Opening up a colorful cosmic jewel box

Oct 29, 2009
The FORS1 instrument on the ESO Very Large Telescope (VLT) at ESO's Paranal Observatory was used to take this exquisitely sharp close up view of the colorful Jewel Box cluster, NGC 4755. The telescope's huge mirror allowed very short exposure times: just 2.6 seconds through a blue filter (B), 1.3 seconds through a yellow/green filter (V) and 1.3 seconds through a red filter (R). The field of view spans about seven arcminutes. Credit: ESO/Y. Beletsky

(PhysOrg.com) -- Star clusters are among the most visually alluring and astrophysically fascinating objects in the sky. One of the most spectacular nestles deep in the southern skies near the Southern Cross in the constellation of Crux.

The Kappa Crucis Cluster, also known as NGC 4755 or simply the "Jewel Box" is just bright enough to be seen with the unaided eye. It was given its nickname by the English astronomer John Herschel in the 1830s because the striking colour contrasts of its pale blue and orange stars seen through a telescope reminded Herschel of a piece of exotic jewellery.

Open clusters such as NGC 4755 typically contain anything from a few to thousands of stars that are loosely bound together by gravity. Because the stars all formed together from the same cloud of gas and dust their ages and are similar, which makes them ideal laboratories for studying how stars evolve.

The position of the cluster amongst the rich star fields and dust clouds of the southern Milky Way is shown in the very wide field view generated from the Digitized Sky Survey 2 data. This image also includes one of the stars of the Southern Cross as well as part of the huge dark cloud of the Coal Sack.

A new image taken with the Wide Field Imager (WFI) on the MPG/ESO 2.2-metre telescope at ESO's in Chile shows the cluster and its rich surroundings in all their multicoloured glory. The large field of view of the WFI shows a vast number of stars. Many are located behind the dusty clouds of the Milky Way and therefore appear red.

This composite image serves as a still “zoom-in”, showing the rich star field in which NGC 4755 nestles and then moving in to the detailed Hubble image of the Kappa Crucis Cluster, or Jewel Box, itself. The range of images begins with a very wide-field view of the sky surrounding NGC 4755. The images then progressively “zoom in” to reveal a “close-up” of the Jewel Box, featuring several very bright, pale blue supergiant stars, a solitary ruby-red supergiant and a variety of other brilliantly coloured stars. The picture on the top left was taken from the ground with a 35-mm camera. The next image is from the Digitized Sky Survey 2, a large digital atlas of the sky. Next is a very sharp image from the FORS1 instrument on the ESO Very Large Telescope at ESO’s Paranal Observatory. The first image (left) on the bottom row was taken by the Wide Field Imager (WFI) on the MPG/ESO 2.2-metre telescope at ESO’s La Silla Observatory. The last image (at bottom right) is the one taken by the legendary (and now retired) WFPC2 aboard Hubble.

The FORS1 instrument on the ESO Very Large Telescope (VLT) allows a much closer look at the cluster itself. The telescope's huge mirror and exquisite image quality have resulted in a brand-new, very sharp view despite a total exposure time of just 5 seconds. This new image is one of the best ever taken of this cluster from the ground.

The Jewel Box may be visually colourful in images taken on Earth, but observing from space allows the NASA/ESA Hubble Space Telescope to capture light of shorter wavelengths than can not be seen by telescopes on the ground. This new Hubble image of the core of the cluster represents the first comprehensive far ultraviolet to near-infrared image of an open galactic cluster. It was created from images taken through seven filters, allowing viewers to see details never seen before. It was taken near the end of the long life of the Wide Field Planetary Camera 2 ― Hubble's workhorse camera up until the recent Servicing Mission, when it was removed and brought back to Earth. Several very bright, pale blue supergiant stars, a solitary ruby-red supergiant and a variety of other brilliantly coloured stars are visible in the Hubble image, as well as many much fainter ones. The intriguing colours of many of the stars result from their differing intensities at different ultraviolet wavelengths.

The huge variety in brightness of the stars in the cluster exists because the brighter stars are 15 to 20 times the mass of the Sun, while the dimmest stars in the Hubble image are less than half the mass of the Sun. More massive stars shine much more brilliantly. They also age faster and make the transition to giant much more quickly than their faint, less-massive siblings.

The Jewel Box cluster is about 6400 light-years away and is approximately 16 million years old.

Source: ESO (news : web)

Explore further: Image: Chandra's view of the Tycho Supernova remnant

add to favorites email to friend print save as pdf

Related Stories

A sparkling spray of stars

Dec 16, 2008

NGC 2264 lies about 2600 light-years from Earth in the obscure constellation of Monoceros, the Unicorn, not far from the more familiar figure of Orion, the Hunter. The image shows a region of space about 30 ...

An Eagle of Cosmic Proportions

Jul 16, 2009

(PhysOrg.com) -- Today ESO has released a new and stunning image of the sky around the Eagle Nebula, a stellar nursery where infant star clusters carve out monster columns of dust and gas.

Recommended for you

Image: Chandra's view of the Tycho Supernova remnant

9 hours ago

More than four centuries after Danish astronomer Tycho Brahe first observed the supernova that bears his name, the supernova remnant it created is now a bright source of X-rays. The supersonic expansion of ...

Satellite galaxies put astronomers in a spin

Jul 24, 2014

An international team of researchers, led by astronomers at the Observatoire Astronomique de Strasbourg (CNRS/Université de Strasbourg), has studied 380 galaxies and shown that their small satellite galaxies almost always ...

Video: The diversity of habitable zones and the planets

Jul 24, 2014

The field of exoplanets has rapidly expanded from the exclusivity of exoplanet detection to include exoplanet characterization. A key step towards this characterization is the determination of which planets occupy the Habitable ...

User comments : 1

Adjust slider to filter visible comments by rank

Display comments: newest first

yyz
not rated yet Oct 30, 2009
Check out the link to the ESO press release, as it has much wider array of pics available, including the HST image shown in the mosaic above.