Author Topic: Hyperbolic Hyperbole or Interstellar Interloper? ('Oumuamua)  (Read 74457 times)

Offline hop

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Re: Hyperbolic Hyperbole or Interstellar Interloper?
« Reply #100 on: 11/10/2017 07:22 AM »
Project Lyra: Sending a Spacecraft to 1I/'Oumuamua (former A/2017 U1), the Interstellar Asteroid
Andreas M. Hein, Nikolaos Perakis, Kelvin F. Long, Adam Crowl, Marshall Eubanks, Robert G. Kennedy III, Richard Osborne

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The first definitely interstellar object 1I/'Oumuamua (previously A/2017 U1) observed in our solar system provides the opportunity to directly study material from other star systems. Can such objects be intercepted? The challenge of reaching the object within a reasonable timeframe is formidable due to its high heliocentric hyperbolic excess velocity of about 26 km/s; much faster than any vehicle yet launched. This paper presents a high-level analysis of potential near-term options for such a mission. Launching a spacecraft in a reasonable timeframe of 5-10 years requires a hyperbolic solar system excess velocity between 33 to 76 km/s for mission durations between 30 to 5 years. Different mission durations and their velocity requirements are explored with respect to the launch date, assuming direct impulsive transfer to the intercept trajectory. Several technology options are outlined, ranging from a close solar Oberth Maneuver using chemical propulsion, and the more advanced options of solar and laser sails. To maximize science return decelerating the spacecraft at 'Oumuamua is highly desirable, due to the minimal science return from a hyper-velocity encounter. It is concluded that although reaching the object is challenging, there seem to be viable options based on current and near-term technology.

Offline Ben the Space Brit

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Re: Hyperbolic Hyperbole or Interstellar Interloper?
« Reply #101 on: 11/10/2017 10:38 AM »
Question based on curiosity: Could a spacecraft capable of such high velocities (and, likely, sustained acceleration) as needed to intercept Oumuamua-class objects be practical for true interstellar missions to such targets as Proxima-b? More propellent would obviously be indicated as well as a long-duration power system and long-range communications system but nothing is obviously unthinkable, especially as any interception of Oumuamua-class objects would most likely be in broadly the same domain as currently being traversed by Voyager-1.
« Last Edit: 11/10/2017 10:40 AM by Ben the Space Brit »
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Offline nacnud

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Re: Hyperbolic Hyperbole or Interstellar Interloper?
« Reply #102 on: 11/10/2017 10:48 AM »
You'd need to be moving about 27 km/s in relation to the sun at infinity to catch up with Oumuamua, or 50km/s at 1AU.

To get to Proxima B would then take another 47,000 years.

Offline hop

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Re: Hyperbolic Hyperbole or Interstellar Interloper?
« Reply #103 on: 11/10/2017 06:06 PM »
To get to Proxima B would then take another 47,000 years.
Yeah, catching 'Oumuamua requires a few x faster than Voyager, which is nothing on interstellar scales. OTOH, if one thinks that something like Breakthrough Starshot could be launched in the next few decades, this should be an absolute piece of cake in comparison: 1/100th the performance would be overkill. YMMV as to how this speaks to the credibility of the respective proposals ;)

One issue not addressed in the Hein preprint is actually finding  'Oumuamua again. It was barely visible in ~meter class telescopes when it was ~1 au from the Sun and < 1 au from Earth. At the proposed intercept distances of tens of au from the Sun, it will be thousands of times fainter. So unless the spacecraft has an absurdly large telescope, the trajectory would need to be known precisely enough to get within a fraction of an au blind. Given that it will be too faint for Hubble within a couple months, this seems very unlikely.

edit:
To be fair, they do touch on the problem briefly, but without any numbers:
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The small size of the object and its low albedo will make it difficult to observe it once it has entered deep space again. This means the navigation problem of getting a sufficiently accurate fix on 1I/‘Oumuamua to get close enough to the object to send back useful data is considerable. Due to the positional uncertainty of such a difficult-to-track object, a distributed, swarm-based mission design that is able to span a large area, should be investigated.
« Last Edit: 11/11/2017 07:52 PM by hop »

Offline Mongo62

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Re: Hyperbolic Hyperbole or Interstellar Interloper?
« Reply #104 on: 11/13/2017 01:20 AM »
A short but particularly interesting paper:

