Astronomy

Are black holes solely responsible for hyper velocity stars?

Are black holes solely responsible for hyper velocity stars?


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I read that the stars orbiting around Sagittarius A* (a.k.a the supermassive black hole located at the heart of the Milky Way) move very fast (many times faster than our Sun moves across the galaxy), and it is believed they have enough speed to wander off. My question is, is any exception to this rule, where somehow some stars may break a stellar speed limit not due to a black hole in their vicinity?


No, black holes are not the only cause of HVSs, although it is thought to be the most common mechanism.

Hyper velocity stars are believed to be caused

  • when binary stars come close enough to a supermassive black hole for one of the pair to be captured while the other star is ejected at high velocity. This appears to the main mechanism for HVSs. See for example this Harvard Smithsonian Center for Astrophysics page, and this University of Utah page.

  • when one star of a binary goes super nova, the second star may be ejected at high velocity. See US 708: Hypervelocity Star Ejected by Supernova Breaks Galactic Speed Record and How do Hypervelocity Stars End up Breaking The Speed Limit?.

There may be other causes, since not all HVSs seem to be explained by these mechanisms. Perhaps some of them are not from this galaxy at all - they may be just passing through.


NASA Blueshift

Last time, we set ourselves up with a nice place to cool off and had a drink or two. And as the evening rolls up, we can lay back with our drinks, dipping our feet in the distant APM 08279+5255 quasar, and watch the universe set. Maybe we can catch a shooting star or two. Of course, I am referring to an actual star shooting across the sky!

Possibly the most studied star that is hurling around the Milky Way is Mira A (Latin for wonderful). Clocking in at around 291,000 miles per hour, Mira A is part of a binary star system (Mira A and Mira B) with a 500-year orbit around its partner, which can be seen in the constellation Cetus from Earth. Mira is also a swollen red giant. A red giant is a small-to-average mass star that is nearing the end of its life. Inside our Sun, a prime example of a small-to-average mass star, nuclear reactions happen constantly as hydrogen fuses into helium. But when the hydrogen runs out in one of these stars (as will happen in the Sun in billions of years), the star will begin to contract, causing immense pressure and energy. This causes the star to expand greatly into a red giant. If Mira A were to magically swap places with the Sun, it would engulf everything out to Mars. What makes Mira A so spectacular, though, is its tail. We’ve actually known about Mira for about 400 years, but it wasn’t until recently that we’ve exposed what is really going on. As Mira travels through space with her companion, she leaves behind mass as she burns fuel. This mass gives off light in ultraviolet wavelengths, and it wasn’t until 2007 when she was viewed with the Galaxy Evolution Explorer (GALEX) that we saw her tail. Hold on to your hats, because it’s a head turner.


Mira had had it. Twinkle, twinkle “LITTLE” star?
Animation of Mira A
Credit: NASA/JPL-Caltech


Mira A’s tail is about 15 light years long – meaning it takes light 15 years to travel from one end to the other. This is 20,000 times longer than the average distance between the Sun and Pluto, by no means a meager distance. And this tail has been growing for 30,000 years. What’s most excellent is that the material deposited by this tail can actually be recycled into new stars, planets and possibly life.


Did somebody get the license plate of that star?
Actual UV image of Mira A
Credit: NASA/JPL-Caltech

And don’t believe for a second that that’s all I have to offer. While Mira is traveling at speeds much faster than other stars (which travel at a comparatively leisurely average speed of 44,738 miles per hour), she is by no means the fastest, and she is still bound to the Milky Way. In 2005, astronomers discovered what they call hyper velocity stars (HVS). To become a HVS, the speed of a star has to exceed the escape velocity of a galaxy which in turn allows it to potentially leave the galaxy. That is, the star has to be going fast enough to overcome all of the gravitational pull that holds it in the galaxy. What?! Let’s scale things back for a moment. Earth has gravity, and that gravity allows us to meander about and not just drift off into space. What’s more important is that if you jump on Earth, you always come back down. You just can’t move fast enough to escape Earth’s loving grip. However, a rocket traveling faster than 25,054 mph (Earth’s escape velocity) can leave this planet and travel to the moon, or beyond. The escape velocity at our current distance from the center of the galaxy is around 1,000 kilometers per second or 2,236,936 miles per hour. So escaping the Milky Way requires a tremendous amount of energy and speed! (Try it. You won’t get far.) So how do these few stars achieve this feat?


