It is a well-known astronomical convention that Earth has only one natural satellite, which is known (somewhat uncreatively) as “the Moon”. However, astronomers have known for a little over a decade that Earth also has a population of what are known as “transient Moons”. These are a subset of Near-Earth Objects (NEOs) that are temporarily scooped up by Earth’s gravity and assume orbits around our planet.
According to a new study by a team of Finish and American astronomers, these temporarily-captured orbiters (TCOs) could be studied with the Large Synoptic Survey Telescope (LSST) in Chile – which is expected to become operational by 2020. By examining these objects with the next-generation telescope, the study’s authors argue that we stand to learn a great deal about NEOs and even begin conducting missions to them.
Rather than resolving the dispute, additional observations only deepened the mystery, even giving rise to suggestions that it might be an extra-terrestrial solar sail. For this reason, scientists are very interested in finding other examples of ‘Oumuamua-like objects. According to a recent study by a team of Harvard astrophysicists, it is possible that interstellar objects enter our system and end up falling into in our Sun somewhat regularly.
Roughly 4.5 billion years ago, scientists theorize that Earth experienced a massive impact with a Mars-sized object (named Theia). In accordance with the Giant Impact Hypothesis, this collision placed a considerable amount of debris in orbit, which eventually coalesced to form the Moon. And while the Moon has remained Earth’s only natural satellite since then, astronomers believe that Earth occasionally shares its orbit with “mini-moons”.
These are essentially small and fast-moving asteroids that largely avoid detection, with only one having been observed to date. But according to a new study by an international team of scientists, the development of instruments like the Large Synoptic Survey Telescope (LSST) could allow for their detection and study. This, in turn, will present astronomers and asteroid miners with considerable opportunities.
The study which details their findings recently appeared in the Frontiers in Astronomy and Space Sciences under the title “Earth’s Minimoons: Opportunities for Science and Technology“. The study was led by Robert Jedicke, a researcher from the University of Hawaii at Manoa, and included members from the Southwest Research Institute (SwRI), the University of Washington, the Luleå University of Technology, the University of Helsinki, and the Universidad Rey Juan Carlos.
As a specialist in Solar System bodies, Jedicke has spent his career studying the orbit and size distributions of asteroid populations – including Main Belt and Near Earth Objects (NEOs), Centaurs, Trans-Neptunian Objects (TNOs), comets, and interstellar objects. For the sake of their study, Jedicke and his colleagues focused on objects known as temporarily-captured orbiters (TCO) – aka. mini-moons.
These are essentially small rocky bodies – thought to measure up to 1-2 meters (3.3 to 6.6 feet) in diameter – that are temporarily gravitationally bound to the Earth-Moon system. This population of objects also includes temporarily-captured flybys (TCFs), asteroids that fly by Earth and make at least one revolution of the planet before escaping orbit or entering our atmosphere.
As Dr. Jedicke explained in a recent Science Dailynews release, these characteristics is what makes mini-moons particularly hard to observe:
“Mini-moons are small, moving across the sky much faster than most asteroid surveys can detect. Only one minimoon has ever been discovered orbiting Earth, the relatively large object designated 2006 RH120, of a few meters in diameter.”
This object, which measured a few meters in diameter, was discovered in 2006 by the Catalina Sky Survey (CSS), a NASA-funded project supported by the Near Earth Object Observation Program (NEOO) that is dedicated to discovering and tracking Near-Earth Asteroids (NEAs). Despite improvements over the past decade in ground-based telescopes and detectors, no other TCOs have been detected since.
After reviewing the last ten years of mini-moon research, Jedicke and colleagues concluded that existing technology is only capable of detecting these small, fast moving objects by chance. This is likely to change, according to Jedicke and his colleagues, thanks to the advent of the Large Synoptic Survey Telescope (LSST), a wide-field telescope that is currently under construction in Chile.
Once complete, the LSST will spend the ten years investigating the mysteries of dark matter and dark energy, detecting transient events (e.g. novae, supernovae, gamma ray bursts, gravitational lensings, etc.), mapping the structure of the Milky Way, and mapping small objects in the Solar System. Using its advanced optics and data processing techniques, the LSST is expected to increase the number of cataloged NEAs and Kuiper Belt Objects (KBOs) by a factor of 10-100.