The origin of interstellar asteroidal objects like 1I/2017 U1

Quote
With the recently discovered interstellar object 1I/2017U1 (1I/'Oumuamua) we have to realize that the Solar System is not isolated, but part of a larger environment with which we interact. We compare the kinematics of 1I/2017U1 with simulations of the Milky Way Galaxy and Gaia TGAS data to estimates the local density of objects similar to 1I/2017U1 and to investigate its possible origin. We find that about 1.3 Myr ago 1I/2017U1 has passed within a distance of 0.16 pc from the nearby star TYC4742-1027-1. It seems unlikely that 1I/2017U1 originated from an Oort-cloud around this star, but it simply trespassed on its way through.

Based on our calculations we conclude that the population of sola lapis (unbound asteroidal objects) is much larger than that of cometary objects. The number of objects with characteristics similar to 1I/2017U1 must be very common, we estimate a population density of ≈3×10^5 similarly sized objects within 100 au from the Sun or ∼10^14 per cubic parsec in the Solar neighborhood. By comparing the results of simulations of the Milky Way Galaxy with the Gaia DR1 TGAS we conclude that the kinematics of 1I/2017U1 is consistent with that expected from interstellar distribution of isolated objects that are part of the local Galactic potential. It is then hard to predict how long 1I/2017 U1 has been roaming the Galaxy before it visited the Solar System.

We subsequently argue that the Galaxy is rich in solae lapides such as 1I/2017U1. We speculate that such an object is formed in a debris disk as left over from the star and planet formation process. Upon interaction with other stars in the parental star cluster or due to resonant interactions within the planetary disk these objects are liberated from their parental star and float freely in the interstellar space. We just met 1I/2017 U1 by chance, and with the derived mean Galactic density we expect such visitors to be very common.
« Last Edit: 11/13/2017 01:27 AM by Mongo62 »

Offline Lar

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Re: Hyperbolic Hyperbole or Interstellar Interloper?
« Reply #105 on: 11/13/2017 02:07 AM »
if the expectation is that such visitors are likely to be common, what changed? That is, why is this the first one detected? Did we gain some big new capability that lets us find them where previously we could not?
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Offline hop

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Re: Hyperbolic Hyperbole or Interstellar Interloper?
« Reply #106 on: 11/13/2017 04:42 AM »
if the expectation is that such visitors are likely to be common, what changed? That is, why is this the first one detected?
"Common" is relative. The paper tries to infer how many are out there based on the fact that Pan-STARRS has detected one in it's operational lifetime. It definitely doesn't imply that we should have seen more, but is does suggest that there many thousands passing through the larger solar neighborhood.

Offline ugordan

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Re: Hyperbolic Hyperbole or Interstellar Interloper?
« Reply #107 on: 11/13/2017 06:26 AM »
That is, why is this the first one detected?

The answer may lie in the fact that this particular object happened to fly fairly close to Earth on its outbound leg.

Offline jebbo

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Re: Hyperbolic Hyperbole or Interstellar Interloper?
« Reply #108 on: 11/13/2017 07:21 AM »
if the expectation is that such visitors are likely to be common, what changed? That is, why is this the first one detected?
"Common" is relative. The paper tries to infer how many are out there based on the fact that Pan-STARRS has detected one in it's operational lifetime. It definitely doesn't imply that we should have seen more, but is does suggest that there many thousands passing through the larger solar neighborhood.

There is an expectation that when LSST is operational (first light 2019), that we will find quite a lot more ... and hopefully much earlier.

Objects like this are our easiest way of studying extrasolar material; way easier than visiting, say, proxima Centauri.

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Offline Star One

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Re: Hyperbolic Hyperbole or Interstellar Interloper?
« Reply #109 on: 11/13/2017 07:40 AM »
A short but particularly interesting paper:

The origin of interstellar asteroidal objects like 1I/2017 U1

Quote
With the recently discovered interstellar object 1I/2017U1 (1I/'Oumuamua) we have to realize that the Solar System is not isolated, but part of a larger environment with which we interact. We compare the kinematics of 1I/2017U1 with simulations of the Milky Way Galaxy and Gaia TGAS data to estimates the local density of objects similar to 1I/2017U1 and to investigate its possible origin. We find that about 1.3 Myr ago 1I/2017U1 has passed within a distance of 0.16 pc from the nearby star TYC4742-1027-1. It seems unlikely that 1I/2017U1 originated from an Oort-cloud around this star, but it simply trespassed on its way through.