There will be a test after the blog.
Credit: NASA, ESA, and A. Feild (STScI)

Astronomers believe that these celestial speeders are the product of binary (or even triple) star systems getting just a little too close to a super-massive black hole – one star gets captured and the other gets sling-shot into the galaxy. It’s a horrible break up. Other theories suggest that a small galaxy collided with ours, and during the collision, unleashed the HVSs upon us. Others still think most of them originated in the Large Magellanic Cloud (one of our neighboring galaxies), and a small group of 675 stars just outside our galaxy are being studied right now with the thought that they might be a cluster of HVSs. There are thought to be roughly 1000 HVSs in the Milky Way alone, which is a small fraction (

0.00001%) of the 100 billion “normal” stars in our galaxy.


And sadly, SDSS J090744.99+024506.8 was never seen again.
Illustration of an expulsion of an HVS from a galaxy
Credit: NASA, ESA, and G. Bacon (STScI)

What’s great about HVSs is that throughout their life they will travel through most of the galaxy. By measuring the motion of these stars, we can get insight into the shape of the Milky Way, and we can also discern information on the presence of dark matter by measuring the trajectory of an HVS when it leaves the galaxy. This trajectory will be affected by the gravitational force of dark matter, and help scientists figure out how much of this matter is hanging around.

Now take a deep breath. I understand that the knowledge of giant stars flying around the galaxy at speeds unfathomable (to anyone not wearing a red onesie) may be a bit unsettling. Just remember that HVSs are a very small percent of stars out there, and as a solar system we aren’t just sitting around waiting for a game of galactic bowling. Our solar system is also running around the galaxy as well (at about about 483,000 miles per hour). Furthermore, the rest of the universe (besides the very few rogue objects) tends to be bound in an orbit (like around the center of our galaxy) and has been moving in this orbit for an incredibly long time (billions of years long), governed by laws of physics as we understand them. So it’s unlikely we would need to do, well, nothing because there wouldn’t be much we could do if something was coming our way. Sleep easy…

So on our adventure through the cosmos, we have found an incredibly large pool of water, an immense vat of ethanol, and now real shooting stars. Let’s strap in and keep going, and maybe we can snatch a diamond, or at least a diamond planet. As always, leave a comment or two, and maybe we can make a detour.


#1 | It’s All About the Escape Velocity

In order to escape the gravitational pull of Earth, a rocket must travel at a minimum speed of around 11 kilometers (seven miles) per second. This escape velocity is determined by the mass of the planet, as well as it’s radius. If the Earth were more massive (and the same size), or if our planet had it’s current mass stuffed into a smaller ball, its escape velocity would be greater than it is under current conditions. Once an object shrinks to its Schwarzschild radius (a size dependent on the mass of the shrinking body), the escape velocity from its surface would reach the speed of light, closing the body off from the rest of the Universe.

If one were to shrink the Earth down to the size of a small marble, the escape velocity of our planet would increase to that of the speed of light. Since no object can travel this quickly (thanks for the insight, Einstein!), not even light could escape the surface of our diminutive world, leaving The Earth as a black hole. Or, if you were to assemble a sphere of water having a radius of 40 astronomical units (roughly the size of the orbit of Pluto), its mass would be so great, the escape velocity of the body would be greater than the speed of light, creating a (much larger) black hole.


Astronomers find closest black hole to Earth, hints of more

Meet your new but shy galactic neighbor: A black hole left over from the death of a fleeting young star.

European astronomers have found the closest black hole to Earth yet, so near that the two stars dancing with it can be seen by the naked eye.

Of course, close is relative on the galactic scale. This black hole is about 1,000 light-years away and each light-year is 5.9 trillion miles (9.5 trillion kilometers). But in terms of the cosmos and even the galaxy, it is in our neighborhood, said European Southern Observatory astronomer Thomas Rivinius, who led the study published Wednesday in the journal Astronomy & Astrophysics.

The previous closest black hole is probably about three times further, about 3,200 light-years, he said.

