Tag Archives: brown dwarf

Astronomers find two failed stars wandering the universe together

A team of researchers from the University of Bern has discovered a very different binary system 450 light-years from Earth. The system — CFHTWIR-Oph 98 or Oph 98 for short — has twin occupants that appeared at first sight to be exoplanets existing in a star-less system. A deeper examination has revealed that they are brown dwarfs — Oph 98 A and Oph 98 B respectively — astronomical objects that are similar to stars but smaller and cooler.

This artist’s illustration represents a couple of planetary-mass brown dwarfs Ophiuchus 98. As they are very young, they are still evolving in the molecular clouds that saw their birth. (University of Bern, Illustration: Thibaut Roger)

These brown dwarfs wander the galaxy together, orbiting each other at an incredibly large distance equivalent to 200 times the distance between Earth and the Sun.

The discovery of the curious Oph 98 system by the research team led by Clémence Fontanive from the Center for Space and Habitability (CSH) and National Centre of Competence in Research PlanetS (NCCR PlanetS) is documented in a paper published in The Astrophysical Journal Letters.

A Star that Failed

The Oph 98 is a relativity new-born system in astrophysical terms, forming just 3 million years ago in the Ophiuchus stellar nursery (hence the ‘Oph’ element of its name). Its relative youth has some interesting consequences for the bodies that comprise it and led the team to properly identify its constituent bodies. 

The system has not existed for long enough for it to start forming planets. This means that Oph 98 A and B must have both formed via the same mechanisms that give rise to stars. This conclusion is also supported by the fact that Oph 98 B is roughly the right size to be a planet, but Oph A is too small to have the reservoir of material needed to form a planet so large. That means they must be brown dwarfs.

“This tells us that Oph 98 B, like its host, must have formed through the same mechanisms that produce stars and shows that the processes that create binary stars operate on scaled-down versions all the way down to these planetary masses,” says Fontanive.

In terms of mass brown dwarfs exist between planets and stars (NASA/ Caltech/ R. Hurt (IPAC).)

The fact that brown dwarfs form in ways that are similar to stars and share similar masses, but do not ignite with the nuclear processes that power stars, has often led to them being nicknamed ‘failed stars.’ It is extremely rare for star-forming processes to create worlds that go on to exist in a system such as this. 

The objects are rare examples of astronomical bodies similar to giant exoplanets that orbit each other without a parent star. Both are young brown dwarfs, with Oph 98 A being the larger of the two with a mass 15 times that of Jupiter. Its smaller companion — Oph 98 B — has a mass equivalent to 8 times that of the gas giant, which is the largest body other than the Sun in our solar system.

This isn’t the only thing that makes Oph 98 unique, however. 

Brown Dwarfs with a Weak Bond

Another thing that makes the Oph 98 system so remarkable is the fact that, like all binary systems, the bodies are gravitationally bound. These bonds are greater with objects of greater mass but follow an inverse square law — meaning the bond’s strength falls off quickly as separation distances increase. Because these objects have relatively small mass coupled with an extremely large separation, the gravitational bond between them is one of the weakest in terms of energy that astronomers have ever observed. 

Observing this system at all is no mean feat as brown dwarfs — especially low-mass ones — emit very little electromagnetic radiation and are thus, not easy to spot.

“Low-mass brown dwarfs are very cold and emit very little light, only through infrared thermal radiation,” explains Fontanive. “This heat glow is extremely faint and red, and brown dwarfs are hence only visible in infrared light.” 

The Ophiuchus cluster that is home to Oph 98 sits in a cloud of dust that makes it difficult to see. In this image it is pictured in X-rays by the Chandra X-Ray Observatory (Chandra X-Ray Observatory)

This visibility challenge was further compounded by the fact that Oph 98 and the Ophiuchus galaxy cluster itself is embedded in a dense cloud of dust that scatters visible light. “Infrared observations are the only way to see through this dust,” the researcher adds.

In fact, the team’s discovery was only made possible by the impressive power of the Hubble Space Telescope and the fact that it makes its observations from above Earth.

Hubble Shines Through Again

The Hubble Space Telescope is one of the only telescopes capable of observing objects as faint as the Oph 98 A and B and resolving the image of the brown dwarfs at such tight angles.

“Detecting a system like Oph 98 also requires a camera with a very high resolution, as the angle separating Oph 98 A and B is a thousand times smaller than the size of the moon in the sky,” Fontanive continues. 

The Hubble Space telescope’s vantage point above Earth’s atmosphere allows it to spot water vapor from brown dwarfs (ESA)

Hubble’s space-based vantage point is also crucial for the observation of such objects. This is because the infrared signatures that are used to observe brown dwarfs arise from water vapors that form in their upper atmospheres. As Earth’s atmosphere is full of water also producing this signal, the fainter trace from distant brown dwarfs is almost always obscured beyond detection for telescopes at the planet’s surface. 

“Both objects looked very red and showed clear signs of water molecules. This immediately confirmed that the faint source we saw next to Oph 98 A was very likely to also be a cold brown dwarf, rather than a random star that happened to be aligned with the brown dwarf in the sky,” says Fontanive.

