Our solar system is full of moons of many different kinds, just as diverse and amazing as the planets they orbit. While Earth only has one moon, and some planets, like Mercury and Venus, have none, others have dozens, namely Jupiter and Saturn. The ice giants Uranus and Neptune also have quite a few each. On July 17, 2018, astronomers announced they’ve discovered even more moons orbiting Jupiter – 10 additional moons, in fact, bringing the known total of Jupiter’s moons now to 79. Nine of those 10 moons are what the astronomers are calling normal, but they’ve labeled one as a real oddball. As so often happens, the astronomers found the moons while searching for something completely unrelated.
These astronomers said they came upon the new moons while searching the outer solar system for evidence of Planet Nine, a large, as-yet unseen planet thought by some scientists to exist in the far outer reaches of the solar system, far beyond Pluto. That was in the spring of 2017. Scott S. Sheppard of the Carnegie Institute for Science led the astronomy team. He said Jupiter happened to be near the search field where they were searching for Planet Nine, and he added:
Jupiter just happened to be in the sky near the search fields where we were looking for extremely distant solar system objects, so we were serendipitously able to look for new moons around Jupiter while at the same time looking for planets at the fringes of our solar system.
Images of the oddball moon – now called Valetudo – from the Magellan telescope in Chile in May 2018. Image via Carnegie Science.
Why are we just now hearing about it? These astronomers said that, while the new observations were exciting, they needed to confirmed them. As Gareth Williams at the International Astronomical Union’s Minor Planet Center explained:
It takes several observations to confirm an object actually orbits around Jupiter. So, the whole process took a year.
It should be noted that the July 17 announcement by Carnegie Science also contains two moons that had been previously found and announced in 2017. Those 2017 moons were labeled S/2016 J1 and S/2017 J1. That gives us a total of 12 new moons for Jupiter confirmed since early 2017, two last year and 10 this year.
All of these new moons are very small, only about one to three kilometers across (a kilometer is 0.6 miles). In that way, they’re like many of Jupiter’s other small moons. They’re thought to have formed after the gas and dust from the earliest stages of planetary formation had dissipated.
Nine of the 10 new moons orbit in a retrograde direction, that is, opposite direction of Jupiter’s spin. They are part of a larger swarm of moons orbiting a long distance out from Jupiter. All of these moons are thought to be the remnants of three much larger bodies that were destroyed by collisions with other moons, asteroids or comets.
SheppardJupiterMoonsMovie - YouTube
The 10th new moon is the oddball. It’s more distant than Jupiter’s prograde moons – those that orbit in the same direction as Jupiter’s spin – and its orbit is much more inclined, crossing the orbits of the outer retrograde moons. It has been nicknamed Valetudo, after the Roman god Jupiter’s great-granddaughter. According to Sheppard:
Our other discovery is a real oddball and has an orbit like no other known Jovian moon. It’s also likely Jupiter’s smallest known moon, being less than one kilometer (0.6 miles) in diameter.
Since Valetudo is moving in the opposite direction to the other retrograde moons, there is a greater chance of a collision occurring, and is probably inevitable. As Sheppard noted:
This is an unstable situation. Head-on collisions would quickly break apart and grind the objects down to dust.
The two other moons mentioned by Carnegie Science are much closer to Jupiter, and orbit in the prograde direction, the same direction as Jupiter’s rotation. They are also part of a larger group of small moons thought to be the left-over remnants of a once larger moon.
So we are still finding moons for Jupiter. As for how many ultimately will be found, no one knows for sure. For a long time the number hovered at 69, and now it is 79. It’s likely that even more small moons are still waiting to be found. According to Sheppard:
Well, it probably won’t stay at 79 for very long. We actually found, on some of the best nights we had, we could image objects even deeper – things that are right on the edge of our noise. There’s many more smaller moons around Jupiter. It’s just very hard to follow those.
Bottom line: For a long time, Jupiter had been known to have dozens of moons. Now, thanks to a search that was primarily for Planet Nine, astronomers have discovered even more – 79 in total. This is the largest number of moons of any planet in the solar system.
Sounds of Saturn: Hear Radio Emissions of the Planet and Its Moon Enceladus - YouTube
New observations from the Cassini spacecraft’s final orbits of planet Saturn reveal a surprisingly powerful and dynamic interaction of plasma waves moving from Saturn to its rings and its moon Enceladus. Research shows that the waves travel on magnetic field lines connecting Saturn directly to Enceladus. The field lines are like an electrical circuit between the two bodies, said the researchers, with energy flowing back and forth.
The recording was captured September 2, 2017, two weeks before Cassini’s mission-ending plunge into Saturn’s atmosphere. Researchers converted the recording of the plasma waves into a “whooshing” audio file – in the same way a radio translates electromagnetic waves into music. In other words, Cassini detected electromagnetic waves in the audio frequency range – and on the ground, we can amplify and play those signals through a speaker. The recording time was compressed from 16 minutes to 28.5 seconds.
NASA’s Cassini spacecraft’s Grand Finale orbits found a powerful interaction of plasma waves moving from Saturn to its rings and its moon Enceladus. Image via NASA/JPL-Caltech.
Much like air or water, plasma (the fourth state of matter, which, unlike solids, liquids, and gas, does not exist freely on Earth’s surface under normal conditions) generates waves to carry energy. The Radio and Plasma Wave Science (RPWS) instrument on board Cassini recorded intense plasma waves during one of its closest encounters to Saturn.
