'Oumuamua

Reference is to:

https://en.wikipedia.org/wiki/%CA%BBOumuamua

In the opening paragrapgh, it states: "[...] is the first known
interstellar object to pass through the Solar System"

Much later, in section "Hypothetical space missions", the penultimate
sentence reads: "That said, astronomers estimate that interstellar objects
similar to 'Oumuamua pass inside the orbit of Earth several times per
year."

So, the first obvious question is, if these things are so common, why did
it take so long to notice one? I supposes that the answer is simply that
"inside the orbit of the Earth" covers a lot of area compared to roughly
the area of Mercury's orbit (where we noticed 'Oumuamua).

But what I really want to know is whether or not anyone else feels that the
orbit as a whole is sort of suspicious. By that I mean that it made an
acute course change. If one wanted to perform such a course change, the
approach must be made extrememly accurately.

Of course, such a manouver might easily be made once in a while 'by
accident', if these things are as numerous as they say. It just seems
strange to me that the very first time we ever see an object from outside
of our Solar System, is passes closer to the Sun than any object within our
Solar System.

On Saturday, December 2, 2017 at 8:49:51 PM UTC-7, Mike_Duffy wrote:
It just seems
strange to me that the very first time we ever see an object from outside
of our Solar System, is passes closer to the Sun than any object within our
Solar System.

The perihelion of 'Oomuamua is 0.25534 AU, which is indeed within the orbit of
Mercury (semi-major axis, 0.387 AU). However, the perihelion of Icarus is 0.1867
AU, so there are objects in our Solar System that pass closer to the Sun than it
did.

John Savard

On Sunday, 3 December 2017 07:56:34 UTC+1, Quadibloc wrote:
On Saturday, December 2, 2017 at 8:49:51 PM UTC-7, Mike_Duffy wrote:
It just seems
strange to me that the very first time we ever see an object from outside
of our Solar System, is passes closer to the Sun than any object within our
Solar System.

The perihelion of 'Oomuamua is 0.25534 AU, which is indeed within the orbit of
Mercury (semi-major axis, 0.387 AU). However, the perihelion of Icarus is 0.1867
AU, so there are objects in our Solar System that pass closer to the Sun than it
did.

John Savard

Which natural occurrence would lead to such a [speculated] elongation of form?
A passing stalactite or stalagmite? I'd hate to see its mother planet! It suggests a degree of ruggedness on a scale rarely seen on Earth.

On Sunday, 3 December 2017 02:13:34 UTC-5, Chris.B wrote:
On Sunday, 3 December 2017 07:56:34 UTC+1, Quadibloc wrote:
On Saturday, December 2, 2017 at 8:49:51 PM UTC-7, Mike_Duffy wrote:
It just seems
strange to me that the very first time we ever see an object from outside
of our Solar System, is passes closer to the Sun than any object within our
Solar System.

The perihelion of 'Oomuamua is 0.25534 AU, which is indeed within the orbit of
Mercury (semi-major axis, 0.387 AU). However, the perihelion of Icarus is 0.1867
AU, so there are objects in our Solar System that pass closer to the Sun than it
did.

John Savard

Which natural occurrence would lead to such a [speculated] elongation of form?
A passing stalactite or stalagmite? I'd hate to see its mother planet! It suggests a degree of ruggedness on a scale rarely seen on Earth.

No reflection spectroscopy to say what it was made of?

RichA wrote:
On Sunday, 3 December 2017 02:13:34 UTC-5, Chris.B wrote:
On Sunday, 3 December 2017 07:56:34 UTC+1, Quadibloc wrote:
On Saturday, December 2, 2017 at 8:49:51 PM UTC-7, Mike_Duffy wrote:
It just seems
strange to me that the very first time we ever see an object from outside
of our Solar System, is passes closer to the Sun than any object within our
Solar System.

The perihelion of 'Oomuamua is 0.25534 AU, which is indeed within the orbit of
Mercury (semi-major axis, 0.387 AU). However, the perihelion of Icarus is 0.1867
AU, so there are objects in our Solar System that pass closer to the Sun than it
did.

John Savard

Which natural occurrence would lead to such a [speculated] elongation of form?
A passing stalactite or stalagmite? I'd hate to see its mother planet!
It suggests a degree of ruggedness on a scale rarely seen on Earth.

No reflection spectroscopy to say what it was made of?


From Wikipedia


Spectra recorded by the 4.2 m (14 ft) William Herschel Telescope on 25
October showed that the object was featureless, and colored red like Kuiper
belt objects.Spectra from the Hale Telescope showed a less-red color
resembling comet nuclei or Trojans.Its spectrum is similar to that of
D-type or P-type asteroids.