The team also found Oph 98 in data collected by the CFHT (pictured) 14 years ago. (CFHT)

Interestingly, the team’s findings have helped confirm the fact that the Oph 98 system has actually been spotted before. The binary was also visible in data collected by the Canada-France-Hawaii Telescope (CFHT), located atop the summit of Mauna Kea, Hawaii, 14 years ago. This older data helped the team confirm how Oph 98 A and B move together across the galaxy as a pair.

“We observed the system again this summer from another Hawaiian observatory, the United Kingdom Infra-Red Telescope. Using these data, we were able to confirm that Oph 98 A and B are moving together across the sky over time, relative to other stars located behind them, which is evidence that they are bound to each other in a binary pair”, explains Fontanive. “We are really witnessing an incredibly rare output of stellar formation processes.”

Original Research

Fontanive. C., et al, ‘A wide planetary-mass companion to a young low-mass brown dwarf in Ophiuchus,’ The Astrophysical Journal Letters, [2020], [https://arxiv.org/abs/2011.08871]

Researchers discover a planet so big it might not be a planet after all

Astronomers have spotted a planet 13 times larger than Jupiter, raising questions as to whether it is a planet, or rather something else.

The newly discovered object lies at the border between gas giants and brown dwarfs. Image via Wiki Commons.

NASA’s Spitzer telescope is an infrared space telescope launched in 2003. Initially meant to survive for only 2.5 years, the telescope is still running, allowing astronomers to gather useful data, especially through a technique called microlensing. In gravitational lensing, astronomers study the bending of the light caused by massive objects or clusters. Stars from the Milky Way usually serve as the lensing object. Microlensing is a type of gravitational lensing in which no distortion in shape can be seen, but the amount of light received from a background object still changes in time. The effect is small, such that even a galaxy with a mass more than 100 billion times that of the Sun will produce barely noticeable effects. However, these effects are strong enough to be noticed.

A light source passes behind a gravitational lens (point mass placed in the center of the image). The aqua circle is a source as it would be seen if there was no lens; white spots are the multiple images of the source.

The good thing about microlensing is that it does not rely on the light from the host stars; thus, it can detect planets, even when the host stars cannot be detected. This was the case with an object called OGLE-2016-BLG-1190.

The object might not sound very exciting, but it is. Astronomers estimate it to be at about 13.4 Jupiter masses. This is almost too big to be a planet; it puts it right at the limit between gas giants and a brown dwarf. In other words, we don’t know if it is a humongous planet or a failed star.

“The planet’s mass places it right at the deuterium burning limit, i.e., the conventional boundary between “planets” and “brown dwarfs”. Its existence raises the question of whether such objects are really “planets” (formed within the disks of their hosts) or “failed stars” (low mass objects formed by gas fragmentation),” the paper reads.

The deuterium burning researchers refer to is a nuclear fusion reaction that occurs in stars and some substellar objects, in which a deuterium nucleus and a proton combine to form a helium nucleus.

Deuterium fusion is what makes a star a star. Brown stars occupy the mass range between the heaviest gas giant planets and the lightest stars. They are generally regarded as sub-stellar objects not massive enough to sustain nuclear fusion of ordinary hydrogen, but still massive enough to support the fusion of deuterium.

OGLE-2016-BLG-1190Lb orbits its parent star approximately every three years, two times further away than the Earth is from the Sun. It’s the first planet discovered through microlensing from Spitzer.

Journal Reference: Y.-H. Ryu et al. OGLE-2016-BLG-1190Lb: First Spitzer Bulge Planet Lies Near the Planet/Brown-Dwarf Boundary. arXiv:1710.09974

TRAPPIST-1, the dwarf star with seven Earth-sized planets, is older than our solar system

The solar system with seven potentially habitable planets is much older than our own.

This illustration shows what the TRAPPIST-1 system might look like from a vantage point near planet TRAPPIST-1f (at right).
Credits: NASA/JPL-Caltech

TRAPPIST-1, with the much less attractive technical name 2MASS J23062928-0502285, is an ultra-cool brown dwarf just slightly larger than Jupiter. Despite its small size and low temperature, it’s one of the most interesting stars we’ve discovered out there. In February this year, NASA announced the discovery of seven Earth-sized planets around the star, all in the habitable zone — the so-called Goldilocks area where it’s just the right temperature for liquid water to exist. To make things even more exciting, this solar system is a ‘mere’ 40 light years away. It’s far enough to be inaccessible for the foreseeable future, but given the sheer immensity of our galaxy, 40 light years is just peanuts.

But having an Earth-like figure and being located in the habitable zone isn’t nearly enough to support life. That’s why astronomers at NASA have been studying the system assiduously, trying to learn more about it and establish its conditions. Now, for the first time, they’ve put an age on it — or rather, an age range. TRAPPIST-1 is between 5.4 and 9.8 billion years old. This makes it a very old system compared to our own, which is ‘just’ 4.5 billion years old.

It’s indeed a very broad range, but at least it enables us to say that the system is old, though we’re not yet sure how old. Also, while it’s a broad constraint, it’s still a constraint. When it was first discovered, we only knew that the star had to be older than 0.5 billion years, since that’s how long it takes for these stars to contract. It could have been almost as old as the universe itself.

