Posted on by Matt Williams

One of the Milky Way’s Arms Might Encircle the Entire Galaxy

Artist's conception of the Milky Way galaxy as seen from far Galactic North (in Coma Berenices) Credit: NASA/JPL-Caltech/R. Hurt

Given that our Solar System sits inside the Milky Way Galaxy, getting a clear picture of what it looks like as a whole can be quite tricky. In fact, it was not until 1852 that astronomer Stephen Alexander first postulated that the galaxy was spiral in shape. And since that time, numerous discoveries have come along that have altered how we picture it.

For decades astronomers have thought the Milky Way consists of four arms — made up of stars and clouds of star-forming gas — that extend outwards in a spiral fashion. Then in 2008, data from the Spitzer Space Telescope seemed to indicate that our Milky Way has just two arms, but a larger central bar. But now, according to a team of astronomers from China, one of our galaxy’s arms may stretch farther than previously thought, reaching all the way around the galaxy.

This arm is known as Scutum–Centaurus, which emanates from one end of the Milky Way bar, passes between us and Galactic Center, and extends to the other side of the galaxy. For many decades, it was believed that was where this arm terminated.

However, back in 2011, astronomers Thomas Dame and Patrick Thaddeus from the Harvard–Smithsonian Center for Astrophysics spotted what appeared to be an extension of this arm on the other side of the galaxy.

Star-forming region in interstellar space. Image credit: NASA, ESA and the Hubble Heritage (STScI/AURA)-ESA/Hubble Collaboration
Star-forming region in interstellar space. Image credit: NASA, ESA and the Hubble Heritage (STScI/AURA)-ESA/Hubble Collaboration

But according to astronomer Yan Sun and colleagues from the Purple Mountain Observatory in Nanjing, China, the Scutum–Centaurus Arm may extend even farther than that. Using a novel approach to study gas clouds located between 46,000 to 67,000 light-years beyond the center of our galaxy, they detected 48 new clouds of interstellar gas, as well as 24 previously-observed ones.

For the sake of their study, Sun and his colleagues relied on radio telescope data provided by the Milky Way Imaging Scroll Painting project, which scans interstellar dust clouds for radio waves emitted by carbon monoxide gas. Next to hydrogen, this gas is the most abundant element to be found in interstellar space – but is easier for radio telescopes to detect.

Combining this information with data obtained by the Canadian Galactic Plane Survey (which looks for hydrogen gas), they concluded that these 72 clouds line up along a spiral-arm segment that is 30,000 light-years in length. What’s more, they claim in their report that: “The new arm appears to be the extension of the distant arm recently discovered by Dame & Thaddeus (2011) as well as the Scutum-Centaurus Arm into the outer second quadrant.”

Ilustration of our galaxy, showing our Sun (red dot) and the possible extension of the Scutum-Centaurus Arm. CREDIT: Modified from "A Possible Extension of the Scutum-Centaurus Arm into the Outer Second Quadrant" by Yan Sun et al., in The Astrophysical Journal Letters, Vol. 798, January 2015; Robert Hurt. NASA/JPL-Caltech/SSC (background spiral).
Illustration of our galaxy showing the possible extension of the Scutum-Centaurus Arm. CREDIT: Yan Sun/The Astrophysical Journal Letters, Vol. 798/Robert Hurt. NASA/JPL-Caltech/SSC

This would mean the arm is not only the single largest in our galaxy, but is also the only one to effectively reach 360° around the Milky Way. Such a find would be unprecedented given the fact that nothing of the sort has been observed with other spiral galaxies in our local universe.

Thomas Dame, one of the astronomers who discovered the possible extension of the Scutum-Centaurus Arm in 2011, was quoted by Scientific American as saying: “It’s rare. I bet that you would have to look through dozens of face-on spiral galaxy images to find one where you could convince yourself you could track one arm 360 degrees around.”

