Star Formation is Coming to a Close

By Breanna Draxler | November 9, 2012 10:21 am

star formation
A composite image of a molecular cloud used as a model to determine how stars are formed.

Hot off the astronomical press: the star census is complete. An international team of astronomers has conducted the first, comprehensive survey of stellar formation in the universe. The undertaking was ten times bigger than any star formation study before it, and confirmed that the rate of star formation has slowed significantly over time. But the researchers upped the stakes with this one by finding that the universe is now almost out of star-making materials. 

Scientists used three massive telescopes for their observations, including the VLT (Very Large Telescope) in Chile, and two in Hawaii: the United Kingdom Infrared Telescope and the Subaru. Through these telescopes the scientists observed hydrogen alpha emissions. They essentially took snapshots of star-forming galaxies 4, 7, 9 and 11 billion years ago, which they assembled into a sort of panoramic history of star formation in the universe.

The researchers found that the rate of star formation in the distant, early universe was much greater than in the closer, more recently formed universe. In fact, based on the extrapolation of their results, published in the Monthly Notices of the Royal Astronomical Society, 95 percent of the universe’s stars have already been formed, half of them in a flurry between 9 and 11 billion years ago. The remaining half have come into existence more gradually since then.

If this rate of formation continues to decline, the astronomers predict that the universe will only churn out another five percent of its current star population before halting production.

Image courtesy of NASA.

CATEGORIZED UNDER: Space, Technology
  • JM

    Hi Breanna,

    the researchers didn’t look for alpha particles. They used optical facilities to observe photons, H-alpha photons.

    regards,

    JM

  • http://xtaldave.wordpress.com xtaldave

    Not an expert on such matters, but wouldn’t you suppose that the rate star formation might be a process that has peaks and troughs? When the stars that were made in the ‘flurry’ 9-11 billion years ago ‘die’ (assuming they haven’t all died already), won’t their debris & remnants form the dust clouds that give rise to the stars of the future?

  • Aaron

    I’m fairly certain that by H-alpha emission, they mean the H-alpha hydrogen emission line, which is due to electrons in excited orbitals sinking back down to a lower state. Not alpha particles, which are actually He nuclei (2 protons and 2 neutrons… which is impossible for a hydrogen atom to emit).

  • https://secure.gravatar.com/michaeljfisher Michael Fisher

    Ethan Siegel over at his blog “Starts With a BANG!” wrote a post on this where he states that far more stars will be born than have already been born:-

    QUOTE: “Every Galaxy will have New Stars for Trillions of Years! [November 7, 2012] ~ …Yes, it’s interesting that the star formation rate has declined, and it’s interesting that it’s declined at the rate we’ve observed. But it’s not going to drop to zero any time soon, and if you sum up the total number of stars in our Universe’s future, it’s actually far greater than the number of stars that have already existed up until this point in time, a far cry from the “only 5% more than we have now” figure you may have read.

    Although we might be approaching the peak of star density within our galaxy, we can very strongly say that the vast majority of stars that will ever call our galaxy home haven’t been born yet. We won’t live long enough to see them, either, as many trillions of years into the future is far too ambitious to count on, even for those of you counting on the singularity. But based on the physics and astronomy we know, there will be new stars for ages and ages to come, outnumbering even the full complement of stars that have ever existed up until today.”

  • Breanna Draxler

    @Aaron and JM, thanks for the sharp eyes! I’ve corrected my wording now.

  • amphiox

    Not an expert on such matters, but wouldn’t you suppose that the rate star formation might be a process that has peaks and troughs? When the stars that were made in the ‘flurry’ 9-11 billion years ago ‘die’ (assuming they haven’t all died already), won’t their debris & remnants form the dust clouds that give rise to the stars of the future?

    The universe is not a perpetual motion machine.

    As stars live they fuse their hydrogen into other elements. When they die some of them explode and eject their material into dust clouds that do give rise to stars in the future. However, 1) since they’ve already fused some of their hydrogen into heavier elements, the material to eject back into the universe to make new stars is not purely hydrogen, but also contains heavier elements that are useless for the purpose of making new stars, and 2) some of the substance that made up the old stars never gets ejected back into dust clouds, but instead forms inert dead stellar remnants, like white dwarfs, neutron stars, and black holes, the means that with each generation of stars, the total amount of hydrogen available in the universe to make new stars goes down.

    And once the universe runs out of accessible hydrogen in sufficient quantity and density for gravitational collapse to make new stars, star formation will stop.

  • Kudzu

    ‘If this rate of formation continues to decline, the astronomers predict that the universe will only churn out another five percent of its current star population before halting production.’

    This amused me as a closing paragraph given what the rest of the article noted. (The 95% figure.) If you had closed with a figure of six or seven percent, then I would have something to ponder.

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