Star Should Have Gone Supernova, But it Imploded Into a Black Hole Instead

Collapsing stars are a rare thing to witness. And when astronomers are able to catch a star in the final phase of its evolution, it is a veritable feast for the senses. Ordinarily, this process consists of a star undergoing gravitational collapse after it has exhausted all of its fuel, and shedding its outer layers in a massive explosion (aka. a supernova). However, sometimes, stars can form black holes without the preceding massive explosion.

This process, what might be described as “going out not with a bang, but with a whimper”, is what a team of astronomers witnessed when observing N6946-BH1 – a star located in the Fireworks Galaxy (NGC 6946). Originally, astronomers thought that this star would exploded because of its significant mass. But instead, the star simply fizzled out, leaving behind a black hole.

The Fireworks Galaxy, a spiral galaxy located 22 million light-years from Earth, is so-named because supernova are known to be a frequent occurrence there. In fact, earlier this month, an amateur astronomer spotted what is now designated as SN 2017eaw. As such, three astronomers from Ohio Sate University (who are co-authors on the study) were expecting N6946-BH1 would go supernova when in 2009, it began to brighten.

Visible-light and near-infrared photos from NASA’s Hubble Space Telescope showing the giant star N6946-BH1 before and after it vanished out of sight by imploding to form a black hole. Credit: NASA/ESA/C. Kochanek (OSU)

However, by 2015, it appeared to have winked out. As such, the team went looking for the remnants of it with the help of colleagues from Ohio State University and the University of Oklahoma. Using the combined power of the Large Binocular Telescope (LBT) and NASA’s Hubble and Spitzer space telescopes, they realized that the star had completely disappeared from sight.

The details of their research appeared in a study titled “The Search for Failed Supernovae with the Large Binocular Telescope: Confirmation of a Disappearing Star“, which recently appeared in the Monthly Notices of the Royal Astronomical Society. Among the many galaxies they were watching for supernovas, they had their sights set on the Fireworks Galaxy to see what had become of N6946-BH1.

After it experienced a weak optical outburst in 2009, they had anticipated that this red supergiant would go supernova – which seemed logical given that it was 25 times as massive as our Sun. After winking out in 2015, they had expected to find that the star had merely dimmed, or that it had cast off a dusty shell of material that was obscuring its light from view.

Their efforts included an LBT survey for failed supernovae, which they combined with infrared spectra obtained by the Spitzer Space Telescope and optical data from Hubble. However, all the surveys turned up negative, which led them to only one possible conclusion: that N6946-BH1 must have failed to go supernova and instead went straight to forming a blackhole.

Simulated view of a black hole. Credit: Bronzwaer/Davelaar/Moscibrodzka/Falcke, Radboud University

As Scott Adams – a former Ohio State student who is now an astrophysicist at the Cahill Center for Astrophysics (and the lead author of the study) – explained in a NASA press release:

“N6946-BH1 is the only likely failed supernova that we found in the first seven years of our survey. During this period, six normal supernovae have occurred within the galaxies we’ve been monitoring, suggesting that 10 to 30 percent of massive stars die as failed supernovae. This is just the fraction that would explain the very problem that motivated us to start the survey, that is, that there are fewer observed supernovae than should be occurring if all massive stars die that way.”

A major implication of this study is the way it could shed new light on the formation of very massive black holes. For some time now, astronomers have believed that in order to form a black hole at the end of its life cycle, a star would have to be massive enough to cause a supernova. But as the team observed, it doesn’t make sense that a star would blow off its outer layers and still have enough mass left over to form a massive black hole.

As Christopher Kochanek – a professor of astronomy at The Ohio State University, the Ohio Eminent Scholar in Observational Cosmology and a co-author of the team’s study – explained:

“The typical view is that a star can form a black hole only after it goes supernova. If a star can fall short of a supernova and still make a black hole, that would help to explain why we don’t see supernovae from the most massive stars.”

This information is also important as far as the study of gravitational waves goes. In February of 2016, scientists at the Laser Interferometer Gravitational-wave Observatory (LIGO) announced the first detection of this strange phenomena, which were apparently generated by a massive black hole. If in fact massive black holes form from failed supernova, it would help astronomers to track down the sources more easily.

Be sure to check out this video of the observations made of this failed SN and black hole:

Further Reading: NASA, MNRAS

 

We Have More Details on the Outermost Trappist-1 Planet!

The announcement of a seven-planet system around the star TRAPPIST-1 earlier this year set off a flurry of scientific interest. Not only was this one of the largest batches of planets to be discovered around a single star, the fact that all seven were shown to be terrestrial (rocky) in nature was highly encouraging. Even more encouraging was the fact that three of these planets were found to be orbiting with the star’s habitable zone.

Since that time, astronomers have been seeking to learn all they can about this system of planets. Aside from whether or not they have atmospheres, astronomers are also looking to learn more about their orbits and surface conditions. Thanks to the efforts of a University of Washington-led international team of astronomers, we now have an accurate idea of what conditions might be like on its outermost planet – TRAPPIST-1h.

Continue reading “We Have More Details on the Outermost Trappist-1 Planet!”

Stunning View of the Crab Nebula Just Got Five Times Better

Images of the Crab Nebula are always a treat because it has such intriguing and varied structure. Also, just knowing that this stellar explosion was witnessed and recorded by people on Earth more than 900 years ago (with the supernova visible to the naked eye for about two years) gives this nebula added fascination.

