NCC 1365

NGC 1365NGC 1365 is enormous. It is one of the largest galaxies known to astronomers—over 200,000 light-years across. This, plus the sharply defined bar of old stars across its structure is why it is also known as the Great Barred Spiral Galaxy. Astronomers believe that the Milky Way, which is only half as big, may look very similar to this galaxy. The bright centre of the galaxy is thought to be caused by huge amounts of superhot gas ejected from the ring of material circling a central black hole. Young luminous hot stars, born in the interstellar clouds, give the arms their blue color. The bar and spiral pattern rotates, with one full turn taking about 350 million years. NGC 1365 is about 61 million light-years away in the constellation Fornax (the Furnace).

Image Credit: ESO

Mergers and Acquisitions

NGC 799 & NGC 800This pair of galaxies, NGC 799 (below) and NGC 800 (above), is located in the constellation of Cetus (The Whale) about 300 million light-years away. Our face-on point of view lets us see these objects are both spiral galaxies with characteristic long arms winding towards a bright bulge at the center.

It may appear that these spiral galaxies are coexisting in an everlasting peace, but that is unlikely. What we see is probably the calm before the storm. Typically, when two galaxies are close enough, they interact over hundreds of millions of years through mutual gravitational attraction. In some cases, only minor interactions occur, causing shape distortions, but sometimes galaxies collide, merging to form a single, new and larger galaxy.

We’ll have to check back in a few hundred million years.

Image Credit: ESO

A Large Galaxy and Its Satellite

NGC1232The colors of the different regions of NGC 1232 stand out in this picture—the central areas contain older reddish stars while the spiral arms are populated by younger blue stars and many star-forming regions. This galaxy is about 100 million light-years away and about twice the size of our Milky Way galaxy. Note the companion galaxy at the lower left, shaped like the squashed greek letter “theta”. NGC 1232A, the satellite galaxy of NGC 1232, is thought to be the cause of unusual bending in the spiral arms in its larger neighbor.

Image Credit: ESO

A Dark Place in the Sky

The Coalsack and the Southern CrossThe Coalsack is probably the most prominent the dark nebulae visible to the naked eye. It casts a dark silhouette against the Milky Way’s bright stripe of stars in the southern sky. The Coalsack is located roughly 600 light-years away in the southern part of the constellation of Crux (the Southern Cross).

This apparently starless dark patch is really an opaque cloud of interstellar dust blocking the light from the background stars. Dust grains in the cloud redden the starlight that reaches us by absorbing blue light preferentially, so that the red stars shimmering in the northern and darkest part of the Coalsack appear deeper red than they would in the absence of this dust.

Image Credit: ESO

Ptolemy’s Cluster

M7Messier 7 (aka M7 or  Ptolemy’s Cluster) is an open cluster of stars in the constellation of Scorpius. The cluster is visible to the naked eye, close to the “stinger” of Scorpius.

M7 has been known since antiquity; it was first recorded by the 1st-century Greek-Roman astronomer Ptolemy, who described it as a nebula in AD 130. Italian astronomer Giovanni Batista Hodierna observed it in the mid 17th-century and counted 30 stars in it. In 1764, French astronomer Charles Messier catalogued the cluster as the seventh member in his list of comet-like objects. This image was recently taken by the 2.2-metre ESO telescope in Chile.

Image Credit: ESO

A Young Star

HD 97300A newly formed star lights up the surrounding gas and dust clouds like a streetlight in enveloping fog, creating reflection nebula IC 2631. The glowing region is the reflection nebula known as IC 2631. These nebulae are clouds of cosmic dust that reflect light from a nearby star into space. IC 2631 is the brightest nebula in the Chamaeleon Complex, a large region of such clouds with numerous newborn and still-forming protostars. The complex is around 500 light-years away in the southern constellation of Chameleon. IC 2631 is illuminated by one of the youngest, most massive, and brightest stars in its region. This neighborhood is full of star-making material which form dark nebulae such as the dark areas above and below IC 2631 in this picture. Dark nebulae are so densely filled with gas and dust that they block background starlight.

HD 97300 a T Tauri star, the youngest visible stage for relatively small stars.They have not yet started to fuse hydrogen into helium in their cores like normal main sequence stars but are just starting to glow by generating heat from gravitational contraction. As these stars mature, they will lose mass and shrink, but during their T Tauri phase, these stars have not yet contracted to the more modest size that they will maintain for billions of years as main sequence stars. Because these young stars already have surface temperatures similar to their main sequence phase and because T Tauri-phase objects are essentially jumbo versions of their later selves, they appear brighter in their oversized youth than they will as mature main sequence stars.

Image Credit: ESO

A Galaxy on Edge

Spiral Galaxy NGC 4565NGC 4565 is sometimes called the Needle Galaxy. It’s an edge-on spiral galaxy located about 30 million light-years away in the constellation Coma Berenices (Berenice’s Hair). Its bright yellowish central bulge juts out above impressive dust lanes. Its shape suggested that it is a barred spiral galaxy, and Spitzer Space Telescope data confirmed the presence of a central bar.

