NASA's Chandra Finds Nearest Pair of Supermassive Black Holes

Composite image of spiral galaxy NGC 3393. (Credit: X-ray: NASA/CXC/SAO/G. Fabbiano et al; Optical: NASA/STScI)

Science Daily — Astronomers using NASA's Chandra X-ray Observatory discovered the first pair of supermassive black holes in a spiral galaxy similar to the Milky Way. Approximately 160 million light years from Earth, the pair is the nearest known such phenomenon.

The black holes are located near the center of the spiral galaxy NGC 3393. Separated by only 490 light years, the black holes are likely the remnant of a merger of two galaxies of unequal mass a billion or more years ago.

"If this galaxy wasn't so close, we'd have no chance of separating the two black holes the way we have," said Pepi Fabbiano of the Harvard-Smithsonian Center for Astrophysics (CfA) in Cambridge, Mass., who led the study that appears in this week's online issue of the journal Nature. "Since this galaxy was right under our noses by cosmic standards, it makes us wonder how many of these black hole pairs we've been missing."

Previous observations in X-rays and at other wavelengths indicated that a single supermassive black hole existed in the center of NGC 3393. However, a long look by Chandra allowed the researchers to detect and separate the dual black holes. Both black holes are actively growing and emitting X-rays as gas falls towards them and becomes hotter.

When two equal-sized spiral galaxies merge, astronomers think it should result in the formation of a black hole pair and a galaxy with a disrupted appearance and intense star formation. A well-known example is the pair of supermassive black holes in NGC 6240, which is located about 330 million light years from Earth.

However, NGC 3393 is a well-organized spiral galaxy, and its central bulge is dominated by old stars. These are unusual properties for a galaxy containing a pair of black holes. Instead, NGC 3393 may be the first known instance where the merger of a large galaxy and a much smaller one, dubbed a "minor merger" by scientists, has resulted in the formation of a pair of supermassive black holes. In fact, some theories say that minor mergers should be the most common way for black hole pairs to form, but good candidates have been difficult to find because the merged galaxy is expected to look so typical.

"The two galaxies have merged without a trace of the earlier collision, apart from the two black holes," said co-author Junfeng Wang, also from CfA. "If there was a mismatch in size between the two galaxies it wouldn't be a surprise for the bigger one to survive unscathed."

If this was a minor merger, the black hole in the smaller galaxy should have had a smaller mass than the other black hole before their host galaxies started to collide. Good estimates of the masses of both black holes are not yet available to test this idea, although the observations do show that both black holes are more massive than about a million suns. Assuming a minor merger occurred, the black holes should eventually merge after about a billion years.

Both of the supermassive black holes are heavily obscured by dust and gas, which makes them difficult to observe in optical light. Because X-rays are more energetic, they can penetrate this obscuring material. Chandra's X-ray spectra show clear signatures of a pair of supermassive black holes.

The NGC 3393 discovery has some similarities to a possible pair of supermassive black holes found recently by Julia Comerford of the University of Texas at Austin, also using Chandra data. Two X-ray sources, which may be due to supermassive black holes in a galaxy about two billion light years from Earth, are separated by about 6,500 light years. As in NGC 3393, the host galaxy shows no signs of disturbance or extreme amounts of star formation. However, no structure of any sort, including spiral features, is seen in the galaxy. Also, one of the sources could be explained by a jet, implying only one supermassive black hole is located in the galaxy.

"Collisions and mergers are one of the most important ways for galaxies and black holes to grow," said co-author Guido Risaliti of CfA and the National Institute for Astrophysics in Florence, Italy. "Finding a black hole pair in a spiral galaxy is an important clue in our quest to learn how this happens."

NASA's Marshall Space Flight Center in Huntsville, Ala., manages the Chandra program for NASA's Science Mission Directorate in Washington. The Smithsonian Astrophysical Observatory controls Chandra's science and flight operations from Cambridge, Mass.

