This Week’s “Where In the Universe?” Challenge

Have you seen this image before? You know you have. It’s probably right on the tip of your tongue. This is the image for this week’s “Where In The Universe?” challenge. The goal of this challenge is to test your skills and visual knowledge of our universe. Guess the name of this image, and give yourself extra points if you can guess the telescope or project that this image came from (is that a clue? It’s not from a spacecraft…). As always, don’t peek below before you make your guess. Comments on how you did are welcome.

A highly scientific illustration of the Voorwerp.  Courtesy Galaxy Zoo
A highly scientific illustration of the Voorwerp. Courtesy Galaxy Zoo

This image is of “Hanny’s Voorwerp” from the Galaxy Zoo project, which in turn, is part of the Sloan Digital Sky Survey, which uses a 2.5-meter telescope on Apache Point, NM, to scan the sky. ‘Voorwerp’ is Dutch for ‘object’, and ‘Hanny’ refers to Hanny van Arkel, a Dutch school teacher. The voorwerp is the blue blob just below the big galaxy. Hanny found the object as she was classifying galaxies from astronomical images as part Galaxy Zoo’s “citizen science” project, where volunteers classify galaxies as spiral or eliptical. As for what the blob is, no one knows for sure. Yet.

Other spectral images show the blob as green, which is probably closer to how our eyes would actually see it if we were close enough. It’s about 700 million light years from Earth and the Voorwerp itself is about 65,000 light years across.

Hanny’s Voorwerp has been of interest to lots of folks, and an astronomer at the William Herschel telescope at La Palma took a spectrum of the Voorwerp, in an effort to help figure out what it is. The spectrum showed that the Voorwerp is at the same distance as the big galaxy. This implies that it’s really big and luminous.

The the best explanation might be that the Voorwerp got its energy from light that was once emitted by a bright quasar. The big galaxy, called IC 2497 is thought to have once hosted the quasar that lit up Hanny’s Voorwerp.

From the Galaxy Zoo Blog: “What is the Voorwerp? That’s not too clear yet. We have to properly analyse the spectrum to understand what exactly is going on. It’s likely forming stars at a huge rate, ionising lots of gas and making it shine. We’re also trying to get a deeper image to see if there’s evidence of an interaction between the big galaxy and the Voorwerp.”

If you’re not familiar with Galaxy Zoo, check it out. It’s a lot of fun. If you’re good at this challenge, you’d be a great help over at Galaxy Zoo. And who knows? Maybe you could find the next unusual object!

Cassini To Buzz Enceladus Oct. 9

Enceladus flyby. Artwork courtesy Karl Kofoed.

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The Cassini spacecraft will make two close passes of Saturn’s geyser-spewing moon Enceladus this month. The first one on October 9 is the closest flyby yet of any moon of Saturn, at a white-knuckle distance of only 25 kilometers (16 miles) from the surface. The not-quite-as-scary Halloween flyby on Oct. 31 will be farther out, at 196 kilometers (122 miles). The focus of the Oct. 9 is the plume of the moon’s geyser, and the spacecraft’s fields and particles instruments will venture deeper into the plume than ever before, directly sampling the particles and gases. Scientists are intrigued by the possibility that liquid water, perhaps even an ocean, may exist beneath the surface of Enceladus. Trace amounts of organics have also been detected, raising tantalizing possibilities about the moon’s habitability.

While Cassini’s cameras and other optical instruments were the focus of an earlier flyby in August, this time the emphasis will be on the composition of the plume rather than imaging the surface.

“We know that Enceladus produces a few hundred kilograms per second of gas and dust and that this material is mainly water vapor and water ice,” said Tamas Gambosi, Cassini scientist at the University of Michigan, Ann Arbor. “The water vapor and the evaporation from the ice grains contribute most of the mass found in Saturn’s magnetosphere.

“One of the overarching scientific puzzles we are trying to understand is what happens to the gas and dust released from Enceladus, including how some of the gas is transformed to ionized plasma and is disseminated throughout the magnetosphere,” said Gambosi.