The discovery of a closer black hole, which is in the constellation Telescopium in the Southern Hemisphere, hints that there are more of these out there. Astronomers theorize there are between 100 million to 1 billion of these small but dense objects in the Milky Way.

The trouble is we can’t see them. Nothing, not even light, escapes a black hole’s gravity. Usually, scientists can only spot them when they're gobbling up sections of a partner star or something else falling into them. Astronomers think most black holes, including this newly discovered one, don't have anything close enough to swallow. So they go undetected.

Astronomers found this one because of the unusual orbit of a star. The new black hole is part of what used to be a three-star dance in a system called HR6819. The two remaining super-hot stars aren't close enough to be sucked in, but the inner star's orbit is warped.

Using a telescope in Chile, they confirmed that there was something about four or five times the mass of our sun pulling on the inner star. It could only be a black hole, they concluded.

Outside astronomers said that makes sense.

“It will motivate additional searches among bright, relatively nearby stars,” said Ohio State University astronomer Todd Thompson, who wasn’t part of the research.

Like most of these type of black holes this one is tiny, maybe 25 miles (40 kilometers) in diameter.

“Washington, D.C. would quite easily fit into the black hole, and once it went in it, would never come back,” said astronomer Dietrich Baade, a study co-author.

These are young hot stars compared to our 4.6 billion-year-old sun. They’re maybe 140 million years old, but at 26,000 degrees F (15,000 degrees C) they are three times hotter than the sun, Rivinius said. About 15 million years ago, one of those stars got too big and too hot and went supernova, turning into the black hole in a violent process, he said.

“It is most likely that there are black holes much closer than this one,” said Avi Loeb, director of Harvard’s Black Hole Initiative, who wasn’t part of the study. “If you find an ant while scanning a tiny fraction of your kitchen, you know there must be many more out there.”

Follow Seth Borenstein on Twitter: @borenbears

The Associated Press Health and Science Department receives support from the Howard Hughes Medical Institute’s Department of Science Education. The AP is solely responsible for all content.


By now, you’ve probably seen the photo of Virgo A, the supermassive black hole ringed by an orange glow at the center of the Messier 87 (M87) galaxy. When news first broke of Virgo A’s capture by telescope cameras, a 29-year-old female scientist, Katie Bouman—a Taurus (May 9, 1989)—was credited with heading a team that created an algorithm that made the image possible. In truth, no one person is solely responsible for this Herculean effort. But we have little doubt that mad scientist Uranus, who entered her Katie Bouman’s sign on March 6, has its fingerprints on this. If nothing else, the widely circulated photos of Dr. Bouman covering her mouth with surprise and awe at first glimpsing the photos is a shout out to the amazing women in the S.T.E.M. fields—and hopefully a clarion call for more women to move into these historically male-dominated industries!

What makes the April 10 discovery a landmark is that we can actually see the black hole. That said, we’ve been talking about black holes since 1916 (and even earlier), when Pisces Albert Einstein introduced the General Theory of Relativity. Up until this point, however, we had to rely on complex equations to confirm their existence rather than any visual cues. But now…voila!

Once an interstellar object is on our radar, both astronomers and astrologers put on the proverbial lab coats and get to work. Spiritual stargazers have actually been interpreting Virgo A—along with more than 50 other black holes—for a while. In fact, some hardcore astrogeeks out there, including deep space astrologer Phillip Sedgewick and Alex Miller, have authored interpretive systems for understanding how black holes impact our charts.

In The Black Hole Book, Alex Miller lists the zodiac position 57 of these cosmic phenomena, each of which has a location on the 360º horoscopic wheel. One of the more well-known black holes is the one in our own Galactic Center, the middle of our Milky Way galaxy. This one is called Sagittarius A and is currently stationed between 27º and 28º Sagittarius on the Western zodiac wheel. The now-visible Virgo A, which lives inside the Virgo constellation, is currently moving near 1º Libra.

Note: It’s important to note that modern day (Hellenic) astrology is not based on the position of the constellations. Although these clusters were once place-markers for each of the 30º slices of the zodiac wheel, they have shifted over time. More on that in the article we wrote debunking NASA’s 2016 claim that your zodiac sign has changed.

