(Image credit: E.L. Trouvelot, New York Public Library)
A chromolithograph of the planet Jupiter, observed Nov. 1, 1880, at 9:30 p.m. The piece of art reveals Jupiter’s Great Red Spot, akin to a hurricane on Earth, which has been raging on the planet for hundreds of years.
Tangle of Sunspots
(Image credit: E.L. Trouvelot, New York Public Library)
A group of sunspots and veiled spots observed on June 17, 1875 at 7:30 a.m. Sunspots are magnetic regions on the sun, which appear in images as dark spots and whose magnetic field strengths thousands of times stronger than Earth’s magnetic field.
Aurora Borealis
(Image credit: E.L. Trouvelot, New York Public Library)
Aurora borealis as observed March 1, 1872, at 9:25 p.m. Glowing lights that seem to dance across the sky, the aurora borealis occurs when charged particles from the sun enter our atmosphere, smashing into the gases there and releases energy in the form of light. Depending on the gas molecule involved in the smash-up, the lights take on different colors. For instance, a common color, pale yellowish-green, is produced by collisions with oxygen molecules, while blue or purplish-red result from crashes with nitrogen molecules, according to the Northern Lights Center in Canada. They are called aurora borealis in the Northern Hemisphere and aurora australis in the Southern Hemisphere.
Orion’s Nebula
(Image credit: E.L. Trouvelot, New York Public Library)
The great nebula in Orion produced from a study made in the years 1875-1876.
Moon Mare
(Image credit: E.L. Trouvelot, New York Public Library)
Mare Humorum is a small circular mare, spanning about 275 miles (443 kilometers), on the near side of the moon. Shown here is Trouvelot’s artwork of the mare based on a study in 1875. It is about 275 miles across. The mountains around the mare mark the edge of an old impact basin, according to NASA.
The Red Planet
(Image credit: E.L. Trouvelot, New York Public Library)
The planet Mars observed Sept. 3, 1877, at 11:55 p.m.
Shooting Stars
(Image credit: E.L. Trouvelot, New York Public Library)
The November meteors, as observed between midnight and 5 a.m. on the night of Nov. 13-14 1868.
Sun Loops
(Image credit: E.L. Trouvelot, New York Public Library)
Solar protuberances, as observed on May 5, 1873, at 9:40 a.m. These structures form from the gases of the sun’s outer atmosphere called the corona. They have lower temperatures compared with the surrounding environment and can extend millions of miles.
A Great Comet
(Image credit: New York Public Library)
In June 1881, a brilliant comet streaked across the skies of the northern hemisphere. E.L. Trouvelot illustrated the Great Comet of 1881 as he saw it.
Total Eclipse
(Image credit: New York Public Library)
A total eclipse of the sun observed July 29, 1878, at Creston, Wyoming Territory and illustrated by Trouvelot.
Saturn’s Stunning Light
(Image credit: New York Public Library)
Trouvelot observed Saturn on November 30, 1874 and produced this illustration.
There’s no questioning the fact that the universe is weird. Just look outside and you’ll see all manner of strange, self-reproducing flora and fauna, crawling upon a blue ball of semimolten rock covered in a thin, hard shell and blanketed by a tenuous film of gases. Yet our own planet represents a tiny fraction of the peculiar phenomena that can be found lurking throughout the cosmos, and every day astronomers turn up new surprises. In this gallery, we take a look at some of the most outlandish objects in space.
Mysterious Radio Signals
Since 2007, researchers have been receiving ultrastrong, ultrabright radio signals lasting only a few milliseconds. These enigmatic flashes have been called fast radio bursts (FRBs), and they appear to be coming from billions of light-years away (they’re not aliens, it’s never aliens). Recently, scientists managed to capture a repeating FRB, which flashed six times in a row, the second such signal ever seen and one that could help them unravel this mystery.
Nuclear Pasta
The strongest substance in the universe forms from the leftovers of a dead star. According to simulations, protons and neutrons in a star’s shriveled husk can be subject to insane gravitational pressure, which squeezes them into linguini-like tangles of material that would snap — but only if you applied to them 10 billion times the force needed to shatter steel.
Haumea Has Rings
The dwarf planet Haumea, which orbits in the Kuiper Belt out beyond Neptune, is already unusual. It has a strange elongated shape, two moons and a day that lasts only 4 hours, making it the fastest-spinning large object in the solar system. But in 2017, Haumea got even weirder when astronomers watched it pass in front of a star and noticed extremely thin rings orbiting around it, likely the result of a collision sometime in the distant past.
A Moon with a Moon
What’s better than a moon? A moon orbiting a moon, which the internet has dubbed a moonmoon. Also known as submoons, moonitos, grandmoons, moonettes and moooons, moonmoons are still only theoretical, but recent calculations suggest that there’s nothing impossible about their formation. Perhaps astronomers may one day discover one.
Dark-Matter-Less Galaxy?
Dark matter — the unknown substance comprising 85 percent of all matter in the universe — is strange. But researchers are at least sure about one thing: Dark matter is everywhere. So team members were scratching their heads over a peculiar galaxy they spotted in March 2018 that seemed to contain hardly any dark matter. Subsequent work suggested that the celestial oddity did in fact contain dark matter, though the finding paradoxically lent credence to an alternative theory positing that dark matter doesn’t exist at all. Get it together, astronomers!
The Most Bizarre Star
When astronomer Tabetha Boyajian of Louisiana State University and her colleagues first saw the star known as KIC 846285, they were flummoxed. Nicknamed Tabby’s star, the object would dip in brightness at irregular intervals and for odd lengths of time, sometimes by as much as 22 percent. Different theories were invoked, including the possibility of an alien megastructure, but nowadays, most researchers believe the star to be surrounded by an abnormal ring of dust that’s causing the darkening.
Highly Electric Hyperion
The title of weirdest moon in the solar system could go to many celestial objects — Jupiter’s overly volcanic Io, Neptune’s geyser-spewing Triton. But one of the strangest looking is Saturn’s Hyperion, a pumice-stone-like irregular rock pockmarked with numerous craters. NASA’s Cassini spacecraft, which visited the Saturn system between 2004 and 2017, also found that Hyperion was charged with a “particle beam” of static electricity flowing out into space.
A Guiding Neutrino
The single, high-energy neutrino that struck Earth on Sept. 22, 2017, wasn’t, on its own, all that extraordinary. Physicists at the IceCube Neutrino Observatory in Antarctica see neutrinos of similar energy levels at least once a month. But this one was special because it was the first to arrive with enough information about its origin for astronomers to point telescopes in the direction it came from. They figured out that it had been flung at Earth 4 billion years ago by a flaring blazar, a supermassive black hole at the center of a galaxy that had been consuming surrounding material.
