APOD: A/2017 U1: An Interstellar Visitor (2017 Nov 03)

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APOD: A/2017 U1: An Interstellar Visitor (2017 Nov 03)

Postby APOD Robot » Fri Nov 03, 2017 4:08 am

Image A/2017 U1: An Interstellar Visitor

Explanation: Traveling at high velocity along an extreme hyperbolic orbit and making a hairpin turn as it swung past the Sun, the now designated A/2017 U1 is the first known small body from interstellar space. A point of light centered in this 5 minute exposure recorded with the William Herschel Telescope in the Canary Islands on October 28, the interstellar visitor is asteroid-like with no signs of cometary activity. Faint background stars appear streaked because the massive 4.2 meter diameter telescope is tracking the rapidly moving A/2017 U1 in the field of view. Astronomer Rob Weryk (IfA) first recognized the moving object in nightly Pan-STARRS sky survey data on October 19. A/2017 is presently outbound, never to return to the Solar System, and already only visible from planet Earth in large optical telescopes. Though an interstellar origin has been established based on its orbit, it is still unknown how long the object could have drifted among the stars of the Milky Way. But its interstellar cruise speed would be about 26 kilometers per second. By comparison humanity's Voyager 1 spacecraft travels about 17 kilometers per second through interstellar space.

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RocketRon

Re: APOD: A/2017 U1: An Interstellar Visitor (2017 Nov 03)

Postby RocketRon » Fri Nov 03, 2017 4:27 am

Any indications or suggestions of why it appears to be shining (reflecting) so brightly ?

At that speed, the Solar System may not have existed when it set out, given how far away any origins may have been. !
Unless it was collided out of orbit within our Solar System ??

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Re: APOD: A/2017 U1: An Interstellar Visitor (2017 Nov 03)

Postby Chris Peterson » Fri Nov 03, 2017 4:47 am

RocketRon wrote:Any indications or suggestions of why it appears to be shining (reflecting) so brightly ?

What makes you think it is particularly bright?

At that speed, the Solar System may not have existed when it set out, given how far away any origins may have been. !
Unless it was collided out of orbit within our Solar System ??

Because its orbital speed is similar to that of the Sun, it is probably from a somewhat local source. It could be recently ejected, or it could predate the Solar System. There's really no way to know.
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RocketRon

Re: APOD: A/2017 U1: An Interstellar Visitor (2017 Nov 03)

Postby RocketRon » Fri Nov 03, 2017 6:09 am

[quote="Chris Peterson"]
What makes you think it is particularly bright?

The fact that it is a glowing bright spot in the photo !!
Relatively, of course, even if it is a long exposure.
If it is a coal black object, it could have been a little more difficult to photograph. (??)

Newspaper reports on this were that it came from way outside/above the ecliptic,
and will head off back out into empty space.
With more detail than the briefer APOD report.
And with (much ?) more speed than Apod reports too ?

Most press reports also used lots of words like if, maybe, perhaps, possibly,
which has been commented upon elsewhere.
Heading off UFO speculation, perhaps ??

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Re: APOD: A/2017 U1: An Interstellar Visitor (2017 Nov 03)

Postby Boomer12k » Fri Nov 03, 2017 8:22 am

An amazing find... an ISO... interStellar object...

Bon Voyage....

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Re: APOD: A/2017 U1: An Interstellar Visitor (2017 Nov 03)

Postby Anortham@mymts.net » Fri Nov 03, 2017 9:37 am

Could this be a Kuiper Belt Object (KBO)?
It is likely to be icy because of its high albedo.
The orbit was stated to be hyperbolic which implies not a closed orbit.
Yet it warped space-time sufficiently to perform a hairpin around Sol.

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Re: APOD: A/2017 U1: An Interstellar Visitor (2017 Nov 03)

Postby De58te » Fri Nov 03, 2017 9:53 am

My speculation of its origin. The "first recognized" link from the University of Hawaii says that it came from the direction of the constellation of Lyra. Lyra is of course a huge space, but the closest star there is Vega at 26 ly. Wonder if they can trace it to Vega, taking in consideration A2017 U1 speed and the speed of the Sun and Vega around the Milky Way. Other stars origin could be Beta Lyrae which is a double star several times larger than the Sun and so close together that that they orbit each other in 12 days. Any asteroid forming there would be quickly kicked out of that system. Interesting, however they are 300 light years away. That would mean its interstellar journey was a really long time. Epsilon Lyrae is also a double star some 125 ly away. My guess goes for Vega.

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Re: APOD: A/2017 U1: An Interstellar Visitor (2017 Nov 03)

Postby BillT » Fri Nov 03, 2017 9:58 am

I have seen the albedo estimated to be around ten percent which isn't a lot different to the Moon. Quite dark compared to icy bodies if the estimates are accurate.