Ali Sulaiman, planetary scientist at the University of Iowa, and a member of the RPWS team, is lead author of a pair of papers describing the findings, published June 7, 2018, and April 28, 2018, in Geophysical Research Letters. Sualiman said in a statement:
Enceladus is this little generator going around Saturn, and we know it is a continuous source of energy. Now we find that Saturn responds by launching signals in the form of plasma waves, through the circuit of magnetic field lines connecting it to Enceladus hundreds of thousands of miles away.
The interaction of Saturn and Enceladus is different from the relationship of Earth and its moon. Enceladus is immersed in Saturn’s magnetic field and is geologically active, emitting plumes of water vapor that become ionized and fill the environment around Saturn. Our own moon does not interact in the same way with Earth. Similar interactions take place between Saturn and its rings, as they are also very dynamic.
Bottom line: Scientists have discovered a surprisingly powerful interaction of plasma waves moving from Saturn to its moon Enceladus. Researchers converted a NASA Cassini spacecraft recording of plasma waves into a “whooshing” audio file.
Ghost dunes in the Noctis Labyrinthus region on Mars, west of the more famous Valles Marineris. The crescent-shaped pits are the remains of active barchan-type dunes from billions of years ago. Image via Mackenzie Day/David Catling/AGU.
Mars is a desert planet, a lot like some deserts on Earth, but much colder. Also just like Earth, the Martian deserts have vast dunes, ranging from small sand ripples (technically not dunes) to towering, cliff-like true dunes of fine sand. But – while various types of dunes have been seen from orbit and up close by Mars rovers, currently still active and gradually making their way across the landscape – now another kind of dune has been found on Mars as well. Scientists call these ghost dunes, and they are very ancient. They reported the finding in GeoSpace on July 10, 2018. The new research paper was just published in the Journal of Geophysical Research: Planets.
These ghost dunes are not active dunes today. Rather, they are the remains of previous ancient dunes that left pit-like depressions in the ground after they eroded away. Hundreds of these crescent-shaped pits have been discovered, each about the size of the U.S. Capitol building. As Mackenzie Day, a planetary geomorphologist at the University of Washington in Seattle and an author of the new study, explained:
Any one of these pits is not enough to tell you that it’s a dune, or from an ancient dune field, but when you put them all together, they have so many commonalities with dunes on Mars and on Earth that you have to employ some kind of fantastic explanation to explain them as anything other than dunes.
How do ghost dunes form? On Earth, ghost dunes may have been partially buried by lava or water-borne sediments. For these Martian ghost dunes, when the lava or sediments hardened, they preserved the contours of the dunes. The remaining top portions of the dunes were then eroded away by winds, which scoured them out, leaving only the “mold” outlines of the former dunes. Now they look like pits with hardened edges.
These dunes’ existence on Mars provide more clues as to what conditions were like billions of years ago, in particular, winds. As Day noted:
One of the cool things about the ghost dunes is that they tell us, for sure, that the wind on Mars was different in the ancient past, when they formed. The fact that the wind was different [when the ghost dunes formed] tells us that the environmental conditions on Mars aren’t static over long time scales, they have changed over the past couple billion years, something we need to know to interpret the geology on Mars.
Crescent-shaped barchan dunes in Egypt’s Western Desert. Image via Google Earth.
How barchan dunes form. Image via Wikipedia CC BY-SA 3.0.
The Martian ghost dunes were found in orbital images of Hellas Planitia basin and Noctis Labyrinthus. They are similar to ones discovered in the Snake River Plain in eastern Idaho in 2016. More than 480 potential dune molds were discovered in orbital images of Noctis Labyrinthus alone, and more than 300 in Hellas Planitia, by Day and co-author David Catling. Noctis Labyrinthus is a region of jumbled plateaus just west of Valles Marineris, the largest-known canyon in the solar system. Hellas Planitia is a massive 4-billion-year-old impact crater over 1,678 miles (2,700 km) across in the southern hemisphere.
The shapes of the ghost dunes on Mars are crescents, just like barchan dunes on Earth, meaning that the original dunes would have been very similar to barchan dunes, the most common type on both Mars and Earth. The “horns” or tips of the crescents point in the direction of the prevailing wind. This type of dunes tends to form on flat terrain where there is little or no vegetation. The fact that there are so many of these pits in each location points to them being the remains of once-active dune fields. As Day noted:
They are all going the same way, which you would expect for dunes because they are all migrating and forming in the same wind regime. So just the shape and size tell us that these are features that are coming from an ancient dune system.
Ghost dunes on Idaho’s eastern Snake River plain. Image via Google Earth.
Analysis of the ghost dunes on Mars indicates that the original dunes were quite large – about 130 feet (40 meters) tall at Noctis Labyrinthus and 246 feet (75 meters) tall at Hellas basin. By comparison, the Curiosity rover has studied a series of dunes near the base of Mount Sharp in Gale Crater. The striking Namib Dune is about 16 feet (5 meters) tall.
As well as providing fascinating clues about ancient environmental conditions on Mars, these ghost dunes may also be a good place to search for evidence of past life. As mentioned in the summary in the new paper:
Ancient dunes in two places on Mars were partially buried and then eroded away, leaving behind dune-shaped pits that preserve information about the ancient environment. These pits may contain ancient dune sandstones around the edges of the pits and could be a good place to look for evidence of ancient life. The shapes of the pits also tell us how the winds behaved in the past.
Namib Dune in Gale Crater on Mars, as seen by the Curiosity rover. It is about 16 feet (5 meters) tall. Image via NASA/JPL-Caltech/MSSS/Thomas Appéré.
