Newborn Star Found Growing Inside Magnetic Nest of Chaos

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NRAO/AUI/NSF; D. Berry

Conventional wisdom would have us believe that stars form in extremely powerful and ordered magnetic fields. But “conventional,” our universe is not (as Yoda might say).

In a new and fascinating study published in Astrophysical Journal Letters and carried out by astronomers using the Atacama Large Millimeter/submillimeter Array (ALMA) in Chile, a star some 1,400 light-years away in the Serpens star-forming region had its magnetic field gauged.

The star, called Ser-emb 8, is embedded inside the magnetic field passing through the molecular cloud it was born in. As the surrounding dust aligns itself with the direction of these magnetic field lines, ALMA is able to make precise measurements of the polarization of the emissions produced by this dust. From these incredibly sensitive measurements, a map of the polarization of light could be created, providing a view of the magnetic nest the star was born in.

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Texture represents the magnetic field orientation in the region surrounding the Ser-emb 8 protostar, as measured by ALMA. The gray region is the millimeter wavelength dust emission. Credit: ALMA (ESO/NAOJ/NRAO); P. Mocz, C. Hull, CfA

And this nest is an unexpected one; it’s a turbulent region lacking the strong and ordered magnetism that would normally be predicted to be in the immediate vicinity of Ser-emb 8. Previous studies have shown newborn stars to possess powerful magnetic fields that take on an “hourglass” shape, extending from the protostar and reaching light-years into space. Ser-emb 8, however, is different.

“Before now, we didn’t know if all stars formed in regions that were controlled by strong magnetic fields. Using ALMA, we found our answer,” said astronomer Charles L. H. “Chat” Hull, at the Harvard-Smithsonian Center for Astrophysics (CfA) in Cambridge, Mass. “We can now study magnetic fields in star-forming clouds from the broadest of scales all the way down to the forming star itself. This is exciting because it may mean stars can emerge from a wider range of conditions than we once thought.”

By comparing these observations with computer simulations, an insightful view of the earliest magnetic environment surrounding a young star has been created.

“Our observations show that the importance of the magnetic field in star formation can vary widely from star to star,” added Hull in a statement. “This protostar seems to have formed in a weakly magnetized environment dominated by turbulence, while previous observations show sources that clearly formed in strongly magnetized environments. Future studies will reveal how common each scenario is.”

Hull and his team think that ALMA has witnessed a phase of star formation before powerful magnetic fields are generated by the young star, wiping out any trace of this pristine magnetic environment passing through the star forming region.

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‘Failed’ Star Rapidly Orbits ‘Dead’ Star in Weird Stellar Pairing

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ESO

The galaxy may be filled with weird stellar wonders, but you’d be hard-pressed to find a binary system stranger than WD1202-024.

First thought to be an isolated white dwarf star approximately 40% the mass of our sun, astronomers studying observational data from NASA’s Kepler space telescope realized the stellar husk has company. In an extremely fast 71-minute orbit, the star has a brown dwarf, 67 times the mass of Jupiter, in tow — an unprecedented find.

White dwarfs are formed after sun-like stars run out of fuel and die. This will be the fate of our sun in about five billion years time, after it becomes depleted of hydrogen in its core and puffs-up into a red giant. Shedding its outer layers after a period of violent stellar turmoil, a planetary nebula will form with a tiny mass of degenerate matter — a white dwarf — in its center. Earth would be toast long before the sun turns into a red giant, however.

But in the case of WD1202-024, it seems that when it was a young star (before it passed through its final red giant phase), it had a brown dwarf in orbit.

Commonly known as “failed stars,” brown dwarfs are not massive enough to sustain sufficient fusion in their cores to spark the formation of a star. But they’re too massive to be called planets as they possess the internal circulation of material that is more familiar to stars (so with that in mind, I like to refer to brown dwarfs as “overachieving planets”). They are the bridge between stars and planets and fascinating objects in their own right.

But the brown dwarf in the WD1202 binary couldn’t have formed with only a 71-minute orbit around the white dwarf; it would have evolved further away. So what happened? After carrying out computer simulations of the system, the international team of researchers found a possible answer.

