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Rare Rectangular Galaxy Found

By David Reneke

News from the space and astronomy communities around the world.

An international team of astronomers from Australia, Germany, Switzerland and Finland has discovered a rare rectangular-shaped galaxy that has a striking resemblance to an emerald-cut diamond. Astronomers don’t have fancy names for most objects they find – they’ve simply labelled this one with the catalogue number LEDA 074886.

While using the Subaru Prime Focus Camera to look for globular clusters of stars swarming around NGC 1407 – a bright, giant galaxy in the constellation Eridanus 70 million light years from Earth – the researchers discovered an unusually shaped dwarf galaxy toward the edge of their image.

Prof Alister Graham of Swinburne University, the lead author of the paper describing the research, said: “It’s one of those things that just makes you smile because it shouldn’t exist, or rather, you don’t expect it to exist”. Its discovery allows astronomers to obtain useful information for modelling other galaxies.

Most galaxies in the universe around us exist in one of three forms: ellipsoidal, disc-like or irregular. Dwarf galaxies, probably the most common galaxies in the universe, are small and have low luminosities.

One of the reasons that LEDA 074886 was hard to find is its dwarf-like status . It has 50 times less stars than our own Milky Way galaxy, and its distance from Earth is equivalent to 700 Milky Way galaxies placed end to end.

The combined advantages of Subaru’s large 8.2-metre primary mirror and its camera at prime focus gave the researchers such a wide field of view that they could observe objects beyond their intended targets and make the surprising discovery of the emerald-shaped dwarf galaxy.

The astronomers suspect that the emerald-cut galaxy may resemble an inflated disc when seen side-on. “One possibility is that the galaxy may have formed out of the collision of two spiral galaxies,” explained co-author Professor Duncan Forbes of Swinburne University.

From all this, astronomers have gained useful information for modelling other galaxies. While the outer rectangular shape is somewhat like galaxy simulations that don’t involve the production of new stars, the disc-like structure is comparable with simulations involving star formation. “This highlights the importance of combining lessons learned from both types of past simulations,” Graham says.

When our own Milky Way galaxy collides with the disc-shaped Andromeda Galaxy in about three billion years from now, we may become inhabitants of a rectangular-looking galaxy ourselves, and get written up in a magazine just like this one!

Nomadic Planets Rule!
Our galaxy may be awash in homeless planets wandering through space instead of orbiting a parent star. In fact, there may be 100,000 times more of these “nomad planets” in the Milky Way than stars, according to a new study by researchers at the Kavli Institute for Particle Astrophysics and Cosmology in California.

If observations confirm the estimate, this new class of celestial objects will affect current theories of planet formation and could change our understanding of the origin and abundance of life. “If any of these nomad planets are big enough to have a thick atmosphere, they could have trapped enough heat for bacterial life to exist,” said Louis Strigari, leader of the team that reported the results.

Searches over the past two decades have identified more than 600 planets outside our solar system, almost all of which orbit stars. Last year, researchers detected about a dozen nomad planets using a technique called gravitational microlensing, which looks for stars whose light is momentarily refocused by the gravity of passing planets.

The research produced evidence that roughly two nomads exist for every typical main sequence star in our galaxy. The new study estimates that nomads may be up to 50,000 times more common than that!

To arrive at their findings the team took into account the known gravitational pull of the Milky Way galaxy, the amount of matter available to make such objects and how that matter might divvy itself up into objects ranging from the size of Pluto to larger than Jupiter.

This was not an easy task. Some were probably ejected from solar systems, but research indicates that not all of them could have formed in that fashion.

“To paraphrase Dorothy from The Wizard of Oz, if correct, this extrapolation implies that we are not in Kansas anymore, and in fact we never were in Kansas,” said Alan Boss of the Carnegie Institution for Science. “The universe is riddled with unseen planetary mass objects that we are just now able to detect.”

A good count, especially of the smaller objects, will have to wait for the next generation of big survey telescopes in the early 2020s.

Few areas of science have excited as much popular and professional interest in recent times as the prevalence of life in the universe. A confirmation that nomad planets roam their starry pastures and cause collisions could indicate that they scatter their microbial flocks to seed life elsewhere.

David Reneke is an astronomy lecturer and teacher, a feature writer for major Australian newspapers and magazines, and a science correspondent for ABC and commercial radio. Subscribe to David’s free Astro-Space newsletter at www.davidreneke.com