Tag Archives: spiral galaxy

Astronomers track source of mysterious repeating radio burst to far-away galaxy

Credit:  European VLBI Network (EVN).

An international team of researchers used a whopping eight telescopes, part of the European Very Long Baseline Interferometry Network (EVN), to identify the source of a repeating fast radio burst (FRB) signal. The mysterious repeating signal comes from a spiral galaxy more than 500 million light-years away from Earth.

This is not only the closest repeating FRB we’ve found thus far, but its source is also unlike something astronomers have come across before.

“This blurs the differences between repeating and non-repeating fast radio bursts. It may be that FRBs are produced in a large zoo of locations across the Universe and just require some specific conditions to be visible,” Kenzie Nimmo, an astronomer at the University of Amsterdam and of the lead authors of the new study, said in a statement.

Blink and you’ll miss them

Fast radio bursts are among some of the weirdest astronomical phenomena. They only last for a few fractions of a second but in this short time, they pack more energy than 500 million Suns. They also exhibit the characteristic dispersion sweep of radio pulsars.

By one estimate, there are more than 2,000 of these FRBs firing across the Universe every day, but due to their short-lived nature detecting them is easier said than done.

First discovered in 2007, fast radio bursts continue to puzzle astronomers. Most of them have only appeared once but, to make things even more complicated, some of these signals appear repeatedly.

An animation shows the random appearance of fast radio bursts (FRBs) across the sky. Credit: h/T. Jarrett (IPAC/Caltech).

In 2017, scientists manage to track the source of a repeating FRB for the first time to a dwarf galaxy, located more than 3 billion light-years from Earth. This signal had been distorted by electromagnetic radiation that interacted with the FRB’s magnetic field, leading scientists to believe that the radio bursts were generated by an extreme event, perhaps in the vicinity of a supermassive black hole that typically occupies the heart of a galaxy. What’s more, the signal also bore telltale signs that it originated close to a star-forming region.

Now, a team of astronomers working with the Very Long Baseline Interferometry Network has found the source of a new repeating FRB, which was tracked to an inconspicuous-looking spiral galaxy called SDSS J015800.28+654253.0.

The newly found signal, called FRB 180916, was less distorted which must mean it comes from a region of space that is less disturbed by extreme objects like black holes, likely far away from a galactic center. But, like it predecessor, the bursts came from a region of that galaxy where star formation is prominent.

“With the characterisation of this source, the argument against pulsar-like emission as an origin for repeating FRBs is gaining strength”, says Ramesh Karuppusamy of the Max Planck Institute for Radio Astronomy (MPIfR), a co-author of the study. “We are at the verge of more such localisations brought about by the upcoming newer telescopes. These will finally allow us to establish the true nature of these sources,” he adds.

Astronomers hope to find more such FRBs so close to home in order to study these events in greater detail. In doing so, scientists might come closer to understanding the Universe itself. Why is that? One huge area of study in cosmology is how structures — any structure of any scale — were formed, and to answer such a big question, computational models have to make a lot of assumptions about the conditions of the early Universe. These theoretical results then have to be compared to physical observations of the actual cosmos. But if scientists can map thousands of FRBs from all directions, it is possible to map the distribution of matter across the universe because a FRB’s time delay indirectly offers an estimate of the amount of material between the source and Earth.

“We hope that continued studies will unveil the conditions that result in the production of these mysterious flashes. Our aim is to precisely localize more FRBs and, ultimately, understand their origin”, concludes Jason Hessels, corresponding author on the study, from the Netherlands Institute for Radio Astronomy (ASTRON) and the University of Amsterdam.

“As we continue to unravel the mystery of FRBs, astronomers need to be able to study these sources in incredible detail. The combined sensitivity of the telescopes in the EVN currently provides a unique opportunity to observe these events and we hope that continued observations will contribute to our understanding of these enigmatic sources.” says Francisco Colomer, Director of the Joint Institute for VLBI ERIC.

The findings were reported in the journals Nature and the Astrophysical Journal Letters.

Artist impression of a warped Milky Way. Credit: CHEN Xiaodian.