Based on our calculations we conclude that the population of sola lapis (unbound asteroidal objects) is much larger than that of cometary objects. The number of objects with characteristics similar to 1I/2017U1 must be very common, we estimate a population density of ≈3×10^5 similarly sized objects within 100 au from the Sun or ∼10^14 per cubic parsec in the Solar neighborhood. By comparing the results of simulations of the Milky Way Galaxy with the Gaia DR1 TGAS we conclude that the kinematics of 1I/2017U1 is consistent with that expected from interstellar distribution of isolated objects that are part of the local Galactic potential. It is then hard to predict how long 1I/2017 U1 has been roaming the Galaxy before it visited the Solar System.

We subsequently argue that the Galaxy is rich in solae lapides such as 1I/2017U1. We speculate that such an object is formed in a debris disk as left over from the star and planet formation process. Upon interaction with other stars in the parental star cluster or due to resonant interactions within the planetary disk these objects are liberated from their parental star and float freely in the interstellar space. We just met 1I/2017 U1 by chance, and with the derived mean Galactic density we expect such visitors to be very common.

I see they didn’t bother using its ‘common’ name, which most of the more recent papers seem too.

Offline Blackstar

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Re: Hyperbolic Hyperbole or Interstellar Interloper?
« Reply #110 on: 11/13/2017 12:10 PM »
A new paper addresses how one might launch a space mission to this object:

https://arxiv.org/abs/1711.03155

I have attached the paper.

Offline Dao Angkan

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Re: Hyperbolic Hyperbole or Interstellar Interloper?
« Reply #111 on: 11/13/2017 09:23 PM »
That is, why is this the first one detected?

The answer may lie in the fact that this particular object happened to fly fairly close to Earth on its outbound leg.

Right, it's hard to make statistics off of a sample of one, but the fact that one has come so close to Earth, within only a few years of operation for this instrument (which isn't even specifically designed to detect extra-solar visitors) suggests that these bodies could be quite common. Now we can consider potential surveys which would be optimised to specifically search for extra-solar visitors.

If we have a survey which starts to regularly detect these objects, then maybe we can have a realistic chance to design a mission to visit one.
« Last Edit: 11/13/2017 09:24 PM by Dao Angkan »

Offline Dao Angkan

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Re: Hyperbolic Hyperbole or Interstellar Interloper?
« Reply #112 on: 11/13/2017 09:36 PM »
A new paper addresses how one might launch a space mission to this object:

https://arxiv.org/abs/1711.03155

I have attached the paper.

This was posted above, it's an interesting paper, but I think a more realistic proposition would be to have a survey specifically searching for these objects so that we can launch a probe at short notice.

The "solar fry-by" sounds interesting, but seems to fly even closer than the Parker Solar Probe, although admittedly only once, so may be reasonable, still, it's pretty low TRL. Is there another mission we could try the "solar fry-by" on as a technology demonstrator?

If refueled BFR and "solar fry-by" both come to fruition, then that would open up some amazing opportunities for outer-solar system exploration.
« Last Edit: 11/13/2017 09:43 PM by Dao Angkan »

Offline hop

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Re: Hyperbolic Hyperbole or Interstellar Interloper?
« Reply #113 on: 11/13/2017 09:47 PM »
If we have a survey which starts to regularly detect these objects, then maybe we can have a realistic chance to design a mission to visit one.
And unless this was a fluke LSST should be that survey.

The Cook et al paper linked earlier predicted LSST should detect between 0.0001 and 1 interstellar object per year. The fact Pan-STARRS spotted one suggests the real number is on the high end of that estimate.
« Last Edit: 11/16/2017 07:06 AM by hop »

Offline Mongo62

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Re: Hyperbolic Hyperbole or Interstellar Interloper?
« Reply #114 on: 11/15/2017 01:12 PM »
APO Time Resolved Color Photometry of Highly-Elongated Interstellar Object 1I/'Oumuamua

