Why do you think this paper is highly cited?

The paper is probably highly cited for a few reasons:

• The paper is in a currently very hot, and scientifically exciting area of extra-solar planet detection.
• The results of not finding any planets in the globular cluster 47 Tuc are surprising, but also amenable to ready explanation by theorists.
• The new results provide a fundamental new "data point" in understanding planet formation and survival in diverse stellar systems.

  Does it describe a new discovery or methodology that's useful to others?

The paper does describe a new result (although in this case it was actually a null result in that no planets were found, and this was quite significant). The paper also presents a new methodology (searching for extrasolar planet transits using a space-based telescope) that is useful to others

  Is it a condensation of previous literature on the subject?

The paper is not a condensation of previous literature; it is rather unique.

  Could you summarize the significance of your paper in layman's terms?

In layman's terms, recent searches for planets about stars in the local solar neighborhood have shown that about 1% of stars have gas giant planets very close to the host star with orbital periods of only 3-5 days. Being so close to the host star there is a significant, 10% chance that any orbiting planet will pass between us and the host star, thus creating an occultation of light (transit). Transits can be seen as periodic dips in the stars light intensity of a few percent, and many thousands of stars can be monitored simultaneously. Globular clusters are groups of about one million stars, and are some of the oldest stars in the galaxy. We currently are only starting to understand where planets do and do not exist, searching in a globular cluster which has different chemical composition than local stars is both observationally convenient in that many stars can be observed at one time, and also scientifically interesting in that a new regime of conditions can be probed. If planets were as common in the globular cluster 47 Tucanae as locally then we expected to find about 20, seeing none we concluded that the different chemical composition of the stars or their crowding probably severely hampers the creation or survival of planets.

Ron Gilliland
Space Telescope Science Institute
Baltimore, MD