Jets and explosions in NGC 7793

This new image from the NASA/ESA Hubble Space Telescope shows NGC 7793, a spiral galaxy in the constellation of Sculptor some 13 million light-years away from Earth. NGC 7793 is one of the brightest galaxies in the Sculptor Group, and one of the closest groups of galaxies to the Local Group — the group of galaxies containing our galaxy, the Milky Way and the Magellanic Clouds.
The image shows NGC 7793’s spiral arms and small central bulge. Unlike some other spirals, NGC 7793 doesn’t have a very pronounced spiral structure, and its shape is further muddled by the mottled pattern of dark dust that stretches across the frame. The occasional burst of bright pink can be seen in the galaxy, highlighting stellar nurseries containing newly-forming baby stars.
Although it may look serene and beautiful from our perspective, this galaxy is actually a very dramatic and violent place. Astronomers have discovered a powerful microquasar within NGC 7793 — a system containing a black hole actively feeding on material from a companion star. While many full-sized quasars are known at the cores of other galaxies, it is unusual to find a quasar in a galaxy’s disc rather than at its centre.
Micro-quasars are almost like scale models — they allow astronomers to study quasars in detail. As material falls inwards towards this black hole, it creates a swirling disc around it. Some of the infalling gas is propelled violently outwards at extremely high speeds, creating jets streaking out into space in opposite directions. In the case of NGC 7793, these jets are incredibly powerful, and are in the process of creating an expanding bubble of hot gas some 1000 light-years across.

Image credit: ESA/Hubble & NASA

Jets and explosions in NGC 7793

This new image from the NASA/ESA Hubble Space Telescope shows NGC 7793, a spiral galaxy in the constellation of Sculptor some 13 million light-years away from Earth. NGC 7793 is one of the brightest galaxies in the Sculptor Group, and one of the closest groups of galaxies to the Local Group — the group of galaxies containing our galaxy, the Milky Way and the Magellanic Clouds.

The image shows NGC 7793’s spiral arms and small central bulge. Unlike some other spirals, NGC 7793 doesn’t have a very pronounced spiral structure, and its shape is further muddled by the mottled pattern of dark dust that stretches across the frame. The occasional burst of bright pink can be seen in the galaxy, highlighting stellar nurseries containing newly-forming baby stars.

Although it may look serene and beautiful from our perspective, this galaxy is actually a very dramatic and violent place. Astronomers have discovered a powerful microquasar within NGC 7793 — a system containing a black hole actively feeding on material from a companion star. While many full-sized quasars are known at the cores of other galaxies, it is unusual to find a quasar in a galaxy’s disc rather than at its centre.

Micro-quasars are almost like scale models — they allow astronomers to study quasars in detail. As material falls inwards towards this black hole, it creates a swirling disc around it. Some of the infalling gas is propelled violently outwards at extremely high speeds, creating jets streaking out into space in opposite directions. In the case of NGC 7793, these jets are incredibly powerful, and are in the process of creating an expanding bubble of hot gas some 1000 light-years across.

Image credit: ESA/Hubble & NASA

(Source: spacetelescope.org)

Dizzying star trails over SEST


The 15-metre diameter Swedish–ESO Submillimetre Telescope (SEST) was built in 1987, and was operated at ESO’s La Silla Observatory in Chile until it was decommissioned in 2003.



At the time of construction, SEST was the only radio telescope in the southern hemisphere that was designed to observe the submillimetre Universe, and it paved the way for later telescopes such as the Atacama Pathfinder Experiment telescope (APEX), and the Atacama Large Millimeter/submillimeter Array (ALMA), both located at Chajnantor.
In this image, we see a crowded night sky filled with star trails, a result of the camera’s long exposure time. The starlight is reflected back at numerous different angles towards the camera from the giant parabolic dish. In the background, the ESO 3.6-metre telescopestands in its dome, silently surveying the cosmos.

Image credit: ESO/José Joaquín Pérez

Dizzying star trails over SEST

The 15-metre diameter Swedish–ESO Submillimetre Telescope (SEST) was built in 1987, and was operated at ESO’s La Silla Observatory in Chile until it was decommissioned in 2003.

At the time of construction, SEST was the only radio telescope in the southern hemisphere that was designed to observe the submillimetre Universe, and it paved the way for later telescopes such as the Atacama Pathfinder Experiment telescope (APEX), and the Atacama Large Millimeter/submillimeter Array (ALMA), both located at Chajnantor.

