Friday, January 30, 2015

The tell-tale signs of a galactic merger

Hubble image of NGC 7714

Wide-field image of NGC 7714 (ground-based image)


*******************************************************************************************************************************

Videos


Panning across NGC 7714
Panning across NGC 7714

Zooming in on NGC 7714
Zooming in on NGC 7714

 
The NASA/ESA Hubble Space Telescope has captured this striking view of spiral galaxy NGC 7714. This galaxy has drifted too close to another nearby galaxy and the dramatic interaction has twisted its spiral arms out of shape, dragged streams of material out into space, and triggered bright bursts of star formation.

NGC 7714 is a spiral galaxy at 100 million light-years from Earth — a relatively close neighbour in cosmic terms.

The galaxy has witnessed some violent and dramatic events in its recent past. Tell-tale signs of this brutality can be seen in NGC 7714's strangely shaped arms, and in the smoky golden haze that stretches out from the galactic centre.

So what caused this disfigurement? The culprit is a smaller companion named NGC 7715, which lies just out of the frame of this image — but is visible in the wider-field DSS image. The two galaxies [1] drifted too close together between 100 and 200 million years ago, and began to drag at and disrupt one another’s structure and shape.

As a result, a ring and two long tails of stars have emerged from NGC 7714, creating a bridge between the two galaxies. This bridge acts as a pipeline, funnelling material from NGC 7715 towards its larger companion and feeding bursts of star formation. Most of the star-forming activity is concentrated at the bright galactic centre, although the whole galaxy is sparking new stars.

Astronomers characterise NGC 7714 as a typical Wolf-Rayet starburst galaxy. This is due to the stars within it; a large number of the new stars are of the Wolf-Rayet type — extremely hot and bright stars that begin their lives with dozens of times the mass of the Sun, but lose most of it very quickly via powerful winds.

This Hubble image is a composite of data capturing a broad range of wavelengths, revealing the correlation of the gas clouds and stars in the galaxy. This new picture not only reveals the intricate structure of NGC 7714, but also shows many other objects that are much further away. These background galaxies resemble faint smudges of light, some of them with spiral forms.

Notes for editors

The Hubble Space Telescope is a project of international cooperation between ESA and NASA.
[1] The interacting pair formed by NGC 7714 and NGC 7715 is named Arp 284.

More information


Credit: NASA and ESA
Acknowledgement: A. Gal-Yam (Weizmann Institute of Science)


Links


Contacts


Georgia Bladon
Hubble/ESA
Garching, Germany
Tel: +49-89-3200-6855
Email:
gbladon@partner.eso.org


Source: ESA/HUBLLE - Space Telescope


The polar ring of Arp 230

Credit: ESA/Hubble & NASA
Acknowledgement: Flickr user Det58


This Picture of the Week shows Arp 230, also known as IC 51, observed by the NASA/ESA Hubble Space Telescope.

Arp 230 is a galaxy of an uncommon or peculiar shape, and is therefore part of the Atlas of Peculiar Galaxies produced by Halton Arp. Its irregular shape is thought to be the result of a violent collision with another galaxy sometime in the past. The collision could also be held responsible for the formation of the galaxy’s polar ring.

The outer ring surrounding the galaxy consists of gas and stars and rotates over the poles of the galaxy. It is thought that the orbit of the smaller of the two galaxies that created Arp 230 was perpendicular to the disc of the second, larger galaxy when they collided. In the process of merging the smaller galaxy would have been ripped apart and may have formed the polar ring structure astronomers can observe today.

Arp 230 is quite small for a lenticular galaxy, so the two original galaxies forming it must both have been smaller than the Milky Way.

A version of this image was entered into the Hubble’s Hidden Treasures image processing competition by flickr user Det58.


Links

Source:  ESA/Hubble - Space Telescope


Thursday, January 29, 2015

Cassini Catches Titan Naked in the Solar Wind

This diagram depicts conditions observed by NASA's Cassini spacecraft during a flyby in Dec. 2013, when Saturn's magnetosphere was highly compressed, exposing Titan to the full force of the solar wind. Image credit: NASA/JPL-Caltech.   › Full image and caption


Researchers studying data from NASA's Cassini mission have observed that Saturn's largest moon, Titan, behaves much like Venus, Mars or a comet when exposed to the raw power of the solar wind. The observations suggest that unmagnetized bodies like Titan might interact with the solar wind in the same basic ways, regardless of their nature or distance from the sun.

Titan is large enough that it could be considered a planet if it orbited the sun on its own, and a flyby of the giant moon in Dec. 2013 simulated that scenario, from Cassini's vantage point. The encounter was unique within Cassini's mission, as it was the only time the spacecraft has observed Titan in a pristine state, outside the region of space dominated by Saturn's magnetic field, called its magnetosphere. 

"We observed that Titan interacts with the solar wind very much like Mars, if you moved it to the distance of Saturn," said Cesar Bertucci of the Institute of Astronomy and Space Physics in Buenos Aires, who led the research with colleagues from the Cassini mission. "We thought Titan in this state would look different. We certainly were surprised," he said.

The solar wind is a fast-flowing gale of charged particles that continually streams outward from the sun, flowing around the planets like islands in a river. Studying the effects of the solar wind at other planets helps scientists understand how the sun's activity affects their atmospheres. These effects can include modification of an atmosphere's chemistry as well as its gradual loss to space.

Titan spends about 95 percent of the time within Saturn's magnetosphere. But during a Cassini flyby on Dec. 1, 2013, the giant moon happened to be on the sunward side of Saturn when a powerful outburst of solar activity reached the planet. The strong surge in the solar wind so compressed the sun-facing side of Saturn's magnetosphere that the bubble's outer edge was pushed inside the orbit of Titan. This left the moon exposed to, and unprotected from, the raging stream of energetic solar particles. 

Using its magnetometer instrument, which is akin to an equisitely sensitive compass, Cassini has observed Titan many times during the mission's decade in the Saturn system, but always within Saturn's magnetosphere. The spacecraft has not been able to detect a magnetic field coming from Titan itself. In its usual state, Titan is cloaked in Saturn's magnetic field.

This time the influence of Saturn was not present, allowing Cassini's magnetometer to observe Titan as it interacted directly with the solar wind. The special circumstance allowed Bertucci and colleagues to study the shockwave that formed around Titan where the full-force solar wind rammed into the moon's atmosphere.

