Disaster looms for gas cloud falling into Milky Way's central black hole

This view shows a simulation of how a gas cloud that has been observed approaching the supermassive black hole at the center of the galaxy may break apart over the next few years.

This is the first time ever that the approach of such a doomed cloud to a supermassive black hole has been observed and it is expected to break up completely during 2013.

The remains of the gas cloud are shown in red and yellow, with the cloud's orbit marked in red. The stars orbiting the black hole are also shown along with blue lines marking their orbits. This view simulates the expected positions of the stars and gas cloud in the year 2021. Credit: ESO/MPE/Marc Schartmann

The normally quiet neighbourhood around the massive black hole at the center of our Milky Way Galaxy is being invaded by a gas cloud that is destined in just a few years to be ripped, shredded and largely eaten.

Many, if not all, galaxies have massive black holes at their centers. But this supermassive black hole is the only one close enough for astronomers to study in detail, so the violent encounter is a unique chance to observe what until now has only been theorised: how a black hole gulps gas, dust and stars as it grows ever bigger.

"When we look at the black holes in the centers of other galaxies, we see them get bright and then fade, but we never know what is actually happening," said Eliot Quataert, a theoretical astrophysicist and University of California, Berkeley professor of astronomy.

"This is an unprecedented opportunity to obtain unique observations and insight into the processes that go on as gas falls into a black hole, heats up and emits light. It's a neat window onto a black hole that's actually capturing gas as it spirals in."

"The next two years will be very interesting and should provide us with extremely valuable information on the behaviour of matter around such massive objects, and its ultimate fate," said Reinhard Genzel, professor of physics at both UC Berkeley and the Max Planck Institute for Extraterrestrial Physics (MPE) in Garching, Germany.

The discovery by Genzel; Stefan Gillessen of the MPE; Quataert and colleagues from Germany, Chile and Illinois will be reported online Wednesday, Dec. 14, in advance of the Jan. 5 publication of the news in the British journal Nature.

Milky Way has a huge hidden neighbour: A Large Perturber

A LARGE satellite galaxy may be lurking, hidden from view, next door to our own.

Sukanya Chakrabarti and Leo Blitz of the University of California, Berkeley, suspected that the gravity of a nearby galaxy was causing perturbations that have been observed in gas on the fringes of the Milky Way.

"We did a large range of simulations where we varied the mass of the perturber and the distance of closest approach," says Chakrabarti. In the best-fitting simulation, the unseen galaxy has about 1 per cent of the Milky Way's mass, or 10 billion times the mass of the sun.

That's a lot. It means the object has roughly the same mass as the Milky Way's brightest satellite galaxy, the Large Magellanic Cloud (LMC).

Right now, says Chakrabarti, the galaxy is roughly 300,000 light years away from us - about twice as far away as the LMC. But the simulations suggest it follows a highly elongated elliptical path, and about 300 million years ago it swept through our own galaxy just 16,000 light years from the galactic centre - closer in than Earth - disturbing the Milky Way's outskirts as it went.

"Overall, it is a very plausible scenario," says Abraham Loeb at the Harvard-Smithsonian Center for Astrophysics in Cambridge, Massachusetts, who was not part of the study. "Of course, the fact that we don't see such a massive satellite is an issue."

Chakrabarti suggests that the galaxy has remained hidden because it is not a brilliant spectacle. Whereas the LMC glistens with bright young stars and the gas that spawned them, the unseen galaxy may be dead, containing old stars and little gas.

To make matters worse, the simulations suggest that the galaxy orbits ours in the same plane as our galaxy's disc. If it is now on the opposite side of the galaxy from us, it could be hiding behind the thick gas and dust in the galactic plane. "It's very likely to be in a region of very high obscuration," says Chakrabarti. The work will appear in Monthly Notices of the Royal Astronomical Society.

By further studying the distribution of gas, Chakrabarti hopes to pinpoint the galaxy's location so that astronomers will know where to look for it. This parallels the way astronomers in the 1840s discovered Neptune from irregularities in the motion of Uranus caused by gravitational tugs from the more distant planet. If the unseen galaxy exists, it will be the first nearby galaxy detected through its gravity rather than its starlight.

The Cosmic Hand; Constellations and Galaxies of Stars

The ultra-dense remains of a massive star light up surrounding gas and dust to create what appears to be a cosmic hand. This pulsar, seen in bright blue at the base of the "palm", is called B1509. The star is so dense that the electrons and protons in its atoms have combined to form neutrons. B1509 spins some 7 times a second and measures just 19 kilometres in diameter. The magnetic field at its surface is 15 trillion times stronger than the Earth's magnetic field. The field drives a wind of electrons and charged atoms that illuminates finger-like structures that extend north.

The pulsar's reach extends to a neighbouring gas cloud called RCW 89, where the wind lights up knots of gas, making them glow brightly in X-rays (visible in orange and red in the upper-right). The temperature in the cloud seems to vary in a circular pattern, which could mean the pulsar is precessing like a spinning top. B1509 sits some 17,000 light years away from Earth, and is estimated to be about 1700 years old. This image was captured by the orbiting Chandra X-ray Observatory. (Image: NASA/CXC/SAO/P Slane et al)

The Cigar Galaxy, or M82, earns its name when viewed in optical and infrared light (left). But X-rays (right) paint a different picture. M82, which sits some 12 million light years away, is one of the most active nearby galaxies, making it a popular subject of study.