Naturally, the prospect presents some problems. For one, there is an apparent gap between the segment that Dame and Thaddeus discovered in 2011 and the start of the one discovered by the Chinese team –  a 40,000 light-year gap to be exact. This could mean that the clouds that Sun and his colleagues discovered may not be part of the Scutum-Centaurus Arm after all, but an entirely new spiral-arm segment.

If this is true, than it would mean that our Galaxy has several “outer” arm segments. On the other hand, additional research may close that gap (so to speak) and prove that the Milky Way is as beautiful when seen afar as any of the spirals we often observe from the comfort of our own Solar System.

Further Reading: arXiv Astrophysics, The Astrophysical Letters

Posted on by Elizabeth Howell

Future Games: Astronauts Tele-Operate An Earth-Bound Rover … From Space!

The K10 Black planetary rover during a Surface Telerobotics Operational Readiness Test at NASA's Ames Research Center. Credit: NASA/Dominic Hart

Astronauts, start your rover engines. Two astronauts recently remote-controlled a rover vehicle in California from their perch on the International Space Station — about 250 miles (400 kilometers) overhead.

The concept is cool in itself, but NASA has loftier aims. It’s thinking about those moon and asteroid and Mars human missions that the agency would really like to conduct one day, if it receives the money and authorization.

Potentially, say, you could have a Mars crew using rovers to explore as much of the surface as possible in a limited time.

Mars Curiosity and its predecessor rovers have found amazing things on Mars, but the challenge is the average 20-minute delay in communications between Mars and Earth. NASA deftly accounts for this problem through techniques such as hazard avoidance software so that Curiosity, say, wouldn’t crash into a big Martian boulder. (More techniques from NASA at this link.) But having astronauts above the surface would cut down on the time delay and potentially change Mars rover driving forever.

Luca Parmitano controlled the K-10 rover from space on July 26, 2013. Credit: NASA Television (screencap)
Luca Parmitano controlled the K10 rover from space on July 26, 2013. Credit: NASA Television (screencap)

So about that test: two astronauts so far have run the K10 planetary vehicle prototype around a “Roverscape” at NASA’s Ames Research Center in California. NASA calls these runs the “first fully-interactive remote operation of a planetary rover by an astronaut in space.”

Expedition 36’s Chris Cassidy was first up on June 15, spending three hours moving the machine around in the rock-strewn area, which is about the size of two football fields. Then his crewmate Luca Parmitano took a turn on July 26, going so far as to deploy a simulated radio antenna. Another test session should take place in August.

“Whereas it is common practice in undersea exploration to use a joystick and have direct control of remote submarines, the K10 robots are more intelligent,” stated Terry Fong, human exploration telerobotics project manager at Ames.

“Astronauts interact with the robots at a higher level, telling them where to go, and then the robot itself independently and intelligently figures out how to safely get there,” added Fong, who is also director of Ames’ intelligent robotics group.

The tests simulated a mission to the moon’s L2 Lagrangian point, a spot where the combined gravity of the moon and Earth allow a spacecraft to remain virtually steady above the surface. One possibility for such a mission would be to deploy a radio telescope on the lunar side opposite from Earth, far from Earth’s radio noise, NASA said.

These tests also showcase a couple of technical firsts:

  • NASA is testing a Robot Application Programming Interface Delegate (RAPID) robot data messaging system to control the robot from space, essentially working to strip down the information to the bare essentials to make communication as easy as possible. (RAPID has been tested before, but never in this way.)
  • The agency is also using its Ensemble software in space for telerobotics for the first time. It describes this as “open architecture for the development, integration and deployment of mission operations software.”

Source: NASA

Posted on by Bob King

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

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. Image courtesy of NRAO/AUI and NRAO

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.

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
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

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?

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
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

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.

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.
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.

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).

If our eyes could see radio light, this is what the sky would look like. What appear to be stars are distant galaxies. The wispy arcs and shells are the remnants of exploding supernovae.
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

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.

