Monday, November 24, 2014

NASA's Swift Mission Probes an Exotic Object: ‘Kicked’ Black Hole or Mega Star?

Zoom into Markarian 177 and SDSS1133 and see how they compare with a simulated galaxy collision. When the central black holes in these galaxies combine, a "kick" launches the merged black hole on a wide orbit taking it far from the galaxy's core. Related multimedia from NASA Goddard's Scientific Visualization Studio

The dwarf galaxy Markarian 177 (center) and its unusual source SDSS1133 (blue) lie 90 million light-years away. The galaxies are located in the bowl of the Big Dipper, a well-known star pattern in the constellation Ursa Major. Image Credit: Sloan Digital Sky Survey

Using the Keck II telescope in Hawaii, researchers obtained high-resolution images of Markarian 177 and SDSS1133 using a near-infrared filter. Twin bright spots in the galaxy's center are consistent with recent star formation, a disturbance that hints this galaxy may have merged with another. Image Credit: Credit: W. M. Keck Observatory/M. Koss (ETH Zurich) et al. Unlabeled version

SDSS1133 (bright spot, lower left) has been a persistent source for more than 60 years. This sequence of archival astronomical imagery, taken through different instruments and filters, shows that the source is detectable in 1950 and brightest in 2001. Image Credit: NASA's Goddard Space Flight Center/M. Koss (ETH Zurich)

An international team of researchers analyzing decades of observations from many facilities, including NASA's Swift satellite, has discovered an unusual source of light in a galaxy some 90 million light-years away.

The object's curious properties make it a good match for a supermassive black hole ejected from its home galaxy after merging with another giant black hole. But astronomers can't yet rule out an alternative possibility. The source, called SDSS1133, may be the remnant of a massive star that erupted for a record period of time before destroying itself in a supernova explosion.

"With the data we have in hand, we can't yet distinguish between these two scenarios," said lead researcher Michael Koss, an astronomer at ETH Zurich, the Swiss Federal Institute of Technology. "One exciting discovery made with NASA's Swift is that the brightness of SDSS1133 has changed little in optical or ultraviolet light for a decade, which is not something typically seen in a young supernova remnant."

In a study published in the Nov. 21 edition of Monthly Notices of the Royal Astronomical Society, Koss and his colleagues report that the source has brightened significantly in visible light during the past six months, a trend that, if maintained, would bolster the black hole interpretation. To analyze the object in greater detail, the team is planning ultraviolet observations with the Cosmic Origins Spectrograph aboard the Hubble Space Telescope in October 2015.

Whatever SDSS1133 is, it's persistent. The team was able to detect it in astronomical surveys dating back more than 60 years.

The mystery object is part of the dwarf galaxy Markarian 177, located in the bowl of the Big Dipper, a well-known star pattern within the constellation Ursa Major. Although supermassive black holes usually occupy galactic centers, SDSS1133 is located at least 2,600 light-years from its host galaxy's core.

In June 2013, the researchers obtained high-resolution near-infrared images of the object using the 10-meter Keck II telescope at the W. M. Keck Observatory in Hawaii. They reveal the emitting region of SDSS1133 is less than 40 light-years across and that the center of Markarian 177 shows evidence of intense star formation and other features indicating a recent disturbance.

"We suspect we're seeing the aftermath of a merger of two small galaxies and their central black holes," said co-author Laura Blecha, an Einstein Fellow in the University of Maryland's Department of Astronomy and a leading theorist in simulating recoils, or "kicks," in merging black holes. "Astronomers searching for recoiling black holes have been unable to confirm a detection, so finding even one of these sources would be a major discovery."

The collision and merger of two galaxies disrupts their shapes and results in new episodes of star formation. If each galaxy possesses a central supermassive black hole, they will form a bound binary pair at the center of the merged galaxy before ultimately coalescing themselves.

Merging black holes release a large amount of energy in the form of gravitational radiation, a consequence of Einstein's theory of gravity. Waves in the fabric of space-time ripple outward in all directions from accelerating masses. If both black holes have equal masses and spins, their merger emits gravitational waves uniformly in all directions. More likely, the black hole masses and spins will be different, leading to lopsided gravitational wave emission that launches the black hole in the opposite direction.

The kick may be strong enough to hurl the black hole entirely out of its home galaxy, fating it to forever drift through intergalactic space. More typically, a kick will send the object into an elongated orbit. Despite its relocation, the ejected black hole will retain any hot gas trapped around it and continue to shine as it moves along its new path until all of the gas is consumed.

If SDSS1133 isn't a black hole, then it might have been a very unusual type of star known as a Luminous Blue Variable (LBV). These massive stars undergo episodic eruptions that cast large amounts of mass into space long before they explode. Interpreted in this way, SDSS1133 would represent the longest period of LBV eruptions ever observed, followed by a terminal supernova explosion whose light reached Earth in 2001.

The nearest comparison in our galaxy is the massive binary system Eta Carinae, which includes an LBV containing about 90 times the sun's mass. Between 1838 and 1845, the system underwent an outburst that ejected at least 10 solar masses and made it the second-brightest star in the sky. It then followed up with a smaller eruption in the 1890s.

In this alternative scenario, SDSS1133 must have been in nearly continual eruption from at least 1950 to 2001, when it reached peak brightness and went supernova. The spatial resolution and sensitivity of telescopes prior to 1950 were insufficient to detect the source. But if this was an LBV eruption, the current record shows it to be the longest and most persistent one ever observed. An interaction between the ejected gas and the explosion's blast wave could explain the object's steady brightness in the ultraviolet.

