Galaxies Caught in Massive Display of 'Cannibalism'

Stellar streams around the spiral galaxy M63

Astronomers have recently observed a series of large galaxies as they were consuming smaller versions of themselves, in order to increase their bulk and mass.

The fact that galaxies tend to collide and merge with each other is nothing new, and experts have been observing some of these cosmic events for many years.

One of them, the Antennae Galaxies, are even renowned around the world. They were imaged with Hubble a few years back, and have since become the unofficial symbol of galactic mergers.

At this point, astrophysicists believe that even the Milky Way engaged in such behavior in the past, when it started to gobble up smaller, dwarf galaxies in its surroundings.

Traces of those bodies can still be seen today, in the anomalous behavior and number of star clusters located throughout the galaxy, as well as in the properties of the supermassive black hole at its core.

But the new observations show for the first time galactic cannibalism taking place outside of the Milky Way's local neighborhood.

The research group, led by expert David Martinez-Delgado, found that dwarf galaxies appear to be heavily influenced by these collisions, especially as far as their shapes go.

Massive distortions appear, and some of the most common side effects of mergers include the development of tidal tails and tendrils, that completely surround and grasp the larger galaxy.

Martinez-Delgado, who holds a joint appointment at the Max Planck Institute for Astronomy, in Germany, and the Instituto de Astrofísica de Canarias, in the Spanish Canary Islands, also collaborated with amateur astronomers for the research.

The expert says that the recent investigation proved the existence of galactic mergers in galaxies up to 50 million light-years,Space reports.

According to the research team, it would appear that the tidal tails are produced under the incredibly strong gravitational pull that the larger galaxies exert on the near side of smaller ones.

Their appearance is determined by the fact that stars are more distant from the larger galaxy lag behind those who are closer. The latter travel at much higher speeds.

The new scientific research will be published in the October issue of the esteemed Astronomical Journal.

Largest Atlas Of Nuclear Galactic Rings Unveiled

An international team of astrophysicists has just unveiled the most complete atlas of nuclear rings, enormous star-forming ring-shaped regions that circle certain galactic nuclei. The catalogue, published in the Monthly Notices of the Royal Astronomical Society, includes 113 such rings in 107 galaxies.

"AINUR (the Atlas of Images of Nuclear Rings) is the most complete atlas of nuclear rings created to date", Sebastien Comeron, a researcher at the Institute of Astrophysics of the Canary Islands (IAC), and co-author of the joint study with other scientists from the universities of La Laguna, Oulu (Finland) and Alabama (United States), tells SINC.

The atlas has just been published in the journal Monthly Notices of the Royal Astronomical Society, and covers 113 nuclear rings in 107 different galaxies. Six are dust rings in elliptical galaxies, while the rest (the majority) are star-forming rings in disc galaxies.

The nuclear rings are ring-shaped, star-forming configurations located around galactic nuclei. They range in size on average from between 500 to 3,000 light years, and they are very bright because they contain an abundance of young stars, including some extremely massive ones. This kind of star has a short lifetime but shines very brightly before exploding as a supernova.

To find the rings, the astrophysicists used images from around 500 galaxies observed by the Hubble space telescope, which belongs to NASA and the European Space Agency, as well as using other references. The images were processed using filters, generating various kinds of maps to help identify the rings more easily.

Rings and Lindblad resonances
"The AINUR atlas has also looked for relationships between the properties of the nuclear rings and those of the galaxies in which they are found", says Comeron, "and we have been able to statistically prove that most rings are associated with Lindblad resonances (gravitational shoves that push objects out of certain orbits and into others)".

The astrophysicists have shown that when the rings are in a barred galaxy (within disc galaxies, which have a central cylinder or 'cigar' of stars), the maximum radius that a nuclear ring can attain is 25% of the length of the bar, and that the maximum radius is inversely proportional to the strength of the bar.

This is the behaviour that was predicted for the internal Lindblad resonances, which are determined by the size of the bar and their strength (how elliptical this is). If the bar is small or very elliptical, the resonance orbit becomes small, but if it is large or not very elliptical, the orbits become bigger.

The researchers also found that, contrary to what had been believed until now, a significant proportion of nuclear rings are to be found in non-barred galaxies (around 20%). The resonances needed to form the rings in these galaxies "are probably created by strong spiral arms, weak oval distortions of the disc and some lesser interaction with neighbouring galaxies", the scientists say.

LUCIFER Allows Astronomers to Watch Stars Being Born

A new instrument for the world's largest optical telescope, the Large Binocular Telescope on Mount Graham, allows astronomers to observe the faintest and most distant objects in the universe.

Large Binocular Telescope (LBT) partners in the U.S, Germany and Italy announced April 21 that the first of two new innovative near-infrared cameras/spectrographs for the LBT is now available to astronomers for scientific observations at the telescope on Mount Graham in southeastern Arizona.

After more than a decade of design, manufacturing and testing, the new instrument - dubbed LUCIFER 1 - provides a powerful tool to gain spectacular insights into the universe - from the Milky Way to extremely distant galaxies. LUCIFER, built by a consortium of German institutes, will be followed by an identical twin instrument that will be delivered to the telescope in early 2011.

"With the large light-gathering power of the LBT, astronomers are now able to collect the spectral fingerprints of the faintest and most distant objects in the universe," said LBT director Richard Green, a professor of astronomy at the University of Arizona's Steward Observatory.

LUCIFER 1 and its twin are mounted at the focus points of the LBT's two giant 8.4-meter (27.6 foot) diameter telescope mirrors. Each instrument is cooled to -213 degrees Celsius in order to observe in the near-infrared wavelength range.

