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The Most Distant Object in the Universe

By David Reneke

News from the space and astronomy communities around the world.

By combining the power of the Hubble Space Telescope, NASA’s Spitzer Space Telescope and one of nature’s zoom lenses, astronomers have found what is probably the most distant galaxy yet seen in the universe. This object offers a view of when the universe was only 3% of its present age of 13.7 billion years.

We actually see the newly discovered galaxy, named MACS0647-JD, as it was 420 million years after the Big Bang. Its light has travelled for 13.3 billion years to reach Earth, which corresponds to a massive redshift of approximately 11.

Redshift is a direct consequence of the expansion of space over cosmic time, stretching the wavelength of light and thus making a distant object appear redder than it really is. Objects with a higher redshift have had their light stretched more, and are therefore more distant from us.

The find is the latest discovery from the Cluster Lensing And Supernova Survey with Hubble (CLASH), which uses massive galaxy clusters as cosmic telescopes to magnify distant galaxies behind them. Astronomers call the effect gravitational lensing.

“This has outstripped even my expectations of what would be possible with the CLASH program,” said Rychard Bouwens, co-author of the study. “The science output in this regard has been incredible.”

About eight billion years into its journey, the galaxy’s light took a detour along multiple paths around a massive galaxy cluster. Due to gravitational lensing, the team observed three magnified images of MACS0647-JD with Hubble. The cluster’s gravity boosted the faraway galaxy’s light, making the images appear far brighter than it otherwise would be.

This cluster does what no man-made telescope can do. Without the magnification it would require a Herculean effort to observe this galaxy as the object is so small, maybe 600 light years across, and possibly in the first stages of galaxy formation. For comparison, the Milky Way is 100,000 light years across.

The estimated mass of this baby galaxy is roughly equal to

100 million or a billion suns. “This object may be one of many building blocks of a galaxy,” explained Dan Coe of the Space Telescope Science Institute and lead author of the study.

The team concluded that this fledgling galaxy is the new distance record holder. It will almost certainly be a prime target for the James Webb Space Telescope, scheduled for launch in 2018, which will be able to conduct spectroscopy to make a definitive measurement of its distance and study its properties in more detail.

Born-Again Star Foreshadows Our Fate

Astronomers have found evidence for a dying Sun-like star coming briefly back to life after casting its gaseous shells into space. It gives a preview of our own solar system in a few billion years.

This new picture of the planetary nebula Abell 30, which is 5500 light years from Earth, is a composite of visible images from the Hubble Space Telescope and X-ray data from ESA’s XMM-Newton and NASA’s Chandra space telescopes.

“Planetary nebula” is the name given to the billowing shells of stellar material cast into space by dying stars. To 18th century astronomers, these objects looked like the colourful “blob” of a planet through their telescopes, and the name stuck. Astronomers now know that stars with less than eight times the mass of the Sun swell into red giants towards the end of their lives.

Their outer layers are expelled via pulsations and winds producing radiation that then illuminates the ejected shells, resulting in intricate artworks that can be seen by modern telescopes.

The star at the heart of Abell 30 experienced its first brush with death 12,500 years ago, as seen from Earth, when its outer shell was stripped off by a slow and dense stellar wind. Optical telescopes see the remnant of this evolutionary stage as a large, near-spherical shell of glowing material expanding out into space.

About 850 years ago the star inexplicably came back to life, violently coughing out knots of helium and rich carbon material. The star’s outer envelope briefly expanded during this period of rebirth, but very rapidly contracted again – probably within 20 years.

This knock-on effect accelerated the wind from the star to its present speed of more than 14 million km/h. As this fast stellar wind catches the slower stream, complex structures are formed, including the delicate cometary tails seen near the central star.

It provides a chilling look at the possible fate of Earth and its fellow planets in our own solar system in a few billion years’ time. It’s inevitable and a fairly common occurrence from what we can observe.

When our Sun emits its final gasps of life at the heart of a planetary nebula, its strong stellar wind and harsh radiation will blast and obliterate any planets that may have survived the red giant phase of stellar evolution. If any distant civilisation is watching with high powerful telescopes at the time they might see the glowing embers of the planets, including Earth, light up in X-rays as they are engulfed in the stellar wind.

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