Laniakea supercluster: Newly identified galactic supercluster, home to the Milky Way

A slice of the Laniakea Supercluster in the supergalactic equatorial plane, an imaginary plane containing many of the most massive clusters in this structure. 

The colours represent density within this slice, with red for high densities and blue for voids, areas with relatively little matter. 

Individual galaxies are shown as white dots. 

Velocity flow streams within the region gravitationally dominated by Laniakea are shown in white, while dark blue flow lines are away from the Laniakea local basin of attraction. 

The orange contour encloses the outer limits of these streams, a diameter of about 160 Mpc. This region contains the mass of about 100 million billion suns. 

Credit: SDvision interactive visualization software by DP at CEA/Saclay, France.

Astronomers using the National Science Foundation's Green Bank Telescope (GBT), among other telescopes, have determined that our own Milky Way galaxy is part of a newly identified ginormous supercluster of galaxies, which they have dubbed "Laniakea," which means "immense heaven" in Hawaiian.

This discovery clarifies the boundaries of our galactic neighbourhood and establishes previously unrecognized linkages among various galaxy clusters in the local Universe.

"We have finally established the contours that define the supercluster of galaxies we can call home," said lead researcher R. Brent Tully, an astronomer at the University of Hawaii at Manoa.

"This is not unlike finding out for the first time that your hometown is actually part of much larger country that borders other nations."

The paper explaining this work is the cover story of the September 4 issue of the journal Nature.

Superclusters are among the largest structures in the known Universe. They are made up of groups, like our own Local Group, that contain dozens of galaxies, and massive clusters that contain hundreds of galaxies, all interconnected in a web of filaments.

Though these structures are interconnected, they have poorly defined boundaries.

To better refine cosmic mapmaking, the researchers are proposing a new way to evaluate these large-scale galaxy structures by examining their impact on the motions of galaxies.

A galaxy between structures will be caught in a gravitational tug-of-war in which the balance of the gravitational forces from the surrounding large-scale structures determines the galaxy's motion.

By using the GBT and other radio telescopes to map the velocities of galaxies throughout our local Universe, the team was able to define the region of space where each supercluster dominates.

"Green Bank Telescope observations have played a significant role in the research leading to this new understanding of the limits and relationships among a number of superclusters," said Tully.


The Milky Way resides in the outskirts of one such supercluster, whose extent has for the first time been carefully mapped using these new techniques.

This so-called Laniakea Supercluster is 500 million light-years in diameter and contains the mass of one hundred million billion Suns spread across 100,000 galaxies.

This study also clarifies the role of the Great Attractor, a gravitational focal point in intergalactic space that influences the motion of our Local Group of galaxies and other galaxy clusters.

Two views of the Laniakea Supercluster. 

Credit: SDvision interactive visualization software by DP at CEA/Saclay, France

Within the boundaries of the Laniakea Supercluster, galaxy motions are directed inward, in the same way that water streams follow descending paths toward a valley.

The Great Attractor region is a large flat bottom gravitational valley with a sphere of attraction that extends across the Laniakea Supercluster.

The name Laniakea was suggested by Nawa'a Napoleon, an associate professor of Hawaiian Language and chair of the Department of Languages, Linguistics, and Literature at Kapiolani Community College, a part of the University of Hawaii system. The name honors Polynesian navigators who used knowledge of the heavens to voyage across the immensity of the Pacific Ocean.

More information: Nature, dx.doi.org/10.1038/nature13674

Arecibo observatory: Two New Programs Launching to Listen for Aliens

The 305-meter telescope at Arecibo Observatory is just one of a collection that SETI will use to search nearby stars for electronic signals that could indicate intelligent life. 

If such a civilization was utilizing a similar dish to image exoplanets, SETI's team should be able to detect it.

Credit: Arecibo Observatory

SETI is stepping up its search for alien lifeforms on far off worlds.

The Search for Extraterrestrial Intelligence (SETI) program recently announced two new methods to search for signals that could come from life on other planets.

In the Panchromatic SETI project, multiple telescopes will scan a variety of wavelengths from 30 stars near the sun; the project will look for powerful signals beamed into space, potentially by intelligent extraterrestrials.

SETI is also launching an interplanetary eavesdropping program that is expected to search for messages beamed between planets in a single system.

"If we are polluting space, perhaps other extraterrestrials are leaking signals," Dan Werthimer, director of the Berkley SETI Research Center, told an audience during the Smithsonian Magazine's "The Future is Here" Festival in May. "Maybe they're sending something our way."

