Astronomy Archives

March 17, 2014April 26, 2016 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) 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.

March 17, 2014December 23, 2015 by Bob King

Till Hellas Freezes Over – See Frost and Clouds in Mars’ Largest Crater

Mars photographed during part of its rotation from Melbourne, Australia on March 8. The bright "cap" marks Hellas, now covered in wintertime frost and clouds. Credit: Maurice Valimberti

Earth’s changing weather always makes life interesting. Seeing weather on other planets through a telescope we sense a kinship between our own volatile world and the fluttering image in the eyepiece. With the April 8 opposition of Mars rapidly approaching, you won’t want to miss a striking meteorological happening right now on the Red Planet.

Map showing the most prominent dark features on Mars. Hellas is at upper right. To its north is the Africa-shaped windswept volcanic plain Syrtis Major. Credit: A.L.P.O. — Map showing the most prominent dark features on Mars. Hellas is at upper right. Credit: A.L.P.O.

Winter’s already well underway in the planet’s southern hemisphere and there’s no better place to see it than over Hellas, Mars’ biggest impact crater. Hellas formed some 4 billion years when a small asteroid crashed into the young planet and left a scar measuring 1,400 miles (2,300 km) wide and 26,465 feet (7,152 meters) deep. Point your telescope in its direction in the next few weeks and you’ll see what looks at first like the planet’s south polar cap. Don’t be deceived. That’s Hellas coated in dry ice frost and filled with wintertime clouds.

The Hellas impact basin, also known as Hellas Planitia. After Mars' Utopia Planitia and the moon's South Pole-Aitken Basin, Hellas is the third largest confirmed crater in the solar system. — The Hellas impact basin, also known as Hellas Planitia, is 1,400 miles wide. After Mars’ Utopia Planitia and the moon’s South Pole-Aitken Basin, Hellas is the third largest confirmed crater in the solar system.

Right now, Mars’ northern hemisphere, along with the north polar cap, are tipped our way. Though the cap is rapidly vaporizing as the northern summer progresses, you can still spot it this month as a small dab of white along the northern limb in 6-inch (15 cm) and larger telescopes. Use a magnification upwards of 150x for the best views. The south polar cap can’t be seen because it’s tipped beyond the southern limb.

Mars from Athens, Greece on March 14, 2014 with Hellas (top), Syrtis Major and both morning and evening limb water clouds. Credit: Manos Kardasis — Mars from Athens, Greece on March 14, 2014 with Hellas (top), Syrtis Major and both morning and evening limb water clouds. The winter-whitened Hellas impact basin is best seen using magnifications of 150x or higher. Credit: Manos Kardasis

Along with nearby Syrtis Major, Hellas was one of the first features discovered with the telescope. Even in summer its pale floor stands out against the darker volcanic features of the planet. Though windswept and bitter cold now, Hellas’ great depth makes it one of the warmest places on Mars during the summer months. Mid-summer atmospheric pressure has been measured at more than 10 millibars, more than twice the planet’s mean. Afternoon high temperatures reach near the freezing point (32 F / 0 C) with nighttime lows around -50 F (-45 C). Winter temperatures are much more severe with lows around -22o F (-140 C). Carbon dioxide condenses as frost and whitens the floors of many craters during this time.

Mars photographed by the Mars Global Surveyor shows the equally prominent Syrtis Major and the Hellas impact basin. Credit; NASA/JPL/Malin Space Systems — Mars photographed by the Mars Global Surveyor shows the equally prominent Syrtis Major and the Hellas impact basin. Syrtis Major is an ancient, low relief shield volcano. Credit; NASA/JPL/Malin Space Systems

We can only see Hellas when that hemisphere is turned in our direction; this happens for about a week and a half approximately once a month. European observers are favored this week with Hellas well placed near the planet’s central meridian from 1 – 4 a.m. local time. Why the outrageous hour? Mars rises around 10 p.m. but typically looks soft and mushy in the telescope until it’s high enough to clear the worst of atmospheric turbulence 2 – 3 hours later. North and South American observers will get their turn starting this Saturday March 22nd around 12:30 – 1 a.m. Good Hellas viewing continues through early April.

