Posted on by Shannon Hall

First Microlensing Detection of a Planet Circling a Brown Dwarf Candidate

This artist's conception could resemble a planetary system in front of a background star. Image Credit: NASA Goddard Space Flight Center / Francis Reddy

When astronomers detect new exoplanets they typically do so using one of two techniques. First, there’s the famous transit technique, which looks for slight dips in light as a planet passes in front of its host star, and second is the radial velocity technique, which senses the motion of a star due to the gravitational pull of its planet.

But then there is gravitational microlensing, the chance magnification of the light from a distant star by the mass of a foreground star and its planets due to the distortion in the fabric of spacetime. While this technique sounds almost improbable, it is so accurate that every detection skips nominating planets as candidates and immediately verifies them as bona-fide worlds.

But without follow-up observations, the microlensing technique struggles with characterizing the incredibly faint host star. Now, a team of international astronomers led by PhD candidate Jennifer Yee from Ohio State University has detected the first microlensing signature, lovingly called MOA-2013-BLG-220Lb, that looks like a confirmed planet orbiting a candidate brown dwarf — an object so faint because it isn’t massive enough to kick-off nuclear fusion in its core.

Matter — no matter how great or small — curves the fabric of spacetime. It can ultimately acts like a lens by curving the background light around it and therefore magnifying the background source. In microlensing, the intervening matter is simply a faint star or perhaps a planetary system.

“As the ‘lens system’ passes in front of a distant, background star, the magnification of that background star changes as a function of time,” Yee told Universe Today. “By measuring the changing magnification of the background star, we can learn about the lensing star and perhaps whether or not it has a planet.”

In a planetary system, the light from the background star will be magnified when the foreground star passes in front of it. If there is a cirlcing planet, there will be an additional cusp in brightness (to a lesser extent but still a tell-tale detection nonetheless).

A sketch of a microlensing signature with a planet in the lens system. Image Credit: NASA / ESA / K. Sahu / STScI
A sketch of a microlensing signature with a planet in the lens system. Image Credit: NASA / ESA / K. Sahu / STScI

At the moment the planetary system transits in front of the background star (and for many years after) we can’t separate the two objects. While the light of the background star may be greatly magnified, its image is distorted because its light merges with the planetary system.

So the microlensing signature cannot tell astronomers anything about the lens system’s star. “It’s out of the ordinary,” Andrew Gould, Yee’s PhD advisor and coauthor on the paper, told Universe Today. “In other techniques people have definitely detected a star and they’re struggling to detect the planet. But microlensing is just the opposite. We detect the planet very clearly, but we can’t detect the host star.”

However, the microlensing signature does give away the lens system’s proper motion — the apparent change in distance over time — as it passes in front of the background star. MOA-2013-BLG-220Lb’s proper motion is extremely high, clocking in at 12.5 milliarcseconds (a distance on the sky that is 2400 times smaller than the size of the full moon) per year. This is roughly three times higher than average.

A high proper motion may be caused by an object that is very close by and is moving slowly or a very distant object moving rapidly. As most stars tend not to move at high speeds, the team assumes the object is relatively close, placing it at a distance of 6,000 light-years.

With a distance fixed, the team is also able to assume a mass for the object. It weighs in below the hydrogen-burning limit and is therefore considered the best brown dwarf candidate microlensing has detected.

“The double-edged sword of microlensing is that no light from the lens star is required,” Yee told Universe Today. “On the one hand, microlensing can find planets around dark or faint objects like brown dwarfs. The flip side is that it’s very difficult to characterize the lens star if its light is not detected.”

Astronomers will have to wait until 2021 to take a second look at the lens system. This time frame is how long we expect it to take before the candidate brown dwarf separates appreciably on the sky from the background star. Once it has done so astronomers will be able to verify whether or not the candidate is truly a brown dwarf.

The paper is available for download here.

Posted on by Shannon Hall

Landmark Discovery: New Results Provide Direct Evidence for Cosmic Inflation

The BICEP telescope located at the south pole. Image Credit: CfA / Harvard

Astronomers have announced Nobel Prize-worthy evidence of primordial gravitational waves — ripples in the fabric of spacetime — providing the first direct evidence the universe underwent a brief but stupendously accelerated expansion immediately following the big bang.

“The implications for this detection stagger the mind,” said co-leader Jamie Bock from Caltech. “We are measuring a signal that comes from the dawn of time.”

BICEP2 (Background Imaging of Cosmic Extragalactic Polarization) scans the sky from the south pole, looking for a subtle effect in the cosmic microwave background (CMB) — the radiation released 380,000 years after the Big Bang when the universe cooled enough to allow photons to travel freely across the cosmos.