'Everything we've got'
Since humans made their first FM radio and television transmissions, signals from Earth have been spilling out into space, announcing the presence of intelligent life to any group that might be searching for it.

According to Werthimer, signals from the 1950s television show "I Love Lucy" have reached thousands of stars, while the nearest suns have already enjoyed the "The Simpsons."

If Earth has unintentionally leaked signs of its presence, other alien civilizations may have done the same thing.

SETI's new Panchromatic project will utilize a variety of telescopes covering a range of frequencies to scour the nearest stars.

"We're going to throw everything we've got at it," Werthimer added.

The panchromatic project will examine a sample of the 30 stars that lie within 5 parsecs (16 light-years) from the sun. The list includes 13 single stars, seven binary systems and one triple system.

Most of the stars are smaller than the sun, but the project will also examine two white dwarfs and one moderately evolved F star. No confirmed exoplanets have been found around any of the stars.

By setting distance as the criteria, the SETI team hopes to alleviate any bias that might otherwise result from focusing on systems similar to that of Earth. The team selected stars for study based only on how far they lie from the sun.

According to SETI-Berkeley's Andrew Siemion, chief scientist of the eavesdropping project, the search will also probe a diverse stellar population already well studied at many wavelengths.

"In the event of a non-detection, these attributes of the sample will allow us to place strong and broadly applicable limits on the presence of technology," Siemion told Space.com via email.

Observations from the Low Frequency Array (LOFAR) telescope in Europe and the Green Bank Telescope (GBT) in West Virginia will begin over the summer and fall of 2014.

Instrument development and commissioning is still in progress for the Infrared Spatial Interferometer (ISI) at Mount Wilson Observatory and the Nickel Telescope at Lick Observatory, both in California.

But according to Siemion, the pair should be ready at about the same time. The Nickel Telescope will conduct the first-ever SETI observations done in the near-infrared.

Remarkable white dwarf star; coldest, dimmest ever detected

This is an artist impression of a white dwarf star in orbit with pulsar PSR J2222-0137. 

It may be the coolest and dimmest white dwarf ever identified. 

Credit: B. Saxton (NRAO /AUI /NSF)

A team of astronomers has identified possibly the coldest, faintest white dwarf star ever detected.

This ancient stellar remnant is so cool that its carbon has crystallized, forming an Earth-size diamond in space.

David Kaplan

"It's a really remarkable object," said David Kaplan, a professor at the University of Wisconsin-Milwaukee. "These things should be out there, but because they are so dim they are very hard to find."

Kaplan and his colleagues found this stellar gem using the National Radio Astronomy Observatory's (NRAO) Green Bank Telescope (GBT) and Very Long Baseline Array (VLBA), as well as other observatories.

White dwarfs are the extremely dense end-states of stars like our Sun that have collapsed to form an object approximately the size of the Earth.

Composed mostly of carbon and oxygen, white dwarfs slowly cool and fade over billions of years. The object in this new study is likely the same age as the Milky Way, approximately 11 billion years old.

Pulsars are rapidly spinning neutron stars, the superdense remains of massive stars that have exploded as supernovas.

As neutron stars spin, lighthouse-like beams of radio waves, streaming from the poles of its powerful magnetic field, sweep through space.

When one of these beams sweeps across the Earth, radio telescopes can capture the pulse of radio waves.

The pulsar companion to this white dwarf, dubbed PSR J2222-0137, was the first object in this system to be detected.

Jason Boyles

It was found using the GBT by Jason Boyles, then a graduate student at West Virginia University in Morgantown.

These first observations revealed that the pulsar was spinning more than 30 times each second and was gravitationally bound to a companion star, which was initially identified as either another neutron star or, more likely, an uncommonly cool white dwarf. The two were calculated to orbit each other once every 2.45 days.

The pulsar was then observed over a two-year period with the VLBA by Adam Deller, an astronomer at the Netherlands Institute for Radio Astronomy (ASTRON).

These observations pinpointed its location and distance from the Earth, approximately 900 light-years away in the direction of the constellation Aquarius.

This information was critical in refining the model used to time the arrival of the pulses at the Earth with the GBT.

By applying Einstein's theory of relatively, the researchers studied how the gravity of the companion warped space, causing delays in the radio signal as the pulsar passed behind it.

