Astronomically speaking, it’s tough to beat the
discovery of a comet or asteroid from another solar system, as all of
the hubbub over ‘Oumuamua
has proven. However, this just might do it. Astronomers studying the
chemical compositions of stars in our Milky Way Galaxy have discovered a
star in the Big Dipper with a combination of elements that exists
nowhere else in the galaxy. An invader? Interloper? Can we charge it
rent?
“Here we report on the discovery of a metal-poor star
with an extreme r-process enhancement and α-element deficiency. In this
star, the abundance ratio of the r-process element Eu with respect to Fe
is more than one order of magnitude larger than the Sun and the
metallicity is 1/20 of solar metallicity.”
That’s astronomer-speak for “Hey! Put down your beer and come look at this!” According to the press release for a new study published in the journal Nature Astronomy,
a group of astronomers from China and Japan using the Large Sky Area
Multi-Object Fiber Spectroscopic Telescope (LAMOST) in Xinglong Station,
Hebei Province, China, discovered a star, now named J1124+4535, just
below the bowl of the Big Dipper, also known as the Ursa Major
constellation, with an unusual chemical signature. Specifically, it has a
very low level of elements such as magnesium compared with an
excessively high level of Europium, a soft metal similar to lead. That
high-low ratio is not found in the Milky Way but matched the chemical
composition of stars in dwarf galaxies orbiting our own.
So, how did J1124+4535 end up in the Big Dipper? It’s believed that
there were once many more dwarf galaxies orbiting the Milky Way, but our
greedy galaxy likes to gorge on them and absorbed them completely –
destroying their identities and assimilating them into its own. Somehow,
J1124+4535 managed to survive. As we found with interstellar asteroids,
if there’s one, there’s probably more, and that’s already the case with
this prisoner from another galaxy. Astronomers have discovered
non-Milky Way hypervelocity stars speeding through after being spun off
by those orbiting dwarf galaxies, particularly the Large Magellanic
Cloud. However, J1124+4535 seems to be the only one so far to arrive via
complete absorption.
Speaking of the Large Magellanic Cloud, it’s scheduled to be absorbed
via collision in about 2 billion years, followed by the Andromeda
Galaxy in another 2 to 3 billion years.
In space, no one can hear you scream, but someone in the future may hear the Milky Way chew, swallow and belch.
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