“Our results really help constrain the evolution of the TRAPPIST-1 system, because the system has to have persisted for billions of years. This means the planets had to evolve together, otherwise the system would have fallen apart long ago,” said Adam Burgasser, an astronomer at the University of California, San Diego, and the paper’s first author.

The system overlaid over the habitable zone.
Image credits: NASA/JPL.

It’s not clear exactly what this means for the habitability of the planet. It’s known that older stars tend to flare less than younger stars, thus having less of a chance of wiping out potential life. But this also means that the planets have absorbed billions of years of high-energy radiation, which might imply that their atmospheres have boiled off. A decent analogy here is Mars, which once hosted an atmosphere which has since been wiped off by radiation.

But there are more aspects to consider. TRAPPIST-1 planets have lower densities than Earth, which makes it more likely for them to hold vast reservoirs of volatile molecules, which could generate thick atmospheres, strong enough to protect the planets from radiation. Especially the two outer planets, planet and planet h might have been lucky enough to escape with an atmosphere.

But if any life exists on these planets, it’s almost certainly way more hardy than that on Earth.

“If there is life on these planets, I would speculate that it has to be hardy life, because it has to be able to survive some potentially dire scenarios for billions of years,” Burgasser said.

TRAPPIST-1 is an ultra-cool dwarf star in the constellation Aquarius, and its seven planets orbit very close to it, which puts them in the Goldilocks area.
Credits: NASA/JPL-Caltech

Future observations will focus on identifying potential atmospheres around these planets. If such an atmosphere exists, then it likely existed for billions of years, which makes the possibility of extraterrestrial life significantly more likely. The observations will also help astronomers better understand other similar systems form and develop.

“These new results provide useful context for future observations of the TRAPPIST-1 planets, which could give us great insight into how planetary atmospheres form and evolve, and persist or not,” said Tiffany Kataria, exoplanet scientist at JPL, who was not involved in the study.

 

Astronomers find water clouds on brown dwarf

Researchers working with the Gemini North telescope in Hawaii have made a stunning discovery: they found evidence of water clouds around a brown dwarf.

Artist’s rendering of WISE 0855 as it might appear if viewed up close in infrared light. (Illustration by Joy Pollard, Gemini Observatory/AURA)

Since its discovery, the brown dwarf known as WISE 0855 has fascinated astronomers. It lies just 7.2 light-years from Earth and it’s the coldest confirmed object outside of our solar system at temperatures ranging between −48 to −13 °C (that’s −55 to 8 °F). The team working on the star have now obtained the star’s infrared spectrum — providing the first details of the object’s composition and chemistry. Among the findings is water, in the form of clouds.

“We would expect an object that cold to have water clouds, and this is the best evidence that it does,” said Andrew Skemer, assistant professor of astronomy and astrophysics at UC Santa Cruz.

“It’s five times fainter than any other object detected with ground-based spectroscopy at this wavelength,” Skemer said. “Now that we have a spectrum, we can really start thinking about what’s going on in this object. Our spectrum shows that WISE 0855 is dominated by water vapor and clouds, with an overall appearance that is strikingly similar to Jupiter.”

Cold stars

Brown dwarfs are failed stars, which never picked up enough steam and mass to spark the nuclear fusion necessary to become “real” stars. In a way, they’re more similar to gas giants than stars, but they formed from the collapse of nebular gases, not from the accretion disc.

But having about five times the mass of Jupiter, WISE 0855 resembles that gas giant planet in many respects. In fact, astronomers believe that by studying WISE 0855 we could learn more about Jupiter.

“WISE 0855 is our first opportunity to study an extrasolar planetary-mass object that is nearly as cold as our own gas giants,” Skemer said.

Another interesting similarity is that they seem to share similar spectrum features. Namely, their spectra have similar water-absorption features, which likely indicates that they both have water vapours in their respective atmospheres. However, Jupiter also has a significant amount of phosphine (a compound of phosphorous and hydrogen) in its atmosphere, while WISE 0855 does not, which would indicate that Jupiter’s atmosphere is much more turbulent, and WISE 0855 is a calmer place.

WISE 0855 and brown dwarfs in general still have many secrets which await uncovering, but the mere fact that we know about a star with water vapours in its atmosphere is mind blowing.

The research was published in Astrophysical Journal Letters and is currently available online.

Lonely planet found in a family of stars

NASA astronauts have discovered a lonely planetary-like mass floating on its own, without a solar system.

A young, free-floating world sits alone in space in this illustration. The object, called WISEA J114724.10?204021.3, is thought to be an exceptionally low-mass “brown dwarf,” which is a star that lacked enough mass to burn nuclear fuel and glow like a star. Image credit: NASA/JPL-Caltech

Imagine a galaxy, riddled with countless solar systems. Then zoom in slowly on a solar system – how do you picture it? There’s probably a star at the center, and several planets around it. That’s generally where we feel planets should be, rotating around a star. But in 2011, astronomers reported that our galaxy is likely teeming with free-floating planets – even outnumbering star-hosted planets. This was a very surprising finding which immediately begs another question: where did these planets come from? Are they the sole survivors from a solar system, were they ejected somehow, or were they simply forever alone, wandering the galaxy by themselves?

