Messier 106

A galaxy about 23 million light years away is the site of impressive, ongoing fireworks. Rather than paper, powder and fire, this galactic light show involves a giant black hole, shock waves and vast reservoirs of gas.

This galactic fireworks display is taking place in NGC 4258, also known as M106, a spiral galaxy like the Milky Way. This galaxy is famous, however, for something that our galaxy doesn’t have – two extra spiral arms that glow in X-ray, optical and radio light. These features, or anomalous arms, are not aligned with the plane of the galaxy, but instead intersect with it.

The anomalous arms are seen in this new composite image of NGC 4258, where X-rays from NASA’s Chandra X-ray Observatory are blue, radio data from the NSF’s Karl Jansky Very Large Array are purple, optical data from NASA’s Hubble Space Telescope are yellow and infrared data from NASA’s Spitzer Space Telescope are red.

A new study made with Spitzer shows that shock waves, similar to sonic booms from supersonic planes, are heating large amounts of gas – equivalent to about 10 million suns. What is generating these shock waves? Researchers think that the supermassive black hole at the center of NGC 4258 is producing powerful jets of high-energy particles. These jets strike the disk of the galaxy and generate shock waves. These shock waves, in turn, heat the gas – composed mainly of hydrogen molecules – to thousands of degrees.

The Chandra X-ray image reveals huge bubbles of hot gas above and below the plane of the galaxy. These bubbles indicate that much of the gas that was originally in the disk of the galaxy has been heated and ejected into the outer regions by the jets from the black hole.

The ejection of gas from the disk by the jets has important implications for the fate of this galaxy. Researchers estimate that all of the remaining gas will be ejected within the next 300 million years – very soon on cosmic time scales – unless it is somehow replenished. Because most of the gas in the disk has already been ejected, less gas is available for new stars to form. Indeed, the researchers used Spitzer data to estimate that stars are forming in the central regions of NGC 4258, at a rate which is about ten times less than in the Milky Way galaxy.

The European Space Agency’s Herschel Space Observatory was used to confirm the estimate from Spitzer data of the low star formation rate in the central regions of NGC 4258. Herschel was also used to make an independent estimate of how much gas remains in the center of the galaxy. After allowing for the large boost in infrared emission caused by the shocks, the researchers found that the gas mass is ten times smaller than had been previously estimated.

Because NGC 4258 is relatively close to Earth, astronomers can study how this black hole is affecting its galaxy in great detail. The supermassive black hole at the center of NGC 4258 is about ten times larger than the one in the Milky Way and is consuming material at a faster rate, potentially increasing its impact on the evolution of its host galaxy.

Image Credit: X-ray: NASA/CXC/Caltech/P.Ogle et al; Optical: NASA/STScI; IR: NASA/JPL-Caltech; Radio: NSF/NRAO/VLA
Explanation from: http://www.nasa.gov/chandra/multimedia/galactic-pyrotechnics.html

Dwarf Galaxy Leo A

At first glance this NASA/ESA Hubble Space Telescope image seems to show an array of different cosmic objects, but the speckling of stars shown here actually forms a single body — a nearby dwarf galaxy known as Leo A. Its few million stars are so sparsely distributed that some distant background galaxies are visible through it. Leo A itself is at a distance of about 2.5 million light-years from Earth and a member of the Local Group of galaxies; a group that includes the Milky Way and the well-known Andromeda galaxy.

Astronomers study dwarf galaxies because they are very numerous and are simpler in structure than their giant cousins. However, their small size makes them difficult to study at great distances. As a result, the dwarf galaxies of the Local Group are of particular interest, as they are close enough to study in detail.

As it turns out, Leo A is a rather unusual galaxy. It is one of the most isolated galaxies in the Local Group, has no obvious structural features beyond being a roughly spherical mass of stars, and shows no evidence for recent interactions with any of its few neighbours. However, the galaxy’s contents are overwhelmingly dominated by relatively young stars, something that would normally be the result of a recent interaction with another galaxy. Around 90% of the stars in Leo A are less than eight billion years old — young in cosmic terms! This raises a number of intriguing questions about why star formation in Leo A did not take place on the “usual” timescale, but instead waited until it was good and ready.