At Earth, our planet's powerful magnetic field acts as a shield against the solar wind, helping to protect our atmosphere from being stripped away. In the case of Venus, Mars and comets -- none of which is protected by a global magnetic field -- the solar wind drapes around the objects themselves, interacting directly with their atmospheres (or in the comet's case, its coma). Cassini saw the same thing at Titan. 

Researchers thought they would have to treat Titan's response to the solar wind with a unique approach because the chemistry of the hazy moon's dense atmosphere is highly complex. But Cassini's observations of a naked Titan hinted at a more elegant solution. "This could mean we can use the same tools to study how vastly different worlds, in different parts of the solar system, interact with the wind from the sun," Bertucci said.

Bertucci noted that the list of similarly unmagnetized bodies might include the dwarf planet Pluto, to be visited this year for the first time by NASA's New Horizons spacecraft.

"After nearly a decade in orbit, the Cassini mission has revealed once again that the Saturn system is full of surprises," said Michele Dougherty, principal investigator of the Cassini magnetometer at Imperial College, London. "After more than a hundred flybys, we have finally encountered Titan out in the solar wind, which will allow us to better understand how such moons maintain or lose their atmospheres."

The new research is published today in the journal Geophysical Review Letters.

The Cassini-Huygens mission is a cooperative project of NASA, the European Space Agency and the Italian Space Agency. NASA's Jet Propulsion Laboratory, a division of the California Institute of Technology in Pasadena, manages the mission for NASA's Science Mission Directorate, Washington, D.C. JPL designed, developed and assembled the Cassini orbiter. The magnetometer team is based at Imperial College, London, U.K. 

More information about Cassini:  http://www.nasa.gov/cassini and http://saturn.jpl.nasa.gov


Media Contact

Preston Dyches
NASA's Jet Propulsion Laboratory, Pasadena, Calif.
818-354-7013

preston.dyches@jpl.nasa.gov



 

Wednesday, January 28, 2015

The Mouth of the Beast

VLT image of the cometary globule CG4
The cometary globule CG4 in the constellation of Puppis
  
PR Image eso1503c
Wide-field view of the sky around the cometary globule CG4



****************************************************************************

Videos
 
Zooming in on the cometary globule CG4
Zooming in on the cometary globule CG4

Panning over a VLT image of the cometary globule CG4
Panning over a VLT image of the cometary globule CG4


VLT images cometary globule CG4

Like the gaping mouth of a gigantic celestial creature, the cometary globule CG4 glows menacingly in this new image from ESO’s Very Large Telescope. Although it appears to be big and bright in this picture, this is actually a faint nebula, which makes it very hard for amateur astronomers to spot. The exact nature of CG4 remains a mystery.

In 1976 several elongated comet-like objects were discovered on pictures taken with the UK Schmidt Telescope in Australia. Because of their appearance, they became known as cometary globules even though they have nothing in common with comets. They were all located in a huge patch of glowing gas called the Gum Nebula. They had dense, dark, dusty heads and long, faint tails, which were generally pointing away from the Vela supernova remnant located at the centre of the Gum Nebula. Although these objects are relatively close by, it took astronomers a long time to find them as they glow very dimly and are therefore hard to detect.

The object shown in this new picture, CG4, which is also sometimes referred to as God’s Hand, is one of these cometary globules. It is located about 1300 light-years from Earth in the constellation of Puppis (The Poop, or Stern).

The head of CG4, which is the part visible on this image and resembles the head of the gigantic beast, has a diameter of 1.5 light-years. The tail of the globule — which extends downwards and is not visible in the image — is about eight light-years long. By astronomical standards this makes it a comparatively small cloud.
The relatively small size is a general feature of cometary globules. All of the cometary globules found so far are isolated, relatively small clouds of neutral gas and dust within the Milky Way, which are surrounded by hot ionised material.

The head part of CG4 is a thick cloud of gas and dust, which is only visible because it is illuminated by the light from nearby stars. The radiation emitted by these stars is gradually destroying the head of the globule and eroding away the tiny particles that scatter the starlight. However, the dusty cloud of CG4 still contains enough gas to make several Sun-sized stars and indeed, CG4 is actively forming new stars, perhaps triggered as radiation from the stars powering the Gum Nebula reached CG4.

Why CG4 and other cometary globules have their distinct form is still a matter of debate among astronomers and two theories have developed. Cometary globules, and therefore also CG4, could originally have been spherical nebulae, which were disrupted and acquired their new, unusual form because of the effects of a nearby supernova explosion. Other astronomers suggest, that cometary globules are shaped by stellar winds and ionising radiation from hot, massive OB stars. These effects could first lead to the bizarrely (but appropriately!) named formations known as elephant trunks and then eventually cometary globules.

To find out more, astronomers need to find out the mass, density, temperature, and velocities of the material in the globules. These can be determined by the measurements of molecular spectral lines which are most easily accessible at millimetre wavelengths — wavelengths at which telescopes like the Atacama Large Millimeter/submillimeter Array (ALMA) operate.

This picture comes from the ESO Cosmic Gems programme, an outreach initiative to produce images of interesting, intriguing or visually attractive objects using ESO telescopes, for the purposes of education and public outreach. The programme makes use of telescope time that cannot be used for science observations. All data collected may also be suitable for scientific purposes, and are made available to astronomers through ESO’s science archive.

More Information

ESO is the foremost intergovernmental astronomy organisation in Europe and the world’s most productive ground-based astronomical observatory by far. It is supported by 15 countries: Austria, Belgium, Brazil, the Czech Republic, Denmark, France, Finland, Germany, Italy, the Netherlands, Portugal, Spain, Sweden, Switzerland and the United Kingdom. ESO carries out an ambitious programme focused on the design, construction and operation of powerful ground-based observing facilities enabling astronomers to make important scientific discoveries. ESO also plays a leading role in promoting and organising cooperation in astronomical research. ESO operates three unique world-class observing sites in Chile: La Silla, Paranal and Chajnantor. At Paranal, ESO operates the Very Large Telescope, the world’s most advanced visible-light astronomical observatory and two survey telescopes. VISTA works in the infrared and is the world’s largest survey telescope and the VLT Survey Telescope is the largest telescope designed to exclusively survey the skies in visible light. ESO is a major partner in ALMA, the largest astronomical project in existence. And on Cerro Armazones, close to Paranal, ESO is building the 39-metre European Extremely Large Telescope, the E-ELT, which will become “the world’s biggest eye on the sky”.

