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.
Since the 1980s, astronomers have known about a mysterious class of objects that they call “ultraluminous X-ray sources,” or ULXs.
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.
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.
Image courtesy STScI/AURA/NASA
Published May 10, 2012
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.
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.
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.
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
National Geographic News
Published May 11, 2012
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.
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.
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.”
Chandra observations have found the fastest wind ever coming from a disk around a stellar-mass black hole.
This record breaking wind is about 20 million miles per hour – about 3% the speed of light.
This wind may be carrying away much more material than the black hole is actually capturing.
This artist’s impression shows a binary system containing a stellar-mass black hole called IGR J17091-3624, or IGR J17091 for short. The strong gravity of the black hole, on the left, is pulling gas away from a companion star on the right. This gas forms a disk of hot gas around the black hole, and the wind is driven off this disk.
New observations with NASA’s Chandra X-ray Observatory have clocked the fastest wind ever seen blowing off a disk around this stellar-mass black hole. Stellar-mass black holes are born when extremely massive stars collapse and typically weigh between five and 10 times the mass of the Sun.
The record-breaking wind is moving about twenty million miles per hour, or about three percent the speed of light. This is nearly ten times faster than had ever been seen from a stellar-mass black hole, and matches some of the fastest winds generated by supermassive black holes, objects millions or billions of times more massive.
Another unanticipated finding is that the wind, which comes from a disk of gas surrounding the black hole, may be carrying away much more material than the black hole is capturing.
The high speed for the wind was estimated from a spectrum made by Chandra in 2011. A spectrum shows how intense the X-rays are at different energies. Ions emit and absorb distinct features in spectra, which allow scientists to monitor them and their behavior. A Chandra spectrum of iron ions made two months earlier showed no evidence of the high-speed wind, meaning the wind likely turns on and off over time.
|Fast Facts for IGR J17091-3624:|
|Coordinates (J2000)||RA 17h 09m 07.92s | Dec -36° 24′ 25.20″|
|Observation Dates||2 pointings on Aug 1 and Oct 6, 2011|
|Observation Time||16 hours 40 min|
|Obs. IDs||12405, 12406|
|References||King, A. et al, 2012, ApJ, 746, L20; arXiv:1112.3648|
|Distance Estimate||About 28,000 light years|
|Release Date||February 21, 2012|
A clump of dark matter has apparently been left behind after a violent collision of galaxy clusters.
This dark matter clump contains far fewer galaxies than would be expected if the dark matter and galaxies hung together.
Astronomers used Chandra, Hubble, and the Canada-France-Hawaii, and Subaru telescopes to observe Abell 520, which is 2.4 billion light years away.
This latest result agrees with a similar conclusion that was announced in 2007.
This composite image shows the distribution of dark matter, galaxies, and hot gas in the core of the merging galaxy cluster Abell 520, formed from a violent collision of massive galaxy clusters that is located about 2.4 billion light years from Earth.
Data from NASA’s Chandra X-ray Observatory show the hot gas in the colliding clusters colored in green. The gas provides evidence that a collision took place. Optical data from NASA’s Hubble Space Telescope and the Canada-France-Hawaii Telescope (CFHT) in Hawaii are shown in red, green, and blue. Starlight from galaxies within the clusters, derived from observations by the CFHT and smoothed to show the location of most of the galaxies, is colored orange.
The blue-colored areas pinpoint the location of most of the mass in the cluster, which is dominated by dark matter. Dark matter is an invisible substance that makes up most of the universe’s mass. The dark-matter map was derived from the Hubble observations, by detecting how light from distant objects is distorted by the cluster galaxies, an effect called gravitational lensing. The blend of blue and green in the center of the image reveals that a clump of dark matter (which can be seen by mousing over the image) resides near most of the hot gas, where very few galaxies are found.
This finding confirms previous observations of a dark-matter core in the cluster announced in 2007. The result could present a challenge to basic theories of dark matter, which predict that galaxies should be anchored to dark matter, even during the shock of a powerful collision.
|Fast Facts for Abell 520:|
|Credit||NASA, ESA, CFHT, CXO, M.J. Jee (University of California, Davis), and A. Mahdavi (San Francisco State University)|
|Scale||8.5 arcmin across (about 5.4 million light years)|
|Category||Groups & Clusters of Galaxies|
|Coordinates (J2000)||RA 04h 54m 03.80s | Dec +02º 53′ 33.00″|
|Observation Date||7 pointings between Oct 10, 2000 and Jan 11, 2008|
|Observation Time||148 hours 38 min. (6 days 4 hours 38 min)|
|Obs. ID||528, 4215, 7703, 9424-9426, 9430|
|Color Code||Optical (Red, Green, Blue); X-ray (Green); Mass (Blue); Luminosity (Orange)|
|References||arXiv:1202.6368; Jee, M. et al, 2012, ApJ 747, 96|
|Distance Estimate||2.4 billion light years (z=0.201)|
|Release Date||March 2, 2012|