The Living Fossil Galaxy
DGSAT I is an ultradiffuse galaxy (UDG), meaning it is as big as a galaxy like the Milky Way but its stars are spread out so thinly that it is nearly invisible. But when scientists saw the ghostly DGSAT 1 in 2016, they noticed that it was sitting all alone, quite unlike other UDGs, which are typically found in clusters. Its characteristics suggest that the faint object formed during a very different era in the universe, back just 1 billion or so years after the Big Bang, making DGSAT 1 a living fossil.
Double Quasar Image
Massive objects curve light, enough so that they can distort the image of things behind them. When researchers used the Hubble Space Telescope to spot a quasar from the early universe, they used it to estimate the universe’s expansion rate and found that it is expanding faster today than it was back then — a finding that disagrees with other measurements. Now physicists need to figure out if their theories are wrong or if something else strange is going on.
Infrared Stream from Space
Neutron stars are extremely dense objects formed after the death of a regular star. Normally, they emit radio waves or higher-energy radiation such as X-rays, but in September 2018, astronomers found a long stream of infrared light coming from a neutron star 800 light-years away from Earth — something never before observed. The researchers proposed that a disk of dust surrounding the neutron star could be generating the signal, but the ultimate explanation has yet to be found.
Rogue Planet with Auroras
Drifting through the galaxy are rogue planets, which have been flung away from their parent star by gravitational forces. One particular peculiarity in this class is known as SIMP J01365663+0933473, a planet-size object 200 light-years away whose magnetic field is more than 200 times stronger than Jupiter’s. This is strong enough to generate flashing auroras in its atmosphere, which can be seen with radio telescopes.
As perceived security threats mount in Earth’s orbit, countries around the world are following the example of the United States and creating their own “space forces.”
Nine months ago, in December 2019, the U.S. Space Force was born. The new military branch was created with a focus to protect the nation’s satellites and other space assets, which are vital to everything from national security to day-to-day communications.
Now, countries including France, Canada and Japan are following suit, as leaders from those countries’ “space force” analogs said Thursday (Sept. 10) during the 2nd Summit for Space Sustainability, an online event hosted by the nonprofit Secure World Foundation.
So, why do these countries, as well as nations like Russia and China, want a military presence in space?
According to Maj. Gen. John Shaw, the combined force space component commander of the U.S. Space Command and commander of space operations command for the U.S. Space Force, it’s analogous to asking “why do ocean-going or seafaring nations want a Navy?” They want “to secure that domain for all activity and to deter threats in that domain,” he said during the summit on Thursday. “Nobody wants a war in space.”
Space torpedoes
The threats that the U.S. Space Force aims to deter are not theoretical and have already started popping up, Shaw explained.
For example, in April and again in July, the Space Force detected an anti-satellite missile test conducted in low Earth orbit by Russia. The April test “provides yet another example that the threats to the U.S. and allied space systems are real, serious and growing,” Space Force commander Gen. John “Jay” Raymond stated following that incident.
Satellite tests are no uncommon occurrence in low Earth orbit. However, according to Shaw, Russia was testing what looked like a “space torpedo.”
“And I could add many other threats that we’ve seen along the continuum of space counter-space capabilities,” Shaw added, citing “the proliferation of electromagnetic spectrum jammers” as an example. Jammers deliberately interfere with information beaming to or from Earth-orbiting satellites.
And, while the U.S. Space Force is actively working to combat these threats, other countries are following suit. “We share the same concerns,” French Space Command major general and commander Michel Friedling said during the summit.
“We want to make sure that we’re not riding coattails,” Brig. Gen. Mike Adamson, the director general and Space/Joint Force Space Component Commander for the Canadian Department of National Defence added during the summit. Canada wants to “maintain our place at the table,” Adamson said.
Satellite swarm threats
However, intentional, nefarious threats from other nations are not the only concern for the U.S. Space Force and other countries’ growing military space efforts. Constellations of satellites from private companies here on Earth can also pose serious issues.
The “proliferation in low Earth orbit of commercial satellites, in some ways, might be the greatest threat to space sustainability,” Shaw said, adding that this will only really be a threat if not done properly.
Recently, SpaceX began launching large numbers of satellites to low Earth orbit, in an effort to grow a huge constellation called Starlink that’s designed to provide internet access around the globe.
SpaceX has already lofted more than 700 Starlink satellites. But Elon Musk’s company has approval from the U.S. Federal Communications Commission to launch as many as 12,000 satellites into orbit and may want to grow the constellation even larger than that someday.
And SpaceX isn’t the only one with such ambitions. For example, Amazon aims to launch about 3,200 satellites for its own internet constellation, Project Kuiper.
Putting so many satellites into orbit raises a number of potential concerns, including the proliferation of “space junk.” While SpaceX’s Starlink satellites are designed to fall out of orbit and burn up in Earth’s atmosphere over time, the presence of so many spacecraft in orbit at once increases the possibility of collisions, which would generate huge swarms of debris. These swarms would then pose a potential threat to other satellites in orbit.
As Shaw mentioned, the Space Force also expects to see more and more “academic” or science-focused satellites launched into orbit.
With all of these new satellites expected to launch, the Space Force wants to ensure that they are made with a “responsible design so that they don’t become a navigational hazard,” Shaw said. “As we continue to expand across all sectors…how do we do that in a responsible way?”
This is a concern for other countries dipping their toes into space-focused military branches as well.
These emerging military enterprises have to consider things such as, “How do we coordinate with the private actors in space?” Friedling said.
Friedling also brought up the issue of security for these private or science-focused satellites. “Do they want to be protected or escorted?” he asked, comparing these craft to private ships that were escorted in convoys during World War I to keep them safe from enemy attack from newly introduced submarines.
The space military representatives, which also included Maj. Gen. Hiroaki Sakanashi, the director general of the project promotion group for emerging domains and programs in the Air Staff Office in Japan, seemed to agree that these are concerns that should be addressed by space-focused military efforts.
“You invite conflict when there’s weakness, and I believe you deter conflict when there is strength, and that is the path we’re on,” Shaw said. Taking this approach “will lead us, I believe, to a more strategically stable situation that deters conflict in space,” he added.
“Certainly, Canada is going along those lines as well,” Adamson agreed.
Email Chelsea Gohd at cgohd@space.com or follow her on Twitter @chelsea_gohd. Follow us on Twitter @Spacedotcom and on Facebook.
When matter is compressed beyond a certain density, a black hole is created. It is called black because no light can escape from it. Some black holes are the tombstones of what were once massive stars. An enormous black hole is thought to lurk at the center of the Milky Way galaxy.
All the mass of a black hole is concentrated into a point at its center called the singularity. Gravity surrounding the singularity is so strong, you would have to travel faster than light to escape. This creates a spherical zone surrounding the singularity called the event horizon from which nothing can escape.
At about one and a half times the diameter of the event horizon, photons become trapped in circular orbits around the black hole. [Gallery: Black Holes of the Universe]
All the mass of a black hole is concentrated into a point at its center called the singularity. Gravity surrounding the singularity is so strong, you would have to travel faster than light to escape. This creates a spherical zone surrounding the singularity called the event horizon from which nothing can escape.