Whether it's a rogue supermassive black hole or the closing act of a rare star, it seems astronomers have never seen the likes of SDSS1133 before.  Source: NASA's Swift Mission


Related Links:

Download HD video and print-resolution images from NASA Goddard's Scientific Visualization Studio: http://svs.gsfc.nasa.gov/goto?10082

Paper: "SDSS1133: an unusually persistent transient in a nearby dwarf galaxy": http://mnras.oxfordjournals.org/content/445/1/515

Simulations Uncover 'Flashy' Secrets of Merging Black Holes (09.27.12): http://www.nasa.gov/topics/universe/features/black-hole-secrets.html

Giant Black Hole Kicked Out of Home Galaxy (06.04.2012):  http://www.nasa.gov/mission_pages/chandra/news/H-12-182.html


Francis Reddy
NASA's Goddard Space Flight Center, Greenbelt, Md.




Friday, November 21, 2014

A spiral in a furnace

Credit:  ESA/Hubble & NASA

This new Hubble image is a snapshot of NGC 986 — a barred spiral galaxy discovered in 1828 by James Dunlop. This close-up view of the galaxy was captured by Hubble’s Wide Field and Planetary Camera 2 (WFPC2).

NGC 986 is found in the constellation of Fornax (The Furnace), located in the southern sky. NGC 986 is a bright, 11th-magnitude galaxy sitting around 56 million light-years away, and its golden centre and barred swirling arms are clearly visible in this image.

Barred spiral galaxies are spiral galaxies with a central bar-shaped structure composed of stars. NGC 986 has the characteristic S-shaped structure of this type of galactic morphology. Young blue stars can be seen dotted amongst the galaxy’s arms and the core of the galaxy is also aglow with star formation.

To the top right of this image the stars appear a little fuzzy. This is because a gap in the Hubble data was filled in with data from ground-based telescopes. Although the view we see in this filled in patch is accurate, the resolution of the stars is no match for Hubble’s clear depiction of the spiral galaxy.


Source:  ESA/Hubble - Space Telescope


Thursday, November 20, 2014

The riddle of the missing stars

Four globular clusters in Fornax

Four globular clusters in Fornax — annotated

Globular cluster Fornax 1

Globular cluster Fornax 2

Globular cluster Fornax 3

Globular cluster Fornax 5

Fornax galaxy with four globular clusters marked

Fornax dwarf galaxy


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

Videos

 
Hubblecast 80: The riddle of the missing stars
Hubblecast 80: The riddle of the missing stars

Hubble and the sunrise over Earth
Hubble and the sunrise over Earth

Globular cluster in 3D
Globular cluster in 3D

Structure of a globular cluster
Structure of a globular cluster


Hubble observations cast further doubt on how globular clusters formed

Thanks to the NASA/ESA Hubble Space Telescope, some of the most mysterious cosmic residents have just become even more puzzling. New observations of globular clusters in a small galaxy show they are very similar to those found in the Milky Way, and so must have formed in a similar way. One of the leading theories on how these clusters form predicts that globular clusters should only be found nestled in among large quantities of old stars. But these old stars, though rife in the Milky Way, are not present in this small galaxy, and so, the mystery deepens.

Globular clusters — large balls of stars that orbit the centres of galaxies, but can lie very far from them — remain one of the biggest cosmic mysteries. They were once thought to consist of a single population of stars that all formed together. However, research has since shown that many of the Milky Way's globular clusters had far more complex formation histories and are made up of at least two distinct populations of stars.

Of these populations, around half the stars are a single generation of normal stars that were thought to form first, and the other half form a second generation of stars, which are polluted with different chemical elements. In particular, the polluted stars contain up to 50-100 times more nitrogen than the first generation of stars.

The proportion of polluted stars found in the Milky Way's globular clusters is much higher than astronomers expected, suggesting that a large chunk of the first generation star population is missing. A leading explanation for this is that the clusters once contained many more stars but a large fraction of the first generation stars were ejected from the cluster at some time in its past.

This explanation makes sense for globular clusters in the Milky Way, where the ejected stars could easily hide among the many similar, old stars in the vast halo, but the new observations, which look at this type of cluster in a much smaller galaxy, call this theory into question.

Astronomers used Hubble's Wide Field Camera 3 (WFC3) to observe four globular clusters in a small nearby galaxy known as the Fornax Dwarf Spheroidal galaxy [1].

"We knew that the Milky Way's clusters were more complex than was originally thought, and there are theories to explain why. But to really test our theories about how these clusters form we needed to know what happened in other environments," says Søren Larsen of Radboud University in Nijmegen, the Netherlands, lead author of the new paper. "Before now we didn’t know whether globular clusters in smaller galaxies had multiple generations or not, but our observations show clearly that they do!"

The astronomers' detailed observations of the four Fornax clusters show that they also contain a second polluted population of stars [2] and indicate that not only did they form in a similar way to one another, their formation process is also similar to clusters in the Milky Way. Specifically, the astronomers used the Hubble observations to measure the amount of nitrogen in the cluster stars, and found that about half of the stars in each cluster are polluted at the same level that is seen in Milky Way's globular clusters.

This high proportion of polluted second generation stars means that the Fornax globular clusters' formation should be covered by the same theory as those in the Milky Way.

Based on the number of polluted stars in these clusters they would have to have been up to ten times more massive in the past, before kicking out huge numbers of their first generation stars and reducing to their current size. But, unlike the Milky Way, the galaxy that hosts these clusters doesn't have enough old stars to account for the huge number that were supposedly banished from the clusters.

"If these kicked-out stars were there, we would see them — but we don't!" explains Frank Grundahl of Aarhus University in Denmark, co-author on the paper. "Our leading formation theory just can't be right. There's nowhere that Fornax could have hidden these ejected stars, so it appears that the clusters couldn't have been so much larger in the past."

This finding means that a leading theory on how these mixed generation globular clusters formed cannot be correct and astronomers will have to think once more about how these mysterious objects, in the Milky Way and further afield, came to exist.

The new work is detailed in a paper published today, 20 November 2014, in The Astrophysical Journal.


Notes

[1] The Milky Way’s gravity keeps Fornax orbiting around us as a satellite galaxy.

