum of space. The water-dwelling micro animal is only 0.5mm (0.02 inches) in size, but can live for up to 60 years. Researchers from the Universities of Oxford and Harvard concluded that they could most likely survive all astrophysical calamities.
Three potential events were considered as part of their research:
There are only a dozen known asteroids and dwarf planets with enough mass to boil the oceans (2x10^18 kg), these include Vesta (2x10^20 kg) and Pluto (10^22 kg). However, none of these objects will intersect the Earth's orbit and pose a threat to tardigrades.
In order to boil the oceans, an exploding star would need to be 0.14 light years away. The closest star to the Sun is 4.2 light years away and the probability of a massive star exploding close enough to Earth to kill all lifeforms on it, within the Sun's lifetime, is negligible.
Gamma-ray bursts are brighter and rarer than supernovae. Much like supernovas, gamma-ray bursts are too far away from Earth to be considered a viable threat. To boil the world's oceans, the burst would need to be within 40 light years, and the likelihood of a burst occurring so close is again, minor.
Gamma-ray burst. Credit: NASA
"Without our technology protecting us, humans are a very sensitive species," said Dr Rafael Alves Batista, Co-author and Post-Doctoral Research Associate in the Department of Physics at Oxford University. "Subtle changes in our environment impact us dramatically. There are many more resilient species on Earth. Life on this planet can continue long after humans are gone. Tardigrades are as close to indestructible as it gets on Earth, but it is possible that there are other resilient species examples elsewhere in the universe. In this context, there is a real case for looking for life on Mars and in other areas of the Solar System in general. If Tardigrades are Earth's most resilient species, who knows what else is out there?"
"A lot of previous work has focused on 'doomsday' scenarios on Earth – astrophysical events like supernovae that could wipe out the human race," explains Dr David Sloan, co-author from the same department at Oxford University. "Our study instead considered the hardiest species – the tardigrade. As we are now entering a stage of astronomy where we have seen exoplanets and are hoping to soon perform spectroscopy, looking for signatures of life, we should try to see just how fragile this hardiest life is. To our surprise we found that although nearby supernovae or large asteroid impacts would be catastrophic for people, tardigrades could be unaffected. Therefore it seems that life, once it gets going, is hard to wipe out entirely. Huge numbers of species, or even entire genera may become extinct, but life as a whole will go on."
In highlighting the resilience of life in general, the research broadens the scope of life beyond Earth, within and beyond the Solar System.
"It is difficult to eliminate all forms of life from a habitable planet," explains Professor Abraham Loeb, co-author and chair of the Astronomy department at Harvard University. "The history of Mars indicates that it once had an atmosphere that could have supported life, albeit under extreme conditions. Organisms with similar tolerances to radiation and temperature as tardigrades could survive long-term below the surface in these conditions. The subsurface oceans that are believed to exist on Europa and Enceladus would have conditions similar to the deep oceans of Earth where tardigrades are found, volcanic vents providing heat in an environment devoid of light. The discovery of extremophiles in such locations would be a significant step forward in bracketing the range of conditions for life to exist on planets around other stars."
Luxembourg yesterday passed a draft law on the exploration and use of space resources. The Grand Duchy is thus the first European country to offer a legal framework ensuring that private operators can be confident about their rights on resources they extract in space.
The new law – approved by a majority of 55 votes against two – will come into force on 1st August 2017. Its first article provides that space resources are capable of being owned. It also establishes the procedures for authorising and supervising space exploration missions.
This legal and regulatory framework is a key part of the SpaceResources.lu initiative, whose goal is to support the long-term economic development of new, innovative activities in the space industry. Within this strategy, Luxembourg has already begun to support research and development projects of leading players in the space mining industry that have set up their European operations in Luxembourg. For example, US firms Deep Space Industries and Planetary Resources both have subsidiaries there now; the latter finalised a 25 million euro agreement last year to accelerate the company's technical advancements, with the aim of launching a first commercial asteroid mission by 2020.
It is hoped that the SpaceResources.lu initiative can build on the experience Luxembourg has gained in sectors that are closely related to space mining, and in particular on its strong track record in the satellite sector. In 1985, a public-private partnership effort launched Société Européenne des Satellites, today known as the largest global satellite operator SES with its headquarters in Luxembourg. This now controls more than 50 satellites.
Deputy Prime Minister, Étienne Schneider, said: "Luxembourg is the first adopter in Europe of a legal and regulatory framework recognising that space resources are capable of being owned by private companies. The Grand Duchy thus reinforces its position as a European hub for the exploration and use of space resources. The legal framework is part of the expertise ecosystem and the business-friendly, innovation-nurturing environment that Luxembourg is offering to space industry companies. By adopting almost unanimously the respective draft law, the Luxembourg Parliament confirmed the strong political cross-party and national commitment to the SpaceResources.lu initiative."