And as Day noted also:
We know that dunes on Earth can support life, and dunes on Earth are very similar to dunes on Mars. One problem that Mars has that Earth doesn’t is the surface radiation. If you are inside a dune, or at the bottom of a dune, and you are microbial life, the dune is protecting you from a lot of that radiation. There is probably nothing living there now. But if there ever was anything on Mars, this is a better place than average to look.
Bottom line: As well as being common on Earth, dunes have also been found on Mars, Venus, Titan and even comet 67P. Now another type of dune has been discovered on Mars – “ghost dunes,” the pit-like remains of ancient, once-active dunes which have mostly eroded away. They bear a strong similarity to present-day dunes and may even hold clues to past life on the red planet.
A test observation by IRD of red dwarf GJ 436. Comparing the star’s spectrum (broken line) to the laser frequency comb (dots) allows researchers to calculate the motion of the star. Image via NINS Astrobiology Center.
IRD will observe the infrared light coming from these stars (which emit more IR than visible light); when that is combined with the huge light-gathering power of the telescope itself, astronomers hope to find hundreds more planets orbiting red dwarf stars. It is generally easier to detect planets orbiting red dwarfs since those stars are smaller and fainter than ones like the sun. There are also many red dwarfs in the sun’s neighborhood that can be studied.
Artist’s conception of an exoplanet orbiting a red dwarf star. Red dwarfs are the most common star in our galaxy, and many exoplanets have already been discovered orbiting them. Image via NASA/ESA/G. Bacon.
Other technology, called a laser frequency comb, provides a standard ruler for measuring the line-of-sight movement of a star to within a few meters per second. From that data, scientists can determine a planet’s distance from the star and its mass.
Many exoplanets have already been discovered around red dwarfs by other telescopes such as the Kepler Space Telescope as well; some of these have been larger gas giant planets like Jupiter, but smaller rocky worlds have also been discovered. This includes planets about the same size as Earth, orbiting in the star’s habitable zone, the region where liquid water can be stable on the surface of a planet.
Kepler-186f was the first Earth-sized exoplanet to be discovered in the habitable zone of its star, a red dwarf. Image via NASA Ames/JPL-Caltech/T. Pyle.
The first Earth-sized exoplanet to be found orbiting a red dwarf star in its habitable zone was Kepler-186f. The planet is less than ten percent larger than Earth and orbits the star every 130 days. Since the star is smaller and cooler than the sun, that means Kepler-186f actually resides in the habitable zone, even though it orbits much closer to the star than the Earth does to the sun. It is one of five known planets in the system, about 500 light-years from Earth; the other four all orbit closer to the star.
As recently reported on EarthSky, new findings suggest that Kepler-186f and another similar planet, Kepler-62f, 1,200 light-years away, have seasons and stable climates like Earth. That’s good news for those hoping to find another planet similar to Earth out there – Earth 2.0 if you will. Not a lot else is known about these planets yet, but both are considered to be at least potentially habitable.
The Subaru Telescope on Mauna Kea in Hawaii. Image via National Astronomical Observatory of Japan (NAOJ).
What if planets are constantly bathed by these smaller, but still significant, flares? There could be a cumulative effect.
Bottom line: Red dwarfs are the most common type of star in our galaxy, and many, if not most, appear to have exoplanets orbiting them. Despite problems from solar flares, some of those planets are potentially habitable, meaning that there could be countless such worlds in the universe. New IRD technology from Japan will now make it easier to find them.
About four billion years ago, when the planet Earth was still in its infancy, the axis of a black hole about one billion times more massive than the sun happened to be pointing right to where our planet was going to be on September 22, 2017.
Blazar shoots neutrinos and gamma rays to Earth: Blazars are a type of active galactic nucleus with one of its jets pointing toward us. In this artistic rendering, a blazar emits both neutrinos and gamma rays that could be detected by the IceCube Neutrino Observatory as well as by other telescopes on Earth and in space. Image via IceCube/NASA.
Along the axis, a high-energy jet of particles sent photons and neutrinos racing in our direction at or near the speed of light. The IceCube Neutrino Observatory at the South Pole detected one of these subatomic particles – the IceCube-170922A neutrino – and traced it back to a small patch of sky in the constellation Orion and pinpointed the cosmic source: a flaring black hole the size of a billion suns, 3.7 billion light-years from Earth, known as blazar TXS 0506+056. Blazars have been known about for some time. What wasn’t clear was that they could produce high-energy neutrinos. Even more exciting was such neutrinos had never before been traced to its source.
Finding the cosmic source of high-energy neutrinos for the first time, announced on July 12, 2018, by the National Science Foundation, marks the dawn of a new era of neutrino astronomy. Pursued in fits and starts since 1976, when pioneering physicists first tried to build a large-scale high-energy neutrino detector off the Hawaiian coast, IceCube’s discovery marks the triumphant conclusion of a long and difficult campaign by many hundreds of scientists and engineers – and simultaneously the birth of a completely new branch of astronomy.
The constellation of Orion, with a bullseye on the location of the blazar. Image via Silvia Bravo Gallart/Project_WIPAC_Communications.
The detection of two distinct astronomical messengers – neutrinos and light – is a powerful demonstration of how so-called multimessenger astronomy can provide the leverage we need to identify and understand some of the most energetic phenomena in the universe. Since its discovery as a neutrino source less than a year ago, blazar TXS 0506+056 has been the subject of intensive scrutiny. Its associated stream of neutrinos continues to provide deep insights into the physical processes at work near the black hole and its powerful jet of particles and radiation, beamed almost directly toward Earth from its location just off the shoulder of Orion.
