milky way Archives

September 8, 2016October 5, 2016 by Evan Gough

Best Picture Yet Of Milky Way’s Formation 13.5 Billion Years Ago

The Milky Way is like NGC 4594 (pictured), a disc shaped spiral galaxy with around 200 billion stars. The three main features are the central bulge, the disk, and the halo. Credit: ESO

Maybe we take our beloved Milky Way galaxy for granted. As far as humanity is concerned, it’s always been here. But how did it form? What is its history?

Our Milky Way galaxy has three recognized stellar components. They are the central bulge, the disk , and the halo. How these three were formed and how they evolved are prominent, fundamental questions in astronomy. Now, a team of researchers have used the unique property of a certain type of star to help answer these fundamental questions.

The type of star in question is called the blue horizontal-branch star (BHB star), and it produces different colors depending on its age. It’s the only type of star to do that. The researchers, from the University of Notre Dame, used this property of BHB’s to create a detailed chronographic (time) map of the Milky Way’s formation.

This map has confirmed what theories and models have predicted for some time: the Milky Way galaxy formed through mergers and accretions of small haloes of gas and dust. Furthermore, the oldest stars in our galaxy are at the center, and younger stars and galaxies joined the Milky Way over billions of years, drawn in by the galaxy’s growing gravitational pull.

The team who produced this study includes astrophysicist Daniela Carollo, research assistant professor in the Department of Physics at the University of Notre Dame, and Timothy Beers, Notre Dame Chair of Astrophysics. Research assistant professor Vinicius Placco, and other colleagues rounded out the team.

“We haven’t previously known much about the age of the most ancient component of the Milky Way, which is the Halo System,” Carollo said. “But now we have demonstrated conclusively for the first time that ancient stars are in the center of the galaxy and the younger stars are found at longer distances. This is another piece of information that we can use to understand the assembly process of the galaxy, and how galaxies in general formed.”

This dazzling infrared image from NASA's Spitzer Space Telescope shows hundreds of thousands of stars crowded into the swirling core of our spiral Milky Way galaxy. Credit: NASA/JPL-Caltech — This dazzling infrared image from NASA’s Spitzer Space Telescope shows hundreds of thousands of stars crowded into the swirling core of our spiral Milky Way galaxy. Credit: NASA/JPL-Caltech

The Sloan Digital Sky Survey (SDSS) played a key role in these findings. The team used data from the SDSS to identify over 130,000 BHB’s. Since these stars literally “show their age”, mapping them throughout the Milky Way produced a chronographic map which clearly shows the oldest stars near the center of the galaxy, and youngest stars further away.

“The colors, when the stars are at that stage of their evolution, are directly related to the amount of time that star has been alive, so we can estimate the age,” Beers said. “Once you have a map, then you can determine which stars came in first and the ages of those portions of the galaxy. We can now actually visualize how our galaxy was built up and inspect the stellar debris from some of the other small galaxies being destroyed by their interaction with ours during its assembly.”

Astronomers infer, from various data-driven approaches, that different structural parts of the galaxy have different ages. They’ve assigned ages to different parts of the galaxy, like the bulge. That makes sense, since everything can’t be the same age. Not in a galaxy that’s this old. But this map makes it even clearer.

As the authors say in their paper, “What has been missing, until only recently, is the ability to assign ages to individual stellar populations, so that the full chemo-dynamical history of the Milky Way can be assessed.”

This new map, with over 130,000 stars as data points, is a pretty important step in understanding the evolution of the Milky Way. It takes something that was based more on models and theory, however sound they were, and reinforces it with more constrained data.

Update: The chronographic map, as well as a .gif, can be viewed here.

September 7, 2016September 11, 2016 by Bob King

Terzan 5 May Unlock Secret to Milky Way’s Past

Peering through the thick dust clouds of the galactic bulge (center of the galaxy) an international team of astronomers has revealed the unusual mix of stars in the stellar cluster known as Terzan 5. The new results indicate that Terzan 5 is in fact one of the bulge's primordial building blocks, most likely the relic of the very early days of the Milky Way. Credit: NASA/ESA/Hubble/F. Ferraro