In this image, we see a crowded night sky filled with star trails, a result of the camera’s long exposure time. The starlight is reflected back at numerous different angles towards the camera from the giant parabolic dish. In the background, the ESO 3.6-metre telescopestands in its dome, silently surveying the cosmos.

Image credit: ESO/José Joaquín Pérez

(Source: eso.org)

Saturn at equinox

How would Saturn look if its ring plane pointed right at the Sun? Before August 2009, nobody knew. Every 15 years, as seen from Earth, Saturn’s rings point toward the Earth and appear to disappear. The disappearing rings are no longer a mystery — Saturn’s rings are known to be so thin and the Earth is so near the Sun that when the rings point toward the Sun, they also point nearly edge-on at the Earth. Fortunately, in this third millennium, humanity is advanced enough to have a spacecraft that can see the rings during equinox from the side. In August 2009, that Saturn-orbiting spacecraft, Cassini, was able to snap a series of unprecedented pictures of Saturn’s rings during equinox. A digital composite of 75 such images is shown above. The rings appear unusually dark, and a very thin ring shadow line can be made out on Saturn’s cloud-tops. Objects sticking out of the ring plane are brightly illuminated and cast long shadows. Inspection of these images is helping humanity to understand the specific sizes of Saturn’s ring particles and the general dynamics of orbital motion. This week, Earth undergoes an equinox.

Image credit: Cassini Imaging Team, ISS, JPL, ESA, NASA

Saturn at equinox

How would Saturn look if its ring plane pointed right at the Sun? Before August 2009, nobody knew. Every 15 years, as seen from Earth, Saturn’s rings point toward the Earth and appear to disappear. The disappearing rings are no longer a mystery — Saturn’s rings are known to be so thin and the Earth is so near the Sun that when the rings point toward the Sun, they also point nearly edge-on at the Earth. Fortunately, in this third millennium, humanity is advanced enough to have a spacecraft that can see the rings during equinox from the side. In August 2009, that Saturn-orbiting spacecraft, Cassini, was able to snap a series of unprecedented pictures of Saturn’s rings during equinox. A digital composite of 75 such images is shown above. The rings appear unusually dark, and a very thin ring shadow line can be made out on Saturn’s cloud-tops. Objects sticking out of the ring plane are brightly illuminated and cast long shadows. Inspection of these images is helping humanity to understand the specific sizes of Saturn’s ring particles and the general dynamics of orbital motion. This week, Earth undergoes an equinox.

Image credit: Cassini Imaging Team, ISS, JPL, ESA, NASA

(Source: apod.nasa.gov)


Celebration: MAVEN arrives at Mars







Members of the Mars Atmosphere and Volatile Evolution (MAVEN) team celebrate at the Lockheed Martin operations center in Littleton, Colorado, Sunday night, after getting confirmation that the spacecraft entered Mars’ orbit.
MAVEN is the first spacecraft dedicated to exploring the tenuous upper atmosphere of Mars, and will soon begin taking measurements of the composition, structure and escape of gases in Mars’ upper atmosphere and its interaction with the sun and solar wind.

Image credit: Lockheed Martin

Celebration: MAVEN arrives at Mars

Members of the Mars Atmosphere and Volatile Evolution (MAVEN) team celebrate at the Lockheed Martin operations center in Littleton, Colorado, Sunday night, after getting confirmation that the spacecraft entered Mars’ orbit.

MAVEN is the first spacecraft dedicated to exploring the tenuous upper atmosphere of Mars, and will soon begin taking measurements of the composition, structure and escape of gases in Mars’ upper atmosphere and its interaction with the sun and solar wind.

Image credit: Lockheed Martin

(Source: nasa.gov)

Shoreline of the universe

Against dark rifts of interstellar dust, the ebb and flow of starlight along the Milky Way looks like waves breaking on a cosmic shore in this night skyscape. Taken with a digital camera from the dunes of Hatteras Island, North Carolina, planet Earth, the monochrome image is reminiscent of the time when sensitive black and white film was a popular choice for dimly lit night- and astro-photography. Looking south, the bright stars of Sagittarius and Scorpius are near the center of the frame. Wandering Mars, Saturn, and Zubenelgenubi (Alpha Librae) form the compact triangle of bright celestial beacons farther right of the galaxy’s central bulge. Of course, the evocative black and white beach scene could also be from that vintage 1950s scifi movie you never saw, “It Came From Beyond the Dunes.”

