Superfast Star Shot Out of Milky Way

A super-hot blue star hurtling through space has been shot completely out of the Milky Way, new Hubble Space Telescope photos reveal.

The star is streaking across space at a blistering speed of 1.6 million mph (2.5 million kph) – three times faster than our sun's orbital velocity in the Milky Way. Hubble observations confirm that the stellar speedster hails from the Milky Way's core, settling some confusion over where it originally called home.Astronomers think the star is a survivor from a triple-star system that traveled through the bustling center of our Milky Way galaxy 100 million years ago, but made the perilous mistake of wandering too close to the galaxy's giant black hole, which captured one of the stars and flung the other two out of the Milky Way. The two ejected stars then merged to form a super-hot, blue star.

While it may seem a little farfetched, astronomers using NASA'sHubble Space Telescope say it is the most likely scenario for the so-called hypervelocity star, known as HE 0437-5439, one of the fastest ever detected.

"Using Hubble, we can for the first time trace back to where the star comes from by measuring the star's direction of motion on the sky," said astronomer Warren Brown of the Harvard-Smithsonian Center for Astrophysics in Cambridge, Mass., lead author of the study and a member of the Hubble team that observed the star. "Its motion points directly from the Milky Way center. These exiled stars are rare in the Milky Way's population of 100 billion stars. For every 100 million stars in the galaxy lurks one hypervelocity star."

Since the first discovery in 2005, astronomers have found 16 hypervelocity stars, most of which are thought to be exiles from the heart of our galaxy. But, the new Hubble result is the first direct observation that links a high-flying star to a galactic center origin.

What this tells us

The movements of these breakneck stars could reveal the shape of thedark matter distribution surrounding our galaxy.

"Studying these stars could provide more clues about the nature of some of the universe's unseen mass, and it could help astronomers better understand how galaxies form," said Oleg Gnedin of the University of Michigan in Ann Arbor. "Dark matter's gravitational pull is measured by the shape of the hyperfast stars' trajectories out of the Milky Way."

The HE 0437-5439 stellar outcast is already trekking deep in the Milky Way's distant outskirts, high above the galaxy's disk, about 200,000 light-years from the center. By comparison, the diameter of the Milky Way's disk is approximately 100,000 light-years.

Astronomers used Hubble data to measure the runaway star's direction of motion and determine the Milky Way's core as its starting point. Brown and Gnedin's team then calculated how fast the star had to have been ejected in order to reach its current location.

"The star is traveling at an absurd velocity, twice as much as the star needs to escape the galaxy's gravitational field," said Brown, who discovered the first unbound, hypervelocity star in 2005. "There is no star that travels that quickly under normal circumstances – something exotic has to happen."

But wait, there's more

After studying the star, researchers noticed that some of the calculations did not seem to add up.

Based on the speed and position of HE 0437-5439, the star would have to be 100 million years old to have journeyed such a distance from the Milky Way's core. Yet its mass – nine times that of our sun – and blue color mean that it should have burned out after only 20 million years – far shorter than the transit time it took to get to its current location.

The most likely explanation for the star's blue color and extreme speed is that it was part of a triple-star system that was involved in an ill-fated encounter with the Milky Way's monster black hole.

This concept for imparting an escape velocity on stars was first proposed in 1988. The theory predicted that the Milky Way's black hole should eject a star about once every 100,000 years.

Brown suggests that the triple-star system contained a pair of closely orbiting stars and a third outer member that was also gravitationally tied to the group. The close encounter enabled the black hole to wrench the outer star away from the tight binary system.

The doomed star's momentum was then transferred to the stellar twosome, boosting the duo to escape velocity from the galaxy. As the pair rocketed away, they carried on with normal stellar evolution.

The more massive companion star evolved more quickly, puffing up to become a red giant and enveloping its partner in the process. The two stars spiraled together, merging into one superstar – a blue straggler.

"While the blue straggler story may seem odd, you do see them in the Milky Way, and most stars are in multiple systems," Brown said.

The mysterious blue straggler

This vagabond star has puzzled astronomers since its discovery in 2005 by the Hamburg/European Southern Observatory sky survey.