As three scientists in a global team of physicists and astronomers involved in this remarkable discovery, we were drawn to participate in this experiment for its sheer audacity, for the physical and emotional challenge of working long shifts at in a brutally cold location while inserting expensive, sensitive equipment into holes drilled 1.5 miles deep in the ice and making it all work. And, of course, for the thrilling opportunity to be the first people to peer into a brand new kind of telescope and see what it reveals about the heavens.
A remote, frigid neutrino detector
At an altitude exceeding 9,000 feet and with average summertime temperatures rarely breaking a frigid -30 Celsius [-22 Fahrenheit], the South Pole may not strike you as the ideal place to do anything, aside from bragging about visiting a place that is so sunny and bright you need sunscreen for your nostrils. On the other hand, once you realize that the altitude is due to a thick coat of ultrapure ice made from several hundred thousand years of pristine snowfall and that the low temperatures have kept it all nicely frozen, then it might not surprise you that for neutrino telescope builders, the scientific advantages outweigh the forbidding environment. The South Pole is now the home of the world’s largest neutrino detector, IceCube.
March 2015: The IceCube Laboratory at the Amundsen-Scott South Pole Station, in Antarctica, hosts the computers that collect raw data from the detector. Due to satellite bandwidth allocations, the first level of reconstruction and event filtering happens in near real time in this lab. Image via Erik Beiser, IceCube/NSF.
It may seem odd that we need such an elaborate detector given that about 100 billion of these fundamental particles sashay right through your thumbnail each second and glide effortlessly through the entire Earth without interacting with a single earthly atom.
In fact, neutrinos are the second most ubiquitous particles, second only to the cosmic microwave background photons left over from the Big Bang. They comprise one-quarter of known fundamental particles. Yet, because they barely interact with other matter, they are arguably the least well understood.
To catch a handful of these elusive particles, and to discover their sources, physicists need big – kilometer-wide – detectors made of an optically clear material – like ice. Fortunately Mother Nature provided this pristine slab of clear ice where we could build our detector.
The IceCube Neutrino Observatory instruments take up a volume of roughly one cubic kilometer of clear Antarctic ice with 5,160 digital optical modules (DOMs) at depths between 1,450 and 2,450 meters [about 4,800 and 8,000 feet]. The observatory includes a densely instrumented subdetector, DeepCore, and a surface air shower array, IceTop. Image via Felipe Pedreros, IceCube/NSF.
At the South Pole several hundred scientists and engineers have constructed and deployed over 5,000 individual photosensors in 86 separate 1.5-mile-deep [2.4 km deep] holes melted in the polar ice cap with a custom-designed hot-water drill. Over the course of seven austral summer seasons we installed all the sensors. The IceCube array was fully installed in early 2011 and has been taking data continuously since.
This array of ice-bound detectors can sense with great precision when a neutrino flies through and interacts with a few Earthly particles that generate dim patterns of bluish Cherenkov light, given off when charged particles move through a medium like ice at close to light speed.
Blazar emission with neutrino reaches IceCube - YouTube
Blazar emission reaches Earth: Gamma rays (magenta), the most energetic form of light, and elusive particles called neutrinos (gray) formed in the jet of an active galactic nucleus far, far away. The radiation traveled for about 4 billion years before reaching Earth. The IceCube Neutrino Observatory at the South Pole detected the arrival of neutrino IC170922 entering Antarctica on September 22, 2017. After the interaction with a molecule of ice, a secondary high-energy particle – a muon – enters IceCube, leaving a trace of blue light behind it. Via NASA’s Goddard Space Flight Center/CI Lab/Nicolle R. Fuller/NSF/IceCube.
Neutrinos from the cosmos
The Achilles’ heel of neutrino detectors is that other particles, originating in the nearby atmosphere, can also trigger these patterns of bluish Cherenkov light. To eliminate these false signals, the detectors are buried deep in the ice to filter out interference before it can reach the sensitive detector. But in spite of being under nearly a mile of solid ice, IceCube still faces an onslaught of about 2,500 such particles every second, each of which could plausibly have been due to a neutrino.
With the expected rate of interesting, real astrophysical neutrino interactions (like incoming neutrinos from a black hole) hovering at about one per month, we were faced with a daunting needle-in-a-haystack problem.
The IceCube strategy is to look only at events with such high energy that they are exceedingly unlikely to be atmospheric in origin. With these selection criteria and several years of data, IceCube discovered the astrophysical neutrinos it had long been seeking, but it could not identify any individual sources – such as active galactic nuclei or gamma-ray bursts – among the several dozen high-energy neutrinos it had captured.
To tease out actual sources, IceCube began distributing neutrino arrival alerts in April 2016 with help from the Astrophysical Multimessenger Observatory Network at Penn State. Over the course of the next 16 months, 11 IceCube-AMON neutrino alerts were distributed via AMON and the Gamma-ray Coordinates Network, just minutes or seconds after being detected at the South Pole.
On September 22, 2017, IceCube alerted the international astronomy community about the detection of a high-energy neutrino. About 20 observatories on Earth and in space made follow-up observations, which allowed identification of what scientists deem to be a source of very high energy neutrinos and, thus, of cosmic rays. Besides neutrinos, the observations made across the electromagnetic spectrum included gamma-rays, X-rays, and optical and radio radiation. These observatories are run by international teams with a total of more than 1,000 scientists supported by funding agencies in countries around the world. Image via Nicolle R. Fuller/NSF/IceCube.