Peering through the thick dust clouds of the galactic bulge an international team of astronomers has revealed the unusual mix of stars in the stellar cluster known as Terzan 5. The new results indicate that Terzan 5 is in fact one of the bulge's primordial building blocks, most likely the relic of the very early days of the Milky Way. Credit: NASA/ESA/Hubble/F. Ferraro — Peering through the thick dust clouds of the galactic bulge (center of the galaxy) an international team of astronomers has revealed the unusual mix of stars in the stellar cluster known as Terzan 5. The new results indicate that Terzan 5 is in fact one of the bulge’s primordial building blocks, most likely the relic of the very early days of the Milky Way. Credit: NASA/ESA/Hubble/F. Ferraro

Not many people have heard of the globular star cluster Terzan 5. It’s a big ball of stars resembling spilled sugar like so many other globular clusters. A very few globulars are bright enough to see with the naked eye; Terzan 5 is faint because it lies far away in the direction of the center of Milky Way galaxy inside its central bulge. Here, the stars that formed at the galaxy’s birth are packed together in great numbers. They are the “old ones” of the Milky Way.

Today, a team of astronomers revealed that Terzan 5 is unlike any globular cluster known. Most Milky Way globulars contain stars of just one age, about 11-12 billion years. They formed around the same time as the Milky Way itself, used up all their available gas early to build stars and then spent the remaining billions of years aging. Most orbit the galaxy’s center in a vast halo like moths whirring around a bright light. Oddball Terzan 5 has two populations aged 12 billion and 4.5 billion years old and it’s located inside the galactic bulge.

Globular clusters are distributed in a spherical halo about the core or bulge in the Milky Way galaxy. The Sun and planets are located well away from the center. From our perspective, most globular clusters appear concentrated in the direction of the galaxy's center. Credit: Science Frontiers Online — Globular clusters are distributed in a spherical halo about the star-rich core or bulge at the center of the disk of the Milky Way galaxy. Credit: Science Frontiers Online

The team used the cameras on the Hubble Space Telescope as well as a host of ground-based telescopes to find compelling evidence for the two distinct kinds of stars. Not only do they show a large gap in age, but the differ in the elements they contain. Terzan 5’s dual populations point to a star formation process that wasn’t continuous but dominated by two distinct bursts of star formation.

“This requires the Terzan 5 ancestor to have large amounts of gas for a second generation of stars and to be quite massive. At least 100 million times the mass of the Sun,” explains Davide Massari, co-author of the study.

Its unusual properties make Terzan 5 the ideal candidate for the title of “living fossil” from the early days of the Milky Way. Current theories on galaxy formation assume that vast clumps of gas and stars interacted to form the primordial bulge of the Milky Way, merging and dissolving in the process.

While the properties of Terzan 5 are uncommon for a globular cluster, they’re very similar to the stars found in the galactic bulge. Remnants of those gaseous clumps appear to have stuck around intact since the days of our galaxy’s birth, one of them evolving into the present day Terzan 5. That makes it a relic from the Milky Way’s infant days and one of the earliest galactic building blocks. Later, the cluster, which held onto some of its remaining gas, experienced a second burst of star formation.

This current model of the Milky Way galaxy shows the yellow-hued galactic bulge formed by ancient stars well along in their evolution, in contrast to the bluer, younger stars in the spiral arms. Credit: NASA/JPL-Caltech/R. Hurt (SSC/Caltech)

“Some characteristics of Terzan 5 resemble those detected in the giant clumps we see in star-forming galaxies at high-redshift (galaxies just beginning to form in the remote universe in the far distant past), suggesting that similar assembling processes occurred in the local and in the distant universe at the epoch of galaxy formation,” said Dr. Francesco Ferraro from the University of Bologna, Italy, who headed up the team.

The Milky Way on a late September night offers an opportunity to contemplate the grand form of the galaxy. Credit: Bob King

Terzan 5’s chandelier-like presence is helping astronomers understand how our galaxy was assembled. Reconstructing the past is one of the key occupations of astronomy. The present is continually departing with every passing moment. Soon enough, every piece of information slips into the past tense. In the near-past, which records humanity’s comings and goings, details are often forgotten or lost. The deep past is even worse. With no one around and only scattered clues, astronomers continually look for fragmental remains that when woven into the fabric of a theory, reveal patterns and processes before we came to be.

