February 2012

It’s famous that the universe is changeable: even the stars that become visible static and predictable every night are subject matter to change. This figure from the NASA Hubble Space Telescope shows planetary nebula Hen 3-1333. Planetary nebulae have not anything to do with planets — they truly represent the death throes of mid-sized stars like the sun. As they current out their outer layers, large, irregular globes of glowing gas develop around them, which appeared planet-like throughout the small telescopes that were used by their first explorers.
Nasa Space News -A Sheep in Wolf-Rayet's Clothing

The star at the heart of Hen 3-1333 is idea to have a mass of around 60% that of the sun, but not like the sun, its visible brightness varies significantly over time. Astronomers trust this variability is caused by a disc of dust which lies almost edge-on when vision from Earth, which occasionally obscures the star.

It is a Wolf–Rayet-type star — a late stage in the growth of sun-sized stars. These are named after (and share many observational personality with) Wolf–Rayet stars, which are a lot larger. Why the comparison? Both Wolf–Rayet and Wolf–Rayet type stars are hot and bright as their helium cores are showing: the former because of the strong stellar winds feature of these stars; the latter because the outer layers of the stars have been puffed left as the star runs low on fuel.

The showing helium core, rich with heavier elements, means that the exteriors of these stars are far hotter than the sun, typically 25,000 to 50,000 degrees Celsius (45,030 to 90,030 Fahrenheit). The sun has a moderately chilly surface temperature of just 5,500 degrees Celsius (9,932 Fahrenheit).

Many of the Universe's galaxies are like our own, displaying beautiful spiral arms wrapping around a bright nucleus. Examples in this stunning image, taken with the Wide Field Camera 3 on the NASA/ESA Hubble Space Telescope, include the tilted galaxy at the bottom of the frame, shining behind a Milky Way star, and the small spiral at the top center.


Other galaxies are even odder in shape. Markarian 779, the galaxy at the top of this image, has a distorted appearance because it is likely the product of a recent galactic merger between two spirals. This collision destroyed the spiral arms of the galaxies and scattered much of their gas and dust, transforming them into a single peculiar galaxy with a unique shape.

This galaxy is part of the Markarian catalogue, a database of over 1500 galaxies named after B. E. Markarian, the Armenian astronomer who studied them in the 1960s. He surveyed the sky for bright objects with unusually strong emission in the ultraviolet.

Ultraviolet radiation can come from a range of sources, so the Markarian catalog is quite diverse. An excess of ultraviolet emissions can be the result of the nucleus of an "active" galaxy, powered by a supermassive black hole at its center. It can also be due to events of intense star formation, called starbursts, possibly triggered by galactic collisions. Markarian galaxies are, therefore, often the subject of studies aimed at understanding active galaxies, starburst activity, and galaxy interactions and mergers.

NGC 6752 contains a high number of "blue straggler'' stars, some of which are visible in this image. These stars display characteristics of stars younger than their neighbors, despite models suggesting that most of the stars within globular clusters should have formed at approximately the same time. Their origin is therefore something of a mystery.

The above image looks like a hoard of gems fit for an emperor's collection, this deep sky object called NGC 6752 is in fact far more worthy of admiration. It is a globular cluster, and at over 10 billion years old is one the most ancient collections of stars known. It has been blazing for well over twice as long as our solar system has existed.

Studies of NGC 6752 may shed light on this situation. It appears that a very high number -- up to 38 percent -- of the stars within its core region are binary systems. Collisions between stars in this turbulent area could produce the blue stragglers that are so prevalent.

Lying 13,000 light-years distant, NGC 6752 is far beyond our reach, yet the clarity of Hubble's images brings it tantalizingly close.

The 355-foot-tall Mobile Launcher, or ML, behaved as expected during its move to Launch Pad 39B in November 2011, an analysis of multiple sensors showed. The top of the tower swayed less than an inch each way. The tests showed that computer models used in designing the massive structure were correct. The actual results varied less than 5 percent of what was predicted.

Confirm Designs For Mobile Launcher Tests

"This gives us much higher confidence in the models," Brown said. "We know that our approach is valid."

Engineers had the tower wired with dozens of accelerometers and strain gauges along with wind sensors to record the launcher's movement during its slow ride atop a crawler-transporter from a park site beside the Vehicle Assembly Building to the launch pad. Crawler drivers performed several speed changes during the six-mile journeys to and from the pad. While at the pad, which is being refurbished after decades of hosting space shuttles, workers connected ventilation, fire support and alarm systems and other water lines.

"We were measuring milli-g's," Brown said.

The ML, designed for the Ares I rocket of the cancelled Constellation program, is due for major modifications in the coming few years as it is strengthened to support the much-heavier SLS. It took two years to build and was completed in August 2010. The ML is the biggest structure of its kind since the Launch Umbilical Towers were constructed to support the Apollo/Saturn V. Those towers saw numerous modifications through their lives as trial-and-error showed where changes were needed, Brown said.

"Our goal here is to have less of those kinds of problems," Brown said.


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