Astronomy Archives

August 16, 2007December 26, 2015 by Fraser Cain

Galaxy Cluster Collision Creates a Dark Matter Core

This strange photograph is a composite image of Abell 520, a massive cluster of galaxies in the process of colliding with one another – it’s one of the most massive structures in the Universe. Several different instruments and observatories came together to produce the image, and the final result gave astronomers a big mystery: its dark matter is behaving strangely.

When galaxies collide, three ingredients come into play: individual galaxies and their billions of stars, hot gas in between the galaxies, and the mysterious dark matter that actually makes up the bulk of the mass. Optical telescopes can see the light from the stars in the galaxies, and X-ray observatories, like Chandra can see the radiation pouring out of the superheated gas. But the presence of dark matter has to be calculated by the way it warps light from more distant objects.

During gigantic collisions like this, astronomers believed that the dark matter and galaxies should stay together, even during the most violent collisions. And this was seen in another galaxy collision: the so-called Bullet Cluster. But in the collision of Abell 520, something surprising was seen.

They found a dark matter core, containing hot gas, but no galaxies. For some reason, the galaxies were stripped away from the densest part of the dark matter. Here’s what Dr. Hendrik Hoekstra, from the University of Victoria had to say:

“It blew us away that it looks like the galaxies are removed from the densest core of dark matter. This would be the first time we’ve seen such a thing and could be a huge test of our knowledge of how dark matter behaves.”

In addition to this core, they also found a corresponding “light region”, which had galaxies, but little or no dark matter. Somehow this collision separated the dark matter from the regular matter.

So what could have stripped these two apart? One possibility is that the galaxies and dark matter were torn apart by a series of gravitational slingshots. Unfortunately, the researchers weren’t able to come up with a realistic computer simulation that had gravitational interactions powerful enough to do this.

Here’s the stranger possibility: we know that dark matter is affected by gravity, but maybe there’s also some kind of unknown interaction between particles of dark matter. This would be extremely difficult to detect since we can’t even see the stuff.

The astronomers have secured time with the Hubble Space Telescope, and will come back and take another look with its powerful gaze. This should help answer some of the mysteries they’ve unearthed.

Original Source: Chandra News Release

August 15, 2007December 26, 2015 by Fraser Cain

Self Organizing Space Dust Could Be a Precursor to Life

As if searching for life wasn’t already difficult enough, physicists now think that clouds of particles in space could mimic the behaviour of life: dividing, replicating and even evolving. This discovery could help scientists understand how life got started here on Earth, and offers intriguing possibilities for life that could evolve in the interstellar clouds of outer space.

This discovery comes from European and Australian researchers, and their work is published in today’s issue of the New Journal of Physics. They developed computer simulations that showed how clouds of molecules naturally organize themselves into complex helix-like structures that resemble DNA.

Over time, an electrical process called polarization organizes the molecules into more and more complex structures. According to the researchers, this suggests a mechanism where organic molecules could assemble faster than in previous models. This shorter time frame means that complex life could be prevalent across the Universe – they get part of the way in space, and then finish off when they reach a planet. Astronomers have already observed vast clouds of these particles out in space with radio telescopes.

Life on Earth requires water, and these molecules wouldn’t have access to the liquid in the near absolute zero temperatures of interstellar space; however, they are able to interact through this polarization process. So there might be a limit, where the structures can’t become complex enough to seed life on young planets. But this process could begin the formation of life, from a random collection of atoms to more complex molecules, and eventually the precursors of life. Evolution could then take over.

Original Source: Science Now

August 15, 2007December 26, 2015 by Fraser Cain

That’s Not a Comet, that’s a Star

If you take a quick look at the photograph with this story you’d think you’re looking at a comet. I’ve actually got it cut down the image a little to fit the website. To really see the full-sized version, check out this link. Well, that’s not a comet, it’s actually the star Mira, moving so fast through interstellar space that it’s leaving a tail behind.