The Oct. 9 flyby will be only 25 kilometers (16 miles) from the surface. The Oct. 31 flyby is farther out, at 196 kilometers (122 miles).   Credit: NASA/JPL
The Oct. 9 flyby will be only 25 kilometers (16 miles) from the surface. The Oct. 31 flyby is farther out, at 196 kilometers (122 miles). Credit: NASA/JPL

On Oct. 31, the cameras and other optical remote sensing instruments will be front and center, imaging the fractures that slash across the moon’s south polar region like stripes on a tiger.

These two flybys might augment findings from the most recent Enceladus flyby, which hint at possible changes associated with the icy moon. Cassini’s Aug. 11 encounter with Enceladus showed temperatures over one of the tiger-stripe fractures were lower than those measured in earlier flybys. The fracture, called Damascus Sulcus, was about 160 to 167 Kelvin (minus 171 to minus 159 degrees Fahrenheit), below the 180 Kelvin (minus 136 degrees Fahrenheit) reported from a flyby in March of this year.

“We don’t know yet if this is due to a real cooling of this tiger stripe, or to the fact that we were looking much closer, at a relatively small area, and might have missed the warmest spot,” said John Spencer, Cassini scientist on the composite infrared spectrometer, at the Southwest Research Institute, Boulder, Colo.

Results from Cassini’s magnetometer instrument during the August flyby suggest a difference in the intensity of the plume compared to earlier encounters. Information from the next two flybys will help scientists understand these observations.

Four more Enceladus flybys are planned in the next two years, bringing the total number to seven during Cassini’s extended mission, called the Cassini Equinox Mission.
The Enceladus geysers were discovered by Cassini in 2005. Since then, scientists have been intrigued about what powers them, because the moon is so tiny, roughly the width of Arizona at only 500 kilometers (310 miles) in diameter.

Source: Cassini Press Release

‘Cosmic Eye’ Helps Focus on Distant Galaxy’s Formation

Cosmic Eye. Credit: Hubble Space Telescope

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Using gravitational lensing, astronomers have been able to see a young star-forming galaxy in the distant universe as it appeared only two billion years after the Big Bang. Appropriately enough, the galaxy used as a zoom lens was the “Cosmic Eye” galaxy, named so because through the effect of gravitational lensing, it looks like a giant eye in space. The researchers, led by Dr. Dan Stark, of Caltech, say this distant galaxy may provide insights into how our own galaxy may have evolved to its present state.

The astronomers used the ten meter Keck telescope in Hawaii, which is equipped with a laser-assisted guide star adaptive optics (AO) to correct for blurring in the Earth’s atmosphere. By combining the powerful telescope with the magnifying effect of the gravitational field of the foreground galaxy – called gravitational lensing – they were able to study the distant star system, which lies 11 billion light years from Earth. The Cosmic Eye, the foreground galaxy, is 2.2 billion light years from Earth.

The distortion of light rays enlarged the distant galaxy eight times.

This allowed the scientists to determine the galaxy’s internal velocity structure and compare it to later star systems such as the Milky Way.

In the image, the red source in the middle is the foreground lensing galaxy, while the blue ring is the near-complete ring image of the background star-forming galaxy.

Watch a movie of the gravitational lensing view.

Research co-author Dr. Mark Swinbank, in The Institute for Computational Cosmology, at Durham University, said, “This is the most detailed study there has been of an early galaxy. Effectively we are looking back in time to when the Universe was in its very early stages.

Stark said, “Gravity has effectively provided us with an additional zoom lens, enabling us to study this distant galaxy on scales approaching only a few hundred light years.

“This is ten times finer sampling than previously. As a result for the first time we can see that a typical-sized young galaxy is spinning and slowly evolving into a spiral galaxy much like our own Milky Way.”

Data from the Keck Observatory was combined with millimeter observations from the Plateau de Bure Interferometer, in the French Alps, which is sensitive to the distribution of cold gas destined to collapse to form stars.