In theory, a black hole of any size could exist. A black hole with the mass of our sun would be 3.7 miles (6 km) in diameter. In practice, the death of a star like the sun does not compress the material enough to form a black hole. Stars with about two times the sun’s mass or more form black holes. Astronomers recognize two major types. [The Strangest Black Holes in the Universe]
Stellar-mass black holes have the mass of several sun-sized stars. They form when a dying star explodes in a supernova, then collapses under its own gravity. Matter drawn toward the black hole forms an accretion disc.
Supermassive black holes can have billions of times our sun’s mass. Matter drawn toward a supermassive black hole is compressed, heats up and may be blasted out into jets thousands of light-years long.
Stellar-mass black holes are scattered throughout the galaxy. A supermassive black hole lies at the core of many galaxies, including our own. The Milky Way’s supermassive black hole is called SgrA* (Sagittarius A-star), and it is seen from Earth in the constellation Sagittarius. The supermassive black hole is about 26,000 light-years away, and has a mass of at least 4 million times the mass of our sun.
The powerful gravity of a black hole distorts light, space and time. One effect is gravitational lensing. A black hole between us and a distant galaxy will bend the rays of light, causing our view of the galaxy to be warped. We have yet to photograph a black hole in detail, but simulations suggest that the supermassive black hole at the Milky Way’s center might appear to be a distorted crescent.
Black holes aren’t supposed to make flashes of light. It’s right there in the name: black holes.
Even when they slam into each other, the massive objects are supposed to be invisible to astronomers’ traditional instruments. But when scientists detected a black hole collision last year, they also spotted a weird flash from the crash.
On May 21, 2019, Earth’s gravitational wave detectors caught the signal of a pair of massive objects colliding, sending ripples cascading through spacetime. Later, an observatory called the Zwicky Transient Facility (ZTF) caught a blast of light. As scientists looked at the two signals, they realized both came from the same patch of sky, and researchers started wondering whether they had spotted the rare visible black hole collision.
“This detection is extremely exciting,” Daniel Stern, coauthor of a new study on the discovery and an astrophysicist at NASA’s Jet Propulsion Laboratory in California, said in a NASA statement. “There’s a lot we can learn about these two merging black holes and the environment they were in based on this signal that they sort of inadvertently created.”
Here’s what scientists think happened in this strange case. The two black holes that merged were locked in the disk surrounding a quasar, a supermassive black hole that shoots out blasts of energy.
“This supermassive black hole was burbling along for years before this more abrupt flare,” Matthew Graham, an astronomer at Caltech and the project scientist for ZTF, said in a university statement.
That in and of itself isn’t so strange, according to his colleague. “Supermassive black holes like this one have flares all the time,” co-author Mansi Kasliwal, an astronomer at Caltech, said in the statement. “They are not quiet objects, but the timing, size and location of this flare was spectacular.”
Scientists suspect, based on the pairing of gravitational waves and light, that the flare sprang from two small black holes merging within the accretion disk of the supermassive black hole. The supermassive black hole’s incredibly strong gravity affects the smaller stuff in the disk, even other black holes.
“These objects swarm like angry bees around the monstrous queen bee at the center,” co-author K. E. Saavik Ford of the City University of New York Graduate Center, the Borough of Manhattan Community College and the American Museum of Natural History, said in the statement. “They can briefly find gravitational partners and pair up but usually lose their partners quickly to the mad dance. But in a supermassive black hole’s disk, the flowing gas converts the mosh pit of the swarm to a classical minuet, organizing the black holes so they can pair up.”
The flash of light doesn’t come from the merger itself, the scientists think. Instead, the force of the merger sends the now-a-little-larger black hole flying off, through the gas surrounding it in the supermassive black hole’s accretion disk. The gas, in turn, produces the flare after a delay of days or weeks, the theory goes according to the statement. In the case of this event, scientists detected the flare about 34 days after the gravitational wave signal.
That’s not a guarantee that this explanation fits what happened, the researchers said.
“The flare occurred on the right timescale, and in the right location, to be coincident with the gravitational-wave event,” Graham said. “We conclude that the flare is likely the result of a black hole merger, but we cannot completely rule out other possibilities.”
The results are described in a paper published on Thursday (June 26) in the journal Physical Review Letters.
Watch for the violent solarmaximum in 2014 — you can’t miss it
What does 10 years mean to our 4.6 billion-year-old sun? Probably about as much as the last millionth of a second meant to you. Still, every decade that our old sun burns on is a decade of turbulent, sometimes violent change — a fact that becomes beautifully evident in a new time-lapse video from NASA’s Solar Dynamics Observatory (SDO).
What does 10 years mean to our 4.6 billion-year-old sun? Probably about as much as the last millionth of a second meant to you. Still, every decade that our old sun burns on is a decade of turbulent, sometimes violent change — a fact that becomes beautifully evident in a new time-lapse video from NASA’s Solar Dynamics Observatory (SDO).
What does 10 years mean to our 4.6 billion-year-old sun? Probably about as much as the last millionth of a second meant to you. Still, every decade that our old sun burns on is a decade of turbulent, sometimes violent change — a fact that becomes beautifully evident in a new time-lapse video from NASA’s Solar Dynamics Observatory (SDO).
In the stunning video, titled “A Decade of Sun,” astronomers compiled 425 million high-definition images of the sun, snapped once every 0.75 seconds between June 2, 2010 and June 1, 2020. Each second of the video represents one day in the sun’s life, and the entire decade blazes by in about 60 minutes (though you can see our 6-minute highlight reel above).
During that decade, the sun undergoes a sea change, slowly bubbling with enormous magnetic ripples known as sunspots, which peaked around 2014 before fading away again. The sun’s quiescence wasn’t a surprise; every 11 years or so, the sun’s magnetic poles suddenly switch places; North becomes South, solar magnetic activity begins to wane, and the sun’s surface starts to look like a tranquil sea of yellow fire. This period of relative calm is called a solar minimum (and we are currently in the midst of one).
Halfway between one decade’s flip-flop and the next, however, a violent shift occurs. Magnetic activity increases to a vibrant high, known as a solar maximum, and the star’s surface ripples with gigantic sunspots, bristles with lashing magnetic field lines and pops with plasma explosions known as solar flares. Each maximum peaks with another magnetic pole reversal, signaling the start of a new solar cycle.
These changes are hard to spot from Earth with the naked eye (though solar maxima do result in more visible auroras at lower latitudes around the world), but NASA’s SDO satellite sees them clearly as it monitors our star in extreme ultraviolet light. These ultra-energetic wavelengths cut through the sun’s glare and reveal the abundant magnetic changes in the sun’s outermost atmosphere, or corona. It’s a stunning spectacle to see — even if the sun has probably already forgotten all about it.