Image Credit: ESA/Hubble & NASA, Judy Schmidt
Explanation from: http://www.spacetelescope.org/images/potw1615a/

The Rosette Nebula

Measuring 50 light years in diameter, the large, round Rosette Nebula is found on the edge of a molecular cloud in the constellation of Monoceros the Unicorn. At the core of the nebula the very hot young stars have heated the surrounding gaseous shell to a temperature in the order of 6 million kelvins, resulting in the emission of copious amounts of X-Rays.

Image Credit & Copyright: Juan Ignacio Jimenez
Explanation by: Royal Observatory Greenwich

Total Solar Eclipse over Svalbard

Svalbard, Norway

March 20, 2015

Image Credit & Copyright: Thanakrit Santikunaporn

The NGC 660 Galaxy

This Hubble image shows a peculiar galaxy known as NGC 660, located around 45 million light-years away from us.

NGC 660 is classified as a "polar ring galaxy", meaning that it has a belt of gas and stars around its centre that it ripped from a near neighbour during a clash about one billion years ago. The first polar ring galaxy was observed in 1978 and only around a dozen more have been discovered since then, making them something of a cosmic rarity.

Unfortunately, NGC 660’s polar ring cannot be seen in this image, but has plenty of other features that make it of interest to astronomers – its central bulge is strangely off-kilter and, perhaps more intriguingly, it is thought to harbour exceptionally large amounts of dark matter. In addition, in late 2012 astronomers observed a massive outburst emanating from NGC 660 that was around ten times as bright as a supernova explosion. This burst was thought to be caused by a massive jet shooting out of the supermassive black hole at the centre of the galaxy.

Image Credit: ESA/Hubble & NASA
Explanation from: http://www.spacetelescope.org/images/potw1348a/

Artist's Impression of the Supermassive Black Hole

This artist's concept illustrates a supermassive black hole with millions to billions times the mass of our sun. Supermassive black holes are enormously dense objects buried at the hearts of galaxies. (Smaller black holes also exist throughout galaxies.) In this illustration, the supermassive black hole at the center is surrounded by matter flowing onto the black hole in what is termed an accretion disk. This disk forms as the dust and gas in the galaxy falls onto the hole, attracted by its gravity.

Also shown is an outflowing jet of energetic particles, believed to be powered by the black hole's spin. The regions near black holes contain compact sources of high energy X-ray radiation thought, in some scenarios, to originate from the base of these jets. This high energy X-radiation lights up the disk, which reflects it, making the disk a source of X-rays. The reflected light enables astronomers to see how fast matter is swirling in the inner region of the disk, and ultimately to measure the black hole's spin rate.

Image Credit: NASA/JPL-Caltech
Explanation from: http://photojournal.jpl.nasa.gov/catalog/PIA16695

Volcán de Colima (Fuego) Eruption

Colima, Mexico

December 13, 2015

Image Credit & Copyright: Sergio Tapiro

Stellar powerhouses in the Eagle Nebula

A spectacular section of the well-known Eagle Nebula has been targeted by the NASA/ESA Hubble Space Telescope. This collection of dazzling stars is called NGC 6611, an open star cluster that formed about 5.5 million years ago and is found approximately 6500 light-years from the Earth. It is a very young cluster, containing many hot, blue stars, whose fierce ultraviolet glow make the surrounding Eagle Nebula glow brightly. The cluster and the associated nebula together are also known as Messier 16.

Astronomers refer to areas like the Eagle Nebula as HII regions. This is the scientific notation for ionised hydrogen from which the region is largely made. Extrapolating far into the future, this HII region will eventually disperse, helped along by shockwaves from supernova explosions as the more massive young stars end their brief but brilliant lives.

In this image, dark patches can also be spotted, punctuating the stellar landscape. These areas of apparent nothingness are actually very dense regions of gas and dust, which obstruct light from passing through. Many of these may be hiding the sites of the early stages of star formation, before the fledgling stars clear away their surroundings and burst into view. Dark nebulae, large and small, are dotted throughout the Universe. If you look up to the Milky Way with the naked eye from a dark, remote site, you can easily spot some huge dark nebulae blocking the background starlight.

This picture was created from images from Hubble’s Wide Field Channel of the Advanced Camera for Surveys through the unusual combination of two near-infrared filters (F775W, coloured blue, and F850LP, coloured red). The image has also been subtly colourised using a ground-based image taken through more conventional filters. The Hubble exposure times were 2000 s in both cases and the field of view is about 3.2 arcminutes across.