“It is similar to an egg-beater effect,” said astronomer Lorne Nelson, of Bishop’s University, Canada, during the American Astronomical Society meeting in Austin, Texas on June 6th. “The brown dwarf spirals in towards the center of the red giant and causes most of the mass of the red giant to be lifted off of the core and to be expelled. The result is a brown dwarf in an extraordinarily tight, short-period orbit with the hot helium core of the giant. That core then cools and becomes the white dwarf that we observe today.”

In the future, the researchers hypothesize, the brown dwarf will continue to orbit the white dwarf until energy is depleted from the system via gravitational waves. In less than 250 million years, the orbital distance will be so small that the extreme tidal forces exerted by the white dwarf will start to drag brown dwarf material into the star, cannibalizing it.

This will turn WD1202 into a cataclysmic variable (CV), causing its brightness to flicker as the brown dwarf material is extruded into an accretion disk orbiting the white dwarf.

What a way to go.

The ‘Alien Megastructure’ Star Is Doing Weird Things Again

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NASA (edit by Ian O’Neill)

In our quest to understand what the heck is going on with Tabby’s Star, astronomers have been given a cosmic gift — a dimming event is happening right now and they’re collecting data in real time.

Early Friday morning, the star — officially designated KIC 8462852 — dipped in brightness inextricably and bulletins started to fly around the internet. Astronomers involved in the original discovery took to Twitter to announce the awesomeness and rally the world’s observatories to point their telescopes at the action 1,300 light-years away:

But why all the excitement? Well, this is the same star that, last year, hogged the headlines with speculation that a super advanced alien civilization was building some kind of “megastructure” around the star. (You can read my article on it here.) But why would the world’s media, let alone professional scientists, be okay with even hinting at the “alien” thing?

Well, as part of the Planet Hunters project, Tabby’s Star is wonderfully weird. After analyzing observations from NASA’s exoplanet-hunting Kepler Space Telescope, the citizen scientists noticed something peculiar.

Usually, Kepler’s ultra-sensitive optics detect the slight dimming of stars when any planets in orbit drift in front — an event known as a “transit.” These transits are typically very slight, but the signals detected at KIC 8462852 were mind-boggling. Between 2011 and 2013, Tabby’s Star exhibited a series of dips, dimming the brightness of the star by over 20 percent. Tabby’s Star was so-named after astronomer Tabetha Boyajian who led this research. Further studies of the star has also revealed a longer period of dimming.

And on Friday morning, it started happening again.

“At about 4 a.m. this morning, I got a phone call from Tabby [Boyajian] saying that Fairborn [Observatory] in Arizona had confirmed that the star was 3 percent dimmer than it normally is and that is enough that we are absolutely confident that this is no statistical fluke,” said Jason Wright, an associate professor of astronomy at Pennsylvania State University, during a live webcast. “We’ve now got it confirmed at multiple observatories I think.”

Now that astronomers are able to observe the star while the dimming is happening live (rather than studying past observations, which as been the case up until now), spectra of the star can be recorded and compared to previous data. This spectral information might reveal what material is causing the weird transit signals, potentially ruling some hypotheses out. But it might also create new questions.

Many hypotheses have been put forward for these unprecedented events before Friday. The most popular natural explanation has been the possibility that a giant “swarm” of comets drifted between the star and us, blocking the starlight. But this explanation falls short and doesn’t really explain why the brightness dips are so dramatic.

The most popular unnatural explanation is — you guessed italiens and astronomers are having a really hard job disproving this hypothesis. This idea is based around the possibility that a super advanced alien civilization (that’s well on its way to becoming a type II Kardashev civilization) is building a star-spanning solar array, akin to a Dyson swarm. In this scenario, the dimming in brightness would be caused by vast solar arrays blocking the light from view.

Now that the dimming is happening again, it will be interesting to see how the megastructure idea evolves.

Although imagining super-advanced aliens building stuff around a nearby star is fun, this episode so early in our hunt for extrasolar worlds is giving us a glimpse of just how strange our galaxy can be. In all likelihood, it probably isn’t an alien megastructure and more likely something astronomers have completely overlooked. But it could also be that these Kepler data are being caused by a natural stellar phenomenon that we’ve never seen before — a possibility that could be revealed very soon.