The Milky Way’s outer disk may actually be warped and twisted

For thousands of years, humans thought that Earth was at the center of the universe. It was only in recent centuries that it became an established scientific fact that Earth orbits the sun, and later that the solar system — along with hundreds of billions of other stars — orbits a common galactic center. Until very recently, it has been very difficult for scientists to visualize what the Milky Way looks like given that we are embedded inside it.

Artist impression of a warped Milky Way. Credit: CHEN Xiaodian.

Artist impression of a warped Milky Way. Credit: CHEN Xiaodian.

Thanks to observation, reconstruction, and comparison to other galaxies, researchers have a fairly accurate idea of what our galaxy looks like. If you were to travel outside the galaxy and look down upon it from above, what you’d see is a barred spiral galaxy with two spiral arms called Scutum–Centaurus and Carina–Sagittarius. But, the spiral disk is anything but stable, new research from China shows. The new study found that the farther away you travel from the galactic core, this disk becomes increasingly warped and twisted.

The Milky Way’s S-like appearance at its edges is due to the fact that gravity becomes weaker the farther you are from the galaxy’s inner regions. Since hydrogen atoms in the far outer disk are no longer confined to a thin plane, they get warped.

There were many challenges in this study. One of them is establishing distances from the sun to the Milky Way’s outer disk when you don’t know what the disk actually looks like yet. The research team at the National Astronomical Observatories of Chinese Academy of Sciences (NAOC), led by Chen Xiaodian, had to employ a new catalog of variable stars known as classical Cepheids. Such stars are hot and massive – five to twenty times the mass of our sun and up to 100,000 times as bright. They also pulsate radially for days to months at a time — and this period of pulsation can be combined with the Cepheid’s brightness to reliably establish its distance from the sun.

A 3D distribution of the classical Cepheids in the Milky Way's warped disk. Credit: CHEN Xiaodian.

A 3D distribution of the classical Cepheids in the Milky Way’s warped disk. Credit: CHEN Xiaodian.

Because they are so bright, Cepheids can be clearly seen millions of light years away and can be easily distinguished from other bright stars in their vicinity, making them indispensable tools in any astronomers’ kit. For instance, it’s thanks to Cepheids that Edwin Hubble and Milton L. Humason were able to prove that the Universe is in a state of expansion. Now, Cepheids have proven their worth once more, establishing an important physical characteristic of the Milky Way’s disk.

“Somewhat to our surprise, we found that in 3D our collection of 1339 Cepheid stars and the Milky Way’s gas disk follow each other closely. This offers new insights into the formation of our home galaxy,” says Prof. Richard de Grijs from Macquarie University in Sydney, Australia, and senior co-author of the paper. “Perhaps more importantly, in the Milky Way’s outer regions, we found that the S-like stellar disk is warped in a progressively twisted spiral pattern.”

The same twisted spiral patterns have been seen before in more than a dozen other galaxies. Combined with these observations, the study’s results suggest that the likely culprit for the Milky Way’s warped spiral pattern is torque from the massive inner disk.

“This new morphology provides a crucial updated map for studies of our galaxy’s stellar motions and the origins of the Milky Way’s disk,” says Dr. DENG Licai, senior researcher at NAOC and co-author of the study published in Nature Astronomy.

Researchers map out the age of the Milky Way’s “heart”

Astronomers have developed the first age-map of the Milky Way galaxy, showing a period of star formation that lasted for 4 billion years.

NGC 1300, a barred spiral galaxy, similar in many ways to the Milky Way. For obvious reasons, we don’t have any real images of our own galaxy. Image credits: Hubble Space Telescope / NASA.

As far as galaxies go, the Milky Way is pretty average. It’s a barred spiral galaxy — a spiral-shaped galaxy with a central bar-shaped structure composed of stars — with a diameter between 100,000 and 180,000 light-years. It’s estimated that our galaxy hosts 100-400 billion stars and at least 100 billion stars.

At its center (the “bar” in the “barred spiral galaxy”), the Milky Way features a star bulge — a massive star population thousands of light years in diameter, containing about a quarter of all the stars in the galaxy. This bulge has two components: a population of metal-poor stars that have a spherical distribution, and a population of metal-rich stars that wrap around them like a waistline or a two-lobed peanut.

