Hubble's Powers of Ten

Kenneth Sembach,

It seems like only yesterday, but Servicing Mission 4 (SM4) took place three years ago now. On the anniversary of SM4, Hubble is better than ever and operating at the peak of its capabilities. The competition for observing time is intense. The Institute received over 1000 proposals in each of the last three Cycles, which oversubscribed the available observing time by a factor of six or more. Funding for archival research is also very competitive. Meanwhile, Hubble’s scientific achievements grow in breadth and depth. Last year, targets spanned ten orders of magnitude in distance—from the Moon to a galaxy at redshift ten. Talk about depth of field!

Other “powers-of-ten” milestones in 2011 were Hubble’s 1,000,000th observation, taken on July 4, and Hubble’s 10,000th scientific paper, which was published a few months later.

The 10,000th paper, entitled “XRF 100316D/SN 2010bh and the Nature of Gamma-Ray Burst Supernovae,” by Zach Cano and collaborators, appeared in the October 10, 2011, issue of the Astrophysical Journal. It analyzes the light curve of the faintest supernova ever associated with a long-duration gamma-ray burst. Dr. Cano recently finished his doctoral studies at the Astrophysics Research Institute of John Moores University in Liverpool, England, and the paper is part of his thesis.

Cano et al. 2011 was but one of 787 scientific papers based on Hubble data published last year—averaging more than two papers per day, the highest total ever and topping the previous high of 728 papers in 2010 by more than one additional paper per week. In April 2012, Hubble’s paper tally stood at 10,385. The 11,000th paper is expected early in 2013, if not sooner.

Hubble results are a fundamental and increasingly important resource for modern astronomical investigations, as evidenced by the exponentially increasing rate of citations to these papers. In just the past two years, Hubble papers received more than 100,000 citations, corresponding to a new citation roughly once every 10 minutes. Approximately one-quarter of all citations to Hubble science have occurred since SM4.

Hubble helps launch the careers of new generations of astronomers. Each year now, more than 100 graduate students and more than 100 postdocs participate in the analysis and scientific interpretation of Hubble data. In the past five years, Hubble data have served as the basis for 175 doctorate degrees in the U.S. and Canada—an average production rate of PhDs of one per 10 days. Obviously, not all Hubble investigations lead to advanced degrees, but Hubble data and grant support form a solid foundation for the scientific vitality of our profession. Young scientists seem to have a fathomless set of ideas to test as they push the frontiers of exploration. Surely, great surprises—and even more prizes—await them.

Based on all these measures of scientific output, a case can be made that Hubble is the most productive telescope of all time (see Figure 1).