Swift was the first facility to identify the flaring blazar TXS 0506+056 as a possible source of the neutrino event. The Fermi Large Area Telescope then reported that the blazar was in a flaring state, emitting many more gamma-rays than it had in the past. As the news spread, other observatories enthusiastically jumped on the bandwagon and a broad range of observations ensued. The MAGIC ground-based telescope noted our neutrino came from a region producing very high-energy gamma-rays (each about ten million times more energetic than an X-ray), the first time such a coincidence has ever been observed. Other optical observations completed the puzzle by measuring the distance to blazar TXS 0506+056: about four billion light years from Earth.
With the first-ever identification of a cosmic source of high-energy neutrinos, a new branch on the astronomy tree has sprouted. As high-energy neutrino astronomy grows with more data, improved inter-observatory coordination, and more sensitive detectors, we will be able to map the neutrino sky with better and better precision.
And we expect exciting new breakthroughs in our understanding of the universe to follow suit, such as: solving the century-old mystery of the origin of astoundingly energetic cosmic rays; testing if spacetime itself is foamy, with quantum fluctuations at very small distance scales, as predicted by certain theories of quantum gravity; and figuring out exactly how cosmic accelerators, like those around the TXS 0506+056 black hole, manage to accelerate particles to such breathtakingly high energies.
For 20 years, the IceCube Collaboration had a dream to identify the sources of high-energy cosmic neutrinos – and this dream is now a reality.
The object known as 1I/2017 U1 (and nicknamed ‘Oumuamua) was traveling too fast (196,000 miles per hour, that’s 54 miles per second or 87.3 kilometers per second) to have originated in our solar system. Comets and asteroids from within our solar system move at a slower speed, typically an average of 12 miles per second (19 km per second) . In non-technical terms, ‘Oumuamua is an interstellar vagabond.
Artist’s concept of the interstellar object ‘Oumuamua. Image via ESA/Hubble, NASA, ESO, M. Kornmesser.
2. We’re not sure where it came from.
‘Oumuamua entered our solar system from the rough direction of the constellation Lyra, but it’s impossible to tell where it originally came from. Thousands of years ago, when ‘Oumuamua started to wander from its parent planetary system, the stars were in a different position so it’s impossible to pinpoint its point of origin. It could have been wandering the galaxy for billions of years.
3. We know it’s out of here.
‘Oumuamua is headed back out of our solar system and won’t be coming back. It’s rapidly headed in the direction of the constellation Pegasus and will cross the orbit of Neptune in about four years and cover one light year’s distance in about 11,000 years.
4. We don’t really know what it looks like.
We’ve only seen it as a speck of light through a telescope (it is far away and less than half a mile in length), but its unique rotation leads us to believe that it’s elongated like a cigar, about 10 times longer than it is wide. We can’t see it anymore. Artist’s concepts are the best guesses at what it might look like.
5. We know it got a little speed boost.
A rapid response observing campaign allowed us to watch as ‘Oumuamua got an unexpected boost in speed. The acceleration slightly changed its course from earlier predictions. Davide Farnocchia, of the Center for Near Earth Object Studies (CNEOS) at NASA’s Jet Propulsion Laboratory, said:
This additional subtle force on ‘Oumuamua likely is caused by jets of gaseous material expelled from its surface. This same kind of outgassing affects the motion of many comets in our solar system.
6. We know it’s tumbling.
Unusual variations in the comet’s brightness suggest it is rotating on more than one axis.
This illustration shows ‘Oumuamua racing toward the outskirts of our solar system. As the complex rotation of the object makes it difficult to determine the exact shape, there are many models of what it could look like. Image via NASA/ESA/STScI.
Karen Meech, an astronomer at the University of Hawaii’s Institute of Astronomy, said small dust grains, present on the surface of most comets, may have eroded away during ‘Oumuamua’s long journey through interstellar space. She said:
The more we study ‘Oumuamua, the more exciting it gets.
It could be giving off gases that are harder to see than dust, but it’s impossible to know at this point.
8. We knew to expect it.
Just not when. The discovery of an interstellar object has been anticipated for decades. The space between the stars probably has billions and billions of asteroids and comets roaming around independently. Scientists understood that, inevitably, some of these small bodies would enter our own solar system. This interstellar visit by ‘Oumuamua reinforces our models of how planetary systems form.
9. We don’t know what it’s doing now.
After January 2018, ‘Oumuamua was no longer visible to telescopes, even in space. But scientists continue to analyze the data gathered during the international observing campaign and crack open more mysteries about this unique interstellar visitor.
10. We know there’s a good chance we’ll see another one … eventually.
Because ‘Oumuamua is the first interstellar object ever observed in our solar system, researchers caution that it’s difficult to draw general conclusions about this newly-discovered class of celestial bodies. Observations point to the possibility that other star systems regularly eject small comet-like objects and there should be more of them drifting among the stars. Future ground- and space-based surveys could detect more of these interstellar vagabonds, providing a larger sample for scientists to analyze. Meech said:
I can hardly wait for the next interstellar object!
Bottom line: What science knows and doesn’t know about ‘Oumuamua, the first confirmed interstellar object to pass through our solar system.
Rare Double Asteroid Revealed by NASA, Observatories - YouTube
New observations by three of the world’s largest radio telescopes have revealed something new about an asteroid with a great name: 2017 YE5. This object, which swept by Earth late in June, 2018, is actually two bodies orbiting a common center of gravity. Each little world is about 3,000 feet (900 meters) in size. Radar observations show these space rocks have similar sizes, but hint that the two objects may be very different in composition and densities. In fact, NASA astronomers suggest one or both space rocks could be extinct Jupiter-family comets.
