B First Interstellar Asteroid Found

[Ernest S Walton]

Look at the stars. Extragalactic stars exist, but are less common than stars in galaxies.

It is estimated that the current Solar System represents 2% of the mass of the original nebular cloud. The vast majority of asteroids are traveling through free space, not in orbit around a star.

 

[mfb]

... and most of them will still be in the galaxy. Their dynamics will be similar to the motion of stars.

Most of the initial mass of the gas cloud was hydrogen and helium, by the way, the fraction that stayed here doesn't tell you anything about solid objects.

 

[OmCheeto]

Yay!
For days I've been trying to figure out where this stick came from.
Fortunately, my Sol to Galactic coordinate transformation skills are nil, so I didn't even start on any calculations.
But it appears the smarties have been trying, and there seems to be a lot of head scratching going on:

NEWS
ASTRONOMY,PLANETARY SCIENCE
We still don’t know where the first interstellar asteroid came from
Clues from ‘Oumuamua’s speed and trajectory lead to answers all over the sky map
BY LISA GROSSMAN 11:38AM, DECEMBER 1, 2017​

So I don't feel so stupid.

 

[Al_]

Does it need a solar system to form an asteroid?

Not sure about the average asteroid. Maybe the definition matters here.
But this one, well, it's long and thin, so it is not formed by accretion. Which leaves collision. Two planets, or planetoids, or moons, or such an object and a pretty large asteroid collided. Now, maybe Oort cloud or interstellar objects sometimes collide, but interstellar space is so very huge that such collisions will be very rare. Far more likely to happen in the more crowded space a round a star. Hence, a solar system.

 

[Al_]

The object is not g-bound to Sol

Chasing it down with a rocket would require huge delta vee. But .. what about a rotating space tether? If we saw another one coming in, and had time to set it up, how long & strong would a tether have to be to have a tip velocity of say, 70km/sec? Is that even possible?

Erm, I answered my own question. Surprisingly, the max velocity does not increase with tether length. https://en.wikipedia.org/wiki/Space_tether#Practical_materials 2 or 3 km/sec is the best we can hope for.

 

[DrStupid]

Two planets, or planetoids, or moons, or such an object and a pretty large asteroid collided.

Yes, that's quite clear. But does the formation of such objects require a cloud with sufficient mass to form a star and not just planets? The paucity of small stars compared to the expected numbers (e.g. according to a Pareto distribution) suggests such a lower limit. But I didn't found corresponding sources.

 

[Al_]

Yes, that's quite clear. But does the formation of such objects require a cloud with sufficient mass to form a star and not just planets? The paucity of small stars compared to the expected numbers (e.g. according to a Pareto distribution) suggests such a lower limit. But I didn't found corresponding sources.

I see. Doh.
But, thinking about it, not unrelated is the question of how did it get up to 26km/sec? Was it due to the speed of the source objects relative to us as they dive toward a star, or just relative to us as they go their own way along between the stars? I suppose a star's involvement makes it more likely, and a big star more so? Look at it another way - if a cloud of dust formed a planet or two, without a star, why would a piece come flying at us so fast, unless the original cloud was going fast. Has it already done some flybys of stars, and completely lost all relation to it's cloud?

 

[snorkack]

I see. Doh.
But, thinking about it, not unrelated is the question of how did it get up to 26km/sec? Was it due to the speed of the source objects relative to us as they dive toward a star, or just relative to us as they go their own way along between the stars?

Relative to Sun. Which is moving at 20 km/s relative to local standard of rest.

What were the relative directions? What was the speed of Oumuamua relative to local standard of rest?

 

[DrStupid]

how did it get up to 26km/sec?

Speed is relative. It could ask how we got up so fast. Such a relative speed is not unusual in interstellar space.

 

[mfb]

20 km/s is a typical relative speed of stars. 26 km/s is nothing special.

But it appears the smarties have been trying, and there seems to be a lot of head scratching going on:

Well, there is a reasonable accuracy for the direction it came from, but finding a specific system is much harder as there is no obvious nearby star in that direction.

 

[CWatters]

Sorry if already mentioned but apparently oumuamua is getting faster...

https://www.standard.co.uk/news/int...leaving-nasa-scientists-baffled-a3875736.html

 

[stefan r]

Sorry if already mentioned but apparently oumuamua is getting faster...

https://www.standard.co.uk/news/int...leaving-nasa-scientists-baffled-a3875736.html

Did they report the delta-v?