But as they indicate in their study, the LSST will also be able to verify the existence of TCOs and track their paths around our planet, which could result in exciting scientific and commercial opportunities. As Dr. Jedicke indicated:
“Mini-moons can provide interesting science and technology testbeds in near-Earth space. These asteroids are delivered towards Earth from the main asteroid belt between Mars and Jupiter via gravitational interactions with the Sun and planets in our solar system. The challenge lies in finding these small objects, despite their close proximity.”
When it is completed in a few years, it is hoped that the LSST will confirm the existence of mini-moons and help track their orbits around Earth. This will be possible thanks to the telescope’s primary mirror (which measures 8.4 meters (27 feet) across) and its 3200 megapixel camera – which has a tremendous field of view. As Jedicke explained, the telescope will be able to cover the entire night sky more than once a week and collect light from faint objects.
With the ability to detect and track these small, fast objects, low-cost missions may be possible to mini-Moons, which would be a boon for researchers seeking to learn more about asteroids in our Solar System. As Dr Mikael Granvik – a researcher from the Luleå University of Technology, the University of Helsinki, and a co-author on the paper – indicated:
“At present we don’t fully understand what asteroids are made of. Missions typically return only tiny amounts of material to Earth. Meteorites provide an indirect way of analyzing asteroids, but Earth’s atmosphere destroys weak materials when they pass through. Mini-moons are perfect targets for bringing back significant chunks of asteroid material, shielded by a spacecraft, which could then be studied in detail back on Earth.”
As Jedicke points out, the ability to conduct low-cost missions to objects that share Earth’s orbit will also be of interest to the burgeoning asteroid mining industry. Beyond that, they also offer the possibility of increasing humanity’s presence in space.
“Once we start finding mini-moons at a greater rate they will be perfect targets for satellite missions,” he said. “We can launch short and therefore cheaper missions, using them as testbeds for larger space missions and providing an opportunity for the fledgling asteroid mining industry to test their technology… I hope that humans will someday venture into the solar system to explore the planets, asteroids and comets — and I see mini-moons as the first stepping stones on that voyage.”
In the past few decades, thanks to improvements in ground-based and space-based observatories, astronomers have discovered thousands of planets orbiting neighboring and distant stars (aka. extrasolar planets). Strangely enough, it is these same improvements, and during the same time period, that enabled the discovery of more astronomical bodies within the Solar System.
These include the “minor planets” of Eris, Sedna, Haumea, Makemake, and others, but also the hypothesized planetary-mass objects collectively known as Planet 9 (or Planet X). In a new study led by Northern Arizona University and the Lowell Observatory, a team of researchers hypothesize that the Large Synoptic Survey Telescope (LSST) – a next-generation telescope that will go online in 2022 – has a good chance of finding this mysterious planet.
Their study, titled “On the detectability of Planet X with LSST“, recently appeared online. The study was led by David E. Trilling, an astrophysicist from the Northern Arizona University and the Lowell Observatory, and included Eric C. Bellm from the University of Washington and Renu Malhotra of the Lunar and Planetary Laboratory at The University of Arizona.
Located on the Cerro Pachón ridge in north-central Chile, the 8.4-meter LSST will conduct a 10-year survey of the sky that will deliver 200 petabytes worth of images and data that will address some of the most pressing questions about the structure and evolution of the Universe and the objects in it. In addition to surveying the early Universe in order to understand the nature of dark matter and dark energy, it will also conduct surveys of the remote areas of the Solar System.
Planet 9/X is one such object. In recent years, the existence of two planetary-mass bodies have been hypothesized to explain the orbital distribution of distant Kuiper Belt Objects. While neither planet is thought to be exceptionally faint, the sky locations of these planets are poorly constrained – making them difficult to pinpoint. As such, a wide area survey is needed to detect these possible planets.
In 2022, the LSST will carry out an unbiased, large and deep survey of the southern sky, which makes it an important tool when it comes to the search of these hypothesized planets. As they state in their study:
“The possibility of undiscovered planets in the solar system has long fascinated astronomers and the public alike. Recent studies of the orbital properties of very distant Kuiper belt objects (KBOs) have identified several anomalies that may be due to the gravitational influence of one or more undiscovered planetary mass objects orbiting the Sun at distances comparable to the distant KBOs.
These studies include Trujillo & Sheppard’s 2014 study where they noticed similarities in the orbits of distant Trans-Neptunian Objects (TNOs) and postulated that a massive object was likely influencing them. This was followed by a 2016 study by Sheppard & Trujillo where they suggested that the high perihelion objects Sedna and 2012 VP113 were being influence by an unknown massive planet.