How many intelligent alien civilizations are out there among the hundreds of billions of stars in the spiral arms of the Milky Way? According to a new calculation, the answer is 36.
That number assumes that life on Earth is more or less representative of the way that life evolves anywhere in the universe — on a rocky planet an appropriate distance away from a suitable star, after about 5 billion years. If that assumption is true, humanity may not exactly be alone in the galaxy, but any neighbors are probably too far away to ever meet.
On the other hand, that assumption that life everywhere will evolve on the same timeline as life on Earth is a huge one, said Seth Shostak, a senior astronomer at the SETI Institute in Mountain View, California, who was not involved in the new study. That means that the seeming precision of the calculations is misleading.
“If you relax those big, big assumptions, those numbers can be anything you want,” Shostak told Live Science.
Distant neighbors
The question of whether humans are alone in the universe is a complete unknown, of course. But in 1961, astronomer Frank Drake introduced a way to think about the odds. Known as the Drake equation, this formulation rounds up the variables that determine whether or not humans are likely to find (or be found by) intelligent extraterrestrials: The average rate of star formation per year in the galaxy, the fraction of those stars with planets, the fraction of those planets that form an ecosystem, and the even smaller fraction that develop life. Next comes the fraction of life-bearing planets that give rise to intelligent life, as opposed to, say, alien algae. That is further divided into the fraction of intelligent extraterrestrial life that develops communication detectable from space (humans fit into this category, as humanity has been communicating with radio waves for about a century).
The final variable is the average length of time that communicating alien civilizations last. The Milky Way is about 14 billion years old. If most intelligent, communicating civilizations last, say, a few hundred years at most, the chances that Earthlings will overlap with their communications is measly at best.
Solving the Drake equation isn’t possible, because the values of most of the variables are unknown. But University of Nottingham astrophysicist Christopher Conselice and his colleagues were interested in taking a stab at it with new data about star formation and the existence of exoplanets, or planets that circle other stars outside our own solar system. They published their findings June 15 in The Astrophysical Journal.
“This paper couldn’t have been written a few years ago,” Conselice told Live Science.
The team calculated the age distribution of stars in the Milky Way, looking for those at least 5 billion years old and presumably old enough to host a humanlike civilization. They found that 97% of stars in the Milky Way are older than 5 billion years. Our solar system, at 4.5 billion years old, is a relative newbie in the galaxy, Conselice said, so it made sense that many stars in the Milky Way are older.
The researchers then calculated the number of those stars that are dense enough and stable enough to host planetary systems. A third of the stars older than 5 billion years qualified. Next, using what astronomers now know about the distribution of exoplanets, the researchers estimated the number of rocky planets within the habitable zones of those stars. They also calculated which stars are metal-rich enough to have orbiting rocky planets with the kind of elements you might need to construct, say, a radio transmitter. Finally, they set a lower limit of the life span of a communicating civilization at 100 years, based on Earth’s timeline with radio technology so far.
The result? If life on other planets follows the same trajectory as on Earth, there are 36 intelligent, communicating extraterrestrial civilizations sharing the Milky Way with humans today. There is uncertainty in this estimate, with a range from four other civilizations up to 211. If alien civilizations are likely to be distributed evenly throughout the Milky Way, our nearest neighbor would likely be 17,000 light-years away.
That means we’re quite unlikely to get in touch. The researchers calculate that a theoretical alien civilization would have to be broadcasting detectable signals for approximately 3,060 years for us to pick them up. That means to establish a two-way conversation with such a civilization, humanity (and the aliens) would have to hold it together for another 6,120 years.
Questioning assumptions
There are more optimistic scenarios for meeting ET. If, for example, life can evolve any time after 5 billion years, but not necessarily right at 5 billion years, the number of possible civilizations in the Milky Way rises to about 928. In this case, a civilization has to communicate for just 1,030 years to make contact.
Ancient aliens and UFOs, or “unidentified flying objects,” have been the stuff of legends for centuries. Modern “eyewitness” accounts began to surface as early as the latter part of the 19th century with reports of “mystery airships” appearing in U.S. newspapers. During WWII, allied airmen’s eerie tales of encountering mysterious “foo fighters” captured our collective imagination, but it was after the Cold War that UFO sightings really took off. While the U.S. government started monitoring the skies for evidence that the Soviets might be developing secret stealth aircraft, many people believed—and continue to believe—that unexplained flying phenomena were of extra terrestrial origin. Pictures of so-called UFOs were touted as proof that alien visitors had made their way to Earth but even in the dark ages before Photoshop, it was easy enough to manipulate photographic technology. The following stories tell of possible UFO sightings, with photographs that may—or may not—prove that real close encounters may be closer than you think.
The problem with these numbers is that the authors filled in some of the blanks in the Drake equation with astronomical data while dispensing with some of the most complicated, controversial variables without much discussion, Shostak said. Does life really evolve on any rocky planet within the habitable zone of a sun-like star? Does intelligent life really reliably show up about 4.5 billion years later? Had a chance asteroid not knocked Earth around 66 million years ago, killing off the dinosaurs, the timeline of the evolution of intelligent life on Earth could look quite different, after all. Perhaps the most limiting variable, Shostak said, is the assumption that a communicating civilization only transmits signals for a century. That seems pessimistic even for human civilization, which has its struggles but seems unlikely to stop using radio waves in the next couple of months, he said.
The legend: At 2:25 p.m, alarm sirens installed in the event of a Japanese air raid sounded as flying objects were spotted in the skies above Los Angeles. A blackout was declared and anxious, terrified citizens followed the instructions to extinguish all lights.
At 3:16 p.m., searchlights swept the skies and anti-aircraft guns opened fire on the unidentified flying objects over the Pacific. Witnesses recount the formation of small red or silver-plated objects high-speed flying at a high altitude was untouched by the anti-aircraft salvos. The larger craft pictured flew off without sustaining damage as well.
The answer to the Drake equation “depends a lot on the probability of life developing on a world and on [intelligent life] developing on a world and on the lifetime of intelligence,” Shostak told Live Science. “Those are all big things that could change the answer by an order of magnitude.”
Washington, D.C.; July 19, 1952
1952-Washington, D. C.United States Air Force
The legend: Early in the history of ufology (the study of unidentified flying objects) in the United States, extra-terrestrial visitors may made themselves known to the leaders of the free world by allegedly buzzing over the White House, the Capitol building, and the Pentagon. Washington National Airport and Andrews Air Force Base picked up a number of UFOs on their radar screens on July 19, 1952, beginning a wave of sightings that are still unexplained to this day.
Conselice said the calculations are a way of understanding humanity’s existence — and its future. If there turn out to be more civilizations out there in the galaxy than the new math predicts, that means that either life can evolve under far broader conditions than just Earth-like ones, or it means that civilizations tend to be far longer-lived than ours thus far.
