Funky Light Signal From Colliding Black Holes Explained (NASA)

Entangled by gravity and destined to merge, two candidate black holes in a distant galaxy appear to be locked in an intricate dance. Researchers using data from NASA's Galaxy Evolution Explorer (GALEX) and NASA's Hubble Space Telescope have come up with the most compelling confirmation yet for the existence of these merging black holes and have found new details about their odd, cyclical light signal.
The candidate black hole duo, called PG 1302-102, was first identified earlier this year using ground-based telescopes. The black holes are the tightest orbiting pair detected so far, with a separation not much bigger than the diameter of our solar system. They are expected to collide and merge in less than a million years, triggering a titanic blast with the power of 100 million supernovae.
Researchers are studying this pair to better understand how galaxies and the monstrous black holes at their cores merge -- a common occurrence in the early universe. But as common as these events were, they are hard to spot and confirm.
PG 1302-102 is one of only a handful of good binary black hole candidates. It was discovered and reported earlier this year by researchers at the California Institute of Technology in Pasadena, after they scrutinized an unusual light signal coming from the center of a galaxy. The researchers, who used telescopes in the Catalina Real-Time Transient Survey, demonstrated that the varying signal is likely generated by the motion of two black holes, which swing around each other every five years. While the black holes themselves don't give off light, the material surrounding them does.
In the new study, published in the Sept. 17 issue of Nature, researchers found more evidence to support and confirm the close-knit dance of these black holes. Using ultraviolet data from GALEX and Hubble, they were able to track the system's changing light patterns over the past 20 years.
"We were lucky to have GALEX data to look through," said co-author David Schiminovich of Columbia University in New York. "We went back into the GALEX archives and found that the object just happened to have been observed six times."
Hubble, which sees ultraviolet light in addition to visible and other wavelengths of light, had likewise observed the object in the past.
The ultraviolet light was important to test a prediction of how the black holes generate a cyclical light pattern. The idea is that one of the black holes in the pair is giving off more light -- it is gobbling up more matter than the other one, and this process heats up matter that emits energetic light. As this black hole orbits around its partner every five years, its light changes and appears to brighten as it heads toward us.
"It's as if a 60-Watt light bulb suddenly appears to be 100 Watts," explained Daniel D'Orazio, lead author of the study from Columbia University. "As the black hole light speeds away from us, it appears as a dimmer 20-Watt bulb."
What's causing the changes in light? One set of changes has to do with the "blue shifting" effect, in which light is squeezed to shorter wavelengths as it travels toward us in the same way that a police car's siren squeals at higher frequencies as it heads toward you. Another reason has to do with the enormous speed of the black hole.
The brighter black hole is, in fact, traveling at nearly seven percent the speed of light -- in other words, really fast. Though it takes the black hole five years to orbit its companion, it is traveling vast distances. It would be as if a black hole lapped our entire solar system from the outer fringes, where the Oort cloud of comets lies, in just five years. At speeds as high as this, which are known as relativistic, the light becomes boosted and brighter.
D'Orazio and colleagues modeled this effect based on a previous Caltech paper and predicted how it should look in ultraviolet light. They determined that, if the periodic brightening and dimming previously seen in the visible light is indeed due to the relativistic boosting effect, then the same periodic behavior should be present in ultraviolet wavelengths, but amplified 2.5 times. Sure enough, the ultraviolet light from GALEX and Hubble matched their predictions.
"We are strengthening our ideas of what's going on in this system and starting to understand it better," said Zoltan Haiman, a co-author from Columbia University who conceived the project.
The results will also help researchers understand how to find even closer-knit merging black holes in the future, what some consider the holy grail of physics and the search for gravitational waves. In the final moments before the ultimate union of two black holes, when they are tightly spinning around each other like ice skaters in a "death spiral," they are predicted to send out ripples in space and time. These so-called gravitational waves, whose existence follows from Albert Einstein's gravity theory published 100 years ago, hold clues about the fabric of our universe.
The findings are also a doorway to understanding other merging black holes across the universe, a widespread population that is only now beginning to yield its secrets.

Hubble Video

A Steve Knight video animation inspired by Hubble, with the music of Miriam Stockley.   Just sit back and enjoy!!!!!   https://www.youtube.com/watch?v=C7EalNrUrEU

Unlocking the Secrets of an Alien World's Magnetic Field

he strength of an alien world's magnetic field may have been deduced for the first time, by analyzing extraordinarily fast winds slamming against it from the planet's star, researchers say.

This research could help gauge the strength of other exoplanets' magnetic fields as well, scientists say.

The magnetic field of a planet can influence its evolution in crucial ways. "It works as a shield against stellar wind particles, which erode the atmosphere, so it is important to know if this field is big or small," said study lead author Kristina Kislyakova, a planetary scientist at the Austrian Academy of Sciences, in Graz.
In order to find out magnetic details about exoplanets — planets beyond our own solar system — Kislyakova and her colleagues investigated HD 209458b, which orbits a sunlike star in the constellation Pegasus about 150 light-years from Earth. This alien world is only about 70 percent the mass of Jupiter, but nearly 40 percent wider.

HD 209458b is a "hot Jupiter," a gas giant that orbits its star closer than Mercury does to the sun — specifically, HD 209458b circles its star at a distance of less than one-twentieth the distance between the sun and Earth. The extraordinary roasting that HD 209458b endures makes its atmosphere blow away like the tail of a comet. Astronomers have informally dubbed the world "Osiris," after the Egyptian god torn to pieces by his evil brother Set.

