Baby star blows gas into space at two different speeds
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If you topple a bottle of water, the liquid flows out very fast. But turn over a container of treacle, and it takes ages to empty. So what could be going on if you see a fast and a slow flow at the same time?
Astronomers faced a similar question when they studied a newborn star. Baby stars often blow material into space, in two opposite directions. Usually, these so-called jets have one single velocity, depending on how exactly they are produced. But in the case of MMS5/OMC-3, something weird is going on.
Observations with ALMA reveal that this baby star produces both high-velocity jets and much slower outflows, as if it is spilling water and treacle at the same time. And no one knows why or how.
Of course, stars don’t spew out water and treacle. Both the fast jets and the slow outflows of MMS5/OMC-3 consist of gas. Originally, the gas whirled around the baby star in a flat, spinning disk. Somehow – probably because of magnetic fields – part of the gas is blown into space, at right angles to the disk.
The ALMA observations show that the fast jets were launched less than 500 years ago. The slower outflows are older – some 1,300 years. Moreover, the slower material is ejected in a slightly different direction from the fast-moving gas.
So how can one star produce gas flows at two different velocities? Astronomers think that they form in different parts of the disk. The fast jets would form in the inner parts of the disk, close to the star. The slow outflows would form further away, in the outer parts of the disk. If the disk is warped like a Pringle, this could also explain why the slow outflows and the fast jets are misaligned.
Astronomers are very eager to learn more about the jets and outflows of baby stars. By studying objects like MMS5/OMC-3, they hope to learn more about the way stars are born.
What?
MMS5/OMC-3 is a so-called protostar – a star still in the process of being born. It is located in a giant stellar nursery, the Orion Molecular Cloud (that’s what the letters OMC stand for). The astronomers studied the millimeter-wave radiation of carbon monoxide – one of the constituents of the outflowing gas. They found that the fast jets have velocities between 50 and 100 kilometers per second. They extend out to a distance of 1.65 trillion kilometers. The slower outflows move at between 10 and 50 kilometers per second. However, since they were produced much longer ago, they now extend out to over 2 trillion kilometers.
Who?
The ALMA observations of MMS5/OMC-3 were carried out by a small team of Japanese astronomers, led by Yuko Matsushita. Yuko is a graduate student in astronomy at Kyushu University in Fukuoka. She worked together with her supervisor, Masahiro Machida, and with Satoko Takahashi and Kohji Tomisaka. The results of the research have been published in The Astrophysical Journal.
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