[2] The clusters studied were named Fornax 1, 2, 3, and 5. Fornax 1, 3, and 5 are made up of approximately 40% first generation stars to 60% polluted second generation ones, while Fornax 2 contains around 60% first generation and 40% second generation.


Notes for editors

The Hubble Space Telescope is a project of international cooperation between ESA and NASA.

The international team of astronomers in this study consists of S. Larsen (Radboud University, the Netherlands), J. P Brodie (University of California, USA), F. Grundahl (Aarhus University, Denmark), and J. Strader (Michigan State University, USA).


More information

Image credit: NASA, ESA, S. Larsen (Radboud University, the Netherlands)


Links


Contacts

Søren Larsen
Radboud University
Nijmegen, Netherlands
Tel: +31 (0)24 365 2806
Email: s.larsen@astro.ru.nl

Frank Grundahl
Aarhus University
Aarhus, Denmark
Tel: +45 21 31 43 67
Email: fgj@phys.au.dk

Georgia Bladon
ESA/Hubble, Public Information Officer
Garching bei München, Germany
Cell: +44 7816291261
Email: gbladon@partner.eso.org




Subaru Telescope Detects Sudden Appearance of Galaxies in the Early Universe

Figure 1: Color composite images of seven LAEs found in this study as they appeared 13.1 billion years ago. This represents the combination of three filter images from Subaru Telescope. Red objects between two white lines are the LAEs. The LAEs of 13.1 billion years ago have a quite red color due to the effects of cosmic expansion on their component wavelengths of light. (Credit: ICRR, University of Tokyo)

Figure 2: This shows evolution of the Lyman-alpha luminosities of the galaxies. The yellow circle at 1 billion years after the Big Bang is used for normalization. The yellow circles come from previous studies, and the yellow dashed line shows the expected evolutionary trend of the luminosity. The current finding is shown by a red circle, and we can see that the galaxies appear suddenly when the universe was 700 million years old. This indicates that the neutral hydrogen fog was suddenly cleared, allowing the galaxies to shine out, as indicated by the backdrop shown for scale and illustration. Click here to see the diagram without the labels inside. (Credit: ICRR, University of Tokyo; Hubble Space Telescope/NASA/ESA)

A team of astronomers using the Subaru Telescope's Suprime-Cam to perform the Subaru Ultra-Deep Survey for Lyman-alpha Emitters have looked back more than 13 billion years to find 7 early galaxies that appeared quite suddenly within 700 million years of the Big Bang (Note 1). The team, led by graduate student Akira Konno and Dr. Masami Ouchi (Associate Professor at the University of Tokyo's ICRR) was looking for a specific kind of galaxy called a Lyman-alpha emitter (LAE), to understand the role such galaxies may have played in an event called "cosmic reionization". (Figure 1)

LAE galaxies are illuminated by strong hydrogen excitation (called Lyman-alpha emission) (Note 2). The team's discovery of these LAEs at a distance of 13.1 billion light-years suggests that LAE galaxies appeared rather suddenly in the early universe.

The universe was born in the Big Bang some 13.8 billion years ago. In its earliest epochs, it was filled with a hot "soup" of charged protons and electrons. As the newborn universe expanded, its temperature decreased uniformly. When the universe was 400,000 years old, conditions were cool enough to allow the protons and electrons to bond and form neutral hydrogen atoms. That event is called "recombination" and resulted in a universe filled with a "fog" of these neutral atoms.

Eventually the first stars and galaxies began to form, and their ultraviolet light ionized (energized) the hydrogen atoms, and "divided" the neutral hydrogen into protons and electrons again. As this occurred, the "fog" of neutrals cleared. Astronomers call this event "cosmic reionization" and think that it ended about 12.8 billion years ago (about a billion years after the Big Bang). The timing of this event – when it started and how long it lasted – is one of the big questions in astronomy.

To investigate this cosmic reionization, the Subaru team searched for early LAE galaxies at a distance of 13.1 billion light years. Although Hubble Space Telescope has found more distant LAE galaxies, the discovery of seven such galaxies at 13.1 billion light-years represents a distance milestone for Subaru Telescope (Note 3).
Mr. Konno, the graduate student heading the analysis of the data from the Subaru Telescope pointed out the obstacles that Subaru had to overcome to make the observations. "It is quite difficult to find the most distant galaxies due to the faintness of the galaxies." he said. "So, we developed a special filter to be able to find a lot of faint LAEs. We loaded the filter onto Suprime-Cam and conducted the most distant LAE survey with the integration time of 106 hours."

That extremely long integration time was one of the longest ever performed at Subaru Telescope. It allowed for unprecedented sensitivity and enabled the team to search for as many of the most distant LAEs as possible. According to Konno, the team expected to find several tens of LAEs. Instead they only found seven.

"At first we were very disappointed at this small number," Konno said. "But we realized that this indicates LAEs appeared suddenly about 13 billion years ago. This is an exciting discovery. Figure 2 shows how the luminosities of LAEs changed based on this study. We can see that the luminosities suddenly brightened during the 700-800 million years after the Big Bang. What would cause this?

According to the team's analysis, one reason that LAEs appeared very quickly is cosmic reionization. LAEs in the epoch of cosmic reionization became darker than the actual luminosity due to the presence of the neutral hydrogen fog. In the team's analysis of their observations, they suggest the possibility that the neutral fog filling the universe was cleared about 13.0 billion years ago and LAEs suddenly appeared in sight for the first time."

"However, there are other possibilities to explain why LAEs appeared suddenly," said Dr. Ouchi, who is the principal investigator of this program. "One is that clumps of neutral hydrogen around LAEs disappeared. Another is that LAEs became intrinsically bright. The reason of the intrinsic brightening is that the Lyman-alpha emission is not efficiently produced by the ionized clouds in a LAE due to the significant escape of ionizing photons from the galaxy. In either case, our discovery is an important key to understanding cosmic reionization and the properties of the LAEs in early universe."

