'Early-warning system’ for dying stars 8 September 2013

'Early-warning system’ for dying stars

  •   Israeli finds ‘early-warning system’ for dying stars
    Forty days before a star burns out as a supernova, it releases a gigantic amount of mass. This data could be useful for many purposes.
  • Dr. Eran Ofer from the Weizmann Institute (pictured here with his daughter) has helped detect an early-warning blast before stars go supernova
    By Rivka Borochov
    Meteorite fragments that caused injuries and panic in the former Soviet Union in February alerted international governments to the importance of interstellar warning systems to help avert the next catastrophe.
    Now new research from Israel exposes and partially explains a previously unknown phenomenon in the universe that could have people in the future packing up and moving to another solar system before our sun explodes into a supernova – a dying star that brightens as it ejects most of its mass.
    Led by Eran Ofek of the Weizmann Institute of Science, the Israeli researchers discovered that before stars get to the supernova stage, they undergo a “mini-explosion,” tossing out a chunk of their mass into outer space. Never before have scientists tracked this mini-explosion down to weeks before a star dies.
    Considered the most powerful explosions in the universe, star burnouts happen for two reasons: the star runs out of fuel suddenly, or consumes too much mass from a nearby star. Up until now, astrophysicists were able to “see” and record these rare events in the cosmos, but were not able to predict in advance when these powerful explosions would happen.
    For scientists, this new research provides insight into the end of stars’ lives and suggests a new early-warning alert system could be in place to detect when a star will die - about 40 days before it goes supernova.
    In the study, Ofek and an international team looked at four supernovas and then pored over retroactive data to find a link to a previous event. Their analysis found that a small outburst could be detected 40 days before the star fatally exploded.
    Star models
    “There are several reasons for this, but such events are pretty rare,” says Ofek. “We didn’t see many events in the past where there is an outburst before the explosion. Maybe there are two other cases like that, but another unique fact in the outburst here is the time difference between the outburst and the supernova: only about one month. It may tell us that there is a deep connection between an outburst and explosion.”

    He explains that massive stars live for 100 million years and the probability of having two unrelated explosions 40 days apart is strikingly low.

    his model may be used in the future to predict fairly accurately when a star will explode. For now, it is of interest to stargazers and astrophysicists, but in the future knowing when a star explodes could open the door to new realms of possibilities -- for renewable energy, for instance.
    That’s because the “small” preliminary explosion amounts to a huge energy “leak” resulting from a buildup of radiation inside the star.
    According to data Ofek and his team described in the February issue of Nature, some 40 days before the final explosion, a star they were observing released as much matter as 3,330 Earths, or one percent of the sun. The energy was traveling at 7.2 million km/h.
    Yet there are no textbooks that can describe this new phenomenon, and in the scheme of things it may not be earth-shattering. “It’s big, but it’s not monumental,” says Ofek. “This whole subject is pretty new and we don’t understand it very well. And it’s too early to say what will come from it.
    First we want to understand the physical mechanism [of the mini-explosion], and continue to speculate about a possible mechanism,” he adds.
    Ofek is a member of the Weizmann’s particle physics and astrophysics department and of the Palomar Transient Factory project based at the California Institute of Technology. This project scans the skies for supernovas using telescopes at the Palomar Observatory in California. A team from Israel, the US and the UK participated in this latest research.