Antares and Rho Ophiuchi

Credit & Copyright: D. Malin (AAO), AATB, ROE, UKS Telescope

Explanation: Why is the sky near Antares and Rho Ophiuchi so colorful? The colors result from a mixture of objects and processes. Fine dust illuminated from the front by starlight produces blue reflection nebulae. Gaseous clouds whose atoms are excited by ultraviolet starlight produce reddish emission nebulae. Backlit dust clouds block starlight and so appear dark. Antares, a red supergiant and one of the brighter stars in the night sky, lights up the yellow-red clouds on the upper left. Rho Ophiuchi lies at the center of the blue nebula on the right. The distant globular cluster M4 is visible just below Antares, and to the left of the red cloud engulfingSigma Scorpii. These star clouds are even more colorful than humans can see, emitting light across the electromagnetic spectrum.

Authors & editors: Robert Nemiroff (MTU) & Jerry Bonnell (USRA)

NGC 3314: When Galaxies Overlap

Credit: W. Keel and R. White, (U. Alabama, Tuscaloosa), Hubble Heritage Team (STScI/ AURA), NASA

Explanation: Can this be a spiral galaxy? In fact, NGC 3314 consists of two large spiral galaxies which just happen to almost exactly line-up. The foreground spiral is viewed nearly face-on, its pinwheel shape defined by young bright star clusters. But against the glow of the background galaxy, dark swirling lanes of interstellar dust are also seen to echo the face-on spiral’s structure. The dust lanes are surprisingly pervasive, and this remarkable pair of overlapping galaxies is one of a small number of systems in which absorption of visible light can be used to directly explore the distribution of dust in distant spirals. NGC 3314 is about 140 million light-years away in the southern constellation of Hydra. Just released, this color composite was constructed from Hubble Space Telescope images made in 1999 and 2000.

Authors & editors: Robert Nemiroff (MTU) & Jerry Bonnell (USRA)

Filaments In The Cygnus Loop

Credit: William P. Blair and Ravi Sankrit (Johns Hopkins University), NASA

Explanation: Subtle and delicate in appearance, these are filaments of shocked interstellar gas — part of the expanding blast wave from a violent stellar explosion. Recorded in November 1997 with the Wide Field and Planetary Camera 2 onboard the Hubble Space Telescope, the picture is a closeup of a supernova remnant known as the Cygnus Loop. The nearly edge-on view shows a small portion of the immense shock front moving toward the top of the frame at about 170 kilometers per second while glowing in light emitted by atoms of excited Hydrogen gas. Not just another pretty picture, this particular image has provided some dramatic scientific results. In 1999, researchers used it to substantially revise downward widely accepted estimates of distance and age for this classic supernova remnant. Now determined to lie only 1,440 light-years away, the Cygnus Loop is thought to have been expanding for 5 – 10 thousand years.

Authors & editors: Robert Nemiroff (MTU) & Jerry Bonnell (USRA)

A Superwind from the Cigar Galaxy

Credit: FOCAS, Subaru 8.3-m Telescope, NAOJ

Explanation: What’s lighting up the Cigar Galaxy? M82, as this irregular galaxy is also known, was stirred up by a recent pass near large spiral galaxy M81. This doesn’t fully explain the source of the red-glowing outwardly expanding gas, however. Recent evidence indicates that this gas is being driven out by the combined emerging particle winds of many stars, together creating a galactic “superwind.” The above recently released photograph from the new Subaru Telescope highlights the specific color of red light strongly emitted by ionized hydrogen gas, showing detailed filaments of this gas. The filaments extend for over 10,000 light years. The 12-million light-year distant Cigar Galaxy is the brightest galaxy in the sky in infrared light, and can be seen in visible light with a small telescope towards the constellation of Ursa Major.

Authors & editors: Robert Nemiroff (MTU) & Jerry Bonnell (USRA)

Eagle EGGs in M16

Credit: J. Hester & P. Scowen (ASU), HST, NASA

Explanation: Star forming regions known as “EGGs” are uncovered at the end of this giant pillar of gas and dust in the Eagle Nebula (M16). EGGs, short for evaporating gaseous globules, are dense regions of mostly molecular hydrogen gas that fragment and gravitationally collapse to form stars. Light from the hottest and brightest of these new stars heats the end of the pillar and causes further evaporation of gas – revealing yet more EGGs and more young stars. This picture was taken by the Wide Field and Planetary Camera on board the Hubble Space Telescope.

