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October 14, 2019

With the discovery of 20 more moons orbiting Saturn, the ringed planet has overtaken Jupiter as host to
the most moons in the Solar system. Saturn now has 82 known moons, whereas Jupiter has a paltry 79.
Announced at the International Astronomical Union's Minor Planet Centre by a team of astronomers
from the Carnegie Institute for Science led by Scott S. Sheppard, the discovery is the latest advance in
the 400-year history of our understanding of the satellites of our neighbouring planets.
As technology has improved, we have observed more and more of these tiny, distant worlds – and we
can be reasonably confident there are still plenty waiting to be discovered.

How do we even know Saturn has moons?

Although most planets of the Solar system are visible to the naked eye and have been known to humans
since antiquity, it wasn't until Galileo Galilei turned a telescope on Jupiter in 1610 that we discovered
Earth was not alone in having an orbiting companion.
Galileo saw Jupiter's four largest moons and could make out what we now know are Saturn's rings.
Decades later, with better telescopes, Christian Huygens and Giovanni Domenico Cassini observed
Saturn's moons.
It became clear that the giant planets are surrounded by multitudes of satellites, resembling smaller
versions of the Solar system.
By the middle of the 19th century, telescopes had improved enough that the first eight moons of
Saturn – including Titan, the largest – had been viewed directly.
The introduction of photographic plates, which enabled the detection of fainter objects with
long-exposure observations, helped astronomers increase their count of Saturn's moons to 14.

Closer inspections

It was a long journey (literally) to the next big improvement in our view of Saturn's moons. Many of
the smaller moons were not discovered until the Voyager fly-by missions in the 1980s and the more
recent 13-year stopover of the Cassini spacecraft in Saturn's orbit.
Until these closer visits, we knew little about the moons aside from the fact that they existed.
One of Cassini's goals was to explore Titan, which is the only moon in the Solar system with a thick,
smoggy atmosphere. Another was to take a look at Saturn's other mid-sized moons, including frozen
Enceladus, which may hold an ocean of liquid water beneath its icy crust.
Cassini also discovered much smaller moons, so-called "shepherd moons" that interact with
Saturn's rings by carving gaps and wavy patterns as they pass through a rubble of rocks and snowballs.

Bigger telescopes, more moons

These close-up observations from space advanced our understanding of individual moons that stay
near to Saturn. Recently, many more moons have been found in orbits much further from the planet.
These more distant moons could only be detected with large optical telescopes such as the Subaru
telescope at Mauna Kea in Hawaii. The telescope is equipped with sensitive cameras that can detect
some of the faint objects separated by millions of kilometres from Saturn.
To confirm that these objects are indeed associated with Saturn, astronomers have to observe them
over days or even months to reconstruct the shape and size of the moon's orbit.

Many small moons are fragments of shattered large moons

Such observations revealed a population of moons that are often described as "irregular" moons.
They are split into three distinct groups: Inuit, Gallic, and Norse. They all have large, elliptical
orbits at an angle to those of moons closer to the planet.
Each group is thought to have formed from a collision or fragmentation of a larger moon. The
Norse group consists of some of the most distant moons of Saturn, which orbit in the opposite
direction to the rotation of the planet.
This suggests they could have formed elsewhere and were later captured by the gravitational force
of Saturn.
Of the 20 new moons, 17 belong to the Norse group including the furthest known moon from the
planet. Their estimated sizes are of the order of 5km in diameter.

Have we found all the moons now?

Are we likely to find even more moons around Saturn? Absolutely.
Some of the newly discovered moons are very faint and at the limit of detection with currently
available instruments. New, bigger telescopes such as Giant Magellan Telescope will allow us to
observe even fainter objects.
In the meantime, the 20 new moons need names. Carnegie Science has invited everyone to help.The Conversation

