Posted on by Matt Williams

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

An artist's conception of a hypervelocity star that has escaped the Milky Way. Credit: NASA

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.

Using ESO's Very Large Telescope, astronomers have recorded a massive star moving at more than 2.6 million kilometres per hour. Stars are not born with such large velocities. Its position in the sky leads to the suggestion that the star was kicked out from the Large Magellanic Cloud, providing indirect evidence for a massive black hole in the Milky Way's closest neighbour. Credit: ESO
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
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?

Could an alien spore really travel light years between different star systems? Well, as long as your theory doesn't require it to still be alive when it arrives - sure it can.
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.

Further Reading: arxiv.org/1411.5022, arxiv.org/1411.5030

Posted on by Matt Williams

Astronomers Poised to Capture Image of Supermassive Milky Way Black Hole

This artist's conception illustrates a supermassive black hole (central black dot) at the core of a young, star-rich galaxy. Now astronomers have found a rogue SMBH travelling through space. Image credit: NASA/JPL-Caltech

Scientists have long suspected that supermassive black holes (SMBH) reside at the center of every large galaxy in our universe. These can be billions of times more massive than our sun, and are so powerful that activity at their boundaries can ripple throughout their host galaxies.

In the case of the Milky Way galaxy, this SMBH is believed to correspond with the location of a complex radio source known as Sagittarius A*.  Like all black holes, no one has even been able to confirm that they exist, simply because no one has ever been able to observe one.

But thanks to researchers working out of MIT’s Haystack Observatory, that may be about to change. Using a new telescope array known as the “Event Horizon Telescope” (EHT), the MIT team hopes to produce this “image of the century” very soon.Initially predicted by Einstein, scientists have been forced to study black holes by observing their apparent effect on space and matter in their vicinity. These include stellar bodies that have periodically disappeared into dark regions, never to be heard from again.

As Sheperd Doeleman, assistant director of the Haystack Observatory at Massachusetts Institute of Technology (MIT), said of black holes: “It’s an exit door from our universe. You walk through that door, you’re not coming back.”

Image of the M87 Galaxy, 50 million ly from the Milky Way, which is believed to have a SMBH at its center. Credit: NASA/CXC/KIPAC/NSF/NRAO/AUI
Image of the M87, a giant elliptical galaxy that is believed to have a SMBH at its center. Credit: NASA/CXC/KIPAC/NSF/NRAO/AUI

As the most extreme object predict by Einstein’s theory of gravity, supermassive black holes are the places in space where, according to Doeleman, “gravity completely goes haywire and crushes an enormous mass into an incredibly close space.”

To create the EHT array, the scientists linked together radio dishes in Hawaii, Arizona, and California. The combined power of the EHT means that it can see details 2,000 times finer than what’s visible to the Hubble Space Telescope.

These radio dishes were then trained on M87, a galaxy some 50 million light years from the Milky Way in the Virgo Cluster, and Sagittarius A* to study the event horizons at their cores.

Other instruments have been able to observe and measure the effects of a black hole on stars, planets, and light. But so far, no one has ever actually seen the Milky Way’s Supermassive black hole.

According to David Rabanus, instruments manager for ALMA: “There is no telescope available which can resolve such a small radius,” he said. “It’s a very high-mass black hole, but that mass is concentrated in a very, very small region.”

Doeleman’s research focuses on studying super massive black holes with sufficient resolution to directly observe the event horizon. To do this his group assembles global networks of telescopes that observe at mm wavelengths to create an Earth-size virtual telescope using the technique of Very Long Baseline Interferometry (VLBI).

Sagittarius A
Image of Sagittarius A*, the complex radio source at the center of the Milky Way, and believed to be a SMBH. Credit: NASA/Chandra

“We target SgrA*, the 4 million solar mass black hole at the center of the Milky Way, and M87, a giant elliptical galaxy,” says Doeleman. “Both of these objects present to us the largest apparent event horizons in the Universe, and both can be resolved by (sub)mm VLBI arrays.” he added. “We call this project The Event Horizon Telescope (EHT).”

Ultimately, the EHT project is a world-wide collaboration that combines the resolving power of numerous antennas from a global network of radio telescopes to capture the first image ever of the most exotic object in our Universe – the event horizon of a black hole.