Two Exoplanets Are Whipping-Up a Pretty Protoplanetary Gas Spiral

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ALMA (ESO/NAOJ/NRAO)/Tang et al.

Using the awesome power of the Atacama Large Millimeter/submillimeter Array (ALMA) in Chile, astronomers have probed the protoplanetary disk of a young star system — with a twist.

ALMA is no stranger to protoplanetary disks; the array of 66 radio antennae in the Atacama desert is extremely sensitive to the emissions from the gas and dust surrounding stars. But this observation has revealed something more — there are two obvious dusty rings (orange) that are being sculpted by the presence of massive worlds, but between them (in blue) is a spiral gas structure. If there’s one thing I love it’s space spirals!

When comparing these observations with theoretical modeling of the system — called AB Aurigae, located about 470 light-years away — for that gas spiral to exist, there must be some interplanetary interplay between two exoplanets orbiting the star at 30 and 80 AU (astronomical units, where 1 AU is the average distance that Earth orbits the sun). The spiral is following the direction of rotation of the disk.

Besides looking really pretty, studies of these spiral structures help astronomers identify the presence of exoplanets and build a better understanding of the nature of protoplanetary disks.

Smallest ‘Super-Earth’ Discovered With an Atmosphere — but It’s No Oasis

MPIA

For the first time, astronomers have detected an atmosphere around a small (and likely) rocky exoplanet orbiting a star only 39 light-years away. Although atmospheres have been detected on larger alien worlds, this is the smallest world to date that has been found sporting atmospheric gases.

Alas, Gliese (GJ) 1132b isn’t a place we’d necessarily call “habitable”; it orbits its red dwarf a little too close to have an atmosphere anything like Earth’s, so you’d have to be very optimistic if you expect to find life (as we know it) camping there. But this is still a huge discovery that is creating a lot of excitement — especially as this exo-atmosphere has apparently evolved intact so close to a star.

The atmosphere was discovered by an international team of astronomers using the 2.2 meter ESO/MPG telescope at La Silla Observatory in Chile. As the exoplanet orbited in front of the star from our perspective (known as a “transit”), the researchers were able to deduce the physical size of the world by the fraction of starlight it blocked. The exoplanet is around 40 percent bigger than Earth (and 60 percent more massive) making it a so-called “super-Earth.”

Through precision observations of the infrared light coming from the exoplanet during the 1.6 day transits, the astronomers noticed that the planet looked larger at certain wavelengths of light than others. In short, this means that the planet has an atmosphere that blocks certain infrared wavelengths, but allows other wavelengths to pass straight through. Researchers of the University of Cambridge and the Max Planck Institute for Astronomy then used this information to model certain chemical compositions, leading to the conclusion that the atmosphere could be a thick with methane or water vapor.

Judging by the exoplanet’s close proximity to its star, this could mean that the planet is a water world, with an extremely dense and steamy atmosphere. But this is just one of the possibilities.

“The presence of the atmosphere is a reason for cautious optimism,” writes a Max Planck Institute for Astronomy news release. “M dwarfs are the most common types of star, and show high levels of activity; for some set-ups, this activity (in the shape of flares and particle streams) can be expected to blow away nearby planets’ atmospheres. GJ 1132b provides a hopeful counterexample of an atmosphere that has endured for billion of years (that is, long enough for us to detect it). Given the great number of M dwarf stars, such atmospheres could mean that the preconditions for life are quite common in the universe.”

To definitively work out what chemicals are in GJ 1132b’s atmosphere, we may not be waiting that long. New techniques for deriving high-resolution spectra of exoplanetary atmospheres are in the works and this exoplanet will be high on the list of priorities in the hunt for extraterrestrial biosignatures. (For more on this, you can check out a recent article I wrote for HowStuffWorks.)

Although we’ll not be taking a vacation to GJ 1132b any time soon, the discovery of an atmosphere around such a small alien world will boost hopes that similar sized super-Earths will also host atmospheres, despite living close to red dwarf stars that are known for their flaring activity. If atmospheres can persist, particularly on exoplanets orbiting within a star’s so-called habitable zone, then there really should be cause for optimism that there really might be an “Earth 2.0” out there orbiting one of the many red dwarfs in our galaxy.