We report on the g, r and i band observations of the Interstellar Object 1I/'Oumuamua taken on 2017 October 29 from 04:28 to 08:40 UTC from the Apache Point Observatory (APO) 3.5m telescope's ARCTIC camera. We use these observations to estimate object colors, and find them to be g−r=0.41±0.24 and r−i=0.23±0.25, consistent with visible spectra (Masiero 2017; Ye et al. 2017; Fitzsimmons et al. 2017) and most comparable to the population of Solar System C/D asteroids, Trojans, or comets, although we find no evidence of any cometary activity, even 1.5 months after 1I/'Oumuamua's close flyby of the Sun. Significant brightness variability was seen in the r observations, with the object becoming notably brighter towards the end of the run. By combining our APO photometric time series data with the Discovery Chanel Telescope (DCT) data of Knight et al. 2017 taken 20 h later on 2017 October 30, we construct an almost complete lightcurve with a most probable lightcurve period of P≃4 h, and reveal the most useful locations during 1I/'Oumuamua's rotation phase for additional data to improve constraints on its lightcurve. This implies a double peaked rotation period of 8.1 ± 0.02 h, with a peak-to-peak amplitude of 1.5 - 2.1 mags. The two values imply that 1I/'Oumuamua has an axial ratio of 4.1 to 6.9 and is rotating below its critical break up limit for most viable values of density and cohesive strength within the range of rotation periods and axial ratios compatible with our data. Our results are compatible with 1I/'Oumuamua having a density > 1.0 g cm−3 or having modest cohesive strength. Astrometry useful for constraining the object's orbit was also obtained and published in Weaver et al. 2017.

Offline hop

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Re: Hyperbolic Hyperbole or Interstellar Interloper?
« Reply #115 on: 11/15/2017 08:45 PM »
The two values imply that 1I/'Oumuamua has an axial ratio of 4.1 to 6.9
They note in the paper that this is pretty far outside the normal range for known solar system objects in this size range. For perspective, I'd think of Itokawa as an example of a fairly oblong asteroid, but it's only ~2.

Both APO and DCT seem to support this extreme lightcuve (and IIRC there were hints from earlier observation) so it's not likely to be totally in error.

Offline JasonAW3

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Re: Hyperbolic Hyperbole or Interstellar Interloper?
« Reply #116 on: 11/15/2017 08:48 PM »
The two values imply that 1I/'Oumuamua has an axial ratio of 4.1 to 6.9
They note in the paper that this is pretty far outside the normal range for known solar system objects in this size range. For perspective, I'd think of Itokawa as an example of a fairly oblong asteroid, but it's only ~2.

Both APO and DCT seem to support this extreme lightcuve (and IIRC there were hints from earlier observation) so it's not likely to be totally in error.

Anybody do a spectrograph of the reflected light yet?
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Offline hop

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Re: Hyperbolic Hyperbole or Interstellar Interloper?
« Reply #117 on: 11/15/2017 09:35 PM »
Anybody do a spectrograph of the reflected light yet?
Yes, see this post and the second paper in this post. Others have also obtained spectra that aren't published yet but are generally similar, for example Alan Fitzsimmons tweeted this one.

The tl;dr is that it's featureless (no obviously identifiable absorption features) with a red slope (reflects more at longer wavelengths than shorter ones). This is similar to some asteroids and KBOs, but that doesn't necessarily mean they are made of the same stuff.

Offline eric_astro

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Re: Hyperbolic Hyperbole or Interstellar Interloper?
« Reply #118 on: 11/15/2017 09:36 PM »
You'd need to be moving about 27 km/s in relation to the sun at infinity to catch up with Oumuamua, or 50km/s at 1AU.

To get to Proxima B would then take another 47,000 years.

But if you woke up in 47,000 years, Proxima would be at about 3 light years from earth!

Online KelvinZero

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Re: Hyperbolic Hyperbole or Interstellar Interloper?
« Reply #119 on: 11/15/2017 11:20 PM »
The two values imply that 1I/'Oumuamua has an axial ratio of 4.1 to 6.9
They note in the paper that this is pretty far outside the normal range for known solar system objects in this size range. For perspective, I'd think of Itokawa as an example of a fairly oblong asteroid, but it's only ~2.

Both APO and DCT seem to support this extreme lightcuve (and IIRC there were hints from earlier observation) so it's not likely to be totally in error.
Weird. Surely this would be a binary? A ratio of 6.9 would be like a skinny finger.

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