New ‘Einstein Ring’ Discovered By Dark Energy Camera

The "Canarias Einstein Ring." The green-blue ring is the source galaxy, the red one in the middle is the lens galaxy. The lens galaxy has such strong gravity, that it distorts the light from the source galaxy into a ring. Because the two galaxies are aligned, the source galaxy appears almost circular. Image: This composite image is made up from several images taken with the DECam camera on the Blanco 4m telescope at the Cerro Tololo Observatory in Chile.

A rare object called an Einstein Ring has been discovered by a team in the Stellar Populations group at the Instituto de Astrofísica de Canarias (IAC) in Spain. An Einstein Ring is a specific type of gravitational lensing.

Einstein’s Theory of General Relativity predicted the phenomena of gravitational lensing. Gravitational lensing tells us that instead of travelling in a straight line, light from a source can be bent by a massive object, like a black hole or a galaxy, which itself bends space time.

Einstein’s General Relativity was published in 1915, but a few years before that, in 1912, Einstein predicted the bending of light. Russian physicist Orest Chwolson was the first to mention the ring effect in scientific literature in 1924, which is why the rings are also called Einstein-Chwolson rings.

Gravitational lensing is fairly well-known, and many gravitational lenses have been observed. Einstein rings are rarer, because the observer, source, and lens all have to be aligned. Einstein himself thought that one would never be observed at all. “Of course, there is no hope of observing this phenomenon directly,” Einstein wrote in 1936.

The team behind the recent discovery was led by PhD student Margherita Bettinelli at the University of La Laguna, and Antonio Aparicio and Sebastian Hidalgo of the Stellar Populations group at the Instituto de Astrofísica de Canarias (IAC) in Spain. Because of the rarity of these objects, and the strong scientific interest in them, this one was given a name: The Canarias Einstein Ring.

There are three components to an Einstein Ring. The first is the observer, which in this case means telescopes here on Earth. The second is the lens galaxy, a massive galaxy with enormous gravity. This gravity warps space-time so that not only are objects drawn to it, but light itself is forced to travel along a curved path. The lens lies between Earth and the third component, the source galaxy. The light from the source galaxy is bent into a ring form by the power of the lens galaxy.

When all three components are aligned precisely, which is very rare, the light from the source galaxy is formed into a circle with the lens galaxy right in the centre. The circle won’t be perfect; it will have irregularities that reflect irregularities in the gravitational force of the lens galaxy.

Another Einstein Ring. This one is named LRG 3-757. This one was discovered by the Sloan Digital Sky Survey, but this image was captured by Hubble's Wide Field Camera 3. Image: NASA/Hubble/ESA
Another Einstein Ring. This one is named LRG 3-757. This one was discovered by the Sloan Digital Sky Survey, but this image was captured by Hubble’s Wide Field Camera 3. Image: NASA/Hubble/ESA

The objects are more than just pretty artifacts of nature. They can tell scientists things about the nature of the lens galaxy. Antonio Aparicio, one of the IAC astrophysicists involved in the research said, “Studying these phenomena gives us especially relevant information about the composition of the source galaxy, and also about the structure of the gravitational field and of the dark matter in the lens galaxy.”

Looking at these objects is like looking back in time, too. The source galaxy is 10 billion light years from Earth. Expansion of the Universe means that the light has taken 8.5 billion light years to reach us. That’s why the ring is blue; that long ago, the source galaxy was young, full of hot blue stars.

The lens itself is much closer to us, but still very distant. It’s 6 billion light years away. Star formation in that galaxy likely came to a halt, and its stellar population is now old.

The discovery of the Canarias Einstein Ring was a happy accident. Bettinelli was pouring over data from what’s known as the Dark Energy Camera (DECam) of the 4m Blanco Telescope at the Cerro Tololo Observatory, in Chile. She was studying the stellar population of the Sculptor dwarf galaxy for her PhD when the Einstein Ring caught her attention. Other members of the Stellar Population Group then used OSIRIS spectrograph on the Gran Telescopio CANARIAS (GTC) to observe and analyze it further.

