Even with six months' notice, we can't stop an incoming asteroid.
- At an international space conference, attendees took part in an exercise that imagined an asteroid crashing into Earth.
- With the object first spotted six months before impact, attendees concluded that there was insufficient time for a meaningful response.
- There are an estimated 25,000 near-Earth objects potentially threatening our planet.
The asteroid 2021 PDC was first spotted on April 19, 2021 by the Pan-STARRS project at the University of Hawaii. By May 2, astronomers were 100% certain it was going to strike Earth somewhere in Europe or northern Africa. On October 20, 2021, the asteroid plowed into Europe, taking countless lives.
There was absolutely nothing anyone could do to deflect it from its deadly course. Experts could only warn a panicking population to get out of the way as soon as possible, if it was possible.
The above scenario is the result of a recently concluded NASA thought experiment.
The question the agency sought to answer was this: If we discovered a potentially deadly asteroid destined to hit Earth in six months, was there anything we could do to prevent a horrifying catastrophe? The disturbing answer is "no," not with currently available technology.
While Europe can breathe easy for now, the simulation conducted by NASA/JPL's Center for Near Earth Object Studies and presented at the 7th IAA Planetary Defense Conference is troubling. Space agencies spot "near-Earth objects" (NEOs) all the time. Many are larger than 140 meters in size, which means they're potentially deadly.
Credit: ImageBank4U / Adobe Stock
"The level [at] which we're finding the 140-meter and larger asteroids remains pretty stable, at about 500 a year. Our projection of the number of these objects out there is about 25,000, and we've only found a little over one-third of those so far, maybe 38% or so," NASA's Planetary Defense Office Lindley Johnson tells Space.com.
With our current technology, spotting an NEO comes down to whether we just happen to have a telescope pointing in its direction. To remove humanity's blind spot, the Planetary Society — the same organization that deployed Earth's first light sails — is developing the NEO Surveyor spacecraft, which they plan to deploy in 2025. According to the Planetary Society, it will be able to detect 90 percent of NEOs of 140 meters or larger, a vast improvement.
How to move an asteroid
The DART spacecraft will attempt to deflect an asteroid.Credit: NASA
The NASA/JPL exercise made clear that six months is just not enough time with our current technology to prepare and launch a mission in time to nudge an NEO off its course. (Small course adjustments become significant over great distances, which is why "nudging" an asteroid is a potential strategy.)
What would such a mission look like? Hollywood aside — remember Armageddon?— we know of no good way to redirect an NEO headed our way. Experts believe that shooting laser beams at an incoming rock, exciting as it might look, is not a realistic possibility. Targeted nuclear blasts might work, but forget about landing Bruce Willis, Ben Affleck, and Liv Tyler on an asteroid to set off a course-altering bomb, especially just a month after its discovery (as was the case in the movie).
Another thing that might work is crashing a spacecraft into an NEO hard enough to shift its course. That's the idea behind NASA's Double Asteroid Redirection Test (DART). This mission will shoot a spacecraft at the (non-threatening) asteroid Dimorphos in the fall of 2022 in the hope of changing its trajectory.
The deadly asteroid's journey
The asteroid "2021 PDC" hit Europe in NASA's simulation.Credit: NASA/JPL
The harrowing "tabletop exercise," as NASA/JPL called it, took place across four days at the conference:
- Day 1, "April 19" — The asteroid named "2021 PDC" is discovered 35 million miles away. Scientists calculate it has a 1-in-20 chance of striking Earth.
- Day 2, "May 2" — Now certain that 2021 PDC will hit Earth, space mission designers attempt to dream up a response. They conclude that with less than six months to impact, there's not enough time to realistically mount a mission to disrupt the NEO's course.
- Day 3, "June 30" — Images from the world's four largest telescopes reveal the area in Europe that will be hit. Space-based infrared measurements narrow the object's size to between 35 and 700 meters. This would pack a similar punch as a 1.2-megaton nuclear bomb.
- Day 4, "October 14" — Six days before impact, the asteroid is just 6.3 million km from Earth. Finally, the Goldstone Solar System Radar has been able to assess the size of 2021 PDC. Scientists calculate the blast from the asteroid will be primarily confined to the border region between Germany, Czechia, Austria, Slovenia, and Croatia. Disaster response experts develop plans for addressing the human toll.
