Posted on by Nancy Atkinson

Dark Galaxies Found from the Early Universe

Caption: This deep image shows the region of the sky around the quasar HE0109-3518, near the center of the image. The energetic radiation of the quasar makes dark galaxies glow, helping astronomers to understand the obscure early stages of galaxy formation. Credit:ESO, Digitized Sky Survey 2 and S. Cantalupo (UCSC)


How do you find a dark galaxy? Shine some light on the subject. Dark galaxies — ancient galaxies that contain little to no stars — have been theorized to exist but have not been observed, until now. An international team of astronomers think they have detected these elusive objects by observing them glowing as they are illuminated by a quasar.

Dark galaxies are small, gas-rich galaxies in the early Universe that are very inefficient at forming stars. They are predicted by theories of galaxy formation and are thought to be the building blocks of today’s bright, star-filled galaxies. Astronomers think that they may have fed large galaxies with much of the gas that later formed into the stars that exist today.

Being essentially devoid of stars, these dark galaxies don’t emit much light, making them very hard to detect. For years astronomers have been trying to develop new techniques that could confirm the existence of these galaxies. Small absorption dips in the spectra of background sources of light have hinted at their existence. However, this new study marks the first time that such objects have been seen directly.

“Our approach to the problem of detecting a dark galaxy was simply to shine a bright light on it,” said Simon Lilly, from the Institute for Astronomy at ETH Zurich, Switzerland) co-author of a new paper published in the Monthly Notices of the Royal Astronomical Society. “We searched for the fluorescent glow of the gas in dark galaxies when they are illuminated by the ultraviolet light from a nearby and very bright quasar. The light from the quasar makes the dark galaxies light up in a process similar to how white clothes are illuminated by ultraviolet lamps in a night club.”

Fluorescence is the emission of light by a substance illuminated by a light source. Quasars are very bright, distant galaxies, and their brightness makes them powerful beacons that can help to illuminate the surrounding area, probing the era when the first stars and galaxies were forming out of primordial gas.

This video zooms into the region around the quasar, HE 0109-3518:

In order to detect the extremely faint fluorescent glow of these dark galaxies, the team used the Very Large Telescope (VLT), and took a series of very long exposures, mapping a region of the sky around the bright quasar HE 0109-3518. They looked for the ultraviolet light that is emitted by hydrogen gas when it is subjected to intense radiation.

The team detected almost 100 gaseous objects lying within a few million light-years of the quasar, and narrowed the possible dark galaxies down to 12 objects. The team says these are the most convincing identifications of dark galaxies in the early Universe to date.

“Our observations with the VLT have provided evidence for the existence of compact and isolated dark clouds,” said Sebastiano Cantalupo from the University of California, Santa Cruz, lead author of the paper. “With this study, we’ve made a crucial step towards revealing and understanding the obscure early stages of galaxy formation and how galaxies acquired their gas.”

The astronomers were also able to determine some of the properties of the dark galaxies, and estimate that the mass of the gas in them is about 1 billion times that of the Sun, typical for gas-rich, low-mass galaxies in the early Universe. They were also able to estimate that the star formation efficiency is suppressed by a factor of more than 100 relative to typical star-forming galaxies found at similar stage in cosmic history.

Read the team’s paper.

Source: ESO

Posted on by John Williams

Life and Death in a Tangled Web of Space

The Vela-C molecular cloud region as observed in far-infrared wavelengths. Credit: CNRS/INSU - Univ. Paris Diderot, France

In a star-making nebula awash in a tangled nest of gas and glowing filaments, scientists have uncovered an interesting, previously unseen interplay between gravity and turbulence that affects the formation of stars.

This image, taken by the European Space Agency’s Herschel Space Observatory, shows the highly detailed structure of cool wispy filaments of the Vela C molecular cloud. Located just 2,300 light-years from Earth, Vela-C is a vast star-making complex of gas and dust. And within this glowing cloud, both high-mass stars and smaller Sun-like stars form through very different processes.

Gravitational attraction pulls gas and dust together to form massive clumps of matter in glowing ridges. According to scientists studying the image, the most massive and brightest stars will form within these clumps. Random motion and turbulence throughout the cloud appear to create the fine nest-like filaments. It’s within these areas that smaller stars will form. Tiny, white specks fleck the image. These white dots, more abundant in the ridge-like filaments, are pre-stellar cores; compact clumps of gas and dust that might ignite into new stars.