Exoplanets Are Sacrificing Moons to Their White Dwarf Overlords

An artist’s impression of a planet, comet and debris field surrounding a white dwarf star (NASA/ESA)

As if paying tribute, exoplanets orbiting white dwarfs appear to be throwing their exomoons into hot atmospheres of these stellar husks.

This fascinating conclusion comes from a recent study into white dwarf stars that appear to have atmospheres that are “polluted” with rocky debris.

A white dwarf forms after a sun-like star runs out of hydrogen fuel and starts to burn heavier and heavier elements in its core. When this happens, the star bloats into a red giant, beginning the end of its main sequence life. After the red giant phase, and the star’s outer layers have been violently ripped away by powerful stellar winds, a small bright mass of degenerate matter (the white dwarf) and a wispy planetary nebula are left behind.

But what of the planetary system that used to orbit the star? Well, assuming they weren’t so close to the dying star that they were completely incinerated, any exoplanets remaining in orbit around a white dwarf have an uncertain future. Models predict that dynamical chaos will ensue and gravitational instabilities will be the norm. Exoplanets will shift in their orbits, some might even be flung clear of the star system all together. One thing is for sure, however, the tidal shear created by the compact white dwarf will be extreme, and should anything stray too close, it will be ripped to shreds. Asteroids will be pulverized, comets will fall and even planets will crumble.

Stray too close to a white dwarf and tidal shear will rip you to shreds (NASA/JPL-Caltech)

Now, in a science update based on research published late last year in the journal Monthly Notices of the Royal Astronomical Society, astronomers of the Harvard-Smithsonian Center for Astrophysics (CfA) have completed a series of simulations of white dwarf systems in an attempt to better understand where the “pollution” in these tiny stars’ atmospheres comes from.

To explain the quantities observed, the researchers think that not only is it debris from asteroids and comets, but the gravitational instabilities that throw the system into chaos are booting any moons — so-called exomoons — out of their orbits around exoplanets, causing them to careen into the white dwarfs.

The simulations also suggest that as the moons meander around the inner star system and fall toward the star, their gravities scramble to orbits of more asteroids and comets, boosting the around of material falling into the star’s atmosphere.

So there you have it, planets, should your star turn into a white dwarf (as our sun will in a few billion years), keep your moons close — your new stellar overlord will be asking for a sacrifice in no time.

Vast Magnetic Canyon Opens up on the Sun — Choppy Space Weather Incoming?

A “live” view of our sun’s corona (NASA/SDO)

As the sun dips into extremely low levels of activity before the current cycle’s “solar minimum”, a vast coronal hole has opened up in the sun’s lower atmosphere, sending a stream of fast-moving plasma our way.

To the untrained eye, this observation of the lower corona — the sun’s magnetically-dominated multi-million degree atmosphere — may look pretty dramatic. Like a vast rip in the sun’s disk, this particular coronal hole represents a huge region of “open” magnetic field lines reaching out into the solar system. Like a firehose, this open region is blasting the so-called fast solar wind in our direction and it could mean some choppy space weather is on the way.

As imaged by NASA’s Solar Dynamics Observatory today, this particular observation is sensitive to extreme ultraviolet radiation at a wavelength of 193 (19.3 nanometers) — the typical emission from a very ionized form of iron (iron-12, or FeXII) at a temperature of a million degrees Kelvin. In coronal holes, it looks as if there is little to no plasma at that temperature present, but that’s not the case; it’s just very rarefied as it’s traveling at tremendous speed and escaping into space.

The brighter regions represent closed field lines, basically big loops of magnetism that traps plasma at high density. Regions of close fieldlines cover the sun and coronal loops are known to contain hot plasma being energized by coronal heating processes.

When a coronal hole such as this rotates into view, we know that a stream of high-speed plasma is on the way and, in a few days, could have some interesting effects on Earth’s geomagnetic field. This same coronal hole made an appearance when it last rotated around the sun, generating some nice high-latitude auroras. Spaceweather.com predicts that the next stream will reach our planet on March 28th or 29th, potentially culminating in a “moderately strong” G2-class geomagnetic storm. The onset of geomagnetic storms can generate impressive auroral displays at high latitudes. Although not as dramatic as an Earth-directed coronal mass ejection or solar flare, the radiation environment in Earth orbit will no doubt increase.