August 30, 2016September 26, 2016 by Evan Gough

6 Million Years Ago The Milky Way’s Supermassive Black Hole Raged

Artist's concept of Sagittarius A, the supermassive black hole at the center of our galaxy. Credit: NASA/JPL

6 million years ago, when our first human ancestors were doing their thing here on Earth, the black hole at the center of the Milky Way was a ferocious place. Our middle-aged, hibernating black hole only munches lazily on small amounts of hydrogen gas these days. But when the first hominins walked the Earth, Sagittarius A was gobbling up matter and expelling gas at speeds reaching 1,000 km/sec. (2 million mph.)

The evidence for this hyperactive phase in Sagittarius’ life, when it was an Active Galactic Nucleus (AGN), came while astronomers were searching for something else: the Milky Way’s missing mass.

There’s a funny problem in our understanding of our galactic environment. Well, it’s not that funny. It’s actually kind of serious, if you’re serious about understanding the universe. The problem is that we can calculate how much matter we should be able to see in our galaxy, but when we go looking for it, it’s not there. This isn’t just a problems in the Milky Way, it’s a problem in other galaxies, too. The entire universe, in fact.

Our measurements show that the Milky Way has a mass about 1-2 trillion times greater than the Sun. Dark matter, that mysterious and invisible hobgoblin that haunts cosmologists’ nightmares, makes up about five sixths of that mass. Regular, normal matter makes up the last sixth of the galaxy’s mass, about 150-300 billion solar masses. But we can only find about 65 billion solar masses of that normal matter, made up of the familiar protons, neutrons, and electrons. The rest is missing in action.

Astrophysicists at the Harvard-Smithsonian Center for Astrophysics have been looking for that mass, and have written up their results in a new paper.

“We played a cosmic game of hide-and-seek. And we asked ourselves, where could the missing mass be hiding?” says lead author Fabrizio Nicastro, a research associate at the Harvard-Smithsonian Center for Astrophysics (CfA) and astrophysicist at the Italian National Institute of Astrophysics (INAF).

“We analyzed archival X-ray observations from the XMM-Newton spacecraft and found that the missing mass is in the form of a million-degree gaseous fog permeating our galaxy. That fog absorbs X-rays from more distant background sources,” Nicastro continued.

Artist's impression of the ESA's XMM Newton Spacecraft. Image credit: ESA — Artist’s impression of the ESA’s XMM Newton Spacecraft. Image credit: ESA

Nicastro and the other scientists behind the paper analyzed how the x-rays were absorbed and were able to calculate the amount and distribution of normal matter in that fog. The team relied heavily on computer models, and on the XMM-Newton data. But their results did not match up with a uniform distribution of the gaseous fog. Instead, there is an empty “bubble”, where this is no gas. And that bubble extends from the center of the galaxy two-thirds of the way to Earth.

What can explain the bubble? Why would the gaseous fog not be spread more uniformly through the galaxy?

Clearing gas from an area that large would require an enormous amount of energy, and the authors point out that an active black hole would do it. They surmise that Sagittarius A was very active at that time, both feeding on gas falling into itself, and pumping out streams of hot gas at up to 1000 km/sec.

Which brings us to present day, 6 million years later, when the shock-wave caused by that activity has travelled 20,000 light years, creating the bubble around the center of the galaxy.

Another piece of evidence corroborates all this. Near the galactic center is a population of 6 million year old stars, formed from the same material that at one time flowed toward the black hole.

“The different lines of evidence all tie together very well,” says Smithsonian co-author Martin Elvis (CfA). “This active phase lasted for 4 to 8 million years, which is reasonable for a quasar.”

The numbers all match up, too. The gas accounted for in the team’s models and observations add up to 130 billion solar masses. That number wraps everything up pretty nicely, since the missing matter in the galaxy is thought to be between 85 billion and 235 billion solar masses.

This is intriguing stuff, though it’s certainly not the final word on the Milky Way’s missing mass. Two future missions, the European Space Agency’s Athena X-ray Observatory, planned for launch in 2028, and NASA’s proposed X-Ray Surveyor could provide more answers.

Who knows? Maybe not only will we learn more about the missing matter in the Milky Way and other galaxies, we may learn more about the activity at the center of the galaxy, and what ebbs and flows it has gone through, and how that has shaped galactic evolution.