Links

Contacts

Richard Hook
ESO education and Public Outreach Department
Garching bei München, Germany
Tel: +49 89 3200 6655
Cell: +49 151 1537 3591
Email:
rhook@eso.org

Source: ESO

Gigantic ring system around J1407b much larger, heavier than Saturn’s

Artist’s conception of the extrasolar ring system circling the young giant planet or brown dwarf J1407b. The rings are shown eclipsing the young sun-like star J1407, as they would have appeared in early 2007. Credit: Ron Miller


Astronomers at the Leiden Observatory, The Netherlands, and the University of Rochester, USA, have discovered that the ring system that they see eclipse the very young Sun-like star J1407 is of enormous proportions, much larger and heavier than the ring system of Saturn. The ring system – the first of its kind to be found outside our solar system – was discovered in 2012 by a team led by Rochester’s Eric Mamajek.

A new analysis of the data, led by Leiden’s Matthew Kenworthy, shows that the ring system consists of over 30 rings, each of them tens of millions of kilometers in diameter. Furthermore, they found gaps in the rings, which indicate that satellites (“exomoons”) may have formed. The result has been accepted for pexublication in the Astrophysical Journal.

“The details that we see in the light curve are incredible. The eclipse lasted for several weeks, but you see rapid changes on time scales of tens of minutes as a result of fine structures in the rings,” says Kenworthy. “The star is much too far away to observe the rings directly, but we could make a detailed model based on the rapid brightness variations in the star light passing through the ring system. If we could replace Saturn’s rings with the rings around J1407b, they would be easily visible at night and be many times larger than the full moon.”

“This planet is much larger than Jupiter or Saturn, and its ring system is roughly 200 times larger than Saturn’s rings are today,” said co-author Mamajek, professor of physics and astronomy at the University of Rochester. “You could think of it as kind of a super Saturn.”

The astronomers analyzed data from the SuperWASP project – a survey that is designed to detect gas giants that move in front of their parent star. In 2012, Mamajek and colleagues at the University of Rochester reported the discovery of the young star J1407 and the unusual eclipses, and proposed that they were caused by a moon-forming disk around a young giant planet or brown dwarf.

In a third, more recent study also led by Kenworthy, adaptive optics and Doppler spectroscopy were used to estimate the mass of the ringed object. Their conclusions based on these and previous papers on the intriguing system J1407 is that the companion is likely to be a giant planet – not yet seen – with a gigantic ring system responsible for the repeated dimming of J1407’s light.

The light curve tells astronomers that the diameter of the ring system is nearly 120 million kilometers, more than two hundred times as large as the rings of Saturn. The ring system likely contains roughly an Earth’s worth of mass in light-obscuring dust particles.

Mamajek puts into context how much material is contained in these disks and rings. “If you were to grind up the four large Galilean moons of Jupiter into dust and ice and spread out the material over their orbits in a ring around Jupiter, the ring would be so opaque to light that a distant observer that saw the ring pass in front of the sun would see a very deep, multi-day eclipse,” Mamajek says. “In the case of J1407, we see the rings blocking as much as 95 percent of the light of this young Sun-like star for days, so there is a lot of material there that could then form satellites.”

 


In the data the astronomers found at least one clean gap in the ring structure, which is more clearly defined in the new model. “One obvious explanation is that a satellite formed and carved out this gap,” says Kenworthy. “The mass of the satellite could be between that of Earth and Mars. The satellite would have an orbital period of approximately two years around J1407b.”

Astronomers expect that the rings will become thinner in the next several million years and eventually disappear as satellites form from the material in the disks.

“The planetary science community has theorized for decades that planets like Jupiter and Saturn would have had, at an early stage, disks around them that then led to the formation of satellites,” Mamajek explains. “However, until we discovered this object in 2012, no-one had seen such a ring system. This is the first snapshot of satellite formation on million-kilometer scales around a substellar object.”

Astronomers estimate that the ringed companion J1407b has an orbital period roughly a decade in length. The mass of J1407b has been difficult to constrain, but it is most likely in the range of about 10 to 40 Jupiter masses.

The researchers encourage amateur astronomers to help monitor J1407, which would help detect the next eclipse of the rings, and constrain the period and mass of the ringed companion. Observations of J1407 can be reported to the American Association of Variable Star Observers (AAVSO). In the meantime the astronomers are searching other photometric surveys looking for eclipses by yet undiscovered ring systems. 

Kenworthy adds that finding eclipses from more objects like J1407’s companion “is the only feasible way we have of observing the early conditions of satellite formation for the near future. J1407’s eclipses will allow us to study the physical and chemical properties of satellite-spawning circumplanetary disks.”

Contact Author(s)

   
585-276-6264
Email:  lsierra@ur.rochester.edu
Twitter: @leonor_sierra



Tuesday, January 27, 2015

The characteristics of the multiple star "sigma Orionis" are determined

Sigma Orionis Star
Credit:  IAC
 

A detailed study on the multiple star system led by Spanish astrophysicists has identified the period, mass and emission of high energy photons of the main stars of the system

Some three million years ago hundreds of stars formed from a dense cloud of gas and dust in the constellation of Orion (“the Hunter”). The star which swallowed the largest part of the mass was sigma Orionis (sigma Ori), which is now the fourth brightest star in the belt of Orion, and which illuminates the famous Horsehead Nebula. At the same time as sigma Orionis, a large number of stars with a full range of masses formed in its neighbourhood, as well as brown dwarfs, and “rogue” planets (objects similar in mass to that of a Jupiter but which do not rotate around a star, rather they move freely in the star cluster). The smallest objects in Orion´s belt have 10,000 times less mass than sigma Orionis.

To understand the frequency of the birth of low mass stars, brown dwarfs, and rogue planets, and how they evolve, we need first to know what happens to their high mass, blue neighbours. With this in mind, an international team of astronomers led by the Spanish researchers Sergio Simón-Díaz, (IAC/ULL), Jose A. Caballero (CAB, CSIC-INTA), and Javier Lorenzo ( University of Alicante), with the participation of the Institute of Astrophysics of Andalusia, have studied in great detail the multiple star sigma Orionis.