[alert style=”alert-info” close=”false”]For astronomers, all elements other than hydrogen and helium are referred to as ‘metals’ — even though elements such as oxygen and carbon which are considered non-metals by chemists. [/alert]

The infrared map constructed from the VISTA Variables in the Via Lactea (VVV) survey of the inner Milky Way showing the studied areas. Credit: ESO/M. Rejkuba/F. Surot Madrid / E. Valenti.

Analyses of these two areas have yielded conflicting results. Now, an international team of researchers has used both simulated and observed data, from millions of stars to map the age and development of these intriguing stars.

“We analysed the colour and brightness of stars to find those that have just reached the point of exhausting their hydrogen fuel-burning in the core, which is a sensitive age indicator. Our findings were not consistent with a purely old Milky Way bulge, but require star formation lasting around 4 billion years and starting around 11 billion years ago. The youngest stars that we see are at least 7 billion years old, which is older than some previous studies had suggested.”

Results paint an interesting overall picture, but it’s still hard to accurately resolve smaller areas within the bulge. Ultimately, researchers hope to create a more accurate, detailed map of the Milky Way core.

Artist’s impression showing the peanut shaped structure in the central bulge. Credit: ESO/NASA/JPL-Caltech/M. Kornmesser/R. Hurt.

Francisco Surot Madrid, the co-lead author of the study, concludes:

“Previous studies have told us that the metal-rich stars in the bar are likely to be the youngest stars. Whilst we can’t disentangle which star belongs to the bar/peanut or the spheroid component in the data we are using, our results tell us that the bar was already formed about 7 billion years ago and there were no large amounts of gas inflowing and forming stars along the bar after that.”

The study hasn’t been peer-reviewed. Results will be presented at the European Week of Astronomy and Space Science.

Spiral galaxy A1689B11 sits behind a massive cluster of galaxies that acts as a lens, producing two magnified images of the spiral galaxy in different positions in the sky. Credit: James Josephide.

What the oldest spiral galaxy can teach us about how the Milky Way evolved

Australian researchers have studied the oldest spiral galaxy to date using a combination of conventional man-made telescopes and natural telescopes. The latter telescopes are made of clusters comprising thousands of galaxies and dark matter, which allow scientists to peer through the cosmos and study far-away objects with unprecedented resolution.

“We are able to look 11 billion years back in time and directly witness the formation of the first, primitive spiral arms of a galaxy,” said Dr Tiantian Yuan, an astronomer at Swinburne University of Technology.

Spiral galaxy A1689B11 sits behind a massive cluster of galaxies that acts as a lens, producing two magnified images of the spiral galaxy in different positions in the sky. Credit: James Josephide.

Spiral galaxy A1689B11 sits behind a massive cluster of galaxies that acts as a lens, producing two magnified images of the spiral galaxy in different positions in the sky. Credit: James Josephide.

Yuan worked with colleagues under the All Sky Astrophysics in 3D, a $40m project funded over the next 7 years by a grant from the Australian Research Council (ARC) and supported by six collaborating Australian universities.

The galaxy in question, considered the most ancient spiral galaxy yet, is called A1689B11. It was imaged with the Near-infrared Integral Field Spectrograph of the Gemini North telescope in Hawaii, in conjunction with one of the cleverest astronomical techniques there is, a little trick called gravitational lensing.  

Famed physicist Albert Einstein predicted, as a result of his Theory of General Relativity, that whenever light from a distant star passes by a closer object, gravity acts like a magnifying lens bending the distant starlight but also brightening it. This effect has been documented extensively around very massive structures such as galaxies.

Captioned below is the great galaxy cluster Abell Cluster 2218. Notice the giant, stretched arcs? Those are actually background galaxies that get distorted and magnified by the giant cluster which bends the light. That’s analogous to how normal lenses such as the ones in a magnifying glass or a pair of spectacles work, by bending light rays that pass through them through refraction in order to focus the light somewhere (such as in your eye). Astronomers often use gravitational lensing as a natural telescope, to great effect.

gravitational lensing

Image credit: ESA, NASA, J.-P. Kneib and Richard Ellis.

Yuan says that if it weren’t for gravitational lensing, they would have never been able to study A1689B11 at this level of detail. His team learned that the ancient spiral galaxy, which has been around for almost 11 billion years, formed stars 20 times faster than the galaxies today.