For more information on the Chandra mission and this result, including images and other multimedia, visit:http://chandra.harvard.edu and http://www.nasa.gov/chandra

Can I Buy Land on the Moon?

FYI: Can I Buy Land on the Moon?

By Rebecca Boyle

Stake Out Governments can’t claim land on the moon, but individuals and corporations may one day be able to. NASA/iStock

For now at least, the moon is like the sea: everyone can use it, but no one can own it. In 1967 the U.S. and the Soviet Union negotiated the Outer Space Treaty, which states that no nation can own a piece of the moon or an asteroid. “You have a right to go up and take the lunar soil, but you don’t have any right to draw a square on the surface of the moon and say, ‘That square is mine,’” says Stephen E. Doyle, a retired lawyer who served as NASA’s Deputy Director of Internal Affairs. If the Space Settlement Institute—which lobbies for private industry to develop land on other planets—has its way, new laws will allow space colonists to stake moon claims and start a colony.

Alan Wasser, the Space Settlement Institute’s chairman, says that a private company should build a “spaceline,” similar to an airline, between the Earth and moon. And because a corporation is not a nation, the Outer Space Treaty would not apply. Corporations have settled new worlds before. The London Company was a joint stock enterprise that established the Jamestown Settlement in 1607,providing transportation to pioneers in return for seven years of labor in America, where they cultivated tobacco and other crops for the company’s profit.

Wasser says that land ownership—and the promise of profits based on it—is a necessary incentive to invest in space settlement. He is lobbying for legislation that would commit the U.S. government to honor future moon claims. But anyone can buy a deed to land on the moon right now. The Lunar Registry (“Earth’s leading lunar real-estate agency”) sells such deeds on its website for about $20 an acre. Doyle says that some kind of lunar governing body is necessary to recognize and enforce property rights, but no such body exists. So as it stands, the claims are not much more than fancy pieces of paper.

Doyle says that future moon settlers could look to the Antarctic Treaty, which designates the continent as a scientific preserve and prohibits military activity or mining; 28 countries maintain research stations subject to review by the Council of Managers of National Antarctic Programs, which oversees best practices of scientific research on the continent. “Anybody who understands the implications of imposing a national law on celestial bodies,” Doyle says, “understands we are better to treat it like Antarctica and the high seas than we are to treat it like Manhattan.” If not, he says, we would “take all the problems and contests we’ve had on the surface of the Earth for 5,000 years and extend them to outer space.”

Hubble Movies Provide Unprecedented View of Supersonic Jets from Young Stars

The glowing, clumpy streams of material shown in these NASA/ESA Hubble Space Telescope images are the signposts of star birth. Ejected episodically by young stars like cannon salvos, the blobby material zips along at more than 700 000 kilometres per hour. The speedy jets are confined to narrow beams by the powerful stellar magnetic field. Called Herbig-Haro or HH objects, these outflows have a bumpy ride through space. When fast-moving blobs collide with slower-moving gas, bow shocks arise as the material heats up. Bow shocks are glowing waves of material similar to waves produced by the bow of a ship ploughing through water. In HH 2, at lower right, several bow shocks can be seen where several fast-moving clumps have bunched up like cars in a traffic jam. In HH 34, at lower left, a grouping of merged bow shocks reveals regions that brighten and fade over time as the heated material cools where the shocks intersect. In HH 47, at top, the blobs of material look like a string of cars on a crowded motorway, which ends in a chain-reaction accident. The smash up creates the bow shock, left. These images are part of a series of time-lapse movies astronomers have made showing the outflows’ motion over time. The movies were stitched together from images taken over a 14-year period by Hubble’s Wide Field Planetary Camera 2. Hubble followed the jets over three epochs: HH 2 from 1994, 1997, and 2007; HH 34 from 1994, 1998, and 2007; and HH 47 from 1994, 1999, and 2008. The outflows are roughly 1350 light-years from Earth. HH 34 and HH 2 reside near the Orion Nebula, in the northern sky. HH 47 is located in the southern constellation of Vela. (Credit: NASA, ESA, and P. Hartigan (Rice University))

Science Daily — Stars aren't shy about sending out birth announcements. They fire off energetic jets of glowing gas travelling at supersonic speeds in opposite directions through space. Although astronomers have looked at still pictures of stellar jets for decades, now they can watch movies, thanks to the NASA/ESA Hubble Space Telescope.

