January 13, 2017

Spiral Galaxy NGC 4921

Spiral Galaxy NGC 4921

How far away is spiral galaxy NGC 4921? Although presently estimated to be about 310 million light years distant, a more precise determination could be coupled with its known recession speed to help humanity better calibrate the expansion rate of the entire visible universe. Toward this goal, several images were taken by the Hubble Space Telescope in order to help identify key stellar distance markers known as Cepheid variable stars. Since NGC 4921 is a member of the Coma Cluster of Galaxies, refining its distance would also allow a better distance determination to one of the largest nearby clusters in the local universe. The magnificent spiral NGC 4921 has been informally dubbed anemic because of its low rate of star formation and low surface brightness. Visible in the above image are, from the center, a bright nucleus, a bright central bar, a prominent ring of dark dust, blue clusters of recently formed stars, several smaller companion galaxies, unrelated galaxies in the far distant universe, and unrelated stars in our Milky Way Galaxy.

Image Credit: Hubble Legacy Archive, ESA, NASA
Explanation from: https://www.nasa.gov/content/hubble-sees-anemic-spiral-ngc-4921

Aurora over Manitoba

Aurora over Manitoba 

Manitoba, Canada

Image Credit: Daniel J Cox

Earth's Atmosphere seen from the International Space Station

Earth's Atmosphere seen from the International Space Station

ISS, Orbit of the Earth
September 2016

Image Credit: NASA/ESA

January 12, 2017

The Cartwheel Galaxy

Cartwheel Galaxy

Lying about 500 million light-years away in the constellation of Sculptor, the cartwheel shape of this galaxy is the result of a violent galactic collision. A smaller galaxy has passed right through a large disc galaxy and produced shock waves that swept up gas and dust — much like the ripples produced when a stone is dropped into a lake — and sparked regions of intense star formation (appearing blue). The outermost ring of the galaxy, which is 1.5 times the size of our Milky Way, marks the shock wave’s leading edge. This object is one of the most dramatic examples of the small class of ring galaxies.

Image Credit: ESA/Hubble & NASA
Explanation from: https://www.spacetelescope.org/images/potw1036a/

Aurora over Alaska

Aurora over Alaska

Talkeetna, Alaska, USA
November 3, 2015

Image Credit & Copyright: Dora Miller

The Trapezium Cluster

The Trapezium Cluster

The Orion Nebula is arguably the finest of all nebulae within the Milky Way visible from the Northern Hemisphere. With a gaseous repository of 10,000 suns, and illuminated by a cluster of hot young stars, the clouds of Messier 42 — as it is also known — glow with fantastic colours and shapes, giving us a bird’s eye view of one of the greatest star forming nurseries in our part of the Milky Way. Messier 42 is a complex of glowing gas, mostly hydrogen but also helium, carbon, nitrogen, and oxygen in decreasing amounts, located 1,500 light-years away. At its very heart, we find the Trapezium, a group of four very hot stars that illuminate the nebula. They are the brightest of an extended cluster of several thousand young stars many of which lie unseen within the opaque gas and dust. Amazingly, whilst the Orion Nebula is easy to identify with the unaided eye, there is apparently no written record of its existence before the 17th century.

This image is based on data acquired with the 1.5 m Danish telescope at the ESO La Silla Observatory in Chile, through three filters (B: 60 s, V: 30 s, R: 21 s).

Image Credit: ESO/IDA/Danish 1.5 m/R.Gendler, J.-E. Ovaldsen, and A. Hornstrup
Explanation from: https://www.eso.org/public/images/trapeziumdk15b/

January 11, 2017

Alien Sunset

Alien Sunset

Our solitary sunsets here on Earth might not be all that common in the grand scheme of things. New observations from NASA's Spitzer Space Telescope have revealed that mature planetary systems -- dusty disks of asteroids, comets and possibly planets -- are more frequent around close-knit twin, or binary, stars than single stars like our sun. That means sunsets like the one portrayed in this artist's photo concept, and more famously in the movie "Star Wars," might be quite commonplace in the universe.

Binary and multiple-star systems are about twice as abundant as single-star systems in our galaxy, and, in theory, other galaxies. In a typical binary system, two stars of roughly similar masses twirl around each other like pair-figure skaters. In some systems, the two stars are very far apart and barely interact with each other. In other cases, the stellar twins are intricately linked, whipping around each other quickly due to the force of gravity.