Rosetta/Natal, South Africa; July 17, 1956
1956-South Africa.South African Air Force
The legend: This famous photograph is part of a series of seven similar images, and was taken in the Drakensberg Mountains by a well-respected member of South African society. The photographer maintained the veracity of her sightings for the remainder of her life. She passed away in 1994.
“If we find a lot of them, that’s a good sign that we might have a very long lifetime for our civilization,” Conselice said.
Santa Ana, California; August 3, 1965
1965-Santa Ana, California.Rex Heflin
The legend: This photograph was taken by highway traffic engineer Rex Heflin while driving near the Santa Ana freeway. Heflin did not report his sighting, however, his pictures were published by the Santa Ana Register on August 20, 1965. The photos were reportedly confiscated and controversy arose regarding their authenticity.
On the other hand, if the search for extraterrestrial life continues to turn up empty, it could mean that life only rarely evolves, or that when civilization arises, it tends to self-destruct rapidly. Perhaps, the Milky Way was relatively bustling a few billion years ago, but those sparks of life have since gone out. In the end, Shostak said, there is only one way to find out.
Tulsa, Oklahoma; 1965
1965-Tulsa, Oklahoma.Life Magazine
The legend: In 1965, a series of strange low-flying objects were reported almost nightly by people of all ages and walks of life across the United States. As the year progressed, the number of these reports rose dramatically. On the night of August 2, 1965, thousands of people in four Midwestern states witnessed spectacular aerial displays by large formations of UFOs. That same night, a multi-colored disc was photographed in Tulsa, Oklahoma as it was observed performing low-altitude maneuvers. This picture was extensively analyzed, pronounced authentic, and later published by Life magazine.
“You’re only going to be able to write a paper in which you can make any estimate of how many alien societies there are once you find one or two,” Shostak said.
Provo, Utah; July 1966
1966-Provo, Utah.United States Air Force
The legend: The pilot of a twin-engine USAF C-47 “Skytrain” transport aircraft took this photograph at approximately 11 a.m on a July morning in 1966 as he was flying over the Rocky Mountains, about 40 kilometers southwest of Provo, Utah. The Condon Committee (a University of Colorado group funded by the United States Air Force to study unidentified flying objects) analyzed the negative and concluded that the photograph depicts an ordinary object thrown in the air. Many ufologists disagreed with their conclusion.
Apollo 16 / Moon; April 16-27, 1967
1972-Apollo 16.NASA
The legend: The UFO is pictured at just right of the top center of the photo. No explanation has been given for the object.
Tavernes, France; 1974
1974-Tavernes, France.Anonymous French Medical Doctor
The legend: This classic image was taken by an anonymous French medical doctor in Var, France. Skeptics tried to discredit the picture on the grounds that “luminous rays cannot end like this.” Normally, they do not, however, there are other possible explanations, such as these are not luminous rays at all but light emissions resulting from ionized air. Many still believe the object in the photograph is a UFO.
Waterbury, Connecticut; 1987
1987-Waterbury, Connecticut.Randy Etting
The legend: Randy Etting, a commercial airline pilot with over 30 years’ experience, spent a lot of time looking at the sky. On the night he took this photograph, he’d witnessed a number of orange and red lights approaching from the west. He got his binoculars and called his neighbors to come outside. By this time, the object was a great deal closer and seemed to be over I-84, just east of Etting’s home. He reported that the lights were shimmering like distortion from engine heat, but he could hear no sound. “As the UFO passed over I-84, cars in both the east and westbound lanes began pulling over and stopping,” he stated. “The UFO displayed a semi-circular pattern of very bright multicolored lights. Five motorists reported that as the object became visible a number of cars lost power and had to pull off the highway.”
Gulf Breeze, Florida; 1987
1987-Gulf Breeze, Florida.Ed Walters
The legend: In November 1987, the Gulf Breeze Sentinel published a group of UFO photos they’d gotten from a local contractor named Ed Walters. Shortly after Walters’ photos hit the local newspaper, more UFO photographers came forward with stories or sightings and more images, both still and moving.
However, thanks to a subsequent Pensacola News Journal feature by reporter Craig Myers the Sentinel’s coverage was dismissed as “uncritical” and “sensationalist.” Using a Styrofoam UFO model (found in the attic of the house where Walters was living when the Sentinel photos were first published), Myers was able to duplicate the original photos almost shot for shot.
The legend: The photographer of this famous Belgian UFO photograph remains anonymous. Taken on an April night during a well-documented UFO wave, the photo shows a triangle-shaped object with lights. As the original photo was too dark for the outline of the object to be seen clearly, it was subsequently enhanced, but that is supposedly the only correction made.
Puebla, Mexico; December 21, 1944
1994-Puebla, Mexico.Carlos Diaz
The legend: Carlos Diaz, a photographer with an extensive collection of UFO images, shot this image while taking photos of the eruption of Mt. Popocatepetl in Puebla, Mexico. The photo shows a glowing, yellowish, disc-shaped object with a red hue toward the top, and windows or portholes. It has since been authenticated by many photographic experts and published in numerous magazines, newspapers, and books.
Phoenix, Arizona; 1977
1997-Phoenix, Arizona.CNN News
The legend: This photograph is one of many depicting one of the most publicized UFO events in history. First observed in a hexagram pattern at about 7:30 p.m. over the Superstition Mountains area east of Phoenix, the characteristic 8 + 1 formation of amber orbs was next seen in two separate arc patterns with “trailing lights” over the Gila River area at about 9:50, and again at 10 p.m. at the southern edge of Phoenix. Thousands reported seeing these objects and a handful of witnesses videotaped them on camcorders.
Taipei, China; 2004
Taipei, China.Lin Qingjiang
The legend: Lin Qingjiang, a worker in Hualian County of Taipei, saw what he believed to be UFO at about 10 p.m. as he was resting outside his home. Lin was quoted as saying that the object, shaped like a large bamboo hat, flew east and west five times within 10 minutes, during which time he as able to capture this photo on his cell phone.
Kaufman, Texas; January 21, 2005
2005-Kaufman, Texas.lawwalk
The legend: The photographer states: “I was out today taking pictures of the chemtrails at 11:35 a.m. I was aiming my camera at a scrawny little cloud. As I was snapping the picture, I noticed a flash in the sky through the viewfinder. When the picture came on the screen, I noticed a gold-colored object at the top of the cloud I had captured also. I looked back where it was and of course, it was gone. I really couldn’t tell much of what it [might] be until I downloaded it to my computer. I zoomed in on it and nearly fell out of my chair. It appears to be a craft of some kind with maybe windows or ports on the right side, in the middle. It also appears to be emanating a gas or some type of energy field around it, mainly at the top.”
