This year astronomers released the first ever groundbreaking image of a black hole. Captured within this simplistic yet impactful image is confirmation of one of the biggest and most complicated astronomical mysteries in human history. Albert Einstein produced equations to suggest that they existed and there were lines of evidence, but this is the first direct proof the first ever magnificent image and what a breakthrough it is. This black hole is a monster and one of the largest known that exists in the known universe in the past we have managed to capture bright glowing quasars and star dense galactic cores, but what sets this image apart is that not only can we see the accretion disk also known as the so-called glowing ring of fire around the edge, but we can also see this in front of the event horizon, the dark and up until now the theoretical chamber of a black hole. Beyond this barrier the gravity is so strong that nothing in the Universe can escape from it not even light hence the empty void like object we see in this image. This is the first time capturing an event horizon and this strengthens our knowledge of black holes.
Before we were unable to conclude on these massive gravity centers, not just being incredibly dense or compact neutron stars or some sort of similar object with a huge gravitational field. We only had infrared images of stars at the center of our galaxy orbiting something with an enormous gravitational pull, but because the black hole is just that, black, we couldn't actually see what was lurking in the dark independently from the black backdrop of space. Even Einstein himself was unsure whether his mathematical equations could actually correspond to such a near physics-defying object, but we now know this to be the case and black holes are indeed very real. This reassures a lot of our predictive models of astrophysics and adds visual evidence to decades of mathematical calculation and refinement. The black hole is confirmed and we can now start to speculate on some much deeper mysteries of cosmology all thanks to this one beautiful image.
So, about the black hole itself, what are we actually looking at in this image? this black hole is in the center of the super-giant elliptical galaxy Messier 87 also known as ‘Virgo A’ or ‘M87’ located over 50 million light-years away in the constellation of Virgo, hence its alternative name. A Messier object is the catalogue of 110 astronomical objects, first recorded by French astronomer Charles Messier in his catalogue of nebulae and star clusters. He was originally trying to locate comets, before identifying these objects and collaborating them into a list of non-comet objects that would help form the basis for the classification of many of our neighboring galaxies and nebulae. Initially all the Messier objects were thought to be located within our Milky Way galaxy, before Messier 31, aka the Andromeda galaxy was identified as an extra galactic object.
Virgo A is a 53 million light-years distant object and the galaxy itself is absolutely enormous. Its radius extends just under 500,000 light-years, meaning its total diameter verges on a mind-bending 1 million light-years across. This is just one of thousands of supergiant elliptical galaxies that we know of. To put that in some kind of perspective, it was recently discovered that our Milky Way galaxy is probably quite a lot larger than we initially thought. Our estimates used to sit at between 100 to 130 thousand light years across, but it is now more likely to be between 150 to 200 thousand light years, putting it nearly on par with our nearest spiral galaxy the Andromeda galaxy. Even at the upper bound of this estimate, M87 is at least 5 times larger than our home galaxy. Supermassive black holes lie at the center of galaxies and play significant role in binding them together at the central bulge. M87’s black hole is one of the most massive ever recorded, it measures 40 billion kilometers across and has a mass of over 6.5 billion solar masses so that's 6.5 billion times heavier than our own Sun.
The largest black hole ever noted TON 618, which is a very distant and radio-loud quasar estimated to weigh in at just over 10 times that mass, but make no mistake 10% of the mass of the largest black hole ever discovered is still an absolute giant of the cosmos.
What you can see in this picture is almost as large as our entire solar system, this made it large enough to be photographed, leading to this breakthrough. This black hole is an enormous size but it still sits at over 50 million light years away. So how did we manage to photograph such a distant object right here on Earth?
