Star cluster NGC 3590, in the wake of Carina

This colourful new image from the MPG/ESO 2.2-meter telescope at ESO's La Silla Observatory in Chile shows the star cluster NGC 3590. 

These stars shine brightly in front of a dramatic landscape of dark patches of dust and richly hued clouds of glowing gas. 

This small stellar gathering gives astronomers clues about how these stars form and evolve, as well as giving hints about the structure of our galaxy's pinwheeling arms. Credit: ESO/G. Beccari

This colorful new image from the MPG/ESO 2.2-meter telescope at ESO's La Silla Observatory in Chile shows the star cluster NGC 3590.

These stars shine brightly in front of a dramatic landscape of dark patches of dust and richly hued clouds of glowing gas.

This small stellar gathering gives astronomers clues about how these stars form and evolve—as well as giving hints about the structure of our galaxy's pinwheeling arms.

NGC 3590 is a small open cluster of stars around 7500 light-years from Earth, in the constellation of Carina (The Keel).

It is a gathering of dozens of stars loosely bound together by gravity and is roughly 35 million years old.

This cluster is not just pretty; it is very useful to astronomers. By studying this particular cluster, and others nearby, astronomers can explore the properties of the spiral disc of our galaxy, the Milky Way.

NGC 3590 is located in the largest single segment of a spiral arm that can be seen from our position in the galaxy: the Carina spiral feature.

The Milky Way has multiple spiral arms, long curved streams of gas and stars stretching out from the galactic centre.

These arms—two major star-filled arms, and two less populated minor arms—are each named after the constellations in which they are most prominent.

The Carina spiral feature is seen from Earth as a patch of sky heavily populated with stars, in the Carina-Sagittarius minor arm.

The name of this arm, Carina, or The Keel, is quite appropriate.

These spiral arms are actually waves of piled up gas and stars sweeping through the galactic disc, triggering sparkling bursts of star formation and leaving clusters like NGC 3590 in their wake.

By finding and observing young stars like those in NGC 3590, it is possible to determine the distances to the different parts of this spiral arm, telling us more about its structure.

Typical open clusters can contain anything from a few tens to a few thousands of stars, and provide astronomers with clues about stellar evolution.

The stars in a cluster like NGC 3590 are born at around the same time from the same cloud of gas, making these clusters perfect test sites for theories on how stars form and evolve.

This image from the Wide Field Imager (WFI) on the MPG/ESO 2.2-metre telescope at La Silla, shows the cluster and the gas clouds surrounding it, which glow in orange and red hues due to the radiation coming from nearby hot stars. WFI's large field of view also captures a colossal number of background stars.

To obtain this image, multiple observations were made using different filters to capture the different colours of the scene.

This image was created by combining images taken in the visible and infrared parts of the spectrum, and a special filter that collected only light coming from glowing hydrogen.

First Exoplanet found around solar twin in star cluster

This artist's impression shows one of the three newly discovered planets in the star cluster Messier 67. 

In this cluster the stars are all about the same age and composition as the Sun. 

This makes it a perfect laboratory to study how many planets form in such a crowded environment. 

Very few planets in clusters are known and this one has the additional distinction of orbiting a solar twin -- a star that is almost identical to the Sun in all respects. Credit: ESO/L. Calçada

ESO HARPS detector cryostat

Astronomers have used ESO's HARPS planet hunter in Chile, along with other telescopes around the world, to discover three planets orbiting stars in the cluster Messier 67.

Although more than one thousand planets outside the Solar System are now confirmed, only a handful have been found in star clusters.

Remarkably one of these new exoplanets is orbiting a star that is a rare solar twin—a star that is almost identical to the Sun in all respects.

Planets orbiting stars outside the Solar System are now known to be very common.

These exoplanets have been found orbiting stars of widely varied ages and chemical compositions and are scattered across the sky but, up to now, very few planets have been found inside star clusters.

This is particularly odd as it is known that most stars are born in such clusters. Astronomers have wondered if there might be something different about planet formation in star clusters to explain this strange paucity.

Anna Brucalassi

Anna Brucalassi (Max Planck Institute for Extraterrestrial Physics, Garching, Germany), lead author of the new study, and her team wanted to find out more.

"In the Messier 67 star cluster the stars are all about the same age and composition as the Sun. This makes it a perfect laboratory to study how many planets form in such a crowded environment, and whether they form mostly around more massive or less massive stars."

The team used the HARPS planet-finding instrument on ESO's 3.6-metre telescope at the La Silla Observatory.

These results were supplemented with observations from several other observatories around the world.

They carefully monitored 88 selected stars in Messier 67 over a period of six years to look for the tiny telltale motions of the stars towards and away from Earth that reveal the presence of orbiting planets.

The small faint constellation Cancer is rich in open clusters and double stars. 

Credit: Starry Night Software, Space.com

This cluster lies about 2500 light-years away in the constellation of Cancer (The Crab) and contains about 500 stars.

Many of the cluster stars are fainter than those normally targeted for exoplanet searches and trying to detect the weak signal from possible planets pushed HARPS to the limit.

Three planets were discovered, two orbiting stars similar to the Sun and one orbiting a more massive and evolved red giant star.