Unlike planets, black holes do not move along an orbital path. They are collapsed stars with an intense gravitational force that sucks in matter so densely that no light can escape. Black holes do drift and shift in space over time, but they are considered “galactic points,” because they have a more fixed placement in the sky. Sagittarius A, for example, takes 72 years to move a single degree.

So, what does this mean for us down here on Earth? There are two ways to look at black holes in astrology: first, how they impact all of us universally, and secondly how they mesh with your individual sign and birth chart.

On the broadest note, black holes are unseen forces that pull us into their fields. They yank us into the shadows and make us stare down our addictions, compulsions and vices. They represent the patterns we find difficult to break…and the innate frequencies (like radiowaves) that we are tuned into as humans, often unconsciously. They also reveal our hidden powers, the things that make us so magnetic that people want more. These are the gifts that we can’t deny, even if we’d rather not pick up the sword for that hero’s journey.

If a black hole is positioned near a planet in your birth chart, it may have a lot of pull on that part of your personality. (See table below.) Turns out Black Hole Sun is not just the name of a 90s Chris Cornell song. People who were born with their Sun within three degrees of a black hole on the zodiac wheel are called “Black Hole Sun personalities,” among astrologers.

To see if Virgo A may be impacting you personally, run a natal chart for yourself here. Then, check to see. Do you have any planets close (within 3º) to its current placement of 1º Libra—that would be 28º-29º Virgo or 0º – 4º Libra?

If you know your time of birth and are able to calculate houses, you can see what house Virgo A falls into. In the sample chart above, it lands at the end of the 8th house, where 1º Libra is located. The house placement of the black hole may reveal an area of life where you could use some transformation. Tali talks about this in the video above. (Not sure what that means? Watch our video on how to interpret your chart!)

If Virgo A (or any black hole) happens to be placed within three degrees of these planets, you may feel an extra charge as you work through your subconscious blocks. Below is a table of what you might transform if any of these planets sit near 1º Libra in your chart. (Or, for you advanced astrogeeks out there, is aspected to it in a trine, square, etc.)

If this planet is conjunct (or aspected to) a black hole, this may be a struggle and a mission in life:
Sun
: Figuring out your sense of self or purpose in the world without outside validation

Moon: Gaining control over your own emotions and desires

Mercury: Communicating effectively so as not to leave people feeling manipulated or pressured

Venus: Addictive romances, using seductive powers in a healthy way

Mars: Navigating conflict without starting battles finding healthy outlets for aggression

Jupiter: Gambling addictions, struggles with staying in one place (but starting fires and not putting them out)

Saturn: Feeling overly burdened by responsibility an addiction to power and control

Uranus: Experimenting with danger, figuring out how to live on the edge without being destructive

Neptune: Struggle to set boundaries martyr complex

Pluto: Seeing life as a constant power struggle, attracting people with major secrets and skeletons in their closets


Black hole

If you really want some insight there have been a couple of programs on TV about Black Holes and "The Black Hole War" based on arguments between the two leading Physicists on the Planet: Steven Hawking and Leonard Susskind. There is also a Book of the same name written by Leonard Susskind.

#27 SteveG

At the center of a black hole, there is a microscopic point at which physics says the mass is infinite - yes infinite! How can that be?

Yes, the words singularity, dark matter and dark energy are all "place-holders", for things we do not fully understand.

#28 CosmoSat

Its just a theory. and there might be a "hole" in the theory itself.

In the scientific community, the word "theory" does not mean "hunch" or "speculation". It means "scientific understanding" or "law of nature".

General relativity, which describes black holes as objects which have an escape velocity greater than light, is the modern description of gravity that passes all the detailed tests it has been challenged to explain.

Black holes are *not* a feature of general relativity they are a feature of all descriptions of gravity. The first mathematical description of a black hole was written down using Newtonian gravity in 1783 by the Rev. John Michell.

Ok..guess that helped fix a "hole" in my understanding of things..

Not really. I said that simply because I didnt wanted to argue any further on this topic. but then others hve.

#29 David Knisely

Well I was just wondering because my autostar controller has a black hole listing. I was just wondering what I might see if I look there. The skies have been bad here. Maybe soon they'll clear up.