Vela-C’s proximity to Earth makes it an ideal laboratory to study the birth of different kinds of stars. The nebula may also make it a perfect study of supernovae. The blue areas in the image contain expanding pockets of hot gas energized by the strong solar wind and ultraviolet radiation of young and massive stars. Compared to our Sun’s expected 10 billion year life-span, these massive stars burn through their supply of nuclear fuel within just a few million years. At the end of their lives, these stars will explode in dazzling supernovae.

The Herschel Telescope, launched in 2009, explores the Universe in the far infrared. While interstellar dust is cold, it shines brightly against the even colder surrounding space. The longest wavelengths of light show up as the red filaments in this image. Shorter, signifying hotter, wavelengths of light show up as yellow, green and blue.

Image Caption: The Vela-C molecular cloud region observed in far-infrared wavelengths. Credit: ESA/PACS/SPIRE/Tracey Hill & Frédérique Motte, Laboratoire AIM Paris-Saclay, CEA/Irfu – CNRS/INSU – Univ. Paris Diderot, France

Posted on by John Williams

Galactic Gong – Milky Way Struck and Still Ringing After 100 Million Years

Small Magellanic Cloud
Small Magellanic Cloud

When galaxies collide, stars are thrown from orbits, spiral arms are stretched and twisted, and now scientists say galaxies ring like a bell long after the cosmic crash.

A team of astronomers from the United States and Canada say they have heard echoes of that ringing, possible evidence of a galactic encounter 100 million years ago when a small satellite galaxy or dark matter object passed through the Milky Way Galaxy; close to our position in the galaxy, as if a rock were thrown into a still pond causing the stars to bounce up and down on the waves. Their results were published in the Astrophysical Journal Letters.

“We have found evidence that our Milky Way had an encounter with a small galaxy or massive dark matter structure perhaps as recently as 100 million years ago,” said Larry Widrow, professor at Queen’s University in Canada. “We clearly observe unexpected differences in the Milky Way’s stellar distribution above and below the Galaxy’s midplane that have the appearance of a vertical wave — something that nobody has seen before.”

Astronomers took observations from about 300,000 nearby stars in the Sloan Digital Sky Survey. Stars move up and down at 20-30 kilometers per second while see-sawing around the galaxy at 220 kilometers per second. By comparison, the International Space Station putters around Earth at 7.71 kilometers per second; Voyager 1, the fastest man-made object, currently is leaving the solar system at about 17.46 kilometers per second. Widrow and colleagues at the University of Kentucky, The University of Chicago and Fermi National Accelerator Laboratory found that the positions of nearby stars is not quite as regular as previously thought. The team noticed a small but statistically significant difference in the distribution of stars above and below the midplane of the Milky Way.

“Our part of the Milky Way is ringing like a bell,” said Brian Yanny, of the Department of Energy’s Fermilab. “But we have not been able to identify the celestial object that passed through the Milky Way. It could have been one of the small satellite galaxies that move around the center of our galaxy, or an invisible structure such as a dark matter halo.”

Susan Gardner, professor of physics at the University of Kentucky added, “The perturbation need not have been a single isolated event in the past, and it may even be ongoing. Additional observations may well clarify its origin.”

Other possibilities considered for the variations were the effect of interstellar dust or simply the way the stars were selected in the survey. But as those events failed to explain fully the observations, the astronomers began to explore possible recent events in the history of the galaxy.

More than 20 visible satellite galaxies circle the Milky Way. Invisible satellites made up of dark matter, hypothetical matter that cannot be seen but is thought to make up a majority of the mass of the Universe, might also orbit our galaxy. Scientists believe that most of the mass orbiting the galaxy is in the form of dark matter. Using computer simulations to explore the effects of a small galaxy or dark matter structure passing through the disk of the Milky Way, the scientists developed a clearer picture of the see-saw effects they were seeing.

In terms of the nine-billion lifetime of the Milky Way Galaxy, the effects are short-lived. This part of the galaxy has been “ringing” for 100 million years and will continue for 100 million years more as the up-and-down motion dissipates, say the astronomers – unless we are hit again.

Image caption: The Small Magellanic Cloud is one of 20 visible satellite galaxies that orbit the Milky Way Galaxy. Astronomers report that a smaller counterpart or dark matter object passed through the Milky Way near our position about 100 million years ago.