The Arecibo Observatory in Puerto Rico, along with the Goldstone Solar System Radar in California, and the Green Bank Observatory in West Virginia combined their efforts to study this object as it swept closest to us in June. The studies showed not one but two objects, about equal in mass. This is only the fourth equal-mass-binary, near-Earth asteroid ever detected.
Also, the recent studies revealed the two tiny worlds in the 2017 YES system revolve around each other once every 20 to 24 hours. And they showed the objects do not reflect as much sunlight as a typical rocky asteroid. In fact, scientists said, 2017 YE5 is likely as dark as charcoal.
Artist’s illustration of the trajectory of asteroid 2017 YE5 through the solar system. At its closest approach to Earth, the asteroid came to within 16 times the distance between Earth and the moon. Image via NASA/JPL-Caltech.
Astronomers with the Morocco Oukaimeden Sky Survey (MOSS) discovered the near-Earth asteroid 2017 YE5 on December 21, 2017. But the object(s) didn’t come closest to us until June 21, 2018. The June close approach was the closest this little system will come to Earth for at least the next 170 years, about 15.5 lunar distances (within 3.7 million miles, or 6 million km). The approach was close enough to provide a good opportunity for radar observations, and even for optical observations, as the asteroid reached a visual magnitude of 15.
Scientists estimate that among near-Earth asteroids larger than 650 feet (200 meters) in size, about 15 percent are binaries with one larger object and a much smaller satellite. Equal-mass binaries like 2017 YE5 are much rarer.
Contact binaries – where two similarly sized objects actually touch each other – are thought to make up another 15 percent of near-Earth asteroids larger than 650 feet (200 meters) in size.
Bi-static radar images of the binary asteroid 2017 YE5 from the Arecibo Observatory and the Green Bank Observatory on June 25. The observations show that the asteroid consists of two separate objects in orbit around each other. Image via Arecibo/GBO/NSF/NASA/JPL-Caltech.
Here’s how three of the world’s largest observatories teamed up to make the discovery, according to a statement from NASA/JPL:
On June 21 and 22, observations by NASA’s Goldstone Solar System Radar (GSSR) in California showed the first signs that 2017 YE5 could be a binary system. The observations revealed two distinct lobes, but the asteroid’s orientation was such that scientists could not see if the two bodies were separate or joined. Eventually, the two objects rotated to expose a distinct gap between them.
Scientists at the Arecibo Observatory in Puerto Rico had already planned to observe 2017 YE5, and they were alerted by their colleagues at Goldstone of the asteroid’s unique properties. On June 24, the scientists teamed up with researchers at the Green Bank Observatory (GBO) in West Virginia and used the two observatories together in a bi-static radar configuration (in which Arecibo transmits the radar signal and Green Bank receives the return signal). Together, they were able to confirm that 2017 YE5 consists of two separated objects. By June 26, both Goldstone and Arecibo had independently confirmed the asteroid’s binary nature.
The new observations obtained between June 21 and 26 indicate that the two objects revolve around each other once every 20 to 24 hours. This was confirmed with visible-light observations of brightness variations by Brian Warner at the Center for Solar System Studies in Rancho Cucamonga, California.
Radar imaging shows that the two objects are larger than their combined optical brightness originally suggested, indicating that the two rocks do not reflect as much sunlight as a typical rocky asteroid. 2017 YE5 is likely as dark as charcoal. The Goldstone images taken on June 21 also show a striking difference in the radar reflectivity of the two objects, a phenomenon not seen previously among more than 50 other binary asteroid systems studied by radar since 2000. (However, the majority of those binary asteroids consist of one large object and a much smaller satellite.) The reflectivity differences also appear in the Arecibo images and hint that the two objects may have different densities, compositions near their surfaces, or different surface roughnesses.
Radar images of the binary asteroid 2017 YE5 from NASA’s Goldstone Solar System Radar (GSSR). The observations, conducted on June 23, 2018, show two lobes, but do not yet show two separate objects. Image via GSSR/NASA/JPL-Caltech.
Bottom line: Asteroid 2017 YE5, which swept by Earth in late June 2018, has been observed to be a rare double asteroid – only fourth “equal mass” binary near-Earth asteroid ever detected,
The 1st meteorite was found after 5 days of walking and scouring a landscape of sand, thick tall grass, shrubs and thorn bushes. Meteorite expert Tomas Kohout (left) and gamekeeper Kegilwe Mogotsi in Botswana’s Central Kalahari Game Reserve. Image via University of Helsinki.
An international team of researchers in Botswana has found meteorites known to be fragments of asteroid 2018 LA, which astronomers detected just eight hours before it struck Earth’s atmosphere on June 2, 2018. The space rock was captured in videos (such as the one below) as it disintegrated at a height of 30 miles (50 km) in the atmosphere.
After searching for five days, the team found the first meteorite in Botswana’s Central Kalahari Game Reserve.
Meteor 2018 LA (ZLAF9B2)seen from farm between Ottosdal and Hartebeesfontein North West South Africa - YouTube
This is only the third time an asteroid has been detected before striking Earth’s atmosphere, and it’s the second time fragments of the inbound rock have been recovered. The first time was in October 7, 2008, when a 13-foot (4-meter) asteroid, designated as 2008 TC3, exploded over Sudan.
This time, astronomers discovered the small asteroid on a Saturday morning, June 2, and were surprised when its trajectory suggested it would pass very, very close to Earth just hours later. They detected the asteroid with the 60-inch (1.5-meter) telescope at Mt. Lemmon, which is part of the Catalina Sky Survey in Arizona.