Lucyna Kedziora-Chudczer, Program Manager/Adjunct Research Fellow,
Swinburne University of Technology/
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May 21, 2018
In the quest for ever-colder temperatures, NASA is sending an apparatus to the International Space Station that will create a spot 10 billion times colder than the vacuum of space.
It's called the Cold Atom Laboratory, a payload about the size of an ice chest aboard Orbital ATK's Cygnus rocket, and it will help scientists observe the weird quantum properties of ultra-cold atoms.
A combination of lasers and magnets will be used to chill and slow a cloud of atoms to just a fraction above absolute zero, also known as zero Kelvin (-273.15 Celsius or -459.67 Fahrenheit).
Absolute zero is the coldest temperature in the Universe - and impossible to achieve, because at that point, atoms stop moving.
But the Cold Atom Laboratory (CAL) can cool clouds of atoms to just one-tenth of a billion of a degree above absolute zero, which causes them to move extremely slowly, exhibiting microscopic quantum phenomena.
These clouds are called Bose-Einstein condensates. They can be created on Earth, but there's a catch - gravity. It drags them downwards very quickly, so they can only be observed for a fraction of a second.
The microgravity environment aboard the ISS will overcome this significant problem, allowing scientists on Earth operating the equipment remotely to observe the atoms for up to 10 seconds.
This will be the longest we've ever been able to observe Bose-Einstein condensates, by a wide margin.
This has several scientific benefits. Because Bose-Einstein condensates are what is known as a superfluid - a type of fluid with zero viscosity - it will help us understand them better.
"If you had superfluid water and spun it around in a glass, it would spin forever," CAL project manager Anita Sengupta of JPL said last year.
"There's no viscosity to slow it down and dissipate the kinetic energy. If we can better understand the physics of superfluids, we can possibly learn to use those for more efficient transfer of energy."
It could also help advance superconductivity, and devices such as superconducting quantum interference devices, quantum computers, and laser-cooled atomic clocks. It could allow for the observation of never-before-seen quantum phenomena.
And it could even help detect and understand dark energy, the unknown force accelerating the expansion of the Universe.
"Studying these hyper-cold atoms could reshape our understanding of matter and the fundamental nature of gravity," said CAL project scientist Robert Thompson of JPL.
"The experiments we'll do with the Cold Atom Lab will give us insight into gravity and dark energy - some of the most pervasive forces in the universe."
The Cold Atom Laboratory isn't the only science payload departing for the ISS on Cygnus.
The rocket will also be carrying a handheld sextant to test for emergency star navigation (not to be confused with SEXTANT, the ground-breaking technology that uses pulsars as guide stars); and biomolecule sequencing technology, for sequencing microbes found aboard the ISS.
The launch is scheduled for Monday, May 21 at 08:39 UTC.
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June 04, 2017
Cosmic _Gravitational _Waves

The first direct evidence of string theory?
For the third time in two years, physicists have detected ripples in the fabric of spacetime, called gravitational waves, that Albert Einstein predicted the existence of more than 100 years ago with his theory of general relativity.
"Einstein continues to rock, in the sense that we keep pushing the boundaries of his theory," Vicky Kalogera, an astrophysicist at Northwestern University and LIGO data analyst, told Business Insider. "It passes every test that we throw at it."
The waves came from two black holes colliding together about 3 billion light-years from Earth, and a giant experiment called LIGO detected them.

But that's just one of many discoveries that gravitational waves could bring us as new detectors go online and get upgraded.
7 Cosmic _Phenomena_ Physicists_Gravitational _Waves_explanation_infographic

 This article was originally published by Business Insider.
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May 31, 2017

"If true, it's revolutionary." The Centre of Our Galaxy _ Find The Missing_ Fifth Force of _Nature