Mira is an older, red giant star shedding massive amounts of material into space. As the star moves quickly through interstellar space, the particles slow down, and remain as a long tail stretching behind. In fact, this tail is 13 light-years long, or 20,000 times the average distance of Pluto from the Sun.

The image was captured by NASA’s Galaxy Evolution Explorer satellite, and the researchers announced their findings during a NASA press conference today. Their research will be published in the latest issue of the journal Nature.

Billions of years ago, Mira was probably quite similar to our own Sun. As it ran out of hydrogen fuel, the star swelled up, becoming an enormous red giant. It’s known as a variable red giant, and pulsates on a regular basis, puffing up its outer layers and brightening enough to be visible with the unaided eye. Eventually the star will run out of material, and settle down as a white dwarf star.

Since it’s traveling at 130 km/s (80 miles/s), all this material cast off by Mira builds up on the leading side; it creates a bow shock in the front, where sloughed off gas is compressed as it encounters the interstellar winds. The compression causes the gas to heat up and blaze in the ultraviolet spectrum. This material then swirls around behind the star, creating a turbulent, tail-like wake. Since the tail is only visible in the ultraviolet spectrum, it took NASA’s Galaxy Evolution Explorer -which mainly observes in ultraviolet – to find it.

Original Source: Nasa News

August 14, 2007December 26, 2015 by Fraser Cain

Hidden Galaxies Ablaze with Star Formation

We have a few pockets of star formation here in the Milky Way. But new galaxies have been discovered, 12 billion light years away, with 1000 times as much star formation. These galaxies are seen just a few billion years after the Big Bang, and they should be incredibly bright. But they aren’t; they’re hiding.

The galaxies were discovered using the AzTEC imaging camera on the James Clerk Maxwell Telescope. Under visible light, these galaxies have shrouded themselves completely in gas and dust. This camera observes in the infrared spectrum, where radiation isn’t completely obscured by dust.

The discovering astronomers first turned up several hundred candidate galaxies in the infrared and submillimeter wavelengths as part of a large survey. Then they did follow-on observations of the 7 brightest candidates using the Smithsonian’s Submillimeter array to pinpoint the exact location of each galaxy. This let them confirm that the bright candidates were indeed individual galaxies, and not clusters of galaxies blurring together.

Once they had the precise locations, they used even more powerful instruments, like Hubble, the Spitzer Space Telescope, and the Very Large Array of radio telescopes. The galaxies were hidden to Hubble, but detectable by Spitzer, which could pierce through the dust in the infrared spectrum to see the stars in the galaxy. The Very Large Array could only see two of the brightest galaxies.

Astronomers believe these galaxies have such huge levels of star formation because they have recently undergone mergers and collisions. The source of the infrared radiation is actually very compact, and the galaxies could be evolving into quasars.

Original Source: CfA News Release

August 9, 2007December 26, 2015 by Fraser Cain

The Galaxy Zoo is Busy

I introduced you to the Galaxy Zoo a few weeks ago. You know, the online site where you use your powerful human brain to help catalog galaxies for science. As I predicted in my article, the response was overwhelming.

According to a recent press release from the Galaxy Zoo project:

“The response has been breathtaking,” said Alex Szalay from Johns Hopkins University, a member of the Galaxy Zoo team. “The traffic was 20 times higher than what we hoped for. This shows the public is really interested in science if they feel they can contribute in a meaningful way.”

The public wants to make a meaningful contribution to science. I could have told them that.

Anyway, right after launch, their website was buried by visitors. In fact, the demand was so great that they blew a circuit breaker in their computer room. The team has been catching up quickly. They’ve upgraded their computer hardware, just to keep ahead of demand, and they’re already hard at work analyzing the fountains of data generated.

Here’s the funny part. At its peak, humans were classifying more than 60,000 galaxies an hour. Since their stated goal is 1 million galaxies, that should have taken them the better part of a single day to wrap up the project.