A new image just might be the biggest Crab Nebula treat ever, as five different observatories combined forces to create an incredibly detailed view, with stunning details of the nebula’s interior region.

Data from the five telescopes span nearly the entire breadth of the electromagnetic spectrum, from radio waves seen by the Karl G. Jansky Very Large Array (VLA) to the powerful X-ray glow as seen by the orbiting Chandra X-ray Observatory. And, in between that range of wavelengths, the Hubble Space Telescope’s crisp visible-light view, and the infrared perspective of the Spitzer Space Telescope.

Astronomers have produced a highly detailed image of the Crab Nebula, by combining data from telescopes spanning nearly the entire breadth of the electromagnetic spectrum. This image combines data from five different telescopes: the VLA (radio) in red; Spitzer Space Telescope (infrared) in yellow; Hubble Space Telescope (visible) in green; XMM-Newton (ultraviolet) in blue; and Chandra X-ray Observatory (X-ray) in purple. Credit: NASA, ESA, G. Dubner (IAFE, CONICET-University of Buenos Aires) et al.; A. Loll et al.; T. Temim et al.; F. Seward et al.; VLA/NRAO/AUI/NSF; Chandra/CXC; Spitzer/JPL-Caltech; XMM-Newton/ESA; and Hubble/STScI.

The Crab is 6,500 light-years from Earth and spans about 10 light-years in diameter. The supernova that created it was first witnessed in 1054 A. D. At its center is a super-dense neutron star that is as massive as the Sun but with only the size of a small town. This pulsar rotates every 33 milliseconds, shooting out spinning lighthouse-like beams of radio waves and light. The pulsar can be seen as the bright dot at the center of the image.

Scientists say the nebula’s intricate shape is caused by a complex interplay of the pulsar, a fast-moving wind of particles coming from the pulsar, and material originally ejected by the supernova explosion and by the star itself before the explosion.

A new x-ray image of the Crab Nebula by the Chandra X-ray Observatory. Credit: X-ray: NASA/CXC/SAO.

For this new image, the VLA, Hubble, and Chandra observations all were made at nearly the same time in November of 2012. A team of scientists led by Gloria Dubner of the Institute of Astronomy and Physics (IAFE), the National Council of Scientific Research (CONICET), and the University of Buenos Aires in Argentina then made a thorough analysis of the newly revealed details in a quest to gain new insights into the complex physics of the object. They are reporting their findings in the Astrophysical Journal (see the pre-print here).

About the central region, the team writes, “The new HST NIR [near infrared] image of the central region shows the well-known elliptical torus around the pulsar, composed of a series of concentric narrow features of variable intensity and width… The comparison of the radio and the X-ray emission distributions in the central region suggests the existence of a double-jet system from the pulsar, one detected in X-rays and the other in radio. None of them starts at the pulsar itself but in its environs.”

“Comparing these new images, made at different wavelengths, is providing us with a wealth of new detail about the Crab Nebula. Though the Crab has been studied extensively for years, we still have much to learn about it,” Dubner said.

A multi-wavelength layout of the Crab Nebula. Credit: (Credit: X-ray: NASA/CXC/SAO; Optical: NASA/STScI; Infrared: NASA/JPL/Caltech; Radio: NSF/NRAO/VLA; Ultraviolet: ESA/XMM-Newton).

Read the team’s paper: Morphological properties of the Crab Nebula: a detailed multiwavelength study based on new VLA, HST, Chandra and XMM-Newton images
Sources: Chandra, Hubble

Deepest X-ray Image Ever Made Contains Mysterious Explosion

For over sixty years, astronomers have been exploring the Universe for x-ray sources. Known to be associated with stars, clouds of super heated gas, interstellar mediums, and destructive events, the detection of cosmic x-rays is challenging work. In recent decades, astronomers have been benefited immensely from by the deployment of orbital telescopes like the Chandra X-ray Observatory.

Since it was launched on July 23rd, 1999, Chandra has been NASA’s flagship mission for X-ray astronomy. And this past week (on Thurs. March 30th, 2017), the Observatory accomplished something very impressive. Using its suite of advanced instruments, the observatory captured a mysterious flash coming from deep space. Not only was this the deepest X-ray source ever observed, it also revealed what could be an entirely new phenomenon.

Located in the region of the sky known as the Chandra Deep Field-South (CDF-S), this X-ray emission source appeared to have come from a small galaxy located approximately 10.7 billion light-years from Earth. It also had some remarkable properties, producing more energy in the space of a few minutes that all the stars in the galaxy combined.

Artist illustration of the Chandra X-ray Observatory, the most sensitive X-ray telescope ever built. Credit: NASA/CXC/NGST

Originally detected in 2014 by a team of researchers from Penn State University and the Pontifical Catholic University of Chile in Santiago, Chile, this source was not even detected in the X-ray band at first. However, it quickly caught the team’s attention as it erupted and became 1000 brighter in the space of a few hours. At this point, the researchers began gathering data using Chandra’s Advanced CCD Imaging Spectronomer.

A day after the flare-up, the X-ray source had faded to the point that Chandra was no longer able to detect it. As Niel Brandt – the Verne M. Willaman Professor of Astronomy and Astrophysics at Penn State and part of the team that first observed it – described the discovery in a Penn State press release:

“This flaring source was a wonderful surprise bonus that we accidentally discovered in our efforts to explore the poorly understood realm of the ultra-faint X-ray universe. We definitely ‘lucked out’ with this find and now have an exciting new transient phenomenon to explore in future years.”