Trajectory models suggest small asteroid ZLAF9B2 impacted our atmosphere over South Africa on June 2, and U.S. government sensors and satellites confirmed the event. After mounting a search, an international team of researchers has now found fragments of the asteroid. Image via projectpluto.com.
When it struck Earth’s atmosphere, asteroid 2018 LA produced an explosion with an intensity of about 1 kiloton, which suggests an estimated size for the space rock of 10 to 16 feet (3 to 5 meters) in diameter.
Artist’s concept of Kepler-186f, the 1st of 2 studied planets now thought to have seasons and a stable climate. Image via NASA Ames/JPL-Caltech/T. Pyle.
We sometimes hear the term Earth-like in describing exoplanets that might be similar to our own world. The terms Earth-like or Earth analog conjure up visions of alien oceans and continents, teeming with life. But how similar to Earth might such distant worlds really be? We still don’t know the answer to that question yet, but a new research study – announced by the Georgia Institute of Technology on June 28, 2018 – shows that there might indeed be some alien worlds that are quite similar to Earth in terms of their seasons and stable climates.
The study focuses on two known exoplanets, one about the same size as Earth and the other a super-Earth (larger than Earth but smaller than the gas giants Uranus or Neptune). The researchers found evidence that both planets likely have seasons and stable climates, just as Earth does. Kepler-186f is less than 10 percent larger then Earth, 500 light-years away in the constellation Cygnus the Swan. It is one of five known planets in that planetary system and orbits within the habitable zone, even though its host star is a red dwarf. Kepler-62f is about 40 percent larger than Earth, 1,200 light-years away in the constellation Lyra the Harp.
The research team, led by Georgia Tech astronomer Gongjie Li and graduate student Yutong Shan from the Harvard-Smithsonian Center for Astrophysics, used computer simulations to determine the axial tilt of each planet. The results indicated that the axial tilts of both planets are stable, like Earth’s, meaning that the planets would experience regular seasons and stable climates. That is good news in terms of how habitable the planets may be, although there are other factors to account for also of course, such as water, composition, type of atmosphere, etc.
Kepler-186f was the 1st Earth-sized exoplanet to be discovered in the habitable zone of another star. Image via NASA.
Artist’s concept of Kepler-62f, the 2nd planet found to have seasons and a stable climate. Image via NASA Ames/JPL-Caltech/T. Pyle.
Planets with highly variable axial tilts, like Mars, are less likely to have such stable environments. Mars’ axial tilt has been very unstable, swinging from zero to 60 degrees over billions of years, and is thought to be a key reason why Mars lost most of its water and turned into the cold, dry desert world we see today.
Earth’s axial tilt has been much more stable, varying from 22.1 to 24.5 degrees every 10,000 years or so. According to Li:
Mars is in the habitable zone in our solar system, but its axial tilt has been very unstable – varying from zero to 60 degrees. That instability probably contributed to the decay of the Martian atmosphere and the evaporation of surface water.
Mars is a good example, then, of what can happen when a planet does not have a stable axial tilt. A stable climate has been important for the continued evolution of life on Earth. The axial variations of Earth have been largely kept in check by the Earth’s large moon, which Mars doesn’t have. Mars and Earth strongly interact gravitationally with each other. If Earth had no moon, its spin axis would precess at the same rate as the orbital oscillation, which could cause large variations in the axial tilt. As Li explained:
It appears that both exoplanets are very different from Mars and the Earth because they have a weaker connection with their sibling planets. We don’t know whether they possess moons, but our calculations show that even without satellites, the spin axes of Kepler-186f and 62f would have remained constant over tens of millions of years.
View of Mars from the Mars Orbiter Mission (India). Mars’ wild axial changes prevented it from having a long-term stable climate. Image via ISRO.
As it stands now, both Kepler-186f and Kepler-62f are candidates for having habitable conditions on their surfaces, but there is still more we need to learn about them. The mass, composition and density of Kepler-186f are still unknown, crucial factors in helping to assess habitability. As Li noted:
Our study is among the first to investigate climate stability of exoplanets and adds to the growing understanding of these potentially habitable nearby worlds.
Planets with stable climates would be more likely to be able to support life, at least as we know it on Earth. What about planets with ever-changing climates? Shan is optimistic about even those worlds:
I don’t think we understand enough about the origin of life to rule out the possibility of their presence on planets with irregular seasons. Even on Earth, life is remarkably diverse and has shown incredible resilience in extraordinarily hostile environments. But a climatically stable planet might be a more comfortable place to start.
Earth’s axial tilt has remained quite stable, thanks largely to the presence of our large moon. Our stable, habitable climate has enabled life to thrive. Image via NASA/NOAA/GSFC/Jason Major.
A growing number of Earth-sized and super-Earth exoplanets have been discovered, including in the habitable zones of their stars, although it is too early to call any of them Earth-like yet specifically. This new research shows how some should have axial tilts and climates ideal for life to exist.
Bottom line: Finding other Earth-like planets is the holy grail of exoplanet research. The new findings showing stable axial tilts and likely stable climates on Kepler-186f and Kepler-62f are a big step in that direction. There is still much more work to be done, but scientists are now getting closer to discovering a world that is similar to ours – not only habitable, but perhaps, even teeming with life.
This is what a Ceres bright spot looks like, close-up. The Dawn spacecraft acquired this high-resolution color view of a sodium carbonate (salt) deposit on the southwest part of Cerealia Facula in Occator Crater on Ceres on June 22, 2018. Image via NASA/JPL-Caltech/UCLA/MPS/DLR/IDA/Jason Major.
