The universe is unbelievably enormous, so much so that we can't even see all of it as
much as we’d like to, and indeed, we don’t even know how big it is beyond what we can
see. But the universe, for all its hard rules and absolute physical laws, does allow for
some hacks that sometimes let us see things that we normally would not.
Few universal hacks are as mind blowing as the idea of gravitational lensing, where while
you might not be able to physically build a telescope to observe extraordinarily distant
objects within the observable universe, nature through gravitational lensing can sometimes
build one for you on a scale probably rbrn beyond even the most advanced civilizations
in the universe can do. So here are 10 mind blowing gravitational lensing events in space,
and indeed, this is a topic we’re going to hear about much more in the future, as
nature itself, in certain circumstances, provides the most powerful telescope possible.
Number 10. The First Detected Planet in Andromeda
The Andromeda Galaxy is currently just over 2.5 million light years from us. And it’s
getting closer, in the far future the milky way will collide with and merge with Andromeda.
But that won’t start for about another 4.5 billion years. Even at such astounding distances,
Andromeda is among the closest galaxies that allow for us to study individual stars within
it. But planets are a different story at that distance, only very special conditions such
as gravitational lensing can allow for situational discoveries of exoplanets.
But, it’s already happened, at least tentatively. The first candidate of an exoplanet within
the Andromeda galaxy is known as PA-99-N2, and through gravitational lensing shows that
the system is that of a star with a smaller companion. This companion would be an exoplanet,
but an enormous one at about 6.34 times the mass of Jupiter. This is significantly smaller
than Brown dwarf territory however, which would need to be about 75 times the mass of
Jupiter, so this planet would be a kind of super gas giant. So it seems within our grasp
to detect more gas giants at least within Andromeda. But while we may not be able to
detect earth-like terrestrial exoplanets, there may come a time when we will.
When the two galaxies collide in the far future, all of a sudden the exoplanets, billions of
them, from another galaxy entirely will become available. Here my science fiction author
imagination fires, think the collision wars, where the species of the two galaxies, and
perhaps some form of far future humans, confront to determine who controls the merged galaxies.
Or it could go the other way, and the species of the two galaxies greet each other, and
plan for the future of the resulting Milkdromeda galaxy and the eventual end of the universe
as we know it.
Number 9. PKS 1413+135
One of the many strange phenomena that the universe displays is the BL Lac type object,
a sub type of blazar. This is an active galactic nucleus with relativistic jets that display
really large variations in the brightness, setting them apart from other active galactic
nuclei such as quasars. One idea about these objects is that they represent relatively
low power elliptical radio galaxies, we just see their jets pointed right at us. The weird
thing about these types of galaxies is that they show apparent superluminal motion, or
material traveling faster than light, when it really isn’t and is just an effect of
material traveling at very near the speed of light seen from our vantage point.
But there is a type of gravitational lens that might help in the study of such objects,
at least at radio frequencies caused by the amplification of light coming from clumps
of plasma moving relativistically along the jets blasting away from the active galactic
nucleus’ central supermassive black hole. Researchers found this apparent effect with
an object known as PKS 1413+135, where the object has dramatically brightened on short
time periods several times in the last 20 years. Something with an enormous mass, 10,000
times that of the sun, is acting as an occasional gravitational lens, causing the amplification
of the light from the plasma at the black hole. There are candidates for what this could
be, but the most likely seems to be another foreground black hole causing the lensing,
perhaps even a primordial one from the early days of the universe floating in the intergalactic
medium.
Number 8. The Quasar and the Rogue Planet Cluster
Sometimes objects in the universe are not just strange for a single reason, but many.
The quasar RX J1131-1231 is one such example. Here we have a really bizarre quasar where
it’s being powered by a supermassive black hole, but a weird one. This black hole, located
about 6 billion light-years away is emitting X rays from its accretion disk in a way that
indicates this black hole must be rotating at half the speed of light, and must be being
fed astonishingly titanic amounts of dust and gas. But even the ability to study and
know that required gravitational lensing due to an elliptical galaxy and its gravity in
the foreground, in fact observationally this quasar appears as four images due to the effect.
But that’s not all that this instance of gravitational lensing has offered. What appears
to have been a very large population of unbound rogue planets were observed as a result of
the effect, apparently a high number of objects ranging in size from that of the moon to that
of Jupiter not bound to any star appeared to be present in this relatively distant quasar,
six billion year ago. An entire cloud of rogue planets, as it were.
Number 7. The Twin Quasar-Related Planet
In 1996 while we still weren’t sure exoplanets outside the solar system even existed, though
by that time everyone suspected they did and there were candidates, a very strange event
was seen that led to the first ever candidate for an extragalactic exoplanet even during
the very earliest attempts at observation of any exoplanets. The problem is, we can’t
ever confirm it as it was a transient one off event. The story goes that a quasar was
being observed, and a microlensing event just happened to occur that produced a twin image
of a quasar by way of a lensing galaxy, but a variation in the observation showed that
something else caused some additional lensing.
