NASA’s space telescope has captured a rather impressive image of a thin, glittering streak of stars known as the spiral galaxy ESO 121-6, which lies in the southern constellation of Pictor (The Painter’s Easel).
Viewed almost exactly side-on, the intricate structure of the swirling arms is hidden, but the full length of the galaxy can be seen - including the intense glow from the central bulge, a dense region of tightly packed young stars located at the center of the spiral arms.
Astronomers Identify the Stellar Patrons of the Milky Way Bar
Scientists with the Sloan Digital Sky Survey III (SDSS-III) have announced the discovery of hundreds of stars rapidly moving together in long, looping orbits around the center of our Galaxy. “The best explanation for their orbits is that these stars are part of the Milky Way bar,” says David Nidever, a Dean B. McLaughin Fellow in the Astronomy Department at the University of Michigan. “We know that the bar plays an important role in determining the structure of the Galaxy, so learning more about these stars will help us understand the whole Galaxy, even out here in the spiral arms.”
The team’s discovery came from accurately measuring the speeds of thousands of stars near the center of the Milky Way. The center of our Galaxy is 30,000 light-years away—close by cosmic standards—yet we know surprisingly little about it, because the Galaxy’s dusty disk hides it from view. In spite of this blind spot, though, we do know a key fact about our Galaxy: like many spiral galaxies, the Milky Way has a ‘bar’ of stars that orbit together around the Galactic Center.
A polar-ring galaxy is a type of galaxy in which an outer ring of gas and stars rotates over the poles of the galaxy. These polar rings are thought to form when two galaxies gravitationally interact with each other.
A new galaxy class has been identified using observations from ESO’s Very Large Telescope (VLT), the Gemini South telescope, and the Canada-France-Hawaii Telescope (CFHT). Nicknamed “green bean galaxies” because of their unusual appearance, these galaxies glow in the intense light emitted from the surroundings of monster black holes and are amongst the rarest objects in the Universe.
Many galaxies have a giant black hole at their centre that causes the gas around it to glow. However, in the case of green bean galaxies, the entire galaxy is glowing, not just the centre. These new observations reveal the largest and brightest glowing regions ever found, thought to be powered by central black holes that were formerly very active but are now switching off.
Astronomer Mischa Schirmer of the Gemini Observatory had looked at many images of the distant Universe, searching for clusters of galaxies, but when he came across one object in an image from the Canada-France-Hawaii Telescope he was stunned — it looked like a galaxy, but it was bright green. It was unlike any galaxy he had ever seen before, something totally unexpected. He quickly applied to use ESO’s Very Large Telescope to find out what was creating the unusual green glow.
“ESO granted me special observing time at very short notice and just a few days after I submitted my proposal, this bizarre object was observed using the VLT,” says Schirmer. “Ten minutes after the data were taken in Chile, I had them on my computer in Germany. I soon refocused my research activities entirely as it became apparent that I had come across something really new.”
The new object has been labelled J224024.1−092748 or J2240. It lies in the constellation of Aquarius (The Water Bearer) and its light has taken about 3.7 billion years to reach Earth.
After the discovery, Schirmer’s team searched through a list of nearly a billion other galaxies and found 16 more with similar properties, which were confirmed by observations made at the Gemini South telescope. These galaxies are so rare that there is on average only one in a cube about 1.3 billion light-years across. This new class of galaxies has been nicknamed green bean galaxies because of their colour and because they are superficially similar to, but larger than, green pea galaxies.
In many galaxies the material around the supermassive black hole at the centre gives off intense radiation and ionises the surrounding gas so that it glows strongly. These glowing regions in typical active galaxies are usually small, up to 10% of the diameter of the galaxy. However, the team’s observations showed that in the case of J2240, and other green beans spotted since, it is truly huge, spanning the entire object. J2240 displays one of the biggest and brightest such regions ever found. Ionised oxygen glows bright green, which explains the strange colour that originally caught Schirmer’s attention.
