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Wednesday, July 23, 2014
Tuesday, July 22, 2014
Scale: Image is 12 arcmin across (35 light years) across.
Scale: Image is 4.6 arcmin across (8.7 light years) across.
Scale: Image is 9.5 arcmin across (36 light years) across.
Scale: Image is 11.4 arcmin across (about 66 light years) across.
These expansive haloes are important components of a galaxy. The halo of our own galaxy, the Milky Way, preserves signatures of both its formation and evolution. Yet, we know very little about the haloes of galaxies beyond our own as their faint and spread-out nature makes exploring them more difficult. Astronomers have so far managed to detect very few starry haloes around other galaxies.
Now, by utilising the unique space-based location of the NASA/ESA Hubble Space Telescope and its sensitive Advanced Camera for Surveys and Wide Field Camera 3, a team of astronomers has probed the halo surrounding the prominent giant elliptical galaxy Centaurus A , also known as NGC 5128, to unprecedented distances. They have found that its halo spreads far further into space than expected and does so in an unexpected form.
"Tracing this much of a galaxy's halo gives us surprising insights into a galaxy's formation, evolution, and composition," says Marina Rejkuba of the European Southern Observatory in Garching, Germany, lead author of the new Hubble study. "We found more stars scattered in one direction than the other, giving the halo a lopsided shape — which we hadn't expected!"
Along the galaxy's length the astronomers probed out 25 times further than the galaxy's radius — mapping a region some 450 000 light-years across. For the width they explored along 295 000 light-years, 16 times further than its "effective radius" . These are large distances if you consider that the main visible component of the Milky Way is around 120 000 light-years in diameter. In fact, the diameter of the halo probed by this team extends across 4 degrees in the sky — equivalent to eight times the apparent width of the Moon.
Alongside their unexpected uneven distribution, the stars within the halo also showed surprising properties relating to the proportion of elements heavier than hydrogen and helium found in the gas that makes up the stars. While the stars within the haloes of the Milky Way and other nearby spirals are generally low in heavy elements, the stars within Centaurus A's halo appear to be rich in heavy elements, even at the outermost locations explored.
"Even at these extreme distances, we still haven't reached the edge of Centaurus A's halo, nor have we detected the very oldest generation of stars," adds co-author Laura Greggio of INAF, Italy. "This aged generation is very important. The larger stars from it are responsible for manufacturing the heavy elements now found in the bulk of the galaxy's stars. And even though the large stars are long dead, the smaller stars of the generation still live on and could tell us a great deal."
The small quantity of heavy elements in the stellar haloes of large spiral galaxies like the Milky Way, is thought to originate from the way that the galaxies formed and evolved, slowly pulling in numerous small satellite galaxies and taking on their stars. For Centaurus A, the presence of stars rich in heavy elements in such remote locations suggests a single past merger with a large spiral galaxy. This event would have ejected stars from the spiral galaxy's disc and these are now seen as part of Centaurus A's outer halo.
"Measuring the amount of heavy elements in individual stars in a giant elliptical galaxy such as Centaurus A is uniquely the province of Hubble — we couldn't do it with any other telescope, and certainly not yet from the ground," adds Rejkuba. "These kinds of observations are fundamentally important to understanding the galaxies in the Universe around us."
These results are being published online in Astrophysical Journal on the 22 July and will appear in the 10 August 2014 issue.
Notes As it is relatively near to Earth, Centaurus A is prominent in our night sky and is well known for its striking and beautiful appearance (heic1110, opo9814e). To see more about this galaxy, see Hubblecast 46: A tour of Centaurus A.
 The effective radius of a galaxy, as referenced here, is the radius of the area in which half of the galaxy’s light is emitted. Astronomers use this effective radius rather than the full radius because the galaxy becomes faint and undefined at its outskirts.
Notes for editorsThe Hubble Space Telescope is a project of international cooperation between ESA and NASA.
The international team of astronomers in this study consists of M. Rejkuba (European Southern Observatory, Germany; Excellence Cluster Universe, Germany), W. E. Harris (McMaster University, Canada), L. Greggio (INAF, Italy), G. L. H. Harris (University of Waterloo, Canada), H. Jerjen (Australian National University, Australia), O. A. Gonzalez (European Southern Observatory, Chile).
More informationImage credit: NASA, ESA & M. Rejkuba (European Southern Observatory)
- Images of Hubble
- More on Centaurus A: heic1110, opo9814e and Hubblecast 46: A tour of Centaurus A.
- Research paper online in Astrophysical Journal.
European Southern Observatory
Garching bei München, Germany
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INAF, Osservatorio Astronomico di Padova
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ESA/Hubble, Public Information Officer
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Monday, July 21, 2014
Kepler-421b orbits an orange, type K star that is cooler and dimmer than our Sun. It circles the star at a distance of about 110 million miles. As a result, this Uranus-sized planet is chilled to a temperature of -135° Fahrenheit.
As the name implies, Kepler-421b was discovered using data from NASA's Kepler spacecraft. Kepler was uniquely suited to make this discovery. The spacecraft stared at the same patch of sky for 4 years, watching for stars that dim as planets cross in front of them. No other existing or planned mission shows such long-term, dedicated focus. Despite its patience, Kepler only detected two transits of Kepler-421b due to that world's extremely long orbital period.
The planet's orbit places it beyond the "snow line" - the dividing line between rocky and gas planets. Outside of the snow line, water condenses into ice grains that stick together to build gas giant planets.
"The snow line is a crucial distance in planet formation theory. We think all gas giants must have formed beyond this distance," explains Kipping.