Perhaps the most interesting theory is that they aren’t planets in the first place – just smaller stars called brown dwarfs which look like planets. Brown dwarfs are peculiar objects: they’re too small to be called stars, and too big to be called planets. They’re not big enough to sustain sustain hydrogen fusion reactions in their cores, unlike main-sequence stars. A new study using data from NASA’s Wide-field Infrared Survey Explorer, WISE, and the Two Micron All Sky Survey, or 2MASS shed some new light on these brown dwarfs, as well as the mystery of lonely stars. The study found a new object, called WISEA J114724.10-204021.3, or just WISEA 1147 for short, estimated to be between roughly five to 10 times the mass of Jupiter.

What makes this particular loner important is that astronomers can track its origin – it’s a brown dwarf.

“With continued monitoring, it may be possible to trace the history of WISEA 1147 to confirm whether or not it formed in isolation,” said Adam Schneider of the University of Toledo in Ohio, lead author of a new study accepted for publication in The Astrophysical Journal.

At this point, we have no idea if this is the rule, the exception, or somewhere in between. Most lonely planets could be brown dwarfs, or very few of them could be – we don’t know the fraction. Tracing the origins of free-floating worlds, and determining whether they are planets or brown dwarfs, is a difficult task, specifically because the objects themselves are so isolated and difficult to identify.

“We are at the beginning of what will become a hot field – trying to determine the nature of the free-floating population and how many are planets versus brown dwarfs,” said co-author Davy Kirkpatrick of NASA’s Infrared Processing and Analysis Center, or IPAC, at the California Institute of Technology in Pasadena.

Finding WISEA 1147 was possible after sifting through many images of the space, taken with WISE in 2010 and 2MASS, about a decade earlier, as it was “brilliantly red” in the images, but this will likely not be the case most of the times.

“The features on this one screamed out, ‘I’m a young brown dwarf,'” said Schneider.

 

Scientists find a tiny star with a huge storm — just like Jupiter’s

Scientists have found one storm that no umbrella can keep you safe from — because that umbrella is going to burn in your hand.

While the windy and overcast weather of a stormy day isn’t surprising on telluric planets, it’s not something most of us readily associate with stars. But it does happen — the best evidence for this is W1906+40, a distant dwarf star recently described in a study published in the Astrophysical Journal.

This illustration shows a cool star, called W1906+40, marked by a raging storm near one of its poles. Image via washingtonpost

This illustration shows a cool star, called W1906+40, marked by a raging storm near one of its poles. Image via washingtonpost

Being small for a star (about as big as Jupiter) W1906+40 is classified as an L-dwarf, more towards planets on the planet-star spectrum. The coolest stars in this class are known as brown dwarfs, “failed stars” that aren’t big or don’t have enough heat to sustain fusion and generate light as most stars do and resemble giant gas planets. However, they form very differently than planets and scientists often have to use the cosmic object’s age to classify it correctly.

With an estimated 3,500 degrees Fahrenheit of surface temperature,  W1906+40 might still have some fusion going on, but nothing powerful enough to stop mineral clouds from forming in its atmosphere, blurring the line between a planet and a star. But just like on Jupiter, the planet-and-star combination of features led to the formation of a massive storm.

On Jupiter, the Great Red Spot has been churning and raging on for as long as humanity has been able to see it — some 400 years. It’s been slowly getting smaller and smaller, though it being roughly three times the size of Earth means the term “smaller” is used loosely here.

“The star is the size of Jupiter, and its storm is the size of Jupiter’s Great Red Spot,” study author John Gizis of the University of Delaware said in a statement. “We know this newfound storm has lasted at least two years, and probably longer.”

The storm on W1906+40 was spotted using the Kepler exoplanet hunting telescope. It searches for exoplanets by measuring the dimming of distant stars’ light, which can be used to determine if there are any objects passing in front of it.

 

In the case of W1906+40, Gizis and his team saw a dark spot that didn’t waver. This wasn’t unusual — patches of concentrated magnetic field can make dark blotches on a star’s surface known as star spots (on sunspots on the Sun,) behave the same way and are relatively common.

But further investigation in infrared light revealed that the dark spot had nothing to do with magnetic fields. The whopping storm makes a dark mark on top of the star, rotating around it about every nine hours.

Scientists aren’t sure why these storms last so long or how common they are, but the researchers involved in the study plan on seeking out more stormy dwarfs to learn more.

star flyby oort cloud

70,000 Years Ago, a Rogue Star Passed Through Our Solar System

Too close for comfort – a team of astronomers from the US, Europe, Chile and South Africa concluded that a dim star passed through the Oort cloud, our solar system’s distant cloud of comets. The star missed the Earth by less than one light year, and passed five times closer than the current closest star, Proxima Centauri.

star flyby oort cloud

Artist’s conception of Scholz’s star and its brown dwarf companion (foreground) during its flyby of the solar system 70,000 years ago. The Sun (left, background) would have appeared as a brilliant star. The pair is now about 20 light years away.
Credit: Michael Osadciw/University of Rochester.

