Archive for the ‘Stiri’ Category

NASA’s Chandra X-ray Observatory, in orbit since 1999, studies the high-energy Universe, where black holes, exploding stars, and mysterious matter hold sway.

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Over three hundred years ago, a very large star ran out of fuel and collapsed. This event created an explosion, known as a supernova, which then produced an expanding field of debris.


Since the 1980s, astronomers have known about a mysterious class of objects that they call „ultraluminous X-ray sources,” or ULXs.

Image courtesy SDO/NASA

A solar flare explodes on May 9 in an image captured by NASA’s Solar Dynamics Observatory.

The phenomenon was short-lived and didn’t spark any coronal mass ejections, huge clouds of charged solar particles that erupt from the sun’s upper atmosphere.

The flare is shown in the 131 Angstrom wavelength of light—typically colored teal—which gave scientists the most detailed picture of the flare.

(See „New ‘Sunquake’ Trigger Found: Huge Solar Belches.”)

 

Image courtesy ESA/PACS/SPIRE, CEA/CNRS/INSU

The Cygnus-X stellar nursery stars in a „stunning” infrared picture released May 10 by the European Space Agency’s Herschel space observatory.

The chaotic jumble of dust and gas is an extremely active region of giant-star birth in the Cygnus constellation, some 4,500 light-years from Earth. (See another infrared picture of the Cygnus constellation.)

„Shocking” find may redraw picture of solar system’s cosmic shield.

The young star LL Ori forms a bow shock as it moves through the Orion Nebula.

Image courtesy STScI/AURA/NASA

Andrew Fazekas

for National Geographic News

Published May 10, 2012

The sun is moving through the Milky Way slower than previously thought, according to new data from a NASA spacecraft.

From its orbit around Earth, the Interstellar Boundary Explorer (IBEX) satellite measured the speeds of interstellar particles entering at the fringes of our solar system, 9 billion miles (14.5 billion kilometers) from the sun.

(Related: „‘Alien’ Particles Found Invading Our Solar System—A First.”)

Plugging the new data into computer models, the IBEX team calculates that the sun is moving at about 52,000 miles (83,700 kilometers) an hour—about 7,000 miles (11,000 kilometers) slower than thought.

The discovery suggests that the protective boundary separating our solar system from the rest of the galaxy is missing a bow shock, a major structural component thought to control the influx of high-energy cosmic rays.

(See „New Hubble Videos Show Star Jets in Action.”)

The sun is constantly sending out charged particles in all directions, forming a cocoon around the solar system called the heliosphere.

Like a boat moving through water, it’s long been thought that the „bow” of the heliosphere forms a crescent-shaped shockwave as our solar system plows through the surrounding cloud of interstellar gas. (See „Solar System’s ‘Nose’ Found; Aimed at Constellation Scorpius.”)

But the new IBEX findings mean the sun is moving so slow that pressure from material flowing around the heliosphere is 25 percent lower than expected—not enough for a bow shock.

Until now, „all the solar system models and theories included a bow shock,” said study leader David McComas of the Southwest Research Institute in San Antonio, Texas.

„Having learned for nearly three decades about it, I was literally shocked when we found it was missing.”

Cosmic-Ray Shielding Key for Life?

The absence of a bow shock is significant, McComas said, because it may indicate that the heliosphere is actually more robust than thought.

With less pressure from outside material, the boundary region isn’t being compressed and therefore weakened as much as expected, which means it should better repel cosmic rays.

(Related: „Solar System ‘Force Field’ Shrinks Fast.”)

And understanding exactly how the heliosphere acts as a gatekeeper for cosmic rays could help scientists evaluate the chances for life on other worlds.

According to McComas, some researchers believe that the cosmic rays that do get through the heliosphere can impact Earth’s climate, because the high-energy particles can ionize—or electrically charge—matter in the atmosphere, leading to heightened cloud formation and lightning generation.

Other experts think the particles could even be related to bursts of evolution or extinction in our planet’s history, because the radiation can influence DNA patterns.

(Also see „Ancient Mass Extinctions Caused by Cosmic Radiation, Scientists Say.”)

For now, the science behind how cosmic rays have influenced Earth is quite controversial, said Seth Redfield, an astronomer from Wesleyan University in Connecticut who was not involved with the new IBEX study.

Still, considering the rays’ expected effects, Redfield said, „it seems obvious to me that there will be scenarios or times when the cosmic-ray flux on a planet is important and [is] having a major influence on the evolution of the planetary atmosphere or even on biological processes on its surface.”