June 17, 2016March 27, 2017 by Fraser Cain

Weekly Space Hangout – June 17, 2016: LIGO Team

Host: Fraser Cain (@fcain)

Special Guest: LIGO Team Members:Kai Staats and Michael Landry
Kai Staats is a filmmaker, lecturer and writer working in science outreach. He is currently completing his MSc thesis for his research in machine learning applied to radio astronomy at the University of Cape Town and the Square Kilometer Array, South Africa. Staats was for ten years CEO of a Linux OS and HPC solutions provider whose systems were used to process images at NASA JPL, conduct sonar imaging on-board Navy submarines, and conduct bioinformatics research at DoE labs. In 2012 Staats engaged his passion for storytelling through film. His work includes sci-fi, human interest, wildlife conservation, and science outreach and education. “LIGO Detection” marks Staats’ 3rd film for the gravitational wave observatory that in February announced detection of merging black holes.

Mike Landry is Detection Lead Scientist at LIGO Hanford Observatory (LHO), Washington State. He began working on LIGO in 2000 as a Caltech postdoc at LHO, and has remained there since. Mike has worked on a variety of aspects of the experiment, including commissioning, calibration, and searches for gravitational waves from spinning neutron stars. From 2010 to 2015, he led the installation of Advanced LIGO at Hanford. Prior to working on LIGO, he received his Ph.D. in particle and nuclear physics from the University of Manitoba, for studies in strange hadronic physics at the Brookhaven National Laboratory’s AGS accelerator.

Guests:
Paul M. Sutter (pmsutter.com / @PaulMattSutter)
Morgan Rehnberg (MorganRehnberg.com / @MorganRehnberg)
Kimberly Cartier (@AstroKimCartier )

Their stories this week:
The discovery of a habitable zone “Tatooine” planet

Experimenting with igniting fires in space

1/3 of the world (and 80% of Americans) can’t see the Milky Way

Eight space telescopes are renewed by NASA

We’ve had an abundance of news stories for the past few months, and not enough time to get to them all. So we are now using a tool called Trello to submit and vote on stories we would like to see covered each week, and then Fraser will be selecting the stories from there. Here is the link to the Trello WSH page (http://bit.ly/WSHVote), which you can see without logging in. If you’d like to vote, just create a login and help us decide what to cover!

We record the Weekly Space Hangout every Friday at 12:00 pm Pacific / 3:00 pm Eastern. You can watch us live on Google+, Universe Today, or the Universe Today YouTube page.

You can also join in the discussion between episodes over at our Weekly Space Hangout Crew group in G+!

June 7, 2016June 7, 2016 by Cory Schmitz

Metropolitan Milky Way

JanikAlheit-CPTMilkyPano — A breathtakingly rare view of the southern hemisphere Milky Way above a major city - a 42-panel panorama. Photo: Janik Alheit

This article was written by contributing author Janik Alheit, and is used by permission from the original at PhotographingSpace.com.

When it comes to my style of photography, preparation is a key element in getting the shot I want.

On this specific day, we were actually planning on only shooting the low Atlantic clouds coming into the city of Cape Town. This in itself takes a lot of preparation as we had to keep a close eye on the weather forecasts for weeks using Yr.no, and the conditions are still unpredictable at best even with the latest weather forecasting technology.

We set out with cameras and camping gear with the purpose of setting up camp high up on Table Mountain so as to get a clear view over the city. The hike is extremely challenging at night, especially with a 15kg backpack on your back! We reached our campsite at about 11pm, and then started setting up our cameras for the low clouds predicted to move into the city at about 3am the next morning. For the next 2 hours or so we scouted for the best locations and compositions, and then tried to get a few hours of sleep in before the clouds arrived.

At about 3am I was woken up by fellow photographer Brendon Wainwright. I realised that he had been up all night shooting timelapses, and getting pretty impressive astro shots even though we were in the middle of the city. I noticed that the clouds had rolled in a bit earlier than predicted and had created a thick blanket over the city, which was acting as a natural light pollution filter.

I looked up at the skies and for the first time in my life I was able to see the core of the Milky Way in the middle of the city! This is when everything changed, the mission immediately became an astrophotography mission, as these kind of conditions are extremely rare in the city.

How to Photograph the Milky Way — Learn how to shoot the Milky Way at PhotographingSpace.com!