I hope someone else out there appreciates the power and enthusiasm of the public to perform this kind of service. The gap between professional and amateur is closing, and the contributions made by the public can be nothing short of awe-inspiring.

People love to help out.

Original Source:Sloan Digital Sky Survey

August 8, 2007December 26, 2015 by Fraser Cain

Hidden Cluster Seen For the First Time

This newly released photograph taken by the Spitzer Space Telescope is of a previously hidden star cluster, revealed now in the infrared spectrum. At visible wavelengths, this cluster, located in the southern portion of the Serpens cloud would be totally obscured by dust. But now, thanks to Spitzer, we can see it for the first time.

The cluster was discovered by Robert Gutermuth and Tyler Bourke, from the Harvard-Smithsonian Center for Astrophysics. They originally uncovered it using the Spitzer Space Telescope, but they weren’t able to determine whether they were forming a new “family unit”, or whether they were part of an existing cluster. Follow on observations with the Smithsonian’s Submillimeter Array (SMA) let them measure its velocity; the newly discovered clouds are drifting at the same velocity as the rest of the Serpens star-forming cloud.

In the Spitzer image, the newly discovered Serpens South stars are the green, yellow and orange points of light. That black line that runs through the image is actually a dense patch of gas and dust which is currently condensing to form stars. The green areas are hot hydrogen gas. And the wisps of red indicate regions where there are large quantities of organic molecules called polycyclic aromatic hydrocarbons. You might find similar particles on your barbecue grill, or coming out your car’s exhaust pipe.

The discovery was made as part of the Gould’s Belt Survey. This is a study of all the prominent star-forming regions located within 1,600 light-years of Earth. Photographs from Spitzer as well as several other ground-based telescopes will be merged together into a large data set that astronomers can study for years to come.

Original Source:Centre for Astrophysics

August 7, 2007December 26, 2015 by Fraser Cain

Four Galaxies in a Cosmic Collision

Galaxies aren’t born, they evolve, getting built up through a succession of mergers over billions of years. In most cases, this process is slow and steady, with galaxies tearing apart their satellite neighbours and gaining mass. But in one cosmic collision seen by NASA’s Spitzer Space Telescope, 4 extremely massive galaxies are coming together at the same time in a cosmic pileup.

These merging galaxies aren’t small either. No, when this collision is all wrapped up, the remaining monster galaxy will have 10 times the mass of our Milky Way – one of the largest galaxies in the entire Universe. We’ll have a taste of this in about 5 billion years, when the Milky Way merges with Andromeda.

Regular mergers are very common across the Universe; it’s how galaxies grow. But this is different. Bigger, more massive, more destructive. Here’s a cool quote from one of the discovering scientists:

“Most of the galaxy mergers we already knew about are like compact cars crashing together,” said Kenneth Rines of the Harvard-Smithsonian Center for Astrophysics, Cambridge, Mass. “What we have here is like four sand trucks smashing together, flinging sand everywhere.”

It’s inevitable that the most massive galaxies in the Universe will collide and merge too, they’ve just never been seen before.

Galaxy collisions are one of the events that can ignite star formation. The gravitational interaction between galaxies causes clouds of gas and dust to collapse, creating new stellar nurseries. But that won’t happen here. Spitzer didn’t see large quantities of gas, and hot, young star formation; only old stars.

Original Source:NASA News Release

August 6, 2007December 26, 2015 by Fraser Cain

Some Variable Stars Cloak Themselves from View

Most stars shine with a brilliant light, barely changing for billions of years. Others vary in brightness dramatically, dimming and brightening in a period of days, weeks or months. One class, called R Coronae Borealis are erratic in their cycles of brightening and dimming, and now astronomers think they know why: they’re hiding behind a dusty blanket.

An international team of astronomers from France and Brazil has detected a huge cloud of dust around an R Coronae Borealis star called RY Sagittarii, lending evidence to the theory that these stars are actually enshrouding themselves in dust, and hiding from view.