“In essence, we are making a virtual telescope with a mirror that is as big as the Earth,” said Doeleman who is the principal investigator of the Event Horizon Telescope. “Each radio telescope we use can be thought of as a small silvered portion of a large mirror. With enough such silvered spots, one can start to make an image.”

“The Event Horizon Telescope is the first to resolve spatial scales comparable to the size of the event horizon of a black hole,” said University of California, Berkeley astronomer Jason Dexter. “I don’t think it’s crazy to think we might get an image in the next five years.”

First postulated by Albert Einstein’s Theory of General Relativity, the existence of black holes has since been supported by decades’ worth of observations, measurements, and experiments. But never has it been possible to directly observe and image one of these maelstroms, whose sheer gravitational power twists and mangle the very fabric of space and time.

Finally being able to observe one will not only be a major scientific breakthrough, but could very well provide the most impressive imagery ever captured.

Posted on by Matt Williams

“Eye of Sauron” Galaxy Used For New Method of Galactic Surveying

Image of the spiral galaxy NGC 4151, aka. "Sauron's Eye". Credit: X-ray: NASA/CXC/CfA/J.Wang et al.; Optical: Isaac Newton Group of Telescopes, La Palma/Jacobus Kapteyn Telescope; Radio: NSF/NRAO/VLA.

Determining the distance of galaxies from our Solar System is a tricky business. Knowing just how far other galaxies are in relation to our own is not only key to understanding the size of the universe, but its age as well. In the past, this process relied on finding stars in other galaxies whose absolute light output was measurable. By gauging the brightness of these stars, scientists have been able to survey certain galaxies that lie 300 million light years from us.

However, a new and more accurate method has been developed, thanks to a team of scientists led by Dr. Sebastian Hoenig from the University of Southampton. Similar to what land surveyors use here on Earth, they measured the physical and angular (or apparent) size of a standard ruler in the galaxy to calibrate distance measurements.

Hoenig and his team used this method at the W. M. Keck Observatory, near the summit of Mauna Kea in Hawaii, to accurately determine for the first time the distance to the NGC 4151 galaxy – otherwise known to astronomers as the “Eye of Sauron”. Continue reading ““Eye of Sauron” Galaxy Used For New Method of Galactic Surveying”

Posted on by Elizabeth Howell

Surprise! Tiny Galaxy Sports A Huge Black Hole, And There Could Be More Like It

Artist's conception of a supermassive black hole in a galaxy's center. Credit: NASA/JPL-Caltech

In a finding that could turn supermassive black hole formation theories upside-down, astronomers have spotted one of these beasts inside a tiny galaxy just 157 light-years across — about 500 times smaller than the Milky Way.

The clincher will be if the team can find more black holes like it, and that’s something they’re already starting to work on after the discovery inside of galaxy M60-UCD1. The ultracompact galaxy is one of only about 50 known to astronomers in the nearest galaxy clusters.

“It’s very much like a pinprick in the sky,” said lead researcher Anil Seth, an astrophysicist at the University of Utah, of M60-UCD1 during an online press briefing Tuesday (Sept. 16).

Seth said he realized something special was happening when he saw the plot for stellar motions inside of M60-UCD1, based on data from the Gemini North Telescope in Hawaii. The stars in the center of the galaxy were orbiting much more rapidly than those at the edge. The velocity was unexpected given the kind of stars that are in the galaxy.

“Immediately when I saw the stellar motions map, I knew we were seeing something exciting,” Seth said. “I knew pretty much right away there was an interesting result there.”

Ultracompact dwarf galaxy M60-UCD1 shines in the inset image based on images from the Hubble Space Telescope and Chandra X-Ray Telescope. Chandra data is pink, and Hubble data is red, green and blue. The large galaxy dominating the field of view of M60. At the right edge is NGC 4647. Credit: X-ray: NASA/CXC/MSU/J.Strader et al, Optical: NASA/STScI
Ultracompact dwarf galaxy M60-UCD1 shines in the inset image based on images from the Hubble Space Telescope and Chandra X-Ray Telescope. Chandra data is pink, and Hubble data is red, green and blue. The large galaxy dominating the field of view is M60. At the right edge is NGC 4647. Credit: X-ray: NASA/CXC/MSU/J.Strader et al, Optical: NASA/STScI

In its weight class, M60-UCD1 is a standout. Last year, Seth was second co-author on a group that announced that it was the densest nearby galaxy, with stars jam-packed 25 times closer than in the Milky Way. It’s also one of the brightest they know of, a fact that is helped by the galaxy’s relative closeness to Earth. It’s roughly 54 million light-years away, as is the massive galaxy it orbits: M60. The two galaxies are only 20,000 light-years apart.