Image credit & copyright: Bill Dickinson

Shoreline of the universe

Against dark rifts of interstellar dust, the ebb and flow of starlight along the Milky Way looks like waves breaking on a cosmic shore in this night skyscape. Taken with a digital camera from the dunes of Hatteras Island, North Carolina, planet Earth, the monochrome image is reminiscent of the time when sensitive black and white film was a popular choice for dimly lit night- and astro-photography. Looking south, the bright stars of Sagittarius and Scorpius are near the center of the frame. Wandering Mars, Saturn, and Zubenelgenubi (Alpha Librae) form the compact triangle of bright celestial beacons farther right of the galaxy’s central bulge. Of course, the evocative black and white beach scene could also be from that vintage 1950s scifi movie you never saw, “It Came From Beyond the Dunes.”

Image credit & copyright: Bill Dickinson

(Source: apod.nasa.gov)


Aurora over a glacier lagoon
Image credit and copyright: James Woodend, UK

Aurora over a glacier lagoon

Image credit and copyright: James Woodend, UK

(Source: universetoday.com)

Perspective view of Hooke crater in Argyre basin

Hooke crater is located near the northern edge of the 1800 km-wide Argyre basin, one of the most impressive impact structures on Mars, excavated in a giant collision about 4 billion years ago.
Sitting in a flat part of the basin known as Argyre Planitia, Hooke crater has a diameter of 138 km and a maximum depth of about 2.4 km. It is named after the English physicist and astronomer Robert Hooke (1635–1703).
Hooke crater comprises two different impact structures, with a smaller impactor blasting a depression off-centre in the floor of a larger, pre-existing crater. The newer crater in the centre is filled with a large mound topped by a dark dune field. The mound appears to be composed of layered material, possibly alternating sheets of sand and frost.


Image credits: ESA/DLR/FU Berlin

Perspective view of Hooke crater in Argyre basin

Hooke crater is located near the northern edge of the 1800 km-wide Argyre basin, one of the most impressive impact structures on Mars, excavated in a giant collision about 4 billion years ago.

Sitting in a flat part of the basin known as Argyre Planitia, Hooke crater has a diameter of 138 km and a maximum depth of about 2.4 km. It is named after the English physicist and astronomer Robert Hooke (1635–1703).

Hooke crater comprises two different impact structures, with a smaller impactor blasting a depression off-centre in the floor of a larger, pre-existing crater. The newer crater in the centre is filled with a large mound topped by a dark dune field. The mound appears to be composed of layered material, possibly alternating sheets of sand and frost.

Image credits: ESA/DLR/FU Berlin

Potentially habitable moons

For astrobiologists, these may be the four most tantalizing moons in our Solar System. Shown at the same scale, their exploration by interplanetary spacecraft has launched the idea that moons, not just planets, could have environments supporting life. The Galileo mission to Jupiter discovered Europa’s global subsurface ocean of liquid water and indications of Ganymede’s interior seas. At Saturn, the Cassini probe detected erupting fountains of water ice from Enceladus indicating warmer subsurface water on even that small moon, while finding surface lakes of frigid but still liquid hydrocarbons beneath the dense atmosphere of large moon Titan. Now looking beyond the Solar System, new research suggests that sizable exomoons, could actually outnumber exoplanets in stellar habitable zones. That would make moons the most common type of habitable world in the Universe.

Image Credit: Research and compilation - René Heller (McMaster Univ.) et al.  Panels - NASA/JPL/Space Science Institute - Copyright: Ted Stryk

Potentially habitable moons

For astrobiologists, these may be the four most tantalizing moons in our Solar System. Shown at the same scale, their exploration by interplanetary spacecraft has launched the idea that moons, not just planets, could have environments supporting life. The Galileo mission to Jupiter discovered Europa’s global subsurface ocean of liquid water and indications of Ganymede’s interior seas. At Saturn, the Cassini probe detected erupting fountains of water ice from Enceladus indicating warmer subsurface water on even that small moon, while finding surface lakes of frigid but still liquid hydrocarbons beneath the dense atmosphere of large moon Titan. Now looking beyond the Solar System, new research suggests that sizable exomoons, could actually outnumber exoplanets in stellar habitable zones. That would make moons the most common type of habitable world in the Universe.