#30 Al Canarelli

For those who want to see a black hole - or at least visualize one - look at any galaxy with your telescope. At the center of each is a massive, or a 'supermassive' black hole, around which the millions of stars in each galaxy orbit. There's one at the center of our Milky Way galaxy, and another at the center of nearby Andromeda (M31).
============================================================
You can't really see a black hole so it's difficult to visualize something you can't see. In many of the galaxies scientists have studied closely, they make the assumption that a supermassive black hole is located close to the center. They base this assumption on the effect the gravity of this huge black hole has on some stars. These stars appear to be orbiting something huge, but there is nothing visible. The velocity of these stars may be far greater than a million miles/hour, so we know that there is a massive gravity force swinging these stars around at such fantastic speeds. This could only be a black hole and the scientists project these findings to all galaxies. Therefore, all galaxies are driven by a supermassive black hole which resides at its center.

Now here comes the wierd stuff.

The black hole at the center of the galaxy, regardless of its size and power is too far from the stars located at a point midway in the galaxy to the outer portion of the galaxy to have any influence on their movement. Therefore, the stars in the galaxy DO NOT orbit the force created by a black hole, even if there is one there, as it's just too far away. So what makes stars orbit around the galaxy? That's another "I DON'T KNOW'. So to explain that, the scientists call on another invented concept. DARK ENERGY.
Thought you had enough with a black hole that you can't see, or dark matter that you can't see? Now you can add dark energy into the mix.

#31 E_Look

#32 David Knisely

The black hole at the center of the galaxy, regardless of its size and power is too far from the stars located at a point midway in the galaxy to the outer portion of the galaxy to have any influence on their movement. Therefore, the stars in the galaxy DO NOT orbit the force created by a black hole, even if there is one there, as it's just too far away. So what makes stars orbit around the galaxy? That's another "I DON'T KNOW'. So to explain that, the scientists call on another invented concept. DARK ENERGY.
Thought you had enough with a black hole that you can't see, or dark matter that you can't see? Now you can add dark energy into the mix.

#33 SteveG

#34 Andrew B.

As I understand it, and in simple terms, when a supermassive star reaches the end of its life by burning most of its available hydrogen, it detonates in a supernova explosion and the resulting collapse results in a black hole. There also appear to be large black holes at the centers of most galaxies which may be residual from the original gravitational accretion as the galaxies formed early in the history of the universe following the Big Bang.

#35 Jim Nelson

#36 brianb11213

"Hypernova" is an unofficial term.

Meanwhile we have three mechanisms involved in SN:

1) accretion from a nearby star

It is at least theoretically possible for (2) & (3) to result in the production of a black hole though this need not always occur.

#37 Kevdog

#38 csrlice12

#39 JLovell

I've seen Buggs Bunny, Roadrunner, etc do that with a hole, but I think you are right. Ringo is the only HUMAN I know of to have a hole in his pocket!


As far as black holes evaporating, there is Hawking radiation, reducing the mass by the famous equation E = mc^2. There is also quantum tunneling, where particles can penetrate impenetrable barriers and escape "boxes" they don't have enough energy to escape.

#40 JoeM101

While many main stream "scientists" claim that black holes are the collapsed remnants of dead stars, i put forward to you a more plausible theory that some cosmologists and plasma physicists are slowly but surely bringing to light..
(noteables: I. Velikovsky, K. Birkeland, I. Langmuir, H. Alfven, H. Arp, A. Perrat)

Alfven contended that the energetic activity ascribed to "black holes" could be better explained by electromagnetic forces and that these forces shape galaxies..

"Today's scientists have substituted mathematics for experiments, and they wander off through equation after equation, and eventually build a structure which has no relation to reality:" - Nikola Tesla

hec, mathematicians proved that heavier than air flight was impossible! Don't get me wrong, Math is critical and a vital tool for science, but let's not put the cart before the horse.

gravity is an infinitesimally week force and does not allow for credible explanations of what is really going on out there.. the big bang, black holes and galactic formation has been made more esoteric than ever by mathematicians who now dominate the realm of cosmology and spread all kinds of assumptions and fudge factors to validate absurd theories. dark matter, dark energy, these are what we in the academic world call "major" fudge factors.. how is it that 70% of the universe is comprised of dark energy (credited for the expansion of space, another questionable theory) and dark matter (invisible, undetectable and not made of "normal" stuff) accounts for 28% of the universe and only 2% left for "normal" matter??