Even eons after their deaths one can observe the unique imprint of high mass stars on almost everything around them: our own chemical composition, the distribution in space of the stars and the nebulae which they leave behind after they have exploded, the form of the spiral arms of the galaxies, and even, curiously enough, the number of low mass stars. “This latter effect –explains Sergio Simón-Díaz, who is first author on the paper- is due to the fact that low mass stars, and brown dwarfs (which are objects with masses between those of the smallest stars and the largest planets) are just the left-overs from the banquets of high mass stars”.

The star sigma Orionis is 3 million years old and has a high temperature: its surface temperature is 30,000K five times hotter than that of the Sun. This very high temperature makes the star have a blueish colour, in contrast to less massive stars which have reddish colours. “In 2011” –remembers Caballero- “we showed that sigma Orionis is really a multiple star consisting of six stars instead as five, as previously thought: two of them are very high mass stars, which are very close together, rotating mutually around each other with an orbital period of some 143 days. A third star, also massive, is orbiting at 100 astronomical units (100 times the distance from the Earth to the Sun) from the other two, and rotates with a much longer period, of some 157 years. The cluster is completed with three other stars, a little cooler and less massive, as well as numerous stellar remnants”.

Now these researchers, together with 11 others from Spain, Germany, Chile, the USA, Belgium, and Hungary, have observed in more detail the central trio of these stars, (sigma Ori Aa, sigma Ori Ab, and sigma Ori B), and have measured their physical parameters with unprecedented accuracy. “ The period of the closest pair, of around 143 days, has now been determined with an uncertainty of only 11 minutes” –points out Simón-Díaz-,” which makes it feasible to programme specific observations at certain phases, for example with X-ray telescopes in space at periastron, the point where the two central stars are separated by their smallest distance”.

“Gobbler” stars

The study has also allowed us to determine very accurately the masses of the three stars using different methods. “The sum of the masses of the trio is bigger than 40 times the mass of the Sun”, emphasizes Simón-Díaz. “These observations, together with interferometric observations now in progress, are an excellent input to theoretical modes which aim at explaining the structure and the fate of these “gobbler stars”.

“We have also measured” –adds Caballero- “the rate of emission of high energy photons from the trio. These photons, emitted by sigma Orionis Aa, Ab, and B and those which ‘comb the mane’ of the Horsehead Nebula, and announce the start of a new banquet of high mass stars in the region. In just a few million years, when sigma Orionis Aa (and perhaps Ab) explodes as a supernova, and cleans out the region around it, a large number of smaller, cooler stars will continue to exist, as well as a few large, massive, very hot stars, which at the present moment are inside the dense clouds near the Horsehead Nebula”.


Referente:

Simón-Díaz et al. (2015, ApJ 799, 169)
Contact: 

Instituto de Astrofísica de Andalucía (IAA-CSIC)
Unidad de Divulgación y Comunicación
Silbia López de Lacalle
- sll@iaa.es - 958230532
http://www.iaa.es
http://www-divulgacion.iaa.es


Monday, January 26, 2015

A Recoiling, Supermassive Black Hole

The galaxy at the center of this image from the Hubble Space Telescope contains an X-ray source, CID-42, which is suspected of being the merged remnant of a pair of supermassive black holes and of being ejected from the host galaxy at a speed of several million miles per hour. Credit: X-ray: NASA/CXC/SAO/F.Civano et al; Optical: NASA/STScI; Optical (wide field): CFHT, NASA/STScI 


When galaxies collide, the central supermassive black holes that reside at their cores will end up orbiting one another in a binary pair, at least according to current simulations. Einstein's general theory of relativity predicts that masses in a binary system should radiate gravitational waves, analogous to the way that accelerating electrical charges radiate electromagnetic waves but very much weaker.

As they radiate away their energy in these waves, orbiting black holes will gradually come closer together until eventually they merge in a coalescence event that is expected to emit a strong burst of gravitational waves. Relativity predicts that the gravitational radiation from black hole coalescence will be preferentially emitted in one direction that depends on the spin- and mass-ratios of the two black holes. In order to conserve momentum, therefore, the newly formed single supermassive black hole will recoil. Indeed, recoiling supermassive black holes are predicted to be one of the key observable signatures of such binary mergers. As they speed away from the center of the galaxy, they are expected to carry along with them their local environments (the discs and hot gas regions).

Amazingly, a few of these bizarre, recoiling candidates have apparently been serendipitously spotted (they are so far only candidates because their character is not yet confirmed). One of them is an X-ray source known as CID-42, which the Hubble Space Telescope resolves into two bright components only a few thousand light-years apart (a relatively small distance in galactic terms). CfA astronomers Francesca Civano, Xiawei Wang, Avi Loeb, and Martin Elvis, together with their colleagues, used the Very Large Array radio facility to study the radio emission emitted by charged particles accelerated by the black holes in CID-42, and analyzed their data together with that from other facilities in an effort to confirm it as a recoil object. They find that all of the radio emission can be attributed to one of the two bright components, which also is the source of the X-ray emission. This source, their analysis concludes (although still not unequivocally), could indeed be a long-sought example of a recoiling black hole. The new research is a major step towards confirming the existence of these exotic objects, but further observations are still needed.

Reference(s): 

 "New Insights from Deep VLA Data on the Potentially Recoiling Black Hole CID-42 in the COSMOS Field," Mladen Novak, Vernesa Smolcic, Francesca Civano, Marco Bondi, Paolo Ciliegi, Xiawei Wang, Abraham Loeb, Julie Banfield, Stephen Bourke, Martin Elvis, Gregg Hallinan, Huib T. Intema, Hans-Rainer Klockner, Kunal Mooley and Felipe Navarrete, MNRAS, 447, 2282, 2015.




Friday, January 23, 2015

Dust filaments of NGC 4217

Credit: ESA/Hubble & NASA
Acknowledgement: R. Schoofs

In this image the NASA/ESA Hubble Space Telescope takes a close look at the spiral galaxy NGC 4217, 60 million light-years away. The galaxy is seen almost perfectly edge on and is a perfect candidate for studying the nature of extraplanar dust structures — the patterns of gas and dust above and below the plane on the galaxy, seen here as brown wisps coming off NGC 4217.

These tentacle-like filaments are visible in the Hubble image only because the contrast with their surroundings is so high. This implies that the structures are denser than their surroundings. The image shows dozens of dust structures some of which reach as far as 7000 light-years away from the central plane. Typically the structures have a length of about 1000 light-years and are about 400 light-years in width.