Thousands of hours of legacy data from the Hubble and Spitzer Space Telescopes was then consulted in order to determine the location of the CDF-S X-ray source. And though scientists were able to determine that the image of the X-ray source placed it beyond any that had been observed before, they are not entirely clear as to what could have caused it.

X-ray (left) and optical (right) images of the space around the X-ray source, made with Chandra and the Hubble Space Telescope, respectively. Credit: NASA/CXC/F. Bauer et al.

On the one hand, it could be the result of some sort of destructive event, or something scientists have never before seen. The reason for this has to do with the fact that X-ray bursts also come with a gamma-ray burst (GRB), which appears to be missing here. Essentially, GRBs are jetted explosions that are triggered by the collapse of a massive star or by the merger of two neutron stars (or a neutron star with a black hole).

Because of this, three possible explanations have been suggested. In the first, the CDF-S X-ray source is indeed the result of a collapsing star or merger, but the resulting jets are not pointed towards Earth. In the second, the same scenario is responsible for the x-ray source, but the GRB lies beyond the small galaxy. The third possible explanation is that the event was caused by a medium-sized black hole shredding a white dwarf star.

Unfortunately, none of these explanations seem to fit the data. However, these research team also noted that these possibilities are not that well understood, since none have been witnessed in the Universe. As Franz Bauer – an astronomer from the Pontifical Catholic University of Chile – said: “Ever since discovering this source, we’ve been struggling to understand its origin. It’s like we have a jigsaw puzzle but we don’t have all of the pieces.”

Not only has Chandra not observed any other X-ray sources like this one during the 17 years it has surveyed the CDF-S region, but no similar events have been observed by the space telescope anywhere in the Universe during its nearly two decades of operation. On top of that, this event was brighter, more short-lived, and occurred in a smaller, younger host galaxy than other unexplained X-ray sources.

Still image of the X-ray source observed by Chandra, showing the captured flare up at bottom Credit: NASA/CXC/Pontifical Catholic Univ./F.Bauer et al.

From all of this, the only takeaway appears to be that the event was likely the result of a cataclysmic event, like a neutron star or a white dwarf being torn apart. But the fact that none of the more plausible explanations seem to account for it’s peculiar characteristics would seem to suggest that astronomers may have witnessed an entirely new kind of cataclysmic event.

The team’s study – “A New, Faint Population of X-ray Transient“- is available online and will be published in the June 2017 issue of the Monthly Notices of the Royal Astronomical Society. In the meantime, astronomers will be sifting through the data acquired by Chandra and other X-ray observatories – like the ESA’s XMM-Newton and NASA’s Swift Gamma-Ray Burst Mission – to see if they can find any other instances of this kind of event.

And of course, future surveys conducted using Chandra and next-generation X-ray telescopes will also be on the lookout for these kind of short-lived, high-energy X-ray bursts. It’s always good when the Universe throws us a curve ball. Not only does it show us that we have more to learn, but it also teaches us that we must never grow complacent in our theories.

Be sure to check out this animation of the CDF-S X-ray source too, courtesy of the Chandra X-ray Observatory:

Further Reading:  Chandra, PennState

Strange Loner Planet Gets Astronomers’ Attention

In the hunt for exoplanets, some rather strange discoveries have been made. Beyond our Solar System, astronomers have spotted gas giants and terrestrial planets that appear to be many orders of magnitude larger than what we are used to (aka. “Super-Jupiters” and “Super-Earths”). And in some cases, it has not been entirely clear what our instruments have been detecting.

For instance, in some cases, astronomers have not been sure if an exoplanet candidate was a super-Jupiter or a brown dwarf. Not only do these substellar-mass stars fall into the same temperature range as massive gas giants, they also share many of the same physical properties. Such was the conundrum addressed by an international team of scientists who recently conduced a study of the object known as CFBDSIR 2149-0403.

Located between 117 and 143 light-years from Earth, this mysterious object is what is known as a “free-floating planetary mass object”. It was originally discovered in 2012 by a team of French and Canadian astronomers led by Dr. Phillipe Delorme of the University Grenoble Alpes using the Canada-France Brown Dwarfs Survey – a near infrared sky survey with the Canada-France Hawaii Telescope at Mauna Kea.

The Canada France Hawaii Telescope, near the summit of Mauna Kea, Hawaii. Credit: cfht.hawaii.edu/

The existence of this object was then confirmed using data by the Wide-field Infrared Survey Explorer (WISE), and was believed at the time to be part of a group of stars known as the AB Doradus Moving Group (30 stars that are moving through space). The data collected on this object placed its mass at between 4 and 7 Jupiter masses, its age at 20 to 200 million years, and its surface temperature at about 650-750 K.

This was the first time that such an object had constraints placed upon its mass and age using spectral data. However, questions remained about its true nature – whether it was a low mass, high-metallicity brown dwarf or a isolated planetary mass. For the sake of their study, Delorme and the international team conducted a multi-wavelength, multi-instrument observational characterization of CFBDSIR 2149-0403.

This consisted of x-ray data from the X-Shooter instrument on the ESO’s Very Large Telescope (VLT), near-infrared data from the VLT’s Hawk-1 instrument, and infrared data from the Spitzer Space Telescope and the CFHT’s Wide-field InfraRed Camera (WIRCam). As Delorme told Tomasz Nowakowski of Phys.org:

“The X-Shooter data enabled a detailed study of the physical properties of this object. However, all the data presented in the paper is really necessary for the study, especially the follow-up to obtain the parallax of the object, as well as the Spitzer photometry. Together, they enable us to get the bolometric flux of the object, and hence constraints that are almost independent from atmosphere model assumptions.”