A1689B11 behaves very differently from other early era galaxies. For instance, it’s characterized by a very cool and thin disc, which rotates relatively calmly with little turbulence. According to Yuan, astronomers have never seen another galaxy from this early period of the universe with such characteristics. Ultimately, A1689B11 may help scientists learn more about how spiral galaxies evolve, the Milky Way included.

Findings will appear in The Astrophysical Journal. A preprint version is available at arXiv:1710.11130.

Astronomers discover a new type of galaxy: Super Spirals

Astronomers have discovered a new species of galaxies in the cosmic wilderness. Called “Super Spirals,” these galaxies are quite similar to normal spiral galaxies except they’re much larger (you know, super). In fact, they’re some of the biggest and brightest objects in the galaxy – and they’ve been hiding in plain sight.

Three examples of super spirals are presented here in images taken by the Sloan Digital Sky Survey.
Credits: SDSS

This strange new type of galactic beast were discovered by a team from the Infrared Processing and Analysis Centre (IPAC) at the California Institute of Technology. They are on average 8-14 times brighter than the Milky Way, possess 10 times as much mass, and create 30 times more stars.

“We have found a previously unrecognized class of spiral galaxies that are as luminous and massive as the biggest, brightest galaxies we know of,” said Patrick Ogle, an astrophysicist at the Infrared Processing and Analysis Center (IPAC) at the California Institute of Technology in Pasadena and lead author of a new paper on the findings published in The Astrophysical Journal. “It’s as if we have just discovered a new land animal stomping around that is the size of an elephant but had shockingly gone unnoticed by zoologists.”

He and his colleagues were searching for massive and bright galaxies. Interestingly, their finding came only from analysis of old data within the NASA/IPAC Extragalactic Database (NED), an online repository containing information on over 100 million galaxies.

“Remarkably, the finding of super spiral galaxies came out of purely analyzing the contents of the NASA/IPAC Extragalactic Database, thus reaping the benefits of the careful, systematic merging of data from many sources on the same galaxies,” said George Helou, a study co-author and the executive director of IPAC. “NED is surely holding many more such nuggets of information, and it is up to us scientists to ask the right questions to bring them out.”

They sampled some 800,000 galaxies, under 3.5 billion light-years from Earth, noticing that 53 of the brightest galaxies intriguingly had a spiral, rather than elliptical, shape. Unlike flat spiral galaxies with organization and structure, elliptic galaxies are more 3D and are generally larger. This prompted astronomers to think they were dealing with a new type of galaxy. Aside for the unusual size and brightness, four of these structures also had double nuclei, like an egg with two yolks. This is a telltale sign that we are dealing with two galaxies merged together, and these early mergers could tell us a lot about their early history.

“Super spirals could fundamentally change our understanding of the formation and evolution of the most massive galaxies,” said Ogle. “We have much to learn from these newly identified, galactic leviathans.”

Journal Reference: Superluminous Spiral Galaxies

Astronomers find out why galaxies get spiral arms

I was always puzzled by the tentacle-like spiral arms some galaxies (including our own) develop; it just seems so counter intuitive and senseless, that most researchers agreed they are only transient features, which come and go in galactic history. But astronomers working at University of Wisconsin-Madison and the Harvard-Smithsonian Center for Astrophysics claim that these are in fact “self-perpetuating, persistent and surprisingly long-lived.”

spiral arms

It’s estimated that some 15 percent of all galaxies have spiral arms, including the Mily Way; to add even more to the mystery, most galaxies in our galactic neighborhood (over 80%) have this feature, while the oldest and largest galaxies in the universe are ellipticals, hinting that spiral galaxies may be a relatively new development in cosmic evolution.

For decades, astrophysicists have debated the nature of these arms, whether they come and go over time or are relatively stable, with variations in gravitational pull on the materials that makes up the arms. The balance seemed to tip towards the first possibility, but new computer simulations which allowed researchers to follow the motions of as many as 100 million “stellar particles,” provided a new perspective on how gravity and other forces mold material into this shape.