This was followed in 2016 by Konstantin Batygin and Michael E. Brown of Caltech suggesting that an undiscovered planet was the culprit. Finally, Malhotra et al. (2016) noted that the most distant KBOs have near-integer period ratios, which was suggestive of a dynamical resonance with a massive object in the outer Solar System. Between these studies, various mass and distance estimates were formed that became the basis of the search for this planet.
Overall, these estimates indicated that Planet 9/X was a super-Earth with anywhere between 5 to 20 Earth masses, and orbited the Sun at a distance of between 150 – 600 AU. Concurrently, these studies have also attempted to narrow down where this Super-Earth’s orbit will take it throughout the outer Solar System, as evidenced by the perturbations it has on KBOs.
Unfortunately, the predicted locations and brightness of the object are not yet sufficiently constrained for astronomers to simply look in the right place at the right time and pick it out. In this respect, a large area sky survey must be carried out using moderately large telescopes with a very wide field of view. As Dr. Trilling told Universe Today via email:
“The predicted Planet X candidates are not particularly faint, but the possible locations on the sky are not very well constrained at all. Therefore, what you really need to find Planet X is a medium-depth telescope that covers a huge amount of sky. This is exactly LSST. LSST’s sensitivity will be sufficient to find Planet X in almost all its (their) predicted configurations, and LSST will cover around half of the known sky to this depth. Furthermore, the cadence is well-matched to finding moving objects, and the data processing systems are very advanced. If you were going to design a tool to find Planet X, LSST is what you would design.”
However, the team also acknowledges that within certain parameters, Planet 9/X may not be detectable by the LSST. For example, it is possible that that there is a very narrow slice of predicted Planet 9/X parameters where it might be slightly too faint to be easily detected in LSST data. In addition, there is also a small possibility that irregularities in the Planet 9/X cadence might lead to it being missed.
There is the even the unlikely ways in which Planet 9/X could go undetected in LSST data, which would come down to a simple case of bad luck. However, as Dr. Trilling indicated, the team is prepared for these possibilities and is hopeful they will find Planet 9/X, assuming there’s anything to find:
“The more likely conclusion if planet X is not detected in LSST data is that planet X doesn’t exist – or at least not the kind of planet X that has been predicted. In this case, we’ve got to work harder to understand how the Universe created this pattern of orbits in the outer Solar System that I described above. This is a really fun part of science: make a prediction and test it, and find that the result is rarely what is predicted. So now we’ve got to work harder to understand the universe. Hopefully this new understanding makes new predictions that we then can test, and we repeat the cycle.”
The existence of Planet 9/X has been one of the more burning questions for astronomers in recent years. If its existence can be confirmed, astronomers may finally have a complete picture of the Solar System and its dynamics. If it’s existence can be ruled out, this will raise a whole new series of questions about what is going on in the Outer Solar System!
We humans have an insatiable hunger to understand the Universe. As Carl Sagan said, “Understanding is Ecstasy.” But to understand the Universe, we need better and better ways to observe it. And that means one thing: big, huge, enormous telescopes.
In this series we’ll look at 6 of the world’s Super Telescopes:
While the world’s other Super Telescopes rely on huge mirrors to do their work, the LSST is different. It’s a huge panoramic camera that will create an enormous moving image of the Universe. And its work will be guided by three words: wide, deep, and fast.
While other telescopes capture static images, the LSST will capture richly detailed images of the entire available night sky, over and over. This will allow astronomers to basically “watch” the movement of objects in the sky, night after night. And the imagery will be available to anyone.
At the heart of the LSST is its enormous digital camera. It weighs over three tons, and the sensor is segmented in a similar way that other Super Telescopes have segmented mirrors. The LSST’s camera is made up of 189 segments, which together create a camera sensor about 2 ft. in diameter, behind a lens that is over 5 ft. in diameter.
Each image that the LSST captures is 40 times larger than the full moon, and will measure 3.2 gigapixels. The camera will capture one of these wide-field images every 20 seconds, all night long. Every few nights, the LSST will give us an image of the entire available night sky, and it will do that for 10 years.