Astronomers have discovered dozens of planets that orbit around a single member of a very wide stellar duo. Sunsets from these worlds would look like our own, and the second sun would just look like a bright star in the night sky.

But do planets exist in the tighter systems, where two suns would dip below a planet's horizon one by one? Unveiling planets in these systems is tricky, so astronomers used Spitzer to look for disks of swirling planetary debris instead. These disks are made of asteroids, comets and possibly planets. The rocky material in them bangs together and kicks up dust that Spitzer's infrared eyes can see. Our own solar system is swaddled in a similar type of disk.

Surprisingly, Spitzer found more debris disks around the tightest binaries it studied (about 20 stars) than in a comparable sample of single stars. About 60 percent of the tight binaries had disks, while the single stars only had about 20 percent. These snug binary systems are as close or closer than just three times the distance between Earth and the sun. And the disks in these systems were found to circumnavigate both members of the star pair, rather than just one.

Though follow-up studies are needed, the results could mean that planet formation is more common around extra-tight binary stars than single stars. Since these types of systems would experience double sunsets, the artistic view portrayed here might not be fiction.

The original sunset photo used in this artist's concept was taken by Robert Hurt of the Spitzer Science Center at the California Institute of Technology, Pasadena, California.

Image Credit: NASA/JPL-Caltech/Univ. of Ariz.
Explanation from: http://photojournal.jpl.nasa.gov/catalog/PIA09228

Vela Supernova Remnant

Vela Supernova Remnant

A so-called Supernova Remnant (SNR) in the Vela constellation, captured by ESO's 1 m Schmidt Telescope at La Silla in Chile. The glowing gas ribbons seen here are part of a shock wave launched into the interstellar medium by a large star that exploded about 11,000 years ago. A "ghost" of the once-large star remains: an ultra-dense neutron star that spins more than 10 times a second, called a pulsar, is located in the central region of this SNR.

Image Credit: ESO
Explanation from: http://eso.org/public/images/vela-snr-schmidtourcomp/

Spiral Galaxy NGC 4707

Spiral Galaxy NGC 4707

On a clear evening in April of 1789, the renowned astronomer William Herschel continued his unrelenting survey of the night sky, hunting for new cosmic objects — and found cause to celebrate! Lengthening his impressive list of cosmic discoveries yet again, the astronomer spotted this bright spiral galaxy, named NGC 4707, lurking in the constellation of Canes Venatici (The Hunting Dog). NGC 4707 lies roughly 22 million light-years from Earth.

Over two centuries later, the NASA/ESA Hubble Space Telescope is able to view the same galaxy in far greater detail than Herschel could, allowing us to appreciate the intricacies and characteristics of NGC 4707 as never before. This striking image comprises observations from Hubble’s Advanced Camera for Surveys (ACS), one of a handful of high-resolution instruments currently aboard the space telescope.

Herschel himself reportedly described NGC 4707 as a “small, stellar” galaxy; while it is classified as a spiral (type Sm), its overall shape, centre, and spiral arms are very loose and undefined, and its central bulge is either very small or non-existent. It instead appears as a rough sprinkling of stars and bright flashes of blue on a dark canvas, as if a pointillist painter had dotted the cosmos with small pinpricks of bright paint.

The blue smudges seen across the frame highlight regions of recent or ongoing star formation, with newborn stars glowing in bright, intense shades of cyan and turquoise.

Image Credit: ESA/Hubble & NASA
Explanation from: https://www.spacetelescope.org/images/potw1651a/

Sunrise

Sunrise seen from the International Space Station

ISS, Orbit of the Earth
September 2016

Image Credit: NASA/ESA

Volcán de Colima & The Moon

Volcán de Colima & The Moon

Colima, Mexico
2002

Image Credit & Copyright: Sergio Tapiro

January 10, 2017

Wide-field view of the sky around the Globular Star Cluster Messier 4

Globular Star Cluster Messier 4

This wide-field view is centred on the globular star cluster Messier 4 (NGC 6121) in the constellation of Scorpius (The Scorpion). It is a colour composite made from exposures from the Digitized Sky Survey 2 (DSS2). The smaller globular cluster at the upper left is NGC 6144. It is similar to Messier 4, but more than three times further away. The red glow of clouds of hydrogen and associated star formation can also be seen in the upper left corner and the bright star Sigma Scorpii can be seen at the upper right.