Our current understanding of the Universe states that it's governed by four fundamental forces: gravity, electromagnetic, and the strong and weak nuclear forces.
But there are hints of a fifth force of nature, and if it exists, we'd not only be able to fill the remaining holes in Einstein's general relativity - we'd have to rethink our understanding of how the Universe actually works. And now physicists have figured out how to put this mysterious force to the ultimate test.
The four forces of nature are what holds the standard model of physics together, which is what we use to explain and predict the behaviour of particles and matter in our Universe.
At the smallest end of the scale are the two nuclear forces - the strong nuclear force is what holds atomic nuclei in place, and the weak nuclear force enables certain atoms to undergo radioactive decay.
Gravity and the electromagnetic force are on the larger end of the scale - electromagnetic force is needed to keep our molecules together, while gravity is responsible for ensuring that entire galaxies and planets aren't ripped apart.
It's all very neat and sensible, but there's a problem - in a lot of ways, gravity is the 'odd one out' in this very important group.
For one thing, gravity is the last of the four fundamental forces that humans haven't figured out how to produce and control.
It also doesn't appear to explain everything that it should - studies have shown that there's more gravity in our Universe than can be produced by all the visible matter out there.
The entity that we use to explain this gap - a placeholder called dark matter - hasn't exactly helped its case, because even our best technology can't find a trace of it.
Thanks to our inability to figure out what dark matter actually is, some physicists (very controversially) want to ditch gravity as a fundamental force altogether.
But instead of permanently dropping one of the fundamental forces of nature in the hopes that the Universe will make more sense without it, what if we added a fifth force that ties gravity to the others in ways we've never thought of before?
"Einstein's theory describes [gravity] beautifully well, but there's lots of evidence showing the theory has holes," says Andrea Ghez, director of the University of California, Los Angeles Galactic Centre Group.
"The mere existence of supermassive black holes tells us that our current theories of how the Universe works are inadequate to explain what a black hole is."
Ghez and her team are on the hunt for this hypothetical fifth force of nature, and say the best place to look would be somewhere in the Universe where the influence of gravity is so strong, signs of something extra will be easier to detect.
By analysing extremely sharp images of the heart of the Milky Way taken with by the Keck Observatory in Hawaii, the researchers can track the orbits of stars near our galaxy's supermassive black hole.
Based on these paths, they can measure the direct influence of gravity on the stars' movements, and figure out if something else is at play.
"This is really exciting. [O]ur work on studying stars at the centre of our galaxy is opening up a new method of looking at how gravity works," says Ghez.
"By watching the stars move over 20 years using very precise measurements taken from Keck Observatory data, you can see and put constraints on how gravity works."
The team is particularly interested in an event that's expected to take place next year, when a star called S0-2 will draw closer than ever to our galaxy's supermassive black hole, and be pulled in at maximum gravitational strength.
If there are any deviations from what general relativity predicts, this will be the best time to spot them.
"If gravitation is driven by something other than Einstein's theory of general relativity, you'll see small variations in the orbital paths of the stars," says Ghez.
This isn't the first time that physicists have actively hunted for the fifth force of nature - last year, a separate team detected signs of its influence in the energy signature of what appeared to be a new subatomic particle.
"If true, it's revolutionary," lead researcher Jonathan Feng from the University of California, Irvine, said at the time.
"If confirmed by further experiments, this discovery of a possible fifth force would completely change our understanding of the Universe, with consequences for the unification of forces and dark matter."
We're still a long way off figuring out if this force actually exists, but this new technique will be the first time scientists have ever looked for it in a gravitational field as strong as the one created by a supermassive black hole.
And even if we don't end up finding another force of nature at the heart of our galaxy, we'll likely gain a better understanding of gravity itself - something the standard model of physics desperately needs.
"It's exciting that we can do this because we can ask a very fundamental question - how does gravity work?" says Ghez.


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January 22, 2017

Astronomers studying pulsars may have finally unravelled why these mysterious pulsating objects appear to send different kinds of signals into space – by tracking the immense cloud trails of their nebulae.

Thanks to images taken by NASA's Chandra X-ray Observatory, a new analysis of two very contrasting pulsars shows that pulsars' energy emissions may only be visible to Earth from certain angles – which could explain a mystery that's puzzled scientists up until now.

Pulsars are a kind of neutron star – an extremely dense core of matter left over once a massive star has exploded in a supernova.

What sets pulsars apart from other neutron stars are their pulsating radio waveemissions – a tightly focused beam of electromagnetic radiation that rapidly rotates around the pulsar much like the light shone from a lighthouse.

While pulsars were long categorised by the emission of these radio waves, more recently researchers have found that some pulsars also generate a different kind of energy signal – gamma rays – and the distinction has puzzled astronomers for almost a decade.

34898-ataleoftwopu-1Geminga, artist's impression. Credit: Nahks Tr'Ehnl

"It's not fully understood why there are variations between different pulsars," says researcher Bettina Posselt from Pennsylvania State University.

"One of the main ideas here is that pulse differences have a lot to do with geometry – and it also depends on how the pulsar's spin and magnetic axes are oriented with respect to line of sight whether you see certain pulsars or not, as well as how you see them."

One of the ways scientists can study pulsars is by tracking what's called pulsar wind nebulae – clouds of energetic particles that form doughnut-shaped rings called tori, which stretch out into tail-like structures as they spin off from the rapidly rotating pulsar.

Thanks to the Chandra X-ray Observatory, scientists can now study these nebulae, which helps us understand the different kinds of magnetic activity that pulsars exhibit – and also why we only pick up certain emissions from them.

"This is one of the nicest results of our larger study of pulsar wind nebulae," says one of the team, physicist Roger W. Romani from Stanford University.

"By making the 3D structure of these winds visible, we have shown how one can trace back to the plasma injected by the pulsar at the centre."

Two very divergent kinds of pulsar wind nebulae can be seen in the pulsars Geminga – which is approximately 800 light-years from Earth – and BO355+54, which is about 3,300 light years away.

In the case of Geminga (shown above), you can see the pulsar has three distinct tails making up its nebulae. Of these, the two long tails are called lateral tails, and are thought to spin off from Geminga's magnetic poles.

These lateral tails stretch out for more than half a light-year from Geminga, while a third, shorter tail also emanates from the pulsar.

The researchers think the positioning of Geminga's poles is why we can only pick up gamma rays from the pulsar on Earth – but not radio emissions.

