WEBVTT FILE 1 00:00:00.010 --> 00:00:04.060 [Music] 2 00:00:04.080 --> 00:00:08.170 [Music] 3 00:00:08.190 --> 00:00:12.210 I'm Aki Roberge, 4 00:00:12.230 --> 00:00:16.250 an astronomer at NASA's Goddard Space Flight Center. I've been studying 5 00:00:16.270 --> 00:00:20.340 a young nearby planetary system around the bright star Beta Pictoris. 6 00:00:20.360 --> 00:00:24.350 Located 63 light-years away, and only about 7 00:00:24.370 --> 00:00:28.380 20 million years old. the star is surrounded by a vast disk of 8 00:00:28.400 --> 00:00:32.450 gas, dust and comet-like bodies that we view edgewise. 9 00:00:32.470 --> 00:00:36.470 We know of one planet in there too, it's a giant planet tracking along 10 00:00:36.490 --> 00:00:40.520 an orbit nearly as large as Saturn's. I'm part of a team 11 00:00:40.540 --> 00:00:44.570 studying Beta Pic's disk using the ALMA observatory in Chile. 12 00:00:44.590 --> 00:00:48.640 We've found something odd: a belt of carbon monoxide 13 00:00:48.660 --> 00:00:52.660 gas centered about three times farther from the star than Neptune's 14 00:00:52.680 --> 00:00:56.690 distance from the sun. The total amount of gas is about 15 00:00:56.710 --> 00:01:00.710 one-sixth the mass of all the water in Earth's oceans. What's 16 00:01:00.730 --> 00:01:04.720 interesting is that incoming ultraviolet light should break up the carbon 17 00:01:04.740 --> 00:01:08.760 monoxide molecules in little more than a century, on average. 18 00:01:08.780 --> 00:01:12.820 This means that the carbon monoxide must be resupplied by the breakup of icy 19 00:01:12.840 --> 00:01:16.890 comets. To produce the amount of gas we detect, we're looking at the 20 00:01:16.910 --> 00:01:21.030 equivalent of the total destruction of a large comet every 5 minutes. 21 00:01:21.050 --> 00:01:25.090 From our data, we can tell that much of the carbon monoxide 22 00:01:25.110 --> 00:01:29.110 is in one or two massive clumps, which was very surprising. 23 00:01:29.130 --> 00:01:33.170 Because we're viewing the disk edge-on, we can't be sure if its one or 24 00:01:33.190 --> 00:01:37.200 two. Regardless, the comets suppling the gas must also 25 00:01:37.220 --> 00:01:41.220 be concentrated into clumps. How could this happen? 26 00:01:41.240 --> 00:01:45.290 If there is one clump, we think we're seeing the aftermath of collision 27 00:01:45.310 --> 00:01:49.310 between two icy planets about the mass of Mars. 28 00:01:49.330 --> 00:01:53.350 Such a collision would have occurred about half a million years ago, releasing large 29 00:01:53.370 --> 00:01:57.370 quantities of gas and small, comet-like fragments. The second 30 00:01:57.390 --> 00:02:01.430 --and we think more likely--scenario is that the carbon monoxide 31 00:02:01.450 --> 00:02:05.460 exists in two clumps and is continually replenished by by collisions in 32 00:02:05.480 --> 00:02:09.510 huge comet swarms. We believe the comets are shepherded together 33 00:02:09.530 --> 00:02:13.570 by an as-yet-undetected second planet whose gravity confines 34 00:02:13.590 --> 00:02:17.610 the comets into a small region so the frequently collide. A planet 35 00:02:17.630 --> 00:02:21.650 with roughly Saturn's mass could do the job. Other observations 36 00:02:21.670 --> 00:02:25.720 hint that the brightest clump is moving in a way that makes the two clump 37 00:02:25.740 --> 00:02:29.770 scenario more likely. Further observations will track it in better detail 38 00:02:29.790 --> 00:02:33.820 and help us confirm this dramatic picture. 39 00:02:33.840 --> 00:02:37.880 [Music][Beeping] 40 00:02:37.900 --> 00:02:41.920 [Beeping] 41 00:02:41.940 --> 00:02:50.417 [Beeping]