The CMB fills every cubic centimeter of the observable universe with approximately 400 microwave photons. The so-called afterglow of the big bang is nearly uniform in all directions, but small residual variations (on the level of one in 100,000) in temperature show a specific pattern. These irregularities match what would be expected if minute quantum fluctuations had ballooned to the size of the observable universe today.

So astronomers dreamed up the theory of inflation — the epoch immediately following the big bang (10-34 seconds later) when the universe expanded exponentially (by at least a factor of 1025) — causing quantum fluctuations to magnify to cosmic size. Not only does inflation help explain why the universe is so smooth on such massive scales, but also why it’s flat when there’s an infinite number of other possible curvatures.

While inflation is a pillar of big bang cosmology, it has remained purely a theoretical framework. Many astronomers don’t buy it as we can’t explain what physical mechanism would have driven such a massive expansion, let alone stop it. The results announced today provide a strong case in support of inflation.

In Depth: We’ve Discovered Inflation! Now What?

The trick is in looking at the CMB where inflation’s signature is imprinted as incredibly faint patterns of polarized light — some of the light waves have a preferred plane of vibration. If a gravitational wave passes through the fabric of spacetime it will squeeze spacetime in one direction (making it hotter) and stretch it in another (making it cooler). Inflation will then amplify these quantum fluctuations into a detectable signal: the hotter and therefore more energetic photons will be visible in the CMB, leaving a slight polarization imprint.

E-modes (left side)
E-modes (left side) look the same when reflected in a mirror. B-modes (right side) do not. Image Credit: Nathan Miller

This effect will create two distinct patterns: E-modes and B-modes, which are differentiated based on whether or not they have even or odd parity. In simpler terms: E-mode patterns will look the same when reflected in a mirror, whereas B-mode patterns will not.

E-modes have already been extensively detected and studied. While both are the result of primordial gravitational waves, E-modes can be produced through multiple mechanisms whereas B-modes can only be produced via primordial gravitational waves. Detecting the latter is a clean diagnostic — or as astronomers are putting it: “smoking gun evidence” — of inflation, which amplified gravitational waves in the early Universe.

“The swirly B-mode pattern is a unique signature of gravitational waves because of their handedness. This is the first direct image of gravitational waves across the primordial sky,” said co-leader Chao-Lin Kuo from Stanford University, designer of the BICEP2 detector.

Polarization patterns imprinted in the CMB. Image Credit: CfA
Shown here are the actual B-mode polarization patterns provided by the BICEP2 Telescope. Image Credit: Harvard-Smithsonian Center for Astrophysics

The team analyzed sections of the sky spanning one to five degrees (two to 10 times the size of the full moon) for more than three years. They created a unique array of 512 detectors, which collectively operate at a frosty 0.25 Kelvin. This new technology enabled them to make detections at a speed 10 times faster than before.

The results are surprisingly robust, with a 5.9 sigma detection. For comparison, when particle physicists announced the discovery of the Higgs Boson in July, 2012 they had to reach at least a 5 sigma result, or a confidence level of 99.9999 percent.  At this level, the chance that the result is erroneous due to random statistical fluctuations is only one in a million. Those are pretty good odds.

While the team was careful to rule out any errors, it will be crucial for another team to verify these results. The Planck spacecraft, which has been producing exquisite measurements of the CMB, will be reporting its own findings later this year. At least a dozen other teams have also been searching for this signature.

“This work offers new insights into some of our most basic questions: Why do we exist? How did the universe begin?” commented Harvard theorist Avi Loeb. “These results are not only a smoking gun for inflation, they also tell us when inflation took place and how powerful the process was.”

Not only does inflation succeed in explaining the origin of cosmic structure — how the cosmic web formed from the smooth aftermath of the big bang — but it makes wilder predictions as well. The model seems to produce not just one universe, but rather an ensemble of universes, otherwise known as a multiverse. This collection of universes has no end and no beginning, continuing to pop up eternally.

Today’s results provide a stronger case for “eternal inflation,” which gives a new perspective on our desolate place within the cosmos. Not only do we live on a small planet orbiting one star out of hundreds of billions, in one galaxy out of hundreds of billions, but our entire universe may just be one bubble out of a vast cosmic ocean of others.

The detailed paper may be found here.
The full set of papers are here.
An FAQ summarizing the data is here.

Posted on by Shannon Hall

Rumors Flying Nearly as Fast as Their Subject: Have Gravitational Waves Been Detected?