Image Credit: Research and compilation - René Heller (McMaster Univ.) et al.  Panels - NASA/JPL/Space Science Institute - Copyright: Ted Stryk

(Source: apod.nasa.gov)


Titan’s thick haze
Image credit: NASA/JPL/Space Science Institute

Titan’s thick haze

Image credit: NASA/JPL/Space Science Institute

(Source: universetoday.com)

thedemon-hauntedworld:

M16 Eagle Nebula Credit: Stefan S, Astrobin

thedemon-hauntedworld:

M16 Eagle Nebula
Credit: Stefan S, Astrobin

Cocoon nebula wide field

In this crowded starfield covering over 2 degrees within the high flying constellation Cygnus, the eye is drawn to the Cocoon Nebula. A compact star forming region, the cosmic Cocoon punctuates a long trail of obscuring interstellar dust clouds. Cataloged as IC 5146, the nebula is nearly 15 light-years wide, located some 4,000 light years away. Like other star forming regions, it stands out in red, glowing, hydrogen gas excited by the young, hot stars and blue, dust-reflected starlight at the edge of an otherwise invisible molecular cloud. In fact, the bright star near the center of this nebula is likely only a few hundred thousand years old, powering the nebular glow as it clears out a cavity in the molecular cloud’s star forming dust and gas. But the long dusty filaments that appear dark in this visible light image are themselves hiding stars in the process of formation that can be seen seen at infrared wavelengths.

Image credit & copyright: Federico Pelliccia

Cocoon nebula wide field

In this crowded starfield covering over 2 degrees within the high flying constellation Cygnus, the eye is drawn to the Cocoon Nebula. A compact star forming region, the cosmic Cocoon punctuates a long trail of obscuring interstellar dust clouds. Cataloged as IC 5146, the nebula is nearly 15 light-years wide, located some 4,000 light years away. Like other star forming regions, it stands out in red, glowing, hydrogen gas excited by the young, hot stars and blue, dust-reflected starlight at the edge of an otherwise invisible molecular cloud. In fact, the bright star near the center of this nebula is likely only a few hundred thousand years old, powering the nebular glow as it clears out a cavity in the molecular cloud’s star forming dust and gas. But the long dusty filaments that appear dark in this visible light image are themselves hiding stars in the process of formation that can be seen seen at infrared wavelengths.

Image credit & copyright: Federico Pelliccia

(Source: apod.nasa.gov)

thedemon-hauntedworld:

M94, Multi-ring galaxy M94 is a complex galaxy in Canes Venatici. It has both inner and outer rings surrounding an unusually bright and active core. The blue areas in the innermost ring are areas of intense star formation. In this image, the outer ring shows hints of the very faint spiral structure seen in recent professional images.
Credit: Bruce Waddington

thedemon-hauntedworld:

M94, Multi-ring galaxy
M94 is a complex galaxy in Canes Venatici. It has both inner and outer rings surrounding an unusually bright and active core. The blue areas in the innermost ring are areas of intense star formation. In this image, the outer ring shows hints of the very faint spiral structure seen in recent professional images.

Credit: Bruce Waddington

(via classicallyforbiddenregions)

New observations explain why Milky Way-like galaxies are so common in the Universe