Image Credit: ESA/Hubble & NASA
Explanation from: https://www.spacetelescope.org/images/potw1101a/

Atacama Large Millimeter/submillimeter Array

An alien green glow illuminates antennas that form part the Atacama Large Millimeter/submillimeter Array (ALMA), located on Chajnantor Plateau, high up in the Chilean Atacama desert. Above, the recognisable glow of the Milky Way and Magellanic Clouds is seen amongst a sea of stars in the night sky.

Image Credit: A. Duro/ESO
Explanation from: http://www.eso.org/public/images/duro_8130-cc/

The Milky Way Galaxy above trees in Salamanca

Salamanca, Spain

March 20, 2015

Image Credit & Copyright: César Vega Toledano

Hubble snaps close-up of the Tarantula Nebula

Hubble has taken this stunning close-up shot of part of the Tarantula Nebula. This star-forming region of ionised hydrogen gas is in the Large Magellanic Cloud, a small galaxy which neighbours the Milky Way. It is home to many extreme conditions including supernova remnants and the heaviest star ever found. The Tarantula Nebula is the most luminous nebula of its type in the local Universe.

Image Credit: NASA, ESA
Explanation from: http://spacetelescope.org/images/heic1105a/

Hubble image of galaxy cluster MACS J0717.5+3745

This enormous image shows Hubble’s view of massive galaxy cluster MACS J0717.5+3745. The large field of view is a combination of 18 separate Hubble images.

Studying the distorting effects of gravity on light from background galaxies, a team of astronomers has uncovered the presence of a filament of dark matter extending from the core of the cluster. This is one of the first positive detections of a filament, and the most precise to date.

Using additional observations from ground-based telescopes, the team were able to map the filament’s structure in three dimensions, the first time this has ever been done.

Image Credit: NASA, ESA, Harald Ebeling, Jean-Paul Kneib (LAM)
Explanation from: https://www.spacetelescope.org/images/heic1215b/

Hubble view of the huge star formation region N11 in the Large Magellanic Cloud

This broad vista of young stars and gas clouds in our neighbouring galaxy, the Large Magellanic Cloud, was captured by the NASA/ESA Hubble Space Telescope’s Advanced Camera for Surveys (ACS). This region is named LHA 120-N 11, informally known as N11, and is one of the most active star formation regions in the nearby Universe. This picture is a mosaic of ACS data from five different positions and covers a region about six arcminutes across.

Image Credit: NASA, ESA and Jesús Maíz Apellániz
Explanation from: https://www.spacetelescope.org/images/heic1011a/

Karymsky Volcano Eruption

Kamchatka Peninsula, Russia

July 13, 2004

Image Credit: Alexander Belousov

Supercell over Wyoming

Wright-Newcastle, Wyoming, USA

May 18, 2014

Image Credit & Copyright: Basehunters Chasing

NASA's SDO Captures Images of a Mid-Level Solar Flare

The Sun emitted a mid-level solar flare, peaking at 8:29 pm EDT on April 17, 2016. NASA’s Solar Dynamics Observatory, which watches the Sun constantly, captured an image of the event. Solar flares are powerful bursts of radiation. Harmful radiation from a flare cannot pass through Earth's atmosphere to physically affect humans on the ground, however -- when intense enough -- they can disturb the atmosphere in the layer where GPS and communications signals travel.

NOAA's Space Weather Prediction Center states that "moderate radio blackouts were observed" during the peak of the flare. Such radio blackouts are only ongoing during the course of a flare, and so they have since subsided. NOAA's Space Weather Prediction Center is the U.S. government's official source for space weather forecasts, watches, warnings and alerts.

This flare is classified as an M6.7 class flare. M-class flares are a tenth the size of the most intense flares, the X-class flares. The number provides more information about its strength. An M2 is twice as intense as an M1, an M3 is three times as intense, etc.

A black spot on the Sun is visible in the upper right of this image captured by NASA's SDO. Such spots are evidence that this is an area of complex magnetic activity on the Sun, which can sometimes lead to solar eruptions sending light and radiation out into space. This region produced a solar flare at 8:29 p.m. EDT on April 17, 2016.

