#### Re: {MPML} Re: C/2017 U1 (PANSTARRS) = P10Ee5V

Sam Deen

If it wasn't so late, I'd probably run a calculation on the odds that an object traveling in a straight line would run into a star less than 1 LY away over ~100 LY.

At any rate, any search for the progenitor (even if it is a direct object) would need to be very deep. In my opinion, it's more likely to find it was ejected from a red dwarf than a more massive star.

~Sam

On Sunday, October 29, 2017 12:39 AM, "George Herbert george.herbert@... [mpml]" wrote:

Nothing major in Vega now works so far, out to distances in the 1400 LY range. I've run smaller lists not full catalog/ Hipparcos etc. Someone will need to run full catalog (have a bored PhD student?...)

The statistical argument that it's likely been in interstellar space for order of magnitude 10s of galactic orbits (3+ Gigayear) argues that we'll never have a good answer, because uncertainty in everything's motions over more than a fraction of a galactic orbit is too high.

George William Herbert

> On Oct 29, 2017, at 12:22 AM, Jon.Giorgini@... [mpml] >
>> On 10/27/2017 11:24 PM, Sam Deen wrote:
>> ......
>> At any rate, I'm confident that within the month we'll be able to find
>> the progenitor star: ...
>
>> On 10/28/2017 4:19 PM, Al Harris wrote:
>>
>> Well, no, I'd say the odds are less than the proverbial snowball's
>> chance in hell. U1's velocity approaching the sun was 26 km/sec, and
>> will be essentially unchanged leaving. 26 km/sec is about .0001 the
>> speed of light, so the object goes about one light year in 10,000 years,
>> a hundred light years in a million years, and a hundred thousand light
>> years in a billion years,
>
> The limited sample of the motion will also work against back-tracking
> origination at some level. There is currently only tracking data after
> the September 9th 0.254 au perihelion.
>
> In 3000 BC, the formal (i.e., optimistic) heliocentric uncertainties
> of the current orbit solution (JPL #4) are +/- 1.7439 degrees in RA and
> +/- 0.9676 degrees in DEC (3-sigma), around Galactic System II longitude
> and latitude (63.3059, 16.7968) degrees.
>
> In terms of absolute location uncertainty, ICRF cartesian 1-sigma
> position vector uncertainties for A/2017 U1 in 3000 BC are:
>
> X +/- 227.793 au,
> Y +/- 317.755 au,
> Z +/- 3.728 au
>
> Growth in ICRF position 1-sigma uncertainties will have a RATE of:
>
> delta_x = +0.0462 au/yr,
> delta_y = +0.0644 au/yr,
> delta_z = +0.0007 au/yr
>
> So A/2017 U1's position uncertainty is growing at a rate of about
> 1 light year per 800,000 years.
>
> The velocity 1-sigma ICRF uncertainties in 3000 BC:
>
> V_x +/- 215 m/s,
> V_y +/- 300 m/s,
> V_z +/- 0.003 m/s
>
> Uncertainties can narrow a little if additional astrometry is obtained
> over the remaining days of detectability, but the most useful for improved
> back-tracking would have been data prior to perihelion.
>
> Then there is the issue of matching the growing volume of space where
> A/2017 U1 could have been against the historical 3-D motion of stars through
> the galaxy over great spans of time.
>
> But if a possible solution is only a couple hundred light years or less
> out, and not much else is around, maybe a case could be made.
> ----------------------------------------------------------
> Jon Giorgini | Navigation & Mission Design Section
> Senior Analyst | Solar System Dynamics Group
> Jon.Giorgini@... | Jet Propulsion Laboratory
> ----------------------------------------------------------
>
>
> ------------------------------------
> Posted by: Jon.Giorgini@...
> ------------------------------------
>
> ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
>
> Posts to this list or information found within may be freely used, with the stipulation that MPML and the originating author are cited as the source of the information.
> ------------------------------------
>