Composition

After shooting the city and clouds for a while, I turned my focus to the Milky Way. I knew I was only going to have this one opportunity to capture an arching Milky Way over a city covered with clouds, so I had to work fast to get the perfect composition before the clouds changed or faded away.

I set my tripod on top of a large rock that gave me a bit of extra height so that I could get as much of the city lights in the shot as possible. The idea I had in my mind was to shoot a panorama from the center of the city to the Twelve Apostles Mountains in the southwest. This was a pretty large area to cover, plus the Milky Way was pretty much straight above us which meant I had to shoot a massive field of view in order to get both the city and the Milky Way.

The final hurdle was to get myself into the shot, which meant that I had to stand on a 200m high sheer cliff edge! Luckily this was only necessary for one frame in the entire panorama.

Gear and settings

I usually shoot with a Canon 70D with an 18mm f/3.5 lens and a Hahnel Triad 40Lite tripod. This particular night I forgot to bring a spare battery for my Canon and by the time I wanted to shoot this photo, my one battery had already died!

Luckily I had a backup camera with me, an Olympus OMD EM10 mirrorless camera. I had no choice but to use this camera for the shot. The lens on that camera was an Olympus M.Zuiko 14-42mm f/3.5 kit lens, which was not ideal, but I just had to make it work.

I think this photo is a testament to the fact that your gear is not nearly as important as your technique and knowledge of your surroundings and your camera.

I started off by shooting the first horizontal line of photos, in landscape orientation, to form the bottom edge of the final stitched photo. From there I ended up shooting 6 rows of 7 photos each in order to capture the whole view I wanted. This gave me 42 photos in total.

For the most part, my settings were 25 seconds, f/3.5, ISO 2000, with the ISO dropped on a few of the pictures where the city light was too bright. I shot all the photos in raw as to get as much data out of each frame as possible.

Editing

Astrophotography is all about the editing techniques.

In this scenario I had to stitch 42 photos into one photo. Normally I would just use the built-in function in Lightroom, but in this case I had to use software called PTGui Pro, which is made for stitching difficult panoramas. This software enables me to choose control points on the overlapping images in order to line up the photos perfectly.

After creating the panorama in PTGui Pro, I exported it as a TIFF file and then imported that file into Lightroom again. Keep in mind that this one file is now 3GB as it is made up of 42 RAW files!

In Lightroom I went through my normal workflow to bring out the detail in the Milky Way by boosting the highlights a bit, adding contrast, a bit of clarity, and bringing out some shadows in the landscape. The most difficult part was to clear up the distortion that was caused by the faint clouds in the sky between individual images. Unfortunately it is almost impossible to blend so many images together perfectly when you have faint clouds in the sky that form and disappear within minutes, but I think I did the best job I could to even out the bad areas.

A special event

After the final touches were made and the photo was complete, I realized that I had captured something really unique. It’s not every day that you see low clouds hanging over the city, and you almost never see the Milky Way so bright above the city, and I managed to capture both in one image!

The response to the image after posting it to my Instagram account was extremely overwhelming. I got people from all over the world wanting to purchase the image and it got shared hundreds of time across all social media.

It just shows you that planning and dedication does pay off!

April 15, 2016April 15, 2016 by Evan Gough

A Super-Fast Star System Shrugs Its Shoulders At Physics

This annotated artist's conception illustrates our current understanding of the structure of the Milky Way galaxy. Image Credit: NASA

Astronomers have found a pair of stellar oddballs out in the edges of our galaxy. The stars in question are a binary pair, and the two companions are moving much faster than anything should be in that part of the galaxy. The discovery was reported in a paper on April 11, 2016, in the Astrophysical Journal Letters.

The binary system is called PB3877, and at 18,000 light years away from us, it’s not exactly in our neighborhood. It’s out past the Scutum-Centaurus Arm, past the Perseus Arm, and even the Outer Arm, in an area called the galactic halo. This binary star also has the high metallicity of younger stars, rather than the low metallicity of the older stars that populate the outer reaches. So PB3877 is a puzzle, that’s for sure.

PB3877 is what’s called a Hyper-Velocity Star (HVS), or rogue star, and though astronomers have found other HVS’s, more than 20 of them in fact, this is the first binary one found. The pair consists of a hot sub-dwarf primary star that’s over five times hotter than the Sun, and a cooler companion star that’s about 1,000 degrees cooler than the Sun.