This flare came from an area of complex magnetic activity on the Sun – known as an active region, and in this case labeled Active Region 2529 – which has sported a large dark spot, called a sunspot, over the past several days. This sunspot has changed shape and size as it slowly made its way across the Sun’s face over the past week and half. For much of that time, it was big enough to be visible from the ground without magnification and is currently large enough that almost five Earths could fit inside. This sunspot will rotate out of our view over the right side of the Sun by April 20, 2016. Scientists study such sunspots in order to better understand what causes them to sometimes erupt with solar flares

Image & Video Credit: NASA/SDO/Goddard
Explanation from: http://www.nasa.gov/feature/goddard/2016/nasas-sdo-captures-images-of-a-mid-level-solar-flare

Comparison of the Sun to VY Canis Majoris

The Sun

The Sun is the star at the center of the Solar System and is by far the most important source of energy for life on Earth. It is a nearly perfect spherical ball of hot plasma, with internal convective motion that generates a magnetic field via a dynamo process. Its diameter is about 109 times that of Earth, and it has a mass about 330,000 times that of Earth, accounting for about 99.86% of the total mass of the Solar System. About three quarters of the Sun's mass consists of hydrogen; the rest is mostly helium, with much smaller quantities of heavier elements, including oxygen, carbon, neon and iron.

The Sun is a G-type main-sequence star (G2V) based on spectral class and it is informally referred to as a yellow dwarf. It formed approximately 4.6 billion years ago from the gravitational collapse of matter within a region of a large molecular cloud. Most of this matter gathered in the center, whereas the rest flattened into an orbiting disk that became the Solar System. The central mass became increasingly hot and dense, eventually initiating nuclear fusion in its core. It is thought that almost all stars form by this process.

The Sun is roughly middle aged and has not changed dramatically for over four billion years, and will remain fairly stable for more than another five billion years. However, after hydrogen fusion in its core has stopped, the Sun will undergo severe changes and become a red giant. It is calculated that the Sun will become sufficiently large to engulf the current orbits of Mercury, Venus, and possibly Earth.

The enormous effect of the Sun on Earth has been recognized since prehistoric times, and the Sun has been regarded by some cultures as a deity. Earth's movement around the Sun is the basis of the solar calendar, which is the predominant calendar in use today.

VY Canis Majoris

VY Canis Majoris (VY CMa) is a red hypergiant star located in the constellation Canis Major. It is one of the largest stars (at one time it was the largest known) and also one of the most luminous of its type, and has a radius of approximately 1,420 ± 120 solar radii (equal to a diameter of 13.2 astronomical units, or about 1,976,640,000 km), and is located about 1.2 kiloparsecs (3,900 light-years) from Earth.

VY Canis Majoris is a single star categorized as a semiregular variable with an estimated period of 2,000 days. It has an average density of 5 to 10 mg/m3. If placed at the center of the Solar System, VY Canis Majoris's surface would extend beyond the orbit of Jupiter, although there is still considerable variation in estimates of the radius.

Explanation from: https://en.wikipedia.org/wiki/Sun and https://en.wikipedia.org/wiki/VY_Canis_Majoris

Volcán de Colima Eruption

Colima, Mexico

January 21, 2015

Image Credit & Copyright: Webcams de México

Comet 252P/LINEAR, Galactic Center and Auxiliary Telescope

This Auxiliary Telescope at the Very Large Telescope (VLT), located at the Paranal Observatory in Chile, looks to be pointing at the greenish emerald glow of the comet 252P/LINEAR high above it.

Discovered in April 2000, 252P/LINEAR is a relative newcomer to the inner Solar System, traveling between the orbit of Jupiter and the orbit of Earth. A couple of days ago, in March 2016, it passed particularly close to the Earth, at a distance of only 5.2 millions kilometers, ranking as the fifth closest recorded passage of a comet. It can still be admired in the southern hemisphere. The green colour arises from fluorescing carbon-based gas surrounding the comet.

This gem of a picture was taken by the ESO Photo Ambassador Babak A. Tafreshi. He has just started out on ESO’s Fulldome Expedition, during which he will be taking more spectacular pictures from ESO’s observatories and of the southern hemisphere night sky.

Image Credit: ESO/B. Tafreshi
Explanation from: http://www.eso.org/public/unitedkingdom/images/potw1615a/

Part of the Coalsack Nebula

This image from the Wide Field Imager on the MPG/ESO 2.2-metre telescope shows part of the huge cloud of dust and gas known as the Coalsack Nebula. The dust in this nebula absorbs and scatters the light from background stars.