1- expansion (inflation theory) - based on Hubble's law that the red-shift measured in galaxies is directly proportional to their distances, hence the further a galaxy is the faster it's moving away, not so, there have been many peculiar objects that directly contradict this assumption, most notably NGC-7603 that has a red-shift of 8700Km/sec while a quasar connected to the galaxy via a filament has a red-shift of 16800km/sec, and recent discoveries of 2 more quasars within the connecting filament have red-shifts of 117000km/sec and 72000km/sec. this is completely contrary to currently accepted theories. there are too many examples to cite but i leave you all with this.. would Hubble have come to the same conclusions if he had measured quasi-stellar red-shifts? i dont think so, if not for Hubble's law, there is no need to run the clock back into a singularity, therefore, no big bang.. let alone the CMB (cosmic background radiation) temperature measurements which do not coincide with big bang predictions of 50 Kelvin, CMB is 3K, more akin to a stable non-expanding universe (predicted almost to the decimal place in a stable, non-expanding universe model)

a plasma universe.. 99.99% of all we see in the universe can be reproduced in labs and scaled to cosmological magnitudes when using plasma physics to test and explain it all

electromagnetism can explain just about everything we observe in the universe today without the need for dark stuff.. and EM is 39 magnitudes, that's 1 with 39 zeros, stronger than gravity, and is more plausible than the gravitational model. I personally think gravity is a weak component of the electromagnetic force and not a separate force at all as is currently theorized.. that is more likely the case than a dark theory, and not anywhere as far out there. Recently scientists at CERN have discovered that the weak nuclear force and strong nuclear forces actually "look and feel" very much like the electromagnetic force at higher energy states.. now there's a unified theory if i ever heard one.. all forces are fundamentally EM.

Einstein himself was quoted to say that not even he understood relativity after it was invaded by mathematicians, nor did he believe that black holes were possible. he was also quoted to say that relativity left him feeling like something was missing.. let's face it quantum physics and relativity are completely disjointed. Plasma physics can account for the very large and the very small. a "unified" theory.

do yourselves a favor, research it yourselves and draw your own conclusions. Cosmology today has been made to be a realm of funky math. how can it be so?

big bang - i don't think so, electric universe - more likely..

just to clarify a point made earlier by other posters to this thread, main stream astrophysics postulates that a star having a mass of 5 to 8 solar masses can gravitationaly collapse into a "black hole" or neutron star (type 2 SN), depending on mass, once it begins to produce iron, not when it runs out of hydrogen as some have stated (a sun type star would theoretically form a white dwarf when it runs out of helium, it would form a red giant once it ran out of hydrogen) if a white dwarf star "sucked" matter off of a companion star and reached 1.4 times the mass of our sun you'd get the classical type 1a supernova (standard candle used for measure astronomical distances).. according to the chandrasekhar limit, the more massive stars (5 to 8 solar masses) would have long since (according to the gravitational model) eaten up all their hydrogen, helium, etc and are at the end stage where the final element created by the fusion process is iron, which absorbs energy, does not produce any as other fusion reactions do, therefor, collapse occurs in mere seconds whereby outer material rebounds off the inner and causes a supernova explosion or a hypernova if the mass is great enough.. this scenario is mathematically plausible but unlikely when observations do not support the predictions. a stars' surface temperature is lower than its coronal temp by several million degrees (predicted by plasma physics and proven by observation and spetral analysis of our sun), and sun spots prove to be even cooler than the surface. this is not what you would expect in a fusion reactor, one last point, if light could not escape a black hole, why would x-rays or gamma rays, they are all part of the same electromagnetic spectrum, just differing wavelengths. G would have to win over EM. hence the requirement for infinite gravity at the singularity, which is supported only by fuzzy math.

someone said there's a hole in the theory and a response was given about how theory doesn't mean hunch, imho, when 96 to 98% of the universe "according to the gravitational model" is stuff we cannot observe, measure or even begin to understand, only by the virtue of math made to fit the model, i'd say hunch is about all it could be called, i would even go as far as calling it simple conjecture.

here's a vid for you: Plasma Physics' Answers to the New Cosmological Questions by Dr. Donald E. Scott - Full Video, and another Thunderbolts Of The Gods or look up electric universe or plasma universe, i'm sure the inquiring mind will be set ablaze with new perspectives and possibilities.