Dr. Masanori Iye, who is a representative of the Thirty Meter Telescope (TMT) project of Japan, commented on the observations and analysis. "To investigate which possibility is correct, we will observe with HSC (Hyper Suprime-Cam) on Subaru Telescope, which has a field of view 7 times wider than Suprime-Cam, and TMT currently being built on the summit of Mauna Kea in Hawaii in the future. By these observations, we will clarify the mystery of how galaxies were born and cosmic reionization occurred."

This research is published in the November 20, 2014 issue of The Astrophysical Journal. The work was supported by the Carnegie Observatory, World Premier International Research Center Initiative (WPI Initiative), MEXT, Japan, and KAKENHI (23244025) Grant-in-Aid for Scientific Research (A) through Japan Society for the Promotion of Science (JSPS).

Notes:

  1. The values of the cosmic age and distance in this press release are based on the latest Planck results. Planck observes the cosmic microwave background. A previous press release on this subject used values based on the cosmological parameters derived from the measurements by WMAP (Wilkinson Microwave Anisotropy Probe).
    The parameters used here are H_0=67.1 km/s/Mpc, Ω=0.317, Λ=0.683 instead of the ones used in the past articles at Subaru Telescope's website H_0=71, Ω=0.27, Λ=0.73.
  2. Lyman-alpha emission line is a spectral line of hydrogen, with a wavelength of 121.6 nm (1nm is one billionth of a meter), and is in the ultraviolet portion of the spectrum. Galaxies illuminated by strong Lyman-alpha line are called "Lyman-alpha emitting galaxies" (LAEs).
  3. In previous studies, astronomers have found hundreds of LAEs existing 12.9 billion years ago, which corresponds to the epoch when cosmic reionization finally ended.
 


Wednesday, November 19, 2014

Spooky Alignment of Quasars Across Billions of Light-years

Artist’s impression of mysterious alignment of quasar rotation axes
Simulation of large scale structure

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

Videos

Artist's impression of mysterious alignment of quasar rotation axes
Artist's impression of mysterious alignment of quasar rotation axes


VLT reveals alignments between supermassive black hole axes and large-scale structure

New observations with ESO’s Very Large Telescope (VLT) in Chile have revealed alignments over the largest structures ever discovered in the Universe. A European research team has found that the rotation axes of the central supermassive black holes in a sample of quasars are parallel to each other over distances of billions of light-years. The team has also found that the rotation axes of these quasars tend to be aligned with the vast structures in the cosmic web in which they reside.

Quasars are galaxies with very active supermassive black holes at their centres. These black holes are surrounded by spinning discs of extremely hot material that is often spewed out in long jets along their axes of rotation. Quasars can shine more brightly than all the stars in the rest of their host galaxies put together.

A team led by Damien Hutsemékers from the University of Liège in Belgium used the FORS instrument on the VLT to study 93 quasars that were known to form huge groupings spread over billions of light-years, seen at a time when the Universe was about one third of its current age.

The first odd thing we noticed was that some of the quasars’ rotation axes were aligned with each other — despite the fact that these quasars are separated by billions of light-years,” said Hutsemékers.
The team then went further and looked to see if the rotation axes were linked, not just to each other, but also to the structure of the Universe on large scales at that time.

When astronomers look at the distribution of galaxies on scales of billions of light-years they find that they are not evenly distributed. They form a cosmic web of filaments and clumps around huge voids where galaxies are scarce. This intriguing and beautiful arrangement of material is known as large-scale structure.

The new VLT results indicate that the rotation axes of the quasars tend to be parallel to the large-scale structures in which they find themselves. So, if the quasars are in a long filament then the spins of the central black holes will point along the filament. The researchers estimate that the probability that these alignments are simply the result of chance is less than 1%.

A correlation between the orientation of quasars and the structure they belong to is an important prediction of numerical models of evolution of our Universe. Our data provide the first observational confirmation of this effect, on scales much larger that what had been observed to date for normal galaxies,” adds Dominique Sluse of the Argelander-Institut für Astronomie in Bonn, Germany and University of Liège.

The team could not see the rotation axes or the jets of the quasars directly. Instead they measured the polarisation of the light from each quasar and, for 19 of them, found a significantly polarised signal. The direction of this polarisation, combined with other information, could be used to deduce the angle of the accretion disc and hence the direction of the spin axis of the quasar.

The alignments in the new data, on scales even bigger than current predictions from simulations, may be a hint that there is a missing ingredient in our current models of the cosmos,” concludes Dominique Sluse. 


More Information

This research was presented in a paper entitled “Alignment of quasar polarizations with large-scale structures“, by D. Hutsemékers et al., to appear in the journal Astronomy & Astrophysics on 19 November 2014.

The team is composed of D. Hutsemékers (Institut d’Astrophysique et de Géophysique, Université de Liège, Liège, Belgium), L. Braibant (Liège), V. Pelgrims (Liège) and D. Sluse (Argelander-Institut für Astronomie, Bonn, Germany; Liège).

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 the European partner of a revolutionary astronomical telescope ALMA, the largest astronomical project in existence. ESO is currently planning the 39-metre European Extremely Large optical/near-infrared Telescope, the E-ELT, which will become “the world’s biggest eye on the sky”. 