Next Time You’re Late To Work, Blame Dark Energy!

Illustration of the Big Bang Theory

Ever since Lemaitre and Hubble’s first proposed it in the 1920s, scientists and astronomers have been aware that the Universe is expanding. And from these observations, cosmological theories like the Big Bang Theory and the “Arrow of Time” emerged. Whereas the former addresses the origins and evolution of our Universe, the latter argues that the flow of time in one-direction and is linked to the expansion of space.

For many years, scientists have been trying to ascertain why this is. Why does time flow forwards, but not backwards? According to new study produced by a research team from the Yerevan Institute of Physics and Yerevan State University in Armenia, the influence of dark energy may be the reason for the forward-flow of time, which may make one-directional time a permanent feature of our universe.

Today, theories like the Arrow of Time and the expansion of the universe are considered fundamental facts about the Universe. Between measuring time with atomic clocks, observing the red shift of galaxies, and created detailed 3D maps that show the evolution of our Universe over the course of billions of years, one can see how time and the expansion of space are joined at the hip.

Artist's impression of the influence gravity has on space time. Credit: space.com
Artist’s impression of the influence gravity has on space time. Credit: space.com

The question of why this is the case though is one that has continued to frustrate physicists. Certain fundamental forces, like gravity, are not governed by time. In fact, one could argue without difficulty that Newton’s Laws of Motion and quantum mechanics work the same forwards or backwards. But when it comes to things on the grand scale like the behavior of planets, stars, and entire galaxies, everything seems to come down to the Second Law of Thermodynamics.

This law, which states that the total chaos (aka. entropy) of an isolated system always increases over time, the direction in which time moves is crucial and non-negotiable, has come to be accepted as the basis for the Arrow of Time. In the past, some have ventured that if the Universe began to contract, time itself would begin to flow backwards. However, since the 1990s and the observation that the Universe has been expanding at an accelerating rate, scientists have come to doubt that this.

If, in fact, the Universe is being driven to greater rates of expansion – the predominant explanation is that “Dark Energy” is what is driving it – then the flow of time will never cease being one way. Taking this logic a step further, two Armenian researchers – Armen E. Allahverdyan of the Center for Cosmology and Astrophysics at the Yerevan Institute of Physics and Vahagn G. Gurzadyan of Yerevan State University – argue that dark energy is the reason why time always moves forward.

In their paper, titled “Time Arrow is Influenced by the Dark Energy“, they argue that dark energy accelerating the expansion of the universe supports the asymmetrical nature of time. Often referred to as the “cosmological constant” – referring to Einstein’s original theory about a force which held back gravity to achieve a static universe – dark energy is now seen as a “positive” constant, pushing the Universe forward, rather than holding it back.

Diagram showing the Lambda-CBR universe, from the Big Bang to the the current era. Credit: Alex Mittelmann/Coldcreation
Diagram showing the Lambda-CBR universe, from the Big Bang to the the current era. Credit: Alex Mittelmann/Coldcreation

To test their theory, Allahverdyan and Gurzadyan used a large scale scenario involving gravity and mass – a planet with increasing mass orbiting a star. What they found was that if dark energy had a value of 0 (which is what physicists thought before the 1990s), or if gravity were responsible for pulling space together, the planet would simply orbit the star without any indication as to whether it was moving forwards or backwards in time.

But assuming that the value of dark energy is a positive (as all the evidence we’ve seen suggests) then the planet would eventually be thrown clear of the star. Running this scenario forward, the planet is expelled because of its increasing mass; whereas when it is run backwards, the planet closes in on the star and is captured by it’s gravity.

In other words, the presence of dark energy in this scenario was the difference between having an “arrow of time” and not having one. Without dark energy, there is no time, and hence no way to tell the difference between past, present and future, or whether things are running in a forward direction or backwards.