Violent starbursts, likely triggered by the gravitational tugs of a neighbouring galaxy, light up the starry disc near its centre. These intense bursts of new star formation blast out plumes of hot gas that glow in the X-ray part of the spectrum (blue). It took 52.5 hours of observing time to create these images, which were taken by the European Space Agency's orbiting XMM-Newton satellite. (Images: ESA)

The chaotic structure of the spiral galaxy NGC 7793 makes it difficult to identify individual spiral arms, though it is possible to discern some rotation. NGC 7793 sits some 12.5 million light years away from Earth. It is one of the brightest members of the Sculptor Group, a cluster of galaxies that is one of the closest neighbours to our Local Group of galaxies. The Very Large Telescope in the Atacama Desert in Chile snapped this image. (Image: ESO)

A nascent bar sits at the centre of NGC 3359, a delicate spiral galaxy that sits some 49 million light years away in the constellation Ursa Major. Bars are elongated, rectangular bodies of stars, gas and dust that are often seen in spiral galaxies, though it is not yet clear how they fit into galaxies' evolution. Although NGC 3359 is several billion years old, this bar seems to be just 500 million years old.

The galaxy's arms are dotted with light-red patches, hydrogen-rich regions that are sites of intense star formation, similar to those seen in the Orion Nebula in the Milky Way. This image was taken by the Gemini North telescope on Mauna Kea in Hawaii. NGC 3359 can be seen with amateur telescopes. (Image: Gemini Observatory Legacy Image)

A stellar nursery is not uniformly bright, a fact highlighted by this image of NGC 3582, a nebula that sits some 10,000 light years away in the constellation Carina. Here, dark dust clouds share space with glowing gas that is energised by the ultraviolet light of young stars. Wispy structures in the clouds are created by radiation from these young stars, as well as by the explosions of short-lived, massive neighbours. This image was taken by the Gemini South telescope on Cerro Pachon in the Chilean Andes. (Image: Gemini Observatory Legacy Image)

This trio of galaxies, which together form a system called Arp 274, seem to be heading toward a cosmic collision. In fact, the two large spirals (middle and right) already seem to be entangled. But their proximity is just an illusion – the galaxies lie at different distances from Earth and are far enough from one another that astronomers do not think they interact. Two foreground stars in the Milky Way can also be seen on the right.

All three galaxies show colourful evidence of new star formation. The energised gas of stellar nurseries (pink) and clusters of young, massive stars (blue) dot the arms of the two spiral galaxies and encircle their compact companion (left). Older stars appear yellow.

Arp 274 sits 400 million light years away in the constellation Virgo. The Hubble Space Telescope snapped the ensemble in early April, after it was chosen by the public from six candidate targets. (Image: NASA/ESA/M. Livio/Hubble Heritage Team/STScI/AURA)

Organic molecules mixed with dust glow green in this infrared image of M33 captured by the Spitzer Space Telescope. M33, also called the Triangulum Galaxy, sits some 2.9 million light years away from Earth. The spiral is a member of the Milky Way's Local Group, a band of dozens of galaxies that travel as an ensemble because they are gravitationally bound. Star-forming regions appear orange-red in this image. Cool material, possibly carried outwards by winds from giant stars or supernovae, glows at infrared wavelengths beyond what optical telescopes detect as the galaxy's edge. (Image: NASA/JPL-Caltech/University of Arizona)

NASA's Galaxy Evolution Explorer captured this ultraviolet image of the nearby planetary nebula NGC 3242, also called "Jupiter's Ghost" (blue and white region at centre). It may sit as little as 1400 light years away in the constellation Hydra. As sun-like stars run out of fuel, they swell into red giants. These bloated stars jettison their outer layers of gas, eventually exposing a dense core of carbon and oxygen called a white dwarf. The ultraviolet light released by the white dwarfs lights up the surrounding gas, creating planetary nebulae. Although sun-like stars live for billions of years, planetary nebulae only last some 10,000 years. Astronomers are not sure whether the wispy white cloud that curves around the blue nebula is a chance passerby or gas that was ejected while the star was still a red giant. (Image: NASA/JPL-Caltech)

Spinning in Space

Milky way 'larger than imagined'

A recent disclosure indicates that the Milky Way is considerably larger (contains more heavenly bodies), bulkier (more mass) and spinning faster (its all relative) than astronomers thought.

For decades, astronomers and stargazers thought that the Milky Way, was a weakling runt compared to the larger Andromeda, but not anymore.

Scientists mapped the Milky Way in a more detailed, three-dimensional way and found that it is 15% greater breadth. More important, it is significantly more dense, with 50% additional mass, which is similar to the weight but includes a size factor.

The new findings were presented at the American Astronomical Society's convention in Long Beach, California. Mark Reid of the Harvard-Smithsonian Centre for Astrophysics in Cambridge, Massachusetts, said it was the cosmic equivalent of him suddenly increasing his bulk from his 5ft 5in, 10 stone frame, to 6ft 3in and 15 stone.

"Previously we thought Andromeda was dominant over the Milky Way, and that we were the little sibling of Andromeda," Mr Reid said. "But now it's more like we're sibling twins."

The fact that the Milky Way and Andromeda are of similar mass means that they share a similar attraction to each other, not necessarily good news. A more massive and attractive Milky Way means that it could be heading for a more violent collision with the neighbouring Andromeda galaxy, sooner than predicted. This event is still likely to be billions of years from now.

Mr Reid and his colleagues used a large system of 10 radio telescope antennas to measure the brightest newborn stars in the galaxy at different times in Earth's orbit around the sun. They made a map of those stars, not just in the locations where they were first seen, but in the third dimension of time - something Mr Reid said has not been done before.

Using this approach, Mr Reid was able to determine the speed at which the spiral-shaped Milky Way is spinning around its centre. That speed - about 568,000mph - is faster than the 492,000mph that scientists had been using for decades.

So now you know why you were feeling a bit dizzy after the New Year Celebrations