Since gas giant planets can be found extremely close to their stars, in orbits lasting days or even hours, theorists believe that many exoplanets migrate inward early in their history.
Kepler-421b shows that such migration isn't necessary. It could have formed right where we see it now.
"This is the first example of a potentially non-migrating gas giant in a transiting system that we've found," adds Kipping.
The host star, Kepler-421, is located about 1,000 light-years from Earth in the direction of the constellation Lyra.
This research has been accepted for publication in The Astrophysical Journal and is available online. Additional information can be found at https://www.cfa.harvard.edu/~dkipping/kepler421.html
David A. Aguilar
Director of Public Affairs
Harvard-Smithsonian Center for Astrophysics
Public Affairs Specialist
Harvard-Smithsonian Center for Astrophysics
Friday, July 18, 2014
Thursday, July 17, 2014
What the spacecraft is actually seeing is the pixelated image shown at right, which was taken by Rosetta's OSIRIS narrow angle camera on 14 July from a distance of 12 000 km.
A second image and a movie show the comet after the image has been processed. The technique used, called "sub-sampling by interpolation", only acts to remove the pixelisation and make a smoother image, and it is important to note that the comet's surface features won't be as smooth as the processing implies. The surface texture has yet to be resolved simply because we are still too far away; any apparent brighter or darker regions may turn out to be false interpretations at this early stage.
But the movie, which uses a sequence of 36 interpolated images each separated by 20 minutes, certainly provides a truly stunning 360-degree preview of the overall complex shape of the comet. Regardless of surface texture, we can certainly see an irregular shaped world shining through. Indeed, some people have already likened the shape to a duck, with a distinct body and head.
Although less obvious in the 'real' image, the movie of interpolated images supports the presence of two definite components. One segment seems to be rather elongated, while the other appears more bulbous.
Dr. Daniel Devost
Marcelo Tucci Maia
Universidade do São Paulo
Prof. Jorge Meléndez
Universidade de São Paulo
Dr. Ivan Ramírez
University of Texas
Wednesday, July 16, 2014
The background image (in brown colours) represent the SDSS imaging survey of the South Galactic cap comprising about 3200 square degrees. Over-plotted in white/blue is the distribution of Dark Matter derived from the CFHT/Megacam Stripe-82 observation over 170 square degrees. The mass peaks in the map contain significant cosmological information, and will provide us with an improved understanding about the dark side of the Universe.
A number of studies have shown that Dark Matter is the principle mass component of the Universe making up about 80% of the mass budget. The most direct technique to reveal the Dark Matter distribution is by using the gravitational lensing technique. Indeed, following Einstein's theory of Gravitation, we know that a mass concentration will deform locally the Space-Time and the observed shapes of distant galaxies seen through the such concentration will be deflected and distorted. By measuring the exact shapes of millions of these distant galaxies we can then map accurately the mass distribution in the Universe, and identify the mass peaks tracing mass concentration along their line of sight. Importantly, the number of mass peaks as a function of the mass peak significance encodes important information on the cosmological world model. In particular this distribution is sensitive to the nature of Gravitational force at large scales as well as the geometry of the Universe. Measuring mass peaks is thus one of the most attractive way to probe the relative importance and nature of Dark Matter and Dark Energy, measure the evolution the Universe and predict its fate.
The abundance of mass peaks in the Dark Matter mass map confirms the theories of structure formation. In the near future, with the up-coming weak lensing surveys (to be conducted with the DES survey, LSST and Euclid), by precisely counting the peaks of dark matter mass maps, we will be able to set constrains on the nature of Dark Matter and Dark Energy.
About the CFHT
Contact information:Dr. HuanYuan Shan
Affiliation: EPFL, Switzerland
Phone number: +41 22 379 2427
Prof. Jean-Paul Kneib.
Affiliation: EPFL, Switzerland
Phone number +33 695 795 392
Prof. Martin Makler.
Affiliation: CBPF, Brazil
Phone number +55 21 2141 7191
Prof. Ludovic van Waerbeke
Affiliation: UBC, Canada
Phone number +1 604 822 5515
Dr. Eric Jullo.
Affiliation: LAM, France
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Dr. Daniel Devost
Director of Science Operations
Tuesday, July 15, 2014
Monday, July 14, 2014
Astronomers have studied the carbon monoxide in a galaxy over 12 billion light years from Earth and discovered that it’s running out of gas, quite literally, and headed for a ‘red and dead’ future.
ContactsDr Minh Huynh
ICRAR - UWA
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Credit: NASA Goddard Space Flight Center Conceptual Image La
Between 1838 and 1845, eta Carinae underwent a period of unusual variability during which it briefly outshone Canopus, normally the second-brightest star. As a part of this event, which astronomers call the Great Eruption, a gaseous shell containing at least 10 and perhaps as much as 40 times the sun's mass was shot into space. This material forms a twin-lobed dust-filled cloud known as the Homunculus Nebula, which is now about a light-year long and continues to expand at more than 1.3 million mph (2.1 million km/h).
Once the researchers had developed their Homunculus model, they took things one step further. They converted it to a format that can be used by 3D printers and made the file available along with the published paper.
NASA Goddard Space Flight Center
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Dr Keith Smith
Royal Astronomical Society
+44 (0)20 7734 4582
Prof. Wolfgang Steffen
National Autonomous University of Mexico
Please contact Francis Reddy (details above) in the first instance.
This research has been published in Steffen W. el al., 2014, "The three-dimensional structure of the Eta Carinae Homunculus", Monthly Notices of the Royal Astronomical Society, vol. 442, p. 3316-3328, published by Oxford University Press.
Notes for editors