First light for ALMA

By Phil Plait | October 3, 2011 6:00 am

After a decade of painstaking engineering and construction, the Atacama Large Millimeter/submillimeter Array (ALMA) is now open for business.

ALMA is a collection of (currently) 19 telescopes, each 12 meters across, that can detect light that is between the radio and infrared parts of the spectrum. All sorts of interesting objects emit this kind of light, including solar systems in the process of forming, very distant galaxies nearly at the very edge of the visible Universe, and warm gas and dust from star birth.

In fact, ALMA released an image of that latter type of thing, and it’s pretty nifty:

That’s a close up of the Antennae Galaxies, one of my favorite objects in the whole sky. This is what used to be two separate spiral galaxies like our Milky Way. A few hundred million years ago they collided, and are still in the process of merging. As they do so, vast clouds of gas slam into each other, collapse, and form stars. We get a pretty good view using visible light, but ALMA can penetrate the thick dust and see what’s going on inside those clouds, and does so in detail and resolution we literally could not get in the past. In that image, blue is visible light from Hubble, and orange and yellow is from ALMA, showing where stars are currently being born.

Observations like this allow astronomers to get more information from these complex sites of star formation. We understand quite a bit about how stars are born, but the details are incredibly difficult to disentangle because so many processes are going on. When we look at objects at different wavelengths we see different physics going on (for example, ultraviolet light can come from very hot stars, while submillimeter light is generated by warm dust), so, when coupled with high-resolution Hubble images like this one inset here, these different physical processes can be teased apart.

And this view will only get better. Right now, 19 dishes are in operation for ALMA, but that will increase to 66 by 2013, spread out over the 5000-meter-high (16,500 foot) plains in northern Chile. When completed it will be able to see even deeper and with more resolution. I think I’m most excited about the prospect of observing young planetary systems. I did some work on those back in my Hubble days, and it’s amazing how much progress has been made in this very young field of astronomy. ALMA will see these systems in the millimeter regime more clearly than any telescope before, and no doubt will be a boon to scientists trying to figure out just how swirling disks of gas and dust turn into planets like Earth.

My congratulations to all my friends at the National Radio Astronomy Observatory and to everyone involved in this project! It’s always great news when we get new eyes on the sky.

Image credits: (NRAO/AUI/NSF), ALMA (ESO/NAOJ/NRAO), HST (NASA, ESA, and B. Whitmore (STScI)); Davide de Martin, NASA; W. Garnier, ALMA (ESO/NAOJ/NRAO)

Related posts:

- Awesome Antennae!
- Least massive protoplanetary disk found
- The belch of a gassy galaxy

CATEGORIZED UNDER: Astronomy, Pretty pictures
MORE ABOUT: ALMA, Antenna galaxies

Comments (16)

  1. Wzrd1

    What is the resolution of ALMA?

  2. So my daughter is taking Spanish, and as a motivator to do well, I promised that we’ll go to a Spanish speaking country sometime in the future. The more I think about it, Chile is moving up on my list of places. ;)

  3. Mel Holloway

    Are the ALMA units mobile like the Very Large Array?

  4. So .. we get two Monday galaxies for the price of one *and* a new telescope seeing first light (first heat / radio?) to start the week off?

    Superluminous. :-)

    The ALMA Antennae image there looks like a new palm or fern frond unfurling – or an octopi tentacle and yellow eye with hints of a question mark in the shape as well.

  5. Nigel Depledge

    Mel Holloway (3) said:

    Are the ALMA units mobile like the Very Large Array?

    IIUC, no. But they are trucked into position (well, IIRC, they have a custom-built monster machine to carry each telescope into position, because the “factory” where they are being built is way down at about 4000 m ASL (!)).

  6. Wzrd1

    @Nigel, #5, they move the dishes assembled? We used to have our Earth stations delivered in sections, assembling the mast and dish on site. Still a lot of metal to move, not to mention the pad for the base, but less risk of damage.

  7. @ 5. Nigel Depledge :

    …they are trucked into position (well, IIRC, they have a custom-built monster machine to carry each telescope into position, because the “factory” where they are being built is way down at about 4000 m ASL (!)).

    If folks are interested, this monster machine and procedure is shown on a BBC World news article as part of their interesting report on this. (Click on my name for article link. Last embedded video – scroll down for it.)

  8. Regner Trampedach

    Mel Holloway @ 3: No, they are not mobile. You can see some empty pads in that picture, ready to recieve the next dishes – there is nothing mobile about them. With so many dishes, there is no need for mobility. The locations are optimized for fairly uniform and high resolution over the field of view. And remember: in order to do interferometry you neeed to be able to know and control the distance between telescopes to a fraction of the wavelength of the “light” used. For radio (10cm – 10m) it is fairly easy to operate with very long baselines. With the millimeter and sub-millimeter waves observed by ALMA, baselines will be at least a 100 times shorter.
    Cheers, Regner

  9. Marshall Perrin

    The above posters stating that the antennae are not mobile are incorrect. ALMA will indeed operate in multiple array configurations, ranging from 160 meters to 16 kilometers diameter. See or . Currently only two fairly small arrays are yet supported, with max baselines of 125 and 400 m. See

    Yes, there are fixed pads permanently installed in the ground. But there are many more of those than there are antennae, even once the full array is populated. So the transporter trucks will be used to pick up and move antennae between pads on a regular, scheduled basis as part of the array operations each semester.

  10. Pete Jackson

    @1Wzrd1: The resolution and frequencies of ALMA can be found at:

    So the extended array will have sub arcsecond resolution.

    To me the real excitement from the array will be in the cosmological arena, to tackle the high redshift problems from the other end At redshifts approaching 10, light emitted initially in the ultraviolet gets redshifted beyond even Hubble’s reach. But ALMA may be able to see, at its highest frequencies, what was going on in visible light as the first stars formed!

  11. Alan(UK)

    First light for radioastron too:

    ALMA is big – this is out of this world!

  12. Pete Jackson

    @11Alan: At 5000 meters altitude, ALMA is 5% of the way into space (defined as 100 km altitude).

  13. Wzrd1

    @Pete Jackson #10, thanks! sub arcsecond is REAL good! That was what I was thinking, the high redshifted first light. :)

  14. Nigel Depledge

    @ Wzrd1 (6) -
    Well, this has kinda been answered already.

    Yes, they do transport them fully assembled. It is a monster machine that does this. I recommend following MTU’s link (#7) to see this.

    The pads on which the ‘scopes sit are fixed in place (as Regner Trampedach points out in #8) so the ‘scopes are not mobile in the same way that the elements of the VLA are. But, as Marshall Perrin (#9) points out, the ‘scopes can be moved from one pad to another. Until reading that comment, I was not aware that they deliberately built more pads than they will build ‘scopes.

    I was previously under the impression that they could move the ‘scopes around as required while they were still building them, but that once they had built all of them they would not need to. It now appears that I was wrong.


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