“The LSST survey will open a movie-like window on objects that change brightness, or move, on timescales ranging from 10 seconds to 10 years.” – LSST: FROM SCIENCE DRIVERS TO REFERENCE DESIGN AND ANTICIPATED DATA PRODUCTS
The LSST will capture a vast, movie-like image of over 40 billion objects. This will range from distant, enormous galaxies all the way down to Potentially Hazardous Objects as small as 140 meters in diameter.
There’s a whole other side to the LSST which is a little more challenging. We get the idea of an in-depth, moving, detailed image of the sky. That’s intuitively easy to engage with. But there’s another side, the data mining challenge.
The Data Challenge
The whole endeavour will create an enormous amount of data. Over 15 terabytes will have to be processed every night. Over its 10 year lifespan, it will capture 60 petabytes of data.
Once data is captured by the LSST, it will travel via two dedicated 40 GB lines to the Data Processing and Archive Center. That Center is a super-computing facility that will manage all the data and make it available to users. But when it comes to handling the data, that’s just the tip of the iceberg.
“LSST is a new way to observe, and gaining knowledge from the Big Data LSST delivers is indeed a challenge.” – Suzanne H. Jacoby, LSST
The sheer amount of data created by the LSST is a challenge that the team behind it saw coming. They knew they would have to build the capacity of the scientific community in advance, in order to get the most out of the LSST.
As Suzanne Jacoby, from the LSST team, told Universe today, “To prepare the science community for LSST Operations, the LSST Corporation has undertaken an “Enabling Science” effort which funds the LSST Data Science Fellowship Program (DSFP). This two-year program is designed to supplement existing graduate school curriculum and explores topics including statistics, machine learning, information theory, and scalable programming.”
The Nature of Dark Matter and Understanding Dark Energy
Contributing to our understanding Dark Energy and Dark Matter is a goal of all of the Super Telescopes. The LSST will map several billion galaxies through time and space. It will help us understand how Dark Energy behaves over time, and how Dark Matter affects the development of cosmic structure.
Cataloging the Solar System
The raw imaging power of the LSST will be a game-changer for mapping and cataloguing our Solar System. It’s thought that the LSST could detect between 60-90% of all potentially hazardous asteroids (PHAs) larger than 140 meters in diameter, as far away as the main asteroid belt. This will not only contribute to NASA’s goal of identifying threats to Earth posed by asteroids, but will help us understand how planets formed and how our Solar System evolved.
Exploring the Changing Sky
The repeated imaging of the night sky, at great depth and with excellent image quality, should tell us a lot about supernovae, variable stars, and possible other events we haven’t even discovered yet. There are always surprising results whenever we build a new telescope or send a probe to a new destination. The LSST will probably be no different.
Milky Way Structure & Formation
The LSST will give us an unprecedented look at the Milky Way. It will survey over half of the sky, and will do so repeatedly. Hundreds of times, in fact. The end result will be an enormously detailed look at the motion of millions of stars in our galaxy.
Perhaps the best part of the whole LSST project is that the all of the data will be available to everyone. Anyone with a computer and an internet connection will be able to access LSST’s movie of the Universe. It’s warm and fuzzy, to be sure, to have the results of large science endeavours like this available to anyone. But there’s more to it. The LSST team suspects that the majority of the discoveries resulting from its rich data will come from unaffiliated astronomers, students, and even amateurs.
It was designed from the ground up in this way, and there will be no delay or proprietary barriers when it comes to public data access. In fact, Google has signed on as a partner with LSST because of the desire for public access to the data. We’ve seen what Google has done with Google Earth and Google Sky. What will they come up with for Google LSST?
The Sloan Digital Sky Survey (SDSS), a kind of predecessor to the LSST, was modelled in the same way. All of its data was available to astronomers not affiliated with it, and out of over 6000 papers that refer to SDSS data, the large majority of them were published by astronomers not affiliated with SDSS.
We’ll have to wait a while for all of this to come our way, though. First light for the LSST won’t be until 2021, and it will begin its 10 year run in 2022. At that time, be ready for a whole new look at our Universe. The LSST will be a game-changer.
Clearly I need to learn to be more specific when I write these articles. Everything time I open my mouth, I need to prepare for the collective imagination of the viewers.
We did a whole article about the biggest things in the Universe, and identified superclusters of galaxies as the best candidate. Well, the part of superclusters actually gravitationally bound enough to eventually merge together in the future. But you had other ideas, including dark energy, or the Universe itself as the biggest thing. Even love? Aww.