Near-infrared observations are essential for understanding the formation of stars and planets in our galaxy as well as revealing the secrets of the most distant and very young galaxies.

LUCIFER's innovative design allows astronomers to observe in unprecedented detail, for example star forming regions, which are commonly hidden by dust clouds.

The instrument is remarkably flexible, combining a large field of view with a high resolution. It provides three exchangeable cameras for imaging and spectroscopy in different resolutions according to observational requirements.

Astronomers use spectroscopy to analyze incoming light and answer questions such as how stars and galaxies formed and what they are made of.

Optical Interferometry Gains Popularity

Image comment: The European Southern Observatory's Very Large Telescope, in Chile, is also based on optical interferometry. It features four 8.2-meter aperture, and four 1.8-meter aperture instruments
Image credits: ESO

For more than 50 years, radio astronomy has benefited from the capabilities of a process called interferometry, in gaining some of the sharpest images of the Universe possible with existing technologies. But, in spite of their positive results, astronomers operating these observatories failed to inspire their colleagues working with instruments that looked at the Cosmos in visible light wavelengths. But, now, optical interferometry is beginning to make its way in new optical telescopes, and the results of observations are clearly improving, Nature News reports.

One clear example is the Center for High Angular Resolution Astronomy (CHARA) observatory, which features a Y-shaped array of six one-meter optical telescopes. Each individual component would stand no chance in front of other telescopes on its own, but together, they all act as a single 33-meter mirror. This ability is what allows astronomers at CHARA to boast of producing some of the sharpest images of the Universe ever taken on our planet. This is all possible due to the fact that the Mount Wilson, California-based instrument uses interferometry.

What this means is that the light captured by each of the six telescopes is not analyzed and processed independently. Rather, underground tunnels carry the signals to a central hub, where they are joined together in a single beam. This allows for the entire array to behave like a single, large mirror, which would be unfeasible to build in real-life. Additionally, interferometry carries the advantage of offering a slight 3D perspective as well, given that all individual components in the array snap their images from different vantage points. This is the basis that allows for the images to be combined seamlessly into a larger, more clear photograph.

By using interferometry, CHARA is able to boast a resolving power about 50 times better than that of the orbit-based Hubble Space Telescope. The ground-based observatory can image relatively small details on the surface of distant stars, for example, which are only apparent in images from other telescopes as diffuse blobs of light. “This is moving us into a realm that radio astronomy has been able to enjoy for decades,” University of Denver in Colorado astronomer Robert Stencel explains. He is the coauthor of a new study, detailing data that CHARA collected of a distant binary system that puzzled astronomers for about a decade.

Scientists capture 'terrifying' Tolkien-like eclipse (w/ Video)

Scientists have captured a 'terrifying' image of a giant Goliath-like star undergoing a two year eclipse. First discovered by a German astronomer 180 years ago, it is the first close-up image of an eclipse beyond the solar system to be captured on camera by scientists.

Astronomers at the University of St Andrews, who collaborated in the international study, describe the find as a ‘terrifying image... like something from a Tolkien book’.

St Andrews physicists Ettore Pedretti and Nathalie Thureau are members of an international team led by Brian Kloppenborg at the University of Denver. The group combined the light of four telescopes more than 300 metres apart to capture a magnified image of the giant star undergoing a ‘stellar eclipse’.

The star, Epsilon Aurigae, is the fifth brightest star in the constellation Auriga, which is known as ‘the charioteer’. Every 27 years Epsilon Aurigae becomes two to three times dimmer, with the dimmed light lasting about two years. The phenomenon was first observed in 1821 by the German astronomer Johann Fritsch.

Using an instrument created at the University of Michigan, astronomers have for the first time imaged a peculiar binary star eclipse that happens once every 27 years.

The resulting image, roughly 140 times sharper than those provided by the Hubble Space Telescope, provides new insights into the distant stellar system, even though the effect of the eclipse is so big that the star almost disappears from view.

Dr Pedretti said, "From the image, we can confirm that the eclipse of Epsilon Aurigae is caused by a thin disc of opaque dust trailed by a massive and unseen companion. Like David, tiny particles of dust are able to kill the light of this ‘Goliath’ star.

“It resembles an image from a book by J.R.R. Tolkien. It is like seeing the vessel of the sun, guided by the Maya Arien, being swallowed by the dragon Smaug and plunging Middle Earth in a second-age of darkness. It is a terrifying image".

The innovative light-combining technique used to view the star is called optical interferometry. Dr Pedretti built the infrared camera used to take superfast ‘snapshots' of the combined light of four telescopes. It has to be very fast in order to 'freeze' the image against the turbulent atmosphere.

Dr Thureau was responsible for the design of some critical optics that combine the light from the four telescopes. She commented, "With this image we have solved an 180 year old mystery. Astronomers have been puzzled for more than a century about this star and we took two pictures that may finally solve the mystery. In fact we will continue to capture images since the eclipse lasts about two years.”

Dr Pedretti and Dr Thureau aim to form the first group in Scotland which will build instruments for optical and infrared interferometry, exploting their high-resolution images.

"Our aim is to exploit existing interferometers around the world in order to take detailed pictures of distant and interesting astronomical objects that are not achievable even with the largest single telescopes," explained Dr Pedretti.

The research, which involved the Universities of St Andrews, Denver, Georgia State and Michigan, is published in this week's issue of Nature.

More information: The paper is called "Infrared images of the transiting disk in the epsilon Aurigae System."

Source:- University of St Andrews/ PhysOrg.com