“Luxembourg continues to be a strong partner and a global leader,” said Chris Lewicki, Planetary Resources CEO. “They are genuinely forward thinking, have a proven record in the satellite industry, and are making their mark on the space mining industry. The passage of this law is further proof of that.”
Alongside steps taken on the national level within the SpaceResources.lu initiative, Luxembourg continues to promote international cooperation in order to make progress on a future governance scheme and a global regulatory framework for space mining. In line with this, the Grand Duchy recently signed a joint statement with the European Space Agency (ESA) on future activities concerning missions to asteroids, related technologies and space resources exploration and utilisation. Luxembourg and the ESA agreed on the opportunity to further study technical and scientific aspects of space resources.
In April, a report by Goldman Sachs revealed that asteroid mining is “more realistic than perceived” – thanks to the falling costs of access to space – and is likely to bring enormous rewards to companies able to develop the necessary technologies for extraction. A single 500-metre-wide asteroid could contain nearly 175 times the global output of platinum.
The discovery of the smallest star able to sustain nuclear fusion has been announced; its diameter is just slightly larger than that of Saturn.
Images and text credit: University of Cambridge, Wikimedia Creative Commons license, Attribution 4.0 International (CC BY 4.0)
The smallest star yet measured has been discovered by a team of astronomers led by the University of Cambridge. With a diameter just slightly larger than that of Saturn, the gravitational pull at its stellar surface is about 300 times stronger than what humans feel on Earth. With just enough mass to enable the fusion of hydrogen nuclei into helium, it is likely as small as stars can possibly become. If it were any smaller, the pressure at its centre would no longer be sufficient to enable this process to take place. Hydrogen fusion is also what powers the Sun, and scientists are attempting to replicate it as a powerful energy source here on Earth.
Very small and dim stars like this one are also the best possible candidates for detecting Earth-sized planets with liquid water on their surfaces, such as TRAPPIST-1, an ultracool dwarf surrounded by seven temperate Earth-sized worlds.
The newly-found star – EBLM J0555-57Ab – is about 600 light years away in the constellation Pictor, in the direction of the Large Magellanic Cloud. It is part of a binary system, and was identified as it passed in front of its much larger companion, a method normally used to detect planets, not stars.
EBLM J0555-57 binary system, imaged by ESO’s La Silla Observatory. Credit: Alexander von Boetticher et al.
“Our discovery reveals how small stars can be,” said Alexander Boetticher, the lead author of the study, and a Master’s student at Cambridge’s Cavendish Laboratory and Institute of Astronomy. “Had this star formed with only a slightly lower mass, the fusion reaction of hydrogen in its core could not be sustained, and the star would instead have transformed into a brown dwarf.”
EBLM J0555-57Ab was identified using data from the Wide Angle Search for Planets (WASP), an experiment run by the Universities of Keele, Warwick, Leicester and St Andrews. It was found to circle its primary star companion with an orbital period of just 7.8 days, and has a mass of 85 Jupiters.
“This star is smaller, and likely colder than many of the gas giant exoplanets that have so far been identified,” said Boetticher. “While a fascinating feature of stellar physics, it is often harder to measure the size of such dim low-mass stars than for many of the larger planets. Thankfully, we can find these small stars with planet-hunting equipment, when they orbit a larger host star in a binary system. It might sound incredible, but finding a star can at times be harder than finding a planet.”
Despite being the most numerous stars in the Universe, stars with sizes and masses less than 20% that of our Sun are poorly understood, since they are difficult to detect. The EBLM project, which identified the star in this study, aims to plug that gap in knowledge: “Thanks to the EBLM project, we will achieve a far greater understanding of the planets orbiting the most common stars that exist; planets like those orbiting TRAPPIST-1,” said co-author Prof. Didier Queloz of Cambridge's Cavendish Laboratory. The team's work is published in the journal Astronomy & Astrophysics.
The European Space Agency (ESA) has confirmed the Laser Interferometer Space Antenna (LISA) as the third large-class mission in its future science programme, with launch planned for 2034.
A trio of satellites to detect gravitational waves has been selected as the third large-class (L3) mission in ESA's Science programme. In terms of its area and dimensions covered, the Laser Interferometer Space Antenna (LISA) will be the largest man-made structure ever put into space – with each "side" of its triangle stretching across millions of kilometres – forming a giant observatory to probe the Dark Side of the Universe.