Posted on by Jason Major

Astronomers Take “Baby Picture” of an Incredibly Distant Galaxy

False-color image of galaxy LAEJ095950.99+021219.1 (Credit: James Rhoads/ASU)

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Astronomers from Arizona State University have grabbed an image of a dim, distant galaxy, seeing it as it looked only 800 million years after the birth of the Universe. Visible above as a green blob in the center of a false-color image acquired with the Magellan Telescopes at the Las Campanas Observatory in Chile, the galaxy is seen in its infancy and, at 13 billion light-years away, is one of the ten most distant objects ever discovered.

The galaxy, designated LAEJ095950.99+021219.1, was detected by light emitted by ionized hydrogen using the Magellan Telescopes’ IMACS (Inamori-Magellan Areal Camera & Spectrograph) instrument, built at the Carnegie Institute in Washington. In order to even find such a remote object — whose existence had already been suspected — the team had to use a special narrow-band filter on the IMACS instrument designed to isolate specific wavelengths of light.

“Young galaxies must be observed at infrared wavelengths and this is not easy to do using ground-based telescopes, since the Earth’s atmosphere itself glows and large detectors are hard to make,” said team leader Sangeeta Malhotra, an associate professor at ASU who helped develop the technique.

“As time goes by, these small blobs which are forming stars, they’ll dance around each other, merge with each other and form bigger and bigger galaxies. Somewhere halfway through the age of the universe they start looking like the galaxies we see today – and not before.”

– Sangeeta Malhotra, ASU professor 

LAEJ095950.99+021219.1 is seen at a redshift of 7, putting it farther away than any other objects previously discovered using the narrow-band technique.

(What is redshift? Watch “How To Measure The Universe” here.)

“We have used this search to find hundreds of objects at somewhat smaller distances. We have found several hundred galaxies at redshift 4.5, several at redshift 6.5, and now at redshift 7 we have found one,” said James Rhoads, associate professor at ASU and research team leader.

“This image is like a baby picture of this galaxy, taken when the universe was only 5 percent of its current age. Studying these very early galaxies is important because it helps us understand how galaxies form and grow.”

So why does LAEJ095950.99+021219.1 not look much like the galaxies we’re used to seeing in images?

Malhotra explains: “Somewhere halfway through the age of the universe they start looking like the galaxies we see today – and not before. Why, how, when, where that happens is a fairly active area of research.”

The team’s NSF-funded research was published in Astrophysical Journal Letters. Read more on Phys.Org News here.

Posted on by Jason Major

A Tribute to Hubble… and Humanity

Here’s a excellent video compilation featuring images from the Hubble Space Telescope, along with music by Kanye West and quotes from astronomers Neil deGrasse Tyson, Lawrence Krauss and Carl Sagan reflecting on our place in the Universe… and the Universe’s place within each of us.

Uploaded to YouTube by video editor Brandon Fibbs, this is a reminder of how Hubble has opened our eyes to the wonders of the cosmos. Enjoy.

“The cosmos is also within us. We’re made of star stuff… we are a way for the cosmos to know itself.”
– Carl Sagan

Posted on by Jason Major

How To Measure the Universe

The Royal Observatory Greenwich is giving free presentations of "Measuring the Universe: from the Transit of Venus to the Edge of the Cosmos" from now until September 1.


Measuring distance doesn’t sound like a very challenging thing to do — just pick your standard unit of choice and corresponding tool calibrated to it, and see how the numbers add up. Use a meter stick, a tape measure, or perhaps take a drive, and you can get a fairly accurate answer. But in astronomy, where the distances are vast and there’s no way to take measurements in person, how do scientists know how far this is from that and what’s going where?

Luckily there are ways to figure such things out, and the methods that astronomers use are surprisingly familiar to things we experience every day.

[/caption]The video above is shared by the Royal Observatory Greenwich and shows how geometry, physics and things called “standard candles” (brilliant!) allow scientists to measure distances on cosmic scales.

Just in time for the upcoming transit of Venus, an event which also allows for some important measurements to be made of distances in our solar system, the video is part of a series of free presentations the Observatory is currently giving regarding our place in the Universe and how astronomers over the centuries have measured how oh-so-far it really is from here to there.

Video credits:
Design and direction: Richard Hogg
Animation: Robert Milne, Ross Philips, Kwok Fung Lam
Music and sound effects: George Demure
Narration and Astro-smarts: Dr. Olivia Johnson
Producer: Henry Holland

Posted on by Jason Major

Dark Matter Makes a Comeback

The Milky Way an moonrise over ESO's Paranal observatory (ESO/H.H. Heyer)

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Recent reports of dark matter’s demise may be greatly exaggerated, according to a new paper from researchers at the Institute for Advanced Study.

