The IRAS galaxy

This protostar could tell us how stars grow up in space

Contributed by
Sep 20, 2016

Somewhere in the vast darkness of space, a flickering star almost looked like an astral corpse ready for its coffin—until it wasn’t.

Scientists now think that so-called casket should be a bike with training wheels, because what looked like a flicker of light on its last gasp is actually a protostar. Star IRAS 19312+1950 only looked like a dying sun from 12,000 light-years away until NASA put off writing its eulogy because the burning ball of gas is actually in its embryonic stage.   

The prepubescent celestial body might have appeared to be on its last gasp because its luminosity was easily confused with the type of glowing red giant better known as an Asymptotic Giant Branch (AGB) star. AGBs burn hydrogen like their final breath of it could be at any moment (technically, it could be). These slowly decomposing stars burn in helium and hydrogen around a lifeless carbon-oxygen core, depleting the fuel in their nearly empty nuclear gas tanks faster and faster until they end up running on fumes. With nothing left of its outer layers but swirling dust, an AGB will then start pulsing until it incinerates all but a shroud of hydrogen around the white dwarf that is now a ghost star.

IRAS 19312+1950 has proven it’s not dead yet (and probably won’t be for millions and even billions of years) by its behavior. Because a protostar is being powered by the galactic energy juice from the gas cloud that spawned it, it spews gas out of its poles faster than any highway speed limit—try upwards of 55 miles per second. Stars with one proverbial foot in the grave can only accelerate their gas jets to a fraction of that. While the ghostly hydrogen clouds around white dwarves keep expanding into the darkness, those around young stars tend to stay close to the nascent ball of flame. Protostars also outshine their ancient counterparts.

IRAS 19312+1950 protostar

What excites astronomers about the birthday party they almost thought was a funeral is what secrets this new find could hold about massive star formation. Stars that are smaller come into being by gathering their glow from a surrounding gaseous disc. Whether the same applies to massive stars remains a mystery. Even the ALMA observatory had issues with this question. The only other protostar we have been able to zero in on is in the Orion nebula, and while it may be in the Milky Way, it is often lost among a sea of stars. This is one case in which being a loner works to your advantage: IRAS is coming of age on its own.

“[The star’s isolation] could make it quite an important object for ongoing detailed studies of the star formation process,” observes Martin Cordiner of NASA’s Goddard Space Flight Center, who has also been leading the study on the new superstar protostar in Astrophysical Journal. “How do massive stars form? How do they pull in gas from their surroundings? How do they feed back radiation and energy to the surrounding environment? If you have a nice isolated object like this, you can study it more easily.”

Cordiner plans to launch a research mission on SOFIA, the world’s largest floating observatory, whose infrared vision specializes in (among many other phenomena) stellar births and deaths. Sounds worthy of a something-millionth—or billionth—birthday cake.