Cosmic beacon flashes out from infant stars

From across the light-years a cosmic beacon beams out from an infant star system.

The fan-like pattern to the right of the image (about one-third of the way across and two-thirds of the way down) pulses with light on a 25.34 day cycle – as regularly as … the rising of the sun. And indeed, an underlying orbital motion may be the cause.

Astronomers have been using the NASA/ESA Hubble Space Telescope to unravel the structure that lies beneath the cloud of dust and gas. They believe that two protostars are circling each other, each at the stage when they are pulling in lots of gas and dust and glowing bright with the resulting heat.

The energy being turned into heat is coming from the gravitational squeeze – the nuclear fires will only come later. The two stars are estimated to be no more than a few hundred thousand years old.

Each of the stars is moving in an elliptical orbit through space, swinging apart and the then swinging back to make a close pass of each other every 25.34 days. Here is a diagram of it.


The right-hand image shows the orbit of each, and how the two orbits interlock.

As they move towards their point of closest encounter, when their combined gravitational influence is at its strongest, they pull in a big mass of material from the surrounding cloud of gas and dust. When the cloud crashes onto the sizzling hot surface of each a huge burst of radiation is unleashed.

The centre diagram shows what we see from the outside, and you can follow the sequence through the cycle on a video that they prepared out of the various images taken over a period of a month of so.

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What we see in these images is the light that gets through the cloud of gas and dust obscuring the underlying two-star system.

The fan-shaped pattern is believed to come about through the forming of two cavities in the cloud. It’s thought that these cavities may be formed by an outflow from near the two-star star system; the outflow will blow away dust and gas out of the envelope that surrounds the star system.

This binary system, called LRLL 54361, was discovered by NASA’s Spitzer Space Telescope inside the star-forming region known as IC 348. This is around 950 light-years away from us and situated inside the constellation Perseus. IC 348 has several hundred stars in it, about half of which have a disc of gas and dust around them. Here is one of the Spitzer images of the region.

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