New discoveries

ALMA detects aluminum around newborn star

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Have you ever seen a shooting star? It looks like a star that falls down from the
heavens. In reality, it’s a grain of space dust that enters Earth’s atmosphere. Because
of collision with atmosphere, the dust particle evaporates and the air molecules start
to glow – that’s the streak of light you see.

Our solar system contains a lot of debris: space dust, small pebbles, larger meteorites
and huge space rocks known as asteroids. These are the leftovers from the birth of
planets like our own Earth.

Meteorites often contain aluminum – a shiny metal that is used in airplanes and
spacecraft because of its low weight. Apparently, when the solar system was born,
aluminum must have been quite abundant.

So you would expect that aluminum is also abundant in other newborn solar systems.
Indeed, ALMA has now detected the element for the very first time around a young
star.

ALMA did not find pure aluminum. Instead, it found aluminum oxide – a molecule that
consists of one aluminum atom and one oxygen atom. These molecules give off a very
specific kind of submillimeter radiation that ALMA can observe.

The radiation is only produced when the aluminum oxide is in the form of a hot gas.
Little wonder then that ALMA only saw the signal close to the star, where
temperatures are high.

However, further away from the star, the gas molecules are expected to condense into
solid particles. Thus, aluminum compounds can get incorporated into dust grains and
meteorites.

With the discovery of aluminum around a newborn star, astronomers hope to learn
more about the formation of meteorites – and eventually planets – in our own solar
system.

What?

Aluminum compounds have been found around a young star known as Kleinmann-Low Source I. This is a star in the constellation Orion that is still in the process of being born. It already weighs in at ten times the mass of our own sun, and it is still gobbling up new material. Together with other baby stars, Source I sits in the Orion Nebula – a huge star-forming region at a distance of some 1,500 light-years.

Who?

The ALMA observations of Kleinmann-Low Source I were carried out by a group of
Japanese astronomers, led by Shogo Tachibana of the University of Tokyo. The team
published their results on April 20, 2019, in The Astrophysical Journal Letters.

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