A main argument that supported the sustainability of these arms was the influence on neighboring galaxies on each other – but this new study modeled stand-alone disk galaxies — those not influenced by another nearby galaxy or object — and the data it produced suggests that the spiral arms first arise as a result of the influence of giant molecular clouds or star nurseries. Not only does this explain how spiral arms are created, but it also shows how they are perpetuated.

spiral arm2

“Past theory held the arms would go away with the perturbations removed, but we see that [once formed] the arms self-perpetuate, even when the perturbations are removed,” said D’Onghia, a UW-Madison professor of astronomy. “It proves that once the arms are generated through these clouds, they can exist on their own through [the influence of] gravity, even in the extreme when the perturbations are no longer there.”

The model, if valid, could also provide more information on how all galaxies form. y relying on models that show the grouping ”stellar particles,” researchers were able to better model how gravity influences the forming of galaxies.

The study was published in The Astrophysical Journal, and you can read it in its entirety here.

lowest-mass supermassive black hole

Mini-supermassive black hole discovered by astronomers

Though this might sound like an oxymoron, this is possible the best term to describe one of the most interesting recent astronomical finds – the lowest mass supermassive black hole discovered so far. The black hole was detected at the center of a late-spiral galaxy, which astronomers at the Chandra X-Ray Observatory initially believed it shouldn’t had been able to harbor one in the first place, and suggests it has a different origin from that of its more hefty cousins.

lowest-mass supermassive black hole

The spiral galaxy NGC 4178 as imaged by the Sloan Digital Sky Survey. The inset shows an X-ray source at the position of the black hole, in the center of an image from NASA’s Chandra X-ray Observatory. (c) NASA/CXC/George Mason Univ/N.Secrest et al; Optical: SDSS

Located about 55 million light years from Earth, NGC 4178 is a spiral galaxy that doesn’t have a bright central concentration, or bulge of stars in its center. This lead scientists to believe that it shouldn’t have a black hole at its center, like is the case for most galaxies, however X-ray analysis provided by Chandra’s X-Ray vision, as well as infrared data the NASA’s Spitzer Space Telescope and radio data from the Very Large Array, revealed a faint X-ray source beeping from the galaxy’s center. Based on the amount of X-rays at different wavelengths, as well as its brightness at infrared wavelengths, the astronomers found that a black hole must be resting at the center of NGC 4178, rapidly pulling in material from its surrounding.

Using a known relation which factors the mass of a black hole and the amount of X-rays and radio waves it generates, scientists were able to estimate a mass of 200,000 times that of our sun. That may seem like a lot, but typical supermassive black holes are in the range of millions or even billions times more massive than our sun. In fact, the black hole at the center of NGC 4178 is the lowest mass supermassive black holes ever observed, although astronomers admit this is probably near the extreme low-mass end of being in the “supermassive” range.

Previous astronomical research saw a close correlation between the mass of a supermassive black hole and the mass of the bulge of its host galaxy. This lead to the popular belief that galaxies without bulges are unlikely to host supermassive black holes. This recent find counters this prediction, suggesting that the mechanisms of supermassive black hole formation are far from being completely identified.

Findings were published in The Astrophysical Journal.

Click for zoom

Astonishing galactic smash-up as seen by the Gemini Observatory

Click for zoom

Click for zoom

Pictured above is a galactic amalgam of the fantastic proportions, at the center of which lies the polar-ring galaxy NGC 660. Around it, space debris like gas and dust, the wreckage of a colossal galactic struggle, litter its surroundings. Only a few of these bizarre space objects have been discovered thus far.

NGC 660 is in Pisces, and the vast ring of stars and debris around it – 40,000 light-years across – came from another galaxy in a collision that astronomers can now begin to unpick. The whole scene was captured with the Gemini Multi-Object Spectrograph on the Fredrick C. Gillett Gemini North Telescope atop Hawaii’s Mauna Kea volcano.

Spiral Galaxy supernova

Brilliant spiral Galaxy hosts two supernovae in past 30 years [PHOTO]

The European Southern Observatory’s (ESO) Very Large Telescope in Chile is back with yet another stunning gem. This spectacular spiral galaxy has hosted two supernova explosions over the last 30 years, making it particularly interesting. Supernovae are one of the brightest and most energetic events in the Universe.