In a paper published in The Astrophysical Journal Letters, lead author Eric Mamajek from the University of Rochester and his team studied the velocity and trajectory of a low-mass star system – WISE 0720-0846 (nicknamed “Scholz’s star”). Due to its low luminosity, the star was discovered only a year ago by astronomer Ralf Dieter-Scholz in Potsdam, Germany, through the use of NASA’s WISE (Wide Field Infrared Survey Explorer), which mapped the entire sky in infrared during the years 2010 and 2011.

Since it was discovered, it had some interesting characteristics. despite being fairly close (“only” 20 light years away), it showed very slow tangential motion, that is, motion across the sky. By studying its trajectory and velocity, astronomers found that the star was either moving towards, or away from our solar system. They reconstructed its past movement and quickly realized it was moving away from our solar system, which means that it passed through it (or very close to it) sometime in the past.

“Most stars this nearby show much larger tangential motion,” says Mamajek, associate professor of physics and astronomy at the University of Rochester. “The small tangential motion and proximity initially indicated that the star was most likely either moving towards a future close encounter with the solar system, or it had ‘recently’ come close to the solar system and was moving away. Sure enough, the radial velocity measurements were consistent with it running away from the Sun’s vicinity — and we realized it must have had a close flyby in the past.”

Scholz’s star moved much faster than expected, and missed Earth by “a whisker” – in astronomical terms, that is. It passed roughly 0.8 light years away from Earth, at 8 trillion kilometers; this happened 70,000 years ago. It may seem like a lot, but it’s really too close for comfort. This fits with an earlier theory, which proposed that such close flybys take place every 100,000 years or so. These encounters could hit the Oort cloud and trigger “comet showers” in the solar system.

“Sure enough, the radial velocity measurements were consistent with it running away from the sun’s vicinity — and we realized it must have had a close flyby in the past,” Mamajek said in a news release.

 

The star is a rogue star – a star that has escaped the gravitational pull of its home galaxy and is moving independently in or towards the intergalactic void; the movement of rogue stars is often hard to predict. A 2012 study claimed that rogue planets riddle the Milky Way, and while rarer, there are also rogue stars in our galaxy.

Currently, Scholz’s star is a small, inconspicuous red dwarf in the constellation of Monoceros, about 20 light years away. The star is part of a binary star system, composed of a low-mass red dwarf star (with mass about 8% that of the Sun) and a “brown dwarf” companion (with mass about 6% that of the Sun). Red dwarfs are by far the most common type of star in the Milky Way, at least in the neighborhood of the Sun, but due to their low luminosity, they are difficult to observe and study. Brown stars are “failed stars” – substellar objects not massive enough to sustain hydrogen-1 fusion reactions in their cores, unlike … well, stars.

Journal Reference:

  1. Eric E. Mamajek, Scott A. Barenfeld, Valentin D. Ivanov, Alexei Y. Kniazev, Petri Väisänen, Yuri Beletsky, Henri M. J. Boffin. THE CLOSEST KNOWN FLYBY OF A STAR TO THE SOLAR SYSTEM. The Astrophysical Journal, 2015; 800 (1): L17 DOI: 10.1088/2041-8205/800/1/L17

 

A strange, lonely planet found without a star

An international discovered a young, exotic, rogue planet – PSO J318.5-22, is just 80 light-years away from Earth and has a mass six times that of Jupiter; it was formed apporximately 12 million years ago – which makes it a newborn in terms of planets (the Earth was formed approximately 4.5 billion years ago.

ps1_lonely_planet-450

Multicolor image from the Pan-STARRS1 telescope of the free-floating planet PSO J318.5-22, in the constellation of Capricornus. Most of its energy is emitted in infrared.

“We have never before seen an object free-floating in space that that looks like this. It has all the characteristics of young planets found around other stars, but it is drifting out there all alone,” explained team leader Dr. Michael Liu of the Institute for Astronomy at the University of Hawaii at Manoa. “I had often wondered if such solitary objects exist, and now we know they do.”

During the past decade, the discovery of new exoplanet has developed at an exponential pace, without about 1.000 (!) new planet discovered through indirect methods. However, even with the astonishing development of technique, only a handful were observed through direct imaging.

“Planets found by direct imaging are incredibly hard to study, since they are right next to their much brighter host stars. PSO J318.5-22 is not orbiting a star so it will be much easier for us to study. It is going to provide a wonderful view into the inner workings of gas-giant planets like Jupiter shortly after their birth,” said Dr. Niall Deacon of the Max Planck Institute for Astronomy in Germany and a co-author of the study.

Astronomers have confirmed the existence of rogue planets only a few year ago, so this is also an exciting, new field of study. There is no current way of telling whether these are planets that have been ejected from orbiting a star or were originally formed on their own as sub-brown dwarfs.