Image Credit: ESO/Digitized Sky Survey 2, Davide De Martin.
Explanation from: https://www.eso.org/public/images/eso1235c/

Globular Cluster Messier 4

Globular Cluster Messier 4

This image from ESO’s La Silla Observatory in Chile shows the spectacular globular star cluster Messier 4. This ball of tens of thousands of ancient stars is one of the closest and most studied of the globular clusters and recent work has revealed that one of its stars has strange and unexpected properties, apparently possessing the secret of eternal youth.

The Milky Way galaxy is orbited by more than 150 globular star clusters that date back to the distant past of the Universe. One of the closest to the Earth is the cluster Messier 4 (also known as NGC 6121) in the constellation of Scorpius (The Scorpion). This bright object can be easily seen in binoculars, close to the bright red star Antares, and a small amateur telescope can show some of its constituent stars.

This new image of the cluster from the Wide Field Imager (WFI) on the MPG/ESO 2.2-metre telescope at ESO’s La Silla Observatory reveals many more of the cluster’s tens of thousands of stars and shows the cluster against the rich background of the Milky Way.

Astronomers have also studied many of the stars in the cluster individually using instruments on ESO’s Very Large Telescope. By splitting the light from the stars up into its component colours they can work out their chemical composition and ages.

New results for the stars in Messier 4 have been surprising. The stars in globular clusters are old and hence not expected to be rich in the heavier chemical elements. This is what is found, but one of the stars in a recent survey was also found to have much more of the rare light element lithium than expected. The source of this lithium is mysterious. Normally this element is gradually destroyed over the billions of years of a star's life, but this one star amongst thousands seems to have the secret of eternal youth. It has either somehow managed to retain its original lithium, or it has found a way to enrich itself with freshly made lithium.

Image Credit: ESO
Explanation from: https://www.eso.org/public/news/eso1235/

Spiral Galaxy NGC 1097

Spiral Galaxy NGC 1097

NASA's Spitzer Space Telescope has imaged a wild creature of the dark -- a coiled galaxy with an eye-like object at its center.

The galaxy, called NGC 1097, is located 50 million light-years away. It is spiral-shaped like our Milky Way, with long, spindly arms of stars. The "eye" at the center of the galaxy is actually a monstrous black hole surrounded by a ring of stars. In this color-coded infrared view from Spitzer, the area around the invisible black hole is blue and the ring of stars, white.

The black hole is huge, about 100 million times the mass of our sun, and is feeding off gas and dust along with the occasional unlucky star. Our Milky Way's central black hole is tame in comparison, with a mass of a few million suns.

The ring around the black hole is bursting with new star formation. An inflow of material toward the central bar of the galaxy is causing the ring to light up with new stars.

The galaxy's red spiral arms and the swirling spokes seen between the arms show dust heated by newborn stars. Older populations of stars scattered through the galaxy are blue. The fuzzy blue dot to the left, which appears to fit snuggly between the arms, is a companion galaxy. Astronomers say it is unclear whether this companion poked a hole in the larger galaxy, or just happens to be aligned in a gap in the arms.

Other dots in the picture are either nearby stars in our galaxy, or distant galaxies.

This image was taken during Spitzer's cold mission, before it ran out of liquid coolant. The observatory's warm mission is ongoing, with two infrared channels operating at about 30 Kelvin (minus 406 degrees Fahrenheit).

Infrared light with a wavelength of 3.6 microns is blue; 4.5-micron light is green and 8.0-micron light is red. The contribution from starlight measured at 3.6 microns has been subtracted from the 8.0-micron image to enhance the visibility of the dust features.

Image Credit: NASA/JPL-Caltech/The SINGS Team (SSC/Caltech)
Explanation from: http://www.spitzer.caltech.edu/images/2685-ssc2009-14a1-The-Coiled-Galaxy-NGC-1097

Earth and Moon seen by Mars Express spacecraft from 8 million kilometres away

Earth and Moon seen by Mars Express spacecraft from 8 million kilometres away

On the night of 3 July 2003, the Mars Express spacecraft was pointed backwards to obtain a view of the Earth-Moon system from a distance of 8 million kilometres while on its way to Mars. This image is the first picture of planetary objects obtained by the Mars Express High Resolution Stereo Camera (HRSC). Although the spatial resolution is low at this great distance, the picture gives a good indication of what to expect from Mars Express in its orbit around Mars. At only 250-300 kilometres above Mars, the camera will obtain very high-resolution images, in brilliant colour and impressive 3D of most of the Martian surface, at resolutions of up to 2 metres. The image was built by combining a super resolution black-and-white snap-shot image of the Earth and the Moon taken by the HRSC with colour information obtained by the blue, green, and red sensors of the instrument.