Hyper-Velocity stars are fast, and can reach speeds of up to 1,198 km. per second, (2.7 million miles per hour,) maybe faster. At that speed, they could cross the distance from the Earth to the Moon in about 5 minutes. But what’s puzzling about this binary star is not just its speed, and its binary nature, but its location.

Hyper-Velocity stars themselves are rare, but PB3877 is even more rare for its location. Typically, hyper velocity stars need to be near enough to the massive black hole at the center of a galaxy to reach their incredible speeds. A star can be drawn toward the black hole, accelerated by the unrelenting pull of the hole, then sling-shotted on its way out of the galaxy. This is the same action that spacecraft can use when they gain a gravity assist by travelling close to a planet.

This video shows how stars can accelerate when their orbit takes them close to the super-massive black holes at the center of the Milky Way.

But the trajectory of PB3877 shows astronomers that it could not have originated near the center of the galaxy. And if it had been ejected by a close encounter with the black hole, how could it have survived with its binary nature intact? Surely the massive pull of the black hole would have destroyed the binary relationship between the two stars in PB3877. Something else has accelerated it to such a high speed, and astronomers want to know what, exactly, did that, and how it kept its binary nature.

Barring a close encounter with the super-massive black hole at the center of the Milky Way, there are a couple other ways that PB3877 could have been accelerated to such a high velocity.

One such way is a stellar interaction or collision. If two stars were travelling at the right vectors, a collision between them could impart energy to one of them and propel it to hyper-velocity. Think of two pool balls on a pool table.

Another possibility is a supernova explosion. It’s possible for one of the stars in a binary pair to go supernova, and eject it’s companion at hyper-velocity speeds. But in these cases, either stellar collision or supernova, things would have to work out just right. And neither possibility explains how a wide-binary system like this could stay intact.

Fraser Cain sheds more light on Hyper-Velocity Stars, or Rogue Stars, in this video.

There is another possibility, and it involves Dark Matter. Dark Matter seems to lurk on the edge of any discussion around something unexplained, and this is a case in point. The researchers think that there could be a massive cocoon or halo of Dark Matter around the binary pair, which is keeping their binary relationship intact.

As for where the binary star PB3788 came from, as they say in the conclusion of their paper, “We conclude that the binary either formed in the halo or was accreted from the tidal debris of a dwarf galaxy by the Milky Way.” And though the source of this star’s formation is an intriguing question, and researchers plan follow up study to verify the supernova ejection possibility, its possible relationship with Dark Matter is also intriguing.

March 14, 2016March 18, 2016 by Evan Gough

The Milky Way Galaxy’s Dark Halo Of Star Formation

Dark matter is invisible. Based on the effect of gravitational lensing, a ring of dark matter has been inferred in this image of a galaxy cluster (CL0024+17) and has been represented in blue. Image: NASA/ESA.

Dark Matter is rightly called one of the greatest mysteries in the Universe. In fact, so mysterious is it, that we here in the opulent sky-scraper offices of Universe Today often joke that it should be called “Dark Mystery.” But that sounds like a cheesy History Channel show, and here at Universe Today we don’t like cheesy, so Dark Matter it remains.

Though we still don’t know what exactly Dark Matter is, we keep learning more about how it interacts with the rest of the Universe, and nibbling around at the edges of what it might be. But before we get into the latest news about Dark Matter, it’s worth stepping back a bit to remind ourselves of what is known about Dark Matter.

Evidence from cosmology shows that about 25% of the mass of the Universe is Dark Matter, also known as non-baryonic matter. Baryonic matter is ‘normal’ matter, which we are all familiar with. It’s made up of protons and neutrons, and it’s the matter that we interact with every day.

Cosmologists can’t see the 25% of matter that is Dark Matter, because it doesn’t interact with light. But they can see the effect it has on the large scale structure of the Universe, on the cosmic microwave background, and in the phenomenon of gravitational lensing. So they know it’s there.

Large galaxies like our own Milky Way are surrounded by what is called a halo of Dark Matter. These huge haloes are in turn surrounded by smaller sub-haloes of Dark Matter. These sub-haloes have enough gravitational force to form dwarf galaxies, like the Milky Way’s own Sagittarius and Canis Major dwarf galaxies. Then, these dwarf galaxies themselves have their own Dark Matter haloes, which at this scale are now much too small to contain gas or stars. Called dark satellites, these smaller haloes are of course invisible to telescopes, but theory states they should be there.