Planets Could Travel Along with Rogue ‘Hypervelocity’ Stars, Spreading Life Throughout the Universe

Back in 1988, astronomer Jack Hills predicted a type of “rogue”star might exist that is not bound to any particular galaxy. These stars, he reasoned, were periodically ejected from their host galaxy by some sort of mechanism to begin traveling through interstellar space.

Since that time, astronomers have made numerous discoveries that indicate these rogue, traveling stars indeed do exist, and far from being an occasional phenomenon, they are actually quite common. What’s more, some of these stars were found to be traveling at extremely high speeds, leading to the designation of hypervelocity stars (HVS).

And now, in a series of papers that published in arXiv Astrophysics, two Harvard researchers have argued that some of these stars may be traveling close to the speed of light. Known as semi-relativistic hypervelocity stars (SHS), these fast-movers are apparently caused by galactic mergers, where the gravitational effect is so strong that it fling stars out of a galaxy entirely. These stars, the researchers say, may have the potential to spread life throughout the Universe.

This finding comes on the heels of two other major announcements. The first occurred in early November when a paper published in the Astrophysical Journal reported that as many as 200 billion rogue stars have been detected in a cluster of galaxies some 4 billion light years away. These observations were made by the Hubble Space Telescope’s Frontier Fields program, which made ultra-deep multiwavelength observations of the Abell 2744 galaxy cluster.

This was followed by a study published in Science, where an international team of astronomers claimed that as many as half the stars in the entire universe live outside of galaxies.

Image of a moving star captured by the ESO Very Large Telescope, believed to have been ejected from the Large Magellanic Cloud. Credit: ESO

However, the recent observations made by Abraham Loeb and James Guillochon of Harvard University are arguably the most significant yet concerning these rogue celestial bodies. According to their research papers, these stars may also play a role in spreading life beyond the boundaries of their host galaxies.

In their first paper, the researchers trace these stars to galaxy mergers, which presumably lead to the formation of massive black hole binaries in their centers. According to their calculations, these supermassive black holes (SMBH) will occasionally slingshot stars to semi-relativistic speeds.

“We predict the existence of a new population of stars coasting through the Universe at nearly the speed of light,” Loeb told Universe Today via email. “The stars are ejected by slingshots made of pairs of massive black holes which form during mergers of galaxies.”

These findings have further reinforced that massive compact bodies, widely known as a supermassive black holes (SMBH), exist at the center of galaxies. Here, the fastest known stars exist, orbiting the SMBH and accelerating up to speeds of 10,000 km per second (3 percent the speed of light).

According to Leob and Guillochon, however, those that are ejected as a result of galactic mergers are accelerated to anywhere from one-tenth to one-third the speed of light (roughly 30,000 – 100,000 km per second).

Image of a hypervelocity star found in data from the Sloan Digital Sky Survey. Credit: Vanderbilt University

Observing these semi-relativistic stars could tell us much about the distant cosmos, according to the Harvard researchers. Compared to conventional research, which relied on subatomic particles like photons, neutrinos, and cosmic rays from distant galaxies, studying ejected stars offers numerous advantages.

“Traditionally, cosmologists used light to study the Universe but objects moving less than the speed of light offer new possibilities,” said Loeb. “For example, stars moving at different speeds allow us to probe a distant source galaxy at different look-back times (since they must have been ejected at different times in order to reach us today), in difference from photons that give us just one snapshot of the galaxy.”

In their second paper, the researchers calculate that there are roughly a trillion of these stars out there to be studied. And given that these stars were detected thanks to the Spitzer Space Telescope, it is likely that future generations will be able to study them using more advanced equipment.

All-sky infrared surveys could locate thousands of these stars speeding through the cosmos. And spectrographic analysis could tell us much about the galaxies they came from.