One intriguing suggestion, though, is the idea of the vast cosmic voids between galaxies. Hmm, is the absence of something a thing? Whoa, time to go to art school and talk about negative space.
Ah well, who cares? It’s a super interesting topic, so let’s go ahead and talk about voids.
When most people imagine the expansion of the Universe after the Big Bang, they probably envision an equally spaced smattering of galaxies zipping away from one another. And that’s pretty accurate at the smallest scales.
But at the largest scales, like when you can see billions of light-years in a cube that fits on your computer screen, then a larger structure starts to take shape.
It looks less like an explosion, and more like a tasty tasty sponge cake, with huge filaments, walls, and the vast gaps in between. The gaps, the voids, the supervoids, are the point of today’s article, but to understand the gaps, we’ve got to understand why the Universe is clumped up the way it is.
Run the Universe clock backwards, all the way to the beginning, to a fraction of a second after the Big Bang. When the entire cosmos was compressed down into a tiny region of superheated plasma.
Although it was mostly uniform in density, there were slight variations – quantum fluctuations in spacetime itself. And as the Universe expanded, those differences were magnified. What started out as tiny differences in the density of matter at the smallest scale, turned into regions of higher and lower density of matter in the Universe.
Here we are, 13.8 billion years after the Big Bang, and we can see how the microscopic variations at the beginning of time were magnified to the largest scales. Instead of individual galaxies, we see huge walls containing thousands of galaxies; filaments of galaxies connect in nodes. These structures are huge; hundreds of millions of light-years across, containing thousands of galaxies. But the gaps, the voids, between these clusters can be even larger.
Astronomers first started thinking about these voids back in the 1970s, when the first large-scale surveys of the Universe were made. By measuring the redshift of galaxies, and determining how fast they were speeding away from us, astronomers started to realize that the distribution of galaxies wasn’t even.
Some galaxies were relatively close, but then there were huge gaps in distance, and then another cluster of galaxies collected together.
Over the last few decades, astronomers have built sophisticated 3-dimensional models that map out the Universe in the largest scales. The Sloan Digital Sky Survey, updated in 2009, has provided the most accurate map so far. The Large Synoptic Survey Telescope, destined for first light in a few years will take this to the next level.
The largest void that we currently know of is known as the Giant Void (original, I know), and it’s located about 1.5 billion light-year away. It has a diameter of 1 billion to 1.3 billion light-years across.
To be fair, these regions aren’t really completely empty. They just have less density than the regions with galaxies. In general, they’ve got about a tenth the density of matter that’s average for the Universe.
Which means that there’s still gas and dust in these regions, as well as dark matter. There will still be stars and galaxies out in the middle of those voids. Even the Giant Void has 17 separate galaxy clusters inside it.
You might imagine continuing to scale outward. Maybe you’re wondering if the this spongy distribution of matter is actually just the next step to an even larger structure, and so on, and so on. But it isn’t. In fact, astronomers call this “the End of Greatness”, because it doesn’t seem like there’s any larger structure to the Universe.
As the expansion of the Universe continues, these voids are going to get even larger. The walls and filaments connecting clusters of galaxies will stretch and break. The voids will merge with each other, and only gravitationally bound galaxy clusters will remain as islands, adrift in the expanding emptiness.
The full scale of the observable Universe is truly mind boggling. We’re here in this tiny corner of the Local Group, which is part of the Virgo Supercluster, which is perched on the precipice of vast cosmic voids. So much to explore, so let’s get to work.
If you follow some of my other shows, like Astronomy Cast and the Weekly Space Hangout. Of course you do, what a ridiculous thing to say… “if”. Anyway, since you follow those other shows, you know I’m currently obsessed with an upcoming observatory called the Large Synoptic Survey Telescope.
Obsessions are best when they’re shared. So today, I invite you to become as obsessed as I am about the LSST.
In the past, astronomers focused on building bigger telescopes at more remote locations so they could peer more deeply into the past, to resolve the faintest objects, to see right to the edge of the observable Universe.
But there’s a whole other dimension to the Universe: time. And by taking advantage of time, astronomers have made some of the most momentous discoveries in the history of astronomy.
The Large Synoptic Survey Telescope is all about time. Watching the sky over and over, night after night, watching for anything that changes.
First, let’s talk about some of the kinds of discoveries that can be made when you’re watching the sky for changes.