Supermassive black holes are known to lurk in the centers of most larger galaxies, including the Milky Way. How they got there in the first place, however, is unclear. The find inside of M60-UCD1 is especially intriguing given the relative size of the black hole to the galaxy itself. The black hole is about 15% of the galaxy’s mass, with an equivalent mass of 21 million Suns. The Milky Way’s black hole, by contrast, takes up less than a percentage of our galaxy’s mass.

Given so few ultracompact galaxies are known to astronomers, some basic properties are a mystery. For example, the mass of these galaxy types tends to be higher than expected based on their starlight.

Some astronomers suggest it’s because they have more massive stars than other galaxy types, but Seth said measurements of stars within M60-UCD1 (based on their orbital motion) show normal masses. The extra mass instead comes from the black hole, he argues, and that will likely be true of other ultracompact galaxies as well.

A Hubble Space Telescope image of ultracompact galaxy M60-UCD1 (inset), which is suspected to host a supermassive black hole at its center. It is orbiting the nearby massive galaxy M60. Within the same field of view is NGC 4647. Credit: NASA/Space Telescope Science Institute/European Space Agency
A Hubble Space Telescope image of ultracompact galaxy M60-UCD1 (inset), which is suspected to host a supermassive black hole at its center. It is orbiting the nearby massive galaxy M60. Within the same field of view is NGC 4647. Credit: NASA/Space Telescope Science Institute/European Space Agency

“It’s a new place to look for black holes that was previously not recognized,” he said, but acknowledged the idea of black holes existing in similar galaxies will not be widely accepted until the team makes more finds. An alternative explanation to a black hole could be a suite of low-mass stars or neutron stars that do not give off a lot of light, but Seth said the number of these required in M60-UCD1 is “unreasonably high.”

His team plans to look at several other ultracompact galaxies such as M60-UCD1, but perhaps only seven to eight others would be bright enough from Earth to perform these measurements, he said. (Further work would likely require an instrument such as the forthcoming Thirty-Meter Telescope, he said.) Additionally, Seth has research interests in globular clusters — vast collections of stars — and plans a visit to Hawaii next month to search for black holes in these objects as well.

Results were published today (Sept. 17) in the journal Nature.

Posted on by Brian Koberlein

What Would It Be Like To Fall Into A Black Hole?

This artist’s impression shows the surroundings of the supermassive black hole at the heart of the active galaxy NGC 3783 in the southern constellation of Centaurus (The Centaur). Credit: ESO/M. Kornmesser

Let’s say you happened to fall into the nearest black hole? What would you experience and see? And what would the rest of the Universe see as this was happening?

Let’s say you decided to ignore some of my previous advice. You’ve just purchased yourself a space dragon from the Market on the Centauri Ringworld, strapped on your favorite chainmail codpiece and sonic sword and now you’re going ride head first into the nearest black hole.

We know it won’t take you to another world or galaxy, but what would you experience and see on your way to your inevitable demise? And what would the rest of the Universe see as this was happening, and would they point and say “eewwwwww”?

If you were falling toward a black hole, most of the time you would simply feel weightless, just as if you were playing Bowie songs and floating in a most peculiar way in the International Space Station. The gravity of a black hole is just like the gravity of any other large mass, as long as you don’t get too close. But, as we’ve agreed, you’re ignoring my advice and flying dragon first into this physics nightmare. As you get closer, the gravitational forces on various parts of your and your dragon’s body would be different. Technically this is always true, but you wouldn’t notice it… at least at first.

Suppose you were falling feet first toward a black hole. As you got closer, your feet would feel a stronger force than your head, for example. These differences in forces are called tidal forces. Because of the tidal forces it would feel as if you are being stretched head to toe, while your sides would feel like they are being pushed inward. Eventually the tidal forces would become so strong that they would rip you apart. This effect of tidal stretching is sometimes boringly referred to as spaghettification.