But of course, Allahverdyan and Gurzadyan were also sure to note in their study that this is a limited test and doesn’t answer all of the burning questions. “We also note that the mechanism cannot (and should not) explain all occurrences of the thermodynamic arrow,” they said. “However, note that even when the dark energy (cosmological constant) does not dominate the mean density (early universe or today’s laboratory scale), it still exists.”

Limited or not, this research is representative of some exciting new steps that astrophysicists have been taking of late. This involves not only questioning the origins of dark energy and the expansion force it creates, but also questioning its implication in basic physics. In so doing, researchers may finally be able to answer the age-old question about why time exists, and whether or not it can be manipulated (i.e. time travel!)

Further Reading: Physical Review E

James Webb Space Telescope Takes The Gloves Off

Behold, the mighty primary mirror of the James Webb Space Telescope, in all its gleaming glory! Image: NASA/Chris Gunn

The James Webb Space Telescope (JWST) isn’t even operational yet, and already its gleaming golden mirror has reached iconic status. It’s segmented mirror is reminiscent of an insect eye, and once that eye is unfolded at its eventual stationary location at L2, the JWST will give humanity its best view of the Universe yet. Now, NASA has unveiled the JWST’s mirrors in a clean room at the Goddard Space Flight Centre, giving us a great look at what the telescope will look like when it’s operational.

Even if you didn’t know anything about the JWST, its capabilities, or its torturous path to finally being built, you would still look at it and be impressed. It’s obviously a highly technological, highly engineered, one of a kind object. In fact, you could be forgiven for mistaking it for a piece of modern art. (I’ve seen less appealing modern art, have you?)

The fact that the JWST will outperform its predecessor, the Hubble, is a well-known fact. After all, the Hubble is pretty long in the tooth now. But how exactly it will outperform the Hubble, and what the JWST’s mission objectives are, is less well-known. It’s worth it to take a look at the objectives of the JWST, again, and re-visit the enthusiasm that has surrounded this mission since its inception.

The James Webb Space Telescope in the clean room at the Goddard Space Flight Center. Image: NASA/Chris Gunn
The James Webb Space Telescope in the clean room at the Goddard Space Flight Center. Image: NASA/Chris Gunn

NASA groups JWST’s science objectives into four areas:

  • infrared vision that acts like a time-machine, giving us a look at the first stars and galaxies to form in the Universe, over 13 billion years ago.
  • a comparative study of the stately spiral and elliptical galaxies of our age with the faintest, earliest galaxies to form in the Universe.
  • a probing gaze through clouds of dust, to watch stars and planets being born.
  • a look at extrasolar planets, and their atmospheres, keeping an eye out for biomarkers.

That is an impressive list, even in an age where people take technological and scientific progress for granted. But alongside these noble objectives, there will no doubt be some surprises. Guessing what those surprises might be is a bit of a fool’s errand, but this is the internet, so let’s dare to be foolish.

We have an idea that abiogenesis on Earth happened fairly quickly, but we have nothing to compare it to. Will we learn enough about exoplanets and their atmospheres to shed some light on conditions needed for life to happen? It’s a stretch, but who knows?

We have an understanding of the expansion of the Universe, and it’s backed up by pretty solid evidence. Will we learn something surprising about this? Or something that sheds some light on Dark Matter and Dark Energy, and their role in the early Universe?

Or will there be surprising findings in the area of planetary and stellar formation? The capability to look deeply into dust clouds should certainly reveal things previously unseen, but only guessed at.

Of course, not everything needs to be surprising to be exciting. Evidence that supports and fine tunes current theories is also intriguing. And the James Webb should deliver a boatload of evidence.

There’s no question that the JWST will outdo the Hubble in the science department. But for a generation or two of people, the Hubble will always have a special place. It drew many of us in, with its breathtaking pictures of nebulae and other objects, its famous Deep Field study, and, of course, its science. It was probably the first telescope to gain celebrity status.