Dr. Swinbank added, “Remarkably the cold gas traced by our millimetre observations shares the rotation shown by the young stars in the Keck observations.

“The distribution of gas seen with our amazing resolution indicates we are witnessing the gradual build up of a spiral disk with a central nuclear component.”

These observations has astronomers looking forward to the capabilities of the European Extremely Large Telescope (E -ELT) and the American Thirty Metre Telescope (TMT), which are being built and will be available in about 10 years.

Source: Durham University

Of Overhead Projectors and Planetarium Foolishness

Overhead projector. Courtesy Alibaba.com

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We don’t normally publish political articles here on Universe Today, but I’m going to make an exception here after watching last night’s presidential debate because a.) John McCain mentioned something about a planetarium, which is an area of interest for UT readers, and b.) McCain obviously had no idea what he was talking about. McCain, the Republican presidential nominee pointed out how Barack Obama, the Democratic nominee, has voted for almost a billion dollars of “pork barrel” projects (money for specific pet projects in their districts) and said, “He (Obama) voted for … $3 million for an overhead projector at a planetarium in Chicago, Illinois.”

First of all, there’s a big difference between an overhead projector and a planetarium projection system. Spacewriter’s Ramblings has a great explanation and pictorial description, if you have questions.

Second, if you want to be nitpicky, while Obama requested the funding, he never voted on it.

Obviously, McCain thinks this is a big issue, since this is at least the second time he’s mentioned Obama and planetariums. A few weeks ago he said that Obama has sought money for “planetariums and other foolishness.”

Foolishness! Over 110 million people around the world visit planetariums every year! They are important learning and teaching tools that encourage a science-literate population, and have inspired young people to become astronomers and astronauts, and aspire to many other science-related occupations as well.
Children enjoy the stars and planets at the Morehead Planetarium in Chapel Hill, North Carolina.

Davin Flateau says it much better than I can on his great post at his Perfect Silence blog.

Obama’s website has a list of his federal funding requests for Fiscal Year 2008, and clearly listed is “Adler Planetarium, to support replacement of its projector and related equipment, $3,000,000,” with a description that says the 40 year old projection equipment has begun to fail and since parts are no longer available, soon students and other museum-goers will be left “without this very valuable and exciting learning experience.” I don’t see that as “pork barrel” funding, but an attempt to maintain a long-standing (Adler opened in 1930) and important institution in his district.

And don’t get me going on Sarah Palin.

Will the Mars Science Laboratory Be Cut?

Mars Science Laboratory. Credit: NASA/JPL

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The Mars Science Laboratory, a souped-up Mars rover scheduled to launch next year might be delayed, scaled down or canceled due to technical problems and cost overruns. The nuclear powered rover designed to search for microbial life on the Red Planet, has already cost $1.5 billion and if it reaches a 30-percent cost overrun, it could be cancelled by Congress. Aviation Week reports that officials from the agency’s Mars Exploration Program (MEP) and the Jet Propulsion Laboratory (JPL) will brief NASA Administrator Mike Griffin and Science Associate Administrator Ed Weiler this Friday and attempt to work out a potential solution. Delaying the rover’s mission until 2011 would be costly, but Weiler has said that JPL is so stretched trying to make the 2009 launch window that the result could be “a nuclear crater on Mars.”

Nearly the size of a small car, the proposed MSL will be three times as heavy and twice the width of the Mars Exploration Rovers (MERs) that landed in 2004, and will be able to travel twice as far. It will carry ten advanced scientific instruments and cameras. It will make the first precise landing and a predetermined site, using a guided entry system and a soft-landing system called the Sky Crane. But assembly and testing of critical components and instruments are behind schedule because of technical problems.

Entry, descent and landing for MSL.  Credit:  JPL
Entry, descent and landing for MSL. Credit: JPL

Since there’s not much extra cash anywhere in NASA and JPL’s pot, any cost overruns from technical issues or delays would have to be taken from other missions. To keep MSL, NASA could be forced to cancel the $485 million 2013 atmospheric Scout mission MAVEN that was recently announced, or a future rover mission tentatively set for 2016.