The best hypothesis is that a one time chance alignment happened where a roughly 3 earth
mass planet happened to move in the field of view and alter the normal profile of the
lensing by the foreground galaxy. Now, can’t ever prove this one, but if that was an exoplanet,
it was an amazing four billion light years away. And we saw it. And at 3 earth masses
that’s actually a really small planet to be able to see even if it were in our own
Galaxy, yet, the magic of microlensing allowed us to glimpse, just once, this very distant
world.
Number 6. The Einstein Rings
In 1912 Albert Einstein predicted that a gravitational body could bend light, essentially as a kind
of lens. This was a foreshock to the publication of General Relativity in 1916 that suggested
a phenomenon that could in principle be looked for, and in principle be tested by observation.
The effect was written about in 1924 by Orest Khvolson, who predicted a ring effect between
a source, the gravitational lens source and the observer in a very specific way. That
need for a near perfect alignment made Einstein skeptical that we would ever see such an effect,
indeed in 1936 he stated that there was no hope of ever observing this phenomenon directly.
Here, Einstein was proven wrong. Behold, an Einstein ring.
What you are seeing here is a foreground object gravitationally distorting the image, as we
see it, of a background galaxy. What should look something like this, is distorted gravitationally
to look like this. Where Einstein messed up was that he was thinking in terms of stars,
and the chance observation of something being gravitationally lensed by a star is low, though
you could do that artificially relatively straightforwardly with the right instrument
placement. But Einstein wasn’t thinking in terms of really huge or gravitationally
powerful things like entire galaxies or black holes. There the chances of lensing events
is much greater, and we have many examples of them, though the first complete observation
of one didn’t happen until the advent of the Hubble Space Telescope.
But about a star forming an Einstein ring with another star, while we haven’t actually
seen that in nature as far as I can find, we actually might in 2028 if the alignment
is absolutely perfect, which the chances of that being the case are about 45 percent from
what we currently know. Alpha Centauri A, from our perspective, will pass in front of
a distant red star and we might see Einstein’s predicted, but highly unlikely event just
116 years after the prediction. Perhaps they are not as rare as Einstein imagined.
Number 5. A Planet in the Galaxy M-51
The Galaxy M-51, also known as the whirlpool galaxy, from our perspective is one of the
most amazing and majestic we can see, even with relatively small telescopes. It’s interesting
in other respects, one of which is that it appears to be actively forming stars at a
high rate, which may be due to a close encounter with another galaxy known as NGC 5195 and
the interactions between the two are responsible for the burst of star formation, which has
been going on for hundreds of millions of years.
And it’s a galaxy we’ve known about for a long time. Whenever you hear a designation
of M, such as M-1, or M-51, or M-31 for Andromeda, that refers to a catalog of essentially fuzzy
objects observed through a telescope by French Astronomer Charles Messier in the latter half
of the 18th century, M-51 first being observed by him in 1773. Messier essentially scanned
the skies very carefully with his telescope looking for anything that wasn’t a star,
basically looking for smudges in the sky. And his work was so good, his catalog is still
used in astronomy today. But what Messier couldn’t have known is that there were planets
in the galaxies he was observing. Though I think had he known what we know now, he’d
have been absolutely amazed.
M-51 presents the object M51-ULS-1b, which was discovered in 2020. This is an odd one,
what’s going on here is that there is a high mass X-ray source, which is very likely
either a black hole or a neutron star, along with a big probably Type B supergiant star
in a binary system. Something seems to distantly orbit the X-ray source and eclipses it, and
the best candidate here is a big planet, but smaller than Saturn or perhaps comparable
to it. That’s pretty amazing really if you think about it, we may have a very special
situational observation of a somewhat small Saturn-like gas giant in a galaxy over 23
million light-years away. Pretty cool, I think Charles Messier would approve.
Number 4. Einstein’s Cross
This is the quasar Q2237+30 and it illustrates how situational gravitational lensing can
be. It’s juxtaposed behind the center of a galaxy known as Huchra’s Lens. This is
after scientist John Huchra and colleagues that found this object in 1985. They didn’t
see this image however, what they discovered with their instrumentation was that there
was redshift weirdness with this object. This was later found to be because the gravitational
lensing effect was in just such a juxtaposition to project four separate images of the quasar.
This particular example exhibits a red shift such that it must be about 8 billion light
years from earth, while the lensing galaxy must be about 400 million light years distant.
Since, several examples of this have been found, and represent a very unusual and situational
variation of gravitational lensing on top of the general overall effect. Here I think
it would be Einstein himself that might approve, or perhaps disapprove.
Number 3. SN 1987A
In 1987, I was already an amateur astronomer at about age 12. I had just seen Saturn through
a very small department store telescope my parents had bought me as part of a microscope
and small telescope set. And just when I learned what a supernova was, there was one happening
very brightly and visible to the naked eye that I couldn’t see because I was in the
northern Hemisphere. Thus I missed the supernova SN 1987A.