In 2013, the "gravitational universe" was chosen as the theme for a future ESA mission. This would be designed to search for ripples in the fabric of space-time created by celestial objects with extremely strong gravity, such as pairs of merging black holes.
Gravitational waves were predicted a century ago by Albert Einstein's general theory of relativity, but remained elusive until very recently, when the first direct detection was made by the ground-based Laser Interferometer Gravitational-Wave Observatory (LIGO). That signal, announced in February 2016, was triggered by the merging of two black holes some 1.3 billion light-years away.
Since then, two more events have been detected and a follow-up study, LISA Pathfinder, has demonstrated that observations can be made in space – not just with ground-based instruments. This precursor mission will conclude on 30th June, after sixteen months of science operations, which have tested key technologies needed for the more advanced LISA in the 2030s.
Space-based operations will provide major advantages:
• no need to create an artificial vacuum, since the vacuum of space is free and better than anything that can be simulated in a lab;
• no interference from seismic noise, such as earthquakes or plate tectonics, passing vehicles and other human activity;
• no limitations in size for the observatory arms, which would otherwise be restricted by the curvature of the Earth.
To detect and measure gravitational waves from distant astronomical sources, a phenomenal level of sensitivity is required. Using laser interferometry over its trio of 2.5 million kilometre arms, LISA will track relative displacements with a resolution of 20 picometres – 1/50 billionth of a metre – less than the width of a helium atom. It will look for ripples in space-time with periods ranging from a few minutes to a few hours. Several thousand objects are expected to be resolved within the first year of operation.
In addition to studying black holes and compact binaries, LISA will probe the expansion of the universe and the gravitational wave background created during the early universe. It will also look for currently unknown (and unmodelled) sources of gravitational waves. History in astrophysics has shown that whenever a new frequency range/medium of detection is available, new and unexpected sources show up. This may, for example, include kinks and cusps in cosmic strings.
Following its selection, LISA will now enter a more detailed phase of design and costing, before construction begins. Its launch is expected during 2034 and the mission lifetime is four years – but the spacecraft will have enough power and orbital stability to potentially last until 2044.
Chinese scientists report the transmission of entangled photons between suborbital space and Earth, using the satellite Micius. More satellites could follow in the near future, with plans for a European–Asian quantum-encrypted network by 2020, and a global network by 2030.
In a landmark study, Chinese scientists report the successful transmission of entangled photons between suborbital space and Earth. Furthermore, whereas the previous record for entanglement distance was 100 km (62 miles), here, transmission over more than 1,200 km (746 miles) was achieved.
The distribution of quantum entanglement, especially across vast distances, holds major implications for quantum teleportation and encryption networks. Yet, efforts to entangle quantum particles – essentially "linking" them together over long distances – have been limited to 100 km or less, mainly because the entanglement is lost as they are transmitted along optical fibres, or through open space on land.
One way to overcome this issue is to break the line of transmission into smaller segments and repeatedly swap, purify and store quantum information along the optical fibre. Another approach to achieving global quantum networks is by making use of lasers and satellite technologies. Using a Chinese satellite called Micius, launched last year and equipped with specialised quantum tools, Juan Yin et al. demonstrated the latter feat. The Micius satellite was used to communicate with three ground stations across China, each up to 1,200 km apart.
The separation between the orbiting satellite and these ground stations varied from 500 to 2,000 km. A laser beam on the satellite was subjected to a beam splitter, which gave the beam two distinct polarised states. One of the spilt beams was used for transmission of entangled photons, while the other was used for photon receipt. In this way, entangled photons were received at the separate ground stations.
"It's a huge, major achievement," Thomas Jennewein, physicist at the University of Waterloo in Canada, told Science. "They started with this bold idea and managed to do it."
"The Chinese experiment is quite a remarkable technological achievement," said Artur Ekert, a professor of quantum physics at the University of Oxford, in an interview with Live Science. "When I proposed the entangled-based quantum key distribution back in 1991 when I was a student in Oxford, I did not expect it to be elevated to such heights."
One of the many challenges faced by the team was keeping the beams of photons focused precisely on the ground stations as the satellite hurtled through space at nearly 8 kilometres per second.
Quantum encryption, if successfully developed, could revolutionise communications. Information sent via this method would, in theory, be absolutely secure and practically impossible for hackers to intercept. If two people shared an encrypted quantum message, a third person would be unable to access it without changing the information in an unpredictable way. Further satellite tests are planned by China in the near future, with potential for a European–Asian quantum-encrypted network by 2020, and a global network by 2030.