Mars at 1 a.m. CDT on successive nights starting March 21, 2014. Notice how planetary features appear to rotate to the east night to night. Created with images from Meridian — Mars at 1 a.m. CDT on successive nights starting March 21, 2014. Notice how planetary features appear to rotate slowly eastward night to night. Created with images from Meridian

Like Earth, Mars revolves from west to east on its axis, but because it rotation period is 37 minutes longer than Earth’s, Hellas and all Martian features appear to drift slowly eastward with each succeeding night. A feature you observed face-on at midnight one night will require staying up until 2:30 a.m. a week later for Mars to “rotate it back” to the same spot. To keep track of the best times to look for Hellas or anything else on Mars, I highly recommend the simple, free utility called Meridian created by Claude Duplessis. Set your time zone and you’ll know exactly the best time to look.

Mars on March 8, 2014 shows not only clouds over Hellas but evening limb clouds. Credit: W.L. Chin — Mars on March 8, 2014 shows clouds over Hellas and evening limb clouds. Credit: Chin Wei Loon

While you’re out watching the Martian winter at work, don’t forget to also look for the shrinking north polar cap and bright, patchy clouds along the planet’s morning (east) and evening limbs. You can use the map above to try and identify the many subtle, gray-toned features named after lands in classic antiquity by 19th century Italian astronomer and Mars aficionado Giovanni Schiaparelli.

I will you success in seeing Hellas and encourage you to share your observations with us here at Universe Today.

March 17, 2014December 23, 2015 by Elizabeth Howell

Hubble Captures Starbirth In A Monkey’s Head As Telescope Approaches 24 Years In Space

A 2014 image of NGC 2174 by the Hubble Space Telescope. Credit: NASA/ESA and the Hubble Heritage Team (STScI/AURA)

Billowing gas clouds and young stars feature in this February Hubble Space Telescope image, released as the telescope approaches its 24th birthday this coming April. The telescope has seen a lot of drama over the years, but in this case, thankfully the excitement is taking place 6,400 light-years away. Here you can see starbirth in action in the nebula NGC 2174, which is sometimes called the Monkey Head Nebula.

“This region is filled with young stars embedded within bright wisps of cosmic gas and dust. Dark dust clouds billow outwards, framed against a background of bright blue gas. These striking hues were formed by combining several Hubble images taken through different coloured filters, revealing a broad range of colours not normally visible to our eyes,” the European Space Agency wrote.

“These vivid clouds are actually a violent stellar nursery packed with the ingredients needed for building stars. The recipe for cooking up new stars is quite inefficient, and most of the ingredients are wasted as the cloud of gas and dust disperses. This process is accelerated by the presence of fiercely hot young stars, which triggers high-speed winds that help to blow the gas outwards.”

Hubble’s dramatic history includes a deformed mirror, a rescue mission, and a nearly last-minute decision to do a shuttle flight for repairs and upgrades when the shuttle program was wrapping up. You can read more about Hubble’s colorful history at the Space Telescope Science Institute.

And Hubble has captured this nebula before, as you can see in this 2011 release.

Sources: ESA and Space Telescope Science Institute

March 16, 2014December 23, 2015 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

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.

March 15, 2014December 23, 2015 by Bob King

New Comet Jacques May Pass 8.4 million miles from Venus this July

Comet C/2014 E2 Jacques photographed from Siding Spring Observatory on March 14, 2014. Credit: Rolando Ligustri

Congratulations to Cristovao Jacques and the SONEAR team! On March 13 they snared C/2014 E2 (Jacques) in CCD images taken with a 0.45-meter (17.7-inch) wide-field reflector at the SONEAR (Southern Observatory for Near Earth Asteroids Research) observatory near Oliveira, Brazil. A very preliminary orbit indicates its closest approach to the sun will occur on June 29 at a distance of 56 million miles followed two weeks later by a relatively close flyby of Venus of 0.09 a.u. or 8.4 million miles (13.5 million km). If a comet approached Earth this closely so soon after perihelion, it would be a magnificent sight. Of course, watching from Venus isn’t recommended. Even if we could withstand its extreme heat and pressure cooker atmosphere, the planet’s perpetual cloud cover guarantees overcast skies 24/7.

Comet Jacques travels across the deep southern sky in early spring as seen from mid-northern latitudes. Approximate positions are shown through April 4. Stellarium

It’s the team’s second comet discovery this year after turning up C/2014 A4 (SONEAR) in January. Comet Jacques has been tracking across northern Centaurus since discovery. Over the next few nights, it straddles the border with Hydra where it will be visible low in the southern sky around for northern hemisphere observers from about midnight to 2 a.m. If you live on a Caribbean island and points south your view will be even better.