For decades scientists have believed that galaxy mergers usually result in the formation of elliptical galaxies. Now, for the the first time, researchers using ALMA and a host of other radio telescopes have found direct evidence that merging galaxies can instead form disc galaxies, and that this outcome is in fact quite common. This surprising result could explain why there are so many spiral galaxies like the Milky Way in the Universe.
An international research group led by Junko Ueda, a Japan Society for the Promotion of Science postdoctoral fellow, has made surprising observations that most galaxy collisions in the nearby Universe — within 40–600 million light-years from Earth — result in so-called disc galaxies. Disc galaxies — including spiral galaxies like the Milky Way and lenticular galaxies — are defined by pancake-shaped regions of dust and gas, and are distinct from the category of elliptical galaxies.
It has, for some time, been widely accepted that merging disc galaxies would eventually form an elliptically shaped galaxy. During these violent interactions the galaxies do not only gain mass as they merge or cannibalise each-other, but they are also changing their shape throughout cosmic time, and therefore changing type along the way.
Computer simulations from the 1970s predicted that mergers between two comparable disc galaxies would result in an elliptical galaxy. The simulations predict that most galaxies today are elliptical, clashing with observations that over 70% of galaxies are in fact disc galaxies. However, more recent simulations have suggested that collisions could also form disc galaxies.
To identify the final shapes of galaxies after mergers observationally, the group studied the distribution of gas in 37 galaxies that are in their final stages of merging. The Atacama Large Millimeter/sub-millimeter Array (ALMA) and several other radio telescopes [1] were used to observe emission from carbon monoxide (CO), an indicator of molecular gas. 
The team’s research is the largest study of molecular gas in galaxies to date and provides unique insight into how the Milky Way might have formed. Their study revealed that almost all of the mergers show pancake-shaped areas of molecular gas, and hence are disc galaxies in the making. Ueda explains: “For the first time there is observational evidence for merging galaxies that could result in disc galaxies. This is a large and unexpected step towards understanding the mystery of the birth of disc galaxies.”
Nonetheless, there is a lot more to discover. Ueda added: “We have to start focusing on the formation of stars in these gas discs. Furthermore, we need to look farther out in the more distant Universe. We know that the majority of galaxies in the more distant Universe also have discs. We however do not yet know whether galaxy mergers are also responsible for these, or whether they are formed by cold gas gradually falling into the galaxy. Maybe we have found a general mechanism that applies throughout the history of the Universe.”

Image credit: ALMA (ESO/NAOJ/NRAO)/SMA/CARMA/IRAM/J. Ueda et al.

New observations explain why Milky Way-like galaxies are so common in the Universe

For decades scientists have believed that galaxy mergers usually result in the formation of elliptical galaxies. Now, for the the first time, researchers using ALMA and a host of other radio telescopes have found direct evidence that merging galaxies can instead form disc galaxies, and that this outcome is in fact quite common. This surprising result could explain why there are so many spiral galaxies like the Milky Way in the Universe.

An international research group led by Junko Ueda, a Japan Society for the Promotion of Science postdoctoral fellow, has made surprising observations that most galaxy collisions in the nearby Universe — within 40–600 million light-years from Earth — result in so-called disc galaxies. Disc galaxies — including spiral galaxies like the Milky Way and lenticular galaxies — are defined by pancake-shaped regions of dust and gas, and are distinct from the category of elliptical galaxies.

It has, for some time, been widely accepted that merging disc galaxies would eventually form an elliptically shaped galaxy. During these violent interactions the galaxies do not only gain mass as they merge or cannibalise each-other, but they are also changing their shape throughout cosmic time, and therefore changing type along the way.

Computer simulations from the 1970s predicted that mergers between two comparable disc galaxies would result in an elliptical galaxy. The simulations predict that most galaxies today are elliptical, clashing with observations that over 70% of galaxies are in fact disc galaxies. However, more recent simulations have suggested that collisions could also form disc galaxies.

To identify the final shapes of galaxies after mergers observationally, the group studied the distribution of gas in 37 galaxies that are in their final stages of merging. The Atacama Large Millimeter/sub-millimeter Array (ALMA) and several other radio telescopes [1] were used to observe emission from carbon monoxide (CO), an indicator of molecular gas. 

The team’s research is the largest study of molecular gas in galaxies to date and provides unique insight into how the Milky Way might have formed. Their study revealed that almost all of the mergers show pancake-shaped areas of molecular gas, and hence are disc galaxies in the making. Ueda explains: “For the first time there is observational evidence for merging galaxies that could result in disc galaxies. This is a large and unexpected step towards understanding the mystery of the birth of disc galaxies.

Nonetheless, there is a lot more to discover. Ueda added: “We have to start focusing on the formation of stars in these gas discs. Furthermore, we need to look farther out in the more distant Universe. We know that the majority of galaxies in the more distant Universe also have discs. We however do not yet know whether galaxy mergers are also responsible for these, or whether they are formed by cold gas gradually falling into the galaxy. Maybe we have found a general mechanism that applies throughout the history of the Universe.”

Image credit: ALMA (ESO/NAOJ/NRAO)/SMA/CARMA/IRAM/J. Ueda et al.