I’ve made up some other names for it, such as My Own Private String Cheese Incident, “the soft-serve effect” and “AAAHHHHH AHHHH MY LEGS MY LEGS!!!”.

So, let’s summarize. You wouldn’t survive falling toward a black hole because you wouldn’t listen. Why won’t you ever listen?

A friend watching you fall toward a black hole would never see you reach the black hole. As you fall towards it, gravity would cause any light coming from you to be redshifted. So as you approached the black hole you would appear more and more reddish, and your image would appear dimmer and dimmer. Your friend would see you redden and dim as you approach, but never quite reach, the event horizon of the black hole. If they could still see you past this point, there would be additional red from the inside of you clouding up the view.

Artist's conception of the event horizon of a black hole. Credit: Victor de Schwanberg/Science Photo Library
Artist’s conception of the event horizon of a black hole. Credit: Victor de Schwanberg/Science Photo Library

Hypothetically, if you could survive crossing the event horizon of a black hole, what
would you see then? Contrary to popular belief, you would not see the entire future of the universe flash before you.

What you would see is the darkness of the black hole fill your view and as you approached the event horizon you would see stars and galaxies on the edge of your view being gravitationally lensed by the black hole. The sky would simply appear more and more black until you reach the event horizon.

Many people think that it is at the event horizon where you would be ripped apart, and at the event horizon all sorts of strange things occur. Unfortunately, this goes along with those who suspect black holes are actually some sort of portal. For a solar mass black hole, the tidal forces near the event horizon can be quite large, but for a supermassive black hole they aren’t very large at all.

In fact, the larger the black hole, the weaker the tidal forces near its event horizon. So if you happened to be near a supermassive black hole, you could cross the event horizon without really noticing. Would you still be totally screwed? YOU BETCHA!

What do you think? If you could drop anything into a black hole, what would it be? Tell us in the comments below.

Posted on by Nancy Atkinson

Watch Live as Astronomers Look for Object ‘G2’ in Observing Run Webcast from the Keck Observatory

This simulation shows the possible behavior of a gas cloud that has been observed approaching the black hole at the center of the Milky Way. Graphic by ESO/MPE/Marc Schartmann.

Wondering about the latest news on the intriguing object called ‘G2’ that is making its closest approach to the supermassive black hole at the center of our galaxy? You might be able to get the latest update on this object in real time during a rare live-streamed observing run from the W. M. Keck Observatory in Hawaii. Watch live above.

The two 10-meter Keck Observatory telescopes on the summit of Mauna Kea will be steered by astronomer Andrea Ghez and her team of observers from the UCLA Galactic Center Group for two nights to study our galaxy’s supermassive black hole, with an attempt to focus in on the enigmatic G2 to see if it is still intact. They’ll also be setting up a test for Einstein’s General Relativity and gathering more data on what they describe as The Paradox of Youth: young objects paradoxically developing around the black hole.

Here’s the time for the livestream in various timezones:

July 3, 2014 @ 9 pm – 10 pm Hawaii
July 4, 2014 @ Midnight – 1 am Pacific
July 4, 2014 @ 3 am – 4 am Eastern

The most previous observations by the Keck Observatory in Hawaii, according to an Astronomer’s Telegram from May 2, 2014 show that the gas cloud called ‘G2’ was surprisingly still intact, even during its closest approach to the supermassive black hole. This means G2 is not just a gas cloud, but likely has a star inside.

“We conclude that G2, which is currently experiencing its closest approach, is still intact, in contrast to predictions for a simple gas cloud hypothesis and therefore most likely hosts a central star,” said the May 2 Telegram. “Keck LGSAO observations of G2 will continue in the coming months to monitor how this unusual object evolves as it emerges from periapse passage.”

For additional info, see our two previous articles about G2:

Gas Cloud or Star? Mystery Object Heading Towards our Galaxy’s Supermassive Black Hole is Doomed
Object “G2? Still Intact at Closest Approach to Galactic Center, Astronomers Report

Posted on by Elizabeth Howell

Supermassive Black Hole Shows Strange Gas Movements

A Hubble Space Telescope image of NGC 5548. Credit: ESA/Hubble and NASA. Acknowledgement: Davide de Martin

Sometimes it takes a second look — or even more — at an astronomical object to understand what’s going on. This is what happened after astronomers obtained this image of NGC 5548 using the Hubble Space Telescope in 2013. While crunching the data, they saw some gas moving around the galaxy in a way that they did not understand.

