A long, long time ago, massive, super-bright galaxies known as starburst galaxies were churning out new stars at a frantic pace. Astronomers would like to study their frenetic star-formation physics and compare them to the relatively slow star factories of the modern era, but this is very hard to do. Starburst galaxies are shrouded from our best visible-light telescopes, hiding as they are behind thick curtains of dust. Enter the Atacama Large Millimeter/submillimeter Array.
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The ALMA telescope can see them by looking directly at the dust itself. To ALMA, the starburst galaxies are some of the brightest objects in the sky.
As construction on ALMA has progressed, astronomers have been making a few observations with a few sets of radio-dish pairs, including this latest observation, which was published last week in Nature. Click through our gallery to see a few other ALMA early highlights.
For the starburst galaxy observations, an international team of astronomers used ALMA and the South Pole Telescope, and found they’re even farther away from us than expected. Two of them are the most distant galaxies of their kind that have ever been seen. This means the light that left these galaxies departed when the universe was in its infancy, around 1 billion years old. This is interesting because the galaxies are at least a billion years older than originally thought.
What’s more, ALMA–which is so sensitive it can detect individual molecular signatures–found water in these distant stellar nurseries. The molecules are the most distant observations of water ever made.
Gravitational Lensing As Seen With ALMA
This schematic image represents how light from a distant galaxy is distorted by the gravitational effects of a nearer foreground galaxy, which acts like a lens and makes the distant source appear distorted, but brighter, forming characteristic rings of light, known as Einstein rings.
One more crazy thing: Astronomers were able to do this in a few _minutes_–observations like these used to take multiple nights. Speed and accuracy are among the many promises of ALMA, the world’s largest ground-based astronomy project.
“We commission as we go, and we’ve tested as we’ve gone along,” explained Phil Jewell, deputy director of the National Radio Astronomy Observatory, an ALMA partner. “We’d like to get the science out…ALMA is such a huge step forward.”
ALMA is an aperture synthesis telescope, which uses pairs of radio antennas looking at the same objects to create a telescope with a huge angular resolution. Each radio dish, eventually 66 in all, forms a pair with every other dish, and their observations are all combined using ALMA’s special supercomputer.
Astronomers celebrated its official inauguration last week in the high, dry desert of Chile, where nearly all the array’s radio dishes are installed and ready to go. I was there with a delegation sponsored by the National Science Foundation and National Radio Astronomy Observatory, and there’s a lot more to share… so stay tuned.
This image combines data from ALMA and the Hubble Space Telescope. Shown in red is a distant, background galaxy, being distorted by the gravitational lens effect produced by the galaxy in the foreground. That galaxy is shown in blue and was measured by Hubble. The background galaxy appears warped into a so-called Einstein ring: a circle of light around the foreground galaxy. Astronomers first spotted signs of the distant galaxies with the South Pole Telescope, and then used ALMA to zoom in on them in greater detail. They were surprised to find that many of these galaxies were farther away than expected.
A Starry Spiral Surprise
This unexpected spiral is surrounding an asymptotic giant branch star, which the sun will become when it is very old. These dying red giants spew gas and dust as they reach the end of their lives, and sometimes their remnants encircle them in shrouds of dust. But this observation marked the first time anyone saw a strange spiral around such a star. Astronomers using the ALMA telescope believe it was caused by a hidden companion orbiting the dying red giant. In the future, observations with ALMA will help scientists understand how dying stars’ remains are spewed into the universe, seeding it with the elements that eventually made their way to our solar system and to us.
How Does Your Solar System Grow?
Observations made with the Atacama Large Millimeter/submillimeter Array (ALMA) telescope show a disk of gas and cosmic dust around the young star HD 142527. This helps shed light on a strange process–how exactly do baby stars continue growing while also gestating solar systems? Young stars gobble up dust and gas as they form, while some remaining material spins into a flat, rotating disk around them. Planets form in that disk, so baby star systems often appear as a dot in the middle, surrounded by a dark gap and then a dusty belt. But somehow, as this process unfolds, the stars continue to grow too. ALMA observations show this can happen thanks to a bridge between the star and its disk, which allows the two to share material. Streamers connect the disk to the star like spokes on a wheel. The outer disk is roughly two light-days across. If this were our own Solar System, the Voyager 1 probe — the most distant manmade object from Earth — would be at approximately the inner edge of the outer disk.
A Sweet Solar System Ingredient
ALMA is powerful in part because it can detect the signatures of individual molecules in deep space. These can help astronomers trace the presence of gas, and they can even be used to detect which way a given galaxy or cloud of dust is rotating, which will help astronomers see the births of stars. But sometimes molecules are fun to look at for their own sake, and for the questions they raise–like, for example, ALMA’s detection of glycolaldehyde. This is the simple possible sugar, but it’s important because it’s a key ingredient in the production of RNA. ALMA spotted it in the gas around a star called IRAS 16293-2422. This young binary star has roughly the same mass as our sun. By looking at the way its super-faint light is warped by the distance between the sugar and us, astronomers were able to tell which way it is moving, and they determined it is falling in toward one of the stars in the binary system. That means it’s in the right place and moving in the right direction for it to perhaps end up on a future forming planet. The star system is about 400 light years away in the constellation Ophiuchus. This image shows the Rho Ophiuchi star-forming region in infrared light, as seen by NASA’s Wide-field Infrared Explorer (WISE). IRAS 16293-2422 is the red object in the center of the small square. The inset image is an artist’s impression of glycolaldehyde molecules, showing its structure (C2H4O2).
Seeing Through Centaurus A’s Swirling Gas Clouds
The noisy galaxy known as Centaurus A hosts a deadly supermassive black hole at its heart, but it is also a center of creation, hosting a stellar nursery that may shed light on how the galaxy formed. Astronomers think it probably is the result of a collision between a huge elliptical galaxy and a smaller spiral galaxy. In one of ALMA’s early observations, astronomers were able to detect the position and motion of Cen A’s gas clouds, showing it swirling around the galactic center. The image here combines information from ALMA’s millimeter-wavelength viewing power, as well as near-infrared wavelength light. ALMA’s observations, shown in a range of green, yellow and orange colors, are the result of the Doppler effect as the gas moves toward or away from us. These are the sharpest and most sensitive such observations ever made.
ALMA First Light
Fittingly for a telescope made up of 66 individual radio dishes, ALMA’s first images captured the Antennae Galaxies, a pair of colliding galaxies replete with stars and stellar nurseries. The observatory’s 39- and 23-foot antennae were able to resolve areas of dense, cold gas that other telescopes could not detect. This image combines data from the Hubble Space Telescope and the ALMA network. ALMA’s observations are in the bright oranges, dark reds and electric purples you can see overlaid on Hubble’s bluish visible-light view. ALMA observes light at millimeter and sub-millimeter wavelengths, allowing observations of the farthest and oldest phenomena in the observable universe.