Via University of Hawaii.

black-hole-feeding

Black-hole wakes up from slumber and feasts on super-Jupiter planet

black-hole-feeding

Artist illustration of the supermassive black hole consuming on a substellar object. (C) ESA

In an unexpected discovery, astronomers have surprised a supermassive black hole that had been dormant for the past decades “waking up” and feasting upon an unsuspecting planet that had drifted too close to its event horizon.  The mass of the planet hints towards a giant Jupiter or a small brown dwarf. Also, a similar event is set to take place in our galaxy soon, after observations of the supermassive black hole lying at the center of our own galaxy showed that it will engage in a similar feeding event, albeit on a gas cloud.

The event was picked-up by the European INTEGRAL space observatory, which surveys the cosmos for high-energy emissions of gamma-rays and X-rays. At the time, INTEGRAL was studying a different galaxy, but a sudden energy flare at NGC 4845, a spiral galaxy some 47 million light-years away, caught the attention of astronomers and it could mean only one thing – the supermassive black hole deep in the galaxy’s bawls had woken up after more than 30 years. Follow-up observations from ESA’s XMM-Newton, NASA’s Swift and Japan’s MAXI X-ray monitor on the International Space Station confirmed the finding.

Technically however there’s no such thing as an inactive black hole, but what the researchers describe through this “hibernation” metaphor is a lack of feeding over a long period of time.

“The observation was completely unexpected, from a galaxy that has been quiet for at least 20–30 years,” said Marek Nikolajuk of the University of Bialystok, Poland, lead author of the research published in the journal Astronomy & Astrophysics.

By analyzing the intensity and duration of the feeding, which peaked in January 2011 and then slowly subsided over the course of a year, the astronomers could infer the mass of the black hole’s meal. Subsequent analysis showed that the object must have been somewhere in the mass range of 14–30 Jupiter masses, consisting with a giant nomad planet (planet’s that stray and travel through interstellar space) or a brown dwarf (substellar objects that are not massive enough to fuse hydrogen in their core and ignite as stars).

A sleeping giant just woke up and it’s damn hungry

The black hole wasn’t just satisfied with having a hefty meal, however. It toyed with its preyed and tormented it, as analysis showed X-ray emissions fluctuated over 2-3 months, suggesting the object passed close, suffered some extreme tidal shear, causing layers of gas to be ripped away before the whole thing was finally consumed. If you’re interested, ESA has a video simulation of the event here.

“This is the first time where we have seen the disruption of a substellar object by a black hole,” said co-author Roland Walter of the Observatory of Geneva, Switzerland.
“We estimate that only its external layers were eaten by the black hole, amounting to about 10% of the object’s total mass, and that a denser core has been left orbiting the black hole.”

According to the researchers, the flaring event in NGC 4845 was a warm-up for a more interesting “black hole in action” study, right in our backyard. Later this year, the Milky Way’s supermassive black hole is expected to commence feeding on a straying giant gas cloud. The cloud is already suffering extreme disruption and is expected to meet its end soon enough. By studying events such as NGC 4845’s flaring or the upcoming gas cloud gobbling by our closest supermassive black hole, scientists can deepen our understanding and learn new things about what happens to cosmic objects as they encounter black holes of various sizes.

“Estimates are that events like these may be detectable every few years in galaxies around us, and if we spot them, Integral, along with other high-energy space observatories, will be able to watch them play out just as it did with NGC 4845,” added Christoph Winkler of the European Space Agency (ESA).

First remote reconnaissance of another solar systems reveals unlike “any other known object in our Universe”

Researchers have for the first time conducted a remote reconnaissance of a distant planetary system with a new telescope imaging system.

Peeking at other planets

reconnaissance

Project 1640 is a dedicated high contrast imaging program at Palomar Observatory with the goal of obtaining images and spectra of brown dwarfs and planetary mass companions to nearby stars. The solar system they analyzed is 128 light years away, and has four red exoplanets; a detailed description of the planets was published in the Astrophysical Journal, showing what an unbelievable diversity of planets our galaxy hosts.

“An image is worth a thousand words, but a spectrum is worth a million,” said lead author Ben R. Oppenheimer, associate curator and chair of the Astrophysics Department at the American Museum of Natural History.

Spectroscopic measurements

spectroscopy1Oppenheimer is the main investigator working on the project. He explained that the planets orbiting the star in case, but until now, the star’s bright light overwhelmed previous attempts to study the planets with spectroscopy. Simplistically put, spectroscopy studies how white light is split into its constituent wavelenghts, much like when it passes through a prism; it’s very useful in such studies, because every chemical element has its unique spectroscopic signature, and if the conditions allow it to be applied properly, the technique can reveal the chemical composition of a planet’s atmosphere.

“In the 19th century it was thought impossible to know the composition of stars, but the invention of astronomical spectroscopy has revealed detailed information about nearby stars and distant galaxies,” said Charles Beichman, executive director of the NASA Exoplanet Science Institute at the California Institute of Technology. “Now, with Project 1640, we are beginning to turn this tool to the investigation of neighboring exoplanets to learn about the composition, temperature, and other characteristics of their atmospheres.”

With this new system, the conditions were just right, allowing a fantastic observation of the planets orbiting HR 8799.

“It’s fantastic to nab the spectra of four planets in a single observation,” said co-author Gautam Vasisht, an astronomer at the Jet Propulsion Laboratory.