The James Webb will probably never gain the social status that the Hubble gained. It’s kind of like the Beatles, there can only be one ‘first of its kind.’ But the JWST will be much more powerful, and will reveal to us a lot that has been hidden.

The JWST will be a grand technological accomplishment, if all goes well and it makes it to L2 and is fully functional. Its ability to look deeply into dust clouds, and to look back in time, to the early days of the Universe, make it a potent scientific tool.

And if engineering can figure out a way to reverse the polarity in the warp core without it going crit, we should be able to fire a beam of tachyon anti-matter neutrinos and de-cloak a Romulan Warbird at a distance of 3 AUs. Not bad for something Congress threatened to cancel!

An Old Glass Plate Hints at a Potential New Exoplanet Discovery

Polluted white dwarf

What’s the value to exoplanet science of sifting through old astronomical observations? Quite a lot, as a recent discovery out of the Carnegie Institution for Science demonstrates. A glass plate spectrum of a nearby solitary white dwarf known as Van Maanen’s Star shows evidence of rocky debris ringing the system, giving rise to a state only recently recognized as a ‘polluted white dwarf.’ Continue reading “An Old Glass Plate Hints at a Potential New Exoplanet Discovery”

The Laws Of Cosmology May Need A Re-Write

A map of the CMB as captured by the Wilkinson Microwave Anisotropy Probe. Credit: WMAP team

Something’s up in cosmology that may force us to re-write a few textbooks. It’s all centred around the measurement of the expansion of the Universe, which is, obviously, a pretty key part of our understanding of the cosmos.

The expansion of the Universe is regulated by two things: Dark Energy and Dark Matter. They’re like the yin and yang of the cosmos. One drives expansion, while one puts the brakes on expansion. Dark Energy pushes the universe to continually expand, while Dark Matter provides the gravity that retards that expansion. And up until now, Dark Energy has appeared to be a constant force, never wavering.

How is this known? Well, the Cosmic Microwave Background (CMB) is one way the expansion is measured. The CMB is like an echo from the early days of the Universe. It’s the evidence left behind from the moment about 380,000 years after the Big Bang, when the rate of expansion of the Universe stabilized. The CMB is the source for most of what we know of Dark Energy and Dark Matter. (You can hear the CMB for yourself by turning on a household radio, and tuning into static. A small percentage of that static is from the CMB. It’s like listening to the echo of the Big Bang.)

The CMB has been measured and studied pretty thoroughly, most notably by the ESA’s Planck Observatory, and by the Wilkinson Microwave Anisotropy Probe (WMAP). The Planck, in particular, has given us a snapshot of the early Universe that has allowed cosmologists to predict the expansion of the Universe. But our understanding of the expansion of the Universe doesn’t just come from studying the CMB, but also from the Hubble Constant.

The Hubble Constant is named after Edwin Hubble, an American astronomer who observed that the expansion velocity of galaxies can be confirmed by their redshift. Hubble also observed Cepheid variable stars, a type of standard candle that gives us reliable measurements of distances between galaxies. Combining the two observations, the velocity and the distance, yielded a measurement for the expansion of the Universe.

So we’ve had two ways to measure the expansion of the Universe, and they mostly agree with each other. There’ve been discrepancies between the two of a few percentage points, but that has been within the realm of measurement errors.

But now something’s changed.

In a new paper, Dr. Adam Riess of Johns Hopkins University, and his team, have reported a more stringent measurement of the expansion of the Universe. Riess and his team used the Hubble Space Telescope to observe 18 standard candles in their host galaxies, and have reduced some of the uncertainty inherent in past studies of standard candles.

The result of this more accurate measurement is that the Hubble constant has been refined. And that, in turn, has increased the difference between the two ways the expansion of the Universe is measured. The gap between what the Hubble constant tells us is the rate of expansion, and what the CMB, as measured by the Planck spacecraft, tells us is the rate of expansion, is now 8%. And 8% is too large a discrepancy to be explained away as measurement error.