Authors & editors: Robert Nemiroff (MTU) & Jerry Bonnell (USRA)

 

Supernova 1994D and the Unexpected Universe

Credit: High-Z Supernova Search Team, HST, NASA

Explanation: Far away, long ago, a star exploded. Supernova 1994D, visible as the bright spot on the lower left, occurred in the outskirts of disk galaxy NGC 4526. Supernova 1994D was not of interest for how different it was, but rather for how similar it was to other supernovae. In fact, the light emitted during the weeks after its explosion caused it to be given the familiar designation of a Type Ia supernova. If allType 1a supernovae have the same intrinsic brightness, then the dimmer a supernova appears, the farther away it must be. By calibrating a precise brightness-distance relation, astronomers are able to estimate not only the expansion rate of the universe (parameterized by the Hubble Constant), but also the geometry of the universe we live in (parameterized by Omega and Lambda). The large number and great distances to supernovae measured over the past few years have been interpreted as indicating that we live in a previously unexpected universe.

Authors & editors: Robert Nemiroff (MTU) & Jerry Bonnell (USRA)

The Sombrero Galaxy from VLT

Credit: Peter Barthel (Kapteyn Inst.) et al., FORS1, VLT ANTU, ESO

Explanation: Why does the Sombrero Galaxy look like a hat? Reasons include the Sombrero’s unusually large and extended central bulge of stars, and dark prominent dust lanes that appear in a disk that we see nearly edge-on. Billions of old stars cause the diffuse glow of the extended central bulge. Close inspection of the bulge in the above photograph shows many points of light that are actually globular clusters. M104’s spectacular dust rings harbor many younger and brighter stars, and show intricate details astronomers don’t yet fully understand. The very center of the Sombrero glows across the electromagnetic spectrum, and is thought to house a large black hole. Light from the Sombrero Galaxy can be seen with a small telescope towards the constellation of Virgo.

Authors & editors: Robert Nemiroff (MTU) & Jerry Bonnell (USRA)

Neighboring Galaxy: The Large Magellanic Cloud

Credit & Copyright: AURA/ NOAO/ NSF

Explanation: The brightest galaxy visible from our own Milky Way Galaxy is the Large Magellanic Cloud (LMC). Visible predominantly from Earth’s Southern Hemisphere, the LMC is the second closest galaxy, neighbor to the Small Magellanic Cloud, and one of eleven known dwarf galaxies that orbit our Milky Way Galaxy. The LMC is an irregular galaxy composed of a bar of older red stars, clouds of younger blue stars, and a bright red star forming region visible near the top of the above image called the Tarantula Nebula. The brightest supernova of modern times, SN1987A, occurred in the LMC.

Authors & editors: Robert Nemiroff (MTU) & Jerry Bonnell (USRA)

M106: A Spiral Galaxy with a Strange Core

Credit: Ron & Beth Sharer, Steven White, AOP, KPNO, NOAO, NSF

Explanation: What’s happening at the center of spiral galaxy M106? A swirling disk of stars and gas, M106’s appearance is dominated by two bright spiral arms and dark dust lanes near the nucleus. Bright newly formed stars near their outer tips distinguish the spiral arms in the above photograph. The core of M106 glows brightly in radio waves and X-rays where twin jets have been found running the length of the galaxy. An unusual central glow makes M106 one of the closest examples of the Seyfert class of galaxies, where vast amounts of glowing gas are thought to be falling into a central massive black hole. M106, also designated NGC 4258, is a relatively close 25 million light years away, spans 30 thousand light years across, and can be seen with a small telescope towards the constellation of Canes Venatici.

Authors & editors: Robert Nemiroff (MTU) & Jerry Bonnell (USRA)

Galaxy Wars: M81 Versus M82

Credit & Copyright: Robert Gendler

Explanation: In the left corner, wearing a red nucleus surrounded by blue spiral arms, is M81. In the right corner, sporting light stars and dark dust lanes, is M82. These two mammoth galaxies have been locked in gravitational combat for the past billion years. The gravity from each galaxy dramatically affects the other during each hundred million-year pass. Last go-round, M82’s gravity likely raised circulating density waves rippling around M81 resulting in the richness of M81’s spiral arms. M81, though, left M82 a messy pulp of exploded stars and colliding gas so violent it emits bright X-rays. In both galaxies, colliding gas has created a recent abundance of bright new stars. In a few billion years only one galaxy will remain.

Authors & editors: Robert Nemiroff (MTU) & Jerry Bonnell (USRA)