vlas

Some galaxies have extremely bright cores, suggesting that they contain a supermassive black hole that is pulling in matter at a prodigious rate. Astronomers call these “active galaxies,” and Hercules A is one of them. In visible light, Hercules A looks like a typical elliptical galaxy. In X-ray light, however, Chandra detects a giant cloud of multimillion-degree gas (purple). This gas has been heated by energy generated by the infall of matter into a black hole at the center of Hercules A that is over 1,000 times as massive as the one in the middle of the Milky Way. Radio data (blue) show jets of particles streaming away from the black hole. The jets span a length of almost one million light years.  

Credit: X-ray: NASA/CXC/SAO, Optical: NASA/STScI, Radio: NSF/NRAO/VLA

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Legday with my darling @sussielemon today. Herre-jävla-gud!! So tired I almost couldn’t get out of the car when I got home. Not gonna be able to walk tomorrow, and I love it! 🙌
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"rapport of sun, moon, earth and all the constellations, what are the messages by you from distant stars to us?" — walt whitman 

"two possibilities exist: either we are alone in the universe or we are not. both are equally terrifying." - arthur c. clarke

astrophography by knate myers at the karl g. jansky very large array (vla), a radio astronomy observatory located on the plains of san agustin, fifty miles west of socorro, new mexico. the vla was perhaps made most famous by carl sagan in the original cosmos documentary, and in the movie “contact”, which was based on his novel.

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The Curious Channel 37 — Must-see TV For Radio Astronomy

Thanks to Channel 37, radio astronomers keep tabs on everything from the Sun to pulsars to the lonely spaces between the stars. This particular frequency, squarely in the middle of the UHF TV broadcast band, has been reserved for radio astronomy since 1963, when astronomers successfully lobbied the FCC to keep it TV-free.

Back then UHF TV stations were few and far between. Now there are hundreds, and I’m sure a few would love to soak up that last sliver of spectrum. Sorry Charley, the moratorium is still in effect to this day. Not only that, but it’s observed in most countries across the world.

So what’s so important about Channel 37? Well, it’s smack in the middle of two other important bands already allocated to radio astronomy – 410 Megahertz (MHz) and 1.4 Gigahertz (Gz). Without it, radio astronomers would lose a key window in an otherwise continuous radio view of the sky. Imagine a 3-panel bay window with the middle pane painted black. Who wants THAT?

Channel 37 occupies a band spanning from 608-614 MHz. A word about Hertz. Radio waves are a form of light just like the colors we see in the rainbow or the X-rays doctors use to probe our bones. Only difference is, our eyes aren’t sensitive to them. But we can build instruments like X-ray machines and radio telescopes to “see” them for us.

Every color of light has a characteristic wavelength and frequency. Wavelength is the distance between successive crests in a light wave which you can visualize as a wave moving across a pond. Waves of visible light range from one-millionth to one-billionth of a meter, comparable to the size of a virus or DNA molecule.

X-rays crests are jammed together even more tightly – one X-ray is only as big as an small atom. Radio waves fill out the opposite end of the spectrum with wavelengths ranging from baseball-sized to more than 600 miles (1000 km) long.

The frequency of a light wave is measured by how many crests pass a given point over a given time. If only one crest passes that point every second, the light beam has a frequency of 1 cycle per second or 1 Hertz. Blue light has a wavelength of 462 billionths of a meter and frequency of 645 trillion Hertz (645 Terahertz).

The higher the frequency, the greater the energy the light carries. X-rays have frequencies starting around 30 quadrillion Hertz (30 petahertz or 30 PHz), enough juice to damage body cells if you get too much exposure. Even ultraviolet light has power to burn skin as many of us who’ve spent time outdoors in summer without sunscreen are aware.

Radio waves are the gentle giants of the electromagnetic spectrum. Their enormous wavelengths mean low frequencies. Channel 37 radio waves have more modest frequencies of around 600 million Hertz (MHz), while the longest radio waves deliver crests almost twice the width of Lake Superior at a rate of 3 to 300 Hertz.

If Channel 37 were ever lost to TV, the gap would mean a loss of information about the distribution of cosmic rays in the Milky Way galaxy and rapidly rotating stars called pulsars created in the wake of supernovae. Closer to home, observations in the 608-614 MHz band allow astronomers track bursts of radio energy produced by particles blasted out by solar flares traveling through the sun’s outer atmosphere. Some of these can have powerful effects on Earth. No wonder astronomers want to keep this slice of the electromagnetic spectrum quiet. For more details on how useful this sliver is to radio astronomy, click HERE.

Just as optical astronomers seek the darkest sites for their telescopes to probe the most remote corners of the universe, so too does radio astronomy need slices of silence to listen to the faintest whispers of the cosmos.

image 1: The Very Large Array, one of the world’s premier astronomical radio observatories, consists of 27 radio antennas in a Y-shaped configuration 50 miles west of Socorro, New Mexico. Each antenna is 82 feet (25 m) in diameter. The data from the antennas is combined electronically to give the resolution of an antenna 22 miles (36 km) across. credit: NRAO/AUI and NRAO

image 2: Channel 37, a slice of the radio spectrum from 608 and 614 Megahertz (MHz) reserved for radio astronomy, sits in the middle of the UHF TV band. Click to see the full spectrum. credit: US Dept. of Commerce

image 3: The visible colors, infrared, radio, X-rays and gamma rays are all forms of light and comprise the electromagnetic spectrum. Here you can compare their wavelengths with familiar objects and see how their frequencies (bottom numbers) increase with decreasing wavelength. credit: ESA

image 4: Diagram showing what how Earth’s atmosphere allows visible light, a portion of infrared and radio light to reach the ground from outer space but filters shorter-wavelength, more dangerous forms of light like X-rays and gamma rays. To study the cosmos in these varieties of light, orbiting telescopes are required.

image 5: If our eyes could see radio light, this is what the sky would look like. What appear to be stars are actually distant galaxies glowing brightly with energy radiated as matter gets sucked down black holes in the cores. The wispy arcs and shells are the remnants of exploding supernovae. Since air molecules don’t scatter radio waves like they do visible light to create a blue sky, the sky would be dark even on a sunny day. credit: National Science Foundation

image 6: The sun as it would look in the radio portion of the spectrum at a frequency of 1.4 gigahertz (GHz). credit: National Radio Astronomy Observatory (NRAO/AUI)

Stay Curious! Watch: First Contact: Carl Sagan On Radio Astronomy

Magnetar Found at Giant Black Hole

Magnetized neutron star could test Einstein’s theory.