The fallout from this is that we may need to revise our standard model of cosmology to account for this, somehow. And right now, we can only guess what might need to be changed. There are at least a couple candidates, though.

It might be centred around Dark Matter, and how it behaves. It’s possible that Dark Matter is affected by a force in the Universe that doesn’t act on anything else. Since so little is known about Dark Matter, and the name itself is little more than a placeholder for something we are almost completely ignorant about, that could be it.

Or, it could be something to do with Dark Energy. Its name, too, is really just a placeholder for something we know almost nothing about. Maybe Dark Energy is not constant, as we have thought, but changes over time to become stronger now than in the past. That could account for the discrepancy.

A third possibility is that standard candles are not the reliable indicators of distance that we thought they were. We’ve refined our measurements of standard candles before, maybe we will again.

Where this all leads is open to speculation at this point. The rate of expansion of the Universe has changed before; about 7.5 billion years ago it accelerated. Maybe it’s changing again, right now in our time. Since Dark Energy occupies so-called empty space, maybe more of it is being created as expansion continues. Maybe we’re reaching another tipping or balancing point.

The only thing certain is that it is a mystery. One that we are driven to understand.

Who was Albert Einstein?

Albert Einstein's Inventions

At the end of the millennium, Physics World magazine conducted a poll where they asked 100 of the world’s leading physicists who they considered to be the top 10 greatest scientist of all time. The number one scientist they identified was Albert Einstein, with Sir Isaac Newton coming in second. Beyond being the most famous scientist who ever lived, Albert Einstein is also a household name, synonymous with genius and endless creativity.

As the discoverer of Special and General Relativity, Einstein revolutionized our understanding of time, space, and universe. This discovery, along with the development of quantum mechanics, effectively brought to an end the era of Newtonian Physics and gave rise to the modern age. Whereas the previous two centuries had been characterized by universal gravitation and fixed frames of reference, Einstein helped usher in an age of uncertainty, black holes and “scary action at a distance”.

Continue reading “Who was Albert Einstein?”

What are White Holes?

Black holes are created when stars die catastrophically in a supernova. So what in the universe is a white hole?

It’s imagination day, and we’re going to talk about fantasy creatures. Like unicorns, but even rarer. Like leprechauns, but even more fantastical!

Today, we’re going to talk about white holes. Before we talk about white holes, let’s talk about black holes. And before we talk about Black Holes, what’s is this thing you have with holes exactly?

Black holes are places in the Universe where matter and energy are compacted so densely together that their escape velocity is greater than the speed of light. We’ve done at least a million videos on them, but if you still want more info, you can start here with our Black Hole playlist.

Fully describing a black hole requires a lot of fancy math, but these are real objects in our Universe. They were predicted by Einstein’s theory of relativity, and actually discovered over the last few decades.

Black holes are created when stars, much more massive than our Sun, die catastrophically in a supernova.
So then what’s a white hole?

White holes are created when astrophysicists mathematically explore the environment around black holes, but pretend there’s no mass within the event horizon. What happens when you have a black hole singularity with no mass?

White holes are completely theoretical mathematical concepts. In fact, if you do black hole mathematics for a living, I’m told, ignoring the mass of the singularity makes your life so much easier.

They’re not things that actually exist. It’s not like astronomers detected an unusual outburst of radiation and then developed hypothetical white hole models to explain them.

White Hole
White Hole. Image Credit: universe-review.ca

As my good friend and sometimes Guide to Space contributor, Dr. Brian Koberlein says, “If you start with five cupcakes and start giving them away, you eventually run out. At that point you can’t give away any more. In this case you can’t count down past zero. Sure, you can hand out slips of paper with “I O U ONE cupcake.” written on them, but it would be ridiculous to use the existence of negative numbers to claim that “negative cupcakes” exist and can be handed out to people.”

Now if white holes did exist, which they probably don’t, they would behave like reverse black holes – just like the math predicts. Instead of pulling material inward, a white hole would blast material out into space like some kind of white chocolate fountain. So generous, these white holes and their chocolate.