From the supermassive black hole embedded in the galaxy’s heart, the researchers detected gas moving outward quite quickly — blocking about 90% of the X-rays being emitted from the black hole, a common feature of objects of this type. So, astronomers marshalled a bunch of telescopes to figure out the answer.

Here’s what they knew before: black holes force matter into a spiral that surround the object, creating a flat plane of material known as an accretion disc. Heating in this disc sends out the aforementioned X-rays as well as some ultraviolet radiation. But NGC 5548 is doing something different.

The gas stream, researchers stated, “absorbs most of the X-ray radiation before it reaches the original cloud, shielding it from X-rays and leaving only the ultraviolet radiation. The same stream shields gas closer to the accretion disc. This makes the strong winds possible, and it appears that the shielding has been going on for at least three years.”

Artist's conception of the environment around NGC 5548. This shows a dark swarm of material above the supermassive black hole, as well as the view that the Hubble Space Telescope had of the scene. Credit: NASA, ESA, and A. Feild (STScI)
Artist’s conception of the environment around NGC 5548. This shows a dark swarm of material above the supermassive black hole, as well as the view that the Hubble Space Telescope had of the scene. Credit: NASA, ESA, and A. Feild (STScI)

Quite the suite of telescopes did follow-up observations: NASA’s Swift spacecraft, Nuclear Spectroscopic Telescope Array (NuSTAR) and Chandra X-ray Observatory, and ESA’s X-ray Multi-Mirror Mission (XMM-Newton) and Integral gamma-ray observatory (INTEGRAL).

“This is a milestone in understanding how supermassive black holes interact with their host galaxies,” stated lead researcher Jelle Kaastra of the SRON Netherlands Institute for Space Research.

“We were very lucky. You don’t normally see this kind of event with objects like this. It tells us more about the powerful ionised winds that allow supermassive black holes in the nuclei of active galaxies to expel large amounts of matter. In larger quasars than NGC 5548, these winds can regulate the growth of both the black hole and its host galaxy.”

The research is available in Science Express and also in preprint version on Arxiv.

Sources: NASA and Spacetelescope.org

Posted on by Nancy Atkinson

Gas Cloud or Star? Mystery Object Heading Towards Our Galaxy’s Supermassive Black Hole is Doomed

This simulation shows the G2 gas cloud/star during its close approach to the black hole at the center of the Milky Way. Image by ESO/MPE/Marc Schartmann.

Observatories around the world and in space have been honed-in on the center of our galaxy, looking for possible fireworks to erupt as a mystery object heads towards our galaxy’s supermassive black hole. The object – called G2 – is being watched in an intense observing campaign across all wavelengths with multiple observatories. This is the first time astronomers have been able to watch an encounter with a black hole like this in real time, and the hope is that watching G2’s demise will reveal not only what this object actually is, but also provide more information on how matter behaves near black holes and how supermassive black holes “eat” and evolve.

“We’re indeed working on new observation of G2 right now,” astronomer Leo Meyer from UCLA told Universe Today, “and we’re in a position to make a significant new statement about it very soon.”

G2 was first spotted in 2011 and was quickly deemed to be heading towards our galaxy’s supermassive black hole, called Sgr A*. Astronomers estimate G2 has a mass roughly three times that of Earth (versus the black hole, which is 4 million times the mass of our Sun). G2 is not falling directly into the black hole, but it will pass Sgr A* at about 100 times the distance between Earth and the Sun. But that’s close enough to predict that G2 is doomed for destruction.

Shown here are VLT observations from 2006, 2010 and 2013, colored blue, green and red respectively showing a gas cloud being ripped apart by the supermassive black hole at the center of the galaxy. Credit: ESO/S. Gillessen.

Shown here are VLT observations from 2006, 2010 and 2013, colored blue, green and red respectively showing a gas cloud being ripped apart by the supermassive black hole at the center of the galaxy. Credit: ESO/S. Gillessen.

