Astronomy Now Home
Home Magazine Resources Store

On Sale Now!



The September 2014 issue of Astronomy Now is on sale! Order direct from our store (free 1st class post & to UK addresses). The Astronomy Now iPad/iPhone editions are now available worldwide on the App Store.



Top Stories



Earthshine used to test life detection method
...By imagining the Earth as an exoplanet, scientists observing our planet's reflected light on the Moon with ESO's Very Large Telescope have demonstrated a way to detect life on other worlds...
  READ MORE

Solid buckyballs discovered in space
...Astronomers using NASA’s Spitzer Space Telescope have detected a particular type of molecule, given the nickname “buckyball”, in a solid form for the first time...
  READ MORE

Steamy water-world gets the Hubble treatment
...Hubble Space Telescope observations of a 7 Earth-mass planet find an unusual water-rich world swathed in a thick, steamy atmosphere...
  READ MORE








Most distant
galaxy cluster found

DR EMILY BALDWIN
ASTRONOMY NOW
Posted: 10 May 2010


Bookmark and Share

A team of astronomers have identified the most distant galaxy cluster yet using near-infrared spectroscopy, placing it at a distance of 9.6 billion light years.

Galaxy clusters are the largest gravitationally bound objects in the Universe, containing tens to thousands of galaxies. Clusters are thought to have begun assembling between ten billion years ago and now, so finding coherent galaxy groupings at such early epochs reveals important information about the formation and evolution of structure during the Universe's first few billion years.

This image of cluster SXDF-XCLJ0218-0510 measures 3.4 arcminutes on each side; the arrows indicate galaxies that are likely located at approximately the same distance. The cluster emits X-rays as shown by the contours, and the circles show galaxies whose distances are accurately measured from the near-infrared observations and have been confirmed to be at 9.6 billion light years away.

Previously, galaxy cluster XMMXCS J2215.9-1738, discovered by ESA's XMM-Newton space telescope in 2006 at 9.2 billion light years, held the distance record. Now, a team of astronomers from Japan and Germany – Masayuki Tanaka of the Institute for the Physics and Mathematics of the Universe (IPMU), Alexis Finoguenov of the Max Planck Institute for Extraterrestrial Physics, and Yoshihiro Ueda of Kyoto University have smashed this record using the Subaru telescope's MOIRCS (Multi-Object InfraRed Camera and Spectrograph)'s near-infrared capabilities to find a cluster at 9.6 billion light years.

“Though we confirmed only several massive galaxies at that distance, there is convincing evidence that the cluster is a real, gravitationally bound cluster,” says Tanaka.

Follow-up observations were made with the orbiting X-ray telescope XMM-Newton to detect hot gas in the cluster and confirm its 9.6 billion light year distance. Though the number of the confirmed members is small, the combination of the X-ray detection and infrared observations confirms that the cluster hosts predominantly old, massive galaxies, thus demonstrating that the galaxies formed when the Universe was still very young.

"The main result of our study is the exact measurement of the distance to a cluster using the absorption and emission features in the galaxy spectra," Finoguenov tells Astronomy Now. "This is a very expensive measurement, but is the one required to confidently derive the Doppler shifts and the corresponding distance to an object."

Last year came the report of another cluster – JKCS 041, read our news story here) – located at 10.2 billion light years distant, but Finoguenov comments that this distance may be unreliable because it is based on galaxy colours, known as a photometric redshift, while the new cluster has a distance determined by measurements of the shifts of well-defined spectral features.

JKCS 041 is 190 million light years across and may also be one of the Universe's most distant clusters. In this Chandra X-ray image, X-ray emission is shown in blue. Image: NASA/CXC/INAF/S.Andreon et al.

"Photometric redshift is a widely used and well established technique and requires less detailed data than spectroscopic redshifts, so it is very useful for faint, distant galaxies," explains Ben Maughan of the University of Bristol, part of the team reporting the results on JKCS 041 last year. "However, it is certainly a less reliable measurement than a spectroscopic redshift, which require significantly more detailed observations that are challenging for very distant galaxies."

Maughan tells Astronomy Now that the lead author of the research on JKCS 041, Stefano Andreon, has been performing follow up observations to attempt to confirm the photometric redshift spectroscopically. "In the interim between our work and this new release it has also been reported by another group that there is some evidence for multiple structures along the line of sight to JKCS 041, which could complicate the distance measurement for JKCS 041, and possibly mean our photometric measurement is incorrect."

Meanwhile, the German-Japanese team members are continuing their search for yet more distant clusters. "If we have a larger number of clusters at such a distance, we can say something about the mass/energy content of our Universe," says Tanaka. "We can also say how uniform the early Universe was. It was very close to uniform, but not totally – small deviations from the uniformity result in the rich cosmic large-scale structure today."

Regardless of which cluster is located the furthest, it is clear that both will provide new insight into the processes that dominated cluster formation in the early Universe.

"I'm very excited by the work being done to push deeper into the Universe in our studies of galaxy clusters, and the more objects like these we find, the better we'll be able to understand how they form and understand the information they hold about the evolution of the Universe," adds Maughan.

The Planets
From tiny Mercury to distant Neptune and Pluto, The Planets profiles each of the Solar System's members in depth, featuring the latest imagery from space missions. The tallest mountains, the deepest canyons, the strongest winds, raging atmospheric storms, terrain studded with craters and vast worlds of ice are just some of the sights you'll see on this 100-page tour of the planets.
 GET YOUR COPY

Hubble Reborn
Hubble Reborn takes the reader on a journey through the Universe with spectacular full-colour pictures of galaxies, nebulae, planets and stars as seen through Hubble's eyes, along the way telling the dramatic story of the space telescope, including interviews with key scientists and astronauts.
 GET YOUR COPY

3D Universe
Witness the most awesome sights of the Universe as they were meant to be seen in this 100-page extravaganza of planets, galaxies and star-scapes, all in 3D!
 GET YOUR COPY


HOME | NEWS ARCHIVE | MAGAZINE | SOLAR SYSTEM | SKY CHART | RESOURCES | STORE | SPACEFLIGHT NOW

© 2014 Pole Star Publications Ltd.