Photographing a black hole began with Professor Heino Falcke of Radboud University in the Netherlands. As a young PhD student in 1993 he had the idea for an initiative to capture a photograph of a black hole. Driven by the determination to see one for himself however at the time nobody thought this could be possible the idea of taking a picture of a black hole over the black backdrop of space was dismissed. That being said Falcke argued that black holes generated a certain type of radio emission which could be detectable from Earth. He also proposed that due to the gravitational field of black holes and their subsequent effect on traveling light black holes may appear around two-and-a-half times larger than they actually are when observed. These two factors in his view made the prospect a possibility. It would take years, millions of dollars and the overcoming of several scientific obstacles along the way, but they had a shot. Eventually after 20 years of arguing his case Falcke managed to persuade several astronomical bodies, mainly the European Research Council and the National Science Foundation to fund the project. Before long, space agencies in East Asia contributed funding giving the project $50 million. So that was one problem solved, but several more still lay ahead. In order to capture a black hole, you would need a radio telescope. Radio telescopes are used because of the aforementioned nature of the black hole, you can't capture a lightless object against the black backdrop of space with just visible light, but the radiation being emitted from the black hole on its accretion disk could hypothetically be illuminated when viewed with a radio telescope to act as a luminous backdrop. This allows us to photograph not only what we've already seen the ring of fire that is the glowing accretion disk, but also the event horizon itself, the dark barrier beyond which light can no longer escape. Capturing both would be an essential requirement improving the existence of black holes as we understand them. The only problem is that every supermassive black hole that we know of is unimaginably distant and to photograph them would require a telescope at least the size of Earth and obviously we can't just construct a radio satellite dish that size. but humans are clever and creative and we soon found a way around that too. Professor Shepard Doelemen of the Harvard-Smithsonian Center for Astrophysics formed an initiative to create a network of eight interlinked radio telescopes. If these were placed at strategic points around the Earth, each one's readings could be merged together to form a bigger picture taken as if the entire Earth were one big radio telescope. This laid the foundations for the Event Horizon Telescope.
The Event Horizon Telescope (EHT) is a global array of eight radio telescopes working in sync as one larger Earth sized telescope, so to give enough reach and space to photograph this monster black hole. The process of using multiple radio telescopes to build a larger overall picture of something is known as interferometry and interferometers such as The Very Large Array are common on Earth. The EHT project was slightly more ambitious given the distance between each individual point, but nevertheless it did its job. In the future it is hoped that the EHT will be expanded to twelve radio telescopes which will allow for even clearer and more accurate observations of distant intergalactic objects. Using this vast interferometer, a team of 200 scientists and mathematicians pointed the network of telescopes towards M87 and stare at its heart over a period of 10 days in 2017 and took continuous pictures of readings as time passed. Slowly piecing together this mystifying cosmic jigsaw. Due to the size and scale of the project they recorded more scientific data than has ever been recorded by any scientific experiment and so took a lot longer to process than was first anticipated. The data recorded was so great that it was unable to be transmitted over the Internet and so was stored on large hard drives and sent to processing centers in Boston in the USA and Bern in Germany. Obviously eight telescopes no matter how well placed wouldn't be able to compare to an actual earth sized telescope and so the virtual network failed to capture the entirety of the image, but with enough pieces computer algorithms can complete the data and fill in the blanks, sort of like a galactic Sudoku solver. The problem is the sheer amount of extracting data in the radio background noise. MIT PhD student Katie Bouman developed an algorithm that could sift through the data and piece together the image. It took over two years and was released later than expected, but has finally happened. Katie herself has become an overnight celebrity for the leaps and bounds she has made in female achievement in both astronomy and computer science.
And here it is, over two years of processing, 200 scientists, eight radio telescopes, terabytes and terabytes of information over $50 million in funding they have all been pieced together to take a photo of an object over 311 sextillion miles away. Everything has fallen into place, this image is the result of all of those cascading factors, this is one of the greatest astronomical breakthroughs of all time and is one of the most important photographs ever taken.
So, what now? Well if you feel the Event Horizon team was stopping here, you'd be wrong. They will now turn their attention to their initial main target, the supermassive black hole at the center of our own galaxy Sagittarius A*. This sounds easier given its proximity, but unfortunately the accretion disk here is much smaller and less luminous for our local black hole and will require more refined techniques of observation.
In the meantime, though, we can have some fun in speculating on some dark more fantastical mysteries of black holes. For example, everything in the Universe is supposedly describable by information, which defines all the energy and matter within the Universe. Initially Einstein's theory suggested that anything sucked into a black hole may be destroyed and would disappear from the universal together in violation of all of the laws of physics. However, the late Stephen Hawking challenged this and supposes that information never actually reaches a point beyond the black hole singularity and is instead stored behind the event horizon in a sort of flat crushed up hologram. This phenomenon is known as super-translation. While this does mean that the information isn't lost from the Universe, it is still all but destroyed on the journey into the black hole due to its gravitational pull. In a process known somewhat trivially as spaghettification, which becomes so destructive that it separates an object atom by atom and only survives in its simplest most basic and useless form. For all intents and purposes, this circumvents the needs for an inside or a supposed exit from a black hole and answers a problem known as the information paradox.