By last July, observations from the Very Large Telescope showed the object being stretched over more than 160 billion kilometers by the black hole’s extreme gravitational field.

Closest approach was expected to have happened by now (April 2014), but nobody’s talking publicly yet about what has been observed, although Meyer hinted news would be coming soon.

The last notification on the G2 Gas Cloud Wiki page (put together by Stefan Gillessen of the Max Planck Institute in Germany, who has lead several observing runs) was posted on April 21, 2014. This notification reported no strong flare of Sgr A* although it was around the expected time peri-center passing for G2, but there has been a rather constant radio detection of 22 GHz at that location with Japanese VLBI Network.

Northwestern University’s Daryl Haggard said in an early April 2014 press release that recent Chandra observations do not show any enhanced emissions in X-rays, adding “from the X-ray perspective, the gas cloud is late to the party, but it remains to be seen whether G2 is fashionably late or a no show.”

And that points to one question about G2: what is it exactly? Haggard called it a gas cloud, but UCLA astronomer Andrea Ghez said there’s actually a debate about what it is.

“There are two camps on that,” she told Universe Today. “Some people have suggested this is a gas cloud. But I think it’s a star. Its orbit looks so much like the orbits of other stars. 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.”

Some astronomers argue that they aren’t seeing the amount of stretching or “spaghettification” that would be expected if this was just a cloud of gas.

Montage of simulation images showing G2 during its close approach to the black hole at the center of the Milky Way. Images by ESO/MPE/Marc Schartmann
Montage of simulation images showing G2 during its close approach to the black hole at the center of the Milky Way. Images by ESO/MPE/Marc Schartmann

Meyer said the stretching from the object tidally reacting to the back hole clearly points to gas, but that doesn’t tell you if something is hidden inside it or not.

“While it is getting stretched, the luminosity is staying surprisingly constant, and that is puzzling the theorists,” Meyer said.

Another puzzle is the timing of when G2’s closest approach would take place. When news of G2 first broke, it was thought that the time of closest approach to the black hole would be in mid-2013. But further observations determined that that estimate was not accurate and Spring 2014 was actually when closest approach would occur.

“This makes this year’s observations so relevant and our upcoming report significant — especially regarding the issue whether there is a star inside the cloud or not,” Meyer told Universe Today via email.

But, Ghez said, we’ll soon know the answer of what this object is.

“This is just the process of science and it’s interesting – because we’ll have a limited set of observations to find out what this is,” she said. “And it may be a gas cloud or it may be a star, but it’s pretty exciting in astronomy to have an event that everybody gets to line up and buy tickets for.”

Another question is if there actually will be any “fireworks” – as Meyer called it – when G2 meets its ultimate doom as it gets shredded and possibly eaten by the black hole. As the object approaches the black hole and gets disrupted, the gas will rain down onto the back hole, increasing the black hole’s mass, possibly making it brighter. Will this create a “flash” or possibly even a jet from the black hole?

“We don’t know, and there are a lot of uncertainties,” Meyer said at the American Astronomical Society meeting in January 2014. “This is something we haven’t seen before, and even if we don’t know if something will happen or not, it still is worth looking. It’s a unique opportunity to learn about fundamental astrophysics. Even if it’s not super-spectacular, we can still learn things.”

Meyer hinted in January that astronomers might not see much at all.

“Whatever gas might end up in the black hole might get smeared out so much that the amount of mass that gets dumped into the back might be very little,” he said. “This dietary supplement might be very little, like a pea or something!”

Our galaxy’s supermassive black hole has long been fairly inactive, but in 2013, NASA’s Swift Gamma-Ray Burst mission detected the brightest flare ever observed from Sgr A*. However, it’s not certain if this burst was related to G2 or not.

Ghez has said these observations of G2 are similar to the search for extraterrestrial life: the odds to see something are against you, but you still have to look, because if you find something, it will be spectacular.

This is exciting for astronomers, since they usually don’t get to see events like this take place “in real time.” In astrophysics, timescales of events taking place are usually very long — not over the course of several months. But it’s important to note that G2 actually met its demise 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.

Unfortunately, this event is beyond what amateur astronomers can observe.