Astronomers had proposed two possibilities to solve the age problem. The star either defied the normal aging process by becoming a blue straggler, or it was flung out of the Large Magellanic Cloud, a neighboring galaxy.

In 2008, a team of astronomers thought they had solved the mystery. They found a match between the exiled star's chemical makeup and the characteristics of other stars in the Large Magellanic Cloud.

The rogue star's position is also close to the neighboring galaxy – only 65,000 light-years away. The new Hubble result now settles the debate over the star's birthplace.

Astronomers using the sharp vision of Hubble's Advanced Camera for Surveys were able to make two separate observations of the wayward star 3 1/2 years apart. Team member Jay Anderson of the Space Telescope Science Institute in Baltimore, Md., developed a technique that measures the star's position relative to each of 11 distant background galaxies, which form a frame of reference.

Anderson then compared the star's position in images taken in 2006 with those taken in 2009 in order to calculate how far the star moved in relation to the background galaxies. The star appeared to move, but only by 0.04 of a pixel (picture element) against the background.

"Hubble excels with this type of measurement," said Anderson. "This observation would be challenging to do from the ground."

The team is now trying to determine the homes of four other unbound stars, all located on the fringes of the Milky Way galaxy.

"We are targeting massive 'B' stars, like HE 0437-5439," said Brown, who has discovered 14 of the 16 known hypervelocity stars. "These stars shouldn't live long enough to reach the distant outskirts of the Milky Way, so we shouldn't expect to find them there. The density of stars in the outer region is much less than in the core, so we have a better chance to find these unusual objects."

Sourced Space.com.

There are an estimated 50 thousand million galaxies in the universe, with the typical galaxy containing 50 thousand million to 100 thousand million stars. It is estimated that there are 10²² stars in total in the universe.

Recipe for a Universe

Take a massive explosion to create plenty of stardust and a raging heat. Simmer for an eternity in a background of cosmic microwaves. Let the ingredients congeal and leave to cool and serve cold with cultures of tiny organisms 13.7 billion years later.

To understand the basic ingredients and the ‘cooking conditions’ of the cosmos, from the beginning of time to the present day, particle physicists have to try and reverse-engineer the ‘dish’ of the Universe. Within the complex concoction, cryptic clues hide the instructions for the cosmic recipe.

Giant Cannibal Galaxy's Last Meal

New images show the "last meal" of a giant cannibal galaxy as it gobbles down a smaller spiral galaxy, which has been twisted and warped from being devoured.

The giant galaxy, Centaurus A (NGC 5128) is the nearest giant, elliptical galaxy, at a distance of about 11 million light-years. The galaxy hosts a supermassive black hole that is 200 million times the mass of the sun, or 50 times the mass of the black hole at the center of the Milky Way.

At the galaxy's center is an opaque dust lane that is thought to be the remains of acosmic merger between the galaxy and a smaller spiral galaxy full of dust.

Between 200 and 700 million years ago, this galaxy is believed to have consumed a smaller spiral, gas-rich galaxy — the contents of which appear to be churning inside Centaurus A's core, likely triggering new generations of stars.

First glimpses of the "leftovers" of this meal were obtained thanks to observations with the European Space Agency's Infrared Space Observatory, which revealed a 16,500 light-year-wide structure, very similar to that of a small barred galaxy.

More recently, NASA's Spitzer Space Telescope resolved this structure into a parallelogram, which can be explained as the remnant of a gas-rich spiral galaxy falling into an elliptical galaxy and becoming twisted and warped in the process. Galaxy merging is the most common mechanism to explain the formation of such giant elliptical galaxies.

The new images, taken by the European Southern Observatory's 3.58-metre New Technology Telescope (NTT) in La Silla, Chile, allow astronomers to get an even sharper view of the structure of this galaxy, completely free of obscuring dust.

What the astronomers found in the images was surprising: "There is a clear ring of stars and clusters hidden behind the dust lanes, and our images provide an unprecedentedly detailed view toward it," said Jouni Kainulainen, lead author of the paper reporting these results. "Further analysis of this structure will provide important clues on how the merging process occurred and what has been the role of star formation during it."