Scientists are now getting their closest-ever views of Ceres, thanks to NASA’s Dawn spacecraft, which is now in its lowest orbit around the dwarf planet. As posted by NASA on July 2, 2018, the new images being sent back are fantastic – high-resolution views of the rugged surface and in particular, the famous “bright spots” in Occator Crater and elsewhere. These spots, which stand out starkly against the darker background surface, have intrigued scientists and the public alike ever since they were first discovered by Dawn when it arrived at Ceres in 2015.
Dawn reached its final, lowest orbit on June 6, and has been busy sending back thousands of images and other data about Ceres. This will help scientists to understand how Ceres formed and evolved over time, and how it appears to still be geologically active today, despite being so small compared to other planets.
The newest images from Ceres have a resolution of less than 5 meters per pixel. As Dr. Andreas Nathues, Framing Camera Lead Investigator, said:
The data exceeds all our expectations.
Here’s one of the images taken by the Dawn spacecraft of dwarf planet Ceres in February, 2015 – from a distance of nearly 29,000 miles (46,000 km) – that sent scientists and the public alike scrambling for explanations of the mysterious bright spots in Occator Crater on Ceres. Yes, from this distance, they looked like “alien headlights.” But, as further analysis and the much closer images on this page show, they’re really salt deposits, specifically sodium carbonate. Image via NASA/JPL-Caltech/UCLA/MPS/DLR/IDA.
Dawn reached its final, lowest orbit on June 6, 2018, and has been sending back images from much closer to Ceres’ surface. The new orbit now takes it to a distance of only 22 miles (35 km) above Ceres’ surface. This wider view is of the carbonate deposit on the southwest part of Cerealia Facula in Occator Crater on Ceres. Image via NASA/JPL-Caltech/UCLA/MPS/DLR/IDA.
Another view showing Cerealia Facula in Occator Crater. Image via NASA/JPL-Caltech/UCLA/MPS/DLR/IDA/Roman Tkachenko.
The bright spots, now known to be composed of sodium carbonate, are one of the biggest clues as to current activity, and the new images and data will help to finally answer the question of how they got there. Dawn has now taken the closest-ever images of Cerealia Facula, the largest deposit in the center of Occator Crater, after firing its ion engine last week to adjust its orbit trajectory. According to Dawn’s chief engineer and project manager, Marc Rayman, of NASA’s Jet Propulsion Laboratory, Pasadena, California:
Acquiring these spectacular pictures has been one of the greatest challenges in Dawn’s extraordinary extraterrestrial expedition, and the results are better than we had ever hoped. Dawn is like a master artist, adding rich details to the otherworldly beauty in its intimate portrait of Ceres.
Dawn’s new orbit now takes it to a distance of only 22 miles (35 km) above Ceres’ surface. Previously, the lowest orbit was 240 miles (385 km), so this is a big improvement for being able to see more details on the surface, including in the spots.
Another view of Cerealia Facula in Occator Crater. Image via NASA/JPL-Caltech/UCLA/MPS/DLR/IDA.
Another view of Cerealia Facula and other nearby deposits in Occator Crater. Image via NASA/JPL-Caltech/UCLA/MPS/DLR/IDA.
View of Vinalia Faculae in Occator Crater. Image via NASA/JPL-Caltech/UCLA/MPS/DLR/IDA.
The spots, evaporate deposits composed of sodium carbonate, are thought to be left over from when water came up to the surface from deeper below and then evaporated in the extremely tenuous and sporadic water vapor “atmosphere.” That water could be either from a shallow sub-surface reservoir or from a deeper reservoir of salty brines percolating upward through fractures. The deposits in Occator Crater are the largest and brightest of these deposits. As with many discoveries in planetary science, they were completely unexpected, and show that Ceres is not just an inert ball of rock and ice. As noted by Carol Raymond, the Dawn mission’s principal investigator:
The first views of Ceres obtained by Dawn beckoned us with a single, blinding bright spot. Unraveling the nature and history of this fascinating dwarf planet during the course of Dawn’s extended stay at Ceres has been thrilling, and it is especially fitting that Dawn’s last act will provide rich new data sets to test those theories.
Landslides on the rim of Occator Crater. Image via NASA/JPL-Caltech/UCLA/MPS/DLR/IDA.
Ahuna Mons on Ceres. Image via NASA/JPL-Caltech/UCLA/Max Planck Institute for Solar System Studies/German Aerospace Center/IDA/Planetary Science Institute.
Ceres is also considered to be an asteroid, and is the largest object in the main asteroid belt between Mars and Jupiter. As well as the carbonate deposits, Dawn also found other unusual features, such as Ahuna Mons, a conical mountain which sits in isolation on Ceres’ surface, with nothing else like it nearby. It is approximately 3 miles (5 kilometers) tall and its formation is thought to involve cryovolcanism (an icy form of volcanism).
More images from Dawn are available here and information about the mission overall is here.
False-color image of Ceres from Dawn, with Occator Crater and its carbonate deposits near the center. Image via NASA/JPL-Caltech/UCLA/MPS/DLR/IDA.
Bottom line: Ceres is a bizarre world, the largest in the main asteroid belt, with bright carbonate deposits splattered on its surface, a weird isolated conical mountain, landslides and a possible subsurface layer of water. NASA’s Dawn spacecraft has now taken the highest-resolution images of Ceres, showing us how just unique this dwarf planet really is.