“We really need to use the worlds’ most advanced observatories to observe this,” Meyer said in January, “as we have to go to multiple wavelengths and use adaptive optics since the galactic center is not visible to light in seen by our eyes, and you need a high angular resolution to see it.”

Posted on by Elizabeth Howell

Tranquil-Looking Galaxy Bears ‘Battle Scars’ From Ancient Struggles

NGC 1316 (left) and its smaller companion galaxy NGC 1317. Image taken with the MPG/ESO 2.2-metre telescope at ESO’s La Silla Observatory in Chile. Credit: ESO

Shining 60 million light-years away all serene-looking is NGC 1316 (left) and a smaller galaxy NGC 1317. This new picture from the European Southern Observatory’s La Silla Observatory in Chile, however, reveals “battle scars” of ancient fights, the observatory stated.

“Several clues in the structure of NGC 1316 reveal that its past was turbulent. For instance, it has some unusual dust lanes embedded within a much larger envelope of stars, and a population of unusually small globular star clusters. These suggest that it may have already swallowed a dust-rich spiral galaxy about three billion years ago,” the European Southern Observatory stated.

“Also seen around the galaxy are very faint tidal tails — wisps and shells of stars that have been torn from their original locations and flung into intergalactic space. These features are produced by complex gravitational effects on the orbits of stars when another galaxy comes too close. All of these signs point to a violent past during which NGC 1316 annexed other galaxies and suggest that the disruptive behavior is continuing.”

You might better known NGC 1316 as Fornax A, the brightest radio source in the constellation Fornax and the fourth-brightest source in the sky. This is due to its supermassive black hole sucking up material in the area — and could actually be stronger because of the close encounters with other galaxies.

This image is a composite of archival pictures from the telescope. If you look closely, you can spot some fainter galaxies in the background, too.

Source: ESO

Posted on by Elizabeth Howell

Supermassive Black Hole’s Dizzying Spin Is Half The Speed Of Light

This photo combination shows the quasar RX J1131-1231 imaged by NASA's Chandra X-ray Observatory and the Hubble Space Telescope. Credit: X-ray: NASA/CXC/Univ of Michigan/R.C.Reis et al; Optical: NASA/STScI

The spin rate of the most distant supermassive black hole has been measured directly, and wow, is it fast. X-ray observations of  RX J1131-1231 (RX J1131 for short) show it is whizzing around at almost half the speed of light. Through X-rays, the astronomers were able to peer at the rate of debris fall into the singularity, yielding the speed measurement.

“We estimate that the X-rays are coming from a region in the disk located only about three times the radius of the event horizon — the point of no return for infalling matter,” stated Jon Miller, an an associate professor of astronomy at the University of Michigan and a co-author on the paper. “The black hole must be spinning extremely rapidly to allow a disk to survive at such a small radius.”

Supermassive black holes are embedded in the heart of most galaxies, and are millions or even billions of times for massive than the Sun. This makes the spin speed astonishingly fast, but also gives astronomers clues about how the host galaxy evolved.

“The growth history of a supermassive black hole is encoded in its spin, so studies of spin versus time can allow us study the co-evolution of black holes and their host galaxies,” stated Mark Reynolds, an assistant research scientist in astronomy at University of Michigan, another co-author on the study.

An artist's conception of jets protruding from a quasar. Credit: ESO/M. Kornmesser
An artist’s conception of jets protruding from a quasar. Credit: ESO/M. Kornmesser

RX J1131 is six billion light-years away from Earth and classified as a quasar, a type of object that occurs when a lot of matter plunges into a supermassive black hole.

“Under normal circumstances, this faraway quasar would be too faint to study. But the researchers were able to take advantage of a sort of natural telescope effect known as gravitational lensing and a lucky alignment of the quasar and a giant elliptical galaxy to get a closer view,” the University of Michigan stated.

“Gravitational lensing, first predicted by Einstein, occurs when the gravity of massive objects acts as a lens to bend, distort and magnify the light from more distant objects as it passes.”

In this case, the researchers used the Chandra X-ray Observatory and the European Space Agency’s XMM-Newton Telescope to capture the X-ray images.

The research was led Rubens Reis, a postdoctoral research fellow in astronomy the University of Michigan. The paper is published today (March 5) in Nature.

For further reading, see the Chandra website and the associated NASA press release.

Source: University of Michigan