This detailed map of the cosmic microwave background is created from seven years worth of data. Image Credit: NASA

Last week the Harvard-Smithsonian Center for Astrophysics (CfA) stated rather nonchalantly that they will be hosting a press conference on Monday, March 17th, to announce a “major discovery.” Without a potential topic for journalists to muse on, this was as melodramatic as it got.

But then the Guardian posted an article on the subject and the rumors went into overdrive. The speculation is this: a U.S. team is on the verge of confirming they have detected primordial gravitational waves — ripples in the fabric of spacetime that carry echoes of the big bang nearly 14 billion years ago.

If there is evidence for gravitational waves, it will be a landmark discovery, ultimately changing the face of physics.

Not only are gravitational waves the last untested prediction of Albert Einstein’s General Theory of Relativity, but primordial gravitational waves will allow astronomers to glimpse the universe in its infancy.

“It’s been called the Holy Grail of cosmology,” Hiranya Peiris, a cosmologist from University College London, told the Guardian. “It would be a real major, major, major discovery.” Any convincing evidence would almost certainly lead to a Nobel prize.

The signal is rumored to have been found by a telescope known as BICEP (Background Imaging of Cosmic Extragalactic Polarization), which scans the sky from the south pole, looking for a subtle effect in the cosmic microwave background (CMB): the radiation released 380,000 years after the big bang when space became transparent to light and photons were allowed to travel freely across the universe.

The South Pole Telescope (left) and BICEP (right). Image Credit: Dana Hrubes
The South Pole Telescope (left) and BICEP (right). Image Credit: Dana Hrubes

While the CMB has been mapped in exquisite detail, astronomers think that hidden within the map is a second fingerprint, which would reveal gravitational waves. Its radiation was scattered toward us from the universe’s earliest atoms, similar to the way blue light is scattered toward us from the atoms in the sky. And just as the sky is slightly polarized — the waves have a preferred orientation — so is the CMB (on the level of a few percent).

Cosmologists are digging through the data, searching for a subtle twist in the polarized light, known as B-modes. If a gravitational wave moves through the fabric of spacetime, it will squeeze spacetime in one direction (the universe will look a little hotter) and stretch it in another (the universe will look a little cooler). The photons will scatter with a preferred direction, leaving a slightly polarized imprint on the CMB, due to the passing gravitational wave.

Not only will detecting this slight polarization pattern in the CMB allow astronomers to uncover evidence of primordial gravitational waves but they will provide proof that immediately after the big bang the universe expanded exponentially — inflated — by at least a factor of 1025. While the theory of inflation is a pillar of big bang cosmology and helps explain key features of the observable universe today (i.e. why the universe is outstandingly uniform on such massive scales), many physicists don’t buy it. It remains a theoretical framework because we can’t explain what physical mechanism would have driven such a massive expansion, let alone stop it.

Inflation is the only mechanism with the ability to amplify gravitational waves, born from quantum fluctuations in gravity itself, into a detectable signal.

“If a detection has been made, it is extraordinarily exciting,” Andrew Jaffe, a cosmologist from Imperial College, London, told the Guardian. “This is the real big tick-box that we have been waiting for. It will tell us something incredibly fundamental about what was happening when the universe was only 10-34 seconds old.”

But even if the rumors prove true, it’s crucial to remain skeptical. Extracting the signal is extremely tricky. The CMB’s temperature varies by a few parts in 100,000. In comparison, B-modes account for just one part in 10 million in the CMB temperature distribution.

The microwaves also travel across the entire observable universe first. Only last year the signal was detected in the CMB for the first time using the South Pole Telescope, but it was in fact distorted by intervening clusters of galaxies and not intrinsic to the CMB itself.

The announcement will be made on Monday at noon EST.

Posted on by Shannon Hall

Physicists Reveal the Hidden Interiors of Gas Giants

Looped movie of the hydrogen jet in the sample chamber. Credit: Sven Toleikis/DESY

In astronomy we love focusing on the bigger picture. We’re searching for exoplanets in the vast hope that we may begin to paint a picture of how planetary systems form; We’re using the Hubble Space Telescope to peer into the earliest history of the cosmos; And we’re building gravitational wave detectors in order to better understand the physical laws that dominate our universe.

All the while we continue to learn about our very own neighborhood. Only recently we learned that Europa has geysers, Mars was perhaps once a lush planet, and comets can in fact disintegrate. Discoveries in our solar system alone never cease to amaze.

For the first time researchers are able to probe the hidden interiors of gas giants such as Jupiter and Saturn. With very little experimental knowledge about the hydrogen deep within such planets, we have always had to rely on mathematical models. But now, researchers have simulated the lower atmospheric layers of these planets in the lab.