Links


Contacts:

Damien Hutsemékers
Institut d’Astrophysique et de Géophysique — Université de Liège
Liège, Belgium
Tel: +32 4 366 9760
Email:
hutsemekers@astro.ulg.ac.be

Dominique Sluse
Institut d'Astrophysique et de Géophysique — Université de Liège
Liège, Belgium
Tel: +32 4 366 9797
Email:
dsluse@ulg.ac.be

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


Tuesday, November 18, 2014

Astronomers dissect the aftermath of a Supernova

A labeled panel of images showing different views of Supernova Remnant 1987A
Left Panel: SNR1987A as seen by the Hubble Space Telescope in 2010.Middle Panel: SNR1987A as seen by the Australia Telescope Compact Array (ATCA) in New South Wales and the Atacama Large Millimeter/submillimeter Array (ALMA) in Chile. Right Panel: A computer generated visualisation of the remnant showing the possible location of a Pulsar. Credit: ATCA & ALMA Observations & data - G. Zanardo et al. / HST Image: NASA, ESA, K. France (University of Colorado, Boulder), P. Challis and R. Kirshner (Harvard-Smithsonian Center for Astrophysics). Labeled image - No labels image

A mosaic of images showing the latest observations of Supernova remnant 1987A at radio frequencies to the far infrared. Images below 100 GHz are from observations made with the ATCA telescope (NSW, Australia), and images above 100 GHz are from the ALMA telescope (Chile). The map on the bottom right of the mosaic is obtained by combining five images. This is used to investigate whether there is a pulsar wind nebula inside the remnant. Credit: G. Zanardo, ICRAR-UWA 

An outline of the equatorial ring and inner debris, as seen with the Hubble Space Telescope (green/blue contours), on top of ALMA observations of the remnant at 345 GHz (red/orange, with rendering). Credit: G. Zanardo, ICRAR-UWA

A simulated still showing components of Supernova Remnant 1987A. 

Credit: ICRAR

 
A video compilation showing Supernova Remnant 1987A as seen by the Hubble Space Telescope in 2010, and by radio telescopes located in Australia and Chile in 2012. The piece ends with a computer generated visualisation of the remnant showing the possible location of a Pulsar.

A visualisation showing how Supernova1987A evolves between May of 1989 and July of 2014
Credit: Dr Toby Potter, ICRAR-UWA, Dr Rick Newton, ICRAR-UWA 

In research published today in the Astrophysical Journal, an Australian led team of astronomers has used radio telescopes in Australia and Chile to see inside the remains of a supernova. 

The supernova, known as SN1987A, was first seen by observers in the Southern Hemisphere in 1987 when a giant star suddenly exploded at the edge of a nearby dwarf galaxy called the Large Magellanic Cloud.

In the two and a half decades since then the remnant of Supernova 1987A has continued to be a focus for researchers the world over, providing a wealth of information about one of the Universe’s most extreme events.

PhD Candidate Giovanna Zanardo at The University of Western Australia node of the International Centre for Radio Astronomy Research led the team that used the Atacama Large Millimetre/submillimeter Array (ALMA) in Chile’s Atacama Desert and the Australia Telescope Compact Array (ATCA) in New South Wales to observe the remnant at wavelengths spanning the radio to the far infrared.

"By combining observations from the two telescopes we’ve been able to distinguish radiation being emitted by the supernova’s expanding shock wave from the radiation caused by dust forming in the inner regions of the remnant,” said Giovanna Zanardo of the International Centre for Radio Astronomy Research (ICRAR) in Perth, Western Australia.
"This is important because it means we’re able to separate out the different types of emission we’re seeing and look for signs of a new object which may have formed when the star's core collapsed. It's like doing a forensic investigation into the death of a star."

“Our observations with the ATCA and ALMA radio telescopes have shown signs of something never seen before, located at the centre or the remnant. It could be a pulsar wind nebula, driven by the spinning neutron star, or pulsar, which astronomers have been searching for since 1987. It’s amazing that only now, with large telescopes like ALMA and the upgraded ATCA, we can peek through the bulk of debris ejected when the star exploded and see what’s hiding underneath."

More research published recently in the Astrophysical Journal also attempts to shine a light on another long-standing mystery surrounding the supernova remnant. Since 1992 the radio emission from one side of the remnant has appeared ‘brighter’ than the other.  
In an effort to solve this puzzle, Dr Toby Potter, another researcher from ICRAR’s UWA node has developed a detailed three-dimensional simulation of the expanding supernova shockwave.

“By introducing asymmetry into the explosion and adjusting the gas properties of the surrounding environment, we were able to reproduce a number of observed features from the real supernova such as the persistent one-sidedness in the radio images”, said Dr Toby Potter.

The time evolving model shows that the eastern (left) side of the expanding shock front expands more quickly than the other side, and generates more radio emission than its weaker counterpart. This effect becomes even more apparent as the shock collides into the equatorial ring, as observed in Hubble Space Telescope images of the supernova.

"Our simulation predicts that over time the faster shock will move beyond the ring first. When this happens, the lop-sidedness of radio asymmetry is expected to be reduced and may even swap sides.”

“The fact that the model matches the observations so well means that we now have a good handle on the physics of the expanding remnant and are beginning to understand the composition of the environment surrounding the supernova – which is a big piece of the puzzle solved in terms of how the remnant of SN1987A formed.”


Supporting Multimedia:  

The animation and images below are available for download from this link.


Original publication details:

‘Spectral and Morphological Analysis of the Remnant of Supernova 1987a with ALMA & ATCA’ G. Zanardo, L. Staveley-Smith, R. Indebetouw et al. Published in the in the Astrophysical Journal November 10th, 2014. Pre-print paper available at: http://arxiv.org/abs/1409.7811 and http://iopscience.iop.org/0004-637X/796/2/82 after 8am EST, November 10th.

‘Multi-dimensional simulations of the expanding supernova remnant SN 1987a’ T.M Potter, L Staveley-Smith, B. Reville et al. Published in the Astrophysical Journal October 20th, 2014. Available at http://arxiv.org/abs/1409.4068 and http://iopscience.iop.org/0004-637X/794/2/174.


Further information:

ICRAR is a joint venture between Curtin University and The University of Western Australia with support and funding from the State Government of Western Australia. 

