Hubble's Universe Unfiltered

  • May 10, 2013

    Will Hubble Observe the Recent Gamma-Ray Burst?

    Q: Will Hubble Observe the Recent Gamma-Ray Burst?

    On April 27, 2013, NASA's Fermi Gamma-Ray Telescope observed a gigantic outpouring of gamma-ray emission in the constellation Leo. Such gamma-ray bursts (GRBs) have been observed by satellites since the late 1960s. Since then, astronomers have painstakingly pinned down that the underlying source is generally a huge supernova explosion in a distant galaxy. A massive star, billions of light-years away, collapses its core to form a black hole and explodes its outer layers across interstellar space. GRBs are the enormously energetic birth announcement of a black hole.

    What made GRB130427A special is that it is relatively close, about 3.6 billion light-years away. Closer means brighter, and the gamma-rays observed were described as "shockingly, eye-wateringly bright." It set records for both the highest energy gamma-rays seen by Fermi as well as the longest-lasting GRB. The burst lasted for hours and remained detectable for most of a day.

    The duration of the burst allowed astronomers to trigger simultaneous observations from other telescopes in other wavelengths. GRB130427A has been detected in optical, infrared, and radio wavelengths. Astronomers will continue to monitor the burst location to measure how the explosion fades away and observe the expected supernova remnant. A supernova of this strength, located this close, provides enticing opportunities to see details not yet uncovered during other, previous stellar explosions.

    Hence, the natural question that I received is whether the Hubble Space Telescope will join in the follow-up observations.

    Hubble has been used for follow-up observations to other discoveries many times. For example, ground-based observations uncovered the solar system's most-distant known object, Sedna. But only Hubble's fine resolution could get a decent estimate of Sedna's size. When Hubble can provide important additional information, it may be tasked to observe what are called "targets of opportunity."

    Such interruptions to Hubble's schedule do have a cost. Observations are meticulously planned well in advance to maximize the scientific return of the telescope. Given Hubble's orbit around Earth and Earth's orbit around the Sun, some regions of the sky are more efficiently scheduled on a given date. Slewing the telescope to another part of the sky is slow and will impact the research of those who have waited many months for their observations. The important criteria for targets of opportunity is both scientific merit and that Hubble must have a unique capability not provided by other telescopes.

    At this time, I am told that Hubble is not scheduled to observe GRB130427A. It is not surprising to me, as the observations most needed now are repeated monitoring visits to the target and Hubble is definitely not designed for daily monitoring. Once the underlying supernova has been found, perhaps Hubble's resolution or ultraviolet light instrumentation might provide a unique capability. If so, I'm sure that some astronomer will propose for such observations.

    What the observations of GRB130427A highlight to me is the intense growth of multi-wavelength astronomy and the fluidity of international scientific cooperation in the Internet age. Within hours, quick-response telescopes had joined observations to provide complementary views in wavelengths that record distinctly different aspects of the explosive event. Round-the-clock monitoring requires round-the-world coverage, and observatories joined efforts to provide both in a collaborative campaign that will last for weeks to months. Like Hubble's orbit, science flows freely across national boundaries.