Now we know that black holes exist as we theorize them, we can start having these conversations regarding what lies beyond or inside them. Alternatively, to Hawking's ideas some believe that a spinning black hole could create a wormhole, an exit point beyond the black hole's event horizon that bends space and time to connect two distant parts of space together, bypassing the distance between them. In fact, some even believe that a black hole could result in a wormhole connecting our Universe to another universe with exit gates into new dimensions known as white holes. Of course, this is all also hypothetical, but again is something we can begin to get excited about the prospect of, now that we know that the gateway into the dark exists. Parallel universes and faster than light travel aside, we've finally achieved confirmation of one of astronomy's two great contemporary mysteries being the existence of black holes the second mystery is the existence and nature of dark matter. With our knowledge of the cosmos strengthened by this picture, we could move towards discovering the nature of dark matter. That is, its existence and its effects on gravity in galaxies and galaxy clusters formations. Ultimately, we still have a lot more to learn and while this image is a giant leap in the right direction, the space beyond the image could hold the answer to more of the mysteries of the Universe. Our knowledge is ever-changing and there will always be more work to be done but with this photograph, we can go forward that little bit more certain about our ideas and models of cosmology and though there is still some way to go this image is still an achievement on the magnificent scale of the black hole itself.
When a massive star comes to the end of its life, it doesn’t go out with a whimper, rather it explodes in majestic fashion in what we call a supernova. This is one of the most energetic events that we know of. At its peak brightness, a powerful supernova can be as luminous as an entire galaxy. This luminosity doesn’t last long, as the energy is expended in a short space of time, perhaps lasting only a couple of days at most. On an astronomical timescale, that is just a heartbeat. So how often do supernovae occur? There’s certainly never been one mentioned in the media recently, right? Well, there’s a supernova somewhere in the observable universe every second or so. As you can see, supernovae are pretty common, but they aren’t all that easy to spot. For one, they have to occur somewhere in the observable universe, and be close enough that we can see them and notice them. But, in just the astronomically short space of time that humans have been able to observe other galaxies, we have seen tens of supernova directly.
This image of galaxy NGC 4526, captured by Hubble in 1994, shows a supernova on the outskirts, during its peak brightness. Astonishingly, it is so bright, in this image it appears to be a star in our own galaxy. But being in another galaxy means even though it was this bright, only strong telescopes were able to observe it.
But what about naked-eye supernova events, how often do they occur, and what would they look like? Well it depends on the distance to us. The most recent naked-eye supernova event was SN 1987A, a supernova that occurred in the Large Magellanic Cloud in 1987. This is the only supernova that’s been observed up close in our local group of galaxies, as the Large Magellanic Cloud is a satellite galaxy to our own Milky Way at only 160,000 light years away. At this supernova’s peak brightness, it reached an apparent magnitude of 3, meaning that although it was visible to the naked-eye, it would have only appeared like another star in the night sky. However, this event was of particular interest to scientists as they had had the Large Magellanic Cloud mapped out, meaning they could pinpoint the exact star that exploded, and view the before and after shots. And the after shots are spectacular.
This is the remnants of the star. The ring around it is stellar material ejected by the star 20,000 years before the explosion, and as the shockwave from the supernova expands you can see it impact the ring, lighting it up through ionisation. But with an apparent magnitude of 3, it’s not super impressive for those of us wanting to look up and see something fantastic in the night sky. The previous naked-eye supernova occurred in 1604, known as Kepler’s supernova.
Occurring only 20,000 light years away, it had an apparent magnitude of -2.5, much brighter than any other star in the night sky and even visible during the day. This brightness lasted a couple of weeks. We can now observe the remnants of this supernova using modern day telescopes. But perhaps the brightest supernova in recorded history was in 1006, with an apparent magnitude of -7.5, meaning it was 16 times brighter than Venus, clearly visible during the day.
Thanks to historical records of early astronomers, we can pinpoint this supernova’s remnant too. But even SN 1006, the brightest supernova on record, was still 7,000 light years away. Are there any stars even closer than that that might erupt in a supernova soon? And if so, what would that be like? As it happens, there are 12 stars that are approaching the end of their lives that would erupt in a supernova less than 3,000 light years away from us.
One of them, one of the most famous stars in our night sky, is Betelgeuse. Found in the Orion constellation on Orion’s shoulder, this star is distinctively reddish in colour. This is because it is a red supergiant, which is really near the end of its life. We don’t know for sure when any supernova will occur, as we haven’t observed any close enough to look out for tell-tale signs, but it is expected that Betelgeuse could go any moment really, although it could also still take tens of thousands of years. It is only a few hundred light years away from us, and it is estimated that it would appear brighter than a full moon when it finally erupts in a supernova. But don’t fret, even at this distance, it is expected that no real harm would come to life on Earth.