The team of physicists led by Dr. Ulf Zastrau from the University of Jena heated cold liquid hydrogen to resemble the dense liquid hydrogen deep within a gas giant’s atmospheric layers.

The team used an X-ray laser operated by a national research center in Germany, Deutsches Elektronen-Synchrotron (DESY), to heat the liquid hydrogen, nearly instantaneously, from -253 to +12,000 degrees Celsius. Initially the X-ray heats only the electrons. But because each electron is bound to a proton, they transfer heat to the proton until a thermal equilibrium is reached. The molecular bonds break during this process, and a plasma of electrons and protons is formed.

In just under a trillionth of a second, physicists are able to create a plasma that’s thought to be radically similar to the plasma deep within the atmospheres of our beloved gas giants.

But first the team had to create cold hydrogen. While it’s abundant throughout the universe, it’s hard to get our hands on the stuff here on Earth. Instead researchers cooled gaseous hydrogen to -253 degrees Celsius using liquid helium. This was a very temperamental process, requiring precise temperature control. If the hydrogen got too cold it would freeze and the researchers would have to use a small heater to re-liquefy it. At the end of the day a jet of cold liquid hydrogen with a diameter no greater than 20 micrometers would flow into a vacuum.

Physicists would then shoot intense pulses of the X-ray laser at the cold hydrogen. They could control the precise timing of the X-ray laser’s “flash” in order to study the properties of liquid hydrogen. The first half of the flash heats up the hydrogen, but the second half of the flash is delayed by varying lengths, which allows the team to understand exactly how thermal equilibrium is established between the electrons and the protons.

The experimental results provide information on the liquid hydrogen’s thermal conductivity and its internal energy exchange, which are both crucial to better understanding gas giants. The experiments will have to be repeated at other temperatures and pressures in order to create a detailed picture of the entire planetary atmosphere.

“Hopefully the results will provide us among others with an experimentally based answer to the question, why the planets discovered outside our solar system do not exist in all imaginable combinations of properties as age, mass, size or elemental composition, but may be allocated to certain groups,” said Dr. Thomas Tschentscher, scientific director of the European XFEL X-ray laser in a press release.

The paper has been accepted in the scientific journal Physical Review Letters and is available for download here.

Posted on by Shannon Hall

New Technique Could Measure Exoplanet Atmospheric Pressure, an Indicator of Habitability

Artistic representations of the only known planets around other stars (exoplanets) with any possibility to support life as we know it. The authors of this study wanted to know how people react to the discovery of alien life and potentially habitable planets. Credit: Planetary Habitability Laboratory, University of Puerto Rico, Arecibo.

Measuring the atmospheric pressure of a distant exoplanet may seem like a daunting task but astronomers at the University of Washington have now developed a new technique to do just that.

When exoplanet discoveries first started rolling in, astronomers laid emphasis in finding planets within the habitable zone — the band around a star where water neither freezes nor boils. But characterizing the environment and habitability of an exoplanet doesn’t depend on the planet’s surface temperature alone.

Atmospheric pressure is just as important in gauging whether or not the surface of an exoplanet may likely hold liquid water. Anyone familiar with camping at high-altitude should have a good understanding of how pressure affects water’s boiling point.

The method developed by Amit Misra, a PhD candidate, involves isolating “dimers” — bonded pairs of molecules that tend to form at high pressures and densities in a planet’s atmosphere — not to be confused with “monomers,” which are simply free-floating molecules. While there are many types of dimers, the research team focused exclusively on oxygen molecules, which are temporarily bound to each other through hydrogen bonding.

We may indirectly detect dimers in an exoplanet’s atmosphere when the exoplanet transits in front of its host star. As the star’s light passes through a thin layer of the planet’s atmosphere the dimers absorb certain wavelengths of it. Once the starlight reaches Earth it’s imprinted with the chemical fingerprints of the dimers.

Dimers absorb light in a distinctive pattern, which typically has four peaks due to the rotational motion of the molecules. But the amount of absorption may change depending on the atmospheric pressure and density. This difference is much more pronounced in dimers than in monomers, allowing astronomers to gain additional information about the atmospheric pressure based on the ratio of these two signatures.

While water dimers were detected in the Earth’s atmosphere as early as last year, powerful telescopes soon to come online may enable astronomers to use this method in observing distant exoplanets. The team analyzed the likelihood of using the James Webb Space Telescope to make such a detection and found it challenging but possible.

Detecting dimers in an exoplanet’s atmosphere would not only help us evaluate the atmospheric pressure, and therefore the state of water on the surface, but other biosignature markers as well. Oxygen is directly tied to photosynthesis, and will most likely not be abundant in an exoplanet’s atmosphere unless it is regularly produced by algae or other plants.