Steven Tilley’s animation of Comet C/2014 E2 Jacques over 35 minutes on March 13, 2014

Comet Jacques exhibits a dense, fairly bright 2-arc-minute coma or cometary atmosphere with a short northward-pointing tail. Brightness estimates have been hard to come by, but it appears the comet may be around magnitude +11.5 – 12 or within range of an 8-inch (20-cm) or larger telescope. One thing’s for certain. In the coming weeks, E2 will be approaching both the Earth and the sun and brightening as it slowly gains altitude in the evening sky.

Another view of the comet on March 13 through a 0.5-meter (19.5-inch) telescope. Credit: Ernesto Guido, Nick Howes, Martino Nicolini

Shortly after perihelion, Comet Jacques will shine brightest at around magnitude +10-10.5 (though it could be brighter) and remain nearly this bright as it swings north from Orion into Perseus from mid-July to mid- August. Closest approach to Earth occurs on Aug. 29-30 at 54 million miles (87 million km). It will join Comet Oukameiden – predicted to reach binocular visibility in late August – to offer comet lovers much to look forward to as the summer wanes.

March 13, 2014April 26, 2016 by David Dickinson

“Death Stars” Caught Blasting Proto-Planets

It’s a tough old universe out there. A young star has lots to worry about, as massive stars just beginning to shine can fill a stellar nursery with a gale of solar wind.

No, it’s not a B-movie flick: the “Death Stars of Orion” are real. Such monsters come in the form of young, O-type stars.

And now, for the first time, a team of astronomers from Canada and the United States have caught such stars in the act. The study, published in this month’s edition of The Astrophysical Journal, focused on known protoplanetary disks discovered by the Hubble Space Telescope in the Orion Nebula.

These protoplanetary disks, also known as “tadpoles” or proplyds, are cocoons of dust and gas hosting stars just beginning to shine. Much of this leftover material will go on to aggregate into planets, but nearby massive O-Type stars can cause chaos in a stellar nursery, often disrupting the process.

“O-Type stars, which are really monsters compared to our Sun, emit tremendous amounts of ultraviolet radiation and this can play havoc during the development of young planetary systems,” said astronomer Rita Mann in a recent press release. Mann works for the National Research Council of Canada in Victoria and is lead researcher on the project

Scientists used the Atacama Large Millimeter Array (ALMA) to probe the proplyds of Orion in unprecedented detail. Supporting observations were also made using the Submillimeter Array in Hawaii.

ALMA saw “first light” in 2011, and has already achieved some first rate results.

“ALMA is the world’s most sensitive telescope at high-frequency radio waves (e.g., 100-1000 GHz). Even with only a fraction of its final number of antennas, (with 22 operational out of a total planned 50) we were able to detect with ALMA the disks relatively close to the O-star while previous observatories were unable to spot them,” James Di Francesco of the National Research Council of Canada told Universe Today. “Since the brightness of a disk at these frequencies is proportional to its mass, these detections meant we could measure the masses of the disks and see for sure that they were abnormally low close to the O-type star.”

ALMA also doubled the number of proplyds seen in the region, and was also able to peer within these cocoons and take direct mass measurements. This revealed mass being stripped away by the ultraviolet wind from the suspect O-type stars. Hubble had been witness to such stripping action previous, but ALMA was able to measure the mass within the disks directly for the first time.

And what was discovered doesn’t bode well for planetary formation. Such protostars within about 0.1 light-years of an O-type star are consigned to have their cocoon of gas and dust stripped clean in just a few million years, just a blink of a eye in the game of planetary formation.

With a O-type star’s “burn brightly and die young” credo, this type of event may be fairly typical in nebulae during early star formation.

“O-type stars have relatively short lifespan, say around 1 million years for the brightest O-star in Orion – which is 40 times the mass of our Sun – compared to the 10 billion year lifespan of less massive stars like our Sun,” Di Francesco told Universe Today. “Since these clusters are typically the only places where O-stars form, I’d say that this type of event is indeed typical in nebulae hosting early star formation.”

It’s common for new-born stars to be within close proximity of each other in such stellar nurseries as M42. Researchers in the study found that any proplyds within the extreme-UV envelope of a massive star would have its disk shredded in short order, retaining on average less than 50% the mass of Jupiter total. Beyond the 0.1 light year “kill radius,” however, the chances for these proplyds to retain mass goes up, with researchers observing anywhere from 1 to 80 Jupiter masses of material remaining.