The sun as seen right now by the SDO’s HMI instrument (NASA/SDO)

The sun is currently in a downward trend in activity and is expected to reach “solar minimum” by around 2019. As expected, sunspot numbers are decreasing steadily, meaning the internal magnetic dynamo of our nearest star is starting to ebb, reducing the likelihood of explosive events like flares and CMEs. This is all part of the natural 11-year cycle of our sun and, though activity is slowly ratcheting down its levels of activity, there’s still plenty of space weather action going on.

Mysterious Fomalhaut b Might Not Be an Exoplanet After All

The famous exoplanet was the first to be directly imaged by Hubble in 2008 but many mysteries surround its identity — so astronomers are testing the possibility that it might actually be an exotic neutron star.

NASA, ESA, P. Kalas, J. Graham, E. Chiang, E. Kite (University of California, Berkeley), M. Clampin (NASA Goddard Space Flight Center), M. Fitzgerald (Lawrence Livermore National Laboratory), and K. Stapelfeldt and J. Krist (NASA Jet Propulsion Laboratory)

Located 25 light-years from Earth, the bright star Fomalhaut is quite the celebrity. As part of a triple star system (its distant, yet gravitationally bound siblings are orange dwarf TW Piscis Austrini and M-type red dwarf LP 876-10) Fomalhaut is filled with an impressive field of debris, sharing a likeness with the Lord Of The Rings’Eye of Sauron.” And, in 2008, the eerie star system shot to fame as the host of the first ever directly-imaged exoplanet.

At the time, the Hubble Space Telescope spotted a mere speck in Fomalhaut’s “eye,” but in the years that followed the exoplanet was confirmed — it was a massive exoplanet approximately the size of Jupiter orbiting the star at a distance of around 100 AU (astronomical units, where 1 AU is the average distance the Earth orbits the sun). It was designated Fomalhaut b.

This was a big deal. Not only was it the first direct observation of a world orbiting another star, Hubble was the aging space telescope that found it. Although the exoplanet was confirmed in 2013 and the International Astronomical Union (IAU) officially named the exoplanet “Dagon” after a public vote in 2015, controversy surrounding the exoplanet was never far away, however.

Astronomers continue to pick at Fomalhaut’s mysteries and, in new research to be published in the journal Monthly Notices of the Royal Astronomical Society, Fomalhaut b’s identity has been thrown into doubt yet again.

“It has been hypothesized to be a planet, however there are issues with the observed colors of the object that do not fit planetary models,” the researchers write. “An alternative hypothesis is that the object is a neutron star in the near fore- or background of Fomalhaut’s disk.” The research team is lead by Katja Poppenhaeger, of Queen’s University, Belfast, and a preprint of their paper (“A Test of the Neutron Star Hypothesis for Fomalhaut b”) can be found via arXiv.org.

Artist’s impression of Fomalhaut b inside its star’s debris disk (ESA, NASA, and L. Calcada – ESO for STScI)

Fomalhaut b was detected in visible and near-infrared wavelengths, but followup studies in other wavelengths revealed some peculiarities. For starters, the object is very bright in blue wavelengths, something that doesn’t quite fit with exoplanetary formation models. To account for this, theorists pointed to a possible planetary accretion disk like a system of rings. This may be the reason for the blue excess; the debris is reflecting more starlight than would be expected to be reflected by the planet alone. However, when other studies revealed the object is orbiting outside the star system’s orbital plane, this explanation wasn’t fully consistent with what astronomers were seeing.

Other explanations were put forward — could it be a small, warm world with lots of planetesimals surrounding it? Or is it just a clump of loosely-bound material and not a planet at all? — but none seem to quite fit the bill.

In this new research, Poppenhaeger’s team pondered the idea that Fomalhaut b might actually be a neutron star either in front or behind the Fomalhaut debris disk and, although their work hasn’t proven whether Fomalhaut b is an exoplanet or not, they’ve managed to put some limits on the neutron star hypothesis.

Neutron stars are the left-overs of massive stars that have run out of fuel and gone supernova. They are exotic objects that are extremely dense and small and, from our perspective, may produce emissions in visible and infrared wavelengths that resemble a planetary body. Cool and old neutron stars will even generate bluer light, which could explain the strange Fomalhaut b spectra.