A supernova would have to occur within 50 light years of us for any harm to befall us, and we just don’t see any eligible candidates for that right now. Although, it should be noted that a certain type of supernovae can also occur with white dwarves.
If a lot of mass gets fed into these tiny, dense stars by other nearby stars, this could trigger a supernova. Because of their tiny and dim nature, we don’t have a good understanding of how many there are out there. It is thought that there could be a few hundred of them within 50 light years from us that we don’t know about. We do seem to be overdue for a supernova somewhere in our galaxy though. Supernovae are believed to occur every 50 years on average in the Milky Way, yet we haven’t seen one with modern telescopes yet. And you can be sure that when it does finally happen, that everything about it will be observed for years to come.
When thinking about where life could exist elsewhere in our own Solar neighborhood the debate is often centered around the oceans of Europa, oceans of Titan, the surface of Mars and the clouds of Venus, but a relatively not discussed body in our Solar System could actually hold a genuine possibility that life exists or may have existed at one point within it. It's not what you might expect, however when we think of life, we think of large planets, plentiful oceans, well as it turns out this body may just prove that life is a bit more prevalent and resistant than that it is. Ceres is a dwarf planet and an asteroid, the largest celestial body located within the main asteroid belt located between the orbits of Mars and Jupiter. Comprised of mostly rock and ice this little planet has recently been found to have key ingredients for organic life to emerge.
The name Ceres originates from the Roman goddess of Agriculture, with that said, you shouldn’t imagine forests, crops, and nature is a little bit of an exaggeration for this celestial body, but Ceres is certainly diverse, unique and very interesting. So let's dive into its frozen oceans as we search for life on the dwarf planet located at just less than 2.8 astronomical units, one astronomical unit – AU being the distance between Earth from the Sun. From our local star, Ceres is located within the asteroid belt. Ceres is essentially the largest of the large asteroids within the belt, hence why it tows the line between asteroid and planet.
It was first discovered in 1801 by astronomer Giuseppe Piazzi at the astronomical observatory of Palermo. In the years leading up to this it was theorized that a planet like Ceres would exist between Mars and Jupiter as part of the now disproven Titius-Bode law. The law stated that each planet moving further away from the Sun would have to orbit at twice the distance of the previous one, meaning the various planetary orbits in the Solar System were increasing in radius exponentially. A discredited theory now, but it led astronomer Johannes Kepler to notice the gap between Mars and Jupiter and he theorized something undiscovered may lie there. This lucky coincidence led Hungarian astronomer Franz Xaver von Zak to assemble a team of 24 astronomers nicknamed the Celestial Police to search the area for a planetary body in 1800 the team found several large asteroids that we now know to be in the asteroid belt. But it was Giuseppe Piazzi an Italian astronomer who discovered the dwarf planet of Ceres by accident. He had been searching for star-like objects when he observed Ceres for the first time and although he initially thought he'd found some sort of comet, further observations eventually ended up with him labeling his discovery as a planet and being invited to join the Celestial Police before illness meant he could no longer observe the skies. Estimates of this celestial body didn't really get much within the correct bounds some theorized it to be as small as 200 kilometers in diameter whereas others placed it around Pluto size at 2,500 kilometers wide.
We now know Ceres’ size to be about 945 kilometers in diameter meaning that Ceres is a comparative size to the top to bottom length of the United Kingdom. It takes 1681 days to orbit the Sun, just over four and a half Earth years. Ceres origin is still up for debate, we predict it to be roughly four and a half billion years old and we theorize it might be a surviving protoplanet also known as a planetary embryo. It’s an asteroid like body that rams into other asteroids to form terrestrial planets. Most of the inner Solar System protoplanets are believed to have been either merged into planets or ejected from the solar system altogether by Jupiter's orbit and gravity. Ceres seems to have survived these eventualities relatively unscathed. Other theories however state that Ceres was actually formed within the Kuiper belt before migrating nearer the Sun via various large gravitational influences this theory holds way given the presence of ammonia salts detected in Ceres’ Occator crater and also Ceres believed formation under colder conditions than most planets and asteroids lends credibility to this theory, meaning that the dwarf planet was formed beyond Jupiter's orbit. For its competition Ceres was originally considered a planet for about 50 years before being reclassified by early astronomers in the mid-1850s after the discovery of other asteroids in its neighborhood. It’s now considered a dwarf planet, minor planet or large asteroid. It was actually Ceres and its neighbors that were crucial in the discovery of the asteroid belt. Most of these asteroid rocks were originally thought to be like stars, but following the discoveries of these asteroids, astronomers realized they fell under a new classification. One year after Ceres discovery in 1802 with the discovery of the second large asteroid Pallas, William Herschel designated the term asteroid which literally means star-like. Under the more recent minor planet designation system, Ceres full name is actually ‘1 Ceres’ followed by ‘2 Pallas’, ‘3 Juno’ and ‘4 Vesta’, numbered in the order of their discovery. In 2006 Pluto who is reclassified as a dwarf planet thanks to the discovery of Eris, another dwarf planet a year earlier. This put Ceres up for debate - being a lot smaller. On the 24th of August 2006 a planetary definition was adopted that stated that a planet had to dominate its orbit, which ruled out asteroids from the get-go as no asteroid in the belt actually cleared out its own orbital path, instead being part of the larger asteroid belt it too became a dwarf planet.