The findings in this study are also crucial in understanding what the early lives of stars are like, and perhaps the pedigree of our own solar system, as well as how common – or rare – our own history might be in the story of the universe.

There’s evidence that our solar system may have been witness to one or more nearby supernovae early in its life, as evidenced by isotopic measurements. We were somewhat lucky to have had such nearby events to “salt” our environment with heavy elements, but not sweep us clean altogether.

“Our own Sun likely formed in a clustered environment similar to that of Orion, so it’s a good thing we didn’t form too close to the O-stars in its parent nebula,” Di Francesco told Universe Today. “When the Sun was very young, it was close enough to a high-mass star so that when it blew up (went supernova) the proto-solar system was seeded with certain isotopes like Al-26 that are only produced in supernova events.”

This is the eventual fate of massive O-type stars in the Orion Nebula, though none of them are old enough yet to explode in this fashion. Indeed, it’s amazing to think that peering into the Orion Nebula, we’re witnessing a drama similar to what gave birth to our Sun and solar system, billions of years ago.

The Orion Nebula is the closest active star forming region to us at about 1,500 light years distant and is just visible to the naked eye as a fuzzy patch in the pommel of the “sword” of Orion the Hunter. Looking at the Orion Nebula at low power through a small telescope, you can just make out a group of four stars known collectively as the Trapezium. These are just such massive hot and luminous O-Type stars, clearing out their local neighborhoods and lighting up the interior of the nebula like a Chinese lantern.

And thus science fact imitates fiction in an ironic twist, as it turns out that “Death Stars” do indeed blast planets – or at least protoplanetary disks – on occasion!

Be sure to check out a great piece on ALMA on a recent episode of CBS 60 Minutes:

Read the abstract and the full (paywalled) paper on ALMA Observations of the Orion Proplyds in The Astrophysical Journal.

March 13, 2014December 23, 2015 by Elizabeth Howell

How Giant Galaxies Bind The Milky Way’s Neighborhood With Gravity

Artist's conception of the Milky Way galaxy. Credit: Nick Risinger

Is it stretching it too far to think of a Lord of the Rings-esque “Entmoot” when reading the phrase “Council of Giants”? In this case, however, it’s not trees gathering in a circle, but galaxies.

A new map of the galactic neighborhood shows how the Milky Way may be restricted by a bunch of galaxies surrounding and constricting us with gravity.

“All bright galaxies within 20 million light years, including us, are organized in a ‘Local Sheet’ 34-million light years across and only 1.5 million light years thick,” stated Marshall McCall of York University in Canada, who is the sole author of a paper on the subject.

“The Milky Way and Andromeda are encircled by twelve large galaxies arranged in a ring about 24-million light years across. This ‘Council of Giants’ stands in gravitational judgment of the Local Group by restricting its range of influence.”

The "Council of Giants" is shown in this diagram based on 2014 research from York University. It shows the brightest galaxies within 20 million light-years of the Milky Way. The galaxies in yellow are the "Council." (You can see a larger image if you click on this.) Credit: Marshall McCall / York University. — The “Council of Giants” is shown in this diagram based on 2014 research from York University. It shows the brightest galaxies within 20 million light-years of the Milky Way. The galaxies in yellow are the “Council.” (You can see a larger image if you click on this.) Credit: Marshall McCall / York University.

Here’s why McCall thinks this is the case. Most of the Local Sheet galaxies (the Milky Way, Andromeda, and 10 more of the 14 galaxies) are flattened spiral galaxies with stars still forming. The other other two galaxies are elliptical galaxies where star-forming ceased long ago, and of note, this pair lie on opposite sides of the “Council.”

“Winds expelled in the earliest phases of their development might have shepherded gas towards the Local Group, thereby helping to build the disks of the Milky Way and Andromeda,” the Royal Astronomical Society stated. The spin in this group of galaxies, it added, is unusually aligned, which could have occurred due to the influence of the Milky Way and Andromeda “when the universe was smaller.”

The larger implication is the Local Sheet and Council likely came to be in “a pre-existing sheet-like foundation composed primarily of dark matter”, or a mysterious substance that is not measurable by conventional instruments but detectable on how it influences other objects. McCall stated that on a small scale, this could help us understand more about how the universe is constructed.

