Space rock may be a unique vis­i­tor

Sunday Star-Times - - World -

A mys­te­ri­ous ob­ject de­tected hurtling past the Sun could be the first space rock traced back to a dif­fer­ent so­lar sys­tem, ac­cord­ing to astronomers track­ing it.

While other ob­jects have pre­vi­ously been mooted as hav­ing in­ter­stel­lar ori­gins, ex­perts say the lat­est find, an ob­ject es­ti­mated to be less than 400 me­tres in di­am­e­ter, is the best con­tender yet.

‘‘The ex­cit­ing thing about this is that this may be es­sen­tially a vis­i­tor from an­other star sys­tem,’’ said Dr Ed­ward Bloomer, astronomer at the Royal Ob­ser­va­tory Green­wich.

If its ori­gins are con­firmed as ly­ing beyond our so­lar sys­tem, it will be the first space rock known to have come from else­where in the galaxy.

Ob­ser­va­tions pub­lished by the Mi­nor Planet Cen­tre at the Har­vard-Smith­so­nian Cen­tre for Astro­physics re­veal that the ob­ject is in a strong hy­per­bolic or­bit – in other words, it is go­ing fast enough to es­cape the grav­i­ta­tional pull of the Sun.

Ob­jects orig­i­nat­ing from, and on long-pe­riod or­bits within, our so­lar sys­tem can end up on a hy­per­bolic tra­jec­tory, and be ejected into in­ter­stel­lar space – for ex­am­ple, if they swing close by a gi­ant planet, since the planet’s grav­ity can cause ob­jects to ac­cel­er­ate. But Dr Gareth Wil­liams, as­so­ciate di­rec­tor of the Mi­nor Planet Cen­tre, said this wasn’t the case for the newly dis­cov­ered body.

‘‘When we run the or­bit for this [ob­ject] back in time, it stays hy­per­bolic all the way out – there are no close ap­proaches to any of the gi­ant plan­ets that could have given this thing a kick,’’ he said. ‘‘If we fol­low the or­bit out into the fu­ture, it stays hy­per­bolic. So it is com­ing from in­ter­stel­lar space and it is go­ing to in­ter­stel­lar space.’’

Ac­cord­ing to ob­ser­va­tions made by astronomers, the ob­ject en­tered our so­lar sys­tem from above, pass­ing just in­side Mer­cury’s or­bit and trav­el­ling be­low the Sun, be­fore turn­ing and head­ing back up through the plane of the so­lar sys­tem to­wards the stars beyond. At its clos­est, on Septem­ber 9, the ob­ject was 37.6 mil­lion kilo­me­tres from the Sun.

The ob­ject was first spot­ted ear­lier this month by an ob­ser­va­tory in Hawaii, and astronomers around the world are now fol­low­ing its path.


The as­ter­oid dubbed A/2017 U1, seen in this artist’s im­pres­sion, is thought to have drifted into our so­lar sys­tem from else­where in the galaxy.

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