"Each time we participate in an exercise of this nature," says Johnson, "we learn more about who the key players are in a disaster event, and who needs to know what information, and when."
Practically speaking, little can be done to hurry technological development along other than budgeting more money toward that goal. Maybe we should have Bruce Willis on call, just in case.
The research suggests that roughly 1 percent of galaxy clusters look atypical and can be easily misidentified.
Their results, published in March, suggest that roughly 1 percent of galaxy clusters look atypical and can be easily misidentified as a single bright galaxy. As researchers launch new cluster-hunting telescopes, they must heed these findings or risk having an incomplete picture of the universe.
Galaxy clusters contain hundreds to thousands of galaxies bound together by gravity. They move through a hot soup of gas called the intracluster medium, which contains more mass than all the stars in all the galaxies within it. This hot gas fuels star formation as it cools and emits X-ray radiation that we can observe with space-based telescopes.
This bright gas cloud creates a fuzzy halo of X-rays around galaxy clusters, making them stand out from more discrete point sources of X-rays produced by, for example, a star or quasar. However, some galactic neighborhoods break this mold, as MIT Associate Professor Michael McDonald learned nine years ago.
In 2012, McDonald discovered a cluster unlike any other, which shone bright like a point source in the X-ray. Its central galaxy hosts a ravenous black hole that consumes matter and spews X-rays so bright as to drown out the diffuse radiation of the intracluster medium. In its core, the cluster forms stars at a rate roughly 500 times higher than most other clusters, giving it the blue glow of a young star population instead of the typical red hue of aging stars.
"We'd been looking for a system like this for decades," McDonald says of the Phoenix cluster. And yet, it had been observed and passed over years prior, assumed to be a single galaxy instead of a cluster. "It'd been in the archive for decades and no one saw it. They were looking past it because it didn't look right."
And so, McDonald wondered, what other unusual clusters might be lurking in the archive, waiting to be found? Thus, the Clusters Hiding in Plain Sight (CHiPS) survey was born.
Taweewat Somboonpanyakul, a graduate student in McDonald's lab, devoted his entire PhD to the CHiPS survey. He began by selecting potential cluster candidates from decades of X-ray observations. He used existing data from ground-based telescopes in Hawaii and New Mexico, and visited the Magellan telescopes in Chile to take new images of the remaining sources, hunting for neighboring galaxies that would reveal a cluster. In the most promising cases, he zoomed in with higher-resolution telescopes such as the space-based Chandra X-Ray Observatory and Hubble Space Telescope.
After six years, the CHiPS survey has now come to a close. Today in The Astrophysical Journal, Somboonpanyakul published the survey's cumulative results, which include the discovery of three new galaxy clusters. One of these clusters, CHIPS1911+4455, is similar to the rapidly-star-forming Phoenix cluster and was described in a paper in January in The Astrophysical Journal Letters. It's an exciting finding since astronomers know of just a few other Phoenix-like clusters. This cluster invites further study, however, as it has a twisted shape with two extended arms, whereas all other rapidly-cooling clusters are circular. The researchers believe it may have collided with a smaller galaxy cluster. "It's super unique compared to all the galaxy clusters that we now know," says Somboonpanyakul.
In all, the CHiPS survey revealed that older X-ray surveys missed roughly 1 percent of galactic neighborhoods because they look different than the typical cluster. This can have significant implications, since astronomers study galaxy clusters to learn about how the universe expands and evolves. "We need to find all the clusters to get those things right," McDonald explains. "Ninety-nine percent completion isn't enough if you want to push the frontier."
As scientists discover and study more of these unusual galaxy clusters, they may better understand how they fit into the broader cosmic picture. At this point, they don't know whether a small number of clusters are always in this strange, Phoenix-like state, or if this is perhaps a typical phase that all clusters undergo for a short period of time — roughly 20 million years, a fleeting moment by spacetime standards. It's difficult for astronomers to tell the difference, as they only get a single snapshot of each cluster nearly frozen in time. But with more data, they can make better models of the physics governing these galactic neighborhoods.
The conclusion of the CHiPS survey coincides with the launch of a new X-ray telescope, eROSITA, which aims to grow our catalogue of clusters from a few hundred to tens of thousands. But unless they change the way they look for those clusters, they will miss hundreds that deviate from the norm. "The people that are building out the cluster searches for this new X-ray telescope need to be aware of this work," says McDonald. "If you miss 1 percent of the clusters, there's a fundamental limit to how well you can understand the universe."
