April 4, 2015

Star-forming Region RCW 108 in Ara

Star-forming Region RCW 108

RCW 108 is a molecular cloud that is in the process of being destroyed by intense ultraviolet radiation from heavy and hot stars in the nearby stellar cluster NGC 6193, seen to the left in the photo. A series of images were obtained with the Wide Field Imager (WFI) of areas in the Milky Way band, including some in which interstellar nebulae of gas and dust are seen. Each frame records 8184 x 8196, or over 67 million, pixels in a sky field of 32 x 32 arcmin 2. The photo shows the RCW 108 complex of bright and dark nebulae in the southern association Ara OB1, a star-forming region in the constellation Ara (the Altar), deep in the southern sky. The resolution in this image has been degraded by reducing the number of pixels in one direction from about 8000 to 3000 in the "High-Resolution version", in order to make the image transportable over the web without incurring completely unacceptable transfer times. Still, it is very large, even in the highly compressed jpeg format, reflecting the great amount of details visible.

This colour picture is a composite made from 12 separate images, obtained with the WFI on 27 March 1999. The blue component corresponds to the B filter, the green to the V filter, and the red to the H-alpha filter. The images in each filter are the composite of 4 individual frames obtained with the telescope pointing at slightly different positions on the sky, so that the parts of the sky falling in the gaps between the 8 individual 2k x 4k CCDs in any given frame are recorded on the others. The monochromatic images are then produced by superimposing the individual frames, correcting for the telescope offsets ; this ensures that the complete field is well covered. This procedure is not simple, as the observing conditions may change slightly from exposure to exposure, resulting in small differences. Finally, the combined images in each filter are aligned and colour-coded to produce the colour picture.

For the processing of this large photo (8k x 8k; 256 Mbytes), a minimum of contrast correction was made and very faint lines may still be perceived in some places where the individual frames were joined. It may also be noted that there is a slight misalignment of the individual colours in stellar images at the extreme corners of the large field. This is due to the effect of differential atmospheric refraction, i.e. light rays of different colours are bent differently in air.

The exposure time was 300 sec for each frame in H-alpha, and 60 sec in B and V. East is to the left and North to the top.

Image Credit: ESO
Explanation from: http://www.eso.org/public/images/eso9925a/

Hubble finds Phantom Objects near Dead Quasars

Hubble finds Phantom Objects near Dead Quasars

NASA's Hubble Space Telescope has photographed a set of wispy, goblin-green objects that are the ephemeral ghosts of quasars that flickered to life and then faded.

Teacup Galaxy, SDSS 1430+13

The glowing structures have looping, helical, and braided shapes. "They don't fit a single pattern," said Bill Keel of the University of Alabama, Tuscaloosa, who initiated the Hubble survey. Keel believes the features offer insights into the puzzling behavior of galaxies with energetic cores.

The ethereal wisps outside the host galaxy are believed to have been illuminated by powerful ultraviolet radiation from a supermassive black hole at the core of the host galaxy. The most active of these galaxy cores are called quasars, where infalling material is heated to a point where a brilliant searchlight shines into deep space. The beam is produced by a disk of glowing, superheated gas encircling the black hole.

NGC 5972

"However, the quasars are not bright enough now to account for what we're seeing; this is a record of something that happened in the past," Keel said. "The glowing filaments are telling us that the quasars were once emitting more energy, or they are changing very rapidly, which they were not supposed to do."

Keel said that one possible explanation is that pairs of co-orbiting black holes are powering the quasars, and this could change their brightness, like using the dimmer switch on a chandelier.

SDSS 1510+07

The quasar beam caused the once invisible filaments in deep space to glow through a process called photoionization. Oxygen atoms in the filaments absorb light from the quasar and slowly re-emit it over many thousands of years. Other elements detected in the filaments are hydrogen, helium, nitrogen, sulfur, and neon. "The heavy elements occur in modest amounts, adding to the case that the gas originated in the outskirts of the galaxies rather than being blasted out from the nucleus," Keel said.

UGC 7342

The green filaments are believed to be long tails of gas pulled apart like taffy under gravitational forces resulting from a merger of two galaxies. Rather than being blasted out of the quasar's black hole, these immense structures, tens of thousands of light-years long, are slowly orbiting their host galaxy long after the merger was completed.

"We see these twisting dust lanes connecting to the gas, and there's a mathematical model for how that material wraps around in the galaxy," Keel said. Potentially, you can say we're seeing it 1.5 billion years after a smaller gas-rich galaxy fell into a bigger galaxy."

NGC 5252

The ghostly green structures are so far outside the galaxy that they may not light up until tens of thousands of years after the quasar outburst, and would likewise fade only tens of thousands of years after the quasar itself does. That's the amount of time it would take for the quasar light to reach them.

Not coincidentally, galaxy mergers would also trigger the birth of a quasar by pouring material into the central supermassive black hole.