In that case, astronomers assessing the habitability of alien planets may need to start considering not only the chances for liquid water but also the strength of other stars’ protective cocoons, study leader McComas said.

„There is no doubt,” he said, „that questions about cosmic-ray shielding go right to the heart of some really important questions related to life as we know it.”

The slower-sun study appears in this week’s issue of the journal Science.

Odd orbits of remote objects hint at unseen world, new calculations suggest.

Richard A. Lovett in Timberline Lodge, Oregon
for
National Geographic News
Published May 11, 2012

An as yet undiscovered planet might be orbiting at the dark fringes of the solar system, according to new research.

Too far out to be easily spotted by telescopes, the potential unseen planet appears to be making its presence felt by disturbing the orbits of so-called Kuiper belt objects, said Rodney Gomes, an astronomer at the National Observatory of Brazil in Rio de Janeiro.

Kuiper belt objects are small icy bodies—including some dwarf planets—that lie beyond the orbit of Neptune.

Once considered the ninth planet in our system, the dwarf planet Pluto, for example, is one of the largest Kuiper belt objects, at about 1,400 miles (2,300 kilometers) wide. Dozens of the other objects are hundreds of miles across, and more are being discovered every year.

(See „Three New ‘Plutos’? Possible Dwarf Planets Found.”)

What’s intriguing, Gomes said, is that, according to his new calculations, about a half dozen Kuiper belt objects—including the remote body known as Sedna—are in strange orbits compared to where they should be, based on existing solar system models. (Related: „Pluto Neighbor Gets Downsized.”)

The objects’ unexpected orbits have a few possible explanations, said Gomes, who presented his findings Tuesday at a meeting of the American Astronomical Society in Timberline Lodge, Oregon.

„But I think the easiest one is a planetary-mass solar companion”—a planet that orbits very far out from the sun but that’s massive enough to be having gravitational effects on Kuiper belt objects.

Mystery Planet a Captured Rogue?

For the new work, Gomes analyzed the orbits of 92 Kuiper belt objects, then compared his results to computer models of how the bodies should be distributed, with and without an additional planet.

If there’s no distant world, Gomes concludes, the models don’t produce the highly elongated orbits we see for six of the objects.

How big exactly the planetary body might be isn’t clear, but there are a lot of possibilities, Gomes added.

Based on his calculations, Gomes thinks a Neptune-size world, about four times bigger than Earth, orbiting 140 billion miles (225 billion kilometers) away from the sun—about 1,500 times farther than Earth—would do the trick.

But so would a Mars-size object—roughly half Earth’s size—in a highly elongated orbit that would occasionally bring the body sweeping to within 5 billion miles (8 billion kilometers) of the sun.

Gomes speculates that the mystery object could be a rogue planet that was kicked out of its own star system and later captured by the sun’s gravity. (See „‘Nomad’ Planets More Common Than Thought, May Orbit Black Holes.”)

Or the putative planet could have formed closer to our sun, only to be cast outward by gravitational encounters with other planets.

However, actually finding such a world would be a challenge.

To begin with, the planet might be pretty dim. Also, Gomes’s simulations don’t give astronomers any clue as to where to point their telescopes—”it can be anywhere,” he said.

No Smoking Gun

Other astronomers are intrigued but say they’ll want a lot more proof before they’re willing to agree that the solar system—again—has nine planets. (Also see „Record Nine-Planet Star System Discovered?”)

„Obviously, finding another planet in the solar system is a big deal,” said Rory Barnes, an astronomer at the University of Washington. But, he added, „I don’t think he really has any evidence that suggests it is out there.”

Instead, he added, Gomes „has laid out a way to determine how such a planet could sculpt parts of our solar system. So while, yes, the evidence doesn’t exist yet, I thought the bigger point was that he showed us that there are ways to find that evidence.”

Douglas Hamilton, an astronomer from the University of Maryland, agrees that the new findings are far from definitive.

„What he showed in his probability arguments is that it’s slightly more likely. He doesn’t have a smoking gun yet.”

And Hal Levison, an astronomer at the Southwest Research Institute in Boulder, Colorado, says he isn’t sure what to make of Gomes’s finding.

„It seems surprising to me that a [solar] companion as small as Neptune could have the effect he sees,” Levison said.

But „I know Rodney, and I’m sure he did the calculations right.”