“So if we find a good target planet, and you could detect these dimer molecules — which might be possible within the next 10 to 15 years — that would not only tell you something about pressure, but actually tell you that there’s life on that planet,” said Misra in a press release.

The paper has been published in the February issue of Astrobiology and is available for download here.

Posted on by Shannon Hall

“Climate Change is Now More Certain Than Ever,” New Report Says

Image Credit: NASA

Climate change is one of the defining issues of our time. So begins the latest report by the U.S. National Academy of Sciences and the United Kingdom’s Royal Society. The two institutions agree: climate change is not only indisputable, it’s largely the result of human activities.

The bulk of the 36-page report is presented in a question-and-answer format, making it a good bed-side read. But in case you don’t want to have nightmares about surging temperatures or polar bears alone on breaking ice caps, we’ll leaf through the intriguing points here.

In a forward to the report, Dr. Ralph J. Cicerone, president of the National Academy of Sciences, and Sir Paul Nurse, president of the Royal Society argue that multiple lines of evidence show that humans are changing Earth’s climate. This is now more certain than ever.

They are careful to include a caveat: “The evidence is clear. However, due to the nature of science, not every single detail is ever totally settled or completely certain. Nor has every pertinent question yet been answered.” Areas of active debate include how much warming to expect in the future and the connections between climate change and extreme weather events such as the frequency and intensity of hurricanes, droughts and floods.

Earth’s global average surface temperature has risen as shown in this plot of combined land and ocean measurements from 1850 to 2012, derived from three independent analyses of the available data sets. The temperature changes are relative to the global average surface temperature of 1961?1990. Source: IPCC AR5, data from the HadCRUT4 dataset (black), UK Met Office Hadley Centre, the NCDC MLOST dataset (orange), US National Oceanic and Atmospheric Administration, and the NASA GISS dataset (blue), US National Aeronautics and Space Administration.
Earth’s global average surface temperature has risen as shown in this plot of combined land and ocean measurements from 1850 to 2012, derived from three independent analyses of the available data sets. Image Credit: National Academy of Sciences / The Royal Society

But the first question: is the climate warming? goes without debate. Yes. Earth’s average surface air temperature has increased by about 0.8 degrees Celsius since 1900, and the last 30 years have been the warmest in 800 years. It’s the most rapid period of sustained temperature change in the scale of global history, trumping every ice age cycle.

Recent estimates of the increase in global temperature since the end of the last ice age are four to five degrees Celsius. While this is much greater than the 0.8 degree Celsius change recorded over the last 100+ years, this change occurred over a period of about 7,000 years. So the change in rate is now 10 times faster.

Of course an increase in temperature goes hand in hand with an increase in carbon emissions. Greenhouse gases such as carbon dioxide absorb heat (infrared radiation) emitted from the Earth’s surface. Increases in the atmospheric concentrations of these gases trap most of the outgoing heat, causing the Earth to warm. Human activities, especially the burning of fossil fuels have increased carbon dioxide concentrations by 40 percent between 1880 and 2012. It is now higher than at any time in at least 800,000 years.

And if the rise in carbon emissions continues unchecked, warming of the same magnitude as the increase out of the last ice age can be expected by the end of this century.

The report continues to ask more controversial questions. Take as an example the question: Does the recent slowdown of warming mean that climate change is no longer happening? The short answer is no. Decades of slow warming and accelerated warming occur naturally in the climate system. Despite the slower rate of warming the 2000’s were still warmer than the 1990’s

The new report builds upon the long history of climate-related work from the United Nations’ Intergovernmental Panel on Climate Change. So while some have argued it doesn’t add anything new to the wealth of climate science data available, it does help make that data more succinct and available to the public. Its goal is to help inform decision makers, policy makers, educators and all other individuals.

The report concludes by noting available options to citizens and governments. They can simply wait and accept the losses, they can change their pattern of energy production, they can attempt to adapt to environmental changes as much as possible, or they can seek as yet unproven geoengineering solutions.

No matter which option we choose, one thing remains certain: the Earth is warming at a tremendous rate and we are the cause.

The paper is available for download here.