A slip to the 2011 launch window will add another $300 million-$400 million to the price tag, but it could be better than trying to launch in 2009 with a rover and team that is potentially unready to fly.

Doug McCuistion, the MEP manager said his program is stretched to its limits, with no funding for technology development and “next to nothing” for education and public outreach.

NASA has been sending a mission to Mars approximately every two years to determine if the planet ever was capable of supporting life.

Sources: Aviation Week, MSNBC

Watch Out! Galactic Collisions Could Snuff Out Star Formation

Galactic Collisions. Credit: Tomer Tal and Jeffrey Kenney/Yale University and NOAO/AURA/NSF

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It’s a violent universe out there! Yesterday we ran an article about galaxies colliding and forming fireballs. Today, there’s more evidence for galactic collisions, and it’s not good news for potential stars. While this image is stunning, such collisions could spell doom for future star formation. A deep new image of the Virgo cluster has revealed huge tendrils of ionized hydrogen gas 400,000 light-years long connecting the elliptical galaxy M86 and the disturbed spiral galaxy NGC 4438. This image, taken by the 4-meter telescope at Kitt Peak National Observatory, provides striking evidence of a previously unsuspected high-speed collision between the two galaxies. “Our data show that this system represents the nearest recent collision between a large elliptical galaxy and a large spiral,” said Jeffrey Kenney of Yale University, “This discovery provides some of the clearest evidence yet for high-speed collisions between large galaxies, and it suggests that the consequences of such collisions are a plausible alternative to black holes in trying to explain the mystery of what process turns off star formation in the biggest galaxies.”

Astronomers have been trying to understand the mystery of what causes the biggest galaxies in the Universe—which are primarily ellipticals, like M86—to stop forming stars. “Something needs to heat up the gas so it doesn’t cool and form stars,” Kenney says. “A number of recent studies suggest that energy from active galactic nuclei associated with supermassive black holes may do this, (see Universe Today articles here and here) but our new study shows that gravitational interactions may also do the trick.”

The Virgo cluster is located approximately 50 million light-years from Earth. Previous studies had noticed disturbed H-alpha gas around each of the two galaxies, but scientists didn’t think the two had a connection. Indeed, some results have suggested that NGC 4438 collided with the small lenticular galaxy NGC 4435, but NGC 4435 has a much higher line-of-sight velocity as seen from Earth and appears undisturbed.

Spectroscopy of selected regions along the filament between M86 and NGC 4438 shows a fairly smooth velocity gradient between the galaxies, supporting the collision scenario. And here’s the kicker: there are no obvious stars in the filaments.

As in most elliptical galaxies, most of the gas within M86 is extremely hot, and therefore radiates X-rays. The X-ray distribution in M86 is irregular and sports a long plume, which had previously been interpreted as a tail of gas which is being stripped by ram pressure as M86 falls into the intracluster medium of the Virgo cluster. The new H-alpha image from Kitt Peak suggests that most of the disturbances to the interstellar medium in M86 are instead due to the collision with NGC 4438.

Low-velocity collisions, especially between small- to medium-sized galaxies, often cause an increase in the local star formation rate, as the collisions tend to cause gas to concentrate in the galaxy centers. But in high velocity collisions (which happen naturally between large galaxies, since their large gravity pulls mass inward much faster), the kinetic energy of the collision can cause the gas to heat up so much that it cannot easily cool and form stars.

While not many galaxies suffer such extreme collisions as M86, most galaxies experience minor mergers and gas accretion events, and these may play a significant role in heating the galaxy’s gas. These more common but modest events are very hard to study, since their observational signatures are weak.

“The same physical processes occur in both strong and weak encounters, and by studying the observable effects in extreme cases like M86 we can learn about the role of gravity in the heating of galaxy gas, which appears to be quite significant,” Kenney adds.

Kenney is the lead author of a paper to be published in a November 2009 issue of Astrophysical Journal Letters.