An international team of scientists led by astronomer Patrick Hartigan of Rice University in Houston, USA, has collected enough high-resolution Hubble images over a 14-year period to stitch together time-lapse movies of young jets ejected from three stars.

The moving pictures offer a unique view of stellar phenomena that move and change over just a few years. Most astronomical processes change over timescales that are much longer than a human lifetime.

The movies reveal the motion of the speedy outflows as they tear through the interstellar environments. Never-before-seen details in the jets' structure include knots of gas brightening and dimming and collisions between fast-moving and slow-moving material, creating glowing arrowhead features. These phenomena are providing clues about the final stages of a star's birth, offering a peek at how the Sun behaved 4.5 billion years ago.

"For the first time we can actually observe how these jets interact with their surroundings by watching these time-lapse movies," said Hartigan. "Those interactions tell us how young stars influence the environments out of which they form. With movies like these, we can now compare observations of jets with those produced by computer simulations and laboratory experiments to see which aspects of the interactions we understand and which we don't understand."

Hartigan's team's results appear in the 20 July 2011 issue of the Astrophysical Journal.

Jets are an active, short-lived phase of star formation, lasting only about 100 000 years. They are called Herbig-Haro (HH) objects, named after George Herbig and Guillermo Haro, who studied the outflows in the 1950s. Astronomers still don't know what role jets play in the star formation process or exactly how the star unleashes them.

A star forms from a collapsing cloud of cold hydrogen gas. As the star grows, it gravitationally attracts more matter, creating a large spinning disc of gas and dust around it. Eventually, planets may arise within the disc as dust clumps together.

The disc material gradually spirals onto the star and escapes as high velocity jets along the star's axis of spin. The speedy jets are confined to narrow beams by the star's powerful magnetic field. The jet phase stops when the disc runs out of material, usually a few million years after the star's birth.

Hartigan and his colleagues used Hubble's Wide Field Planetary Camera 2 to study jets HH 1, HH 2, HH 34, HH 46, and HH 47. HH 1-HH 2 and HH 46-HH 47 are pairs of jets emanating in opposite directions from single stars. Hubble followed the jets over three epochs: HH 1 and HH 2 in 1994, 1997, and 2007; HH 34 in 1994, 1998, and 2007; and HH 46 and HH 47 in 1994, 1999, and 2008. The jets are roughly ten times the width of the Solar System and zip along at more than 700 000 kilometres per hour.

All of the outflows are roughly 1350 light-years from Earth. HH 34, HH 1, and HH 2 reside near the Orion Nebula, in the northern sky. HH 46 and HH 47 are in the southern constellation of Vela (The Sails).

Computer software has woven together these observations, taken over many years, and generated movies that show continuous motion. The movies support previous observations which revealed that the twin jets are not ejected in a steady stream, like water flowing from a garden hose. Instead, they are launched sporadically in clumps. The beaded-jet structure might be like a "ticker tape," recording episodes when material fell onto the star.

The movies show that the clumpy gas in the jets is moving at different speeds like traffic on a motorway. When fast-moving blobs collide with gas in the slow lane, bow shocks arise as the material heats up. Bow shocks are glowing waves of material similar to waves produced by the bow of a ship ploughing through water. In HH 2, for example, several bow shocks can be seen where several fast-moving clumps have bunched up like cars in a traffic jam. In another jet, HH 34, a grouping of merged bow shocks reveals regions that brighten and fade over time as the heated material cools where the shocks intersect.

In other areas of the jets, bow shocks form from encounters with the surrounding dense gas cloud. In HH 1 a bow shock appears at the top of the jet as it grazes the edge of a dense gas cloud. New glowing knots of material also appear. These knots may represent gas from the cloud being swept up by the jet, just as a swift-flowing river pulls along mud from the shoreline.