“These glowing regions are fantastic probes to try to understand the physics of galaxies — it’s like sticking a medical thermometer into a galaxy far, far away,” says Schirmer. “Usually, these regions are neither very large nor very bright, and can only be seen well in nearby galaxies. However, in these newly discovered galaxies they are so huge and bright that they can be observed in great detail, despite their large distances.” — Astronomer Mischa Schirmer of the Gemini Observatory
Distance: 70,000,000 light-years away in the Constellation Eridanus
The large face-on grand design spiral galaxy NGC 1232 has undoubtedly interacted in complex ways with its smaller irregular companion galaxy NGC 1232A and that interaction has left an indelible mark on the larger galaxy.
The sweeping spiral arms appear to be “bent” in areas rather than the gently curving structures seen in undisturbed spiral galaxies. This aberration of the arms is likely due to gravitational encounters with NGC 1232A as it orbits the larger spiral. Radiowave studies indicate a large envelope of neutral gas extending well beyond the optical extent of the galaxy.
Rotational velocity measurements of the galaxies huge spiral arms suggest a large component of dark matter comprising NGC 1232. NGC1232 spans some 200,000 light years making it almost twice the size of the Milky Way.
Astronomers have seen a distant galaxy that blasts away material with two trillion times the energy the sun emits — the biggest such eruption ever seen. That ejection of matter could answer an important question about the universe: why are the black holes in the centers of galaxies so light?
Image: Artist’s impression of the huge outflow ejected from the quasar SDSS J1106+1939 Credit: ESO/L. Calçada
Computer models of the early universe usually produce a virtual cosmos that looks like ours except for one thing. The ratio of the mass of black holes in galaxy centers to the rest of the matter in galaxies is larger in the simulations than in the real universe.
Scientists think somehow galaxies are ridding themselves of much of the mass that would have ended up falling into their central black holes. However, until now researchers have been at a lack for an explanation of how this might happen.
To expel matter from galaxies takes energy. “We needed some input of energy from supermassive black holes,” Nahum Arav, an astrophysicist at Virginia Tech.
Supermassive black holes are obvious candidates, because they are the most energetic objects known. Some galaxies containing active black holes, called quasars, shine more brightly than anything else in the universe. “Our simulations showed that if we allowed the quasar to release a lot of mechanical energy, then the masses of galaxies would match observations,” Arav said.
Arav led a team that observed a quasar, called SDSS J1106+1939, which dates back to when the universe was only 3 billion years old (it is now about 13.7 billion years of age). Most quasars are millions or even billions of light-years distant, which means we see them as they were long ago. As such, they offer a unique window back in time, to when galaxies were young.
NGC 6946, also known as the Fireworks Galaxy, is a face-on spiral galaxy about 10 million light years away beyond a multitude of forground stars within our own galaxy. It spans nearly 40000 light-years across. Nine supernovae have been discovered in NGC 6946 since 1917, which is a sign of an abnormally high star formation rate.
Pinwheel Galaxy: M101
M101, also known as the Pinwheel Galaxy, is located 25 million light years away in the constellation Ursa Major. It is about 170,000 light years across, almost twice the size of the Milky Way.
This image is a composite of data from four different telescopes, created to map different forms of activity in the region. Red, infrared light, shows dust lanes heated from new stars. Blue indicates ultraviolet from young stars. Yellow is visible light from stars tracing dust lanes. Purple, x-rays, shows high energy emissions from supernovae and hot matter falling into black holes.
Image from National Geographic, information from National Geographic and NASA.
100,000 Stars: An Interactive Exploration of the Milky Way Galaxy
100,000 Stars is a new experiment for Chrome web browsers (or any other WebGL browser like Firefox or Safari) that lets you interactively explore the Milky Way galaxy with your mouse and scroll wheel.
Hoag’s Object [1521 x 1489]
The large stellar association cataloged as NGC 206 is nestled within the dusty arms of neighboring spiral galaxy Andromeda (M31), 2.5 million light-years distant.
Seen near the center of this gorgeous close-up of the southwestern extent of Andromeda’s disk, the bright, blue stars of NGC 206 indicate its youth. Its youngest massive stars are less than 10 million years old.
Much larger than the clusters of young stars in the disk of our Milky Way galaxy known as open or galactic clusters, NGC 206 spans about 4,000 light-years. That’s comparable in size to the giant stellar nurseries NGC 604 in nearby spiral M33 and the Tarantula Nebula, in the Large Magellanic Cloud.