Image Credit: ESA/DLR/Freie Universität Berlin
Explanation from: http://mars.jpl.nasa.gov/express/newsroom/pressreleases/20030717a_image01.html

Earth seen from the International Space Station

Earth seen from the International Space Station

ISS, Orbit of the Earth
August 2016

Image Credit: NASA/ESA

Spiral Galaxy RX J1140.1+0307

Spiral Galaxy RX J1140.1+0307

This image taken with the Advanced Camera for Surveys (ACS) onboard the NASA/ESA Hubble Space Telescope captures a galaxy in the Virgo constellation. This camera was installed in 2002, and its wide field of view is double that of its predecessor, capturing superb images with sharp image quality and enhanced sensitivity that can be seen here.

The beautiful spiral galaxy visible in the centre of the image is catchily known as RX J1140.1+0307, and it presents an interesting puzzle. At first glance, this galaxy appears to be a normal spiral galaxy, much like the Milky Way, but first appearances can be deceptive!

The Milky Way galaxy, like most large galaxies, has a supermassive black hole at its centre, but some galaxies are centred on lighter, intermediate-mass black holes. RX J1140.1+0307 is such a galaxy — in fact, it is centred on one of the lowest black hole masses known in any luminous galactic core. What puzzles scientists about this particular galaxy is that the calculations don’t add up. With such a relatively low mass for the central black hole, models for the emission from the object cannot explain the observed spectrum; unless there are other mechanisms at play in the interactions between the inner and outer parts of the accretion disc surrounding the black hole.

Image Credit: ESA/Hubble & NASA, Judy Schmidt
Explanation from: https://www.spacetelescope.org/images/potw1702a/

Volcán de Colima

Volcán de Colima

Colima, Mexico
2010

Image Credit & Copyright: Sergio Tapiro

January 8, 2017

Sunrise seen from the International Space Station

Sunrise seen from the International Space StationSunrise seen from the International Space StationSunrise seen from the International Space StationSunrise seen from the International Space StationSunrise seen from the International Space Station

ISS, Orbit of the Earth
September 2016

Image Credit: NASA/ESA

The IC 3639 Galaxy

The IC 3639 Galaxy

IC 3639, a galaxy with an active galactic nucleus, is seen in this image combining data from the Hubble Space Telescope and the European Southern Observatory.

This galaxy contains an example of a supermassive black hole hidden by gas and dust. Researchers analyzed NuSTAR data from this object and compared them with previous observations from NASA's Chandra X-Ray Observatory and the Japanese-led Suzaku satellite. The findings from NuSTAR, which is more sensitive to higher energy X-rays than these observatories, confirm the nature of IC 3639 as an active galactic nucleus that is heavily obscured, and intrinsically much brighter than observed.

Image Credit: NASA/JPL-Caltech/ESO/STScI
Explanation from: http://photojournal.jpl.nasa.gov/catalog/PIA21087

NGC 3576: Glowing Gas in the Milky Way

NGC 3576: Glowing Gas in the Milky Way

A region of glowing gas in the Sagittarius arm of the Milky Way galaxy, NGC 3576 is located about 9,000 light years from Earth. Such nebulas present a tableau of the drama of the evolution of massive stars, from the formation in vast dark clouds, their relatively brief (a few million years) lives, and the eventual destruction in supernova explosions. The diffuse X-ray data detected by Chandra (blue) are likely due to the winds from young, massive stars that are blowing throughout the nebula. Optical data from ESO are shown in orange and yellow.

Image Credit: X-ray: NASA/CXC/Penn State/L.Townsley et al, Optical: ESO/2.2m telescope
Explanation from: https://www.nasa.gov/mission_pages/chandra/multimedia/NGC3576-glowing-gas-milky-way.html

Puyehue-Cordón Caulle Volcano Eruption

Puyehue-Cordón Caulle Volcano Eruption

Osorno, Los Lagos, Chile

Image Credit: Ivan Alvarado

The NGC 1448 Galaxy

The NGC 1448 Galaxy

NGC 1448, a galaxy with an active galactic nucleus, is seen in this image combining data from the Carnegie-Irvine Galaxy Survey in the optical range and NuSTAR in the X-ray range.