Valpara, Mexico; 2004
2004-Valpara, Mexico.Mercury newspaper-Mexico
The legend: This image was taken by Valpara newspaper reporter Manuel Aguirre who noticed a band of glowing lights in the distance over the city skyline. This photograph has not been debunked, and to date is considered legitimate. The unknown object appears to be circular or spherical in shape.
Modesto, California; 2005
2005-Modesto, California.R. David Anderson
The legend: The unnamed photographer states: “I noticed some kind of craft toward my left that appeared from behind a tree . . . in our front yard. I rapidly rotated my camera on its mount and took one picture. There were several brilliant lights that surrounded this craft. It was impossible to make out the shape of the craft because the lights were so brilliant. The lights did not strobe or flash [as] a normal aircraft array would. Each light glowed with the same intensity and color as a sodium-vapor type street lamp
The entire arc of the Milky Way can be seen in the southern sky in this view from the European Southern Observatory’s Very Large Telescope at the Paranal Observatory in Chile’s Atacama Desert.
Seated in the Atacama Desert of Chile, the European Southern Observatory (ESO)’s Very Large Telescope (VLT) consists of four main telescopes and four smaller telescopes that can be used separately or combined into a single larger instrument powerful enough to distinguish two car headlights at the distance of the moon.
World’s most advanced optical instrument
The VLT is located at Paranal Observatory in the Atacama Desert. The four Unit Telescopes boast 8.2-meter (27 feet) mirrors. Just one of these instruments can spot objects that are 4 billion times fainter than what can be seen with the unaided eye. According to the ESO’s website, the VLT is “the world’s most advanced optical telescope.”
The first of the four instruments, Unit Telescope 1 (UT1), saw first light on May 25, 1998, and went into scientific operations on April 1, 1999. UT2 saw first light only four days before the observatory’s March 5, 1999, inauguration.
The four Unit Telescopes sit in compact, thermally controlled buildings that rotate with the instruments. These buildings minimize adverse effects, such as turbulence in the telescope tube, on observations.
At the inauguration, the four Unit telescopes were given names in the Mapuche language, from an indigenous people living in the area south of Santiago de Chile. Chile’s schoolchildren participated in the naming, with an essay by then-17-year-old Jorssy Albanez Castilla unanimously selected by the committee.
UT1 is known as Antu (an-too), which means the sun.
UT2 is Kueyen (quay-yen), or the moon.
UT3 is Melipal (me-li-pal), or the Southern Cross).
UT4 is Yepun (ye-poon), or the evening star (Venus).
The VLT also contains four moveable 1.8-meter Auxiliary Telescopes. All eight telescopes are currently operational.
Together, the eight telescopes can create a massive interferometer. However, the Unit Telescopes are more often used individually, and are only available to be combined for a limited number of nights each year. The four smaller Auxiliary Telescopes, however, are available to allow the interferometer to operate each night.
In February 2018, the ESPRESSO instrument (Echelle SPectrograph for Rocky Exoplanet and Stable Spectroscopic Observations) on the VLT allowed the four Unit Telescopes to combine light from all four telescopes for the first time, making the VLT the largest optical telescope in existence in terms of collecting area. Due to the complexity involved, the light from the four had not been previously combined; only three Unit Telescopes could be combined at once.
“This impressive milestone is the culmination of work by a large team of scientists and engineers over many years,” project scientist Paolo Molaro said in a statement. “It is wonderful to see ESPRESSO working with all four Unit Telescopes, and I look forward to the exciting science results to come.”
A system of mirrors, prisms and lenses transmits the light from each Unit Telescope to the ESPRESSO instrument up to 226 feet (69 meters) away. ESPRESSO can collect the light from all four Unit Telescopes together, or from each one individually.
“ESO has realized a dream that dates back to the time when the VLT was conceived in the 1980s: bringing the light from all four Unit Telescopes on Cerro Paranal together at an incoherent focus to feed a single instrument!” said ESPRESSO instrument scientist Gaspare Lo Curto.
The science of the VLT
Over nearly two decades, the VLT has made significant contributions to astronomy, snapping the first image of an exoplanet, capturing the first direct measurements of the atmosphere of a super-Earth, and taking the universe’s cosmic temperature. In addition, the observatory’s hotel served as a villain’s hideout in the James Bond flick, “Quantum of Solace.”
In 2004, a team of European and American astronomers studying the TW Hydrae Association, a group of very young stars and other objects, spotted a red speck of light near one of the association’s brown dwarfs. The object was more than 100 times fainter than its parent star. Further observations confirmed that it was an exoplanet orbiting its star at 55 times the Earth-sun distance.
“Our new images show convincingly that this really is a planet, the first planet that has ever been imaged outside of our solar system,” ESO astronomer Gael Chauvin said in a statement.
In 2008, a team of scientists used the VLT to discover and image an object near the star Beta Pictoris. Most directly imaged exoplanets lie far from their stars, past where Neptune would orbit, where stellar light is dimmer. In contrast, the planet Beta Pictoris b lies much closer, where Saturn would orbit.
“Direct imaging of extrasolar planets is necessary to test the various models of formation and evolution of planetary systems,” researcher Daniel Rouan said in a statement. “But such observations are only beginning. Limited today to giant planets around young stars, they will in the future extend to the detection of cooler and older planets, with the forthcoming instruments on the VLT and on the next generation of optical telescopes.”
Spin class
Researchers also used the VLT to determine how fast Beta Pictoris b is spinning, clocking the massive planet almost 62,000 mph (100,000 km/h) at its equator. In comparison, Earth’s equator spins at only 1,056 mph (1,700 km/h), while Jupiter travels at about 29,000 mph (47,000 km/h). This was the first time an exoplanet’s rotation rate had been determined.
ESO/Stéphane Guisard
The sky appears to rotate above ESO’s Very Large Telescope in this long exposure. The star trails curve away from the celestial equator in the middle of the photo, where the stars seem to move in a straight line.
“It is not known why some planets spin fast and others more slowly,” researcher Remco de Kok said in a statement. “But this first measurement of an exoplanet’s rotation shows that the trend seen in the solar system, where the more massive planets spin faster, also holds true for exoplanets. This must be some universal consequence of the way planets form.”
The private organization Breakthrough Initiatives has enlisted the help of the VLT to hunt for planets around Earth’s closest star, Proxima Centauri. After helping to fund an upgrade to an existing instrument on the VLT, Breakthrough Initiatives will receive time for a “careful search” of the Proxima Centauri system for new planets. The improvement in the VLT Imager and Spectrometer for Mid Infrared instrument will equip it with a coronagraph, which blocks much of the light from a star, as well as an adaptive optics system to correct for distortions in starlight caused by Earth’s atmosphere. The upgrade is scheduled to be completed in 2019.
TRAPPIST-1
The VLT was also instrumental in revealing a system of seven Earth-sized planets just 40 light-years from Earth. The TRAPPIST-1 system boasts seven worlds, six of which appear to be rocky. All seven could potentially boast liquid water on their surface, though the innermost three appear to be too hot to hold onto it on more than a fraction of their surface. After an intriguing observation on the VLT in early 2016, when the system was first announced, researchers used multiple telescopes, including the VLT, to follow-up and observe the seven worlds.
