Do we have a second interstellar visitor, following on the heels of the controversial ‘Oumuamua? If so, the new object is of a much different nature, as was its detection. In 2014, a meteor north of Manus Island, off the coast of Papua New Guinea produced a powerful blast that, upon analysis, implied a ∼ 0.45m meter object massing about 500 kg. Events like this, not uncommon in our skies, are cataloged by the Center for Near Earth Object Studies (CNEOS); this one shows up as being detected at 2014-01-08 17:05:34 UTC.
Image: This gorgeous wide-angle photo from the 1997 Perseid shower captures a 20-degree-long fireball meteor and another, fainter meteor trail in a rich area of the northern summer Milky Way. Showers like these are predictable, but could some solitary fireballs mark the end of a meteor with an interstellar origin? Credit & Copyright: Rick Scott & Joe Orman.
Now the CNEOS catalog, which covers the last three decades, is useful indeed, for it takes advantage of detectors maintained by the U.S. government to analyze the sound and light of the passage of objects through the atmosphere, producing information on velocity and position at the time of impact. Harvard’s Avi Loeb, a familiar face in the media thanks to the ‘Oumuamua discussion, worked with undergraduate student Amir Siraj, whom he set to calculating. What could we learn about the prior trajectory of meteors in the catalog, homing in on the fastest?
In a paper submitted to Astrophysical Journal Letters, Loeb and Siraj note the latter’s identification of the 2014 Manus Island meteor as interstellar in origin. The paper finds no substantial gravitational interactions between the meteor and any planet other than Earth. Indeed, based on the CNEOS-reported impact speed of 44.8 km s-1, Loeb and Siraj calculate a speed of 43.8 km s-1 outside the Solar System. For the object to be bound, the observed speed at impact would have to be off by more than 45%.
This meteor, then, was on an unbound hyperbolic orbit. We can go on from here to note the object’s relation to another useful metric. For measured relative to the Local Standard of Rest, this meteor entered the Solar System with a speed of 60 kilometers per second.
The Local Standard of Rest (LSR) is produced by averaging the motion of all stars in the Sun’s neighborhood. Siraj and Loeb speculate that this velocity could indicate ejection from a planetary system, specifically from the inner regions where orbital speeds are high. The object’s speed would imply a position inside the orbit of Mercury were it to come from a star like our own, but a red dwarf like Proxima Centauri would have an ejection speed from its habitable zone in this very regime. Recall that the habitable zone around Proxima Centauri is 20 times closer to the star than the HZ in our own system. So here’s an interesting thought: “Since dwarf stars are most common, the detection of this meteor offers new prospects for ‘interstellar panspermia,’ namely the transfer of life between planets that reside in the habitable zones of different stars.”
What I’m quoting from above is an as yet unpublished summation Loeb has recently written of the paper’s findings, one that goes on to speculate about its implications. Panspermia would require a larger object because it would have to survive the fiery passage through the atmosphere, but the notion that objects could be passed from star to star in this way is interesting (and note that Loeb is not identifying a Proxima Centauri origin for this meteor, but rather pointing to possible scenarios between stars). The point is that dwarf stars are the most common in the universe, and the detection of an interstellar meteor could point to what is perhaps a common form of transfer between stars.
Beyond that, consider the possibilities in studying interstellar materials when we may find them entering our own atmosphere. Says Loeb:
Using the Earth’s atmosphere as a detector for interstellar objects offers new prospects for inferring the composition of the gases they leave behind as they burn up in the atmosphere. In the future, Astronomers may establish an alert system that triggers follow-up spectroscopic observations to an impact by a meteor of possible interstellar origin. Alert systems already exist for gravitational wave sources, gamma-ray bursts, or fast radio bursts at the edge of the Universe. Even though interstellar meteors reflect the very local Universe, they constitute a “message in a bottle” with fascinating new information about nurseries which may be very different from the Solar System. Some of them might even represent defunct technological equipment from alien civilizations, which drifted towards Earth by chance, just like a plastic bottle swept ashore on the background of natural seashells.