Perhaps the best example of this is the Mira Variable. These are red giants at the very end of their stellar evolution, almost out of usable hydrogen to burn in their cores. As their stellar flame flickers out, the light pressure can no longer hold against the gravity pulling the star inward. The star compresses in on itself, raising the temperature and pressure, allowing more fusion. It flares up again, and brightens in our sky.
Astronomers discovered that there’s a very specific relationship to the brightness and rate that this brightening happens. In other words, if you know how often a Mira variable flares up, you know how intrinsically bright it is. And if you know how bright it is, you can calculate how far away it is. Even in other galaxies.
That’s what Edwin Hubble did when he surveyed Mira variables in other galaxies. He discovered that most galaxies are actually speeding away from us in all directions, leading to the theory of the Big Bang.
Thanks to time, we understand that we life in an expanding Universe that originated from a single point, 13.8 billion years ago.
Let me give you another example: the discovery of gamma ray bursts. In the 1960s, the US launched a group of satellites as part of the Vela Mission. They had no astronomical purpose, they were designed to watch for the specific gamma ray signature from an unauthorized nuclear weapons test. But instead of nuclear explosions, they detected massive blasts of gamma radiation coming from deep space. These blasts only last for a few seconds and then fade away, leaving a faint afterglow that also fades.
We now know that gamma ray bursts mark the deaths of the largest stars in the Universe, and the formations of new black holes. Other gamma ray bursts signal the collisions of exotic stellar remnants, like neutron stars and white dwarfs.
I can give you many more examples, where the dimension of time lead to a discovery in astronomy:
In 1930, Clyde Tombaugh compared pairs of photographic plates, switching back and forth over and over, looking for any object that moved position. This was how he discovered Pluto. In fact, this same technique is used by astronomers to find other dwarf planets, asteroids and comets to this day.
Astronomers return again and again to galaxies in the night sky, looking for any that have a new star in them. This is a tell tale sign of a supernova, the explosion of a star much more massive than our Sun. Some of these supernovae allowed astronomers to discover dark energy, that the expansion of the Universe is accelerating.
This is what time can help us discover.
Now, on to the Large Synoptic Survey Telescope. The observatory is currently under construction in north-central Chile, where many of the world’s most powerful telescopes are located.
Its main mirror is 8.4 meters across. Just for comparison, ESO’s Very Large Telescopes are 8.2 metres across. The Gemini Observatories are 8.1 metres across. The Keck Observatory is 10 metres wide. What I’m saying here, is that the LSST is plenty big.
But that’s not its most important feature. LSST is fast. When I say fast, I’m saying this in the astronomical sense, which means that it can gather a lot of light over a wide area on the sky in a very short amount of time. While Keck, for example, can focus incredibly deeply at a tiny spot in the sky, LSST gulps light across a huge region of the sky.
It’ll be able to see 3.5-degrees of the sky, every time it takes a picture. The Sun and the Moon are about 0.5-degrees across in the sky, so imagine a grid 7 moons across and 7 moons high.
It’ll take a 15-second exposure every 20 seconds. In the amount of time you’ll spend watching this video, the LSST could have taken dozens of high resolution images of the sky.
In fact, it’ll completely image the available sky every few nights. And then petabytes of data will be released onto the internet, available for astronomers to pore over.
Want to find asteroids, just look through the LSST records. Want to know how fast the Universe is expanding, dig through the data. LSST is going to look everywhere and anywhere every couple of nights, and then provide this data to scientists to make discoveries.
Assuming the construction isn’t delayed, the Large Synoptic Survey Telescope should see first light in 2019. Shortly after that, it’ll be disgorging mountains of astronomical data onto the internet.
And shortly after that, I suspect, we’ll start to hear everything the Universe was doing when we weren’t watching before. Because now, thanks to LSST, we’ll be watching all the time.
Astronomers have reported the discovery of a star that passed within the outer reaches of our Solar System just 70,000 years ago, when early humans were beginning to take a foothold here on Earth. The stellar flyby was likely close enough to have influenced the orbits of comets in the outer Oort Cloud, but Neandertals and Cro Magnons – our early ancestors – were not in danger. But now astronomers are ready to look for more stars like this one.
Lead author Eric Mamajek from the University of Rochester and collaborators report in The Closest Known Flyby Of A Star To The Solar System (published in Astrophysical Journal on February 12, 2015) that “the flyby of this system likely caused negligible impact on the flux of long-period comets, the recent discovery of this binary highlights that dynamically important Oort Cloud perturbers may be lurking among nearby stars.”