(Source: eso.org)

Big surprises can come in small packages

Astronomers using the NASA/ESA Hubble Space Telescope have found a monster lurking in a very unlikely place. New observations of the ultracompact dwarf galaxy M60-UCD1 have revealed a supermassive black hole at its heart, making this tiny galaxy the smallest ever found to host a supermassive black hole. This suggests that there may be many more supermassive black holes that we have missed, and tells us more about the formation of these incredibly dense galaxies.




Lying about 50 million light-years away, M60-UCD1 is a tiny galaxy with a diameter of 300 light-years — just 1/500th of the diameter of the Milky Way. Despite its size it is pretty crowded, containing some 140 million stars. While this is characteristic of an ultracompact dwarf galaxy (UCD) like M60-UCD1, this particular UCD happens to be the densest ever seen.
Despite their huge numbers of stars, UCDs always seem to be heavier than they should be. Now, an international team of astronomers has made a new discovery that may explain why — at the heart of M60-UCD1 lurks a supermassive black hole with the mass of 20 million Suns.
"We’ve known for some time that many UCDs are a bit overweight. They just appear to be too heavy for the luminosity of their stars," says co-author Steffen Mieske of the European Southern Observatory in Chile. "We had already published a study that suggested this additional weight could come from the presence of supermassive black holes, but it was only a theory. Now, by studying the movement of the stars within M60-UCD1, we have detected the effects of such a black hole at its centre. This is a very exciting result and we want to know how many more UCDs may harbour such extremely massive objects."
The supermassive black hole at the centre of M60-UCD1 makes up a huge 15 percent of the galaxy’s total mass, and weighs five times that of the black hole at the centre of the Milky Way. "That is pretty amazing, given that the Milky Way is 500 times larger and more than 1000 times heavier than M60-UCD1," explains Anil Seth of the University of Utah, USA, lead author of the international study. "In fact, even though the black hole at the centre of our Milky Way galaxy has the mass of 4 million Suns it is still less than 0.01 percent of the Milky Way’s total mass, which makes you realise how significant M60-UCD1’s black hole really is."
The team discovered the supermassive black hole by observing M60-UCD1 with both the NASA/ESA Hubble Space Telescope and the Gemini North 8-metre optical and infrared telescope on Hawaii’s Mauna Kea, USA. The sharp Hubble images provided information about the galaxy’s diameter and stellar density, whilst Gemini was used to measure the movement of stars in the galaxy as they were affected by the black hole’s gravitational pull. These data were then used to calculate the mass of the unseen black hole.
The finding implies that there may be a substantial population of previously unnoticed black holes. In fact, the astronomers predict there may be as many as double the known number of black holes in the local Universe.
Additionally, the results could affect theories of how such UCDs form. One explanation is that M60-UCD1 was once a large galaxy containing 10 billion stars, and a supermassive black hole to match. "This galaxy may have passed too close to the centre of its much larger neighbouring galaxy, Messier 60," explains co author Remco van den Bosch of the Max Planck Institute for Astronomy in Heidelberg, Germany. "In that process the outer part of the galaxy would have been torn away to become part of Messier 60, leaving behind only the small and compact galaxy we see today."
The team believes that M60-UDC1 may one day merge with Messier 60 to form a single galaxy. Messier 60 also has its own monster black hole an amazing 4.5 billion times the size of our Sun and more than 1000 times bigger than the black hole in our Milky Way. A merger between the two galaxies would also cause the black holes to merge, creating an even more monstrous black hole.

Image credit: NASA, ESA, D. Coe, G. Bacon (STScI)

Big surprises can come in small packages

Astronomers using the NASA/ESA Hubble Space Telescope have found a monster lurking in a very unlikely place. New observations of the ultracompact dwarf galaxy M60-UCD1 have revealed a supermassive black hole at its heart, making this tiny galaxy the smallest ever found to host a supermassive black hole. This suggests that there may be many more supermassive black holes that we have missed, and tells us more about the formation of these incredibly dense galaxies.

Lying about 50 million light-years away, M60-UCD1 is a tiny galaxy with a diameter of 300 light-years — just 1/500th of the diameter of the Milky Way. Despite its size it is pretty crowded, containing some 140 million stars. While this is characteristic of an ultracompact dwarf galaxy (UCD) like M60-UCD1, this particular UCD happens to be the densest ever seen.