But the scientists did not, and this was the first supernova in modern times that was relatively
close that we could observe in depth. SN 1987A happened in the Large Magellanic cloud, which
is a dwarf companion of the Milky Way, with the supernova being about 168,000 light-years
from earth. We had seen supernovas before, the previous one had been Kepler’s supernova
in 1604 described by Johannes Kepler himself, and now we know of the supernova remnant from
it, but we hadn’t ever seen a close one from our perspective in modern science with
modern instruments until SN 1987A, and only within the last few years has evidence of
the resulting neutron star been found.
But in regards to microlensing, something weird happened with this supernova that has
never been resolved. When a supernova occurs, the first sign of it is a flux of neutrinos.
You see that before the actual flash of light due to the nature of neutrinos and supernovae.
In this case, there were four instruments studying neutrinos at the time. One specific
instrument, the smallest and least capable one, detected a neutrino flux from this supernova
four hours earlier than the others.
This led to the suggestion that a star might have just perfectly passed by that altered
and amplified the neutrino flux for that detector, and even that earth itself can enhance neutrino
intensity at different positions on its surface. Or maybe the supernova released multiple bursts
of neutrinos, and only one instrument was positioned right to detect the first burst.
Until we see more close supernovas, this is likely to remain an obscure, but open question
regarding supernovae.
Number 2. Icarus
In 2018 a star was discovered in the course of studying an extragalactic supernova with
the Hubble Space Telescope that didn’t seem quite right. A look at previous data showed
that this point like source had brightened significantly over the course of three years,
and the only explanation is that there was a star in that distant galaxy that was being
magnified by gravitational lensing by at least a factor of 2000 times. But in this case,
it had to be a two fold effect, in other words lensing from a galaxy cluster coupled with
microlensing from a smaller three solar mass object.
There was also a second peak noted in the data that may suggest that Icarus as it’s
known which is thought to be a blue supergiant star may have a companion in a binary star
configuration. What it didn’t look like was the usual objects that can be seen at
such great distance, in this case about 14 billion light years away, with the apparent
exceeding of the age of the universe due to its subsequent expansion.This compounded lensing
effect may have been due to a black hole or massive star within the overall galaxy cluster.
Studies of stars like this could yield clues about the earliest stars in the universe,
this one having emitted its light as we saw it when the universe was only about 30 percent
of its current age. Studies of this also might yield clues on whether primordial black holes
created near the birth of the universe could account for a significant fraction of dark
matter.
Number 1. Earendel
Earlier this year Icarus was superseded as the most distant seen individual star by a
very unusual lensed star known as Earendel, after an old English term for the morning
star but also a character from J. R. R. Tolkein’s Silmarillion. This star is by far the farthest
known star, coming in at 28 billion light-years away, again this great distance exceeds the
age of the universe because of its expansion since the big bang. In reality however ,the
light we see left the star about 12.9 billion years ago. Discovered with the Hubble Space
Telescope, this star was magnified about 1400 times by lensing created by the galaxy cluster
WHL0137-08.
This star is of great interest, because the light emitted from it from our perspective
was just 900 million years after the big bang, offering an insight on the very earliest stars
in the universe. One thing that can be said about this star is that it no longer exists.
What’s known is that it was extremely massive, about 50 to 100 solar masses, and would have
quickly went supernova, but it hasn’t yet done so from our vantage point, so think of
it as a kind of time ghost, where we’re looking so far back in time that we’re seeing
something that is no longer there if you could magically cross the immense distance to it.
In fact, there very well may be little evidence of this past star on location, and you have
to be at our distance to ever know it existed.
Further study of this star is one of the proposed projects for the James Webb Space Telescope,
because being an example of a very early star it could yield information on whether it’s
a single star at all, and if there were elements other than hydrogen and helium in its spectra,
giving clues to how early populations of stars in the universe began to supply the universe
with heavier elements, and it’s even possible that this star is so early that it contains
almost no elements other than the primordial hydrogen and helium of the big bang, or maybe
there will be surprises.
But one thing is clear, we are only at the very beginning of the study of gravitationally
lensed objects, but the study of such objects promises everything from more extragalactic
exoplanets, to insights on perhaps primordial black holes, dark matter, the earliest stars,
and literally represents the universe giving us a telescope of sorts that can see backwards
in time to the early universe. Expect much more from the study of gravitationally lensed
objects, and eventually the very largest human made telescopes of the future may use the
effect in relation to the earth or the sun to dramatically increase the power of our
observations of the cosmos. Thanks indeed, nature.
Thanks for listening! I am futurist and science fiction author John Michael Godier currently
musing about how we give special names like Icarus and Earendel to really far away stars,
but typically only unwieldy catalog numbers for interesting close ones. They need to unleash
me on naming astronomical objects. Picture it, the beautiful LeBaron Nebula, the McRib
elliptical galaxy, the sri racha supernova remnant and the mustard cluster. Won’t get
far, the IAU never likes my ideas and be sure to check out my books at your favorite online
book retailer and subscribe to my channels for regular, in-depth explorations into the
interesting, weird and unknown aspects of this amazing universe in which we live.