The researchers used NASA's Hubble Space Telescope to analyze the spectrum of light from HD 209458b as it passed in front of its star. Oddly, the data revealed hydrogen atoms moving away extremely quickly from the exoplanet in a lopsided manner.
To help explain the unusual way in which the hydrogen is blowing off HD 209458b, the scientists built a 3D model to account for all the known interactions between planetary atmospheres and stellar winds, the flow of particles that stream off stars. The model suggested the exoplanet had a magnetic field about 10 percent as strong as Jupiter's, and that the stellar wind blowing onto the planet was moving at about 895,000 mph (1.44 million km/h).

"The implication of these findings is improvement of our understanding of the worlds outside the solar system — some new light shed on bodies many light-years away from us," Kislyakova told Space.com.

Astronomers have confirmed more than 800 planets beyond our own solar system, and the discoveries keep rolling in. How much do you know about these exotic worlds?

These findings support prior research suggesting that hot Jupiters have relatively weak magnetic fields compared with their cooler gas giant cousins. Since hot Jupiters orbit very near their stars, they experience powerful gravitational pulls that likely slow the rates at which these hot Jupiters spin. This slower rotation should result in weaker magnetic fields, because a planet's magnetic field "is generated most effectively in fast-rotating cores of planets," Kislyakova said.

NASA Telescopes Find Clear Skies and Water Vapor on Exoplanet

Astronomers using data from three of NASA's space telescopes -- Hubble, Spitzer and Kepler -- have discovered clear skies and steamy water vapor on a gaseous planet outside our solar system. The planet is about the size of Neptune, making it the smallest planet from which molecules of any kind have been detected.
"This discovery is a significant milepost on the road to eventually analyzing the atmospheric composition of smaller, rocky planets more like Earth," said John Grunsfeld, assistant administrator of NASA's Science Mission Directorate. "Such achievements are only possible today with the combined capabilities of these unique and powerful observatories."
Clouds in a planet's atmosphere can block the view to underlying molecules that reveal information about the planet's composition and history. Finding clear skies on a Neptune-size planet is a good sign that smaller planets might have similarly good visibility.
"When astronomers go observing at night with telescopes, they say 'clear skies' to mean good luck," said Jonathan Fraine of the University of Maryland, College Park, lead author of a new study appearing in Nature. "In this case, we found clear skies on a distant planet. That's lucky for us because it means clouds didn't block our view of water molecules."

The planet, HAT-P-11b, is categorized as an exo-Neptune -- a Neptune-sized planet that orbits the star HAT-P-11. It is located 120 light-years away in the constellation Cygnus. This planet orbits closer to its star than does our Neptune to our sun, making one lap roughly every five days. It is a warm world thought to have a rocky core and gaseous atmosphere. Not much else was known about the composition of the planet, or other exo-Neptunes like it, until now.
Part of the challenge in analyzing the atmospheres of planets like this is their size. Larger Jupiter-like planets are easier to see because of their impressive girth and relatively inflated atmospheres. In fact, researchers already have detected water vapor in the atmospheres of those planets. The handful of smaller planets observed previously had proved more difficult to probe, partly because they all appeared to be cloudy.
In the new study, astronomers set out to look at the atmosphere of HAT-P-11b, not knowing if its weather would call for clouds. They used Hubble's Wide Field Camera 3 and a technique called transmission spectroscopy, in which a planet is observed as it crosses in front of its parent star. Starlight filters through the rim of the planet's atmosphere. If molecules like water vapor are present, they absorb some of the starlight, leaving distinct signatures in the light that reaches our telescopes.
Using this strategy, Hubble was able to detect water vapor in HAT-P-11b. But before the team could celebrate clear skies on the exo-Neptune, they had to show that starspots -- cooler "freckles" on the face of stars -- were not the real sources of water vapor. Cool starspots on the parent star can contain water vapor that might erroneously appear to be from the planet.
The team turned to Kepler and Spitzer. Kepler had been observing one patch of sky for years, and HAT-P-11b happens to lie in the field. Those visible-light data were combined with targeted Spitzer observations taken at infrared wavelengths. By comparing these observations, the astronomers figured out that the starspots were too hot to have any steam. It was at that point the team could celebrate detecting water vapor on a world unlike any in our solar system. This discovery indicates the planet did not have clouds blocking the view, a hopeful sign that more cloudless planets can be located and analyzed in the future.
"We think that exo-Neptunes may have diverse compositions, which reflect their formation histories," said study co-author Heather Knutson of the California Institute of Technology in Pasadena. "Now with data like these, we can begin to piece together a narrative for the origin of these distant worlds."
The results from all three telescopes demonstrate that HAT-P-11b is blanketed in water vapor, hydrogen gas and likely other yet-to-be-identified molecules. Theorists will be drawing up new models to explain the planet's makeup and origins.
"We are working our way down the line, from hot Jupiters to exo-Neptunes," said Drake Deming, a co-author of the study who is also from the University of Maryland. "We want to expand our knowledge to a diverse range of exoplanets."
The astronomers plan to examine more exo-Neptunes in the future, and hope to apply the same method to super-Earths -- massive, rocky cousins to our home world with up to 10 times the mass. Although our solar system doesn't have a super-Earth, NASA's Kepler mission is finding them in droves around other stars. NASA's James Webb Space Telescope, scheduled to launch in 2018, will search super-Earths for signs of water vapor and other molecules; however, finding signs of oceans and potentially habitable worlds is likely a ways off.
"The work we are doing now is important for future studies of super-Earths and even smaller planets, because we want to be able to pick out in advance the planets with clear atmospheres that will let us detect molecules," said Knutson.
Once again, astronomers will be crossing their fingers for clear skies.