You can read the study in the Monthly Notices of the Royal Astronomical Society.

Source: Royal Astronomical Society

March 13, 2014December 23, 2015 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.

March 12, 2014December 23, 2015 by Elizabeth Howell

Still No Sign Of ‘Planet X’ In Latest NASA Survey

No "Planet X" was found in a survey of the sky using NASA's Wide-Field Infrared Survey Explorer. This picture, which comes from the same dataset, shows a recently discovered star (in red) called WISEA J204027.30+695924.1. Credit: DSS/NASA/JPL-Caltech

It’s one of those rumors that just won’t quiet down — a large planet lurking at the solar system’s edge. Back in the 1840s, when Neptune was discovered, its orbit seemed to be a little “off” from what was expected.

Some astronomers of the time said that was caused by a planet further out. Although the Neptune perturbations are now ascribed to observational errors, the tale of Planet X continues, and has sometimes even been linked with doomsday. (See this past Universe Today story for the full tale.)

NASA’s latest survey puts even less credence in that theory. A scan of the sky showed nothing Saturn’s size or bigger at a distance of 10,000 Earth-sun distances, or astronomical units. Nothing bigger than Jupiter exists as far as 26,000 AU. (To put that in perspective, Pluto is 40 AU from the sun.)

“The outer solar system probably does not contain a large gas giant planet, or a small, companion star,” stated Kevin Luhman of the Center for Exoplanets and Habitable Worlds at Penn State University, author of a paper in the Astrophysical Journal describing the results.

Astronomers used information from NASA’s Wide-Field Infrared Survey Explorer, which did two full-sky scans in 2010 and 2011 to look at asteroids, stars and galaxies. NASA’s AllWISE program, released in November 2013, allows astronomers to find moving objects by comparing the two surveys.

Kevin Luhman discovered the brown dwarf pair in data from NASA's Wide-field Infrared Survey Explorer (WISE; artist's impression). Image: NASA/JPL-Caltech — Artist’s impression of the WISE satellite

A second study of the data found other objects further out in space — 3,525 stars and brown dwarfs (objects just below the threshold for fusion) within 500 light-years of the sun.

“We’re finding objects that were totally overlooked before,” stated Davy Kirkpatrick of NASA’s Infrared and Processing Analysis Center at the California Institute of Technology, who led the second paper.

Both papers will be published in the Astrophysical Journal.

Source: NASA

March 12, 2014December 23, 2015 by David Dickinson

Astronomers Identify the Largest Yellow “Hypergiant” Star Known

A stellar monster lurks in heart of the Centaur.

A recent analysis of a star in the south hemisphere constellation of Centaurus has highlighted the role that amateurs play in assisting with professional discoveries in astronomy.

The find used of the European Southern Observatory’s Very Large Telescope based in the Atacama Desert in northern Chile — as well as data from observatories around the world — to reveal the nature of a massive yellow “hypergiant” star as one of the largest stars known.

The stats for the star are impressive indeed: dubbed HR 5171 A, the binary system weighs in at a combined 39 solar masses, has a radius of over 1,300 times that of our Sun, and is a million times as luminous. Located 3,600 parsecs or over 11,700 light years distant, the star is 50% larger than the famous red giant Betelgeuse. Plop HR 5171 A down into the center of our own solar system, and it would extend out over 6 astronomical units (A.U.s) past the orbit of Jupiter.

The field around HR 5171 A (the brightest star just below center). Credit: ESO/Digitized Sky Survey 2.

Researchers used observations going back over 60 years – some of which were collected by dedicated amateur astronomers – to pin down the nature of this curious star. A variable star just below naked eye visibility spanning a magnitude range from +6.1 to +7.3, HR 5171 A also has a relatively small companion star orbiting across our line of sight once every 1300 days. Such a system is known as an eclipsing binary. Famous examples of similar systems are the star Algol (Alpha Persei), Epsilon Aurigae and Beta Lyrae. The companion star for HR 5171 is also a large star in its own right at around six solar masses and 400 solar radii in size. The distance from center-to-center for the system is about 10 A.U.s – the distance from Sol to Saturn – and the surface-to-surface distance for the A and B components of the system are “only” about 2.8 A.U.s apart. This all means that these two massive stars are in physical contact, with the expanded outer atmosphere of the bloated primary contacting the secondary, giving the pair a distorted peanut shape.