Image Credit: ESO

The MACS J0416.1-2403 Galaxy Cluster

At first glance, this cosmic kaleidoscope of purple, blue and pink offers a strikingly beautiful — and serene — snapshot of the cosmos. However, this multi-coloured haze actually marks the site of two colliding galaxy clusters, forming a single object known as MACS J0416.1-2403 (or MACS J0416 for short).

MACS J0416 is located about 4.3 billion light-years from Earth, in the constellation of Eridanus. This new image of the cluster combines data from three different telescopes: the NASA/ESA Hubble Space Telescope (showing the galaxies and stars), the NASA Chandra X-ray Observatory (diffuse emission in blue), and the NRAO Jansky Very Large Array (diffuse emission in pink). Each telescope shows a different element of the cluster, allowing astronomers to study MACS J0416 in detail.

As with all galaxy clusters, MACS J0416 contains a significant amount of dark matter, which leaves a detectable imprint in visible light by distorting the images of background galaxies. In this image, this dark matter appears to align well with the blue-hued hot gas, suggesting that the two clusters have not yet collided; if the clusters had already smashed into one another, the dark matter and gas would have separated. MACS J0416 also contains other features — such as a compact core of hot gas — that would likely have been disrupted had a collision already occurred.

Together with five other galaxy clusters, MACS J0416 is playing a leading role in the Hubble Frontier Fields programme, for which this data was obtained. Owing to its huge mass, the cluster is in fact bending the light of background objects, acting as a magnifying lens. Astronomers can use this phenomenon to find galaxies that existed only hundreds of million years after the big bang.

Image Credit: NASA, ESA, CXC, NRAO/AUI/NSF, STScI, and G. Ogrean
Explanation from: https://www.spacetelescope.org/images/potw1612a/

The star cluster IC 4651

This rich view of a tapestry of colourful stars was captured by the Wide Field Imager (WFI) camera, on the MPG/ESO 2.2-metre telescope at ESO’s La Silla Observatory in Chile. It shows a open cluster of stars known as IC 4651, a stellar grouping that lies at in the constellation of Ara (The Altar).

Image Credit: ESO

The UGC 4459 Galaxy

Despite being less famous than their elliptical and spiral galactic cousins, irregular dwarf galaxies, such as the one captured in this NASA/ESA Hubble Space Telescope image, are actually one of the most common types of galaxy in the universe. Known as UGC 4459, this dwarf galaxy is located approximately 11 million light-years away in the constellation of Ursa Major (The Great Bear), a constellation that is also home to the Pinwheel Galaxy (M101), the Owl Nebula (M97), Messier 81, Messier 82 and several other galaxies all part of the M81 group.

UGC 4459’s diffused and disorganized appearance is characteristic of an irregular dwarf galaxy. Lacking a distinctive structure or shape, irregular dwarf galaxies are often chaotic in appearance, with neither a nuclear bulge — a huge, tightly packed central group of stars — nor any trace of spiral arms — regions of stars extending from the center of the galaxy. Astronomers suspect that some irregular dwarf galaxies were once spiral or elliptical galaxies, but were later deformed by the gravitational pull of nearby objects.

Rich with young blue stars and older red stars, UGC 4459 has a stellar population of several billion. Though seemingly impressive, this is small when compared to the 200 to 400 billion stars in the Milky Way!

Observations with Hubble have shown that because of their low masses of dwarf galaxies like UGC 4459, star formation is very low compared to larger galaxies. Only very little of their original gas has been turned into stars. Thus, these small galaxies are interesting to study to better understand primordial environments and the star formation process.

Image Credit: ESA/Hubble and NASA, Judy Schmidt
Explanation from: http://www.nasa.gov/image-feature/goddard/2016/hubble-peers-at-a-distinctly-disorganized-dwarf-galaxy

Hubble Frontier Fields view of Abell 2744

Abell 2744, nicknamed Pandora’s Cluster, was the first of six targets within the Frontier Fields programme, which together have produced the deepest images of gravitational lensing ever made. The cluster is thought to have a very violent history, having formed from a cosmic pile-up of multiple galaxy clusters.

Image Credit: NASA, ESA and the HST Frontier Fields team (STScI)