Unexpected results

spectroscopy 2

The results were very strange – unlike anything astronomers were prepared for.

“These warm, red planets are unlike any other known object in our universe. All four planets have different spectra, and all four are peculiar. The theorists have a lot of work to do now.”

The first anomaly that strikes the eye is the apparent chemical imbalance. From what we know of basic chemistry, ammonia and methane should naturally coexist in varying quantities unless they are in extremely cold or hot environments. However, at temperatures just over 700 degrees Celsius (1340 degrees Fahrenheit), which are “lukewarm” by astronomic standards, all the planets either have methane or ammonia, with little or no signs of their chemical partners.

The planets are also surprisingly red – emitting longer wavelengths of light, than celestial objects with similar temperatures. The most likely explanation for this phenomena is a patchy cloud covering all the planets.

“The spectra of these four worlds clearly show that they are far too toxic and hot to sustain life as we know it,” said co-author Ian Parry, a senior lecturer at the Institute of Astronomy, Cambridge University. “But the really exciting thing is that one day, the techniques we’ve developed will give us our first secure evidence of the existence of life on a planet outside our solar system.”

A bright future

Aside from the unquestionable value of this particular study, the system has proven its worth and now, researchers will definitely want to take a glance at other solar systems, perhaps some which are more likely to harbor life.

“Astronomers are now able to monitor cloudy skies on extrasolar planets, and for the first time, they have made such observations for four planets at once,” said Maria Womack, program director for the Division of Astronomical Sciences at the National Science Foundation. “This new ability enables astronomers to now make comparisons as they track the atmospheres, and maybe even weather patterns, on the planets.”

The fact that all these planets were different also shows that the technique works in a number of environments, bringing even more hope to the table.

“The variation in the spectra of the four planets is really intriguing,” said Didier Saumon, an astronomer at Los Alamos National Laboratory who was not involved in this study. “Perhaps this shouldn’t be too surprising, given that the four gaseous planets of the solar system are all different. The hundreds of known exoplanets have forced us to broaden our thinking, and this new data keeps pushing that envelope.”

Artist's impression of the "rogue planet" CFBDSIR2149 discovered in the AB Doradus group of moving stars. (European Southern Observatory/AFP)

Closest rogue planet discovered is just 100 light-years away

Like in a scene from a Sci-fi novel, about 100 light years away, somewhere in the constellation Doradus, a planet is travelling around the galaxy by itself, without orbiting a parent star. This “rogue planet“, has a temperature of about 400C and a mass between 4 to 7 times that of Jupiter – close to the mass limit beyond which it would have become a brown dwarf.

The object, that so far has the captivating name of CFBDSIR2149, has been discovered while observing a region of space occupied by a group of about 30 stars called the AB Doradus Moving Group – a group of stars that have formed at the same time – most likely from the same initial gaseous nebulae. This fact was derived from the similarities in the composition, age and the similar direction of movement through space of the stars – which place the age of this group somewhere between 50 and 120 million years old – a reasonably young star group.

Artist's impression of the "rogue planet" CFBDSIR2149 discovered in the AB Doradus group of moving stars. (European Southern Observatory/AFP)

Artist’s impression of the “rogue planet” CFBDSIR2149 discovered in the AB Doradus group of moving stars. (European Southern Observatory/AFP)

The initial observations placed the object in the category of brown dwarfs – a class of sub-stellar objects – that are more massive then the biggest planets – the gas giants, yet they don’t have enough mass to start nuclear fusion. However, further analyses revealed that our object was in fact smaller than this – making it a planet – a gas giant. The whole detection was possible due to the fact that our “rogue” emits light in the infrared wavelengths.

Astronomers said that based on its estimated age, through computer models of planetary evolution, they were able to make further deductions regarding the planet’s mass – 4 to 7 times the mass of Jupiter, and surface temperature of 400 degrees Celsius (750 degrees Fahrenheit).

The planet was discovered during a survey using the infrared cameras of the Canada-France-Hawaii Telescope on Hawaii’s Mauna Kea and the Very Large Telescope (VLT) in Chile, as study co-author Etienne Artigau of the University of Montreal said: “This object was discovered during a scan that covered the equivalent of 1,000 times the [area] of the full moon.

Of course, this is not the first time such a “nomad planet” has been spotted, but this observation is special because it found the closest such object discovered so far – only 100 light years away, the first such planet that is relatively close to our solar system, as study co-author Etienne Artigau put it: “We observed hundreds of millions of stars and planets, but we only found one homeless planet in our neighbourhood“.

A big question in the case of all such rogue planets is how this planet came to be? Maybe it formed inside a solar system, just as any other planet, and got ejected afterwards – through gravitational interaction perhaps with a more massive object entering that system. Or it formed separate from any solar system from the beginning, similar to the formation of a star – through progressive accretion of the gas of a dense nebulae. This question remains open – and perhaps will remain for some time to come.

Philippe Delorme of France’s Institute of Planetology and Astrophysics said: “these objects are important, as they can either help us understand more about how planets may be ejected from planetary systems, or how very light objects can arise from the star formation process.”