Source: NOAO

Ozone Hole Bigger Again

Ozone hole during 7 October 2008 as measured by the Scanning Imaging Absorption Spectrometer for Atmospheric Cartography (SCIAMACHY) atmospheric sensor onboard ESA’s Envisat. Credits: KNMI/ESA

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Is the ozone hole was recovering? Maybe not. The protective atmospheric layer of ozone around our planet has been thinning over Antarctica for many years. New satellite data indicates the 2008 ozone hole is larger both in size and ozone loss than 2007 but is not as large as the record year of 2006. This year the area of the thinned ozone layer over the South Pole reached about 27 million square kilometers, compared to 25 million square kilometers in 2007 and a record ozone hole extension of 29 million square kilometers in 2006, which is about the size of the North American continent. Ozone is a protective atmospheric layer found about 25 kilometers in altitude that acts as a sunlight filter, shielding life on Earth from harmful ultraviolet rays. A thinner ozone layer can increase the risk of skin cancer and cataracts and harm marine life. What causes the ozone layer to change from year to year, and if CFC’s have been banned, why isn’t the ozone recovering?

The depletion of ozone is caused by extreme cold temperatures at high altitude and the presence of ozone-destructing gases in the atmosphere such as chlorine and bromine. Most of these gases originate from man-made products like chlorofluorocarbons (CFCs), which were phased out under the 1987 Montreal Protocol. But they continue to linger in the atmosphere.

Depending on the weather conditions, the size the Antarctic ozone hole varies every year. As the polar spring arrives in September or October, the combination of returning sunlight and the presence of so-called stratospheric clouds (PSCs) over the Antarctic leads to a release of highly ozone-reactive chlorine radicals present in the atmosphere that break ozone down into individual oxygen molecules. A single molecule of chlorine has the potential to break down thousands of molecules of ozone.

Chlorine activation and ozone hole extension early September 2007 and 2008.   Credits: DLR
Chlorine activation and ozone hole extension early September 2007 and 2008. Credits: DLR

Colder temperatures in the stratosphere over Antarctica, combined with a high formation rate of PSCs caused more lingering chlorine radicals to be released, making the current hole one of the largest. 2006 saw the largest hole. A unit of measurement called a Dobson Unit describes the thickness of the ozone layer, and this year (2008) about 120 Dobson Units were observed compared to around 100 Dobson Units in 2006.

The analysis is based upon the Scanning Imaging Absorption Spectrometer for Atmospheric Cartography (SCIAMACHY) atmospheric sensor onboard ESA’s Envisat, the Global Ozone Monitoring Experiment (GOME) aboard ESA’s ERS-2 and its follow-on instrument GOME-2 aboard EUMETSAT’s MetOp.

Source: ESA

A Different Side of Mercury

A different side of Mercury. Credit: NASA/Johns Hopkins University Applied Physics Laboratory/Carnegie Institution of Washington

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Here’s the first image from MESSENGER’s flyby of Mercury on Monday. The bright crater just south of the center of the image is Kuiper, which has been seen before on images from the Mariner 10 mission in the 1970s. But most of this image, to the east, or right of Kuiper, toward the limb of Mercury is new territory for human eyes – at least in optical views. The image was taken by the Wide Angle Camera as MESSENGER was departing from the planet, and are among the first spacecraft views of that portion of Mercury’s surface. Most striking are the large pattern of rays that extend from north to south, almost along the entire face of Mercury. Amazing! This extensive ray system appears to emanate from a relatively young crater newly imaged by MESSENGER, providing a view of the planet distinctly unique from that obtained during MESSENGER’s first flyby.

2nd Update: (9:40 am CDT) More images!

Update: (8:50 am CDT) See 2nd image released below:


Mercury's limb.  Credit: NASA/Johns Hopkins University Applied Physics Laboratory/Carnegie Institution of Washington
Mercury's limb. Credit: NASA/Johns Hopkins University Applied Physics Laboratory/Carnegie Institution of Washington

Above is the 3rd image released from the second flyby, a spectacular close-up of Mercury, as seen by the MESSENGER as it approached the planet, at about 17,100 kilometers (10,600 miles) altitude. The features in the foreground, near the right side of the image, are close to the terminator, the line between the sunlit dayside and dark night side of the planet, so shadows are long and prominent. The MESSENGER team has only had a few hours to examine these intriguing features, and, currently, more images from the flyby are still streaming back to Earth.

