Baby stars in the Rosette Cloud

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A sweeping arc of warm dust marks the boundary between stars that have formed and power the Rosette Nebula, and stars that are still forming in the surrounding Rosette cloud. This Herschel image uses infrared light to reveal embedded stars up to 10 times the mass of our Sun busily forming inside dusty cocoons.

Working from the Royal Greenwich Observatory, England, the first Astronomer Royal, John Flamsteed, discovered a cluster of stars in 1690. We know that cluster as NGC 2244. Almost 150 years later, another English astronomer, John Herschel, discovered faint wisps of gas surrounding the stars. This is what we call the Rosette Nebula. Now the Herschel space observatory, named after John Herschel’s father, William, has revealed newly forming stars – protostars – in a previously invisible portion of the surrounding cloud.

This Herschel image shows most of the Rosette cloud, which resides 5000 light-years from Earth. The original star cluster lies to the right of the image but the stars are invisible at these wavelengths. The newly discovered stars are the bright points of white light scattered across the central portion of the image.

The bright smudges are dusty cocoons containing high-mass protostars. These will eventually become stars containing around 10 times the mass of the Sun. In the redder regions of the image and near its centre, are lower mass protostars, similar in mass to the Sun.

If our eyes could see faintly enough, the Rosette cloud would dominate the night sky, close to the famous constellation of Orion, the Hunter. In area, it would appear around five times larger than the full Moon. As it is, the light given out by this ring of celestial dust and gas is too feeble to be seen by anything other than Herschel.

Herschel collected the nebula’s infrared light given out by dust and this image is a three-colour composite made of wavelengths at 70 microns (blue), 160 microns (green) and 250 microns (red). It was put together using observations from Herschel’s Photoconductor Array Camera and Spectrometer (PACS) and the Spectral and Photometric Imaging Receiver (SPIRE). Each colour represents a different temperature of dust, from 10K in the red emission to 40K in the blue. Pillars of dust point towards the star cluster.

The picture shows the dusty component of the nebula. One percent of the mass in a giant molecular cloud is dust; the rest is gas. In total, the cloud contains enough dust and gas to make 10 000 Sun-like stars.

Credits: ESA/PACS & SPIRE Consortium, Frédérique Motte, Laboratoire AIM Paris-Saclay, CEA/IRFU - CNRS/INSU - Uni. Paris Diderot, HOBYS Key Programme Consortia

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