Astronomers with the European Southern Observatory announced in April a surprising lack of dark matter in the galaxy within the vicinity of our solar system.

The ESO team, led by Christian Moni Bidin of the Universidad de Concepción in Chile, mapped over 400 stars near our Sun, spanning a region approximately 13,000 light-years in radius. Their report identified a quantity of material that matched what could be directly observed: stars, gas, and dust… but no dark matter.

“Our calculations show that it should have shown up very clearly in our measurements,” Bidin had stated, “but it was just not there!”

But other scientists were not so sure about some assumptions the ESO team had based their calculations upon.

Researchers Jo Bovy and Scott Tremaine from the Institute for Advanced Study in Princeton, NJ, have submitted a paper claiming that the results reported by Moni Biden et al are “incorrect”, and based on an “invalid assumption” of the motions of stars within — and above — the plane of the galaxy.

(Read: Astronomers Witness a Web of Dark Matter)

“The main error is that they assume that the mean azimuthal (or rotational) velocity of their tracer population is independent of Galactocentric cylindrical radius at all heights,” Bovy and Tremaine state in their paper. “This assumption is not supported by the data, which instead imply only that the circular speed is independent of radius in the mid-plane.”

The researchers point out the stars within the local neighborhood move slower than the average velocity assumed by the ESO team, in a behavior called asymmetric drift. This lag varies with a cluster’s position within the galaxy, but, according to Bovy and Tremaine, “this variation cannot be measured for the sample [used by Moni Biden’s team] as the data do not span a large enough range.”

When the IAS researchers took Moni Biden’s observations but replaced the ESO team’s “invalid” assumptions on star movement within and above the galactic plane with their own “data-driven” ones, the dark matter reappeared.

Artist's impression of dark matter surrounding the Milky Way. (ESO/L. Calçada)

“Our analysis shows that the locally measured density of dark matter is consistent with that extrapolated from halo models constrained at Galactocentric distances,” Bovy and Tremaine report.

As such, the dark matter that was thought to be there, is there. (According to the math, that is.)

And, the two researchers add, it’s not only there but it’s there in denser amounts than average — at least in the area around our Sun.

“The halo density at the Sun, which is the relevant quantity for direct dark matter detection experiments, is likely to be larger because of gravitational focusing by the disk,” Bovy and Tremaine note.

When they factored in their data-driven calculations on stellar velocities and the movement of the halo of non-baryonic material that is thought to envelop the Milky Way, they found that “the dark matter density in the mid-plane is enhanced… by about 20%.”

So rather than a “serious blow” to the existence of dark matter, the findings by Bovy and Tremaine — as well as Moni Biden and his team — may have not only found dark matter, but given us 20% more!

Now that’s a good value.

Read the IAS team’s full paper here.

(Tip of the non-baryonic hat to Christopher Savage, post-doctorate researcher at the Oskar Klein Centre for Cosmoparticle Physics at Stockholm University for the heads up on the paper.)

Posted on by Jason Major

We Are In This Universe; The Universe Is In Us

The latest installment of the excellent Symphony of Science series is out, and like every one of them it’s a fun, inspirational and educational trip through the cosmos with voiceovers by leading astronomers and physicists. These are great, and if you haven’t seen the others be sure to check them out on creator John Boswell’s YouTube channel here.

Read more on the Symphony of Science website.

“We are part of this universe
We are in this universe
The universe is in us
Yes, the universe is in us”

– Neil deGrasse Tyson

Posted on by Nancy Atkinson

Intelligent Alien Dinosaurs?

I for one welcome our alien dinosaur overlords…maybe.

Dinosaurs once roamed and ruled the Earth. Is it possible that similar humongous creatures may have evolved on another planet – a world that DIDN’T get smacked by an asteroid – and later they developed to have human-like, intelligent brains? A recent paper discussing why the biochemical signature of life on Earth is so consistent in orientation somehow segued into the possibility that advanced versions of T. Rex and other dinosaurs may be the life forms that live on other worlds. The conclusion? “We would be better off not meeting them,” said scientist Ronald Breslow, author of the paper.

The building blocks of terrestrial amino acids, sugars, and the genetic materials DNA and RNA have two possible orientations, left or right, which mirror each other in what is called chirality. On Earth, with the exception of a few bacteria, amino acids have the left-handed orientation. Most sugars have a right-handed orientation. How did that homochirality happen?