Mercury close up. Credit: NASA/Johns Hopkins University Applied Physics Laboratory/Carnegie Institution of Washington
Mercury close up. Credit: NASA/Johns Hopkins University Applied Physics Laboratory/Carnegie Institution of Washington

Here’s the second image released from the flyby. This is a close-up image taken 9 minutes and 14 seconds after MESSENGER’s closest approach to Mercury, when the spacecraft was moving at 6.1 kilometers/second (3.8 miles/second). The largest impact feature at the top of the image is about 133 kilometers (83 miles) in diameter and is named Polygnotus. This area was imaged previously by Mariner 10.

More on the first image: Data from the flyby started coming back to Earth early this morning, at about 1:50 am EDT. This spectacular image is one of the first to be returned and was taken about 90 minutes after the spacecraft’s closest approach to Mercury. This young, extensively rayed crater, along with the prominent rayed crater to the southeast of Kuiper, near the limb of the planet, were both seen in Earth-based radar images of Mercury but not previously imaged by spacecraft. As the MESSENGER team is busy examining this newly obtained view that is only a few hours old, data from the flyby continue to stream down to Earth, including higher resolution close-up images of this previously unseen terrain.

MESSENGER completed the flyby on Oct. 6 at 4:40 am EDT.

We’ll add more images as they become available.

Source: MESSENGER Gallery

Extracting Water From the Moon With Basic Home Appliances

Two scientists have cooked up a way to get water and oxygen from the moon. And to test their idea, they used a basic kitchen microwave oven. “This is exploration,” said Dr. Bill Kaukler of the University of Alabama in Huntsville’s Center for Materials Research. Kaukler and Dr. Ed Etheridge of Marshall Space Flight Center have proposed using microwaves to draw water from below the lunar surface. To do this, microwaves would be “shot” at the moon, likely from an orbiting spacecraft. But to test their theory, Kaukler and Etheridge didn’t build an elaborate test site. They just put a plate of simulated lunar regolith in a microwave oven and “nuked” it for a few minutes.

Kaukler said they were inspired by the results of 1994’s Clementine mission which uncovered the possible existence of ice within some of the craters at the moon’s poles. This discovery was confirmed in early 1998 by NASA’s lunar prospector. Scientists believe the ice was brought to the moon the same way water was brought to Earth – by comets crashing into the surface.

“If you estimate, there would be billions of tons of water,” Ethridge said.

The surface is covered by regolith, or silicate rock that is the lunar version of top soil. It’s about two meters deep “and where you have silicates, you have oxygen,” said Kaukler. “That makes it worthwhile to extract, and, one of the beauties of this is we don’t have to dig.”

Digging could stir up the fine, gritty dust. The microscopic particles then could adversely affect the astronauts’ spacesuits and their equipment, he said.

To get to the water, microwaves would be shot into the regolith, “thawing” the ice to about minus-50 degrees Celsius. Water vapor would be drawn to the surface by the moon’s vacuum environment. The water vapor is then collected on a plate as ice and scraped off to be used as water for the astronauts. The hydrogen and oxygen can also be separated through electrolysis to use as fuel for a trip to Mars.

In their Marshall lab, the scientists used a microwave oven, a vacuum, water and a simulant to regolith to verify their findings.

“We put some water in the simulant and placed it inside the microwave,” Kaukler said. “Then, we used the vacuum to replicate the lunar atmosphere.

“We were able to get about 95 percent of the water back in about two minutes.”

Other uses of microwaves would be to “melt” the lunar surface. The process would help create dust-free landing and launch sites as well as smoother floors for structures and roads for traveling without kicking up dust.