Neutron stars also produce ultraviolet light and X-rays and, although it is hard to separate the UV light coming from the exoplanet and the UV light coming from the star, X-ray emissions should be resolvable.

Artist’s impression of a magnetar, an extreme example of a neutron star (ESO/L.Calçada)

So, using observations from NASA’s Chandra X-ray Observatory, the researchers looked at Fomalhaut b in soft X-rays and were able to put some pretty strong constraints on whether or not this object really could be a neutron star. As it turned out, Chandra didn’t detect X-rays (within its capabilities). This doesn’t necessarily mean that it isn’t a neutron star, it constrains what kind of neutron star it could be. Interestingly, it also reveals how far away this object could be.

Assuming it is a neutron star with a typical radius of 10 kilometers, and as no X-ray emissions within Chandra’s wavelength range were detected, this object would be a neutron star with a surface temperature cooler than 90,000 Kelvin — revealing that it is over 10 million years old. For this hypothesis to hold, the neutron star would actually lie behind the Fomalhaut system, around 44 light-years (13.5 parsecs) from Earth.

Further studies are obviously needed and, although the researchers point out that Fomalhaut b is still most likely an exoplanet with an extensive ring system (just with some strange and as-yet unexplained characteristics), it’s interesting to think that it could also be a neutron star that isn’t actually in the Fomalhaut system at all. In fact, it could be the closest neutron star to Earth, providing a wonderful opportunity for astronomical studies of these strange and exotic objects.

ALMA Reveals the True Nature of Hubble’s Enigmatic Ghost Spiral

Appearing as a ghostly apparition in deep space, the LL Pegasi spiral nebula signals the death of a star — and the world’s most powerful radio observatory has delved into its deeper meaning.

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Left: HST image of LL Pegasi publicized in 2010. Credit: ESA/NASA & R. Sahai. Right: ALMA image of LL Pegasi. Credit: ALMA (ESO/NAOJ/NRAO) / Hyosun Kim et al.

When the Hubble Space Telescope revealed the stunning LL Pegasi spiral for the first time, its ghostly appearance captivated the world.

Known to be an ancient, massive star, LL Pegasi is dying and shedding huge quantities of gas and dust into space. But this is no ordinary dying star, this is a binary system that is going out in style.

The concentric rings in the star system’s nebula are spiraling outwards, like the streams of water being ejected from a lawn sprinkler’s head. On initial inspection of the Hubble observation, it was assumed that the spiral must be caused by the near-circular orbit of two stars, one of which is generating the flood of gas. Judging by the symmetry of the rings, this system must be pointing roughly face-on, from our perspective.

Though these assumptions generally hold true, new follow-up observations by the Atacama Large Millimeter/submillimeter Array (ALMA) on the 5,000 meter-high Chajnantor plateau in Chile has added extra depth to the initial Hubble observations. Astronomers have used the incredible power of ALMA to see a pattern in the rings, revealing the complex orbital dynamics at play deep in the center of the spiral.

“It is exciting to see such a beautiful spiral-shell pattern in the sky. Our observations have revealed the exquisitely ordered three-dimensional geometry of this spiral-shell pattern, and we have produced a very satisfying theory to account for its details,” said Hyosun Kim, of the Academia Sinica Institute of Astronomy and Astrophysics (ASIAA) in Taiwan and lead researcher of this work.

Just as we read tree rings to understand the history of seasonal tree growth and climatic conditions, Kim’s team used the rings of LL Pegasi to learn about the nature of the binary star’s 800 year orbit. One of the key findings was the ALMA imaging of bifurcation in the rings; after comparing with theoretical models, they found that these features are an indicator that the central stars’ orbit is not circular — it’s in fact highly elliptical.

ALMA observation of the molecular gas around LL Pegasi. By comparing this gas distribution with theoretical simulations, the team concluded that the bifurcation of the spiral-shell pattern (indicated by a white box) is resulted from a highly elliptical binary system. Credit: ALMA (ESO/NAOJ/NRAO) / Hyosun Kim et al.

