Tag: astronomy

NASA science administrator Ed Weiler is retiring after 33 years

9:12 am

Science administrator Ed Weiler is retiring after almost 33 years at NASA.

Among Weiler’s many achievements, he was crucial to getting the Hubble Space Telescope launched. Even more important, though others had conceived the idea of using the shuttle to maintain Hubble, he designed the maintenance schedule for the telescope. Seven years before it was launched, he insisted that a regular schedule of repair missions be placed on the shuttle manifest. He also insisted that a duplicate of the telescope’s main camera be built, so that if anything went wrong with the first a repaired unit could be launched quickly. It was his foresight here that made the first repair of Hubble in December 1993 go so smoothly. For this, astronomers will always be grateful.

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A second large satellite will rain debris down in October

10:06 am

Even if UARS misses you today, don’t relax! A second large satellite, the 2.4 ton ROSAT X-Ray space telescope, is going to rain debris down late in October or early November.

On its ROSAT website, DLR estimates that “up to 30 individual debris items with a total mass of up to 1.6 tonnes might reach the surface of the Earth. The X-ray optical system, with its mirrors and a mechanical support structure made of carbon-fibre reinforced composite – or at least a part of it – could be the heaviest single component to reach the ground.”

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New exoplanets make astronomers long for a telescope to see them

2:39 pm

The plethora of new exoplanet discoveries has astronomers longing for a telescope that can see them up close.

Astronomers need either a giant space telescope equipped with a device for blocking starlight, or an interferometer, consisting of several telescopes flying in formation. NASA did develop a proposal for such a space telescope, called Terrestrial Planet Finder, and the European Space Agency hoped to fly a similar mission called Darwin. But budgetary constraints have left both missions in limbo, unlikely to advance to the front of either agency’s queue until well into the next decade. At the conference, Traub raised the issue. “People are not thinking deeply about the distant future. People are wrapped up with what they’re doing right now,” he says. “Clearly, I’m concerned.”

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A Yellow Supergiant Progenitor of a Massive Star Supernova in M51

3:31 pm

The uncertainty of science: Astronomers have determined that the star that went supernova in the Whirlpool Galaxy (M51) in June — making it the nearest supernova in 25 years — was a yellow supergiant star, not an aging red supergiant as predicted by theory. From the preprint paper:

Despite the canonical prediction that Type II supernovae arise from red supergiants, there is mounting evidence that some stars explode as yellow supergiants. A handful of Type II supernovae have been observed to arise from yellow supergiants: supernovae 1993J, 2008cn, and 2009kr. The locations of the progenitors on the Hertzsprung-Russell diagram shows clearly that these stars are not located on the predicted end points for single star stellar evolution tracks. In addition, despite arising from supposedly similar yellow supergiant progenitors, these supernovae display a wide range of properties.

The Hertzsprung-Russell diagram is a graph mapping the color of stars against their luminosity. Because color and brightness change as the star evolves over time, the graph is used by astronomers to track the birth, growth, and death of stars. That these yellow supergiants don’t appear to be at “the predicted end points for single star evolution” on the diagram is a serious problem for the theorists who have tried to explain what causes this particular type of supernova.

Which also means astronomers are still unable to tell us what stars in the sky are most likely to go supernova in the future.

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A giant storm on a distant star

8:56 am

Astronomers have spotted what they think is a giant storm on a distant star.

As part of a large survey of nearby brown dwarfs – objects that occupy the mass gap between dwarf stars and giant planets – the scientists used an infrared camera on the 2.5m telescope at Las Campanas Observatory in Chile to capture repeated images of a brown dwarf dubbed 2MASS J21392676+0220226, or 2MASS 2139 for short, over several hours. In that short time span, they recorded the largest variations in brightness ever seen on a cool brown dwarf.

“We found that our target’s brightness changed by a whopping 30 per cent in just under eight hours,” said PhD candidate Jacqueline Radigan, lead author of a paper to be presented this week at the Extreme Solar Systems II conference in Jackson Hole, Wyoming and submitted to the Astrophysical Journal. “The best explanation is that brighter and darker patches of its atmosphere are coming into our view as the brown dwarf spins on its axis,” said Radigan.

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Unknown objects in space

12:57 pm

Fermi list of object types

NASA’s Fermi Gamma-Ray Telescope today released an updated catalog of the last two years of its survey of the sky at high energy emissions. All told, there are 1873 objects in the catalog, more than half of which are supermassive black holes at the center of distant galaxies. You can see this all-sky map below the fold.