An artist’s conception of a T-type brown dwarf star. Credit: Wikimedia Commons/Tyrogthekreeper

From the combined data, they were able to characterize the absolute flux of the CFBDSIR 2149-0403, obtain readings on its spectrum, and even determine the radial velocity of the object. They were therefore able to determine that it not likely a member of a moving population of stars, as was previously expected.

“We now reject our initial hypothesis that CFBDSIR 2149-0403 would be a member of the AB Doradus moving group,” said Delorme. “This removes the most robust age constraint we had. Though determining that certainly improved our knowledge of the object it also made it more difficult to study, by adding age as a free parameter.”

As for what it is, they narrowed that down to one of two possibilities. Basically, it could be a planetary-mass object with a mass of between 2 and 13 Jupiters that is less than 500 million years in age, or a high metallicity brown dwarf that is between 2 and 40 Jupiter masses and two to three billion years in age. Ultimately, they acknowledge that this uncertainty is due to the fact that our theoretical understanding of cool, low-gravity, and metallicity-enhanced bodies is not robust enough yet.

Much of this has to do with the fact that brown dwarfs and super gas giants have common physical parameters that produce very similar effects in the spectra of their atmospheres. But as astronomers gain more of an understanding of planetary formation, which is made possible by the discovery of so many extra-solar planetary systems, we might just find where the line between the smallest of stars and the largest of gas giants is drawn.

Further Reading: arXiv, Phys.org

Huge News, Seven Earth-Sized Worlds Orbiting a Red Dwarf, Three in the Habitable Zone

Illustration showing the possible surface of TRAPPIST-1f, one of the newly discovered planets in the TRAPPIST-1 system. Credits: NASA/JPL-Caltech

In what is surely the biggest news since the hunt for exoplanets began, NASA announced today the discovery of a system of seven exoplanets orbiting the nearby star of TRAPPIST-1. Discovered by a team of astronomers using data from the TRAPPIST telescope in Chile and the Spitzer Space Telescope, this find is especially exciting since all of these planets are believed to be Earth-sized and terrestrial (i.e. rocky).

But most exciting of all is the fact that three of these rocky exoplanets orbit within the star’s habitable zone (aka. “Goldilocks Zone”). This means, in effect, that these planets are capable of having liquid water on their surfaces and could therefore support life. As far as extra-solar planet discoveries go, this is without precedent, and the discovery heralds a new age in the search for life beyond our Solar System.

Continue reading “Huge News, Seven Earth-Sized Worlds Orbiting a Red Dwarf, Three in the Habitable Zone”

Space Jellyfish Show Types Of Pulsar Wind Nebulas

Since they were first discovered in the late 1960s, pulsars have continued to fascinate astronomers. Even though thousands of these pulsing, spinning stars have been observed in the past five decades, there is much about them that continues to elude us. For instance, while some emit both radio and gamma ray pulses, others are restricted to either radio or gamma ray radiation.

However, thanks to a pair of studies from two international teams of astronomers, we may be getting closer to understanding why this is. Relying on data collected by the Chandra X-ray Observatory of two pulsars (Geminga and B0355+54), the teams was able to show how their emissions and the underlying structure of their nebulae (which resemble jellyfish) could be related.

These studies, “Deep Chandra Observations of the Pulsar Wind Nebula Created by PSR B0355+54” and “Geminga’s Puzzling Pulsar Wind Nebula” were published in The Astrophysical Journal. For both, the teams relied on x-ray data from the Chandra Observatory to examine the Geminga and B0355+54 pulsars and their associated pulsar wind nebulae (PWN).

An artist’s impression of an accreting X-ray millisecond pulsar. Credit: NASA/Goddard Space Flight Center/Dana Berry

Located 800 and 3400 light years from Earth (respectively), the Geminga and B0355+54 pulsars are quite similar. In addition to having similar rotational periods (5 times per second), they are also about the same age (~500 million years). However, Geminga emits only gamma-ray pulses while B0355+54 is one of the brightest known radio pulsars, but emits no observable gamma rays.

What’s more, their PWNs are structured quite differently. Based on composite images created using Chandra X-ray data and Spitzer infrared data, one resembles a jellyfish whose tendrils are relaxed while the other looks like a jellyfish that is closed and flexed. As Bettina Posselt – a senior research associate in the Department of Astronomy and Astrophysics at Penn State, and the lead author on the Geminga study – told Universe Today via email:

“The Chandra data resulted in two very different X-ray images of the pulsar wind nebulae around the pulsars Geminga and PSR B0355+54. While Geminga has a distinct three-tail structure, the image of PSR B0355+54 shows one broad tail with several substructures.”

In all likelihood, Geminga’s and B0355+54 tails are narrow jets emanating from the pulsar’s spin poles. These jets lie perpendicular to the donut-shaped disk (aka. a torus) that surrounds the pulsars equatorial regions. As Noel Klingler, a graduate student at the George Washington University and the author of the B0355+54 paper, told Universe Today via email:

“The interstellar medium (ISM) isn’t a perfect vacuum, so as both of these pulsars plow through space at hundreds of kilometers per second, the trace amount of gas in the ISM exerts pressure, thus pushing back/bending the pulsar wind nebulae behind the pulsars, as is shown in the images obtained by the Chandra X-ray Observatory.”