This research was supported, in part, by the Kavli Research Investment Fund at MIT, and by NASA through the Guest Observer programs for the Chandra X-ray Observatory and Hubble Space Telescope.
Not only does this give us a look at the scaffolding of the universe, we found some new galaxies too!
- An international team of scientists has taken the first image of the web like structure that shapes the cosmos.
- The images are the first direct look at the largest known objects in the universe.
- The images also suggest far more dwarf galaxies exist than previously thought, provoking questions about how they form.
You might not have heard of them if you aren't an astronomer, but the largest known objects in the universe aren't galaxies or the super-clusters they form together. They're actually ghostly webs of dark matter that form the boundary between the voids of deep space and the clusters of galaxies where stars shine, planets form, and most of the astronomical phenomena you know reside.
This filament, which spreads throughout the cosmos forming a foam-like structure, attracts dust along its main stretches while galaxies seem to cluster at its nodes. Despite the massive size of these filaments—a typical length would be in the 200-500 million light-year range—it isn't easy to actually see these things directly.
This is why a new study, published in Astronomy and Astrophysics, is so exciting. It provides the first direct look at the cosmic spider web holding the universe together and reveals hidden galaxies to astronomy.
The universe is held together by cosmic spider webs?
"The image shows the light emitted by hydrogen atoms in the cosmic web in a region roughly 15 million light years across. In addition to the very weak emission from intergalactic gas, a number of point sources can be seen: these are galaxies in the process of forming their first stars."
© Jeremy Blaizot / projet SPHINX
Lots of things in space are hard to look at directly, but it is possible to observe their effects on things near them. Ever since the filament was first noticed in the 1980s, astronomers have been looking at the effect it has on light, such as how it can refract the light from objects behind it when it sits between that object and Earth, and how it interacts with extremely bright quasars. While this provided some data, it left much to be desired.
Luckily, science marches forward, and it was probably inevitable that somebody would figure out how to get a better look at the stuff.
Using the aptly named Very Large Telescope in Chile and a device called the Multi-Unit Spectroscopic Explorer, an international team of researchers aimed at Hubble Ultra-Deep Field. This region, known for being where some of the most revealing images of the cosmos are taken from, was observed for 155 hours, 140 of which produced useful images. After a year of processing, the team produced these images:
The blue is the hydrogen collecting near the filament. The background is the Hubble Ultra-Deep Field Image.
Credit: Roland Bacon/David Mary/ESO/NAS
The long exposure time allows for the dim light from hydrogen emissions to be collected and formed into an image.
The images you see also include a large number of galaxies that previously escaped detection. A follow-up analysis of the data also suggested that the hydrogen detected by the spectroscopic explorer could be accounted for by assuming the presence of a large number of previously unknown dwarf galaxies. While these galaxies are currently too small to see individually, follow-up studies will know where to start looking for them.
As lead author Roland Bacon explained to CNN:
"We cannot see these galaxies, because they are intrinsically faint and too far: we are observing them 2 billion years after the Big Bang -- at a distance of 11 billion light-years. But there are so many that we can see the integrated light produced by them."
While fascinating in its own right, this discovery will lay the foundations for further study of the filament and may lead to a new understanding of dwarf galaxy formation.
The newly discovered galaxies are 62 times bigger than the Milky Way.
- Two recently discovered radio galaxies are among the largest objects in the cosmos.
- The discovery implies that radio galaxies are more common than previously thought.
- The discovery was made while creating a radio map of the sky with a small part of a new radio array.
An extremely active galaxy
Radio galaxies are galaxies with extremely active central regions, known as nuclei, which shine incredibly brightly in some part of the electromagnetic spectrum. They are known for emitting large jets of ionized matter into intergalactic space at speeds approaching that of light. They are related to quasars and blazars. It is thought that supermassive black holes are the energy source that make these galaxies shine so brightly.
What makes these two galaxies (known as MGTC J095959.63+024608.6 and MGTC J100016.84+015133.0) so interesting is their size. Only 831 similar, "giant radio galaxies" are known to exist. As study co-author Dr. Matthew Prescott explains, these are particularly large even for giants:
"These two galaxies are special because they are amongst the largest giants known, and in the top 10 percent of all giant radio galaxies. They are more than two mega-parsecs across, which is around 6.5 million light-years or about 62 times the size of the Milky Way. Yet they are fainter than others of the same size."