This galaxy contains an example of a supermassive black hole hidden by gas and dust. X-ray emissions from NGC 1448, as seen by NuSTAR and Chandra, suggests for the first time that, like IC 3639, there must be a thick layer of gas and dust hiding the active black hole in this galaxy from our line of sight.

Image Credit: NASA/JPL-Caltech/Carnegie-Irvine Galaxy Survey

Supernova Remnant G11.2-0.3

Supernova Remnant G11.2-0.3

  • New Chandra data of the supernova remnant G11.2-0.3 raise new questions about the timing of its origin.
  • Previously, G11.2-0.3 was associated with an event recorded by Chinese observers in 386 CE.
  • Chandra observations show that dense gas clouds lie along the line of sight between Earth and G11.2-0.3.
  • This new information means that the supernova explosion would have been too faint to be seen with the naked eye from Earth.

A new look at the debris from an exploded star in our galaxy has astronomers re-examining when the supernova actually happened. Recent observations of the supernova remnant called G11.2-0.3 with NASA's Chandra X-ray Observatory have stripped away its connection to an event recorded by the Chinese in 386 CE.

Historical supernovas and their remnants can be tied to both current astronomical observations as well as historical records of the event. Since it can be difficult to determine from present observations of their remnant exactly when a supernova occurred, historical supernovas provide important information on stellar timelines. Stellar debris can tell us a great deal about the nature of the exploded star, but the interpretation is much more straightforward given a known age.

New Chandra data on G11.2-0.3 show that dense clouds of gas lie along the line of sight from the supernova remnant to Earth. Infrared observations with the Palomar 5-meter Hale Telescope had previously indicated that parts of the remnant were heavily obscured by dust. This means that the supernova responsible for this object would simply have appeared too faint to be seen with the naked eye in 386 CE. This leaves the nature of the observed 386 CE event a mystery.

A new image of G11.2-0.3 is being released in conjunction with this week's workshop titled "Chandra Science for the Next Decade" being held in Cambridge, Massachusetts. While the workshop will focus on the innovative and exciting science Chandra can do in the next ten years, G11.2-0.3 is an example of how this "Great Observatory" helps us better understand the complex history of the Universe and the objects within it.

Taking advantage of Chandra's successful operations since its launch into space in 1999, astronomers were able to compare observations of G11.2-0.3 from 2000 to those taken in 2003 and more recently in 2013. This long baseline allowed scientists to measure how fast the remnant is expanding. Using this data to extrapolate backwards, they determined that the star that created G11.2-0.3 exploded between 1,400 and 2,400 years ago as seen from Earth.

Previous data from other observatories had shown this remnant is the product of a "core-collapse" supernova, one that is created from the collapse and explosion of a massive star. The revised timeframe for the explosion based on the recent Chandra data suggests that G11.2-0.3 is one of the youngest such supernovas in the Milky Way. The youngest, Cassiopeia A, also has an age determined from the expansion of its remnant, and like G11.2-0.3 was not seen at its estimated explosion date of 1680 CE due to dust obscuration. So far, the Crab nebula, the remnant of a supernova seen in 1054 CE, remains the only firmly identified historical remnant of a massive star explosion in our galaxy.

This latest image of G11.2-0.3 shows low-energy X-rays in red, the medium range in green, and the high-energy X-rays detected by Chandra in blue. The X-ray data have been overlaid on an optical field from the Digitized Sky Survey, showing stars in the foreground.

Although the Chandra image appears to show the remnant has a very circular, symmetrical shape, the details of the data indicate that the gas that the remnant is expanding into is uneven. Because of this, researchers propose that the exploded star had lost almost all of its outer regions, either in an asymmetric wind of gas blowing away from the star, or in an interaction with a companion star. They think the smaller star left behind would then have blown gas outwards at an even faster rate, sweeping up gas that was previously lost in the wind, forming the dense shell. The star would then have exploded, producing the G11.2-0.3 supernova remnant seen today.

The supernova explosion also produced a pulsar - a rapidly rotating neutron star - and a pulsar wind nebula, shown by the blue X-ray emission in the center of the remnant. The combination of the pulsar's rapid rotation and strong magnetic field generates an intense electromagnetic field that creates jets of matter and anti-matter moving away from the north and south poles of the pulsar, and an intense wind flowing out along its equator.

Image Credit: X-ray: NASA/CXC/NCSU/K.Borkowski et al; Optical: DSS
Explanation from: http://chandra.harvard.edu/photo/2016/g11/