Markarian 1498

The first "green goblin" type of object was found in 2007 by Dutch schoolteacher Hanny van Arkel. She discovered the ghostly structure in the online Galaxy Zoo project. The project has enlisted the public to help classify more than a million galaxies catalogued in the Sloan Digital Sky Survey (SDSS), and moved on to add galaxies seen in Hubble images probing the distant universe. The bizarre feature was dubbed Hanny's Voorwerp, Dutch for Hanny's object.

Because his follow-up Hubble images of Hanny's Voorwerp were so intriguing, Keel started a deliberate hunt for more bizarre objects like it. They would share the rare and striking color signature of Hanny's Voorwerp on the SDSS images.

UGC 11185

Keel had 200 people volunteer specifically to look at over 15,000 galaxies hosting quasars. Each candidate had to have at least 10 views that collectively reveal weirdly colored clouds.

Keel's team took the galaxies that looked the most promising and further studied them by dividing their light into its component colors through a process called spectroscopy. In follow-up observations from Kitt Peak National Observatory and the Lick Observatory, his team found 20 galaxies that had gas that was ionized by radiation from a quasar, rather than from the energy of star formation. And, the clouds extended more than 30,000 light-years outside the host galaxies.

SDSS 2201+11

Eight of the newly discovered clouds were more energetic than would be expected given the amount of radiation coming from the host quasar, even when observed in infrared light by NASA's Wide-field Infrared Survey Explorer (WISE) space telescope. The host quasars were as little as one-tenth the brightness needed to provide enough energy to photoionize the gas. Keel said that presumably the brightness changes are governed by the rate at which material is falling onto the central black hole.

Keel speculated that this quasar variability might be explained if there are two massive black holes circling each other in the host galaxy's center. This could conceivably happen after two galaxies merged. A pair of black holes whirling about each other could disrupt the steady flow of infalling gas. This would cause abrupt spikes in the accretion rate and trigger blasts of radiation.

When our Milky Way galaxy merges with the Andromeda galaxy (M31) in about 4 billion years, the black holes in each galaxy could wind up orbiting each other. So in the far future, our galactic system could have its own version of Hanny's Voorwerp encircling it.

Image Credit: NASA, ESA, and W. Keel
Explanation from: http://hubblesite.org/newscenter/archive/releases/2015/13/full/

April 3, 2015

Largest stars in the Universe: VY Canis Majoris

VY Canis Majoris is one of the biggest known stars, has a radius of approximately 1 420 ± 120 solar radii and 15 to 35 Solar mass

Distance from the Sun to VY Canis Majoris is approximately 5 000 light-years

Comparison: Earth - Sun - VY Canis Majoris (Radius)

Comparison: Earth - Sun - VY Canis Majoris - Radius

VY Canis Majoris pictured by Hubble Space Telescope

VY Canis Majoris - VY CMa - Hubble Space Telescope

VY CMa compared to Earth's orbit

VY CMa compared to Earth

VY Canis Majoris compared to the Sun

largest star largest star in the universe compared to the sun
largest star in the universe

vy canis majoris compared to sunvy canis majoris compared to the sunvy canis majoris to sunvy canis majoris sunvy canis majoris the sunvy canis majorisvy canis majorislargest stars in the universelargest star in the universe

April 2, 2015

International Space Station over 2015 Super Typhoon Maysak

Super Typhoon Maysak from Orbit Super Typhoon Maysak from ISS Super Typhoon Maysak from International Space Station

Typhoon Maysak strengthened into a super typhoon on March 31, reaching Category 5 hurricane status on the Saffir-Simpson Wind Scale. ESA Astronaut Samantha Cristoforetti captured this image while flying over the weather system on board the International Space Station.

The Tropical Rainfall Measuring Mission (TRMM) and Global Precipitation Measurement (GPM) satellites, both co-managed by NASA and the Japan Aerospace Exploration Agency, captured rainfall and cloud data that revealed heavy rainfall and high thunderstorms in the strengthening storm.

The TRMM satellite has been collecting valuable scientific data since November 1997. Early on March 30, the satellite collected rainfall data as it flew directly above Maysak at 04:14 UTC (12:14 a.m. EDT) when maximum sustained winds were near 85 knots (98 mph). Rainfall data was collected by TRMM's Microwave Imager (TMI) and Precipitation Radar (PR) instruments and showed heaviest rainfall southwest of the center, and in fragmented bands of thunderstorms northeast of the center. In both of those places rainfall was in excess of 50 mm/2 inches per hour.

Image Credit: ESA/NASA/Samantha Cristoforetti
Explanation from: http://www.nasa.gov/content/space-station-flies-over-super-typhoon-maysak/

NGC 6357 and Pismis 24

NGC 6357 and Pismis 24

The star cluster Pismis 24 lies in the core of the large emission nebula NGC 6357 that extends one degree on the sky in the direction of the Scorpius constellation. Part of the nebula is ionised by the youngest (bluest) heavy stars in Pismis 24. The intense ultraviolet radiation from the blazing stars heats the gas surrounding the cluster and creates a bubble in NGC 6357. The presence of these surrounding gas clouds makes probing into the region even harder.