The star, named Scholz’s star, was just 8/10ths of a light year at closest approach to the Sun. In comparison, the nearest known star to the Sun is Proxima Centauri at 4.2 light years.
While the internet has been rife with threads and accusations of a Nemesis star that is approaching the inner Solar System and is somehow being “hidden” by NASA, this small red dwarf star with a companion represents the real thing.
In 1984, the paleontologists David Raup and Jack Sepkoski postulated that a dim dwarf star, now widely known on the internet as the Nemesis Star, was in a very long period Solar orbit. The elliptical orbit brought the proposed star into the inner Solar System every 26 million years, causing a rain of comets and mass extinctions on that time period. By no coincidence, because of the sheer numbers of red dwarfs throughout the galaxy, Scholz’s star nearly fits such a scenario. Nemesis was proposed to be in a orbit extending 95,000 A.U. compared to Scholz’s nearest flyby distance of 50,000 A.U. Recent studies of impact rates on Earth, the Moon and Mars have discounted the existence of a Nemesis star (see New Impact Rate Count Lays Nemesis Theory to Rest, Universe Today, 8/1/2011)
But Scholz’s star — a real-life Oort Cloud perturber — was a small red dwarf star star with a M9 spectral classification. M-class stars are the most common star in our galaxy and likely the whole Universe, as 75% of all stars are of this type. Scholz’s is just 15% of the mass of our Sun. Furthermore, Scholz’s is a binary star system with the secondary being a brown dwarf of class T5. Brown Dwarfs are believed to be plentiful in the Universe but due to their very low intrinsic brightness, they are very difficult to discover … except, as in this case, as companions to brighter stars.
The astronomers reported that their survey of new astrometric data of nearby stars identified Scholz’s as an object of interest. The star’s transverse velocity was very low, that is, the stars sideways motion. Additionally, they recognized that its radial velocity – motion towards or away from us, was quite high. For Scholz’s, the star was speeding directly away from our Solar System. How close could Scholz’s star have been to our system in the past? They needed more accurate data.
The collaborators turned to two large telescopes in the southern hemisphere. Spectrographs were employed on the Southern African Large Telescope (SALT) in South Africa and the Magellan telescope at Las Campanas Observatory, Chile. With more accurate trangental and radial velocities, the researchers were able to calculate the trajectory, accounting for the Sun’s and Scholz’s motion around the Milky Way galaxy.
Scholz’s star is an active star and the researchers added that while it was nearby, it shined at a dimly of about 11th magnitude but eruptions and flares on its surface could have raised its brightness to visible levels and could have been seen as a “new” star by primitive humans of the time.
At present, Scholz’s star is 20 light years away, one of the 70 closest stars to our Solar System. However, the astronomers calculated, with a 98% certainty, that Scholz’s passed within 0.5 light years, approximately 50,000 Astronomical Units (A.U.) of the Sun.
An A.U. is the mean distance from the Earth to the Sun and 50,000 is an important mile marker in our Solar System. It is the outer reaches of the Oort Cloud where billions of comets reside in cold storage, in orbits that take hundreds of thousands of years to circle the Sun.
With this first extraordinary close encounter discovered, the collaborators of this paper as well as other researchers are planning new searches for “Nemesis” type stars. The Large Synoptic Survey Telescope (LSST) and other telescopes within the next decade will bring an incredible array of data sets that will uncover many more red dwarf, brown dwarf and possibly orphan planets roaming in nearby space. Some of these could likewise be traced to past or future near misses to the Sun and Earth system.
The world’s largest-ever digital camera has received the green light to move forward with development. The 3,200-megapixel camera for the Large Synoptic Survey Telescope (LSST) will snap the widest, deepest and fastest views of the night sky ever observed, providing unprecedented details of the Universe. Astronomers say the LSST will help uncover some of the biggest mysteries in astronomy.
The SLAC National Accelerator Laboratory announced this week they have received key “Critical Decision 2” approval from the Department of Energy.
“This important decision endorses the camera fabrication budget that we proposed,” said LSST Director Steven Kahn. “Together with the construction funding we received from the National Science Foundation in August, it is now clear that LSST will have the support it needs to be completed on schedule.”