“For surface site preparation, the microwaves would melt the top layer, glazing it, so it’s not all dust,” Ethridge said. “It would create a cobblestone effect.”

So if the moon had water, oxygen and useable real estate, it might be a financially viable place to colonize.

“Since we’re planning to go to the moon and Mars, the idea is to save weight (on the flight) and to extract the materials the astronauts would need – oxygen and water,” said Kaukler. “There have been studies that showed (getting the water) to be economically viable,” he said. “It could be the first commercial venture.”

Source: Huntsville Alabama Times

Galaxy Ramming Through Space Creates Fireballs

Fireball Galaxy. Credit: Subaru Telescope, National Astronomical Observatory of Japan (NAOJ)

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During routine observations of the Coma Cluster of galaxies using the Subaru Telescope in Hawaii, astronomers discovered a thread-like structure stretching from one of the galaxies. The astronomers determined this filament was about 260 thousand light years long, and spectral analysis of the filament suggested a younger age toward the outer edge of the filament. The filament also has many young stars surrounded by ionized gas that look like projectiles flying out from the galaxy. So what happened in this chaotic area of space? Astronomers determined a speeding galaxy rammed into the Coma Cluster, stripping gas from the galaxy and creating fireball-like projectiles.

Galaxies evolve over time, and astronomers do not yet understanding how they change in shape, size, and color. Galaxy Clusters, which are dense populations of galaxies, rich with hot intergalactic gas, accompanied by strong gravitational forces are some of the best locations to observe galactic evolution.

A team of researchers from the National Astronomical Observatory of Japan and the University of Tokyo used Suprime-cam on the Subaru Telescope to observe the Coma Cluster of galaxies. The Coma Cluster contains over 1,000 galaxies and is fairly close to Earth at about 300 million light years away.
During observations in 2006 and 2007, the astronomers saw the filament extending from Galaxy RB199 and several of the “fireballs.” Detailed study identified several bright knots connected by blue filamentary structures, and the knots are actually the clusters of young stars weighing 10 million times our Sun, contained in an area about 3000 to 6000 light years across. Because the knots are accompanied by ionized gas, active star formation is going on in the fireballs where usually far less star formation would be expected. The team noted that the size and the mass of the fireballs indicate they could develop into dwarf galaxies.

Closeups of four fireballs.  Subaru Telescope, National Astronomical Observatory of Japan (NAOJ)
Closeups of four fireballs. Subaru Telescope, National Astronomical Observatory of Japan (NAOJ)

Because the inside of the cluster is crowded with galaxies, they pass by each other and crash into each other. The team thought that the tidal forces during such encounters could strip gas or stars from the galaxies. They also postulated that as a galaxy falls into the center of the cluster the gravitational forces of the cluster could remove the gas and stars from that galaxy. Both scenarios are possible, however, the research team found that these mechanisms could hardly explain the characteristics of the fireballs. The team then realized that ram pressure stripping occurs when superheated gas (several tens of million Kelvin) in the cluster and the galaxies collide at high speeds. Previous X-ray observation shows the presence of large amounts of hot ionized gas in the middle of the Coma Cluster while RB199 crashes into the center at a speed of 1200 miles per second, causing strong friction with this hot gas. As such, the team concluded that the ram pressure has enough power to strip the gas from the galaxy AND create the fireballs.

While there are several reports indicating ram pressure stripping in nearby galaxy clusters, the identification of fireballs in this study is the first to demonstrate the stripped gas turns into stars while traveling through remote space far away from its source. Similar phenomena have been observed in galaxy clusters much further away at several billions light years, however, those distant cases were interpreted through witnessing the transitional phase of galaxies changing their morphology or colors as they fall into a cluster. The fireballs discovered by this team of Japanese astronomers provide the first sample of such structures in a nearby cluster. Principal investigator, Dr. Michitoshi Yoshida, said “the team is confident that our study of these phenomena leads to a better understanding of the gas stripping processes in galaxy clusters, and the effect of clusters on the evolution of individual galaxies”.

Source: Subaru Press release