The findings were reported in the journal Solar and Stellar Astrophysics.

source: BBC

NASA discovers coolest stars ever

NASA’s Wide-field Infrared Survey Explorer (WISE) has offered data about the coolest stars ever found until now, stars which are about as warm as you and me.

Named Y dwarfs, these stars have lit the interest of astrophysicists for a long time, but it wasn’t until now that they were finally discovered and analyzed. These dark orbs are almost impossible to see with a visible light telescope, but WISE’s infrared vision allowed researchers to finally notice their faint glow, locating them relatively near, at 40 light years away.

“WISE scanned the entire sky for these and other objects, and was able to spot their feeble light with its highly sensitive infrared vision,” said Jon Morse, Astrophysics Division director at NASA Headquarters in Washington. “They are 5,000 times brighter at the longer infrared wavelengths WISE observed from space than those observable from the ground.”

These stars, also named brown dwarfs are also referred to as failed stars, because their mass is too low to fuse atoms at their core, so instead of becoming incandescent, like most stars, they just cool even more. Their atmosphere is pretty similar to that of gas giants, such as Jupiter, but they are easier to see because they are alone, and away from the blinding light of another star.

“The brown dwarfs we were turning up before this discovery were more like the temperature of your oven,” said Davy Kirkpatrick, a WISE science team member at the Infrared Processing and Analysis Center at the California Institute of Technology in Pasadena, Calif. “With the discovery of Y dwarfs, we’ve moved out of the kitchen and into the cooler parts of the house.”

Coldest star so far found – not hotter than a cup of coffee

An artist's impression of the coldest brown dwarf found so far, CFBDSIR 1458 10b captioned on the right. Image (c) L. Calçada, ESO.

Astronomers usually classify stellar objects by a spectra going from hotter to cooler, using the letters O, B, A, F, G, K, and M. As observational technology progressed and a myriad of new astronomical findings were made, in the last 15 years alone two new classes  L and T emerged designed to describe ultracool brown dwarfs. A recent scientific finding suggests that yet another spectra might need to be added to accommodate the coldest star discovered so far.

Dubbed CFBDSIR 1458 10b, the brown dwarf has a remarkably low surface temperature of  97 degrees C (206 degrees F) –  just about as hot as a freshly made morning cup of coffee.

Over the years there has been steady but slow progress in pushing the boundaries of finding the coldest stars,” said study leader Michael Liu, an astronomer at the University of Hawaii were a team of researchers studied and published a paper about CFBDSIR 1458 10b.

“But with this latest discovery we have made a big leap forward—besting the previous record holder by at least 150 Kelvin [270 degrees F, or 150 degrees C],” he said.

Astronomers using the Keck II telescope recorded this composite infrared image of the brown dwarf binary designated CFBDSIR J1458+10. The fainter component is at present date considered the coldest star discovered so far. (c) Michael Liu - Univ. of Hawaii

CFBDSIR J1458+1013B did not cool down after starting out hot like our Sun, instead “it never became very hot in the first place because it developed from a fairly small cloud of gas,” said Duane Pontius, professor of physics at Birmingham-Southern College (BSC) in Alabama. “Gravity pulled the cloud together and compressed the gas, which heats it up just as a bicycle pump heats up when you compress air into a tire. But relative to brighter stars, there wasn’t as much gas, so this star never heated up much.”

This means that because it has such a low gravitational energy and mass, the dwarf was never able to sustain hydrogen fusion reactions in its core, which creates scorching high surface temperatures like 5,500 degrees Celsius on our own sun (a fairly low temperature compared to other stellar bodies). Astronomers at Keck II telescope, Canada-France-Hawaii telescope, and European Southern Observatory Very Large Telescop managed to describe CFBDSIR J1458+1013B after tracing it’s very dim infrared signature. The dwarf is paired in orbit with yet another dwarf star, the later a lot brighter though.

The study seems to gray the line between scientists decide what can be considered a planet and what can be considered a star, since CFBDSIR J1458+1013B is estimated to have a mass only 6 to 15 the mass of Jupiter, which has a surface temperature of -149 degrees C (-236 degrees F ).

“…this new object is so much colder than anything else seen that it now enters the regime where it may actually have an atmosphere with water clouds,” Liu said.

“The most exciting aspect of this finding is that we might be on the threshold of finding a new class of objects that blurs the line between gas-giant exoplanets and brown dwarf stars previously seen—something I think that is really surprising the astronomical community.”

You think CFBDSIR J1458+1013B is pretty cold for a star? Well, NASA scientists are trying to determine the exact temperature of a newly discovered brown dwarf, called WD 0806-661b, which is believed to have a temperature of roughly ~30 degrees Celsius and a mass 7 times that of Jupiter.

“I think it’s pretty neat to find a ‘star’ that could have a temperature similar to that of Earth,” says Kevin Luhman (Penn State University), who led one of the observing teams. Luhman and two colleagues used NASA’s infrared Spitzer Space Telescope to study WD 0806-661b, the companion of a faint white-dwarf star 63 light-years distant in the southern constellation Volans.

Story via skyandtelescope.com