Thus spectroscopy of gaseous debris burning up in the Earth’s atmosphere could offer us a way to make interstellar investigations of the kind we’ve been assuming would be decades (at least) off, assuming we can make a timely identification of likely targets.
The paper is Siraj & Loeb, “Discovery of a Meteor of Interstellar Origin,” submitted to Astrophysical Journal Letters (preprint).
Comments on this entry are closed.
A Faster Way to Form Planets
By Kerry Hensley on 12 April 2019
When interstellar asteroid ‘Oumuamua sped through our solar system in 2017, it revealed that small bodies might make a habit of visiting other planetary systems. Could such objects occasionally be responsible for jump-starting planet formation?
“A Hypothesis for the Rapid Formation of Planets,” S. Pfalzner & M. T. Bannister 2019 ApJL 874 L34. http://doi:10.3847/2041-8213/ab0fa0
Harvard professor discovers new way to hunt for alien spaceships
by Benyamin Cohen | Tuesday, April 16, 2019
Alien hunter Avi Loeb found what appears to be an interstellar object using a new detection method.
The best way to look for alien objects is to use the sun as a lamppost and to search for objects based on their reflective sunlight. This is how Oumuamua was found. But smaller objects, like that of a meteor, can use the Earth’s atmosphere as a detector. A few weeks ago, Loeb and Siraj were doing research on a meteor that had been spotted off the coast of Papua New Guinea. The fireball had an abnormally high velocity and seemed to originate from outside our solar system. If confirmed, the meteor will be only the second such object ever spotted by humans.
“Using the Earth’s atmosphere as a detector for interstellar objects offers new prospects for inferring the composition of the gases they leave behind as they burn up in the atmosphere,” Loeb explained. “In the future, astronomers may establish an alert system that triggers follow-up spectroscopic observations to an impact by a meteor of possible interstellar origin. … Some of them might even represent defunct technological equipment from alien civilizations, which drifted towards Earth by chance, just like a plastic bottle swept ashore on the background of natural seashells.”
Ever the explorer, Loeb believes we should continue scanning the sky. “Such a search would resemble my favorite activity with my daughters when we vacation on a beach – namely, examining shells swept ashore from the ocean. Not all shells are the same, and similarly only a fraction of the interstellar objects might be technological debris of alien civilizations. But we should examine anything that enters the solar system from interstellar space in order to infer the true nature of Oumuamua or other objects of its mysterious population.”
Wanting to learn more, we traveled to Loeb’s office on Harvard’s campus. We turned on a tape recorder and let him speak about Oumuamua and his search for alien life, which you can listen to here:
“Watch the skies. Everywhere. Keep looking. Keep watching the skies.” – The Thing from Another World.
As with any rare phenomenon, the more eyes looking out for them will increase the probability that they will be found. This is one of the reasons that we need vast numbers of cheap probes in the solar system. Whether to record transient phenomena, maintain observational series, or to find those hypothetical Bracewell probes or artifacts.
Using the Earth’s atmosphere as a net is certainly one approach, but it is the equivalent of looking on one small shoreline. We need to create a much larger net to be equivalent to all those beach walkers finding odd things washed up on beaches around the world.
Has anyone ever tried to estimate the rate at which our Solar System expels material into the ISM?
Could this high speed meteor have been a solar system object that was on its way to being ejected from the solar system when Earth got in its way?
No doubt some have worked on your first question Ronald, because it is related to the questions about how many rogue planets get ejected from the systems they form in. A simple assumption would be that the ejection rate would be high early in a system’s history but would fall over time as material thins out. But if a system experiences an upset (close passage of a nearby star, planet migration as per what caused the Late Heavy Bombardment here, etc.) there would be an uptick in the expulsion rate, less than but in proportion to the increased rate of impact during and after such events, I would assume.
As to your second question, that would be a double rarity. Possible, but very low odds.
An interesting little paper, funded by Breakthrough. My first thought was that local planetary slingshots could have achieved these speeds with no need to invoke an interstellar aspect. The authors’ calculations appear to rule this out.