"The tails seem to tell us why that is," says Posselt. "For Geminga, we view the bright gamma ray pulses and the edge of the pulsar wind nebula torus, but the radio beams near the jets point off to the sides and remain unseen."

34898-ataleoftwopu-2

Top Left X-ray: NASA/CXC/PSU/B.Posselt et al; Infrared: NASA/JPL-Caltech. Top Right X-ray: NASA/CXC/GWU/N.Klinger et al; Infrared: NASA/JPL-Caltech. Illustrations by Nahks Tr'Ehnl.

By contrast, B0355+54 (pictured above alongside Geminga) has its radio waves angled at Earth, which is how we're able to detect it – even though we can't pick up its gamma rays.

"For B0355+54, a jet points nearly at us so we detect the bright radio pulses while most of the gamma-ray emission is directed in the plane of the sky and misses the Earth," says one of the team, Oleg Kargaltsev from George Washington University.

"This implies that the pulsar's spin axis direction is close to our line-of-sight direction and that the pulsar is moving nearly perpendicularly to its spin axis."


While there's still a lot to learn about pulsars, the new discoveries help explain why we've only picked up distinct emissions from these kinds of cosmic objects before – and lets researchers study particle physics in ways that would be impossible to replicate in a lab on Earth.

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January 22, 2017

It's not science fiction anymore.

A paper landed in my inbox this week with a startling premise: soon, stem cells swabbed from human beings’ cheeks or skin could be cultured to create germ cells (sperm and eggs), and from there to create a human being.
The process, known as in vitro gametogenesis (IVG), has never been completed with cells from people. And, in fact, human and primate studies have been met with limited success.
But there have been real, live mice (and more mouse embryos that were not allowed to develop) created through this process. Every indication is that human beings will soon follow.
In a paper published Wednesday in the journal Science Translational Medicine, three researchers argue that now is the time to consider the serious cultural and ethical questions around this technology.
Eli Adashi, a professor of medical science at Brown University and an author on the paper, said that the medical benefits of the technology are clear.
"Imagine a young girl who came down with cancer, and had been subjected to chemotherapy and radiation, and recovered," he said.
"Now she’s a woman who’s contemplating [having a child,] and is infertile due to the cancer therapy. An individual like that would today require a donor egg, which is not trivial because producing an egg or recovering an egg from a woman is not as simple as recovering sperm from men."
With IVG, there would be no need for the complicated and expensive process of retrieving a donor egg from a third person. Instead, a swab of the cheek and some time to culture in a laboratory could produce as many eggs as the woman might need.
Similarly, men with genetic infertility disorders might benefit from therapies that edit the genes of their sperm in order to render it fertile. But often it’s difficult to collect enough sperm from those men for the potential therapies to work.
IVG would enable doctors to create a near-unlimited supply.
And finally, IVG could render the existing in vitro fertilisation (IVF) process much cheaper. No need for the couple to go through a complicated and often difficult extraction process; a few minutes with a cheek swab will do the job.
However, and this is the big however that led Adashi and his colleagues to write this paper, there’s real reason for concern about the ethics and, frankly, politics of IVG.
First, any new technology involved in creating new human beings will have to pass a rigorous battery of safety tests. First in nonhuman primates, and then in people.
Regulators will ensure that any children born through this process are monitored carefully for ill health effects and other problems.
But if IVG clears that hurdle, it will still face a culture with some serious sensitivities around embryos and the earliest stages of life.
"If you have an inexhaustible supply of eggs and sperm, it stands to reason that some, or a whole lot, of embryos will be generated," Adashi said.
And if large groups of embryos are created, whether for purposes of creating children or for research, it’s likely that many will be destroyed, intentionally or otherwise. And there are people who believe deeply that destroying an embryo is murder.
This isn’t a new issue, per se. Ethical questions around stem cells and human embryos have impacted medical science for years, even rising to the level of national politics.
But IVG does present a new potential flashpoint for this debate, with the real possibility of conflict between activists who would attribute human rights to embryos and parents seeking fertility treatments.
And Adashi says that conflict might be closer than many people realise. He traces the history of this science back to an early paper published in 2005.
"Ten [or so] years is not a very long time," he said.
"And it might give you at least an inkling of when there might be a reported comparable finding in a human. We don’t know, but the lesson here is sooner than we think. Let’s not wait till that moment arrives. Let’s start the [ethical] conversation now."
"Like all conversations, it will be time consuming. And depending how well we do it, and we’ve got to do it well, it will be demanding."
He warns that if scientists don’t begin that conversation, the results will be bad for science.

"It will not be wise to have that conversation when you’re seeing a paper in Science or Nature reporting the complete process in a human. That would not be wise on our collective part. We should be as much as possible ready for that."

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