Contact Details:

Dr Giovana Zanardo, ICRAR - UWA 
Ph: +61 8 6488 7765 | M: +61 414 531 081
E: Giovanna.Zanardo@gmail.com

Professor Lister Staveley-Smith, ICRAR Science Director - UWA 
Ph: +61 8 6488 4550 | M: +61 425 212 592
E: Lister.Staveley-smith@icrar.org

Pete Wheeler, ICRAR Media Contact 
Ph: +61 8 6488 7771 | M: +61 423 982 018
E: Pete.Wheeler@icrar.org

David Stacey, UWA Media Manager 
Ph: +61 8 6488 7977 
E: David.Stacey@uwa.edu.au




Monday, November 17, 2014

First observations of the surface of objects from the Oort cloud

CFHT observations of C/2014 S3 and C/1996 O1 (Hale Bopp)
The cometary coma is very strong on the Hale Bopp image while there is a faint hint of a coma on the image of C/2014 S3. 
Images Credits: K. Meech, O. Hainaut, and J. Bauer

Gemini image of C/2013 P2. 
Very little coma is seen despite the proximity to the Sun. 
Credits: K. Meech.

Astronomers from the University of Hawaii in Manoa, ESO, ASIAA in Taiwan, DLR in Berlin and IAA in Bangalore, India announced the discovery of two unusual objects in comet-like orbits but with almost no activity, giving scientists a first look at their surfaces. These results, presented at the annual meeting of the Division of Planetary Sciences of the American Astronomical Society in Tucson, Arizona, are particularly intriguing because the surfaces are different from what astronomers expected, and they give us clues about the movement of material in the early solar system as the planets were assembled.

The two objects, named C/2013 P2 and C/2014 S3, were discovered using Pan-STARRS survey telescope (PS1) on Haleakala, Maui, Hawaii. Both objects have the orbit of a comet coming from the Oort cloud, a spherical halo of comet nuclei in the outer solar system that extends to about 100,000 times the Earth-sun distance, which is known as 1 astronomical unit, or 1 AU. 

Follow-up observations were done on CFHT for both objects and C/2013 P2 was also followed-up with Gemini. Very little coma is seen despite the fact that they are both on a cometary orbit on its closest approach to the Sun. When they get that close to the Sun, comets erupt and produce tails that have been observed across all of humanity's History. In 1996, a team of astronomers at the University of Hawaii used MegaCam on CFHT to observe the center of comet Hale Bopp (C/1995 O1) where it clearly had a massive coma and tail. 

Furthermore, Gemini observations of C/2013 P2 also shows that this object may be an inactive Oort cloud comet. Such objects were hypothesized by Jan Oort back in 1950 when he inferred the existence of what we now call the Oort cloud. Oort suggested that these bodies might have a layer of "volatile frosting" left over from 4.5 billion years of space radiation that disappears after their first pass through the inner solar system. The activity seen in C/2013 P2 is consistent with ice sublimation models but at a level that is one thousand to a million times less than we typically see for comets coming from the Oort cloud. The CFHT data were critical for these models since they need brightness to be sampled over time. 

On the other hand, CFHT images of C/2014 S3 portrais it as a bluer object whose composition is similar to inner solar system asteroid material. This would make C/2014 S3 a unique asteroid that orbits the Sun like a comet. This discovery may help shed some light on some mysteries related to the formation of the solar system. There are several models that try to explain how the planets grew in the early solar system, and some of these predict that material formed close to the sun could have been thrown outward into the outer Solar System and Oort cloud, where it remains today. Bodies like C/2014 S3 could be evidence of this.


Additional information:  Official press release


Information:

Media contact:

Daniel Devost
Director of Science Operations.
Phone number (CFHT): (808)885-3163
devost@cfht.hawaii.edu

Dr. Karen Meech
Institute for Astronomy
+1 720-231-7048 (on MST)

Bin Yang, ESO
byang@eso.org

Henry Hsieh
hhsieh@asiaa.sinica.edu.tw
Cell: +1 808-729-4208 (until 11/22)
+886 0983 436 485 (Taiwan)



Saturday, November 15, 2014

Astronomers Thrilled by Extreme Storms on Uranus

Infrared images of Uranus (1.6 and 2.2 microns) obtained on Aug. 6, 2014, with adaptive optics on the 10-meter Keck II telescope. The white spot is an extremely large storm that was brighter than any feature ever recorded on the planet in the 2.2 micron band. The cloud rotating into view at the lower-right limb grew into the large storm that was seen by amateur astronomers at visible wavelengths. Credit: Imke de Pater (UC Berkeley) & W. M. Keck Observatory images.

Animation showing the movement of the bright spot as Uranus rotated over a two hour period on Oct. 4, 2014. The images were taken at the Pic du Midi telescope in the French Pyrénées. Credit: CLICK ON IMAGE TO SEE ANIMATED GIF Courtesy of Marc Delcroix and F. Colas (S2P).

Optical images of Uranus on Sept. 19 and Oct. 2, showing the dramatic appearance of a bright storm on a planet that normally displays only a diffuse bright polar region. Credit: Courtesy of Anthony Wesley, Murrumbateman, Australia. 

MAUNA KEA, Hawaii — The normally bland face of Uranus has become increasingly stormy, with enormous cloud systems so bright that for the first time ever, amateur astronomers are able to see details in the planet's hazy blue-green atmosphere.

"The weather on Uranus is incredibly active," said Imke de Pater, professor and chair of astronomy at the University of California, Berkeley, and leader of the team that first noticed the activity when observing the planet with adaptive optics on the W. M. Keck Observatory in Hawaii.

"This type of activity would have been expected in 2007, when Uranus's once every 42-year equinox occurred and the sun shined directly on the equator,” noted co-investigator Heidi Hammel of the Association of Universities for Research in Astronomy. “But we predicted that such activity would have died down by now. Why we see these incredible storms now is beyond anybody's guess."

In all, de Pater, Hammel and their team detected eight large storms on Uranus’s northern hemisphere when observing the planet with the Keck Observatory on August 5 and 6. One was the brightest storm ever seen on Uranus at 2.2 microns, a wavelength that senses clouds just below the tropopause, where the pressure ranges from about 300 to 500 mbar, or half the pressure at Earth's surface. The storm accounted for 30 percent of all light reflected by the rest of the planet at this wavelength.