 

[mfb]

He said: “This additional subtle force on ′Oumuamua likely is caused by jets of gaseous material expelled from its surface,”

“This same kind of outgassing affects the motion of many comets in our solar system.”

The original source

The observed accleration peaks at a few times 10^-6 m/s², or 30 m/s over one year. As its passage was faster, the total delta_v is smaller but an exact number needs an integral.

 

[DaveC426913]

It seems our little asteroid friend is actually a comet, venting gas.

 

[stefan r]

It seems our little asteroid friend is actually a comet, venting gas.

I thought you had to see the gas/dust in order for it to be called a comet. It should be called a "solar thermal rocket".

 

[rootone]

It just fired up the low tech impulse motors
the AI is now going to head to next the next interesting destination.
Only some curious white noise around the star Sol.

 

[at94official]

I had loads of fun this morning figuring out where the "25 km/s" number came from.
I think I did my maths correctly, as I came up with a figure of 25.7 km/sec.

Another number I came up with was, that if it was from Vega, it would have taken 580,000,000 years to travel that distance.
Though, as indicated by another of your simulations, Vega was probably nowhere near where it came from, that far back.
(Our galaxy looks like a busy airport when you look at it in 1000years/increment timescales. Freakin' stars flying everywhere!)

ps. Any idea who runs "projectpluto.com"? They seem to know what they are talking about:"Pseudo-MPEC" for A/2017 U1

[edit: millions of millions sounded too much like Sagan]

How did you figure all out of this? With my knowledge, solar systems move uniquely towards the center of our Galaxy, there's no way Vega is in there, from the direction of the Asteroid. Is it?

My knowledge in Astronomy is very little, I would love your direct and simple explanation.

Thanks,
Austin

 

[davenn]

With my knowledge, solar systems move uniquely towards the center of our Galaxy,

the solar system is orbiting the core of the Milky Way, as in the same ways the Earth orbits the Sun

 

[at94official]

the solar system is orbiting the core of the Milky Way, as in the same ways the Earth orbits the Sun

Right, and we can't go back from the same spot, ever. Right?

 

[davenn]

Right, and we can't go back from the same spot, ever. Right?

probably not exactly the same spot, but after one full orbit around the outer rim of the galaxy,
the solar system will be in a reasonably similar location ( one full orbit takes around 250 million years, from memory)

 

[SF cookie]

@ Austin:

No, the vast majority of solar systems orbit the centre of our galaxy in a roughly circular orbit. Very like our solar system's planets orbit around our sun.

There are plenty of solar systems which don't follow tidy 'more-or-less' circular orbits around the galactic center but they are thought to be systems whose galactic orbits can be explained by one of the following:

1) some previous gravitational interaction with another star or other massive object,
2) the star was part of a binary system whose partner went super-nova,
3) the star originated outside our galaxy and is a left-over part of an earlier galactic merger.

Sorry, but I can't do computional astronomy - I'm a C-minus at that sort of thing.

 

[OmCheeto]

How did you figure all out of this? With my knowledge, solar systems move uniquely towards the center of our Galaxy, there's no way Vega is in there, from the direction of the Asteroid. Is it?

My knowledge in Astronomy is very little, I would love your direct and simple explanation.

Thanks,
Austin

The comment; "Coming from the direction of Vega" was from the ProjectPluto website. My "figuring it out" was, um..., to google it.

"Pseudo-MPEC" for A/2017 U1

...Where did it come from?

... about five degrees away from the bright star Vega.​

 

[stefan r]

Right, and we can't go back from the same spot, ever. Right?

Depends on which reference frame you use. I remember seeing a full moon on the horizon on my way home from work. Suppose I see the full moon on the horizon again a month later. Would you say it is in "the same spot"? It is "on the horizon".

Ecliptic coordinate system
Celestial coordinate system
Cosmic microwave background

the object came from RA=18h 39m 14s, dec=+33 59' 50", with an uncertainty of about 2'

That is the Equatorial coordinate system

 

[rootone]

It is space time not just space.
The solar system and the galaxy as a whole cannot return to previous state.
No matter what your frame of reference is

 

[Tom.G]

Any idea who runs "projectpluto.com"?

A WHOIS lookup returns the name, address, phone #

 

[Hornbein]

I like the theory that 'Oumuamua is a crystal of hydrogen formed in interstellar space. It explains neatly some of its peculiar properties. This has been published in Astrophysical Journal.

Evidence that 1I/2017 U1 (‘Oumuamua) was composed of molecular hydrogen ice.