The paper’s own extrapolation of local object density however given 1 Earth strike per decade results in a prevalence of 1 million such objects/au^3 or as the authors point out 6 billion trillion per star. Given those numbers,
any thoughts that…
“Some of them might even represent defunct technological equipment from alien civilizations, which drifted towards Earth by chance, just like a plastic bottle swept ashore on the background of natural seashells.” is at extreme odds with the authors own numbers. Even if a trillion technological relicts were ejected from EVERY star system each and every one of them would be drowned by a billion natural objects. The chances will likely be much lower. I like Avi Loeb, he likes to speculate. Even so, he didn’t risk including those remarks about defunct tech in his paper!^^
An object with a radius of 0.45 m weighing 500 kg would have a density of about 1300 kg/m3. That seems rather low for a meteorite.
Also, it is possible for an interstellar meteor to have a much lower impact velocity if it had previously interacted with the gravity of another planet (Jupiter comes to mind), we just wouldn’t be able to identify it as interstellar!
“This seems rather low for a meteorite.” Correct me if I am wrong, but I think that this is just the opposite! A stone boulder averaging one and a half feet in length, width, and breadth averages out at roughly 200-300 pounds. This object weighed roughly one half ton, indicating a mostly metalic composition.
Sigh. These are in g/cc to make Kg/m3 just multiply by 1000:
LL 3.21 (± 0.22)
L 3.35 (± 0.16)
H 3.40 (± 0.18)
EL 3.55 (± 0.1)
EH 3.72 (± 0.02)
CM 2.12 (± 0.26)
CO 2.95 (± 0.11)
CV 2.95 (± 0.26)
CK 3.47 (± 0.02)*
Aubrites 3.12 (± 0.15)
Diogenites 3.26 (± 0.17)
Eucrites 2.86 (± 0.07)
Howardites 3.02 (± 0.19)
Ureilites 3.05 (± 0.22)
Shergottites 3.10 (± 0.04)
Nakhlites 3.15 (± 0.07)
Mesosiderites 4.25 (± 0.02)
Pallasites 4.76 (± 0.10)
Iron meteorites are composed primarily of an Iron/Nickel blend which will often have a density of approximately 7g/cm3 – 8g/cm3.
I stand corrected. This obviously means that its density is ~1.3g?cm3. This raises an interesting question, however! The reason Siraj and Loeb believe that this object is denser than this is that it must have originated in a place too hot for comets to exist. 1.3g/cm3 would indicate that this, however; IS a comet fragment! This discrepancy may be resolvable in the existing data. It would take a rocky or metalic object signifigantly longer to burn up in Earth’s atmosphere than it would take an icy object to. If this event was observed COMPLETELY from start to finish, modeling should reveal which type it was IF INDEED it was a natural object. This is WILD SPECULATION, but if a conundrum arises due to irreconcilable data sets, an alternative NON-NATURAL explanation may arise. Don’t hold your breath, though.
How about objects that reach the surface of the Earth? If objects from other bodies in the solar system can be recognized and characterized, can the same be done for objects from outside the solar system? It may give new meaning to “leaving no stone unturned”.
The last three American Mars rovers, Spirit, Opportunity, and Curiosity, all found meteorites lying on the surface of the Red Planet:
That they happen to find them at their landing/roving sites by chance indicates there are a lot of meteorites all over Mars.
So far, no known meteorite has been confirmed to have an interstellar origin. The way they test for this is by looking for an elemental and/or isotopic signature that departs significantly from solar system norms. Radioactive decay rates are important here, allowing time of formation to be estimated. But if a particular meteor came from a system that was formed at about the same time as ours and that had a chemical makeup close to ours it would be extremely hard to discover the true origin.
I just wonder if the meteor or bolide was green, we seem to be having a recent influx of green ones… “Watch the skies.”
And where is this information coming from?
Check your news feeds, there has been at least 10 in the last 5 months.
And how do they compare to earlier numbers of green fireballs?