These delayed travel times helped the researchers determine the orientation of their orbit and the individual masses of the two stars.

The pulsar has a mass 1.2 times that of the Sun and the companion a mass 1.05 times that of the Sun.

These data strongly indicated that the pulsar companion could not have been a second neutron star; the orbits were too orderly for a second supernova to have taken place.

Knowing its location with such high precision and how bright a white dwarf should appear at that distance, the astronomers believed they should have been able to observe it in optical and infrared light.

Remarkably, neither the Southern Astrophysical Research (SOAR) telescope in Chile nor the 10-meter Keck telescope in Hawaii was able to detect it.

"Our final image should show us a companion 100 times fainter than any other white dwarf orbiting a neutron star and about 10 times fainter than any known white dwarf, but we don't see a thing," said Bart Dunlap, a graduate student at the University of North Carolina at Chapel Hill and one of the team members.

"If there's a white dwarf there, and there almost certainly is, it must be extremely cold."

The researchers calculated that the white dwarf would be no more than a comparatively cool 3,000 degrees Kelvin (2,700 degrees Celsius).

Astronomers believe that such a cool, collapsed star would be largely crystallized carbon, not unlike a diamond.

Other such stars have been identified and they are theoretically not that rare, but with a low intrinsic brightness, they can be deucedly difficult to detect.

Its fortuitous location in a binary system with a neutron star enabled the team to identify this one.

Green Bank Telescope (GBT): High Velocity Smith Cloud is a failed Dwarf Star

This is a false-colour image of the Smith Cloud made with data from the Green Bank Telescope (GBT). 

Credit: NRAO/AUI/NSF

Like a bullet wrapped in a full metal jacket, a high-velocity hydrogen cloud hurtling toward the Milky Way appears to be encased in a shell of dark matter, according to a new analysis of data from the National Science Foundation's Robert C. Byrd Green Bank Telescope (GBT).

Astronomers believe that without this protective shell, the high-velocity cloud (HVC) known as the Smith Cloud would have disintegrated long ago when it first collided with the disk of our Galaxy.

If confirmed by further observations, a halo of dark matter could mean that the Smith Cloud is actually a failed dwarf galaxy, an object that has all the right stuff to form a true galaxy, just not enough to produce stars.

"The Smith Cloud is really one of a kind. It's fast, quite extensive, and close enough to study in detail," said Matthew Nichols with the Sauverny Observatory in Switzerland and principal author on a paper accepted for publication in the Monthly Notices of the Royal Astronomical Society.

"It's also a bit of a mystery; an object like this simply shouldn't survive a trip through the Milky Way, but all the evidence points to the fact that it did."

Previous studies of the Smith Cloud revealed that it first passed through our Galaxy many millions of years ago.

By re-examining and carefully modeling the cloud, astronomers now believe that the Smith Cloud contains and is actually wrapped in a substantial "halo" of dark matter, the gravitationally significant yet invisible stuff that makes up roughly 80 percent of all the matter in the Universe.

"Based on the currently predicted orbit, we show that a dark matter free cloud would be unlikely to survive this disk crossing," observed Jay Lockman, an astronomer at the National Radio Astronomy Observatory in Green Bank, West Virginia, and one of the coauthors on the paper.

"While a cloud with dark matter easily survives the passage and produces an object that looks like the Smith Cloud today."

The Milky Way is swarmed by hundreds of high-velocity clouds, which are made up primarily of hydrogen gas that is too rarefied to form stars in any detectable amount.

The only way to observe these objects, therefore, is with exquisitely sensitive radio telescopes like the GBT, which can detect the faint emission of neutral hydrogen.

If it were visible with the naked eye, the Smith Cloud would cover almost as much sky as the constellation Orion.

Most high-velocity clouds share a common origin with the Milky Way, either as the leftover building blocks of galaxy formation or as clumps of material launched by supernovas in the disk of the Galaxy.

A rare few, however, are interlopers from farther off in space with their own distinct pedigree. A halo of dark matter would strengthen the case for the Smith Cloud being one of these rare exceptions.

Currently, the Smith Cloud is about 8,000 light-years away from the disk of our Galaxy. It is moving toward the Milky Way at more than 150 miles per second and is predicted to impact again in approximately 30 million years.

"If confirmed to have dark matter this would in effect be a failed galaxy," said Nichols. "Such a discovery would begin to show the lower limit of how small a galaxy could be."