Many of the objects are quite familiar, such as the Crab Nebula, the remnant of a supernova that exploded a little less than a thousand years ago.

For decades, most astronomers regarded the Crab Nebula as the steadiest beacon at X-ray energies. But data from several orbiting instruments — including Fermi’s Gamma-ray Burst Monitor — now show unexpected variations. Astronomers have shown that since 2008, the nebula has faded by 7 percent at high energies, a reduction likely tied to the environment around its central neutron star.

Since 2007, Fermi and the Italian Space Agency’s AGILE satellite have detected several short-lived gamma-ray flares at energies hundreds of times higher than the nebula’s observed X-ray variations. In April, the satellites detected two of the most powerful yet recorded. To account for these “superflares,” scientists say that electrons near the pulsar must be accelerated to energies a thousand trillion times greater than that of visible light — and far beyond what can be achieved by the Large Hadron Collider near Geneva, Switzerland, now the most powerful particle accelerator on Earth.

What I, and many astronomers, find even most interesting about this catalog, however, is the large number of completely mysterious objects scattered across the sky, objects that emit powerful gamma rays but are not visible in any other wavelengths. All told, these unidentified objects comprise almost one third of the entire catalog.
» Read more

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Baby Star Found on Earth’s Doorstep

6:16 pm

A baby star has been found only 27 light years away.

AP Columbae lies in the constellation Columba the Dove, south of the brilliant constellation Orion. “AP Columbae is still contracting under gravity towards the main sequence,” says astronomer Adric Riedel of Georgia State University in Atlanta, whose team measured the star’s parallax—an indication of its distance—and discovered that the star is abnormally luminous. Although the star is dim and red, it’s four times as bright as it should be, because it’s twice the diameter of a main-sequence star of the same color.

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Kepler team pushes for mission extension

12:55 pm

The Kepler team pushes for a mission extension in order to find Earth-sized planets.

The Kepler spacecraft has hit an unexpected obstacle as it patiently watches the heavens for exoplanets: too many rowdy young stars. The orbiting probe detects small dips in the brightness of a star that occur when a planet crosses its face. But an analysis of some 2,500 of the tens of thousands of Sun-like stars detected in Kepler’s field of view has found that the stars themselves flicker more than predicted, with the largest number varying twice as much as the Sun. That makes it harder to detect Earth-sized bodies. As a result, the analysis suggests that Kepler will need more than double its planned mission life of three-and-a-half years to achieve its main goal of determining how common Earth-like planets are in the Milky Way.

While it is important to find those Earth-sized planets, to me the important discovery here is that Kepler is confirming what previous research has suggested: Stars like our Sun are generally far more active and variable than the Sun itself. Which means that either the Sun is unusual, or has been unusually inactive during recorded human history.

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The Hubble Space Telescope: Movie camera!

11:03 am

Using Hubble Space Telescope images taken over a 14 year period, a team of astronomers led by Patrick Hartigan of Rice University have produced six very short time-lapse movies, showing the changes that have occurred to a variety of interstellar jets and bow shocks over time. The one below is my favorite. They are all worth looking at, as they illustrate forcefully how the changeless heavens are not so changeless.

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The closest supernovae in almost 25 years

7:56 pm

Astronomers have spotted the closest supernovae in almost 25 years, only 21 million light years away.

The supernova, dubbed PTF 11kly, occurred in the Pinwheel Galaxy, located in the “Big Dipper,” otherwise known as the Ursa Major constellation. It was discovered by the Palomar Transient Factory (PTF) survey, which is designed to observe and uncover astronomical events as they happen. “We caught this supernova very soon after explosion. PTF 11kly is getting brighter by the minute. It’s already 20 times brighter than it was yesterday,” said Peter Nugent, the senior scientist at Berkeley Lab who first spotted the supernova. Nugent is also an adjunct professor of astronomy at UC Berkeley. “Observing PTF 11kly unfold should be a wild ride. It is an instant cosmic classic.”

Astronomers expect the supernova to continue to brighten over the next two weeks, when it should be visible to anyone using binoculars.

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When dust, pebbles, rocks, and boulders act like liquid

3:35 pm

The science team of Lunar Reconnaissance Orbiter released an intriguing picture yesterday of what scientists call a granular flow down the side of a five mile wide crater on the far side of the moon. Looking at the image, one would swear that the darker material flowing down the slope of the crater rim is a lava flow frozen in place.

lunar granular flow

However, according to the scientists, that is not what it is. Instead, this is merely debris left behind from an avalanche.
» Read more

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