Some of the dust filaments are round or irregular clouds, others are vertical columns, looplike structures or vertical cones. These structures can help astronomers to identify the mechanisms responsible for the ejection of gas and dust from the galactic plane of spiral galaxies and reveal information on the transport of the interstellar medium to large distances away from galactic discs.

The properties of the observed dust structures in NGC 4217 suggest that the gas and dust was driven out of the midplane of the galaxy by powerful stellar winds resulting from supernovae — explosions that mark the deaths of massive stars.

This image was entered into the Hubble Hidden Treasures competition by contestant Ralf Schoofs.


Source: ESA/Hubble - Space Telescope


Thursday, January 22, 2015

IYL 2015: Chandra Celebrates The International Year of Light

M51, SNR E0519-69.0, MSH 11-62, Cygnus A, RCW 86



The year of 2015 has been declared the International Year of Light (IYL) by the United Nations. Organizations, institutions, and individuals involved in the science and applications of light will be joining together for this yearlong celebration to help spread the word about the wonders of light.

In many ways, astronomy uses the science of light. By building telescopes that can detect light in its many forms, from radio waves on one end of the "electromagnetic spectrum" to gamma rays on the other, scientists can get a better understanding of the processes at work in the Universe.

NASA's Chandra X-ray Observatory explores the Universe in X-rays, a high-energy form of light. By studying X-ray data and comparing them with observations in other types of light, scientists can develop a better understanding of objects likes stars and galaxies that generate temperatures of millions of degrees and produce X-rays.

To recognize the start of IYL, the Chandra X-ray Center is releasing a set of images that combine data from telescopes tuned to different wavelengths of light. From a distant galaxy to the relatively nearby debris field of an exploded star, these images demonstrate the myriad ways that information about the Universe is communicated to us through light.



The images, beginning at the upper left and moving clockwise, are:


M51
Messier 51 (M51):
This galaxy, nicknamed the "Whirlpool," is a spiral galaxy, like our Milky Way, located about 30 million light years from Earth. This composite image combines data collected at X-ray wavelengths by Chandra (purple), ultraviolet by the Galaxy Evolution Explorer (GALEX, blue); visible light by Hubble (green), and infrared by Spitzer (red).


SNR E0519-69.0
SNR E0519-69.0:
When a massive star exploded in the Large Magellanic Cloud, a satellite galaxy to the Milky Way, it left behind an expanding shell of debris called SNR 0519-69.0. Here, multimillion degree gas is seen in X-rays from Chandra (blue). The outer edge of the explosion (red) and stars in the field of view are seen in visible light from Hubble.


MSH 11-62
MSH 11-62:
When X-rays, shown in blue, from Chandra and XMM-Newton are joined in this image with radio data from the Australia Telescope Compact Array (pink) and visible light data from the Digitized Sky Survey (DSS, yellow), a new view of the region emerges. This object, known as MSH 11-62, contains an inner nebula of charged particles that could be an outflow from the dense spinning core left behind when a massive star exploded.


Cygnus A
Cygnus A:
This supernova remnant is the remains of an exploded star that may have been witnessed by Chinese astronomers almost 2,000 years ago. Modern telescopes have the advantage of observing this object in light that is completely invisible to the unaided human eye. This image combines X-rays from Chandra (pink and blue) along with visible emission from hydrogen atoms in the rim of the remnant, observed with the 0.9-m Curtis Schmidt telescope at the Cerro Tololo Inter-American Observatory (yellow).


RCW 86
RCW 86:
This galaxy, at a distance of some 700 million light years, contains a giant bubble filled with hot, X-ray emitting gas detected by Chandra (blue). Radio data from the NSF's Very Large Array (red) reveal "hot spots" about 300,000 light years out from the center of the galaxy where powerful jets emanating from the galaxy's supermassive black hole end. Visible light data (yellow) from both Hubble and the DSS complete this view.


In addition to these newly released images, the Chandra X-ray Center has created a new online repository of images called "Light: Beyond the Bulb" for IYL. This project places astronomical objects in context with light in other fields of science and research.

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

For more information on "Light: Beyond the Bulb," visit the website at http://lightexhibit.org

For more information on the International Year of Light, go to http://www.light2015.org/Home.html


Fast Facts for Whirlpool Galaxy:

Credit: X-ray: NASA/CXC/SAO; UV: NASA/JPL-Caltech; Optical: NASA/STScI; IR: NASA/JPL-Caltech
Scale: Image: is 6 x 10 arcmin across. (About 52,000 x 87,000 light years)
Category: Normal Galaxies & Starburst Galaxies
Coordinates (J2000): RA 13h 29m 52.3s | Dec +47° 11' 54
Constellation: Canes Venatici
Observation Dates: 11 pointings between Mar 2000 and Oct 2012
Observation Time: 232 hours 10 min (9 days 16 hours 10 min)
Obs. IDs: 353, 354, 1622, 3932, 13812-13816, 15496, 15553
Instrument: ACIS
Also Known As: NGC 5194, NGC 5195
Color Code: X-ray (Purple); Ultraviolet (Blue); Optical (Green); Infrared (Red)
Distance Estimate: About 30 million light years


Fast Facts for SNR E0519-69.0:

Credit: X-ray: NASA/CXC/Rutgers/J.Hughes; Optical: NASA/STScI
Scale: Image is 1.5 arcmin across. (about 70 light years)
Category: Normal Galaxies & Starburst Galaxies
Coordinates (J2000): RA 05h 19m 34.90s | Dec -69° 02' 07.30"
Constellation: Dorado
Observation Dates: 4 pointings between Jun 2000 and Feb 2010
Observation Time: 25 hours 16 min (1 day 1 hour 16 min)
Obs. IDs: 118, 11241, 12062, 12063
Instrument: ACIS
Color Code: X-ray (Blue); Optical (Red, Green, Blue)
Distance Estimate: About 160,000 light years


Fast Facts for MSH 11-62:

Credit: X-ray: NASA/CXC/SAO/P.Slane et al; Optical: DSS; Radio: CSIRO/ATNF/ATCA
Scale: Image is 55 arcmin across. (256 light years)
Category: Normal Galaxies & Starburst Galaxies
Coordinates (J2000): RA 11h 11m 52.00s | Dec -60° 39' 12.00"
Constellation: Carina
Observation Dates: 1 pointing in Apr 2002 and 8 between Oct 2013 and Jan 2014
Observation Time: 131 hours 17 min (5 days 11 hours 17 min)
Obs. IDs: 2782, 14822-14824, 16496, 16497, 16512, 16541, 16566
Instrument: ACIS
Color Code: X-ray (Blue); Optical (Yellow); Radio (Pink)
Distance Estimate: About 16,000 light years


Fast Facts for Cygnus A:

Credit: X-ray: NASA/CXC/SAO; Optical: NASA/STScI; Radio: NSF/NRAO/AUI/VLA
Scale: Image is 2.7 arcmin across. (about 550,000 light years)
Category: Normal Galaxies & Starburst Galaxies
Coordinates (J2000): RA 19h 59m 28.30s | Dec +40° 44' 02.00"
Constellation: Cygnus
Observation Dates: 11 pointings between Mar 2000 and Sep 2005
Observation Time: 67 hours 35 min (2 days 19 hours 35min)
Obs. IDs: 359, 360, 1707, 5830, 5831, 6225, 6226, 6228, 6229, 6250, 6252
Instrument: ACIS
Color Code: X-ray: Blue; Optical: Yellow; Radio: Red
Distance Estimate: About 700 million light years


Fast Facts for RCW 86:

Credit: X-ray: NASA/CXC/MIT/D.Castro et al, Optical: NOAO/AURA/NSF/CTIOScale: Image is 19.5 arcmin across. (about 46.5 light years)
Category Normal Galaxies & Starburst Galaxies
Coordinates (J2000): RA 14h 45m 02.30s | Dec -62º 20' 32.00"
Constellation: Circinus
Observation Dates: 3 pointings in Feb, 2013
Observation Time: 28 hours 57 min (1 day 4 hours 57 min )
Obs. IDs: 14890, 15608, 15609
Instrument: ACIS
Also Known As: G315.4-2.1
Color Code: X-ray (Blue and Pink); Optical (Yellow)
Distance Estimate: About 8,200 light years 




Tuesday, January 20, 2015

Three Almost Earth-Size Planets Found Orbiting Nearby Star

This whimsical cartoon shows the three newly discovered extrasolar planets (right) casting shadows on their host star that can been seen as eclipses, or transits, at Earth (left). Earth can be detected by the same effect, but only in the plane of Earth's orbit (the ecliptic). During the K2 mission, many of the extrasolar planets discovered by the Kepler telescope will have this lucky double cosmic alignment that would allow for mutual discovery—if there is anyone on those planets to discover Earth. The three new planets orbiting EPIC 201367065 are just out of alignment; while they are visible from Earth, our solar system is tilted just out of their view.  Credit: K. Teramura, UH IfA. High-resolution version


MAUNA KEA, HI – A team of scientists recently discovered a system of three planets, each just larger than Earth, orbiting a nearby star called EPIC 201367065. The three planets are 1.5-2 times the size of Earth.

The outermost planet orbits on the edge of the so-called “habitable zone,” where the temperature may be just right for liquid water, believed necessary to support life, on the planet’s surface. The paper, “A Nearby M Star with Three Transiting Super-Earths Discovered by K2,” was submitted to the Astrophysical Journal today and is available here.

“The compositions of these newfound planets are unknown, but, there is a very real possibility the outer planet is rocky like Earth,” said Erik Petigura, a University of California, Berkeley graduate student who spent a year visiting the UH Institute for Astronomy. “If so, this planet could have the right temperature to support liquid water oceans.”

The planets were confirmed by the NASA Infrared Telescope Facility (IRTF) and the W. M. Keck Observatory in Hawaii as well as telescopes in California and Chile.

“Keck's contribution to this discovery was vital,” said Andrew Howard, a University of Hawaii astronomer on the team. “The adaptive optics image from NIRC2 showed the star hosting these three planets is a single star, not a binary. It showed that the planets are real and not an artifact of some masquerading multi-star system.”

Due to the competitive state of planet finding, and the fact that time on the twin Keck telescopes are scheduled months in advance, the team asked UC Berkeley Astronomer, Imke de Pater to gather some data during her scheduled run. 

“The collegiality of the Keck Observatory community is just wonderful,” Howard said. “Imke took time away from her own science observations to get us images of this system, all on a couple hours’ notice.”

The new discovery paves the way for studies of the atmosphere of a warm planet nearly the size of Earth. 

“We’ve learned in the past year that planets the size and temperature of Earth are common in our Milky Way galaxy,” Howard said. “We also discovered some Earth-size planets that appear to be made of the same materials as our Earth, mostly rock and iron.”

The astronomers next hope to determine what elements are in the planets’ atmospheres. If these warm, nearly Earth-size planets have thick, hydrogen-rich atmospheres, there is not much chance for life.

“A thin atmosphere made of nitrogen and oxygen has allowed life to thrive on Earth. But nature is full of surprises. Many extrasolar planets discovered by the Kepler Mission are enveloped by thick, hydrogen-rich atmospheres that are probably incompatible with life as we know it,” said Ian Crossfield, the University of Arizona astronomer who led the study.

The discovery is all the more remarkable because Kepler is now hobbled by the loss of two reaction wheels that kept it pointing at a fixed spot in space. Kepler, launched in 2009, was reborn in 2014 as “K2” with a clever strategy of pointing the telescope in the plane of the Earth’s orbit to stabilize the spacecraft. Kepler is back to mining the cosmos for planets by searching for eclipses, or transits, as planets orbit in front of their host stars and periodically block some of the starlight.

“I was devastated when Kepler was crippled by a hardware failure,” Petigura added. “It’s a testament to the ingenuity of NASA engineers and scientists that Kepler can still do great science.”

Kepler sees only a small fraction of the planetary systems in its gaze, those with orbital planes aligned edge-on to our view from Earth. Planets with large orbital tilts are simply missed by Kepler.

“It’s remarkable that the Kepler telescope is now pointed in the ecliptic, the plane that Earth sweeps out as it orbits the Sun,” Fulton explains. “This means that some of the planets discovered by K2 will have orbits lined up with Earth’s, a celestial coincidence that allows Kepler to see the alien planets, and Kepler-like telescopes in those very planetary systems (if there are any) to discover Earth.”

“Here’s looking at you, looking at me,” said Howard.