The smaller of the two is just over two megaparsecs across, roughly six and a half million light-years. The larger is almost another half megaparsec larger than that.
Exactly how these things get to be so massive remains a mystery. Some have proposed that they are ejecting matter into unusually empty space, allowing for the jet to expand further, though some evidence contradicts this. The most commonly suggested idea is that they are simply much, much older than the previously observed radio galaxies, allowing more time for expansion to occur.
How does this change our understanding of the universe?
While exciting and impressive on their own, the findings also suggest that there are very many more of these giant galaxies than previously supposed. If you were going off the previous estimates for how typical these galaxies are, then the odds of finding these two would be 1 in 2.7×106. This suggests that there must be more, given that the alternative is that the scientists were impossibly lucky.
In the study, the researchers also apply this reasoning to smaller versions of these galaxies, saying:
"While our analysis has considered only enormous (>2 Mpc) objects, if radio galaxies must grow to reach this size, then we may expect to similarly uncover in our data previously undetected GRGs with smaller sizes."
Exactly how common radio galaxies and turn out to be remains to be seen. Still, it will undoubtedly be an exciting time for radio astronomy as new telescopes are turned skywards to search for them.
How did they find them?
The new galaxies were discovered by the amusingly named MeerKAT radio telescope in South Africa during the creation of a new radio map of the sky. The MeerKAT is the first of what will soon be the Square Kilometre Array of telescopes, which will span several countries in the southern hemisphere and make even more impressive discoveries in radio astronomy possible.
Planets can emit radio waves. For the first time, we've picked them up from outside the solar system.
- An international team of scientists have picked up the first radio waves emitted by an exoplanet.
- The planet is a "Hot Jupiter" orbiting a star system 40 light years from Earth.
- The findings must be confirmed, but if they are, it will be a first in radio astronomy.
When people think about radio waves from space, the first thought is probably about aliens. However, lots of things can produce radio waves, pulsars are famous for doing so, and the entire field of radio astronomy is dedicated to looking at objects with equipment that sees what we cannot.
This provides the possibility of using radio telescopes to gather information that could never be acquired with visible light. An international team of researchers has done just that. They have identified the first-ever radio emission from a planet in another solar system and have used it to gather information about the planet.
It's not little green men, but it's a start.
Science has known for a while that planets emit radio emissions. Jupiter does it all the time due to the interaction of various kinds of radiation with its magnetic field. Previous studies achieved a fair understanding of what these emissions look like.
In this study, the authors used an estimate of what Jupiter's emissions would look like if they were much further away to determine if the radio emissions coming from the Tau Boötis system matched what would be expected if the system had a gas giant of its own closely orbiting its sun, commonly known as a "Hot Jupiter." The existence of a planet in that system has been known for some time.
The study utilized a top of the line, decentralized radio telescope network to collect these findings. The Low-Frequency Array (LOFAR) is centered in the Netherlands and operated by the Netherlands Institute for Radio Astronomy. While the network includes telescopes all over Europe, this study only used the core group of telescopes.
After reviewing the massive collection of radio images, the subtle signs of a gas giant orbiting another star began to appear. Lead author Dr. Jake D. Turner, a postdoctoral researcher at Cornell University, explained the findings:
"We present one of the first hints of detecting an exoplanet in the radio realm. The signal is from the Tau Boötes system, which contains a binary star and an exoplanet. We make the case for an emission by the planet itself. From the strength and polarization of the radio signal and the planet's magnetic field, it is compatible with theoretical predictions."
While the idea of looking for exoplanets with radio telescopes isn't new, this is the first time that researchers have picked up signals from an exoplanet. This is no small feat, and several other astronomers have expressed their excitement.
"If confirmed through follow-up observations this radio detection opens up a new window on exoplanets, giving us a novel way to examine alien worlds that are tens of light-years away."
The study involved more than 100 hours of searching for radio signals in star systems up to 100 light-years away. The expected signals were only seen in Tau Boötes. The detected signal is relatively weak, and it remains possible that it wasn't from the exoplanet. Further research will focus on confirming the findings.
Dr. Turner also expressed his desire to continue searching for other exoplanets using a larger proportion of the telescopes in the LOFAR.