Despite their huge numbers of stars, UCDs always seem to be heavier than they should be. Now, an international team of astronomers has made a new discovery that may explain why — at the heart of M60-UCD1 lurks a supermassive black hole with the mass of 20 million Suns.

"We’ve known for some time that many UCDs are a bit overweight. They just appear to be too heavy for the luminosity of their stars," says co-author Steffen Mieske of the European Southern Observatory in Chile. "We had already published a study that suggested this additional weight could come from the presence of supermassive black holes, but it was only a theory. Now, by studying the movement of the stars within M60-UCD1, we have detected the effects of such a black hole at its centre. This is a very exciting result and we want to know how many more UCDs may harbour such extremely massive objects."

The supermassive black hole at the centre of M60-UCD1 makes up a huge 15 percent of the galaxy’s total mass, and weighs five times that of the black hole at the centre of the Milky Way. "That is pretty amazing, given that the Milky Way is 500 times larger and more than 1000 times heavier than M60-UCD1," explains Anil Seth of the University of Utah, USA, lead author of the international study. "In fact, even though the black hole at the centre of our Milky Way galaxy has the mass of 4 million Suns it is still less than 0.01 percent of the Milky Way’s total mass, which makes you realise how significant M60-UCD1’s black hole really is."

The team discovered the supermassive black hole by observing M60-UCD1 with both the NASA/ESA Hubble Space Telescope and the Gemini North 8-metre optical and infrared telescope on Hawaii’s Mauna Kea, USA. The sharp Hubble images provided information about the galaxy’s diameter and stellar density, whilst Gemini was used to measure the movement of stars in the galaxy as they were affected by the black hole’s gravitational pull. These data were then used to calculate the mass of the unseen black hole.

The finding implies that there may be a substantial population of previously unnoticed black holes. In fact, the astronomers predict there may be as many as double the known number of black holes in the local Universe.

Additionally, the results could affect theories of how such UCDs form. One explanation is that M60-UCD1 was once a large galaxy containing 10 billion stars, and a supermassive black hole to match. "This galaxy may have passed too close to the centre of its much larger neighbouring galaxy, Messier 60," explains co author Remco van den Bosch of the Max Planck Institute for Astronomy in Heidelberg, Germany. "In that process the outer part of the galaxy would have been torn away to become part of Messier 60, leaving behind only the small and compact galaxy we see today."

The team believes that M60-UDC1 may one day merge with Messier 60 to form a single galaxy. Messier 60 also has its own monster black hole an amazing 4.5 billion times the size of our Sun and more than 1000 times bigger than the black hole in our Milky Way. A merger between the two galaxies would also cause the black holes to merge, creating an even more monstrous black hole.

Image credit: NASA, ESA, D. Coe, G. Bacon (STScI)

(Source: spacetelescope.org)

Aurora over Maine

It has been a good week for auroras. Earlier this month active sunspot region 2158 rotated into view and unleashed a series of flares and plasma ejections into the Solar System during its journey across the Sun’s disk. In particular, a pair of Coronal Mass Ejections (CMEs) impacted the Earth’s magnetosphere toward the end of last week, creating the most intense geomagnetic storm so far this year. Although power outages were feared by some, the most dramatic effects of these impacting plasma clouds were auroras seen as far south as Wisconsin, USA. In the featured image taken last Friday night, rays and sheets of multicolored auroras were captured over Acadia National Park, in Maine, USA. Since another CME plasma cloud is currently approaching the Earth, tonight offers another good chance to see an impressive auroral display.

Image credit & copyright: Jeremy P. Gray

Aurora over Maine

It has been a good week for auroras. Earlier this month active sunspot region 2158 rotated into view and unleashed a series of flares and plasma ejections into the Solar System during its journey across the Sun’s disk. In particular, a pair of Coronal Mass Ejections (CMEs) impacted the Earth’s magnetosphere toward the end of last week, creating the most intense geomagnetic storm so far this year. Although power outages were feared by some, the most dramatic effects of these impacting plasma clouds were auroras seen as far south as Wisconsin, USA. In the featured image taken last Friday night, rays and sheets of multicolored auroras were captured over Acadia National Park, in Maine, USA. Since another CME plasma cloud is currently approaching the Earth, tonight offers another good chance to see an impressive auroral display.

Image credit & copyright: Jeremy P. Gray

(Source: apod.nasa.gov)

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