NGC 3310

NGC 3310NGC 3310 is a grand design spiral galaxy in the constellation Ursa Major. It is also a starburst galaxy. (Starburst galaxies are undergoing an exceptionally high rate of star formation.) NGC 3310 probably collided with one of its satellite galaxies about 100 million years ago, triggering widespread star formation. The ring clusters of NGC 3310 have been undergoing starburst activity for at least the last 40 million years.

Image Credit: NASA

NGC 4206

A dusty spiral in VirgoNGC 4206 is about 70 million light-years away. It was imaged as part of a Hubble survey of nearby edge-on spiral galaxies made to measure the effect that the material between the stars, called the interstellar medium, has on the light that travels through it. Astronomers have been able to map the absorption and scattering of light by the material which causes objects to appear redder to distant observers.

Image Credit:  ESA / NASA
Acknowledgement: Nick Rose

A Supernova Remnant

DEM L 190These delicate filaments are actually sheets of debris from a stellar explosion in a neighboring galaxy, the Large Magellanic Cloud (LMC), a small companion galaxy to the Milky Way visible from the southern hemisphere. This remnant, know as N49 or DEM L 190, is from a massive star that died in a supernova blast thousands of years ago. This filamentary material will eventually be recycled into building new generations of stars in the LMC. Our own Sun and planets were formed from similar debris of supernovae that exploded in our own galaxy billions of years ago.

These filaments harbor a very powerful spinning neutron star that may be the central remnant from the supernova. It is quite common for the core of an exploded supernova star to become a spinning neutron star (or pulsar) after the immediate shedding of the supernova’s outer layers.  The pulsar in N 49 is spinning at a rate of once every 8 seconds. It also has a super-strong magnetic field a thousand trillion times stronger than Earth’s magnetic field. This places this star into the exclusive class of objects called “magnetars.”

Image Credit: NASA

Stars and Stripe

SN1006In 1006 A.D., observers from Africa to Europe to the Far East recorded the arrival of light from what is now called SN 1006, a tremendous supernova explosion of a white dwarf star nearly 7,000 light-years away. The supernova was probably the brightest star ever seen in recorded times. It surpassed Venus in the night time sky, only being outshone by the moon. It was visible during the day for weeks, and remained visible to the naked eye for at least two and a half years before fading away.

About 50 years ago, radio astronomers detected a nearly circular ring of material at the recorded position of the supernova. The ring was almost the same angular diameter as the full moon. The size of the remnant implied that the blast wave from the supernova had expanded at nearly 20 million miles per hour over the nearly 1,000 years since the explosion occurred.

Today, we know that SN 1006 has a diameter of nearly 60 light-years, and is still expanding at roughly 6 million miles per hour. Even at that speed, however, it takes observations years apart to detect significant outward motion of the shock wave. This Hubble image of a delicate ribbon of gas shows a very thin section of the supernova remnant. The location of the 1006 explosion is well out of the farme to the lower left. The shock wave is moving to the upper right.

Image Credit: NASA

The Backward Galaxy

backward galaxyThe Backward Galaxy (aka NGC4622) lies 111 million light years away in the constellation Centaurus. NGC 4622 is an example of a galaxy with leading spiral arms. In most spiral galaxies, the spiral arms trail; that is, the tips of the spiral arms are winding away from the center of the galaxy in the direction of the disk’s orbital rotation. In NGC4622, however, the outer arms are leading spiral arms; the tips of the spiral arms point towards the direction of disk rotation. This may be the result of a gravitational interaction between NGC 4622 and another galaxy or the result of a merger between NGC 4622 and a smaller object.

Image Credit: NASA

The Cartwheel Galaxy

Cartwheel GalaxyThe Cartwheel Galaxy (also known as ESO 350-40) is a lenticular and ring galaxy about 500 million light-years away in the constellation Sculptor. The ring resulted from a collision between two galaxies that would have been observed for the first time on Earth at the beginning of the Jurassic Period 200 million years ago. What we see today took 200 million years to develop, based on rate analysis of expanding gases.

Image Credit: NASA