sheeny
10-08-2006, 08:04 AM
Found this in this morning's Nature Contents.
Al.
Editor's Summary
10 August 2006
Solar System minnows
Scorpius X-1 (Sco X1) has an important place in the history of astronomy as, apart from the Sun, it was the first cosmic X-ray source ever detected. It now has a new claim to fame: small but significant dips in its X-ray light curves obtained by the Rossi X-ray Timing Explorer satellite may represent the first ever observation of small (less than 100 metre diameter) trans-neptunian objects (TNOs). The irregularities occur at millisecond time scales and are almost certainly caused by occultation of tiny TNOs. Since the first discovery of a Kuiper belt object in 1992, nearly a thousand more TNOs have been found. The ones that have been seen are hundreds to several thousand kilometres in diameter but many smaller objects have been expected to exist.
News and Views: Solar System: Sifting through the debris
A quadrillion previously unnoticed small bodies beyond Neptune have been spotted as they dimmed X-rays from a distant source. Models of the dynamics of debris in the Solar System's suburbs must now be reworked.
Asantha Cooray
Letter
Nature 442, 660-663(10 August 2006) | doi:10.1038/nature04941; Received 14 February 2006; Accepted 25 May 2006
Occultation of X-rays from Scorpius X-1 by small trans-neptunian objects
Hsiang-Kuang Chang1 (http://www.nature.com/nature/journal/v442/n7103/abs/nature04941.html#a1),2 (http://www.nature.com/nature/journal/v442/n7103/abs/nature04941.html#a2), Sun-Kun King3 (http://www.nature.com/nature/journal/v442/n7103/abs/nature04941.html#a3), Jau-Shian Liang1 (http://www.nature.com/nature/journal/v442/n7103/abs/nature04941.html#a1), Ping-Shien Wu2 (http://www.nature.com/nature/journal/v442/n7103/abs/nature04941.html#a2), Lupin Chun-Che Lin1 (http://www.nature.com/nature/journal/v442/n7103/abs/nature04941.html#a1) and Jeng-Lun Chiu1 (http://www.nature.com/nature/journal/v442/n7103/abs/nature04941.html#a1)
Since the discovery1 of the trans-neptunian objects (TNOs) in 1992, nearly one thousand new members have been added to our Solar System2,3, several of which are as big as—or even larger than—Pluto4,5. The properties of the population of TNOs, such as the size distribution and the total number, are valuable information for understanding the formation of the Solar System, but direct observation is only possible for larger objects with diameters above several tens of kilometres. Smaller objects, which are expected to be more abundant, might be found when they occult background stars6,7,8,9,10, but hitherto there have been no definite detections. Here we report the discovery of such occultation events at millisecond timescales in the X-ray light curve of Scorpius X-1. The estimated sizes of these occulting TNOs are http://www.nature.com/__chars/less/special/le/black/med/base/glyph.gif100 m. Their abundance is in line with an extrapolation of the distribution2 of sizes of larger TNOs.
Al.
Editor's Summary
10 August 2006
Solar System minnows
Scorpius X-1 (Sco X1) has an important place in the history of astronomy as, apart from the Sun, it was the first cosmic X-ray source ever detected. It now has a new claim to fame: small but significant dips in its X-ray light curves obtained by the Rossi X-ray Timing Explorer satellite may represent the first ever observation of small (less than 100 metre diameter) trans-neptunian objects (TNOs). The irregularities occur at millisecond time scales and are almost certainly caused by occultation of tiny TNOs. Since the first discovery of a Kuiper belt object in 1992, nearly a thousand more TNOs have been found. The ones that have been seen are hundreds to several thousand kilometres in diameter but many smaller objects have been expected to exist.
News and Views: Solar System: Sifting through the debris
A quadrillion previously unnoticed small bodies beyond Neptune have been spotted as they dimmed X-rays from a distant source. Models of the dynamics of debris in the Solar System's suburbs must now be reworked.
Asantha Cooray
Letter
Nature 442, 660-663(10 August 2006) | doi:10.1038/nature04941; Received 14 February 2006; Accepted 25 May 2006
Occultation of X-rays from Scorpius X-1 by small trans-neptunian objects
Hsiang-Kuang Chang1 (http://www.nature.com/nature/journal/v442/n7103/abs/nature04941.html#a1),2 (http://www.nature.com/nature/journal/v442/n7103/abs/nature04941.html#a2), Sun-Kun King3 (http://www.nature.com/nature/journal/v442/n7103/abs/nature04941.html#a3), Jau-Shian Liang1 (http://www.nature.com/nature/journal/v442/n7103/abs/nature04941.html#a1), Ping-Shien Wu2 (http://www.nature.com/nature/journal/v442/n7103/abs/nature04941.html#a2), Lupin Chun-Che Lin1 (http://www.nature.com/nature/journal/v442/n7103/abs/nature04941.html#a1) and Jeng-Lun Chiu1 (http://www.nature.com/nature/journal/v442/n7103/abs/nature04941.html#a1)
Since the discovery1 of the trans-neptunian objects (TNOs) in 1992, nearly one thousand new members have been added to our Solar System2,3, several of which are as big as—or even larger than—Pluto4,5. The properties of the population of TNOs, such as the size distribution and the total number, are valuable information for understanding the formation of the Solar System, but direct observation is only possible for larger objects with diameters above several tens of kilometres. Smaller objects, which are expected to be more abundant, might be found when they occult background stars6,7,8,9,10, but hitherto there have been no definite detections. Here we report the discovery of such occultation events at millisecond timescales in the X-ray light curve of Scorpius X-1. The estimated sizes of these occulting TNOs are http://www.nature.com/__chars/less/special/le/black/med/base/glyph.gif100 m. Their abundance is in line with an extrapolation of the distribution2 of sizes of larger TNOs.