When amateur astronomers heard about the activity, they turned their telescopes on the planet and were amazed to see a bright blotch on the surface of a normally boring blue dot.

‘I got it!’

French amateur astronomer Marc Delcroix processed the amateur images and confirmed the discovery of a bright spot on an image by French amateur Régis De-Bénedictis, then in others taken by fellow amateurs in September and October. He had his own chance on Oct. 3 and 4 to photograph it with the Pic du Midi one-meter telescope, where on the second night, "I caught the feature when it was transiting, and I thought, ‘Yes, I got it!’” said Delcroix.

“I was thrilled to see such activity on Uranus. Getting details on Mars, Jupiter or Saturn is now routine, but seeing details on Uranus and Neptune are the new frontiers for us amateurs and I did not want to miss that,” said Delcroix, who works for an auto parts supplier in Toulouse and has been observing the skies – Jupiter in particular - with his backyard telescope since 2006 and, since 2012, occasionally with the Pic du Midi telescope. “I was so happy to confirm myself these first amateur images on this bright storm on Uranus, feeling I was living a very special moment for planetary amateur astronomy.”Interestingly, the extremely bright storm seen by the 10-meter Keck II telescope in the near infrared is not the one seen by the amateurs, which is much deeper in the atmosphere than the one that initially caused all the excitement. De Pater’s colleague Larry Sromovsky, a planetary scientist at the University of Wisconsin, Madison, identified the amateur spot as one of the few features on the Keck Observatory images from August 5 that was only seen at 1.6 microns, and not at 2.2 microns. The 1.6 micron light is emitted from deeper in the atmosphere, which means that this feature is below the uppermost cloud layer of methane-ice in Uranus’s atmosphere.

“The colors and morphology of this cloud complex suggests that the storm may be tied to a vortex in the deeper atmosphere similar to two large cloud complexes seen during the equinox,” Sromovsky said

Such vortices could be anchored much deeper in the atmosphere and extend over large vertical distances, as inferred from similar vortices on Jupiter, including its Great Red Spot.

An expanded team of astronomers led by Kunio M. Sayanagi, an Assistant Professor at Hampton University in Virginia, leveraged the amateur observations to activate a “Target of Opportunity” proposal on the Hubble Space Telescope, which imaged the entire planet on Oct. 14. Observing at a variety of wavelengths, HST revealed multiple storm components extending over a distance of more than 9,000 kilometers (5,760 miles) and clouds at a variety of altitudes.

De Pater, Sromovsky, Hammel and Pat Fry of the University of Wisconsin will report the details of their observations on Nov. 12 at a meeting of the American Astronomical Society’s Division of Planetary Sciences in Tucson, Ariz.

Ice giant

Uranus is an ice giant, about four times the diameter of Earth, with an atmosphere of hydrogen and helium, with just a bit of methane to give it a blue tint. Because it is so distant – 19 times farther from the sun than Earth – astronomers were able to see little detail on its surface until adaptive optics on both Keck Observatory telescopes revealed features much like those on Jupiter.

De Pater and her colleagues have been following Uranus for more than a decade, charting the weather on the planet, including bands of circulating clouds, massive swirling storms and convective features at its north pole. Bright clouds are probably caused by gases such as methane rising in the atmosphere and condensing into highly reflective clouds of methane ice.

Because Uranus has no internal source of heat, its atmospheric activity was thought to be driven solely by sunlight, which is now weak in the northern hemisphere. Hence astronomers were surprised when these observations showed such intense activity.

Observations taken with the Keck II telescope by Christoph Baranec, an Assistant Professor at the University of Hawaii on Manoa, revealed that the storm was still active, but had a different morphology and possibly reduced intensity.

“If indeed these features are high-altitude clouds generated by flow perturbations associated with a deeper vortex system, such drastic fluctuations in intensity would indeed be possible,” Sromovsky added.

“These unexpected observations remind us keenly of how little we understand about atmospheric dynamics in outer planet atmospheres,” the authors wrote in their paper.

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 spectographs 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.


SCIENCE CONTACTS

Imke de Pater

imke@berkeley.edu

Larry Sromovsky
larry.sromovsky@ssec.wisc.edu

Heidi Hammel
(203) 321-6929

hbhammel@aura-astronomy.org

Marc Delcroix
delcroix.marc@free.fr

MEDIA CONTACT:

Steve Jefferson
Communications Officer
W. M. Keck Observatory
808.881.3827

sjefferson@keck.hawaii.edu




Friday, November 14, 2014

The Party’s Over for These Youthful Compact Galaxies Release Images

Fast Evolution of a Galaxy
This graphic illustrates how a vibrant, star-forming galaxy quickly transforms into a sedate galaxy composed of old stars. The scenario begins when two galaxies merge (Panel 1), funneling a large amount of gas into the central region. The gas compresses, sparking a firestorm of star birth, which blows out most of the remaining star-forming gas (Panel 2). Devoid of its fuel, the galaxy settles into a quiet existence, composed of aging stars (Panel 3).  Illustration Credit: NASA, ESA, and A. Feild (STScI)Science Credit: P. Sell (Texas Tech University). Release Images 
 
Outflows from 12 Merging Galaxies
The 12 galaxies in these Hubble Space Telescope images are undergoing a firestorm of star birth, as shown by their bright white cores. Hubble reveals that the galaxies' star-making frenzy was ignited by mergers with other galaxies. The odd shapes of many of the galaxies are telltale evidence of those close encounters.

The new Hubble Wide Field Camera 3 observations suggest that energy from the star-birthing frenzy created powerful winds that are blowing out the gas, squelching future generations of stars. This activity occurred when the universe was half its current age of 13.7 billion years. The gas-poor galaxies may eventually become so-called "red and dead" galaxies, composed only of aging stars.

The galaxies are the most compact yet found. They contain as much mass as our Milky Way galaxy, but packed into a much smaller area. The smallest galaxies are about 650 light-years across.