On Sat, 2 Dec 2017 22:56:31 -0800 (PST), Quadibloc wrote:

The perihelion of 'Oomuamua is 0.25534 AU, which is indeed within the orbit of
Mercury (semi-major axis, 0.387 AU). However, the perihelion of Icarus is 0.1867
AU, so there are objects in our Solar System that pass closer to the Sun

Thank you, I was not aware of any objects with a smaller perihelion than
Mercury.

My point re-phrased should thus have had something to do with an estimate
of the fraction of the known objects in the Solar System that have
perihelion less than 'Oomuamua.

I do understand that, for a given 'hyperbolic excess velocity', a smaller
course-change angle will be seen in objects with greater perihelion, and
thus are less likely to be observed. (Because they are further away from
our 'scopes).

I suppose it's 'suspicious' closeness to the sun really needs to be
compared to perihelia of other extra-System objects (i.e. the 'several'
estimated per year even though we have never seen any of them.) Otherwise,
I am generalizing on one unique event.

And as others have pointed out, what is REALLY suspicious is its shape. I
suppose we need to compare the shapes of all those 'several' other such
objects.

On Sunday, December 3, 2017 at 8:28:06 PM UTC-8, Mike_Duffy wrote:

... I was not aware of any objects with a smaller perihelion than
Mercury.

My point re-phrased should thus have had something to do with an estimate
of the fraction of the known objects in the Solar System that have
perihelion less than 'Oomuamua.

Well, Sun-grazing comets can come *very* close to the sun and survive, although many of them do not...

https://www.space.com/30315-sungrazi...fographic.html

https://en.wikipedia.org/wiki/C/2011_W3_(Lovejoy)

https://www.space.com/23780-comet-is...-roasting.html

On Sun, 3 Dec 2017 23:27:57 -0500, Mike_Duffy
wrote:
My point re-phrased should thus have had something to do with an
estimate
of the fraction of the known objects in the Solar System that have
perihelion less than 'Oomuamua.

It' s a small fraction but still a very large number. SOHO discovered
about a thousand sungrazing comets, some of which passed so close
that they
even collided with the Sun.

Nothing prevents an interstellar object to pass arbitrarily close to
the Sun. It's all a matter of probabilities. And even the improbable
does sometimes happen.

On Sun, 3 Dec 2017 23:27:57 -0500, Mike_Duffy
wrote:

My point re-phrased should thus have had something to do with an estimate
of the fraction of the known objects in the Solar System that have
perihelion less than 'Oomuamua.

Objects in the distant parts of the Solar System are continually being
perturbed in a way that increases the eccentricity of their orbits,
resulting in Sun-diving comets (and in some cases, asteroids) which
have perihelia well inside that of Mercury, sometimes even
intersecting the surface of the Sun.

I do understand that, for a given 'hyperbolic excess velocity', a smaller
course-change angle will be seen in objects with greater perihelion, and
thus are less likely to be observed. (Because they are further away from
our 'scopes).

Not sure what you mean by this. There is no course change with any
object orbiting the Sun, whether in a closed (elliptical) orbit or an
open (hyperbolic orbit). Whether we see these things are not is simply
a matter of chance. We can run the numbers based on different models
and conclude how many such objects exist, but we only see the ones we
see. It is virtually certain that we will soon start getting
observations that allow us to test our models, however, since there
are an increasing number of rapid survey telescopes coming on line,
meaning that essentially nothing over a certain size will escape our
observation.

I suppose it's 'suspicious' closeness to the sun really needs to be
compared to perihelia of other extra-System objects (i.e. the 'several'
estimated per year even though we have never seen any of them.) Otherwise,
I am generalizing on one unique event.

A comparison we won't be able to make until we start regularly
detecting extrasolar objects.

And as others have pointed out, what is REALLY suspicious is its shape. I
suppose we need to compare the shapes of all those 'several' other such
objects.

There's nothing "suspicious" about it. If accurate, it's simply
interesting. We know little about the shape of most small bodies in
the Solar System, and we know nothing about the history of this body.
Furthermore, the suggested shape isn't certain, it's just a conclusion
based on the varying brightness as the body rotates. That does not
produce a single solution. The proposed shape is statistically sound,
but far from certain.

On Mon, 04 Dec 2017 07:38:01 -0700, Chris L Peterson wrote:

Not sure what you mean by this. There is no course change

It was poor phrasing. What I called 'course change' is the angle between
the incoming & outgoing straight-line approximations of the hyperbola.