Image Credit: ESO


Seeing into the Heart of Mira A and its PartnerMain sequence stars such as the Sun wind up as red giants. Studying red giant stars tells astronomers about the future of the Sun (in a few billion years). It also tells us about how previous generations of stars spread the elements needed for life across the Universe. One of the most famous red giants in the sky is called Mira A, part of the binary system Mira about 400 light-years from Earth.

Mira A is an old star, already spewing out the products of its life’s work into space for recycling. Mira B, Mira A’s companion, orbits A at twice the distance from the Sun to Neptune.

Mira A is known to have a slow stellar wind which gently molds the surrounding material. Mira B is a hot, dense white dwarf with a fierce and fast stellar wind. Recent observations at millimeter wavelengths show how the interaction of the stellar winds from the two stars have created a complex nebula. The bubble at the centre is created by Mira B’s energetic wind inside Mira A’s more relaxed outflow. The heart-shaped bubble, formed some time in the last 400 years or so, is a relatively young object in astronomical terms.

Image Credit: ESO / S. Ramstedt (Uppsala University, Sweden) & W. Vlemmings (Chalmers University of Technology, Sweden)

A Ring of Fire

Fine Ring NebulaThis rather unusual planetary nebula is the Fine Ring Nebula. Planetary nebulae form from dying stars when they have expanded into a red giant phase and then eject a shell of gas as they evolve into the next phase of their stellar evolution, white dwarfs. Most planetary nebulae are either spherical or elliptical in shape, or are bipolar (featuring two symmetric lobes of material), but the Fine Ring Nebula looks like an almost perfectly circular ring. Astronomers believe that this unusually shaped planetary nebula was formed from a binary system. The interaction between the primary star and its orbiting companion shapes the ejected material.

The stellar object at the center of the Fine Ring Nebula does appear to be a binary system, orbiting with a period of 2.9 days. Observations suggest that the binary pair is almost perfectly face-on from our vantage point, implying that the planetary nebula’s structure is aligned in the same way. Our point of view looks down on the torus (doughnut shape) of ejected material, leading to the strikingly circular ring shape in the image.

Image Credit: ESO

NGC 300

ngc 300NGC 300 is a spiral galaxy in the constellation Sculptor. At one time, it was thought that NGC 300 was a part of a galaxy cluster know as th eSculptor Group. However, recent measurements show that it is closer to us in the relatively empty space between our Local Group and the Sculptor Group. It’s about 94,000 light-years in diameter, somewhat smaller than the Milky Way

Image Credit: ESO

The Milky Way

milkwayThis 360-degree panorama covers all of the southern and northern celestial hemispheres. The plane of our Milky Way Galaxy, which we see edge-on from Earth, is the luminous band across the image. The projection used in the picture puts the viewer in front of our Galaxy with the Galactic Plane running horizontally through the image. It’s almost as if we were looking at the Milky Way from the outside because the solar system is near the galactic rim. From our vantage point the general components of our spiral galaxy come clearly into view, including its disc as well as the central bulge and nearby satellite galaxies.

Image Credit: ESO / S. Brunier

A Dwarf (Helium) Flasher

White Dwarf ResurrectionPay no attention to the bright star in the center of the picture. The really interesting stellar object in the frame is that blob of red near the bottom. It’s a small white dwarf undergoing a helium flash.

Normally, the white dwarf stage is the end of the life cycle of a low-mass star, but in some rare cases, a star reignites in a helium flash and expands to its previous red giant state. When this happens, huge amounts of gas and dust are ejected before the star shrinks to become a white dwarf again.

A helium flash is a dramatic and short-lived series of events, and this star—Sakurai’s Object, named for the Japanese amateur astronomer who discovered it—has allowed astronomers a rare opportunity to study a helium flash as it occurred.

Image Credit: ESO

Partly Cloudy, For Now

The Dark Cloud Lupus 4Lupus 4, a spider-shaped blob of gas and dust, blots out background stars like a dark cloud on a moonless night. Although dark and gloomy for now, dense pockets of material within such clouds are where new stars form and where they will later burst into radiant life. Lupus 4 is about 400 light-years away, straddling the constellations of Lupus (The Wolf) and Norma (The Carpenter’s Square).

Image Credit: ESO

Visions of Future Past

ngc2207Over next couple of billion years, these two spiral galaxies will end up in a complete galactic merger—the two galaxies will become a single, larger one. They’re about 150 million light-years away in the constellation of Canis Major (the Great Dog), so what we can see now is what was happening 150 million years ago.

The gravitational attraction of NGC 2207, the larger of the pair, is already stirring things up throughout its smaller partner, distorting IC 2163’s shape and throwing stars and gas into long streamers that extend over 100,000 light-years. However, most of the space between stars in a galaxy is empty. When these galaxies collide, almost none of the stars in them will crash into another star.

This 150 million old image is a vision of the Milky Way’s future. About the time NGC 2207 and IC 2163 have finished their merger, the Milky Way will begin colliding with the Andromeda Galaxy.

Image Credit: ESO