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A Birthplace like the Sun’s

The night sky has always been a kind of time machine, allowing us to look farther into the past the deeper we look into space. But the heavens are also a time machine in another sense — by looking carefully, we can find stellar systems in almost every stage of development. We recently saw an example in the Helix Nebula, an object that suggests what our Solar System may look like in five billion years, after the Sun has gone into its red giant phase and then collapsed into a white dwarf.

Now have a look at the Sun as it may have been five billion years in the other direction, back when it was coalescing out of its own primordial materials. The Pillars of Creation image taken by Hubble has become iconic, a majestic, breathtaking vista of a star-forming region in M16, the Eagle Nebula. Below, we see a Hubble image of the Pillars overlaid with Chandra X-ray Observatory data showing infant stars being born.

Note the bright x-ray sources, most of which are young stars. Much harder to see in the image is E42 (see the caption below for its location). It is an evaporating gas globule (EGG), one of 73 found in the Pillars of Creation region. Only four seem massive enough to form a star, and of these only E42 seems to have the mass of the Sun. All four of these proto-stars are thought to be the youngest ever identified by astronomers, according to Jeffrey Linsky (JILA, Boulder). And all are apparently too young to be emitting x-rays.

The Pillars of Creation

Image: The Chandra data show bright X-ray sources in this field, most of which are young stars. In this image, red, green, and blue represent low, medium, and high energy X-rays. The Chandra data have been overlaid on the Hubble Space Telescope image to show the context of these X-ray data. E42 is located in the left pillar on the right edge of a node jutting out to the right about two-thirds of the way down the pillar. Credit: X-ray: NASA/CXC/U.Colorado/Linsky et al.; Optical: NASA/ESA/STScI/ASU/J.Hester & P.Scowen.

The question to be asked now is whether E42 will ever grow up. 7000 light years away, the Pillars show evidence of a nearby supernova explosion, according to a French study. Says Linsky, “My guess is that the shock wave from the supernova may have been far enough away so that E42 and some of the other stars may have survived. But I guess we will have to wait another thousand years or so to get the answer.”

A supernova is likely the cause of the heavy elements in the gas that formed our Sun and Solar System. That would indicate that the Sun was born under conditions not so different from what we see in the Pillars of Creation, an environment rocked by shockwaves and permeated by ultraviolet radiation. Chemical abundances tell the tale and help us interpret the signs of an otherwise unrecoverable past.

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  • ljk April 9, 2008, 8:50

    Sequential star formation in a cometary globule (BRC37) of IC1396

    Authors: Hisashi Ikeda, Koji Sugitani, Makoto Watanabe, Naoya Fukuda, Motohide Tamura, Yasushi Nakajima, Andrew J. Pickles, Chie Nagashima, Takahiro Nagayama, Hidehiko Nakaya, Makoto Nakano, Tetsuya Nagata

    (Submitted on 8 Apr 2008)

    Abstract: We have carried out near-IR/optical observations to examine star formation toward a bright-rimmed cometary globule (BRC37) facing the exciting star(s) of an HII region (IC1396) containing an IRAS source, which is considered to be an intermediate-mass protostar. With slit-less spectroscopy we detected ten H_alpha emission stars around the globule, six of which are near the tip of the globule and are aligned along the direction to the exciting stars. There is evidence that this alignment was originally towards an O9.5 star, but has evolved to align towards a younger O6 star when that formed.

    Near-IR and optical photometry suggests that four of these six stars are low-mass young stellar objects (YSOs) with masses of ~0.4 M_sun. Their estimated ages of ~1 Myr indicate that they were formed at the tip in advance of the formation of the IRAS source. Therefore, it is likely that sequential star formation has been taking place along the direction from the exciting stars towards the IRAS source, due to the UV impact of the exciting star(s).

    Interestingly, one faint, H_alpha emission star, which is the closest to the exciting star(s), seems to be a young brown dwarf that was formed by the UV impact in advance of the formation of other YSOs at the tip.

    Comments: main text (30 pages) + online material, 14 figures, accepted for publication in AJ

    Subjects: Astrophysics (astro-ph)

    Cite as: arXiv:0804.1178v1 [astro-ph]

    Submission history

    From: Koji Sugitani [view email]

    [v1] Tue, 8 Apr 2008 04:48:22 GMT (487kb)

    http://arxiv.org/abs/0804.1178