Posted on by Shannon Hall

Nearby Stream of Stars Reveals Past Cosmic Collision

The 51st entry in Charles Messier's famous catalog is perhaps the original spiral nebula--a large galaxy with a well defined spiral structure also cataloged as NGC 5194. Over 60,000 light-years across, M51's spiral arms and dust lanes clearly sweep in front of its companion galaxy, NGC 5195. Image data from the Hubble's Advanced Camera for Surveys was reprocessed to produce this alternative portrait of the well-known interacting galaxy pair. The processing sharpened details and enhanced color and contrast in otherwise faint areas, bringing out dust lanes and extended streams that cross the small companion, along with features in the surroundings and core of M51 itself. The pair are about 31 million light-years distant. Not far on the sky from the handle of the Big Dipper, they officially lie within the boundaries of the small constellation Canes Venatici. Image Credit: NASA

The tangled remains of vast cosmic collisions can be seen across the universe, such as the distant Whirlpool Galaxy’s past close encounter with a nearby galaxy, which resulted in the staggering beauty we see today.

Such colossal collisions between galaxies appear to be common. It’s likely giant galaxies, such as our own, originated long ago after smaller dwarf galaxies crashed together. Unfortunately, Hubble has yet to peer into the early Universe and catch two dwarf galaxies merging by chance. And they’re extremely rare to catch in the present nearby universe.

But for the first time, astronomers have uncovered evidence of a similar collision much closer to home.

The Milky Way is part of a large cosmic neighborhood. A collection of more than 35 galaxies compose the Local Group. While the largest and heavier members are the Milky Way and the Andromeda galaxy, there are many smaller satellite galaxies orbiting the two.  Anyone who has looked at the southern sky should be familiar with the Large and Small Magellanic Clouds: two satellite galaxies of the Milky Way less than 200,000 light years away.

Andromeda has over 20 satellite galaxies circling its nearly a trillion stars. A team of European astronomers has analyzed measurements of the stars in the dwarf galaxy Andromeda II — the second largest dwarf galaxy in the Local Group — and made a surprising discovery: an odd stream of stars that simply doesn’t belong.

The team led by Dr. Nicola C. Amorisco from the Dark Cosmology Centre at the Niels Bohr Institute in Copenhagen used the Deep Imaging Multi-Object (DEIMOS) spectrograph onboard the Keck II telescope in Hawaii in order to measure the velocities of more than 700 stars in the Andromeda II dwarf galaxy.

Stars in a large spiral galaxy will move, on average, with the rotation of the galaxy. On one side of the galaxy’s spinning disk, the stars will be moving away from the Earth, and their light waves will be stretched to redder wavelengths. On the opposite side, the stars will be moving toward the Earth, and their light waves will be compressed to bluer wavelengths.

But the stars in dwarf galaxies don’t exhibit such a pattern. Instead they move around entirely at random.

Amorisco and colleagues, however, found a rather different case present in Andromeda II. They observed a stream of stars — roughly 16,000 light years in length and 980 light years in thickness — that didn’t exhibit random motions at all. They orbit the center of the galaxy in a very coherent fashion.

But it gets better: the stars in this stream are also much colder than the stars outside the stream. In astronomy this is the equivalent of saying that the stars in this stream are much older. Amorisco’s team now believes they once belonged to a different galaxy entirely and remain only as a remnant of the past collision, which likely occurred over 3 billion years ago.

Streams of stars often result from collisions. As two galaxies begin to interact, the stars nearest the approaching galaxy feel a much stronger gravitational pull than the stars further away. Eventually the gravitational pull on the closer side of the galaxy will pull the stars from their initial galaxy, creating a stream of stars, dust and gas.

This is the smallest known example of two galaxies merging. The finding adds further evidence that mergers between dwarf galaxies plays a fundamental role in creating the large and beautiful galaxies we see today.

The paper has been published in Nature and is available for download here.

Posted on by Shannon Hall

Is Eta Carinae Heading Toward Another Eruption?

Eta Car

Massive stars can devastate their surroundings, unleashing hot winds and blasting radiation. With a mass over 100 times heavier than the Sun and a luminosity a million times brighter than the Sun, Eta Carinae clocks in as one of the biggest and brightest stars in our galaxy.

The enigmatic object walks a thin line between stellar stability and tumultuous explosions. But now a team of international astronomers is growing concerned that it’s leaning toward instability and eruption.

In the 19th Century the star mysteriously threw off unusually bright light for two decades in an event that became known as the “Great Eruption,” the causes of which are still up for debate. John Herschel and others watched as Eta Carinae’s brightness oscillated around that of Vega — rivaling a supernova explosion.

We now know the star ejected material in the form of two big globes. “During the eruption the star threw off more than 10 solar masses, which can now be observed as the surrounding bipolar nebula,” said lead author Dr. Andrea Mehner from the European Southern Observatory. Miraculously the star survived, but the nebula has been expanding into space ever since.

Eta Carinae has been observed at the South African Astronomical Observatory — a 0.75m telescope outside of Cape Town — for more than 40 years, providing a wealth of data. From the start of observations in 1976 until 1998, astronomers saw an increase across the J, H, K and L bands — filters, which allow certain wavelength ranges of infrared light to pass through.