Jupiter must capture orders of magnitude more such objects (11 earth radii, 318 earth masses)
Could we use the giant as a massive detector for such events, if we had a network of satellites monitoring its atmosphere for interstellar bolides?
How many satellites would it take for round-the-clock coverage?
Jupiter is also the one that can capture these objects and turn them into short period objects. There may be a whole arsenal of derelict spacecraft in the same orbits as the short period Jupiter comet families!
Around 22,000. BoE using Planet Labs Earth observation satellites (180) x Jupiter’s greater area than Earth (121x).
Each cost 6 figures, say $0.5m, so total hardware costs is ~$10bn. Basically the cost of a major probe like Cassini. There would be a lot of launch costs, replacements, and monitoring overhead. Not cheap, but not that expensive either.
Would a large spacecraft, aircraft carrier size, that was left in space for millions or billions of years end up looking something like Asteroid Bennu? After all anything that large would have smaller objects gravitate towards it and eventual cover it up with a rubble pile.
NASA is working on a camera that could save humanity from extinction.
But they are getting impatient about launching an infrared space telescope called NEOCam.
Tiny fragment of a comet found inside a meteorite
by Arizona State University
April 15, 2019
A tiny piece of the building blocks from which comets formed has been discovered inside a primitive meteorite. The discovery by a Carnegie Institution of Science-led team, including a researcher now at Arizona State University, was published April 15 in Nature Astronomy.
The finding could offer clues to the formation, structure, and evolution of the solar system.
“The meteorite is named LaPaz Icefield 02342,” says research scientist Jemma Davidson of ASU’s Center for Meteorite Studies in the School of Earth and Space Exploration. “The name comes from where it was found in Antarctica’s LaPaz Icefield.”
She adds that it belongs to a class of primitive carbonaceous chondrite meteorites that have undergone minimal changes since they formed more than 4.5 billion years ago, likely beyond the orbit of Jupiter.
Full article here:
Giant Meteor Explodes Over East Coast.
The green fireball was seen by hundreds of people from Vermont to South Carolina.
By Avery Thompson Apr 18, 2019
What is interesting about the reports is that it was seen from Brazil! That is impossible since these meteors are burning up only 100 to 60 miles high and the curvature of the earth would put it below the horizon.
The east coast USA fireball was on April 17, 2019, 02:58 UTC and the Brazilian fireball was on April 12, 2019, 06:20 UTC. Seems someone was not paying much attention to the date/times on the videos and satellite data. But thats two green fireballs in 5 days! :-)
The Meteorite Flux of the Last 2 Million Years Recorded in the Atacama Desert
Press Release – Source: astro-ph.EP
Posted April 30, 2019 11:09 PM
The evolution of the meteorite flux to the Earth can be studied by determining the terrestrial ages of meteorite collected in hot deserts.
We have measured the terrestrial ages of 54 stony meteorites from the El Médano area, in the Atacama Desert, using the cosmogenic nuclide chlorine 36. With an average age of 710 ka, this collection is the oldest collection of non fossil meteorites at the Earth’s surface.
This allows both determining the average meteorite flux intensity over the last 2 Myr (222 meteorites larger than 10 g per km2 per Myr) and discussing its possible compositional variability over the Quaternary period. A change in the flux composition, with more abundant H chondrites, occurred between 0.5 and 1 Ma, possibly due to the direct delivery to Earth of a meteoroid swarm from the asteroid belt.
A. Drouard, J. Gattacceca, A. Hutzler, P. Rochette, R. Braucher, D. Bourlès, ASTER Team, M. Gounelle, A. Morbidelli, V. Debaille, M. Van Ginneken, M. Valenzuela, Y. Quesnel, R. Martinez
(Submitted on 29 Apr 2019)
Comments: accepted in Geology
Subjects: Earth and Planetary Astrophysics (astro-ph.EP)
Cite as: arXiv:1904.12644 [astro-ph.EP] (or arXiv:1904.12644v1 [astro-ph.EP] for this version)
From: Alexis Drouard
[v1] Mon, 29 Apr 2019 12:37:02 UTC (393 KB)