The technique used to observe Centaurus A could help scientists better understand star formation in galaxies.

"These are the first steps in the development of a new technique that has the potential to trace giant clouds of gas in other galaxies at high resolution and in a cost-effective way," said co-author João Alves. "Knowing how these giant clouds form and evolve is to understand how stars form in galaxies

New Experiment to Test Super Teflon in Space

Teflon-coated frying pans may scratch easily, but a souped-up version, a nanomaterial 10,000 times more durable than the ordinary non-stick stuff, is headed for the space station to see if it could someday coat the mechanical moving parts of spacecraft.

But first it must prove it can survive ultraviolet radiation, atomic oxygen, extreme temperatures and other space hazards, after blasting offMonday aboard the space shuttle Atlantis on a course for the International Space Station (ISS).

Astronauts intend to install the material outside the space station during one of the mission's planned spacewalks.

The super Teflon could theoretically slide across a surface for more than 62,000 miles (100,000 km) before wearing away, compared to ordinary Teflon that would last just a mile or so. Researchers added fluoride-coated alumina nanoparticles that helped boost the material's strength and durability, even as it retained most of the Teflon's non-stick slipperiness.

"These are low wear, low friction materials that work well in vacuum, and we want to know if they work well in space," said Greg Sawyer, a mechanical and aerospace engineer at the University of Florida. He leads a multi-university effort backed by the U.S. Air Force that designed a whole range of nanocomposite materials for space trials aboard the space station.

Better space-age materials

Sawyer worked with his former mentors at the Rensselaer Polytechnic Institute (RPI) in New York to develop nanocomposite materials for many different space applications. Super Teflon's durability and non-stick character would make it easier for moving parts within spacecraft to move, and require less energy due to less resistance from friction.

Rensselaer researchers also built conductive nanocomposites in collaboration with the U.S. Department of Energy National Renewable Energy Laboratory. One material consists of a tough polymer filled withcarbon nanotubes, or tiny cylinders made of carbon that can conduct electricity. The second conductive material involves liquid crystalline polymers, which can resist fires and many industrial chemicals.

"Conductivity experiments look at how materials with conductivity degrade over time," Sawyer told SPACE.com. "With PTSE [Teflon] and those materials you're looking at how long they can provide adequate lubrication."

Another even more futuristic material comes in the form of so-called "chameleon" coatings developed by the Air Force Research Laboratory in Ohio. These adaptive materials can change their coating surfaces based on how much friction or strength is needed.

Space trials are a go

Researchers ensured that all the nanocomposite materials flying aboard the space shuttle Atlantis could first endure vacuum tests on Earth, as a bare minimum requirement for surviving space trials. The team had to scramble in particular to develop the conductive nanocomposites and ready it for launch in less than a week.

"It was an exciting week and we weren't sure if the composites would hold up to the rigorous testing imposed on them to determine if they could even be launched into space," said Linda Schadler, a materials engineer at RPI.

The Teflon study is part of a larger Materials International Space Station Experiment - 7 (MISSE-7) that will expose materials on an outside test bed, where the experiments face intense radiation and temperatures ranging from -40 degrees to 140 degrees F (-40 degrees to 60 degrees C). Atomic oxygen formed by ultraviolet rays splitting oxygen into single atoms also poses a unique space hazard that can erode materials.

Sawyer designed a tribometer that can monitor the friction of the materials such as the super Teflon. The material sample sits on a turntable resembling a record, and stationary pin rests on top of the spinning sample.

"The sample spins under the pin, and during that we can record the forces so we know how the material is behaving," Sawyer explained.

The experimental setup automatically sends data in real-time to the ISS lab, which then forwards the info to university labs on Earth. After all the work that went into getting their materials launched into space, researchers plan on running the space trials for as long as possible.

Ultimately, MISSE experiments - which can be folded up like a suitcase – can be collected by spacewalking astronauts to be packed up and returned to Earth for waiting scientists