What about the planet itself? Well we know Ceres is made of mostly ice and rock there is a rocky interior with an icy exterior. We have interestingly observed what could be the remnant of an ocean that once held liquid water, an essential building block for life as we know it. On the surface ice mixes with various minerals and you can even find iron rich clay on surface. Ceres' surface is relatively warm for an asteroid with an average surface temperature of 235 Kelvin (-38° C). About five years ago in January 2014 we detected water vapor in several regions. The water vapor comprises more of Ceres’ external makeup than we realized. This could be the result of outgassing or from a unique type of volcano called a cryovolcano. This outgassing is actually a common feature of a comet. Internally Ceres’ mantle which is about 100 kilometers thick could contain up to 200 million cubic kilometers of water which is more than all the fresh water on Earth. Aside from all that, some other interesting things about the planet is that the mass accounts for approximately 1/3 of the entire asteroid belt’s total mass and it is the only belt object to be rounded by its own gravity. It is also the only classified dwarf planet inside the orbit of Neptune and it's the 33rd largest celestial body in the solar system. But what makes this planet so interesting is its composition lends itself to the formation of life as we know it and so perhaps there is some form of life that has existed or currently exists near its surface.
In another of Ceres craters some organic materials were discovered, they are a key ingredient for life to form and thrive, but what made it more interesting was the fact that these more organic materials seem to be endogenous, meaning they originated from inside the planet itself. Scientists were very pleased with this discovery but something a bit more well-known that brings the discussion of life to the table are the famous bright spots, a seemingly unique feature to Ceres. A year after detecting water vapor, NASA's Dawn spacecraft went to observe Ceres and entered its orbit in March 2015 this was when its cratered surface was discovered and two very distinct bright spots were observed inside one such crater. Though NASA often dismissed this as reflectivity for glaciers it was initially thought to be a cryovolcano. A concept mentioned earlier cryovolcanoes are a type of volcano that spirit iced water methane and ammonia instead of magma. 18 months after the bright spot discovery dawn scientists documented a mountain on Ceres named Ahuna Mons this mountain is fairly unique as the dwarf planet doesn't seem to have any other mountains. What it did have was bright streaks similar in appearance to the bright spots down his side. This pointed to the theory that Ahuna Mons is a cryovolcano. Near infrared spectra of the planet also suggested that the geologic activity may have something to do with the spots, now however NASA scientists believe the spots may have been caused by a form of brine related to reflective ammonia salts on the surface. It may well be the cryovolcano theory as the bright spots seemed to shine when they are even not facing the Sun. Some theorize that life may have existed in the past in the liquid water oceans of Ceres but not anymore. Even if it is devoid of life now the planet does boast favorable conditions for life as we know it water on the surface vapor and the 20% carbon mass could provide the right conditions for organic chemistry but for now we really don't know.
Habitability is no guarantee of presence of life. Just because Ceres is habitable and suitable for life and primitive life, that doesn't mean a single microorganism has to exist at all on a surface perhaps the shiny spots to open the door to the possibility of some form of life but until more studies are done we cannot confirm nor deny this if life in any form actually does exist on Ceres. However then it's incredibly likely they involved independently to earth and if so the process of life formation may be more robust and common than we expected. If we can find life prevalent and resilient enough to survive for billions of years on the surface of an asteroid then who knows what earth-like planets such as Kepler 22b could hold.
Life could be common, if Ceres has life against all odds then Jupiter's Europa stands a very good chance of having some form of life in its oceans and who knows what could be elsewhere in the solar system. Let's hope future observations of Ceres and such other places can reveal this possibility, because if so, it opens up the potential for an entire galaxy full of amazing very life for us to discover and learn from in all of its corners imagine the kind of knowledge such a library of interplanetary species would give us and unlocking all of their potential could begin with this remote tiny but brilliant celestial body that is the planet of Ceres.