Their apparent structures appear to be due to their disposition relative to Earth. In Geminga’s case, the view of the torus is edge-on while the jets point out to the sides. In B0355+54’s case, the torus is seen face-on while the jets points both towards and away from Earth. From our vantage point, these jets look like they are on top of each other, which is what makes it look like it has a double tail. As Posselt describes it:

“Both structures can be explained with the same general model of pulsar wind nebulae. The reasons for the different images are (a) our viewing perspective, and (b) how fast and where to the pulsar is moving. In general, the observable structures of such pulsar wind nebulae can be described with an equatorial torus and polar jets. Torus and Jets can be affected (e.g., bent jets) by the “head wind” from the interstellar medium the pulsar is moving in. Depending on our viewing angle of the torus, jets and the movement of the pulsar, different pictures are detected by the Chandra X-ray observatory. Geminga is seen “from the side” (or edge-on with respect to the torus) with the jets roughly located in the plane of the sky  while for B0355+54 we look almost directly to one of the poles.”

This orientation could also help explain why the two pulsars appear to emit different types of electromagnetic radiation. Basically, the magnetic poles – which are close to their spin poles – are where a pulsar’s radio emissions are believed to come from. Meanwhile, gamma rays are believed to be emitted along a pulsar’s spin equator, where the torus is located.

“The images reveal that we see Geminga from edge-on (i.e., looking at its equator) because we see X-rays from particles launched into the two jets (which are initially aligned with the radio beams), which are pointed into the sky, and not at Earth,” said Klingler. “This explains why we only see Gamma-ray pulses from Geminga.  The images also indicate that we are looking at B0355+54 from a top-down perspective (i.e., above one of the poles, looking into the jets).  So as the pulsar rotates, the center of the radio beam sweeps across Earth, and we detect the pulses;  but the  gamma-rays are launched straight out from the pulsar’s equator, so we don’t see them from B0355.”

An all-sky view from the Fermi Gamma-ray Space Telescope, showing the position of Geminga in the Milky Way. Credit : NASA/DOE/International LAT Team.

“The geometrical constraints on each pulsar (where are the poles and the equator) from the pulsar wind nebulae help to explain findings regarding the radio and gamma-ray pulses of these two neutron stars,” said Posselt. “For example, Geminga appears radio-quiet (no strong radio pulses) because we don’t have a direct view to the poles and pulsed radio emission is thought to be generated in a region close to the poles. But Geminga shows strong gamma-ray pulsations, because these are not produced at the poles, but closer to the equatorial region.”

These observations were part of a larger campaign to study six pulsars that have been seen to emit gamma-rays. This campaign is being led by Roger Romani of Stanford University, with the collaboration of astronomers and researchers from GWU (Oleg Kargaltsev), Penn State University (George Pavlov), and Harvard University (Patrick Slane).

Not only are these studies shedding new light on the properties of pulsar wind nebulae, they also provide observational evidence to help astronomers create better theoretical models of pulsars. In addition, studies like these – which examine the geometry of pulsar magnetospheres – could allow astronomers to better estimate the total number of exploded stars in our galaxy.

By knowing the range of angles at which pulsars are detectable, they should be able to better estimate the amount that are not visible from Earth. Yet another way in which astronomers are working to find the celestial objects that could be lurking in humanity’s blind spots!

Further Reading: Chandra X-Ray Observatory

Farthest Galaxy Ever Seen Viewed By Hubble Telescope

Since it was first launched in 1990, the Hubble Space Telescope has provided people all over the world with breathtaking views of the Universe. Using its high-tech suite of instruments, Hubble has helped resolve some long-standing problems in astronomy, and helped to raise new questions. And always, its operators have been pushing it to the limit, hoping to gaze farther and farther into the great beyond and see what’s lurking there.

And as NASA announced with a recent press release, using the HST, an international team of astronomers just shattered the cosmic distance record by measuring the farthest galaxy ever seen in the universe. In so doing, they have not only looked deeper into the cosmos than ever before, but deeper into it’s past. And what they have seen could tell us much about the early Universe and its formation.

Due to the effects of special relativity, astronomers know that when they are viewing objects in deep space, they are seeing them as they were millions or even billions of years ago. Ergo, an objects that is located 13.4 billions of light-years away will appear to us as it was 13.4 billion years ago, when its light first began to make the trip to our little corner of the Universe.

An international team of scientists has used the Hubble Space Telescope to spectroscopically confirm the farthest galaxy to date. Credits: NASA/ESA/B. Robertson (University of California, Santa Cruz)/A. Feild (STScI)
An international team of scientists has used the Hubble Space Telescope to spectroscopically confirm the farthest galaxy to date. Credits: NASA/ESA/B. Robertson (University of California, Santa Cruz)/A. Feild (STScI)

This is precisely what the team of astronomers witnessed when they gazed upon GN-z11, a distant galaxy located in the direction of the constellation of Ursa Major. With this one galaxy, the team of astronomers – which includes scientists from Yale University, the Space Telescope Science Institute (STScI), and the University of California – were able to see what a galaxy in our Universe looked like just 400 million years after the Big Bang.

Prior to this, the most distant galaxy ever viewed by astronomers was located 13.2 billion light years away. Using the same spectroscopic techniques, the Hubble team confirmed that GN-z11 was nearly 200 million light years more distant. This was a big surprise, as it took astronomers into a region of the Universe that was thought to be unreachable using the Hubble Space Telescope.