“This data set is unique for its consistency over a timespan of more than 40 years,” Mehner told Universe Today. “It provides us with the opportunity to analyze long-term changes in the system as Eta Carinae still recovers from its Great Eruption.”

In order to understand the longterm overall increase in light we have to look at a more recent discovery noted in 2005 when scientists discovered that Eta Carinae is actually two stars: a massive blue star and a smaller companion. The temperature increased for 15 years until the companion came very close to the massive star, reaching periastron.

This increase in brightness is likely due to an overall increase in temperature of some component of the Eta Carinae system (which includes the massive blue star, its smaller companion, and the shells of gas and dust that now enshroud the system).

After 1998, however, the linear trend changed significantly and the star’s brightness increased much more rapidly in the J and H bands. It’s getting bluer, which in astronomy, typically means it’s getting hotter.

However, it’s unlikely the star itself is getting hotter. Instead we are seeing the effect of dust around the star being destroyed rapidly. Dust absorbs blue light. So if the dust is getting destroyed, more blue light will be able to pass through the nebulous globes surrounding the system. If this is the case, then we’re really seeing the star as it truly is, without dust absorbing certain wavelengths of its light.

While the nebula is slowly expanding and the dust is therefore dissipating, the authors do not think it’s enough to account for the recent brightening. Instead Eta Carinae is likely rotating at a different speed or losing mass at a different rate. “The changes observed may imply that the star is becoming more unstable and may head towards another eruptive phase,” Mehner told Universe Today.

Perhaps Eta Carinae is heading toward another “Great Eruption.” Only time will tell. But in a field where most events occur on a timescale of millions of years, it’s a great opportunity to watch the system evolve on a human time scale. And when Eta Carinae reaches periastron in the middle of this year, tens of telescopes will be collecting its light, hoping to see a sudden turn of events that may help us explain this exotic system.

The paper has been accepted for publication in Astronomy & Astrophysics and is available for download here.

Posted on by Shannon Hall

NSF Report Biased, Expert Says: Americans Don’t Think Astrology is Scientific

Americans ...

Every Thanksgiving when I was home from college, at least one family member would turn to me and ask me how that astrology degree was going, or tell me about a new astrology article they read. It wasn’t that my family members really thought I was studying astrology or even believed astrology was scientific, it was just that they mixed up “astronomy” with “astrology.” In all fairness, for those who don’t follow either astrology or astronomy very closely, it might be considered an honest mistake.

So when a report from the National Science Foundation claimed a majority of young Americans believed astrology was scientific I had my doubts. But so did psychologist, Richard Landers from Old Dominion University who performed a small second study and found the report to be biased.

Since 1979, NSF surveys have asked Americans whether they view astrology — the study of how the movement of celestial bodies affects the here and now — as being scientific.

Their most recent survey showed that nearly half of all Americans (42 percent) believe astrology to be scientific. But what’s more alarming, according to the NSF, is that American understandings of science are moving in the wrong direction. It seems our golden year was in 2004, when 66 percent of Americans said astrology was not at all scientific. That number has been dropping ever since.

It should come as no surprise that those with a higher education are more willing to demote astrology entirely. In 2012, 72 percent of those with graduate degrees indicated that astrology is not scientific, compared with only 34 percent of those who didn’t graduate high school.

Shockingly, age was also related to perceptions of astrology. Younger respondents (ages 18-24) seemed to give astrology a high vote of confidence,with only 42 percent claiming that it isn’t scientific. So roughly six in every 10 young adults believe astrology is absolutely scientific.

But such dramatic conclusions are being drawn from a single question: “Is astrology scientific?” It’s based on the crucial assumption that people are correctly interpreting the word “astrology.”

Landers guessed that the survey respondents might be mixing up the term “astrology” with “astronomy.” So he performed a quick survey himself, using Amazon Mechanical Turk (MTurk) — a crowdsourcing internet marketplace. He collected 100 responses to a survey that asked three questions:

— Please define astrology in 25 words or less.
— Do you believe astrology to be scientific?
— What is your highest level of education completed?

His initial assessment — without taking into account how the respondent defined astrology — showed results very similar to the original survey provided by the NSF — approximately 30 percent found astrology to be scientific. While this percentage is less than what the NSF report found, Landers believes this is due to a user bias (MTurk users tend to be more educated and older than the average American).

But once Landers included the answer to the first question into his results, he saw a very clear trend: those who defined astrology correctly did not believe it to be scientific, while those who confused astrology with astronomy did believe it to be scientific.