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

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.

Posted on by Jean Tate

Arecibo Observatory

courtesy of the NAIC - Arecibo Observatory, a facility of the NSF

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Named after the nearby city in Puerto Rico, the Arecibo Observatory (or Arecibo Radio Telescope) is the largest single-aperture (radio) telescope ever built, 305 m in diameter.

Taking advantage of a karst sinkhole, Cornell University built a spherical reflector out of wire mesh, with receivers at the focus suspended by 18 steel cables strung from three concrete towers on the rim. It took three years to build, and was completed in 1963. Since then it has been upgraded several times; for example, in 1974 perforated aluminum panels replaced the wire mesh, and a Gregorian reflector system added to the receiver mechanism in 1997. Among other things, these upgrades have extended the range of radio wavelengths Arecibo can operate at, both as a radio telescope and for radar astronomy.

Such a visually interesting piece of scientific hi-tech has lead to Arecibo playing a role in many movies and TV shows, from James Bond’s Golden Eye to Contact to X-Files.

Everyone knows about SETI@Home, right? Well, it’s receivers on Arecibo that supply the data which the millions of PCs crunch!

Arecibo has played a key role in many astronomical discoveries, from the rotation period of Mercury (a radar astronomy application, in 1964), to the pulses of the Crab Nebula (1968), to studies of pulsars by Hulse and Taylor (1974) that lead to their Nobel Prize (1993), and to direct imaging of asteroids (another radar astronomy application, first done in 1989).

Due to budget cutbacks and changes in research priorities, the future of Arecibo is uncertain (most of its funding comes from the National Science Foundation); maybe you can find a way to save it?

Here’s the official Arecibo Observatory website; ALFA is a current large-scale astronomical survey being done at Arecibo, in case you don’t already know about SETI@Home, and click here to read more about planetary radar.

Calling All Amateur Astronomers: Help Comb Through Arecibo Data for Gems, Arecibo Spots Triple Asteroid, Arecibo Gets an Upgrade: just three of the many Universe Today stories featuring the Arecibo Observatory!

Some of the ways Arecibo contributes to astronomy are covered in Astronomy Casts The Rise of Supertelescopes, and Across the Electromagnetic Spectrum.

Source: National Astronomy and Ionosphere Center: Arecibo Observatory

Posted on by Fraser Cain

What are Telescopes?

This artist’s rendering shows the Extremely Large Telescope in operation on Cerro Armazones in northern Chile. The telescope is shown using lasers to create artificial stars high in the atmosphere. Image: ESO/E-ELT
This artist’s rendering shows the Extremely Large Telescope in operation on Cerro Armazones in northern Chile. The telescope is shown using lasers to create artificial stars high in the atmosphere. Image: ESO/E-ELT

Early theories of the Universe were limited by the lack of telescopes. Many of modern astronomy’s findings would never have been made if it weren’t for Galileo Galilei’s discovery. Pirates and sea captains carried some of the first telescopes: they were simple spyglasses that only magnified your vision about four times and had a very narrow field of view. Today’s telescopes are huge arrays that can view entire quadrants of space. Galileo could never have imagined what he had set into motion.

Here are a few facts about telescopes and below that is a set of links to a plethora of information about them here on Universe Today.

Galileo’s first telescopes were simple arrangements of glass lenses that only magnified to a power of eight, but in less than two years he had improved his invention to 30 power telescope that allowed him to view Jupiter. His discovery is the basis for the modern refractor telescope.

There are two basic types of optical telescopes; reflector and refractor. Both magnify distant light, but in different ways. There is a link below that describes exactly how they differ.

Modern astronomer’s have a wide array of telescopes to make use of. There are optical observation decks all around the world. In addition to those there are radio telescopes, space telescopes, and on and on. Each has a specific purpose within astronomy. Everything you need to know about telescopes is contained in the links below, including how to build your own simple telescope.