Set to begin science operations in 2022, the LSST will create an unprecedented archive of astronomical data that will track billions of remote galaxies, helping researchers study galaxy formation. It will rapidly scan the sky, charting objects that change or move: from exploding supernovae to potentially hazardous near-Earth asteroids and create high resolution time-lapse videos of these objects and a 3-D map of the Universe. It will also help us better understand mysterious dark matter and dark energy, which make up 95 percent of the Universe
The camera itself will be the size of a small car and weigh more than 3 tons. It will be able to take up to 800 panoramic images each night and can cover the sky twice each week. Researchers say it will have the ability to reach faint objects twenty times faster than currently possible over the entire visible sky. Scientists anticipate LSST will generate 6 million gigabytes of data per year.
The telescope will have an 8.4-meter-diameter primary mirror that has an integrated 5-meter-diameter tertiary mirror. This mirror has already been fabricated at the University of Arizona’s Mirror Lab. The outer ring serves as the first mirror, and is called M1. Another more steeply curved mirror, M3, is carved out of the center. It has a 3-degree field of view.
LSST will be taking digital images of the entire visible southern sky every few nights from atop the Cerro Pachón mountain in Chile.
Amateur and armchair astronomers will be happy to know that data from the LSST will be shared publicly and become available quickly via the internet. Researchers involved are planning to involve the public, including students, by using portals like Google Sky or World Wide Telescope, as well as developing research projects that can be done by students in classroom settings, and the public at home and at settings like science museums. They also hope to utilize citizen science projects like Cosmoquest and Galaxy Zoo.
With the latest approval from the DOE, the LSST team can now move forward with the development of the camera. There will be a “Critical Decision 3” review process next summer, which will be the last requirement before actual fabrication of the camera can begin. Components of the camera will be built by an international collaboration of labs and universities.
Look up in a clear night sky. How many moons do you see? Chances are, you’re only going to count to one. Admittedly, if you count any higher and you’re not alone, you may get some funny looks cast in your direction. But even though you may not be able to actually see them, there may very well be more moons out there orbiting our planet.
For the time being, anyway.
Today, Earth has one major moon in orbit around it. (Technically the Earth-Moon system orbits around a common center of gravity, called the barycenter, but that’s splitting hairs for the purpose of this story.) At one time Earth may have had two large moons until the smaller eventually collided into the larger, creating the rugged lump we now call the farside highlands. But, that was 4 billion years ago and again not what’s being referred to here.
Right now, at his moment, Earth may very well have more than the one moon we see in the night sky. Surprise.
Of course, it would be a very small moon. Perhaps no more than a meter across. But a moon nonetheless. And there could even be others – many others – much smaller than that. Little bits of solar system leftovers, orbiting our planet even farther out than the Moon we all know and love, coming and going in short-lived flings with Earth without anyone even knowing.
This is what has been suggested by researcher Mikael Granvik of the University of Helsinki in Finland. He and his colleagues have created computer simulations of asteroids believed to be occupying the inner solar system, and what the chances are that any number of them could be captured into Earth orbit at any given time.
The team’s results, posted Dec. 20 in the science journal Icarus, claim it’s very likely that small asteroids would be temporarily captured into orbit (becoming TCOs, or temporarily captured objects) on a regular basis, each spending about nine months in up to three revolutions around Earth before heading off again.
Some objects, though, might hang around even longer… in the team’s simulations one TCO remained in orbit for 900 years.
“There are lots of asteroids in the solar system, so chances for the Earth to capture one at any time is, in a sense, not surprising,” said co-author Jeremie Vauballion, an astronomer at the Paris Observatory.
In fact, the team suspects that there’s most likely a TCO out there right now, perhaps a meter or so wide, orbiting between 5 and 10 times the distance between Earth and the Moon. And there could be a thousand smaller ones as well, up to 10 centimeters wide.
So if these moons are indeed out there, why don’t we know about them?
Put simply, they are too small, too far, and too dark.
At that distance an object the size of a writing desk is virtually undetectable with the instruments we have now.. especially if we don’t even know exactly where to look. But in the future the Large Synoptic Survey Telescope (LSST) may, once completed, be able to spot these tiny satellites with its 3200-megapixel camera.
Once spotted, TCOs could become targets of exploration. After all, they are asteroids that have come to us, which would make investigation all the easier – not to mention cheaper – much more so than traveling to and back from the main asteroid belt.
“The price of the mission would actually be pretty small,” Granvik said. And that, of course, makes the chances of such a mission getting approved all the better.
Read more on David Shiga’s article on New Scientist here.