But how could these fast moving stars be capable of spreading life throughout the cosmos?

The Theory of Panspermia argues that life is distributed throughout the universe by celestial objects. Credit: NASA/Jenny Mottar

“Tightly bound planets can join the stars for the ride,” said Loeb. “The fastest stars traverse billions of light years through the universe, offering a thrilling cosmic journey for extra-terrestrial civilizations. In the past, astronomers considered the possibility of transferring life between planets within the solar system and maybe through our Milky Way galaxy. But this newly predicted population of stars can transport life between galaxies across the entire universe.”

The possibility that traveling stars and planets could have been responsible for the spread of life throughout the universe is likely to have implications as a potential addition to the Theory of Panspermia, which states that life exists throughout the universe and is spread by meteorites, comets, asteroids.

But Loeb told Universe Today that a traveling planetary system could have potential uses for our species someday.

“Our descendants might contemplate boarding a related planetary system once the Milky Way will merge with its sister galaxy, Andromeda, in a few billion years,” he said.


Black hole masses in active galactic nuclei

The masses of supermassive black holes, key to many cosmological studies, are highly uncertain beyond our local Universe. The main challenge is to establish the spatial and kinematic structure of the broad-line emitting gas in active galactic nuclei.

The scientific community’s interest in supermassive black holes (SMBHs) soared after the discovery of the empirical relationship between the mass of the central SMBH and the velocity dispersion of the stars in the bulges of local galaxies, the MBHσ relation 1,2 , roughly 20 years ago. This result strongly implies a co-evolution of SMBHs and their host galaxies. How massive black holes grow and interact with their environment depends, for a given gas content, critically on the central gravitational potential of the galaxy but also on the mass of the SMBH 3 , since it sets the scale of the energy ‘feedback’ that the SMBH can muster. For a thorough understanding of the cosmic role of SMBHs, we need more accurate mass determinations at all cosmic distances than current methods provide 1,4 .


Types Edit

    (Great Annihilator), 340 ly from Sgr A*[2] /IL Lupi (currently thought to be the closest to Earth, at about 3,000 light years, with a mass roughly estimated to be 11.0 ± 1.9 times the mass of Sun) [citation needed] A candidate stellar mass black hole outside of the Local Group. [3] (smallest black hole yet discovered) [citation needed] /V1033 Sco (at one time considered the smallest black hole known) [4] /GU Mus /V1487 Aql /QZ Vul /V821 Ara (triple star system visible with unaided eye, with closest black hole as of May 2020) [5] (candidate smallest stellar black hole) [6][7] (name of both a galactic B-type star, [8] as well as the name of a very closely associated over-massive stellar-mass black hole. [9] ) (most massive stellar-mass black hole known, not counting GW black holes) [10] (in NGC 1536) /KV UMa /V381 Nor (at one time considered the smallest black hole known) [4] /V4641 Sgr

Black holes detected by gravitational wave signals Edit

As of February 2019 [update] , 10 mergers of binary black holes have been observed. In each case two black holes merged to a larger black hole. In addition, one neutron star merger has been observed (GW170817), forming a black hole. In addition, over 30 alerts have been issued since April 2019, of black hole merger candidates.

Binary black holes Edit

    core black holes — a pair of supermassive blackholes at the centre of this galaxy [11] – the first binary-cored quasar — a pair of supermassive blackholes at the core of this quasar [12][13]

In addition, the signal of several binary black holes merging into a single black hole and in so doing producing gravitational waves have been observed by the LIGO instrument. These are listed above in the section Black holes detected by gravitational wave signals.


What makes hypervelocity stars move so fast?

The exact origins of hypervelocity stars is unknown, but many existing theories suggest interaction with gravitationally strong objects is the cause. It is believed that a strong candidate for the origin of these objects is binary star systems interacting with supermassive black holes in the centre of distant galaxies from ours.

As the binary system falls toward the black hole it is believed that one of the stars will be captured by the black hole and the other will be split from the system, retaining the high velocity gained. Other theories suggest companion stars can be ejected following supernova explosions in binary systems. Many of these theories fit with current observations but further research needs to be done.

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