Probably most striking, however, was that Hubble was only able to image the 2D projection of what is in fact a 3D object, something that ALMA could investigate. By measuring the line-of-sight velocities of gas being ejected from the central star, ALMA was able to create a three-dimensional view of the nebula, with the help of numerical modeling. Watch the animation below:

“While the [Hubble Space Telescope] image shows us the beautiful spiral structure, it is a 2D projection of a 3D shape, which becomes fully revealed in the ALMA data,” added co-author Raghvendra Sahai, of NASA’s Jet Propulsion Laboratory in Pasadena, Calif., in a statement.

This research is a showcase of the power of combining observations from different telescopes. Hubble was able to produce a dazzling (2D) picture of the side-on structure of LL Pegasi’s spirals, but ALMA’s precision measurements of gas outflow speed added (3D) depth, helping us “see” an otherwise hidden structure, while revealing the orbital dynamics of two distant stars.

A special thanks to Hyosun Kim for sending me the video of the LL Pegasi visualization!

Plasmaloopalicious!

The magnetic loop containing hydrogen and nitrogen plasma evolves over 4 micro-seconds. Credit: Bellan & Stenson, 2012
The magnetic loop containing hydrogen and nitrogen plasma evolves over 4 micro-seconds. Credit: Bellan & Stenson, 2012

There’s no better method to understand how something works than to build it yourself. Although computer simulations can help you avoid blowing up a city block when trying to understand the physics behind a supernova, it’s sometimes just nice to physically model space phenomena in the lab.

So, two Caltech researchers have done just that in an attempt to understand a beautifully elegant, yet frightfully violent, solar phenomenon: coronal loops. These loops of magnetism and plasma dominate the lower corona and are particularly visible during periods of intense solar activity (like, now). Although they may look nice and decorative from a distance, these loops are wonderfully dynamic and are often the sites of some of the most energetic eruptions in our Solar System. Coronal loops spawn solar flares and solar flares can really mess with our hi-tech civilization.

A coronal loop as seen by NASA's Transition Region and Coronal Explorer (TRACE). Credit: NASA
A coronal loop as seen by NASA’s Transition Region and Coronal Explorer (TRACE). Credit: NASA

In an attempt to understand the large-scale dynamics of a coronal loop, Paul Bellan, professor of applied physics at Caltech, and graduate student Eve Stenson built a dinky “coronal loop” of their own (pictured top). Inside a vacuum chamber, the duo hooked up an electromagnet (to create the magnetic “loop”) and then injected hydrogen and nitrogen gas into the two “footpoints” of the loop. Then, they zapped the whole thing with a high-voltage current and voila! a plasma loop — a coronal loop analog — was born.

Although coronal loops on the sun can last hours or even days, this lab-made plasma loop lasted a fraction of a second. But by using a high-speed camera and color filters, the researchers were able to observe the rapid expansion of the magnetic loop and watch the plasma race from one footpoint to the other. Interestingly, the two types of plasma flowed in opposite directions, passing through each other.

The simulation was over in a flash, but they were able to deduce some of the physics behind their plasma loop: “One force expands the arch radius and so lengthens the loop while the other continuously injects plasma from both ends into the loop,” Bellan explained. “This latter force injects just the right amount of plasma to keep the density in the loop constant as it lengthens.” It is hoped that experiments like these will ultimately aid the development of space weather models — after all, it would be useful if we could deduce which coronal loops are ripe to erupt while others live out a quiescent existence.

It’s practical experiments like these that excite me. During my PhD research, my research group simulated steady-state coronal loops in the hope of explaining some of the characteristics of these fascinating solar structures. Of particular interest was to understand how magnetohydrodynamic waves interact with the plasma contained within the huge loops of magnetism. But all my research was based on lines of code to simulate our best ideas on the physical mechanisms at work inside these loops. Although modelling space phenomena is a critical component of science, it’s nice to compare results with experiments that aim to create analogs of large-scale phenomena.

The next test for Bellan and Stenson is to create two plasma loops inside their vacuum chamber to see how they interact. It would be awesome to see if they can initiate reconnection between the loops to see how the plasma contained within reacts. That is, after all, the fundamental trigger of explosive events on the Sun.

Read more in my Discovery News article: “Precursors to Solar Eruptions Created in the Lab