In fact, astronomers did not suspect that they would be able to probe this deep into space and time without using Spitzer, or until the deployment the James Webb Space Telescope – which is scheduled to launch in October 2018. As Pascal Oesch of Yale University, the principal investigator of the study, explained:

“We’ve taken a major step back in time, beyond what we’d ever expected to be able to do with Hubble. We see GN-z11 at a time when the universe was only three percent of its current age. Hubble and Spitzer are already reaching into Webb territory.”

The Hubble Space Telescope in 1997, after its first servicing mission. It's about 552 km (343m) above Earth. Image: NASA
The Hubble Space Telescope in 1997, after its first servicing mission. Credit: NASA

In addition, the findings also have some implications for previous distance estimates. In the past, astronomers had estimated the distance of GN-z11 by relying on Hubble and Spitzer’s color imaging techniques. This time, they relied on Hubble’s Wide Field Camera 3 to spectroscopically measure the galaxies redshift for the first time. In so doing, they determined that GN-z11 was farther way than they thought, which could mean that some particularly bright galaxies who’s distanced have been measured using Hubble could also be farther away.

The results also reveal surprising new clues about the nature of the very early universe. For starters, the Hubble images (combined with data from Spitzer) showed that GN-z11 is 25 times smaller than the Milky Way is today, and has just one percent of our galaxy’s mass in stars. At the same time, it is forming stars at a rate that is 20 times greater than that of our own galaxy.

As Garth Illingworth – one of the team’s investigator’s from the University of California, Santa Cruz – explained:

“It’s amazing that a galaxy so massive existed only 200 million to 300 million years after the very first stars started to form. It takes really fast growth, producing stars at a huge rate, to have formed a galaxy that is a billion solar masses so soon. This new record will likely stand until the launch of the James Webb Space Telescope.”

Last, but not least, they provide a tantalizing clue as to what future missions – like the James Webb Space Telescope – will be finding. Once deployed, astronomers will likely be looking ever farther into space, and farther into the past. With every step, we are closing in on seeing what the very first galaxies that formed in our Universe looked like.

Further Reading: NASA

Why Can’t We See the Center of the Milky Way?

For millennia, human beings have stared up at the night sky and stood in awe of the Milky Way. Today, stargazers and amateur astronomers continue in this tradition, knowing that what they are witnessing is in fact a collection of hundreds of millions of stars and dust clouds, not to mention billions of other worlds.

But one has to wonder, if we can see the glowing band of the Milky Way, why can’t we see what lies towards the center of our galaxy? Assuming we are looking in the right direction, shouldn’t we able to see that big, bright bulge of stars with the naked eye? You know the one I mean, it’s in all the pictures!

Unfortunately, in answering this question, a number of reality checks have to be made. When it is dark enough, and conditions are clear, the dusty ring of the Milky Way can certainly be discerned in the night sky. However, we can still only see about 6,000 light years into the disk with the naked eye, and relying on the visible spectrum. Here’s a rundown on why that is.

Size and Structure:

First of all, the sheer size of our galaxy is enough to boggle the mind. NASA estimates that the Milky Way is between 100,000 – 120,000 light-years in diameter – though some information suggests it may be as much as 150,000 – 180,000 light-years across. Since one light year is about 9.5 x 1012km, this makes the diameter of the Milky Way galaxy approximately 9.5 x 1017 – 1.14 x 1018 km in diameter.

To put that in layman’s terms, that 950 quadrillion (590 quadrillion miles) to 1.14 quintillion km (7oo septendecillion miles). The Milky Way is also estimated to contain 100–400 billion stars, (although that could be as high as one trillion), and may have as many as 100 billion planets.

At the center, measuring approx. 10,000 light-years in diameter, is the tightly-packed group of stars known as the “bulge”. At the very center of this bulge is an intense radio source, named Sagittarius A*, which is likely to be a supermassive black hole that contains 4.1 million times the mass of our Sun.

We, in our humble Solar System, are roughly 28,000 light years away from it. In short, this region is simply too far for us to see with the naked eye. However, there is more to it than just that…

Radio image of the night sky. Credit: Max Planck Institute for Radio Astronomy, generated by Glyn Haslam.

Low Surface Brightness:

In addition to being a spiral barred galaxy, the Milky Way is what is known as a Low Surface Brightness (LSB) galaxy –  a classification that refers to galaxies where their surface brightness is, when viewed from Earth, at least one magnitude lower than the ambient night sky. Essentially, this means that the sky needs to be darker than about 20.2 magnitude per square arcsecond in order for the Milky Way to be seen.

This makes the Milky Way difficult to see from any location on Earth where light pollution is common – such as urban or suburban locations – or when stray light from the Moon is a factor. But even when conditions are optimal, there still only so much we can see with the naked eye, for reasons that have much to do with everything that lies between us and the galactic core.

Dust and Gas:

Though it may not look like it to the casual observer, the Milky Way is full of dust and gas. This matter is known as as the interstellar medium, a disc that makes up a whopping 10-15% of the luminous/visible matter in our galaxy and fills the long spaces in between the stars. The thickness of the dust deflects visible light (as is explained here), leaving only infrared light to pass through the dust.