I wouldn't make any guess at origin since it's speed relative to the Sun (when the asteroid was well out in interstellar space) is quite typical of the relative speeds of stars in the neighbourhood of the Sun.

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Re: APOD: A/2017 U1: An Interstellar Visitor (2017 Nov 03)

Postby hamilton1 » Fri Nov 03, 2017 10:09 am

I wonder what speed would be necessary to zip straight past the sun instead of being forced into a 'hairpin turn'...?

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Re: APOD: A/2017 U1: An Interstellar Visitor (2017 Nov 03)

Postby neufer » Fri Nov 03, 2017 11:27 am

hamilton1 wrote:
I wonder what speed would be necessary to zip straight past the sun instead of being forced into a 'hairpin turn'...?

Actually the Sun bumped into A/2017 U1:

viewtopic.php?f=31&t=37698&start=25#p276469
viewtopic.php?f=31&t=37698

For the Sun to have had little effect after passing so close to the asteroid their relative speed would have been on the order of 100 km/s.
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Re: APOD: A/2017 U1: An Interstellar Visitor (2017 Nov 03)

Postby hamilton1 » Fri Nov 03, 2017 12:41 pm

Thanks Art.

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Re: APOD: A/2017 U1: An Interstellar Visitor (2017 Nov 03)

Postby sillyworm2 » Fri Nov 03, 2017 1:02 pm

Someone is hurling stones at us.

JTsyo

Re: APOD: A/2017 U1: An Interstellar Visitor (2017 Nov 03)

Postby JTsyo » Fri Nov 03, 2017 1:19 pm

Any info of its path through the solar system? Did it come close to earth and we only saw it on the way out or was the path much further out?

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Re: APOD: A/2017 U1: An Interstellar Visitor (2017 Nov 03)

Postby Chris Peterson » Fri Nov 03, 2017 1:22 pm

RocketRon wrote:
Chris Peterson wrote:What makes you think it is particularly bright?

The fact that it is a glowing bright spot in the photo !!
Relatively, of course, even if it is a long exposure.
If it is a coal black object, it could have been a little more difficult to photograph. (??)

It is a dark object. You can't tell much from an image about something's intrinsic albedo. That requires quantitative measurements of the data with known references. And in fact, this was difficult to photograph, in the sense of requiring a large aperture telescope.
Chris

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Re: APOD: A/2017 U1: An Interstellar Visitor (2017 Nov 03)

Postby Chris Peterson » Fri Nov 03, 2017 1:25 pm

Anortham@mymts.net wrote:Could this be a Kuiper Belt Object (KBO)?

Not from our Kuiper belt.

It is likely to be icy because of its high albedo.

It does not have a high albedo. Its albedo is typical of many asteroids, and the fact that this displayed no outgasing near perihelion argues for a rocky body, not an icy one.

The orbit was stated to be hyperbolic which implies not a closed orbit.
Yet it warped space-time sufficiently to perform a hairpin around Sol.

Its change of direction around the Sun has much more to do with the degree that the Sun warps space-time than this asteroid!
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Re: APOD: A/2017 U1: An Interstellar Visitor (2017 Nov 03)

Postby neufer » Fri Nov 03, 2017 1:27 pm

JTsyo wrote:
Any info of its path through the solar system? Did it come close to earth
and we only saw it on the way out or was the path much further out?

viewtopic.php?f=31&t=37698
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Re: APOD: A/2017 U1: An Interstellar Visitor (2017 Nov 03)

Postby geckzilla » Fri Nov 03, 2017 2:09 pm

It looks like it was traveling close to perpendicular with the galactic plane before it encountered Sol. I imagine its long, lonely path through the galaxy to oscillate through the galactic plane more now than it did before.
Just call me "geck" because "zilla" is like a last name.

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Re: APOD: A/2017 U1: An Interstellar Visitor (2017 Nov 03)

Postby neufer » Fri Nov 03, 2017 2:40 pm

geckzilla wrote:
It looks like it was traveling close to perpendicular with the galactic plane before it encountered Sol. I imagine its long, lonely path through the galaxy to oscillate through the galactic plane more now than it did before.

    A/2017 U1 was traveling with almost the same speed & direction
    (i.e., a relative velocity vector of merely 26 km/s) as our own Sun (moving at 220 km/s).