In addition to Howard and Petigura, UH graduate students Benjamin Fulton and Kimberly Aller, and UH astronomer Michael Liu were among the two dozen scientists who contributed to the study.

The W. M. Keck Observatory operates the largest, most scientifically productive telescopes on Earth. The two, 10-meter optical/infrared telescopes near the summit of Mauna Kea on the Island of Hawaii feature a suite of advanced instruments including imagers, multi-object spectrographs, high-resolution spectrographs, integral-field spectrographs and world-leading laser guide star adaptive optics systems. 

NIRC2 (the Near-Infrared Camera, second generation) works in combination with the Keck II adaptive optics system to obtain very sharp images at near-infrared wavelengths, achieving spatial resolutions comparable to or better than those achieved by the Hubble Space Telescope at optical wavelengths. NIRC2 is probably best known for helping to provide definitive proof of a central massive black hole at the center of our galaxy. Astronomers also use NIRC2 to map surface features of solar system bodies, detect planets orbiting other stars, and study detailed morphology of distant galaxies.

Keck Observatory is a private 501(c) 3 non-profit organization and a scientific partnership of the California Institute of Technology, the University of California and NASA.


Media Contact:

Steve Jefferson
Communications Officer
W. M. Keck Observatory
808.881.3827

sjefferson@keck.hawaii.edu



Monday, January 19, 2015

Venus Express snaps swirling vortex

Venus Express snaps swirling vortex 
Copyright ESA/VIRTIS/INAF-IASF/Obs. de Paris-LESIA/Univ. Oxford

Close-up view of south polar vortex (video)
Copyright: ESA/VIRTIS/INAF-IASF/Obs. de Paris-LESIA


This ghostly puff of smoke is actually a mass of swirling gas and cloud at Venus’ south pole, as seen by the Visible and Infrared Thermal Imaging Spectrometer (VIRTIS) aboard ESA’s Venus Express spacecraft.

Venus has a very choppy and fast-moving atmosphere – although wind speeds are sluggish at the surface, they reach dizzying speeds of around 400 km/h at the altitude of the cloud tops, some 70 km above the surface. At this altitude, Venus’ atmosphere spins round some 60 times faster than the planet itself. This is very rapid; even Earth’s fastest winds move at most about 30% of our planet’s rotation speed. Quick-moving Venusian winds can complete a full lap of the planet in just four Earth days.

Polar vortices form because heated air from equatorial latitudes rises and spirals towards the poles, carried by the fast winds. As the air converges on the pole and then sinks, it creates a vortex much like that found above the plughole of a bath. In 1979, the Pioneer Venus orbiter spotted a huge hourglass-shaped depression in the clouds, some 2000 km across, at the centre of the north polar vortex.

However, other than brief glimpses from the Pioneer Venus and Mariner 10 missions in the 1970s, Venus’ south pole had not been seen in detail until ESA’s Venus Express first entered orbit in April 2006.

One of Venus Express’ first discoveries, made during its very first orbit, was confirming the existence of a huge atmospheric vortex circulation at the south pole with a shape matching the one glimpsed at the north pole.

This south polar vortex is a turbulent mix of warming and cooling gases, all surrounded by a ‘collar’ of cool air. Follow-up Venus Express observations in 2007, including this image, showed that the core of the vortex changes shape on a daily basis. Just four hours after this image the vortex looked very different and a day later it had morphed into a squashed shape unrecognisable from the eye-like structure here.

A video of the vortex, made from 10 images taken over a period of five hours, can be seen here. The vortex rotates with a period of around 44 hours.

The swirling region shown in this VIRTIS image is about 60 km above the planet’s surface. Venus’ south pole is located just up and to the left of the image centre, slightly above the wispy ‘eye’ itself.

This image was obtained on 7 April 2007 at a wavelength of 5.02 micrometres. It shows thermal-infrared emission from the cloud tops; brighter regions like the ‘eye’ of the vortex are at lower altitude and therefore hotter.


Links



Source: ESA


The Cosmic Seeds of Black Holes

 
Simulation of the collapse of gas in the very early universe into a small black hole, the first step in producing a more massive black hole that will become the seed for the future development of a galaxy. (The scale of the image is 20 au; one au - astronomical unit - is the average distance of the Earth from the Sun. Credit: Becerra


Supermassive black holes with millions or billions of solar-masses of material are found at the nuclei of most galaxies. During the embryonic stages of these galaxies they are thought to play an important role, acting as seeds around which material collected. During the later lifetime of galaxies they can power dramatic outflowing jets of material (among other phenomena) as infalling dust and gas accretes onto the disks that typically surround them. These active, later phases of supermassive black holes can result in turning galaxies into an extremely bright objects like quasars, whose luminosities allow them to be seen at cosmic distances. In fact, quasars have recently been detected from eras less than a billion years after the big bang.

But where do all these black holes come from – especially the ones present in the early universe!? The explosive death of massive stars, one nominal route, can take many hundreds of millions of years while the star itself coalesces from ambient gas and then evolves, after which material must be added to the black hole seed to grow it into a supermassive monster. It is not clear that there is enough time in the early universe for this to happen. A second method has been proposed for these cosmic seeds, the direct collapse of primordial gas into seedlings that are much more massive – about ten thousand solar-masses - than are those present in stellar ashes.

Computer simulations have struggled for years to predict what happens in direct collapse, with mixed successes. CfA astronomers Fernando Becerra, Thomas Greif, and Lars Hernquist, and a colleague, have just published the most detailed 3-D simulation of the process in the early universe with an amazingly fine spatial scale precision -- as small as the solar-system -- and spanning a factor of over ten trillion in size and twenty orders of magnitude (a factor of one hundred million trillion) in gas density. They find that a small protostellar-like core of only 0.1 solar-masses can develop in only a few years from a suitable environment and then can grow into a supermassive black hole in only millions of years. In particular, they find that fragmentation, which had been predicted to disrupt the growth of these seedlings, is not a serious problem. Their result is a significant step towards explaining the cosmic origins of the seeds of galaxies.


Reference(s):

"Formation of Massive Protostars in Atomic Cooling Haloes," Fernando Becerra, Thomas H. Greif, Volker Springel, and Lars E. Hernquist, MNRAS 446, 2380, 2015.