If meteorites carried specific types of amino acids to Earth about 4 billion years, that could have set the pattern the left-handed chirality in terrestial proteins.

“Of course,” Breslow said in a press release, “showing that it could have happened this way is not the same as showing that it did. An implication from this work is that elsewhere in the universe there could be life forms based on D-amino acids and L-sugars. Such life forms could well be advanced versions of dinosaurs, if mammals did not have the good fortune to have the dinosaurs wiped out by an asteroidal collision, as on Earth.”

But not everyone was impressed with the notion of dinosaurs from space. “None of this has anything to do with dinosaurs,” wrote science author Brian Switek in the Smithsonian blog Dinosaur Tracking. “As much as I’m charmed by the idea of alien dinosaurs, Breslow’s conjecture makes my brain ache. Our planet’s fossil record has intricately detailed the fact that evolution is not a linear march of progress from one predestined waypoint to another. Dinosaurs were never destined to be. The history of life on earth has been greatly influenced by chance and contingency, and dinosaurs are a perfect example of this fact.”

For further reading:
American Chemical Society paper
ACS press release
Dinosaur Tracking blog

Posted on by Jason Major

Polar Telescope Casts New Light On Dark Energy And Neutrino Mass

The 10-meter South Pole Telescope in Antarctica at the Amundsen-Scott Station. (Daniel Luong-Van, National Science Foundation)

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Located at the southermost point on Earth, the 280-ton, 10-meter-wide South Pole Telescope has helped astronomers unravel the nature of dark energy and zero in on the actual mass of neutrinos — elusive subatomic particles that pervade the Universe and, until very recently, were thought to be entirely without measureable mass.

The NSF-funded South Pole Telescope (SPT) is specifically designed to study the secrets of dark energy, the force that purportedly drives the incessant (and apparently still accelerating) expansion of the Universe. Its millimeter-wave observation abilities allow scientists to study the Cosmic Microwave Background (CMB) which pervades the night sky with the 14-billion-year-old echo of the Big Bang.

Overlaid upon the imprint of the CMB are the silhouettes of distant galaxy clusters — some of the most massive structures to form within the Universe. By locating these clusters and mapping their movements with the SPT, researchers can see how dark energy — and neutrinos — interact with them.

“Neutrinos are amongst the most abundant particles in the universe,” said Bradford Benson, an experimental cosmologist at the University of Chicago’s Kavli Institute for Cosmological Physics. “About one trillion neutrinos pass through us each second, though you would hardly notice them because they rarely interact with ‘normal’ matter.”

If neutrinos were particularly massive, they would have an effect on the large-scale galaxy clusters observed with the SPT. If they had no mass, there would be no effect.

The SPT collaboration team’s results, however, fall somewhere in between.

Even though only 100 of the 500 clusters identified so far have been surveyed, the team has been able to place a reasonably reliable preliminary upper limit on the mass of neutrinos — again, particles that had once been assumed to have no mass.

Previous tests have also assigned a lower limit to the mass of neutrinos, thus narrowing the anticipated mass of the subatomic particles to between 0.05 – 0.28 eV (electron volts). Once the SPT survey is completed, the team expects to have an even more confident result of the particles’ masses.

“With the full SPT data set we will be able to place extremely tight constraints on dark energy and possibly determine the mass of the neutrinos,” said Benson.

“We should be very close to the level of accuracy needed to detect the neutrino masses,” he noted later in an email to Universe Today.

The South Pole Telescope's unique position allows it to watch the night sky for months on end. (NSF)

Such precise measurements would not have been possible without the South Pole Telescope, which has the ability due to its unique location to observe a dark sky for very long periods of time. Antarctica also offers SPT a stable atmosphere, as well as very low levels of water vapor that might otherwise absorb faint millimeter-wavelength signals.

“The South Pole Telescope has proven to be a crown jewel of astrophysical research carried out by NSF in the Antarctic,” said Vladimir Papitashvili, Antarctic Astrophysics and Geospace Sciences program director at NSF’s Office of Polar Programs. “It has produced about two dozen peer-reviewed science publications since the telescope received its ‘first light’ on Feb. 17, 2007. SPT is a very focused, well-managed and amazing project.”

The team’s findings were presented by Bradford Benson at the American Physical Society meeting in Atlanta on April 1.

Read more on the NSF press release here.