    A/2017 U1 will continue traveling with almost the same speed & direction
    (i.e., a relative velocity vector of merely 26 km/s) as our own Sun (moving at 220 km/s).
https://en.wikipedia.org/wiki/Milky_Way ... ighborhood wrote:
<<The orbital speed of the Solar System about the center of the Milky Way is approximately 220 km/s. The general direction of the Sun's Galactic motion is towards the star Vega near the constellation of Hercules, at an angle of roughly 60 sky degrees to the direction of the Galactic Center. The Sun's orbit about the Milky Way is expected to be roughly elliptical with the addition of perturbations due to the Galactic spiral arms and non-uniform mass distributions. In addition, the Sun passes through the Galactic plane approximately 2.7 times per orbit. This is very similar to how a simple harmonic oscillator works with no drag force (damping) term.>>

The asteroid will be sent out from the Sun at a relative velocity of 26 km/s and at an angle of 36° below the Galactic plane for a relative vertical velocity = -15 km/s [= 26 sin(-36°)].

However the Sun is currently moving at a velocity of 220 km/s and at an angle of 18° above the Galactic plane for an absolute vertical velocity = 67 km/s [= 220 sin(18°)].

Hence the absolute vertical velocity of the asteroid is just 52 km/s [= 67 - 15] : thus less than the Sun and like the Sun confined to the disk.
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Re: APOD: A/2017 U1: An Interstellar Visitor (2017 Nov 03)

Postby geckzilla » Fri Nov 03, 2017 3:20 pm

I appreciate your effort, Art. It's hard to understand the relative and absolute motions of each object when all I have to go on is a short animation. Your car chase image would probably be more useful as an analogy if I had any clue what it was about.
Just call me "geck" because "zilla" is like a last name.

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Re: APOD: A/2017 U1: An Interstellar Visitor (2017 Nov 03)

Postby IamOuibe » Fri Nov 03, 2017 3:26 pm

I am curious as to whether our current technology would allow us to detect a Voyager or Pioneer probe that enters our solar system.

oldwierdgeek

Re: APOD: A/2017 U1: An Interstellar Visitor (2017 Nov 03)

Postby oldwierdgeek » Fri Nov 03, 2017 3:35 pm

Let's have our largest telescopes track it as long as they can. You know - just in case it takes a while for them to wake up and turn on the engines to come back to investigate this source of modulated radio emissions... (Cue ominous music)

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Re: APOD: A/2017 U1: An Interstellar Visitor (2017 Nov 03)

Postby APODFORIST » Fri Nov 03, 2017 3:45 pm


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Re: APOD: A/2017 U1: An Interstellar Visitor (2017 Nov 03)

Postby BDanielMayfield » Fri Nov 03, 2017 3:51 pm

IamOuibe wrote:I am curious as to whether our current technology would allow us to detect a Voyager or Pioneer probe that enters our solar system.

It depends on how close it gets. Also on chance, like if it flies into the field of view of a large telescope while someone is looking taking pictures. (Must have photographic evidence to be believed.) :wink:

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Re: APOD: A/2017 U1: An Interstellar Visitor (2017 Nov 03)

Postby neufer » Fri Nov 03, 2017 3:58 pm

geckzilla wrote:
I appreciate your effort, Art.
It's hard to understand the relative and absolute motions of each object when all I have to go on is a short animation.

Click to play embedded YouTube video.
The important thing is that the Sun, Vega, the asteroid and the local neighborhood are all moving along more or less together within the galactic disk at about 220 km/s. :arrow:

Should we every have an Interstellar Visitor coming in at ~200 km/s (e.g., a 12 gauge shotgun round) :arrow:
then we might start talking about it being an Intergalactic disk Visitor as well.

geckzilla wrote:
Your car chase image would probably be more useful as an analogy if I had any clue what it was about.
Art Neuendorffer

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Re: APOD: A/2017 U1: An Interstellar Visitor (2017 Nov 03)

Postby neufer » Fri Nov 03, 2017 4:15 pm

BDanielMayfield wrote:
IamOuibe wrote:
I am curious as to whether our current technology would allow us to detect a Voyager or Pioneer probe that enters our solar system.

It depends on how close it gets. Also on chance, like if it flies into the field of view of a large telescope while someone is looking taking pictures. (Must have photographic evidence to be believed.) :wink:

    Assuming it had stopped sending radio signals it would probably have to be within a few million kilometers.
https://en.wikipedia.org/wiki/ESA_Space ... _Telescope wrote:
<<The ESA Space Debris Telescope is located at the Teide Observatory on the island of Tenerife, Spain. The telescope is ESA's Optical Ground Station forming a part of the Artemis experiment. As a large part of the observation time is dedicated to space debris surveys, in particular the observation of space debris in the geostationary ring and in geostationary transfer orbits, the term ESA Space Debris Telescope became used very frequently. Space debris surveys are carried out every month, centered on New Moon. The telescope is a Ritchey-Chrétien telescope with an aperture of 1 m and field of view of 0.7 degrees, equipped with a cryogenically cooled mosaic CCD-Camera of 4k*4k pixels. The detection threshold is between 19th and 21st magnitude, which corresponds to a capability to detect space debris objects as small as 10 cm in the geostationary ring.>>
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