#interstellar objects

Image: NASA, ESA, David Jewitt (UCLA); Image Processing: Joseph DePasquale (STScI)

The True Nature of Oumaumua

On October 19th 2017, the Pan-STARRS1 observatory in Hawaii detected what is believed to be the very first interstellar object, some 40 days after it had already passed it's closest point to Earth.

The object sparked a lot of coverage, and due to a number of unexplained behaviours, some even suggested it was an alien ship.

Firstly while it behaved like a comet, it's shape was nothing like the comets we experience in our solar system, rather than round, it was flat. Secondly, as it approached the Sun, it didn't generate a notable tale, the lack of gaseous outflow was most unlike your average comet. In addition to this, it's movement was peculiar, it appeared to gain more thrust from it's pass near the sun than could be accounted for by it's supposed mass.

Two Arizona State University astrophysicists, Steven Desch and Alan Jackson of the School of Earth and Space Exploration believe they have found an explanation to all the issues without reaching for the "aliens".

Instead, Desch and Jackson proposed something a little more akin to a bit of Pluto, although hailing from another star system.

The proposed theory is, that sometime around 400 million years ago a comet smashed into a Pluto like body, with a surface crust of Nitrogen which was hurled into space and out of the star system.

Fast forward to 2017, it reached our solar system, having been eroded by almost half a billion years of interstellar charged particles, and now more like a flat pebble than a rounded mass.

The fact it's nitrogen can account for the mistake in calculating it's mass, the reflective properties were greater than assumed, and therefore the mass was smaller, which explains too the odd speed gain from the Sun as it passed through. The nitrogen theory also explains the lack of tail.

So, sorry Ancient Aliens dude ..

NITROGEN !

seems at least the more logical explanation.

Scientists know of 750,000 or so asteroids and comets — and all of them are part of this fine solar system.  That is, all of them but one.  And as new research shows, it’s weird as hell.

Today [2017/11/20], scientists are reporting their analysis of ‘Oumuamua, an interstellar object spotted last month.  The oddly-shaped, fast-moving rock immediately surprised astronomers with its chemical makeup and other properties, which implied there should be far more interstellar objects floating around than previously thought.

“The presence of ‘Oumuamua suggests that previous estimates of the density of interstellar objects were pessimistically low,” the authors write in the study published today in the journal Nature.

‘Oumuamua’s story begins on October 19, 2017 when the Hawaiian Pan-STARRS1 telescope system spotted it.  Scientists named it A/2017 U1, but immediately realized that they were looking at something strange, since its orbit’s shape was extremely hyperbolic.  That means rather than orbiting the Sun, this thing came and went with enough speed to “clearly” imply it was from outside the solar system.

The brief visit made the planet difficult to name — the minor planet designation scheme doesn’t allow for naming something only seen once.  Researchers created a new classification for these interstellar objects, and gave it a Hawaiian name that “reflects the way this object is like a scout or messenger sent from the distant past to reach out to us,” according to a Minor Planet Center communication.  Pronounced “Oh-moo-ah-moo-ah,” it means “a messenger from afar arriving first.”

Observations of the wildly-varying light from ‘Oumuamua showed scientists it wasn’t spherical, but probably had a cigar shape measuring 800 meters by 80 meters by 80 meters — that’s something almost as tall as the Statue of Liberty, but half a mile long.  It’s red, and likely made from metal and carbon-rich matter like some comets.  Scientists also observed that it didn’t have a fuzzy, comet-like appearance, which is surprising given the fact that most observed rocks originating from the distant Oort cloud are comets.

This set up a conundrum: Scientists assumed interstellar objects would behave more like comets than asteroids until ‘Oumuamua came along.  If they’re more like asteroids, that implied to the team that there are way more of these interstellar rocks in the Solar System than originally thought, according to the paper.  It also adds another factor when considering Earth impacts.  “Impact from an interstellar object would be far more energetic than from a solar system object with similar mass, due to the larger impact speed,” the authors write.

As far as where it came from — no one knows yet.  The paper suggests a nearby debris disk, or that its trajectory was changed by some planet or other comet — maybe it was set off by the undiscovered Planet Nine.  All that is informed speculation, of course.

Scientists will never get to see ‘Oumuamua again as it speeds off — but it brief visit suggests might not be the last time scientists spot something like this.

[Nature]

I feel the sudden urge to read Arthur C. Clarke’s Rendezvous with Rama.  Or re-read Greg Bear’s Eon.

As stars form, planets form around them from the left overs, but stars don’t sit still, they move around the galaxy, and as they do, they come close to other stars, sometimes very close, and when gravitational forces get involved, some planets get ejected out of their birth system into interstellar space. 

"All in all, the mass of #3I_ATLAS is of order a billion metric tons!...Despite systematic uncertainties, the magnitude of the #nongravitationalacceleration can be estimated quite robustly...the bounds for a model which only includes CO2-sublimation is compatible with the non-gravitational estimates of the nucleus size...one conclusion is beyond any reasonable doubt: the third interstellar object 3I/ATLAS is at least 5 orders of magnitude more massive than the first interstellar object #1I_Oumuamua...we should have detected at least a hundred thousand 1I/Oumuamua-mass objects before discovering a single interstellar object with the #mass of 3I/ATLAS...Does this discrepancy mean that one or both of these two mysterious #interstellarobjects is not natural in origin?"

#artifact?

There's only been three interstellar objects officially discovered. Ever.

The study of interstellar objects only started in 2017. This is a brand new field!