“This is an amazing planetary system — not only because we have found so many planets, but because they are all surprisingly similar in size to the Earth!” said researcher Michaël Gillon of the STAR Institute at the University of Liège in Belgium.
The VLT has also been used to probe exoplanet atmospheres. In 2010, it studied the super-Earth GJ1214b and found an atmosphere dominated by thick clouds or hazes.
“This is the first super-Earth to have its atmosphere analyzed. We’ve reached a real milestone on the road toward characterizing these worlds,” researcher Jacob Bean said in a statement.
In 2008, the VLT took the cosmic temperature of the universe. By detecting carbon monoxide molecules in a galaxy located almost 11 billion light-years away, it allowed astronomers to obtain the most precise measurement of the cosmic temperature at such a remote epoch.
“This is the first time that these three molecules have been detected in absorption in front of a quasar, a detection that has remained elusive for more than a quarter century,” Cédric Ledoux, an ESO researcher, said in a statement.
The VLT has played a role in many other lines of research. According to the ESO’s website, an average of one paper a day is published in a peer-reviewed journal using the VLT’s observations.
A glowing laser shines forth from the European Southern Observatory’s Very Large Telescope, creating an artificial star 90 km above the surface of the Earth used to fine-tune the telescope’s optics.
Nebula Dominated by Cosmic Superbubble
ESO/Manu Mejias
The European Southern Observatory’s Very Large Telescope was used to obtain this view of the nebula LHA 120-N 44 surrounding the star cluster NGC 1929. Lying within the Large Magellanic Cloud, a satellite galaxy of our own Milky Way, this region of star formation features a colossal superbubble of material expanding outwards due to the influence of the cluster of young stars at its heart that sculpts the interstellar landscape and drives forward the nebula’s evolution.
Swirling Star Trails Over Yepun
ESO/F. Char
This view shows one of the Unit Telescopes of ESO’s Very Large Telescope (VLT) sitting beneath bright star trails circling the south celestial pole, a point in the sky that lies in the southern constellation of Octans (The Octant). Image released Jan. 7, 2013.
Omega Nebula’s Bright Pink Heart
ESO
This image of the Omega Nebula (Messier 17), captured by the European Southern Observatory’s Very Large Telescope, is one of the sharpest of this object ever taken from the ground. It shows the dusty, rosy central parts of the famous star-forming region in fine detail.
The VLT in Action
ESO/S. Brunier
The ESO Very Large Telescope (VLT) during observations. In this picture, taken from the VLT platform looking north-northwest at twilight, the four 8.2-metre Unit Telescopes (UTs) are visible.
Carina Nebula Infrared Image from ESO’s Very Large Telescope
ESO/T. Preibisch
This panorama of the Carina Nebula, a region of massive star formation in the southern skies, was taken in infrared light using the HAWK-I camera on the European Southern Observatory’s Very Large Telescope in Chile and released Feb. 8, 2012. Many previously hidden features, scattered across a spectacular celestial landscape of gas, dust and young stars, have emerged.
Milky Way in 360-Degree Panorama
ESO/S. Brunier
This amazing image seems to show the Milky Way streaming down not once, but twice, at ESO’s Very Large Telescope on Chile’s Cerro Paranal mountain. Actually, the photo shows a 360-degree panorama of the sky, so the two streams of stars are two halves of the band of the Milky Way arcing across the sky.
Yepun’s Laser and the Magellanic Clouds
ESO/B. Tafreshi/TWAN
This spectacular image shows Yepun, the fourth 8.2-metre Unit Telescope of ESO’s Very Large Telescope (VLT) facility, launching a powerful yellow laser beam into the sky.
War and Peace Nebula Captured by ESO’s Very Large Telescope
ESO
The European Southern Observatory’s Very Large Telescope has taken the most detailed image so far of a spectacular part of the stellar nursery called NGC 6357. The view shows many hot young stars, glowing clouds of gas and weird dust formations sculpted by ultraviolet radiation and stellar winds.
VLT Looks into the Eyes of the Virgin
ESO
This striking image, taken with the FORS2 instrument on the Very Large Telescope, shows a beautiful yet peculiar pair of galaxies, NGC 4438 and NGC 4435, nicknamed The Eyes. The larger of these, at the top of the picture, NGC 4438, is thought to have once been a spiral galaxy that was strongly deformed by collisions in the relatively recent past. The two galaxies belong to the Virgo Cluster and are about 50 million light-years away.
NGC 6729 – Baby Stars Spit Up High-Speed Jets in Photo
ESO
This very detailed false-colour image from ESO’s Very Large Telescope shows the dramatic effects of very young stars on the dust and gas from which they were born in the star-forming region NGC 6729.
Orion Nebula Spied by Hawk I 1024
ESO
The central region of the Orion Nebula (M42, NGC 1976) as seen in the near-infrared by the High Acuity Wide field K-band Imager (HAWK-I) instrument at ESO’s Very Large Telescope at Paranal.
Hot Stars Found Hidden in Galaxy’s Dusty Embrace
ESO
This infrared image of the nearby galaxy Messier 83 was taken by ESO’s Very Large Telescope (VLT) at the Paranal Observatory in Chile.
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Rose Red Stars
ESO/Manu Mejias, images
The star cluster NGC 371 appears in this new image from ESO’s Very Large Telescope.
Carina Nebula Imaged by the VLT Survey Telescope
ESO. Acknowledgement: VPHAS+ Consortium/Cambridge Astronomical Survey Unit
The spectacular star-forming Carina Nebula has been captured in great detail by the VLT Survey Telescope at ESO’s Paranal Observatory. This picture was taken with the help of Sebastián Piñera, President of Chile, during his visit to the observatory on June 5, 2012 and released on the occasion of the new telescope’s inauguration in Naples on Dec. 6, 2012.
Planetary Nebula Fleming 1
ESO/H. Boffin
This ESO Very Large Telescope image shows the planetary nebula Fleming 1 in the constellation of Centaurus (The Centaur). New observations suggest that a very rare pair of white dwarf stars lies at the heart of this object, with their orbital motions explaining the nebula’s remarkably symmetric jet structures. Image released Nov. 8, 2012.
Sharpening Up Jupiter
ESO/F. Marchis, M. Wong, E. Marchetti, P. Amico, S. Tordo
Amazing image of Jupiter taken in infrared light on the night of Aug. 17, 2008 with the Multi-Conjugate Adaptive Optics Demonstrator (MAD) prototype instrument mounted on ESO’s Very Large Telescope.
Reference article: Facts about the fundamental force of gravity.
While gravity’s effects can clearly be seen on the scale of things like planets, stars and galaxies, the force of gravity between everyday objects is extremely difficult to measure.