"This dazzling infrared image from NASA's Spitzer Space Telescope shows hundreds of thousands of stars crowded into the swirling core of our spiral Milky Way galaxy. In visible-light pictures, this region cannot be seen at all because dust lying between Earth and the galactic center blocks our view. Credit: NASA/JPL-Caltech
This dazzling infrared image from NASA’s Spitzer Space Telescope showing hundreds of thousands of stars crowded into the swirling core of our spiral Milky Way galaxy. Credit: NASA/JPL-Caltech

This makes infrared telescopes like the Spitzer Space Telescope extremely valuable tools in mapping and studying the galaxy, since it can peer through the dust and haze to give us extraordinarily clear views of what is going on at the heart of the galaxy and in star-forming regions. However, when looking in the visual spectrum, light from Earth, and the interference effect of dust and gas limit how far we can see.

Limited Instrumentation:

Astronomers have been staring up at the stars for thousands of years. However, it was only in comparatively recent times that they even knew what they were looking at. For instance, in his book Meteorologica, Aristotle (384–322 BC) wrote that the Greek philosophers Anaxagoras (ca. 500–428 BCE) and Democritus (460–370 BCE) had proposed that the Milky Way might consist of distant stars.

However, Aristotle himself believed the Milky Way was be caused by “the ignition of the fiery exhalation of some stars which were large, numerous and close together” and that these ignitions takes place in the upper part of the atmosphere. Like many of Aristotle’s theories, this would remain canon for western scholars until the 16th and 17th centuries, at which time, modern astronomy would begin to take root.

Meanwhile, in the Islamic world, many medieval scholars took a different view. For example, Persian astronomer Abu Rayhan al-Biruni (973–1048) proposed that the Milky Way is “a collection of countless fragments of the nature of nebulous stars”. Ibn Qayyim Al-Jawziyya (1292–1350) of Damascus similarly proposed that the Milky Way is “a myriad of tiny stars packed together in the sphere of the fixed stars” and that these stars are larger than planets.

Persian astronomer Nasir al-Din al-Tusi (1201–1274) also claimed in his book Tadhkira that: “The Milky Way, i.e. the Galaxy, is made up of a very large number of small, tightly clustered stars, which, on account of their concentration and smallness, seem to be cloudy patches. Because of this, it was likened to milk in color.”

Despite these theoretical breakthroughs, it was not until 1610, when Galileo Galilei turned his telescope towards the heavens, that proof existed to back up these claims. With the help of telescopes, astronomers realized for the first time that there were many, many more stars in the sky than the ones we can see, and that all of the ones that we can see are a part of the Milky Way.

Over a century later, William Herschel created the first theoretical diagram of what the Milky Way (1785) looked like. In it, he described the shape of the Milky Way as a large, cloud-like collection of stars, and claimed the Solar System was close to the center. Though erroneous, this was the first attempt at hypothesizing what our cosmic backyard looked like.

It was not until the 20th century that astronomers were able to get an accurate picture of what our Galaxy actually looks like. This began with astronomer Harlow Shapely measuring the distributions and locations of globular star clusters. From this, he determined that the center of the Milky Way was 28,000 light years from Earth, and that the center was a bulge, rather than a flat area.

This annotated artist's conception illustrates our current understanding of the structure of the Milky Way galaxy. Image Credit: NASA
This annotated artist’s conception illustrates our current understanding of the structure of the Milky Way galaxy. Image Credit: NASA

In 1923, astronomer Edwin Hubble used the largest telescope of his day at the Mt. Wilson Observatory near Pasadena, Calif., to observe galaxies beyond our own. By observing what spiral galaxies look like throughout the universe, astronomers and scientists were able to get an idea of what our own looks like.

Since that time, the ability to observe our galaxy through multiple wavelengths (i.e. radio waves, infrared, x-rays, gamma-rays) and not just the visible spectrum has helped us to get an even better picture. In addition, the development of space telescopes – such as Hubble, Spitzer, WISE, and Kepler – have been instrumental in allowing us to make observations that are not subject to interference from our atmosphere or meteorological conditions.

But despite our best efforts, we are still limited by a combination of perspective, size, and visibility barriers. So far, all pictures that depict our galaxy are either artist’s renditions or pictures of other spiral galaxies. Until quite recently in our history, it was very difficult for scientists to gauge what the Milky Way looks like, mainly because we’re embedded inside it.

To get an actual view of the Milky Way Galaxy, several things would need to happen. First, we would need a camera that worked in space that had a wide field of view (aka. Hubble, Spitzer, etc). Then we’d need to fly that camera to a spot that’s roughly 100,000 light years above the Milky Way and point it back at Earth. With our current propulsion technology, that would take 2.2 billion years to accomplish.

Milky Way in infrared. Image credit: COBE
Milky Way in infrared. Image credit: COBE

Fortunately, as noted already, astronomers have a few additional wavelengths they can use to see into the galaxy, and these are making much more of the galaxy visible. In addition to seeing more stars and more star clusters, we’re able to see more of the center of our Galaxy as well, which includes the supermassive black hole that has been theorized as existing there.

For some time, astronomers have had name for the region of sky that is obscured by the Milky Way – the “Zone of Avoidance“. Back in the days when astronomers could only make visual observations, the Zone of Avoidance took up about 20% of the night sky. But by observing in other wavelengths, like infrared, x-ray, gamma rays, and especially radio waves, astronomers can see all but about 10% of the sky. What’s on the other side of that 10% is mostly a mystery.

In short, progress is being made. But until such time that we can send a ship beyond our Galaxy that can take snapshots and beam them back to us, all within the space of our own lifetimes, we’ll be dependent on what we can observe from the inside.