One of the top candidates for the title of "Milky Way stellar heavyweight champion" was, until now, Pismis 24-1, a bright young star that lies in the core of the small open star cluster Pismis 24 (the bright stars in the Hubble image) about 8,000 light-years away from Earth. Pismis 24-1 was thought to have an incredibly large mass of 200 to 300 solar masses. New NASA/ESA Hubble measurements of the star, have, however, resolved Pismis 24-1 into two separate stars, and, in doing so, have "halved" its mass to around 100 solar masses.

Image Credit: NASA, ESA and Jesús Maíz Apellániz
Explanation from: http://www.spacetelescope.org/images/heic0619a/

April 1, 2015

Comparison Earth to Sun (Temperature, Mass, Radius, Volume)

Earth compared to Sun Earth compared to the Sun

Comparison Earth to Sun - Surface Temperature
Comparison Earth to Sun - Surface Temperature

Comparison Earth to Sun - Mass
Comparison Earth to Sun - Mass

Comparison Earth to Sun - Radius
Comparison Earth to Sun - Radius

Comparison Earth to Sun - Volume
Comparison Earth to Sun - Volume

March 31, 2015

NGC 346: Young stars sculpt gas with powerful outflows

Star cluster: NGC 346 - Hubble Space Telescope - Small Magellanic Cloud - Milky Way

This Hubble Space Telescope view shows one of the most dynamic and intricately detailed star-forming regions in space, located 210,000 light-years away in the Small Magellanic Cloud (SMC), a satellite galaxy of our Milky Way. At the centre of the region is a brilliant star cluster called NGC 346. A dramatic structure of arched, ragged filaments with a distinct ridge surrounds the cluster.

A torrent of radiation from the hot stars in the cluster NGC 346, at the centre of this Hubble image, eats into denser areas around it, creating a fantasy sculpture of dust and gas. The dark, intricately beaded edge of the ridge, seen in silhouette, is particularly dramatic. It contains several small dust globules that point back towards the central cluster, like windsocks caught in a gale.

Image Credit: NASA, ESA and A. Nota (ESA/STScI, STScI/AURA)
Explanation from: http://www.spacetelescope.org/images/heic0514a/

March 30, 2015

New stars shed light on the past

Star-Forming Region - N90 - NGC-602

This image depicts bright blue newly formed stars that are blowing a cavity in the centre of a fascinating star-forming region known as N90.

The high energy radiation blazing out from the hot young stars in N90 is eroding the outer portions of the nebula from the inside, as the diffuse outer reaches of the nebula prevent the energetic outflows from streaming away from the cluster directly. Because N90 is located far from the central body of the Small Magellanic Cloud, numerous background galaxies in this picture can be seen, delivering a grand backdrop for the stellar newcomers. The dust in the region gives these distant galaxies a reddish-brown tint.

Image Credit: NASA, ESA and the Hubble Heritage Team STScI/AURA)-ESA/Hubble Collaboration
Explanation from: http://www.spacetelescope.org/images/heic0702a/

Antennae Galaxies: NGC 4038 • NGC 4039

Antennae Galaxies: NGC 4038 • NGC 4039

The galaxies — also known as NGC 4038 and NGC 4039 — are locked in a deadly embrace. Once normal, sedate spiral galaxies like the Milky Way, the pair have spent the past few hundred million years sparring with one another. This clash is so violent that stars have been ripped from their host galaxies to form a streaming arc between the two. In wide-field images of the pair the reason for their name becomes clear — far-flung stars and streamers of gas stretch out into space, creating long tidal tails reminiscent of antennae.

This new image of the Antennae Galaxies shows obvious signs of chaos. Clouds of gas are seen in bright pink and red, surrounding the bright flashes of blue star-forming regions — some of which are partially obscured by dark patches of dust. The rate of star formation is so high that the Antennae Galaxies are said to be in a state of starburst, a period in which all of the gas within the galaxies is being used to form stars. This cannot last forever and neither can the separate galaxies; eventually the nuclei will coalesce, and the galaxies will begin their retirement together as one large elliptical galaxy.

This image uses visible and near-infrared observations from Hubble’s Wide Field Camera 3 (WFC3), along with some of the previously-released observations from Hubble’s Advanced Camera for Surveys (ACS).

Image Credit: ESA/Hubble & NASA
Explanation from: http://www.spacetelescope.org/images/potw1345a/

March 29, 2015

The bright star Alpha Centauri and its surroundings

Pictures of Stars - Alpha Centauri Proxima Centauri System - nearest star to Earth Sun - closest star to Earth Sun

This wide-field view of the sky around the bright star Alpha Centauri was created from photographic images forming part of the Digitized Sky Survey 2. The star appears so big just because of the scattering of light by the telescope's optics as well as in the photographic emulsion. Alpha Centauri is the closest star system to the Solar System.

Image Credit: ESO/Digitized Sky Survey 2
Explanation from: http://www.eso.org/public/images/eso1241e/