Dale Frail couldn’t resist the prospect of watching a black hole swallow its prey. Frail, who is in charge of the Very Large Array (VLA) of radio telescopes near Socorro in New Mexico, had seen a report last month about a long-lived X-ray flare emanating from the centre of the Milky Way, home to a supermassive black hole called Sagittarius A* (Sgr A*). Astronomers were speculating that the flare might be a sign that a gas cloud they had been tracking had begun its death spiral into the black hole.

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Best evidence yet for a high-energy jet emanating from the Milky Way’s black hole

Jets of high energy particles emanating from a black hole have been detected plenty of times before, but in other galaxies, that is — not from the supermassive black hole at the center of the Milky Way, known as Sagittarius A* (Sgr A*). Previous studies and other evidence suggested that perhaps there were jets – or ghosts of past jets – but many findings and studies often contradicted each other, and none were considered definitive.

Now, astronomers using Chandra X-ray Observatory and the Very Large Array (VLA) radio telescope have found strong evidence Sgr A* is producing a jet of high-energy particles.

“For decades astronomers have looked for a jet associated with the Milky Way’s black hole. Our new observations make the strongest case yet for such a jet,” said Zhiyuan Li of Nanjing University in China, lead author of a study in The Astrophysical Journal.

The supermassive black hole at the center of the Milky Way is about four million times more massive than our Sun and lies about 26,000 light-years from Earth.

While the common notion is that black holes inhale and ingest everything that comes their way, that’s not always true. Sometimes they reject small portions of incoming mass, pushing it away in the form of a powerful jet, and many times a pair of jets. These jets also feed the surroundings, releasing both mass and energy and likely play important roles in regulating the rate of formation of new stars.

Since Sgr A* is presently known to be consuming very little material, and so the jet is weak, making it difficult to detect. Astronomers don’t see another jet “shooting” in the opposite direction but that may be because of gas or dust blocking the line of sight from Earth or a lack of material to fuel the jet. Or there may be just a single jet.

The study shows the spin axis of Sgr A* is pointing in one direction, parallel to the rotation axis of the Milky Way, which indicates to astronomers that gas and dust have migrated steadily into Sgr A* over the past 10 billion years. If the Milky Way had collided with large galaxies in the recent past and their central black holes had merged with Sgr A*, the jet could point in any direction.

The jet appears to be running into gas near Sgr A*, producing X-rays detected by Chandra and radio emission observed by the VLA. The two key pieces of evidence for the jet are a straight line of X-ray emitting gas that points toward Sgr A* and a shock front — similar to a sonic boom — seen in radio data, where the jet appears to be striking the gas. Additionally, the energy signature, or spectrum, in X-rays of Sgr A* resembles that of jets coming from supermassive black holes in other galaxies.

Image credit: X-ray: NASA/CXC/UCLA/Z.Li et al; Radio: NRAO/VLA

Giant Elliptical Galaxy Harbors Largest Known Black Hole in Universe

The black hole at the center of the super giant elliptical galaxy M87 in the Virgo cluster fifty million light-years away is the most massive black hole for which a precise mass has been measured—6.6 billion solar masses. Orbiting the galaxy is an abnormally large population of about 12,000 globular clusters, compared to 150-200 globular clusters orbiting the Milky Way. The team theorized that the M87 black hole grew to its massive size by merging with several other black holes. M87 is the largest, most massive galaxy in the nearby universe, and is thought to have been formed by the merging of 100 or so smaller galaxies. The M87 black hole’s large size and relative proximity, astronomers think that it could be the first black hole that they could actually “see.”

In 2011, using the Frederick C. Gillett Gemini Telescope on Mauna Kea, Hawaii, a team of astronomers calculated the black hole’s mass, which is vastly larger than the black hole in the center of the Milky Way, which is about 4 million solar masses. The black hole’s event horizon, 20 billion km across “could swallow our solar system whole.”

In order to calculate the black hole’s mass, the astronomers measured how fast surrounding stars orbit the black hole. They found that, on average, the stars orbit at speeds of nearly 500 km/s (for comparison, the sun orbits the black hole at the center of the Milky Way at about 220 km/s). From these observations, the astronomers could come up with what they say is the most accurate estimate for the mass of a supermassive black hole.

Future calculations may attempt to calculate the size of another black hole with a roughly estimated mass of 18 billion solar masses, which is located in a galaxy about 3.5 billion light-years away.

In the image at the top of the page, a central jet is surrounded by nearby bright arcs and dark cavities in the multimillion degree Celsius atmosphere of M87. Much further out, at a distance of about fifty thousand light years from the galaxy’s center, faint rings can be seen and two spectacular plumes extend beyond the rings. These features, shown in X-rays, together with VLA radio observations, are dramatic evidence that repetitive outbursts from the central supermassive black hole have been affecting the entire galaxy for a hundred million years or more.

The Daily Galaxy via Chandra X-Ray Observatory