Supernova Alerts

Supernovae and other short-lived, unpredictable cosmic events pose a challenge astronomers. They want to collect data during the earliest phases of the exposure, but critical hours or days may pass before anyone notices the event. The astronomy community has several alert systems that spread the word so professional and amateur astronomers alike can observe the stellar explosions.

Harvard University runs the International Astronomical Union’s Central Bureau for Astronomical Telegrams. It collects reports of novae and supernovae as well as new objects in the Solar System like moons, comets, and “unusual minor planets”. They don’t report everything, however. Novae events within the Milky Way and its satellite galaxies get reported while the dozens of novae in our neighboring Andromeda Galaxy don’t. The Central Bureau reports most supernova events, but they won’t report the faintest explosions. IAU Circulars are printed and mailed on postcards to subscribers. Most astronomers subscribe to the emailed Central Bureau Electronic Telegrams. The Central Bureau charges for both subscriptions while listing the most recent novae in the Milky Way and recent supernovae on its website

Several digital-first alert systems provide a broader range of services than the Central Bureau. Astronomers at Kyoto University in Japan created the Variable Star Network mailing lists in 1995. Although its associated website doesn’t receive much attention, the mailing lists and archives are active projects. An arXiv preprint the VSNet team prepared has a good overview of the history of transient notifications as well as a comprehensive history of the VSNet and its contributions. Scientists at the University of California, Berkeley, created the Astronomer’s Telegram in 1998 to address some of the weaknesses of the traditional circular-based approach. The Astronomer’s Telegram automatically broadcasts a report on any astronomical event via email or RSS within seconds rather than incur cost and time penalties of editing submissions. For full details you can read their peer-reviewed paper or their arXiv preprint. CalTech scientists in 2009 used new virtual observatory tools to create the SkyAlert system which consolidates virtual observatory feeds into a central notification system. As described in their arXiv preprint, the SkyAlert system is itself a virtual observatory tool. Astronomers can code triggers into their observatories’ algorithms to automatically switch to a new supernova’s location when it receives a new SkyAlert.

Most of the notifications come from the professional sky surveys that dominate supernova detections. Although Ohio State University’s All-Sky Automated Survey for Supernovae lists recently-discovered supernovae on their website, the project issues reports via Astronomer’s Telegram and Twitter. The Catalina Real Time Survey searches for supernovae in data collected by an asteroid-focused sky survey. They use a virtual observatory tool to feed services like Sky Alert. Future survey projects like Europe’s Gaia space telescope mission and the United States’ Large Synoptic Survey Telescope will increase the rate of supernova discoveries. The LSST created the Transient Events iPhone app to relay its discoveries along with noticed from the SkyAlert service. The Gaia mission will issue its own Gaia Science Alerts to anyone who subscribes. The Faulkes Telescope Project, for example, will send the alerts to British schools whose students will conduct follow-up observations for the Gaia science team.

Amateur astronomer David Bishop chairs the Rochester Academy of Science’s Astronomy Section. He consolidates many of the circular and professional lists in the section’s Bright Supernova website and maintains the supernova chat group at Yahoo.

Until astrophysicists figure out how to predict a supernova, astronomers will always chase after each new event. Some supernovae give an early warning that we can detect on Earth. As a supergiant star’s core collapses, a wave of neutrinos rush away from the dying star ahead of the explosion itself. When neutrino observatories buried in deep caves or beneath Antarctic glaciers see a sudden spike in detections, the Super Nova Early Warning System alerts the world’s astronomers. Of course, nothing’s perfect. Only some supernovae generate neutrinos. Even then the explosion can’t be too far away (in galactic terms) or else too few neutrons will arrive at Earth. On top of that, the neutrino observatories low resolution only identify the general region where the supernova is appearing. Most professional observatories need much more precise information since their telescopes aren’t designed to scan the night sky. Amateur astronomers, with their relatively wide field telescopes, don’t have that problem. Sky & Telescope magazine created the AstroAlert system to connect the two communities. AstroAlert relays the neutrino observatories’ Snews reports to amateur astronomers and then relays the amateurs’ observations to the professional community.