But proving that these dark satellites are even there requires some evidence of the effect they have on their host galaxies.

Now, thanks to Laura Sales, who is an assistant professor at the University of California, Riverside’s, Department of Physics and Astronomy, and her collaborators at the Kapteyn Astronomical Institute in the Netherlands, Tjitske Starkenberg and Amina Helmi, there is more evidence that these dark satellites are indeed there.

In their paper “Dark influences II: gas and star formation in minor mergers of dwarf galaxies with dark satellites,” from November 2015, they provide an analysis of theory-based computer simulations of the interaction between a dwarf galaxy and a dark satellite.

Their paper shows that when a dark satellite is at its closest point to a dwarf galaxy, the satellite’s gravitational influence compresses the gas in the dwarf. This causes a sustained period of star formation, called a starburst, that can last for billions of years.

NGC 5253 is one of the nearest of the known Blue Compact Dwarf (BCD) galaxies, and is located at a distance of about 12 million light-years from Earth in the southern constellation of Centaurus. It is experiencing a starburst of hot, young stars, which could be caused by dark satellites. Image: NASA/ESA/Hubble.

Their modelling suggests that dwarf galaxies should be exhibiting a higher rate of star formation than would otherwise be expected. And observation of dwarf galaxies reveals that that is indeed the case. Their modelling also suggests that when a dark satellite and a dwarf galaxy interact, the shape of the dwarf galaxy should change. And again, this is born out by the observation of isolated spheroidal dwarf galaxies, whose origin has so far been a mystery.

The exact nature of Dark Matter is still a mystery, and will probably remain a mystery for quite some time. But studies like this keep shining more light on Dark Matter, and I encourage readers who want more detail to read it.

February 26, 2016February 9, 2021 by Fraser Cain

Weekly Space Hangout – Feb. 26, 2016: Fast Radio Bursts & Missing Baryons

Host: Fraser Cain (@fcain)

Guests:

Kimberly Cartier (@AstroKimCartier )
Dave Dickinson (www.astroguyz.com / @astroguyz)
Jolene Creighton (fromquarkstoquasars.com / @futurism)
Nicole Gugliucci (cosmoquest.org / @noisyastronomer)

Their stories this week:
Mysterious Fast Radio Bursts Solve Missing Baryon Problem

Search Narrows for Planet Nine

WFIRST Unveiled

Double Shadow Transit Season Begins

Pulsar “Web” search for gravitational waves

Milky Way Survey of Gas and Dust Completed

Mars in 3 days? Hm.

Scott Kelly to return to Earth on March 1 – why was he in space for a year?

We’ve had an abundance of news stories for the past few months, and not enough time to get to them all. So we’ve started a new system. Instead of adding all of the stories to the spreadsheet each week, we are now using a tool called Trello to submit and vote on stories we would like to see covered each week, and then Fraser will be selecting the stories from there. Here is the link to the Trello WSH page (http://bit.ly/WSHVote), which you can see without logging in. If you’d like to vote, just create a login and help us decide what to cover!

We record the Weekly Space Hangout every Friday at 12:00 pm Pacific / 3:00 pm Eastern. You can watch us live on Google+, Universe Today, or the Universe Today YouTube page.

You can also join in the discussion between episodes over at our Weekly Space Hangout Crew group in G+!

February 10, 2016March 18, 2016 by Evan Gough

Great Attractor Revealed? Galaxies Found Lurking Behind the Milky Way

Milky Way by Matt Dieterich — Milky Way (without the constellations) by Matt Dieterich

Hundreds of galaxies hidden from sight by our own Milky Way galaxy have been studied for the first time. Though only 250 million light years away—which isn’t that far for galaxies—they have been obscured by the gas and dust of the Milky Way. These galaxies may be a tantalizing clue to the nature of The Great Attractor.

On February 9th, an international team of scientists published a paper detailing the results of their study of these galaxies using the Commonwealth Scientific and Industrial Research Organization’s (CSIRO) Parkes radio telescope, a 64 meter telescope in Australia. The ‘scope is equipped with an innovative new multi-beam receiver, which made it possible to peer through the Milky Way into the galaxies behind it.