We have many interesting articles on the Milky Way here at Universe Today. For example, here’s What is the Milky Way? And here’s an article on why it’s called The Milky Way, how big it is, why it rotates, and what the closest galaxy is to it.

And here are 10 Facts About the Milky Way. And be sure to check out our Guide to Space section on the Milky Way.

And be to sure to check out Universe Today’s interview with Dr. Andrea Ghez, Professor of Astronomy at UCLA, talking about what is at the center of our Galaxy.

How Long Will Our Spacecraft Survive?

There are many hazards out there, eager to disrupt and dismantle the mighty machines we send out into space. How long can they survive to perform their important missions?

Every few months, an eager new spacecraft arrives on the launch pad, ready for its date with destiny. If we don’t blow it all to bits with a launch vehicle failure, it’ll be gently placed into orbit with surgical precision. Then it’ll carry out a noble mission of exploring the Solar System, analyzing the Earth, or ensuring we have an infinite number of radio stations in our cars, allowing us to never be satisfied with any of them.

Space is hostile. Not just to fragile hu-mans, but also to our anthropomorphized Number Five is alive robotic spacecraft which we uncaringly send to do our bidding. There are many hazards out there, eager to disrupt and dismantle our stalwart electronic companions. Oblivion feeds voraciously on our ever trusting space scouts and their tiny delicate robotic hearts, so many well before their time.

How long have they got? How long will our spacecraft survive as we cast them on their suicide missions to “go look at stuff on behalf of the mighty human empire”? When spacecraft are hurled into the void, all mission planners know they’re living on borrowed time.

The intrepid Mars Exploration Rovers, Spirit and Opportunity, were only expected to operate for 3 months. NASA’s Spitzer Space Telescope carried a tank of expendable helium coolant to let it see the dimmest objects in the infrared spectrum.

Sometimes the spacecraft wear down for unexpected reasons, like electronic glitches, or parts wearing out. Hubble was equipped with rotating gyroscopes that eventually wore out over time, making it more difficult to steer at its targets, and only an intervention by rescue and repair allowed the mission to keep going.

In general, a spacecraft is expected to last a few months to a few years. Spirit and Opportunity only had a planned mission of 3 months. It took Spirit more than 6 dauntless years to finally succumb to the hostile Martian environment. Opportunity is still kicking more than a decade later, thanks to some very careful driving and gusts of Martian wind clearing off its solar panels which didn’t surprise anybody.

Artist impression of Rosetta and Asteroid 2867 Steins. Credit:  ESA
Artist impression of Rosetta and Asteroid 2867 Steins. Credit: ESA

ESA’s Rosetta spacecraft needed to survive for 10 years in a dormant state before its encounter with Comet 67/P. It’s expected to last until the end of 2015. Then its orbit will carry it too far from the Sun to operate its solar panels, then it’ll go to sleep one last time.

As a testament to luck and remarkable feats of engineering, some survive much longer than anyone ever expected. NASA’s Voyager Spacecraft, launched in 1977, are still going and communicating with Earth. It’s believed they’ll survive until 2025, when their radioisotope thermoelectric generators stop producing power.

At which point they’ll return to the Earth at the heart of a massive alien spacecraft and scare the bejeebus out of us.

… And I know what you’re thinking. Once our spacecraft stop functioning, they’ll still exist. Perhaps getting close enough to another source of solar energy to start transmitting again.

So, how long will our spacecraft hold together in something roughly robot-probe shaped? Any spacecraft orbiting a planet or Moon won’t last long geologically before they’re given a rocky kiss of death with help from a big group hug from gravity.

This might take a decade, a hundred years or a million. Eventually, that spacecraft is racing towards a well distributed grave on its new home.

Solar Dynamics Observatory. Credit: NASA
Solar Dynamics Observatory. Credit: NASA

A spacecraft that’s orbiting the Sun should last much longer. However, a gravitational threesome with a planet or large asteroid could drag it into a solar death spiral or hurl it into a planet. There are asteroids whipping around from the formation of the Solar System, and they haven’t crashed into anything… yet.

A lucky spacecraft might last hundreds of millions, or even billions of years. Our little robot friends that leave the gravitational pull of the Solar System have a chance of making it for the long haul.

Once they’re out in interstellar space, there will be very few micrometeorites to punch little holes in them. Unless they happen to run into another star – and that’s very unlikely – they’ll travel through space until they’re worn away over billions of years, and who knows what that means for future alien archaeology students. The golden records on the Voyager spacecraft were designed to still be playable for a billion years in space.

Artist's concept of NASA's Voyager spacecraft. Image credit: NASA/JPL-Caltech
Artist’s concept of NASA’s Voyager spacecraft. Image credit: NASA/JPL-Caltech

It’s tough to keep a spacecraft operating in space. It’s a really hostile place, ready to fry their little silicon brains, scuttle them with a micrometeorite, or just erode them away over an incomprehensible length of time.

Are horrible space agency fiends tossing our trusting big eyed robot pals to their doom on one-way missions into the abyss? Don’t worry viewers, I have it on good authority this is what the robots want.

Beloved astronaut Chris Hadfield said if Voyager had stayed at home where it’s safe, it would’ve been sad forever, because it never would have discovered things. I think he’s right, Voyager is as happy as it could be exploring the parts of our Universe the rest of us aren’t able to go and see for ourselves.

What’s your favorite spacecraft survivor story? Tell us in the comments below.