The researchers believe this could also improve our understanding of the Milky Way's earliest star formation.

More information: Paper on Arxiv: arxiv.org/abs/1404.3209

Remarkable Features below the surface of the Moon

Mare Serenitatis / Sea of Serenity. 

Credit: Bruce Campbell (Smithsonian Institution, National Air and Space Museum); Arecibo /NAIC; NRAO /AUI /NSF

New images of Earth's Moon reveal more than can be seen with the naked eye, thanks to the combined efforts of the two largest radio telescopes of their kind, the National Radio Astronomy Observatory's Green Bank Telescope (GBT) in West Virginia and the Arecibo Observatory in Puerto Rico.

To make these images, radar signals beamed from Arecibo's powerful transmitter penetrated far below the Moon's dusty surface.

The signals then rebounded back and were picked up by the sensitive receivers on the GBT.

This observing technique, known as bistatic radar, has been used to study many objects in our solar system, including asteroids and other planets.

The first image reveals previously hidden features around an area known as Mare Serenitatis, or the Sea of Serenity, which is near the Apollo 17 landing site.

The radar observations were able to "see" approximately 10-15 meters (33-50 feet) below the lunar surface.

The light and dark features are the result of compositional changes in the lunar dust and differences in the abundance of rocks buried within the soil.

The second image is a similar observation of the lunar impact crater known as Aristillus.

The radar echoes reveal geologic features of the large debris field created by the force of the impact.

The dark "halo" surrounding the crater is due to pulverized debris beyond the rugged, radar-bright rim deposits.

The image also shows traces of lava-like features produced when lunar rock melted from the heat of the impact.

The crater is approximately 55 kilometers (34 miles) in diameter and 3.5 kilometers (2 miles) deep.

Aristillus Crater. 

Credit: Bruce Campbell (Smithsonian Institution, National Air and Space Museum); Arecibo/NAIC; NRAO/AUI/NSF

These images help planetary scientists interpret the complex history of the Moon, which is often obscured by dust layers built up over billions of years, better understand the geology of earlier landing sites, and plan for future lunar exploration.

Fireworks Galaxy: Rivers of Hydrogen Gas Fuel Spiral Galaxies

Three distinct features are visible in this composite image of NGC 6946. 

The bright heart of the galaxy in optical light (blue), the dense hydrogen in the spirals (orange), and the extended halo surrounding the galaxy (red). 

New research also shows a faint filament that could be hydrogen flowing from the intergalactic medium into the galaxy to fuel star formation.

Credit: D.J. Pisano (WVU); B. Saxton (NRAO/AUI/NSF); Palomar Observatory – Space Telescope Science Institute 2nd Digital Sky Survey (Caltech); Westerbork Synthesis Radio Telescope

Inpouring rivers of hydrogen gas could explain how spiral galaxies maintain the constant star formation that dominates their hearts, a new study reports.

Using the Green Bank Telescope (GBT) in West Virginia, scientists observed a tenuous filament of gas streaming into the galaxy NGC 6946, known as the "Fireworks Galaxy" because of the large number of supernovae observed within it.

The find may provide insight into the source of fuel that powers the ongoing birth of young stars, researchers said.

D.J. Pisano

"We knew that the fuel for star formation had to come from somewhere," study lead author D.J. Pisano, of West Virginia University (WVU), said in a statement.

"So far, however, we've detected only about 10 percent of what would be necessary to explain what we observe in many galaxies."

Located 22 million light-years from Earth on the border of the constellations Cepheus and Cygnus, NGC 6946 is a medium-sized spiral galaxy pointed face-on toward the Milky Way.

Previous studies revealed a halo of hydrogen gas around NGC 6946 common to spiral galaxies.

Such halos are formed by hydrogen ejected from the galaxies by star formation and violent supernova explosions.

These interactions heat the gas in the halo to extreme temperatures.

When Pisano turned the GBT toward the spiral galaxy for further examination, however, he discovered a ribbon of gas too cool to have suffered the heating processes undergone by the halo gas.

On average, the Milky Way churns out between 1 to 5 new stars per year. Rich in gas, NGC 6946 is far more active. For example, it has hosted at least 9 explosive supernovae in the past century.

"A leading theory is that rivers of hydrogen — known as cold flows — may be ferrying hydrogen through intergalactic space, clandestinely fueling star formation," Pisano said. "But this tenuous hydrogen has simply been too diffuse to detect, until now."