Spiral Galaxy supernova

The galaxy’s name is NGC 1187, and is located 60 million light years away from Earth , in the constellation Eridanus. The first supernova found in NGC 1187, officially called SN 1982R, was detected in October 1982 at ESO’s La Silla Observatory in Chile’s Atacama Desert. The second one, called SN 2007Y, was spotted by amateur astronomer Berto Monard in South Africa in 2007.

When a star reaches the end of its life, it dies off in a spectacular fashion, exploding with a high energy release. So you can imagine the magnitude of its energy release, consider that the radiated energy during a supernova explosion is comparable to the amount of energy the sun will emit over the entire course of its life. Also, it’s no rare event for a supernova to outshine whole galaxies before fading away during the course of a few years.

The first supernova from NGC 1187 is no longer visible in this image, however the second from 2007 is still visible near the bottom of the image, albeit fainter since it’s well past its climax point. Nevertheless, the spiral galaxy is stunning itself, with or without supernovae.

source MNN. Image credit: ESO.

Artist's rendering of the oldest known spiral galaxy - 11 billion years old. The red area in the upper right corner is a dwarf galaxy that is merging with it. (Dunlap Institute for Astronomy & Astrophysics/Joe Bergeron)

Oldest spiral galaxy is a freak of cosmos

Artist's rendering of the oldest known spiral galaxy - 11 billion years old. The red area in the upper right corner is a dwarf galaxy that is merging with it. (Dunlap Institute for Astronomy & Astrophysics/Joe Bergeron)

Artist’s rendering of the oldest known spiral galaxy – 11 billion years old. The red area in the upper right corner is a dwarf galaxy that is merging with it. (Dunlap Institute for Astronomy & Astrophysics/Joe Bergeron)

In a remarkable discovery, astronomers have found the oldest spiral galaxy to our knowledge –  a three-armed spiral galaxy dating back nearly 11 billion years. It precedes any other previous record holder by about 2 billion years, basically sweeping away the competition. The spiral galaxy is so amazing that it caught astronomers completely by surprise, and even they couldn’t believe what they had stumbled upon at first.

“Our first thought was that we must have the wrong distance for the galaxy,” lead researcher David Law, with the University of Toronto, told Discovery News.

“Then we thought perhaps it was the human brain playing tricks on us. If you look at enough blobby, weird-looking galaxies sooner or later, like a Rorschach blob test, you start to pick out patterns whether or not they’re there,” Law said.

This wasn’t any illusion, any fabric of their imagination. Indeed, the spiral galaxy, dubbed Q2343-BX442 and located in the direction of the Pegasus constellation, had its structured imaged by the Hubble Space Telescope and was confirmed by the Keck II telescope in Hawaii, which studied the object’s internal motions. Studies of spectra from more than 3,600 locations in and around the galaxy revealed that it is, indeed, a rotating spiral galaxy.

The galaxy was present in the early universe, about 3 billion years after the Big Bang, at a time when galaxies were still forming and normally looked clumpy and irregular. “The vast majority of old galaxies look like train wrecks,” said UCLA astronomer Alice E. Shapley, one of the discoverers of the unusual spiral galaxy. “Our first thought was, why is this one so different, and so beautiful?”

Ancient galaxy has spiral days numbered

Ancient spiral galaxies are extremely rare. Actually out of a sample bundle of  306 Hubble Space Telescope imaged ancient galaxies, only ONE presented a spiral structure – the very object of discussion in this article, BX442. This very atypical placement of the spiral galaxy at such an early phase of the Universe is what sparked scientists to investigate it with great scrutiny. The team came to the conclusion that the galaxy’s shape is due to gravitational effects of a smaller galaxy in its vicinity. If that proves to be true, than BX442 wouldn’t had last as a spiral galaxy for too long.

Computer simulations show BX442, a relatively large galaxy with about the same mass as the Milky Way, would only last about 100 million years as a spiral structure.

“We think that we just happened to catch it at a very special time,” Shapley said. “I’d say by today, it probably doesn’t look like a spiral galaxy.”

Our own spiral galaxy, the Milky Way, belongs to a longer-lived class.

“One of the leading mechanisms that we believe explains modern day spirals, such as the Milky Way, is what is called ‘density wave theory,’ which doesn’t need any kind of nearby galaxy. It happens from the disk alone in isolation,” Law said.

The findings were reported in journal Nature.