The theory goes that these stars, which can be 50 times larger than our Sun, puff out an envelope of dust around themselves. As this cloud moves into our line of sight from the Earth, it eclipses the star. From our point of view, the star dims in brightness. Then as the solar radiation blasts the dust particles away, the star brightens again.

The researchers used ESO’s Very Large Telescope Interferometer to clearly detect the presence of clouds around a variable star called RY Sagittarii. This was the first time these dust clouds were ever directly detected. The brightest dust cloud was detected several hundred stellar radii away from the centre of the star, so it had clearly drifted away. They discovered that a huge envelope surrounds the star in an area 120 times as big as RY Sagittarii itself.

The cloud is traveling at a speed of 300 km/s, so the astronomers calculated that it was probably ejected about 6 months before it was discovered. They’re planning to perform follow up observations on RY Sagittarii to understand how these dust clouds are formed, and how they dissipate.

Original Source: ESO News Release

August 3, 2007December 26, 2015 by Fraser Cain

Galactic Collisions Set Quasars Ablaze

Some galaxies are relatively quiet, while others blaze with enough radiation that we can see them clear across the Universe. Astronomers now understand that these quasars are formed when the supermassive black holes at the heart of galaxies are actively feeding on material. But where does this material come from?

What sets quasars off?

New research led by two astronomers from the University of Hawaii, Hai Fu and Alan Stockton, seems to give the answer. When you bring a gas-poor galaxy together with a gas-rich galaxy, the cosmic collision feeds fresh hydrogen and helium directly into the maw of the supermassive black hole. Material backs up, then heats up, and then it blazes across the electromagnetic spectrum. Explosions can detonate in the surrounding accretion disk, hurtling back outward again.

Astronomers have suspected this mechanism was happening, but they weren’t sure where this fuel supply of gas was coming from. Using the Hubble Space Telescope and telescopes on Mauna Kea, Hawaii, the researchers analyzed the chemical constituents of material falling into a distant quasar.

They found that this gas was almost pure hydrogen and helium – mostly untouched since the Big Bang. This is much different from the stars and other material in the surrounding giant galaxy which are polluted with heavier elements like carbon and oxygen. The black hole is getting a fresh supply of uncontaminated material.

This difference means that the infalling gas is coming from an external source, probably from another galaxy which is currently in the process of merging. This material comes in, and it also goes out. The tremendous forces and energies involved expel material away from the black hole, helping it travel thousands of light-years away.

Original Source:Institute for Astronomy

August 2, 2007December 26, 2015 by Fraser Cain

The Clear Skies Above Paranal

If you ever wondered why telescopes are perched atop the highest mountains, with the clearest skies, just check out this picture. That’s the night sky above the European Southern Observatory’s Very Large Telescope, located atop Paranal, a 2,600 metre (8,500 foot) mountain in Chile’s Atacama Desert. The photograph was taken by ESO astronomer Yuri Beletsky.

Here’s the cool thing. It’s a single image. The camera was tracking the stars, which is why they look so crisp, while the telescope domes look a little blurry.

The most striking part of the image is, of course, the wide band of stars in the Milky Way. It spans across 100 degrees of the sky. There are two brighter objects in the image as well. The larger, brighter object is Jupiter. You can make out that it has a planetary disk in the photograph. The other is the star Alpha Centauri (one of the closest stars to the Sun).

The beam stretching into the sky is part of the telescope’s adaptive optics system. It creates an artificial star in the sky above the observatory, which a sophisticated computer can use to calculate the amount of atmospheric distortion above the telescope. The telescope’s mirror is then distorted in real time to counteract the effects of the Earth’s atmosphere. It’s like having a space telescope without needing to actually head out into space.

Great picture Yuri!

Here are some past articles about adaptive optics system:

Original Source:ESO news Release