1 00:00:01,560 --> 00:00:09,780 In 2017 astronomers discovered `Oumuamua: the first interstellar object in our Solar System. 2 00:00:11,400 --> 00:00:19,640 Now the NASA/ESA Hubble Space Telescope has found that it is leaving our Solar System faster than expected. 3 00:00:22,640 --> 00:00:28,600 The first time we discussed it, we were saying: Oh my god, oh my god. We really need to check and check 4 00:00:28,600 --> 00:00:33,020 and double check and make really sure, because the effect is so small 5 00:00:33,020 --> 00:00:39,220 and so subtle that many things could go and screw up your measurements. 6 00:00:39,220 --> 00:00:45,720 And after checking and double checking, and cross-checking, the effect was still there! 7 00:00:48,340 --> 00:00:54,840 But astronomers might have already found an intriguing explanation to this observation. 8 00:01:02,440 --> 00:01:06,900 Hubble sees `Oumuamua getting a boost 9 00:01:08,080 --> 00:01:13,880 `Oumuamua first came to the attention of astronomers by the end of 2017. 10 00:01:14,960 --> 00:01:22,320 Observatories around the world discovered that the object was a lonely voyager from interstellar space 11 00:01:23,860 --> 00:01:26,780 the first of its kind to be observed. 12 00:01:33,380 --> 00:01:41,000 For the first time we had evidence of an asteroid, an object, that was coming at a very high velocity into our Solar System. 13 00:01:41,000 --> 00:01:46,200 And the velocity was so high that it proved that the object was actually coming from the outside 14 00:01:46,200 --> 00:01:50,900 that it was coming probably from another Solar System, and was just passing into our System. 15 00:01:51,800 --> 00:01:58,800 Astronomers using Hubble and other observatories to study it in more detail have now found something odd 16 00:01:59,620 --> 00:02:05,620 this peculiar object is moving faster than the laws of celestial mechanics predict. 17 00:02:06,840 --> 00:02:10,800 A result that caught the scientists by surprise! 18 00:02:12,300 --> 00:02:17,760 We considered different values. One of them is an interaction with some magnetic field. 19 00:02:17,760 --> 00:02:26,180 Or another one would be an interaction with a force going along the trajectory 20 00:02:26,180 --> 00:02:29,500 not really knowing what it would be, just to see if it works. 21 00:02:29,500 --> 00:02:36,180 Or a force that would be an impulse; like a small outburst or something like that. 22 00:02:36,180 --> 00:02:38,780 And all these hypothesis failed. 23 00:02:41,200 --> 00:02:47,040 The most likely explanation for `Oumuamua’s odd behaviour is that it is outgassing. 24 00:02:48,860 --> 00:02:53,380 Outgassing occurs when sunlight heats up the surface of an object. 25 00:02:54,260 --> 00:02:58,680 This causes it to vent a plume of gas that acts like a booster rocket. 26 00:02:59,820 --> 00:03:06,640 However, outgassing is a typical behaviour of comets, which now leads astronomers to suggest 27 00:03:06,640 --> 00:03:11,740 `Oumuamua is an interstellar comet, rather than an asteroid. 28 00:03:14,580 --> 00:03:19,880 However, `Oumuamua shows no trace of typical cometary features. 29 00:03:21,060 --> 00:03:27,280 The interstellar visitor does not show a characteristic long tail of evaporating material. 30 00:03:27,880 --> 00:03:34,760 It also shows no evidence for a coma, an envelope of gas and dust surrounding most comets. 31 00:03:36,340 --> 00:03:45,020 In terms of the quantity of dust and gas that is released: it’s tiny. It is really not much. 32 00:03:45,020 --> 00:03:48,580 But it is very small, so you don’t expect a lot of dust. 33 00:03:48,580 --> 00:03:58,100 And still, again, comparing with normal comets it’s about right for such a small comet to have so little gas. 34 00:03:58,960 --> 00:04:05,000 Astronomers speculate that perhaps the small dust grains adorning the surface of most comets 35 00:04:05,000 --> 00:04:12,660 eroded during `Oumuamua’s journey through interstellar space, with only larger dust grains remaining. 36 00:04:13,200 --> 00:04:19,000 A cloud of these larger particles would not be bright enough to be detected by Hubble. 37 00:04:21,800 --> 00:04:26,400 The true nature of this interstellar nomad may remain a mystery 38 00:04:26,940 --> 00:04:35,240 `Oumuamua’s recently-detected gain in speed makes it unlikely that we will be able to accurately trace its origin. 39 00:04:35,900 --> 00:04:40,840 And as it is getting further away from Earth it becomes too distant 40 00:04:40,840 --> 00:04:44,600 for even the best telescopes in the world to observe. 41 00:04:47,220 --> 00:04:53,460 We have never observed a comet like that before. But it’s possible. We have never seen one. 42 00:04:53,460 --> 00:04:57,160 So, many differences, many things in common. 43 00:04:57,160 --> 00:05:02,220 So we really need to wait for the next one to start making comparisons. 44 00:05:02,880 --> 00:05:06,240 So the hope is that in the future, with better telescopes 45 00:05:06,240 --> 00:05:10,420 and small telescopes searching the skies for asteroids, we will find more of these objects. 46 00:05:11,620 --> 00:05:18,240 But what we have learned from `Oumuamua surprised us beyond our wildest imagination.