Data collected from 100 participants using MTurk.
Data collected from 100 participants using MTurk. Image Credit: R. Landers

Among those that correctly identified astrology, only 13.5 percent found it to be “pretty scientific.” And only one person found it to be “very scientific.” Among those that confused astrology with astronomy, the discipline was overwhelmingly seen as scientific.

“My little quick study doesn’t ‘overturn’ the NSF results” Landers told Universe Today. “It only suggests that the NSF results are probably biased to some degree.”

With such small number statistics Landers certainly didn’t prove the NSF results wrong, but he does call the study into question. Landers also noted an additional study from the European Commission which corroborated his findings.

I for one would love to see the NSF conduct a more detailed study. Including a definition of astrology in the next round of surveys would certainly bring clarification and shed light on the root of the problem.

—

Update: After posting this article, a reader informed me of a critique of Richard landers’ assessment, posted by The Washington Post’s Jim Lindgren. He conducted another follow-up study to explore the issue. In his own sample, Lindgren found that probably only one respondent out of 108 confused “astrology” with “astronomy.” He claims it’s unlikely the NSF report was biased at all.

However, the back and forth banter between experts suggests these words and their corresponding definitions do need to be clarified. Science journalists have their work cut out for them.

Posted on by Shannon Hall

Zooniverse Reaches One Million Volunteers

A global map showing where all the volunteers are based. Image Credit: Zooniverse

Zooniverse — the renowned home of citizen science projects — is now one million strong. That’s one million registered volunteers since the project began less than seven years ago.

It all began when Galaxy Zoo launched in July 2007. The initial response to this project was overwhelming. Since then the Zooniverse team has created almost 30 citizen science projects ranging from astronomy to zoology.

“We are constantly amazed by the effort that the community puts into our projects,” said the Zooniverse team in an email regarding the news late last week.

Many projects have produced unique scientific results, ranging from individual discoveries to classifications that rely on input from thousands of volunteers. As of today there are 60+ papers listed on the websites publications page, many of which have made the news.

In the first two weeks after Galaxy Zoo’s launch, registered citizen scientists classified more than a million galaxies. Each volunteer was presented with an image from the Sloan Digital Sky Survey and asked to classifiy the galaxy as belonging to one of six categories: elliptical, clockwise spiral, anticlockwise spiral, edge-on, merger, or unsure.

An example of an unknown galaxy needing classification. Image credit: Galaxy Zoo
An example of an unknown galaxy needing classification. Image credit: Galaxy Zoo

But citizen scientists weren’t simply labeling galaxies, they were helping astronomers to answer crucial questions and raise new ones about our current understandings of galaxy evolution. One significant finding showed that bar-shaped features in spiral galaxies has doubled over the latter half of the history of the Universe. This confirms that bars signify maturity in spiral galaxies and play an important role in shutting down star formation.

Another finding downplayed the importance of collisions in forming supermassive black holes. Citizen scientists found 13 bulgeless galaxies — suggesting they had never experienced a major collision — with supermassive black holes, nonetheless. All healthy black holes, with masses at least millions of times that of the Sun, must have grown through less dramatic processes.

Planet Hunters — a citizen science project developed in 2010 — has also seen wide success. Ordinary citizens examine the Kepler Space Telescope’s light curves of stars and flag any slight dips in brightness that might indicate a planet crossing in front of the star. Many eyes examine each light curve, allowing some to cross check others.

An example light curve.
An example light curve asking for any obvious dips. Image Credit: Planet Hunters

In roughly three years, citizen scientists examined more than 19 million Kepler light curves. Contrary to what many astronomers expected, ordinary citizens were able to spot transiting objects that many computer algorithms missed.

In 2012, Planet Hunter volunteers, Kian Jek and Robert Gagliano discovered an exoplanet in a four-star system. The Neptune-size planet, labeled “Planet Hunters 1” (PH1), orbits its two parent stars every 138 days. A second pair of stars, approximately 90 billion miles away, are also gravitationally bound to the system. This wacky system was later confirmed by professional astronomers.

In 2013, Planet Hunter volunteers discovered yet another planet candidate, which, if confirmed, would make a known six-planet system really the first seven-planet system. The five innermost planets are smaller than Neptune, while the two outer planets are gas giants. All orbit within Earth’s orbit around the Sun.

These are only a few of Zooniverse’s citizen science projects. Others allow ordinary citizens to help analyze how whales communicate with one another, study the lives of the ancient Greeks, and even look at real life cancer data. So join today and become number one million and one.

Zooniverse is produced by the Citizen Science Alliance, which works with many academic and other partners worldwide.