One of the other implications of white hole math, is that they only theoretically exist as long as there isn’t a single speck of matter within the event horizon. As soon as single atom of hydrogen drifted into the region, the whole thing would collapse. Even if white holes were created back at the beginning of the Universe, they would have collapsed long ago, since our Universe is already filled with stray matter.

That said, there are a few physicists out there who think white holes might be more than theoretical. Hal Haggard and Carlo Rovelli of Aix-Marseille University in France are working to explain what happens within black holes using a branch of theoretical physics called loop quantum gravity.

Artistic view of a radiating black hole.  Credit: NASA
Artistic view of a radiating black hole. Credit: NASA

In theory, a black hole singularity would compress down until the smallest possible size predicted by physics. Then it would rebound as a white hole. But because of the severe time dilation effect around a black hole, this event would take billions of years for even the lowest mass ones to finally get around to popping.

If there were microscopic black holes created after the Big Bang, they might get around to decaying and exploding as white holes any day now. Except, according to Stephen Hawking, they would have already evaporated.

Another interesting idea put forth by physicists, is that a white hole might explain the Big Bang, since this is another situation where a tremendous amount of matter and energy spontaneously appeared.

In all likelihood, white holes are just fancy math. And since fancy math rarely survives contact with reality, white holes are probably just imaginary.

What other highly theoretical theories in space and physics would you like us to investigate? Tell us in the comments below.

New Signal May Be Evidence of Dark Matter, Say Researchers

Dark Matter Halo

Dark matter is the architect of large-scale cosmic structure and the engine behind proper rotation of galaxies. It’s an indispensable part of the physics of our Universe – and yet scientists still don’t know what it’s made of. The latest data from Planck suggest that the mysterious substance comprises 26.2% of the cosmos, making it nearly five and a half times more prevalent than normal, everyday matter. Now, four European researchers have hinted that they may have a discovery on their hands: a signal in x-ray light that has no known cause, and may be evidence of a long sought-after interaction between particles – namely, the annihilation of dark matter.

When astronomers want to study an object in the night sky, such as a star or galaxy, they begin by analyzing its light across all wavelengths. This allows them to visualize narrow dark lines in the object’s spectrum, called absorption lines. Absorption lines occur because a star’s or galaxy’s component elements soak up light at certain wavelengths, preventing most photons with those energies from reaching Earth. Similarly, interacting particles can also leave emission lines in a star’s or galaxy’s spectrum, bright lines that are created when excess photons are emitted via subatomic processes such as excitement and decay. By looking closely at these emission lines, scientists can usually paint a robust picture of the physics going on elsewhere in the cosmos.

But sometimes, scientists find an emission line that is more puzzling. Earlier this year, researchers at the Laboratory of Particle Physics and Cosmology (LPPC) in Switzerland and Leiden University in the Netherlands identified an excess bump of energy in x-ray light coming from both the Andromeda galaxy and the Perseus star cluster: an emission line with an energy around 3.5keV. No known process can account for this line; however, it is consistent with models of the theoretical sterile neutrino – a particle that many scientists believe is a prime candidate for dark matter.

The researchers believe that this strange emission line could result from the annihilation, or decay, of these dark matter particles, a process that is thought to release x-ray photons. In fact, the signal appeared to be strongest in the most dense regions of Andromeda and Perseus and increasingly more diffuse away from the center, a distribution that is also characteristic of dark matter. Additionally, the signal was absent from the team’s observations of deep, empty space, implying that it is real and not just instrumental artifact.

In a pre-print of their paper, the researchers are careful to stress that the signal itself is weak by scientific standards. That is, they can only be 99.994% sure that it is a true result and not just a rogue statistical fluctuation, a level of confidence that is known as 4σ. (The gold standard for a discovery in science is 5σ: a result that can be declared “true” with 99.9999% confidence) Other scientists are not so sure that dark matter is such a good explanation after all. According to predictions made based on measurements of the Lyman-alpha forest – that is, the spectral pattern of hydrogen absorption and photon emission within very distant, very old gas clouds – any particle purporting to be dark matter should have an energy above 10keV – more than twice the energy of this most recent signal.