Gravity is one of the four fundamental forces in the universe, alongside electromagnetism and the strong and weak nuclear forces. Despite being all-pervasive and important for keeping our feet from flying off the Earth, gravity remains, in large part, a puzzle to scientists.
Ancient scholars trying to describe the world came up with their own explanations for why things fall toward the ground. The Greek philosopher Aristotle maintained that objects have a natural tendency to move toward the center of the universe, which he believed to be the middle of the Earth, according to physicist Richard Fitzpatrick from the University of Texas.
But later luminaries dislodged our planet from its primary position in the cosmos. The Polish polymath Nicolas Copernicus realized that the paths of the planets in the sky make much more sense if the sun is the center of the solar system. The British mathematician and physicist Isaac Newton extended Copernicus’ insights and reasoned that, as the sun tugs on the planets, all objects exert a force of attraction on one another.
Where F is the force of gravity, m1 and m2 are the masses of two objects and r is the distance between them. G, the gravitational constant, is a fundamental constant whose value has to be discovered through experiment.
Gravity is the weakest of the fundamental forces. A bar magnet will electromagnetically pull a paper clip upward, overcoming the gravitational force of the entire Earth on the piece of office equipment. Physicists have calculated that gravity is 10^40 (that’s the number 1 followed by 40 zeros) times weaker than electromagnetism, according to PBS’s Nova.
While gravity’s effects can clearly be seen on the scale of things like planets, stars and galaxies, the force of gravity between everyday objects is extremely difficult to measure. In 1798, British physicist Henry Cavendish conducted one of the world’s first high precision experiments to try to precisely determine the value of G, the gravitational constant, as reported in the Proceedings of the National Academy of Science’s Front Matter.
Cavendish built what’s known as a torsion balance, attaching two small lead balls to the ends of a beam suspended horizontally by a thin wire. Near each of the small balls, he placed a large, spherical lead weight. The small lead balls were gravitationally attracted to the heavy lead weights, causing the wire to twist just a tiny bit and allowing him to calculate G.
Remarkably, Cavendish’s estimation for G was only 1% off from its modern-day accepted value of 6.674 × 10^−11 m^3/kg^1 * s^2. Most other universal constants are known to far higher precision but because gravity is so weak, scientists must design incredibly sensitive equipment to try to measure its effects. Thus far, a more precise value of G has eluded their instrumentation.
The German-American physicist Albert Einstein brought about the next revolution in our understanding of gravity. His theory of general relativity showed that gravity arises from the curvature of space-time, meaning that even rays of light, which must follow this curvature, are bent by extremely massive objects.
Einstein’s theories were used to speculate about the existence of black holes — celestial entities with so much mass that not even light can escape from their surfaces. In the vicinity of a black hole, Newton’s law of universal gravitation no longer accurately describes how objects move, but rather Einstein’s tensor field equations take precedence.
Astronomers have since discovered real-life black holes out in space, even managing to snap a detailed photo of the colossal one that lives at the center of our galaxy. Other telescopes have seen black holes’ effects all over the universe.
The application of Newton’s gravitational law to extremely light objects, like people, cells and atoms, remains a bit of an unstudied frontier, according to Minute Physics. Researchers assume that such entities attract one another using the same gravitational rules as planets and stars, but because gravity is so weak, it is difficult to know for sure.
Perhaps, atoms attract one another gravitationally at a rate of one over their distance cubed instead of squared — our current instruments have no way of telling. Novel hidden aspects of reality might be accessible if only we could measure such minute gravitational forces.
A perpetual force of mystery
Gravity perplexes scientists in other ways, too. The Standard Model of particle physics, which describes the actions of almost all known particles and forces, leaves out gravity. While light is carried by a particle called a photon, physicists have no idea if there is an equivalent particle for gravity, which would be called a graviton.
Bringing gravity together in a theoretical framework with quantum mechanics, the other major discovery of the 20th-century physics community, remains an unfinished task. Such a theory of everything, as it’s known, might never be realized.
But gravity has still been used to uncover monumental findings. In the 1960s and 70s, astronomers Vera Rubin and Kent Ford showed that stars at the edges of galaxies were orbiting faster than should be possible. It was almost as if some unseen mass was tugging on them gravitationally, bringing to light a material that we now call dark matter.
In recent years, scientists have also managed to capture another consequence of Einstein’s relativity — gravitational waves emitted when massive objects like neutron stars and black holes rotate around one another. Since 2017, the Laser Interferometer Gravitational-Wave Observatory (LIGO) has opened up a new window to the universe by detecting the exceedingly faint signal of such events.
Einstein’s theory of general relativity has been proven right (again!), thanks to the wobbly dance of a high-speed star swirling around the monster black hole at the center of our galaxy.
Astronomers with the European Southern Observatory (ESO) have been watching that star — named S2 — orbit our local supermassive black hole for 27 years, taking precise measurements of the star’s position and velocity as it swoops around the galactic center, roughly 26,000 light-years from Earth. After watching the star complete nearly two full orbits (each complete orbit takes about 16 years), the researchers concluded that the star does not have a fixed elliptical orbit as predicted by Isaac Newton’s theory of gravity, but rather “dances” around the black hole in a pattern that resembles a rosette drawn using a spirograph.
This sort of orbit, where the star’s point of closest approach moves subtly around the black hole with each orbit, is known as Schwarzschild precession. This wonky sort of precession (or forward movement) was predicted by Einstein more than 100 years ago to describe the effects of an infinitesimally small object orbiting an extraordinarily massive one, the researchers wrote in their new study, published online today (April 16) in the journal Astronomy & Astrophysics.
“Einstein’s general relativity predicts that bound orbits of one object around another are not closed, as in Newtonian gravity, but precess forward in the plane of motion,” study co-author Reinhard Genzel, director of the Max Planck Institute for Extraterrestrial Physics in Germany, said in a statement. “This famous effect — first seen in the orbit of the planet Mercury around the sun — was the first evidence in favor of general relativity. One hundred years later, we have now detected the same effect in the motion of a star orbiting the [black hole] at the center of the Milky Way.”
This is the first time that Schwarzschild precession has been confirmed in a star orbiting a black hole, the researchers wrote in their study. The team identified the loop-de-loops of S2 after making more than 300 observations of the star using several instruments on the ESO’s Very Large Telescope in Chile.
Beyond adding one more log to the proverbial fire of Einstein’s legacy, the new finding could also help researchers make more exact calculations of the types and quantities of matter located at the center of the galaxy, the researchers said.
“Because the S2 measurements follow general relativity so well, we can set stringent limits on how much invisible material, such as distributed dark matter or possible smaller black holes, is present,” study co-authors Guy Perrin of the Paris Observatory and Karine Perraut of France’s University of Grenoble said in the statement. “This is of great interest for understanding the formation and evolution of supermassive black holes.”
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