The movies also provide evidence that the inherent clumpy nature of the jets begins near the newborn stars. In HH 34 Hartigan traced a glowing knot to within about 14 billion kilometres of the star.

"Taken together, our results paint a picture of jets as remarkably diverse objects that undergo highly structured interactions between material within the outflow and between the jet and the surrounding gas," Hartigan explained. "This contrasts with the bulk of the existing simulations which depict jets as smooth systems."

The details revealed by Hubble were so complex that Hartigan consulted with experts in fluid dynamics from Los Alamos National Laboratory in New Mexico, the UK Atomic Weapons Establishment, and General Atomics in San Diego, California, as well as computer specialists from the University of Rochester in New York. Motivated by the Hubble results, Hartigan's team is now conducting laboratory experiments at the Omega Laser facility in New York to understand how supersonic jets interact with their environment.

"The fluid dynamicists immediately picked up on an aspect of the physics that astronomers typically overlook, and that led to a different interpretation for some of the features we were seeing," Hartigan explains. "The scientists from each discipline bring their own unique perspectives to the project, and having that range of expertise has proved invaluable for learning about this critical phase of stellar evolution."

[1] The international team of astronomers in this study consists of Patrick Hartigan (Rice University, Texas, USA), Adam Frank (University of Rochester, New York, USA); John Foster (Atomic Weapons Establishment, Aldermaston, UK); Paula Rosen (Atomic Weapons Establishment, Aldermaston, UK); Bernie Wilde (Los Alamos National Laboratory, New Mexico, USA); Rob Coker (Los Alamos National Laboratory, New Mexico, USA); Melissa Douglas (Los Alamos National Laboratory, New Mexico, USA); Brent Blue (General Atomics, San Diego, California, USA) and Freddy Hansen (General Atomics, San Diego, California, USA).

Videos 

Stellar jet HH 47

This video shows the evolution over time of Herbig-Haro object HH 47, a jet expelled from a newborn star in the southern constellation of Vela. The video was made by stitching together observations of HH 47 made in 1994, 1999 and 2008.

Credit:

NASA, ESA, P. Hartigan (Rice University), G. Bacon (STScI)

Bow shock in stellar jet HH 47

This video shows a close-up of a bow shock in Herbig-Haro object HH 47, a jet expelled from a newborn star in the southern constellation of Vela. Bow shocks like this are similar to the bow wave caused by a boat moving through water. They are produced by fast-moving material from the star colliding with slower-moving material.

The video was made by stitching together observations of HH 47 made in 1994, 1999 and 2008.

Credit:

NASA, ESA, P. Hartigan (Rice University), G. Bacon (STScI)

Bow shock in stellar jet HH 34

This video shows a close-up of a bow shock in Herbig-Haro object HH 34, a jet expelled from a newborn star in the constellation of Orion. Bow shocks like this are similar to the bow wave caused by a boat moving through water. They are produced by fast-moving material from the star colliding with slower-moving material.

The video was made by stitching together observations of HH 34 made in 1994, 1998 and 2007.

Credit:

NASA, ESA, P. Hartigan (Rice University), G. Bacon (STScI)

NASA Satellites Watch as Hurricane Irene Bears Down on East Coast

By Rebecca Boyle

Hurricane Irene Swirls Northward Hurricane Irene is seen swallowing nearly the entire eastern seaboard in this satellite image from Friday morning. The image of Earth's full disk was captured by the GOES-13 satellite at 10:45 a.m. EDT. Click here to embiggen. NASA Goddard Space Flight Center

If you live in the eastern time zone, odds are you're battening down the hatches in advance of Hurricane Irene, a Category 2 monster threatening much of the eastern seaboard. Coastal communities are under mandatory evacuation orders in several states. This NASA Goddard image from Friday morning makes it clear this storm is no joke.