As always, the study of cosmology is fraught with mysteries. Whether this particular emission line turns out to be evidence of a sterile neutrino (and thus of dark matter) or not, it does appear to be a signal of some physical process that scientists do not yet understand. If future observations can increase the certainty of this discovery to the 5σ level, astrophysicists will have yet another phenomena to account for – an exciting prospect, regardless of the final result.

The team’s research has been accepted to Physical Review Letters and will be published in an upcoming issue.

Mysterious Object “G2” at Galactic Center is Actually Binary Star

A mysterious object swinging around the supermassive black hole in the center our galaxy has surprised astronomers by actually surviving what many thought would be a devastating encounter. And with its survival, researchers have finally been able to solve the conundrum of what the object – known as G2 — actually is. Since G2 was discovered in 2011, there was a debate whether it was a huge cloud of hydrogen gas or a star surrounded by gas. Turns out, it was neither … or actually, all of the above, and more.

Astronomers now say that G2 is most likely a pair of binary stars that had been orbiting the black hole in tandem and merged together into an extremely large star, cloaked in gas and dust.

“G2 survived and continued happily on its orbit; a simple gas cloud would not have done that,” said Andrea Ghez from UCLA, who has led the observations of G2. “G2 was basically unaffected by the black hole. There were no fireworks.”

This was one of the “most watched” recent events in astronomy, since it was the first time astronomers have been able to view an encounter with a black hole like this in “real time.” The thought was that watching G2’s demise would not only reveal what this object was, but also provide more information on how matter behaves near black holes and how supermassive black holes “eat” and evolve.

The two Keck 10-meter domes atop Mauna Kea. (Rick Peterson/WMKO)
The two Keck 10-meter domes atop Mauna Kea. (Rick Peterson/WMKO)

Using the Keck Observatory, Ghez and her team have been able to keep an eye on G2’s movements and how the black hole’s powerful gravitational field affected it.

While some researchers initially thought G2 was a gas cloud, others argued that they weren’t seeing the amount of stretching or “spaghettification” that would be expected if this was just a cloud of gas.

As Ghez told Universe Today earlier this year, she thought it was a star. “Its orbit looks so much like the orbits of other stars,” she said. “There’s clearly some phenomenon that is happening, and there is some layer of gas that’s interacting because you see the tidal stretching, but that doesn’t prevent a star being in the center.”

Now, after watching the object the past few months, Ghez said G2 appears to be just one of an emerging class of stars near the black hole that are created because the black hole’s powerful gravity drives binary stars to merge into one. She also noted that, in our galaxy, massive stars primarily come in pairs. She says the star suffered an abrasion to its outer layer but otherwise will be fine.

Ghez explained in a UCLA press release that when two stars near the black hole merge into one, the star expands for more than 1 million years before it settles back down.

“This may be happening more than we thought. The stars at the center of the galaxy are massive and mostly binaries,” she said. “It’s possible that many of the stars we’ve been watching and not understanding may be the end product of mergers that are calm now.”

Ghez and her colleagues also determined that G2 appears to be in that inflated stage now and is still undergoing some spaghettification, where it is being elongated. At the same time, the gas at G2’s surface is being heated by stars around it, creating an enormous cloud of gas and dust that has shrouded most of the massive star.

Usually in astrophysics, timescales of events taking place are very long — not over the course of several months. But it’s important to note that G2 actually made this journey around the galactic center around 25,000 years ago. Because of the amount of time it takes light to travel, we can only now observe this event which happened long ago.

“We are seeing phenomena about black holes that you can’t watch anywhere else in the universe,” Ghez added. “We are starting to understand the physics of black holes in a way that has never been possible before.”

The research has been published in the journal Astrophysical Journal Letters.

Further reading: UCLA, Keck