The area around the Milky Way that is obscured to us is called the Zone of Avoidance (ZOA). This study focused on the southern portion of the ZOA, since the telescope is in Australia. (The northern portion of the ZOA is currently being studied by the Arecibo radio telescope, also equipped with the new multi-beam receiver.) The significance of their work is not that they found hundreds of new galaxies. There was no reason to suspect that galactic distribution would be any different in the ZOA than anywhere else. What’s significant is what it will tell us about The Great Attractor.

The Great Attractor is a feature of the large-scale structure of the Universe. It is drawing our Milky Way galaxy, and hundreds of thousands of other galaxies, towards it with the gravitational force of a million billion suns. The Great Attractor is an anomaly, because it deviates from our understanding of the universal expansion of the universe. “We don’t actually understand what’s causing this gravitational acceleration on the Milky Way or where it’s coming from,” said Professor Lister Staveley-Smith of The University of Western Australia, the lead author of the study.

“We know that in this region there are a few very large collections of galaxies we call clusters or superclusters, and our whole Milky Way is moving towards them at more than two million kilometres per hour.”

The core of the Milky Way seen in Infrared. Seeing through this has been a real challenge. Credit: NASA/Spitzer

Professor Staveley-Smith and his team reported that they found 883 galaxies, of which over one third have never been seen before. “The Milky Way is very beautiful of course and it’s very interesting to study our own galaxy but it completely blocks out the view of the more distant galaxies behind it,” he said.

The team identified new structures in the ZOA that could help explain the movement of The Milky Way, and other galaxies, towards The Great Attractor, at speeds of up to 200 million kilometres per hour. These include three galaxy concentrations, named NW1, NW2, and NW3, and two new clusters, named CW1 and CW2.

University of Cape Town astronomer Professor Renée Kraan-Korteweg, a member of the team who did this work, says “An average galaxy contains 100 billion stars, so finding hundreds of new galaxies hidden behind the Milky Way points to a lot of mass we didn’t know about until now.”

How exactly these new galaxies affect The Great Attractor will have to wait for further quantitative analysis in a future study, according to the paper. The data from the Arecibo scope will show us the northern hemisphere of the ZOA, which will also help build our understanding. But for now, just knowing that there are hundreds of new galaxies in our region of space sheds some light on the large-scale structure of our neighbourhood in the universe.

January 27, 2016January 27, 2016 by Fraser Cain

Milky Way with Nearby Constellations by Matt Dieterich

Constellations near the Milky Way by Matt Dieterich

Here’s an amazing photograph of the Milky Way by astrophotographer Matt Dieterich. He took the image a step further, however, and identified all the constellations you can see close to the Milky Way.

You’ll want to click this image and see a bigger version.

milky way constellations — Full panoramic view of the constellations near the Milky Way by Matt Dieterich

Right down near the horizon is Sagittarius – it looks like a teapot, with the Milky Way rising like steam from its spout. Many of the brightest, most spectacular nebulae in the night sky are located around this constellation: the Lagoon Nebula, Trifid Nebula, and the Omega Nebula. The 4 million solar mass supermassive black hole located at the center of the Milky Way is located in this region too.

Further up the Milky Way you can see the three constellations that form the Summer Triangle: Lyra, Cygnus and Aquila.

And right on the left side of the photograph is Cassiopeia, with its familiar “W” shape.

In the lower-right of the image are a few constellations from the zodiac: Scorpio, Libra and Virgo. And if you look closely you can see Saturn making its way across the sky, in the plane of the ecliptic.

If you’re interested in learning about the night sky, I highly recommend you take your time and learn your constellations. These are your wayposts, navigational aides that help you find your way across the Universe, to the wonders right there in the sky above you.

Matt used a Nikon D750 camera with a 24mm f/1.4 lens. The whole image is made up of 20 separate exposures of 15 seconds each, stitched together to make this amazing mosaic. He captured this image from Glacier National Park in Northern Montana.

Here’s the original version, without the highlighted constellations. Once again, you’ll want to click to see the full resolution goodness.

You’ll want to check out the full resolution version on Matt’s Flickr page.

A big thanks to Matt for contributing this picture to the Universe Today Flickr pool. If you’re an astrophotographer, you’ll be in good company, with thousands of other photographers who share their pictures. We’ve got more than 33,000 pictures there now.