Evacuations are under way in several boroughs in New York, which apparently has never happened before, and the city’s subway system is shutting down at noon tomorrow. Multiple states are under emergency status, Atlantic City is closing casinos, college students are not allowed to move into their dorms, and disaster planners are bracing for power outages from the Carolinas to New England.

Irene has weakened slightly, but the storm could strengthen before it makes landfall, which is expected to happen in North Carolina on Saturday. From there, it will track north through the Chesapeake Bay and the Delaware, Maryland and Virginia peninsula, eventually moving through New York City, where it could still be a Category 2 storm. It will eventually pass through Quebec before petering out in the Labrador Sea.

Peculiar Pair of Galaxies Nicknamed 'The Eyes'

ESO's Very Large Telescope has taken a striking image of a beautiful yet peculiar pair of galaxies nicknamed The Eyes. The larger of these, NGC 4438, was once a spiral galaxy but has become badly deformed by collisions with other galaxies in the last few hundred million years. (Credit: Image courtesy of ESO)

Science Daily  — The European Southern Observatory's Very Large Telescope has taken a striking image of a beautiful yet peculiar pair of galaxies nicknamed The Eyes. The larger of these, NGC 4438, was once a spiral galaxy but has become badly deformed by collisions with other galaxies in the last few hundred million years. This picture is the first to come out of ESO's Cosmic Gems programme, an initiative in which ESO has granted dedicated observing time for outreach purposes.

But although the centres of these two galaxies look similar, their outskirts could not be more different. The galaxy in the lower right, known as NGC 4435, is compact and seems to be almost devoid of gas and dust. In contrast, in the large galaxy in the upper left (NGC 4438) a lane of obscuring dust is visible just below its nucleus, young stars can be seen left of its centre, and gas extends at least up to the edges of the image.

The Eyes are about 50 million light-years away in the constellation of Virgo (The Virgin) and are some 100 000 light-years apart. The nickname comes from the apparent similarity between the cores of this pair of galaxies -- two white ovals that resemble a pair of eyes glowing in the dark when seen in a moderate-sized telescope.

The contents of NGC 4438 have been stripped out by a violent process: a collision with another galaxy. This clash has distorted the galaxy's spiral shape, much as could happen to the Milky Way when it collides with its neighbouring galaxy Andromeda in three or four billion years.

NGC 4435 could be the culprit. Some astronomers believe that the damage caused to NGC 4438 resulted from an approach between the two galaxies to within about 16 000 light-years that happened some 100 million years ago. But while the larger galaxy was damaged, the smaller one was significantly more affected by the collision. Gravitational tides from this clash are probably responsible for ripping away the contents of NGC 4438, and for reducing NGC 4435's mass and removing most of its gas and dust.

Another possibility is that the giant elliptical galaxy Messier 86, further away from The Eyes and not visible in this image, was responsible for the damage caused to NGC 4438. Recent observations have found filaments of ionised hydrogen gas connecting the two large galaxies, indicating that they may have collided in the past.

The elliptical galaxy Messier 86 and The Eyes belong to the Virgo Cluster, a very rich grouping of galaxies. In such close quarters, galaxy collisions are fairly frequent, so perhaps NGC 4438 suffered from encounters with both NGC 4435 and Messier 86.

This picture is the first to be produced as part of the ESO Cosmic Gems programme. This is a new initiative to produce astronomical images for educational and public outreach purposes. The programme mainly makes use of time when the sky conditions are not suitable for science observations to take pictures of interesting, intriguing or visually attractive objects. The data are also made available to professional astronomers through ESO's science archive.

In this case, although there were some clouds, the atmosphere was exceptionally stable, which allowed very sharp details to be revealed in this image taken using the VLT's FORS2 instrument. Light passing through two different filters was used: red (coloured red) and green-yellow (coloured blue), and the exposure times were 1800 seconds and 1980 seconds, respectively. FORS2 is the visual and near ultraviolet FOcal Reducer and low dispersion Spectrograph for the VLT. It is installed on the VLT's Unit Telescope 1.