The Hubble false-color images were processed to bring out important details in the galaxies. The images were taken in 2010. Credit: NASA, ESA, and P. Sell (Texas Tech University)

Researchers using NASA's Hubble Space Telescope and Chandra X-ray Observatory have uncovered young, massive, compact galaxies whose raucous star-making parties are ending early. The firestorm of star birth has blasted out most of the remaining gaseous fuel needed to make future generations of stars. Now the party's over for these gas-starved galaxies, and they are on track to possibly becoming so-called "red and dead galaxies," composed only of aging stars.

Astronomers have debated for decades how massive galaxies rapidly evolve from active star-forming machines to star-starved graveyards. Previous observations of these galaxies reveal geysers of gas shooting into space at up to 2 million miles an hour. Astronomers have suspected that powerful monster black holes lurking at the centers of the galaxies triggered the gaseous outflows and shut down star birth by blowing out any remaining fuel.

Now an analysis of 12 merging galaxies at the end of their star-birthing frenzy is showing that the stars themselves are turning out the lights on their own star-making party. This happened when the universe was half its current age of 13.7 billion years.
"Before our study, the common belief was that stars cannot drive high-velocity outflows in galaxies; only more powerful supermassive black holes can do that," explained Paul Sell of Texas Tech University in Lubbock, lead author of a science paper describing the study's results. "Through our analysis we found that if you have a compact enough starburst, which Hubble showed was the case with these galaxies, you can actually produce the velocities of the outflows we observed from the stars alone without needing to invoke the black hole."

Team member Christy Tremonti of the University of Wisconsin-Madison first identified the galaxies from the Sloan Digital Sky Survey as post-starburst objects spouting high-speed gaseous fountains. The sharp visible-light views from Hubble's Wide Field Camera 3 show that the outflows are arising from the most compact galaxies yet found. These galaxies contain as much mass as our Milky Way galaxy, but packed into a much smaller area. The smallest galaxies are about 650 light-years across.

In such small regions of space, these galaxies are forming a few hundred suns a year. (By comparison, the Milky Way makes only about one sun a year.) This makes for a rowdy party that wears itself out quickly, in only a few tens of millions of years. One reason for the stellar shutdown is that the gas rapidly heats up, becoming too hot to contract under gravity to form new stars. Another possibility is that the star-birthing frenzy blasts out most of the star-making gas via powerful stellar winds.

"The biggest surprise from Hubble was the realization that the newly formed stars were born so close together," said team member Aleks Diamond-Stanic of the University of Wisconsin-Madison, who first suggested the possibility of starburst-driven outflows from these galaxies in a 2012 science paper. "The extreme physical conditions at the centers of these galaxies explain how they can expel gas at millions of miles per hour."

To identify the mechanism triggering the high-velocity outflows, Sell and his team used the Chandra X-ray Observatory and other telescopes to determine whether the galaxies' supermassive black holes (weighing up to a billion suns) were the powerhouses driving them. After analyzing all of the observations, the team concluded that the black holes were not the source of the outflows. Rather, it was the powerful stellar winds from the most massive and short-lived stars at the end of their lives, combined with their explosive deaths as supernovae.

Based on their analysis of the Hubble and Chandra data, team members suggest that the "party begins" when two gas-rich galaxies collide, funneling a torrent of cold gas into the merging galaxies' compact center. The large amount of gas compressed into the small space ignites the birth of numerous stars. The energy from the stellar firestorm then blows out the leftover gas, quenching further star formation.

"If you stop the flow of cold gas to form stars, that's it," explained Sell, who conducted the research while a graduate student at the University of Wisconsin-Madison. "The stars stop forming, and the galaxy rapidly evolves and may eventually become a red, dead elliptical galaxy. These extreme starbursts are quite rare, however, so they may not grow into the typical giant elliptical galaxies seen in our nearby galactic neighborhood. They may, instead, be more compact."

The team's results were published in the July 11 edition of the Monthly Notices of the Royal Astronomical Society.



Contact:

Donna Weaver / Ray Villard
Space Telescope Science Institute, Baltimore, Md.
410-338-4493 / 410-338-4514

dweaver@nasa.gov / villard@stsci.edu

Paul Sell
Texas Tech University, Lubbock, Texas
806-742-7129

paul.sell@ttu.edu


Source: HubbleSite

Hubble reveals a super-rich galactic neighbourhood

Credit: ESA/Hubble & NASA
Acknowledgement: Nick Rose

This new image from the NASA/ESA Hubble Space Telescope shows the super-rich galaxy cluster Abell 1413. Located between the constellations of Leo (The Lion) and Coma Berenices, the cluster is over 2 billion light-years from Earth. This image is dominated by a large and highly elliptical galaxy called MCG+04-28-097, with a halo of stars extending for more than 6.5 million light-years [1].

Abell 1413 is part of the Abell catalogue, a collection of over 4000 rich clusters of galaxies fairly close to Earth — at least from a cosmological perspective — their light took less than 3 billion years to reach us. The clusters are called rich due to the huge number of galaxies they play host to. Abell 1413 is observed to contain more than 300 galaxies held together by the immense gravity of the cluster.

The strong interactions between these galaxies cause the material in the cluster to be heated to extremely high temperatures of almost 100 million degrees. Because of this, the cluster emits very strong X-ray radiation.
Visible distortions in the image can be seen in the form of arcs, caused by gravitational lensing [2].

This image was created from optical and near-infrared exposures taken with the Wide Field Channel of Hubble’s Advanced Camera for Surveys (ACS). A version of this image was entered into the Hubble's Hidden Treasures image processing competition by contestant Nick Rose.


Notes

[1] The galaxies at the centre of Abell 1413 are found to be very highly elliptical whereas those at the periphery are more spherical.

[2] Gravitational lensing occurs when the intense gravity of the cluster bends space-time around it, causing a range of bizarre and beautiful optical phenomena for galaxies located in the background.


Source:  ESA/Hubble - Space Telescope