Astronomers have painstakingly built models of the asteroid population, and those models predict that there will be ~1 km sized asteroids that orbit closer to the Sun than Venus does. The problem is, nobody’s been able to find one. Until now.
Astronomers working with the Zwicky Transient Facility say they’ve finally found one. But this one’s bigger, at about 2 km. If its existence can be confirmed, then asteroid population models may have to be updated.
Astronomers at Caltech’s Zwicky Transient Facility (ZTF) have discovered an asteroid that orbits inside Venus. Though other asteroids have a portion of their orbit inside Venus’, this is the first one with an orbit that is completely inside Venus’ orbit. The new object is named 2020 AV2.
Why report on an asteroid that has no chance of hitting Earth? Because this asteroid, known as 2006 QV89, has a history. A history of being kind of hard to track.
Whenever scientists announce an upcoming close encounter with an asteroid, certain corners of the internet light up like the synaptic rush that accompanies a meth binge, with panicky headlines shouted straight from the brain stem. But never mind that. We’re not that corner of the internet. We’re sober, yo!
It’s become something of an action movie cliche: an asteroid is hurling towards Earth, its impact will cause a mass extinction, and the only hope for humanity is a ragtag group of astronauts and average Joes who will fly to the asteroid and blow it to pieces using nukes. The idea has been explored so many times by Hollywood that it seems like this is actually something space agencies have planned.
And in truth, they are, though the execution may be a little more sophisticated. For decades, space agencies have considered various methods for destroying asteroids that threaten Earth. But according to a new study led by researchers from John Hopkins University, incoming asteroids may be harder to break apart than we thought.
The era of renewed space exploration has led to some rather ambitious proposals. While many have been on the books for decades, it has only been in recent years that some of these plans have become technologically feasible. A good example is asteroid mining, where robotic spacecraft would travel to Near-Earth Asteroids and the Main Asteroid Belt to harvest minerals and other resources.
At the moment, one of the main challenges is how these craft would be able to get around and refuel once they are in space. To address this, the New York-based company Honeybee Robotics has teemed up with the University of Central Florida (UFC) to develop a steam-powered robotic spacecraft. The company recently released a demonstration video that shows their prototype World is Not Enough (WINE) “steam hopper” in action.
Within Earth’s orbit, there are an estimated eighteen-thousands Near-Earth Asteroids (NEAs), objects whose orbit periodically takes them close to Earth. Because these asteroids sometimes make close flybys to Earth – and have collided with Earth in the past – they are naturally seen as a potential hazard. For this reason, scientists are dedicated to tracking NEAs, as well as studying their origin and evolution.
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.
Artist rendering of the LSST observatory (foreground) atop Cerro Pachón in Chile. Credit: Large Synoptic Survey Telescope Project Office.
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.”
Time-lapse photo of the sky above the LSST construction site in Chile. Credit: LSST
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.”
The HubbleSpace Telescope is the oldest space telescope in operation, having spent the past twenty-eight years in orbit. Nevertheless, this mission is still hard at work revealing things about our Solar System, neighboring exoplanets, and some of the farthest reaches of the Universe. And every so often, it also captures an image that happens to turn up something interesting and unexpected.
Recently, while conducting a study of Abell 370, a galaxy cluster located approximately four billion light-years away in the constellation Cetus (the Sea Monster), Hubble managed to spot something in foreground. While observing this collection of several hundred galaxiess, the image was photobombed by 22 asteroids whose tails created streaks that looked like background astronomical phenomena.
The study was part of the Frontier Fields program, where Hubble has captured images of some of the earliest galaxies in the Universe (aka. “relic galaxies”) in order to determine how it evolved over time. The position of this asteroid field is near the ecliptic (the plane of our Solar System) where most asteroids reside, which is why Hubble astronomers saw so many crossings.
Artist’s impression of a Near-Earth Asteroid passing by Earth. Credit: ESA
In the past, Hubble has recorded many instances of asteroid trails when conducting observations along a line-of-sight near the plane of our Solar System. In this case, the Near-Earth Asteroids (NEAs) – which orbit Earth at an average distance of about 260 million km (161.5 million mi) – were previously undetected due to their faintness. But thanks to the images taken by Hubble, scientists were able to identify them manually based on their motion.
Of the 22 asteroids, five were identified as unique objects. The image was assembled from several exposures taken in visible and infrared light, which was first released on November 6th, 2017. The image was prepared in honor of “Asteroid Day”, a global annual event that takes place every June 30th to raise awareness about asteroids and what can be done to protect Earth from a possible impact.
The day falls on the anniversary of the Tunguska event, which took place on June 30th, 1918, in eastern Russia and resulted in the flattening of 2,000 square km (770 square mi) of forest. While far less harmful than the Cretaceous–Paleogene (K–Pg) extinction event – which took place 66 million years ago and is believed to have killed the dinosaurs – Tunguska was the most harmful asteroid event in recorded history.
In many of the images snapped by Hubble, the asteroid tails appeared as white trails that look like curved streaks, an effect caused by parallax. In astronomy, parallax is an observational effect where the apparent position of an object appears to be different based on different lines of sight. Basically, as Hubble orbited around the Earth and took several images of the galaxy, the asteroids appeared to be moving relative to the background stars and galaxies.
The massive galaxy cluster Abell 370 as seen by Hubble Space Telescope in the final Frontier Fields observations. Credit: NASA/ESA/HFF
The asteroids own motion along their orbits and other contributing factors also led to their streaked appearance. Whereas the white streaks were identified as asteroid tails, the blue streaks are distorted images of distant galaxies behind the cluster. This effect is known as gravitational lensing, where light from distant objects is warped and magnified by the presence of an intervening object.
