Asteroid Smash-up Tells Of Rocky Road To Planet Formation

This artist’s concept shows the immediate aftermath of a large asteroid impact around NGC 2547-ID8, a 35-million-year-old sun-like star thought to be forming rocky planets. Credit: NASA/JPL-Caltech

NASA’s Spitzer Space Telescope has spotted an eruption of dust around a young star, possibly the result of a smashup between large asteroids. This type of collision can eventually lead to the formation of planets.

Small clumps of material within a disk stick together to form larger clumps. Eventually these clumps grow to become planets. Credit: NASA

Planets form by dribs and drabs within dusty disks around newly-forming stars. Dust sticks to dust to form small clumps. The clumps grow bigger as they which sweep up more material within the cloud until they’re boulder-sized. Gravity now works its wonders, drawing smaller bits of debris to larger until asteroids (also called planetesimals), the seeds of the planets form.

Many asteroids break apart when they collide, but others continue to grow by accumulation until they’ve collected enough stuff to collapse through self-gravity to form a sphere. After 100 million years of bone-crushing impacts, a planet is born!

Astronomers had been regularly observing the star NGC 2547-ID8 located 1,200 light years away in the constellation Vela the Sails with the Spitzer telescope, which can see into the infrared, a color of light just beyond the red end of the rainbow spectrum. We sense infrared as heat, but Spitzer sees it as glowing radiation.

Dust warmed by starlight radiates brightly in the infrared. Previous observations of NGC 2547-ID8 had already shown variations in the amount of dust around the star, hinting at possible asteroid collisions. But astronomers couldn’t believe their eyes when they compared photos made in August 2012 and five months later in January 2013.

The bright summer star Vega – 25 light years from Earth – photographed by the Spitzer Space Telescope shows a huge disk of glowing dust extending at least 76 billion miles from the star. Like NGC 2547-ID8, Vega is a young star that appears to be forming planets much like the sun 4.6 billion years ago. Credit: NASA

“We not only witnessed what appears to be the wreckage of a huge smashup, but have been able to track how it is changing – the signal is fading as the cloud destroys itself by grinding its grains down so they escape from the star,” said Kate Su of the University of Arizona and co-author on the study.

Now a large, thick cloud of dust orbits the star which the team of astronomers is keeping their eye on in hopes of spotting more collisions.

Astronomers were surprised to see these data from NASA’s Spitzer Space Telescope in January 2013, showing a huge eruption of dust around a star called NGC 2547-ID8. In this plot, infrared brightness is shown on the vertical axis and time along the bottom. Credit: NASA/JPL-Caltech/University of Arizona

“We are watching rocky planet formation happen right in front of us,” said George Rieke, a University of Arizona co-author of the new study. Although no one was around to watch out solar system’s planets form, Spitzer offers a glimpse into those lost times through its study of young, dust-cloaked stars in the present.


3 Responses

  1. Edward M. Boll

    Ophiuchus is supposed to be brighter than magnitude 7 now. I suppose that we have a few more days to see it.

      1. astrobob

        Hi Edward,
        I don’t think it’s that bright. I saw it 6 mornings ago at mag. ~8.5-9. Other more recent estimates have placed it around 8-8.5.

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