The immense, unblocked dish of the Green Bank Telescope (GBT), combined with its location in the US National Radio Quiet Zone, where radio transmissions are limited, allow the large disk to detect the faint hydrogen signal that would be present in a cold flow.

Another possibility is that the hydrogen detected originated from a close encounter with another galaxy in the past.

The gravitational interaction between the two could have stretched out a ribbon of neutral atomic hydrogen, researchers said.

Such a ribbon would contain stars that astronomers should be able to easily observe, though none have yet been spotted. Further studies of the streamer hydrogen gas will help clarify its role.

The research was published in the Astronomical Journal.

Green Bank Telescope (GBT): River of Hydrogen flowing through space

This composite image contains three distinct features: the bright star-filled central region of galaxy NGC 6946 in optical light (blue), the dense hydrogen tracing out the galaxy's sweeping spiral arms and galactic halo (orange), and the extremely diffuse and extended field of hydrogen engulfing NGC 6946 and its companions (red). 

The new GBT data show the faintly glowing hydrogen bridging the gulf between the larger galaxy and its smaller companions. 

This faint structure is precisely what astronomers expect to appear as hydrogen flows from the intergalactic medium into galaxies or from a past encounter between galaxies. 

Credit: D.J. Pisano (WVU); B. Saxton (NRAO/AUI/NSF); Palomar Observatory -- Space Telescope Science Institute 2nd Digital Sky Survey (Caltech); Westerbork Synthesis Radio Telescope (WSRT)

D.J. Pisano

Using the National Science Foundation's Robert C. Byrd Green Bank Telescope (GBT), astronomer D.J. Pisano from West Virginia University has discovered what could be a never-before-seen river of hydrogen flowing through space.

This very faint, very tenuous filament of gas is streaming into the nearby galaxy NGC 6946 and may help explain how certain spiral galaxies keep up their steady pace of star formation.

"We knew that the fuel for star formation had to come from somewhere. So far, however, we've detected only about 10 percent of what would be necessary to explain what we observe in many galaxies," said Pisano.

"A leading theory is that rivers of hydrogen – known as cold flows – may be ferrying hydrogen through intergalactic space, clandestinely fueling star formation. But this tenuous hydrogen has been simply too diffuse to detect, until now."

Spiral galaxy NGC 6946

Spiral galaxies, like our own Milky Way, typically maintain a rather tranquil but steady pace of star formation.

Others, like NGC 6946, which is located approximately 22 million light-years from Earth on the border of the constellations Cepheus and Cygnus, are much more active, though less-so than more extreme starburst galaxies.

This raises the question of what is fueling the sustained star formation in this and similar spiral galaxies.

Earlier studies of the galactic neighborhood around NGC 6946 with the Westerbork Synthesis Radio Telescope (WSRT) in the Netherlands have revealed an extended halo of hydrogen (a feature commonly seen in spiral galaxies, which may be formed by hydrogen ejected from the disk of the galaxy by intense star formation and supernova explosions).

A cold flow, however, would be hydrogen from a completely different source: gas from intergalactic space that has never been heated to extreme temperatures by a galaxy's star birth or supernova processes.

Using the GBT, Pisano was able to detect the glow emitted by neutral hydrogen gas connecting NGC 6946 with its cosmic neighbours. This signal was simply below the detection threshold of other telescopes.

The GBT's unique capabilities, including its immense single dish, unblocked aperture, and location in the National Radio Quiet Zone, enabled it to detect this tenuous radio light.

Astronomers have long theorized that larger galaxies could receive a constant influx of cold hydrogen by syphoning it off other less-massive companions.

In looking at NGC 6946, the GBT detected just the sort of filamentary structure that would be present in a cold flow, though there is another probable explanation for what has been observed.

It's also possible that sometime in the past this galaxy had a close encounter and passed by its neighbours, leaving a ribbon of neutral atomic hydrogen in its wake.

If that were the case, however, there should be a small but observable population of stars in the filaments.

Further studies will help to confirm the nature of this observation and could shine light on the possible role that cold flows play in the evolution of galaxies.

Journal Reference: D. J. Pisano. GREEN BANK TELESCOPE OBSERVATIONS OF LOW COLUMN DENSITY H I AROUND NGC 2997 AND NGC 6946. The Astronomical Journal, 2014; 147 (3): 48 DOI: 10.1088/0004-6256/147/3/48