In this case, the intervening object who’s gravitational force magnified the light of the background galaxies was Abell 370. These more distant galaxies are too distant for Hubble to see directly, hence why astronomers use the technique to study the most distant objects in the Universe. But whereas the blue streaks were expected, the white streaks caused by asteroids took scientists completely by surprise!
This year, the European Space Agency (ESA) is co-hosting a live webcast with the European Southern Observatory (ESO) with expert interviews, news on some the most recent asteroid research, and a discussion about what killed the dinosaurs. You can watch this event tomorrow starting at 13:00 CEST (11:00 UST/04:00 PST) by going to the ESA’s Asteroid Day web page.
In February of 2015, the National Observatory of Athens and the European Space Agency launched theNear-Earth object Lunar Impacts and Optical TrAnsients (NELIOTA) project. Using the 1.2 meter telescope at the Kryoneri Observatory, the purpose of this project is to the determine the frequency and distribution of Near-Earth Objects (NEOs) by monitoring how often they impact the Moon.
Last week, on May 24th, 2017, the ESA announced that the project had begun to detect impacts, which were made possible thanks to the flashes of light detected on the lunar surface. Whereas other observatories that monitor the Moon’s surface are able to detect these impacts, NELIOTA is unique in that it is capable of not only spotting fainter flashes, but also measuring the temperatures of they create.
Projects like NELIOTA are important because the Earth and the Moon are constantly being bombarded by natural space debris – which ranges in size from dust and pebbles to larger objects. While larger objects are rare, they can cause considerable damage, like the 20-meter object that disintegrated above the Russian city of Chelyabinsk in February of 2013, causing extensive injuries and destruction of property.
The two main smoke trails left by the Russian meteorite as it passed over the city of Chelyabinsk. Credit: AP Photo/Chelyabinsk.ru
What’s more, whereas particulate matter rains down on Earth and the Moon quite regularly, the frequency of pebble-sized or meter-sized objects is not well known. These objects remain too small to be detected by telescopes directly, and cameras are rarely able to picture them before they break up in Earth’s atmosphere. Hence, scientists have been looking for other ways to determine just how frequent these potentially-threatening objects are.
One way is to observe the areas of the lunar surface that are not illuminated by the Sun, where the impact of a small object at high speed will cause a bright flash. These flashes are created by the object burning up on impact, and are bright enough to be seen from Earth. Assuming the objects have a density and velocity common to NEOs, the brightness of the impact can be used to determine the size and mass of the object.
As Detlef Koschny – the co-manager of the near-Earth object segment of the ESA’s Space Situational Awareness Program, and a scientist in the Science Support Office – said in an ESA press release:
“These observations are very relevant for our Space Situational Awareness program. In particular, in the size range we can observe here, the number of objects is not very well known. Performing these observations over a longer period of time will help us to better understand this number.“
Tiny pieces of rock striking the Moon’s surface were witnessed by the NELIOTA project, which was monitoring the dark side of the Moon. Credit: NELIOTA project
After being taken offline in 2016 for the sake of making upgrades, the NELIOTA project officially began conducting operations on March 8th, 2017. Using this refurbished telescope, which is operated by the National Observatory of Athens, NELIOTA is capable of detecting flashes that are much fainter than any current, small-aperture, lunar monitoring telescopes.
The telescope does this by observing the Moon’s night hemisphere whenever it is above the horizon and between phases. At these times – i.e. between a New Moon and the First Quarter, or between the Last Quarter and a New Moon – the surface is mostly dark and flashes are most visible. Incoming light is then split into two colors and the data is recorded by two advanced digital cameras that operate in different color ranges.
This data is then analyzed by automated software, which extrapolates temperatures based on the color data obtained by the cameras. As Alceste Bonanos – the Principal Investigator for NELIOTA – explained, all this sets the 1.2 meter telescope apart:
“Its large telescope aperture enables NELIOTA to detect fainter flashes than other lunar monitoring surveys and provides precise color information not currently available from other project. Our twin camera system allows us to confirm lunar impact events with a single telescope, something that has not been done before. Once data have been collected over the 22-month long operational period, we will be able to better constrain the number of NEOs (near-Earth objects) in the decimetre to metre size range.
Images showing the lunar impact flash caught by NELIOTA. Credit: NELIOTA project
The NELIOTA project scientists are currently collaborating with the Science Support Office of ESA to analyze the flashes and measure the temperatures of each flash. From this, they hope to be able to make accurate estimates of the mass and size of each impactor, which they will further corroborate by analyzing the size of the craters these impacts leave behind.
The study of impacts on the Moon will ultimately let scientists know exactly how often larger objects are raining down on Earth. Armed with this information, we will be able to make better predictions on when and how a potentially-threatening object could be entering our atmosphere. As the Chelyabinsk meteor demonstrated, one of the greatest dangers posed by meteorites is a general lack of preparedness. Where people can be forewarned, injury, damage and even deaths can be prevented.
NELIOTA is also contributing to public outreach and education through a number of initiatives. These include public tours of the Kryoneri Observatory – in which the details of the NELIOTA project are shared – as well as presentations to students and the general public about Near-Earth Asteroids. The project team are also training two PhD students in how to operate the Kryoneri telescope and conduct lunar observing, thus creating the next-generation of NEO observers.
This summer (Friday, June 30th), the Observatory will also be hosting a public event to coincide with Asteroid Day 2017. This international event will feature presentations, speeches and educational seminars hosted by astronomical institutions and organizations from all around the world. Save the date!