Friday, January 16, 2015

The third way of galaxies

Credit: ESA/Hubble & NASA
Acknowledgement: J. Barrington


The subject of this image is NGC 6861, a galaxy discovered in 1826 by the Scottish astronomer James Dunlop. Almost two centuries later we now know that NGC 6861 is the second brightest member of a group of at least a dozen galaxies called the Telescopium Group — otherwise known as the NGC 6868 Group — in the small constellation of Telescopium (The Telescope).

This NASA/ESA Hubble Space Telescope view shows some important details of NGC 6861. One of the most prominent features is the disc of dark bands circling the centre of the galaxy. These dust lanes are a result of large clouds of dust particles obscuring the light emitted by the stars behind them.

Dust lanes are very useful for working out whether we are seeing the galaxy disc edge-on, face-on or, as is the case for NGC 6861, somewhat in the middle. Dust lanes like these are typical of a spiral galaxy. The dust lanes are embedded in a white oval shape, which is made up of huge numbers of stars orbiting the centre of the galaxy. This oval is, rather puzzlingly, typical of an elliptical galaxy.

So which is it — spiral or elliptical? The answer is neither! NGC 6861 does not belong to either the spiral or the elliptical family of galaxies. It is a lenticular galaxy, a family which has features of both spirals and ellipticals.

The relationships between these three kinds of galaxies are not yet well understood. A lenticular galaxy could be a faded spiral that has run out of gas and lost its arms, or the result of two galaxies merging. Being part of a group increases the chances for galactic mergers, so this could be the case for NGC 6861.

A version of this image was entered into the Hubble’s Hidden Treasures image processing competition by contestant Josh Barrington.


Source:  ESA/Hubble - Space Telescope


Thursday, January 15, 2015

A twist on planetary origins

An artist’s rendering of a protoplanetary impact. Early in the impact, molten jetted material is ejected at a high velocity and breaks up to form chondrules, the millimeter-scale, formerly molten droplets found in most meteorites. These droplets cool and solidify over hours to days. Image: NASA/California Institute of Technology

New study finds meteorites were byproducts of planetary formation, not building blocks

Meteors that have crashed to Earth have long been regarded as relics of the early solar system. These craggy chunks of metal and rock are studded with chondrules — tiny, glassy, spherical grains that were once molten droplets. Scientists have thought that chondrules represent early kernels of terrestrial planets: As the solar system started to coalesce, these molten droplets collided with bits of gas and dust to form larger planetary precursors.

However, researchers at MIT and Purdue University have now found that chondrules may have played less of a fundamental role. Based on computer simulations, the group concludes that chondrules were not building blocks, but rather byproducts of a violent and messy planetary process.

The team found that bodies as large as the moon likely existed well before chondrules came on the scene. In fact, the researchers found that chondrules were most likely created by the collision of such moon-sized planetary embryos: These bodies smashed together with such violent force that they melted a fraction of their material, and shot a molten plume out into the solar nebula. Residual droplets would eventually cool to form chondrules, which in turn attached to larger bodies — some of which would eventually impact Earth, to be preserved as meteorites.

Brandon Johnson, a postdoc in MIT’s Department of Earth, Atmospheric and Planetary Sciences, says the findings revise one of the earliest chapters of the solar system.

“This tells us that meteorites aren’t actually representative of the material that formed planets — they’re these smaller fractions of material that are the byproduct of planet formation,” Johnson says. “But it also tells us the early solar system was more violent than we expected: You had these massive sprays of molten material getting ejected out from these really big impacts. It’s an extreme process.”

Johnson and his colleagues, including Maria Zuber, the E.A. Griswold Professor of Geophysics and MIT’s vice president for research, have published their results this week in the journal Nature.


High-velocity molten rock

To get a better sense of the role of chondrules in a fledgling solar system, the researchers first simulated collisions between protoplanets — rocky bodies between the size of an asteroid and the moon. The team modeled all the different types of impacts that might occur in an early solar system, including their location, timing, size, and velocity. They found that bodies the size of the moon formed relatively quickly, within the first 10,000 years, before chondrules were thought to have appeared.

Johnson then used another model to determine the type of collision that could melt and eject molten material. From these simulations, he determined that a collision at a velocity of 2.5 kilometers per second would be forceful enough to produce a plume of melt that is ejected out into space — a phenomenon known as impact jetting.

“Once the two bodies collide, a very small amount of material is shocked up to high temperature, to the point where it can melt,” Johnson says. “Then this really hot material shoots out from the collision point.”

The team then estimated the number of impact-jetting collisions that likely occurred in a solar system’s first 5 million years — the period of time during which it’s believed that chondrules first appeared. From these results, Johnson and his team found that such collisions would have produced enough chondrules in the asteroid belt region to explain the number that have been detected in meteorites today.


Falling into place

To go a step further, the researchers ran a third simulation to calculate chondrules’ cooling rate. Previous experiments in the lab have shown that chondrules cool down at a rate of 10 to 1,000 kelvins per hour — a rate that would produce the texture of chondrules seen in meteorites. Johnson and his colleagues used a radiative transfer model to simulate the impact conditions required to produce such a cooling rate. They found that bodies colliding at 2.5 kilometers per second would indeed produce molten droplets that, ejected into space, would cool at 10 to 1,000 kelvins per hour.

“Then I had this ‘Eureka!’ moment where I realized that jetting during these really big impacts could possibly explain the formation of chondrules,” Johnson says. “It all fell into place.”

Going forward, Johnson plans to look into the effects of other types of impacts. The group has so far modeled vertical impacts — bodies colliding straight-on. Johnson predicts that oblique impacts, or collisions occurring at an angle, may be even more efficient at producing molten plumes of chondrules. He also hopes to explore what happens to chondrules once they are launched into the solar nebula.

“Chondrules were long viewed as planetary building blocks,” Zuber notes. “It’s ironic that they now appear to be the remnants of early protoplanetary collisions.”

Fred Ciesla, associate professor of planetary science at the University of Chicago, says the findings may reclassify chondrites, a class of meteorites that are thought to be examples of the original material from which planets formed.

“This would be a major shift in how people think about our solar system,” says Ciesla, who did not contribute to the research. “If this finding is correct, then it would suggest that chondrites are not good analogs for the building blocks of the Earth and other planets. Meteorites as a whole are still important clues about what processes occurred during the formation of the Solar System, but which ones are the best analogs for what the planets were made out of would change.”

This research was funded in part by NASA.


 
Source:  MIT News