NGC 5101 and NGC 5708: two spiral galaxies in Hydra

Image and text credit: Astronomy Picture of the Day Copyright: Martin Pugh

This sharp telescopic field of view holds two bright galaxies. Barred spiral NGC 5101 and nearly edge-on system NGC 5078 are separated on the sky by about 0.5 degrees or about the apparent width of a full moon. Found within the boundaries of the serpentine constellation Hydra, both are estimated to be around 90 million light-years away and similar in size to our own large Milky Way galaxy. In fact, if they both lie at the same distance their projected separation would be only 800,000 light-years or so. That’s easily less than half the distance between the Milky Way and the Andromeda Galaxy. NGC 5078 is interacting with a smaller companion galaxy, cataloged as IC 879, seen just below and left of the larger galaxy’s bright core. Even more distant background galaxies are scattered around the colorful field. Some are even visible right through the face-on disk of NGC 5101.

Update: Astronomers discover the oldest known star

A team led by astronomers at The Australian National University has discovered the oldest known star in the Universe, which formed shortly after the Big Bang 13.7 billion years ago. The discovery has allowed astronomers for the first time to study the chemistry of the first stars, giving scientists a clearer idea of what the Universe was like in its infancy. “This is the first time that we’ve been able to unambiguously say that we’ve found the chemical fingerprint of a first star,” said lead researcher, Dr Stefan Keller of the ANU Research School of Astronomy and Astrophysics.

The discovery has been published in Nature and the paper is S. C. Keller, et al., “A single low-energy, iron-poor supernova as the source of metals in the star SMSS J031300.36−670839.3,” Nature, 2014; doi:10.1038/nature12990. From the abstract:

Here we report the optical spectrum of SMSS J031300.36−670839.3, which shows no evidence of iron (with an upper limit of 10−7.1 times solar abundance). Based on a comparison of its abundance pattern with those of models, we conclude that the star was seeded with material from a single supernova with an original mass about 60 times that of the Sun (and that the supernova left behind a black hole). Taken together with the four previously mentioned low-metallicity stars, we conclude that low-energy supernovae were common in the early Universe, and that such supernovae yielded light-element enrichment with insignificant iron.


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