“The companion we have found is very significant as it can have an influence on the fate of HR 5171 A, for example stripping off its outer layers and modifying its evolution,” said astronomer Olivier Chesneau of the Observatoire de la Côte d’Azur in Nice France in the recent press release.

Knowing the orbital period of a secondary star offers a method to measure the mass of the primary using good old Newtonian mechanics. Coupled with astrometry used to measure its tiny parallax, this allows astronomers to pin down HR 5171 A’s stupendous size and distance.

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Along with luminous blue variables, yellow hypergiants are some of the brightest stars known, with an absolute magnitude of around -9. That’s just 16x times fainter than the apparent visual magnitude of a Full Moon but over 100 times brighter than Venus – if you placed a star like HR 5171 A 32 light years from the Earth, it would easily cast a shadow.

Astronomers used a technique known as interferormetry to study HR 5171 A, which involves linking up several telescopes to create the resolving power of one huge telescope. Researchers also culled through over a decade’s worth data to analyze the star. Though much of what had been collected by the American Association of Variable Star Observers (the AAVSO) had been considered to be too noisy for the purposes of this study, a dataset built from 2000 to 2013 by amateur astronomer Sebastian Otero was of excellent quality and provided a good verification for the VLT data.

The discovery is also crucial as researchers have come to realize that we’re catching HR 5171 A at an exceptional phase in its life. The star has been getting larger and cooling as it grows, and this change can be seen just over the past 40 year span of observations, a rarity in stellar astronomy.

“It’s not a surprise that yellow hypergiants are very instable and lose a lot of mass,” Chesneau told Universe Today. “But the discovery of a companion around such a bright star was a big surprise since any ‘normal’ star should at least be 10,000 times fainter than the hypergiant. Moreover, the hypergiant was much bigger than expected. What we see is not the companion itself, but the regions gravitationally controlled and filled by the wind from the hypergiant. This is a perfect example of the so-called Roche model. This is the first time that such a useful and important model has really been imaged. This hypergiant exemplifies a famous concept!”

Indeed, you can see just such photometric variations as the secondary orbits its host in the VLTI data collected by the AMBER interferometer, backed up by observations from GEMINI’s NICI chronograph:

Credit: ESO/VLT/GEMINI/NICI — Looking at the bizarre system of HR 5171. Credit: Olivier Chesneau/ESO/VLT/GEMINI/NICI

The NIGHTFALL program was also used for modeling the eclipsing binary components.

These latest measurements place HR 5171 A firmly in the “Top 10” for largest stars in terms of size known, as well as the largest yellow hypergiant star known This is due mainly to tidal interactions with its companion. Only eight yellow hypergiants have been identified in our Milky Way galaxy. HR 5171 A is also in a crucial transition phase from a red hypergiant to becoming a luminous blue variable or perhaps even a Wolf-Rayet type star, and will eventually end its life as a supernova.

Enormous stars: From left to right, The Pistol Star, Rho Cassiopeiae, Betelgeuse and VY Canis Majoris compared with the orbits of Jupiter (in red) and Neptune (in blue). Remember, HR 5171 A is 50% larger than Betelgeuse! Credit: Anynobody under a Creative Commons Attribution Share-Alike 3.0 Unported license.

HR 5171 A is also known as HD 119796, HIP 67261, and V766 Centauri. Located at Right Ascension 13 Hours 47’ 11” and declination -62 degrees 35’ 23,” HR 5171 culminates just two degrees above the southern horizon at local midnight as seen from Miami in late March.

HR 5171 A: a finder chart. Click to enlarge. Credit: Stellarium

HR 5171 A is a fine binocular object for southern hemisphere observers.

But the good news is, there’s another yellow hypergiant visible for northern hemisphere observers named Rho Cassiopeiae:

Rho Cass is one of the few naked eye examples of a yellow hypergiant star, and varies from magnitude +4.1 to +6.2 over an irregular period.

It’s amusing read the Burnham’s Celestial Handbook entry on Rho Cass. He notes the lack of parallax and the spectral measurements of the day — the early 1960s — as eluding to a massive star with a “true distance… close to 3,000 light years!” Today we know that Rho Cassiopeiae actually lies farther still, at over 8,000 light years distant. Robert Burnham would’ve been impressed even more by the amazing nature of HR 5171 as revealed today by ESO astronomers!

– The AAVSO is always seeking observations from amateur astronomers of variable stars.