Image of the Month: Baby stars of NGC 2841

NGC 2841 is a rather beautiful flocculent spiral galaxy. The Hubble Space Telescope recently imaged NGC 2841 as part of an investigation into how new stars are created.

NGC 2841: a spiral galaxy some 46 million light years away. (Image credit: NASA/ESA)

How do stars form? It is a question which intrigues astronomers and it is a very important one too with implications for both cosmology and searches for exoplanets .  Star formation drives the evolution of galaxies and also we know that planetary systems form alongside their stars.

Despite its importance, stellar formation is still largely mysterious. We still do not know exactly what starts a molecular cloud collapsing to form a stellar nursery. It is especially hard to explain this process of star birth in some spiral galaxies. These are the flocculent spiral galaxies, identified by their fuzzy and clumpy spiral arms, in fact they look rather fluffy. (Astronomy is, of course, a very Serious Science, and it would undignified to speak of Fluffy Spiral Galaxies so the much more imposing term Flocculent is used instead.) Such flocculent spiral galaxies can be thought of as being at the other end of the scale from grand design spirals like the Andromeda or Whirlpool galaxies.

NGC 2841, subject of our Image of the Month, is a rather gorgeous flocculent spiral notable for its relatively low star formation rate compared to other spirals. It was imaged by the Hubble Space Telescope’s Wide Field Camera 3 (WFC3) as part of an on-going project to observe and compare contrasting star-forming regions. Targets include both star clusters and galaxies, and star formation rates seen range from the starburst galaxy M82 (the Cigar Galaxy) which is creating about ten new stars in its core alone every year to the much less fecund star producer NGC 2841.

The WFC3 is designed to observe both the ultraviolet radiation emitted in abundance by newborn stars and the infrared wavelengths which can penetrate the dusty veils common in star-forming regions. Regions full of new young (perhaps 100 million years old or less) stars show up as bright blue clumps in our image of the disc of NGC 2841. Yet despite young stars being fairly common, there are few sites of current star formation to be seen. It is very likely that the violent birthpangs of radiation from young stars disperses the very star-forming regions in which they were formed.

The bluish clumps of new stars in the image are broadly comparable to the Pleiades in our own galaxy. Born together, eventually the stars will be dispered by the shearing motion caused by the galaxy’s rotation around its centre, distributing them evenly through the galaxy’s disc.

NCC 2841 was discovered  230 years ago by William Herschel in the constellation Ursa Major. It is about 46 million light years (about 14 Mpc) away and it is about the same size as the Milky Way.