The first two planets both have about one third the mass of Jupiter and orbit their host stars in seven and five days respectively. The third planet takes 122 days to orbit its host and is more massive than Jupiter.

The first of these planets proved to be orbiting a remarkable star—it is one of the most similar solar twins identified so far and is almost identical to the Sun.

It is the first solar twin in a cluster that has been found to have a planet.

Two of the three planets are "hot Jupiters"—planets comparable to Jupiter in size, but much closer to their parent stars and hence much hotter.

All three are closer to their host stars than the habitable zone where liquid water could exist.

Luca Pasquini

"These new results show that planets in open star clusters are about as common as they are around isolated stars—but they are not easy to detect," adds Luca Pasquini (ESO, Garching, Germany), co-author of the new paper.

"The new results are in contrast to earlier work that failed to find cluster planets, but agrees with some other more recent observations. We are continuing to observe this cluster to find how stars with and without planets differ in mass and chemical makeup."

More information: This research was presented in a paper entitled "Three planetary companions around M67 stars", by A. Brucalassi et al., to appear in the journal Astronomy & Astrophysics. (PDF)

ESO WFI Telescope Image: 'Elephant Trunk' Space Clouds Surround Star Cluster - Video

The new photo shows a mysterious ring and structures known as "elephant trunks" — huge columns of interstellar dust and gas. You can watch the video fly-through of the new space cloud photos provided by ESO.

Astronomers used the European Southern Observatory's La Silla Observatory to capture the amazing new images of the space clouds around the distant star cluster NGC 3572.

"This new image shows how these clouds of gas and dust have been sculpted into whimsical bubbles, arcs and the odd features known as elephant trunks by the stellar winds flowing from this gathering of hot young stars," ESO officials wrote in an image description.

The Wide Field Imager on the MPG/ESO 2.2-metre telescope at ESO’s La Silla Observatory in Chile has captured the best image so far of the star cluster NGC 3572, a gathering of young stars, and its spectacular surroundings. 

Image released Nov. 13, 2013. 

Credit: ESO/G. Beccari

Another interesting aspect of the new image is a ring-shaped nebula located a bit above the center of the picture.

Scientists aren't sure what the origin of the nebula is, but they think it might be a leftover from the cloud of material that formed the star cluster, or it could be a bubble around a hot star.

Some astronomers also suggest that it could be a planetary nebula — the remains of a dying sun-like star.

Stars in clusters might have formed at around the same time, but they are incredibly diverse in size, temperature, colour and mass, ESO officials said.

"These gangs of young stars stick together for a relatively short time, typically tens or hundreds of millions of years," ESO officials said.

"They are gradually disbanded by gravitational interactions, but also because the most massive stars are short-lived, burning through their fuel quickly and ultimately ending their lives in violent supernova explosions, thus contributing to the dispersion of the remaining gas and stars in the cluster."

Mini-Neptunes: First transiting planets in a star cluster discovered

In the star cluster NGC 6811, astronomers have found two planets smaller than Neptune orbiting Sun-like stars. Credit: Michael Bachofner

All stars begin their lives in groups. Most stars, including our Sun, are born in small, benign groups that quickly fall apart.

Others form in huge, dense swarms that survive for billions of years as stellar clusters.

Within such rich and dense clusters, stars jostle for room with thousands of neighbors while strong radiation and harsh stellar winds scour interstellar space, stripping planet-forming materials from nearby stars.

It would thus seem an unlikely place to find alien worlds.

Yet 3,000 light-years from Earth, in the star cluster NGC 6811, astronomers have found two planets smaller than Neptune orbiting Sun-like stars.

The discovery, published in the journal Nature, shows that planets can develop even in crowded clusters jam-packed with stars.

"Old clusters represent a stellar environment much different than the birthplace of the Sun and other planet-hosting field stars," says lead author Soren Meibom of the Harvard-Smithsonian Center for Astrophysics (CfA).

"And we thought maybe planets couldn't easily form and survive in the stressful environments of dense clusters, in part because for a long time we couldn't find them."

The two new alien worlds appeared in data from NASA's Kepler spacecraft. Kepler hunts for planets that transit, or cross in front of, their host stars.

During a transit, the star dims by an amount that depends on the size of the planet, allowing the size to be determined.

Kepler-66b and Kepler-67b are both less than three times the size of Earth, or about three-fourths the size of Neptune (mini-Neptunes).

Of the more than 850 known planets beyond our solar system, only four - all similar to or greater than Jupiter in mass - were found in clusters.

Kepler-66b and -67b are the smallest planets to be found in a star cluster, and the first cluster planets seen to transit their host stars, which enables the measurement of their sizes.

Meibom and his colleagues have measured the age of NGC 6811 to be one billion years. Kepler-66b and Kepler-67b therefore join a small group of planets with precisely determined ages, distances, and sizes.

Considering the number of stars observed by Kepler in NGC 6811, the detection of two such planets implies that the frequency and properties of planets in open clusters are consistent with those of planets around field stars (stars not within a cluster or association) in the Milky Way galaxy.

"These planets are cosmic extremophiles," says Meibom. "Finding them shows that small planets can form and survive for at least a billion years, even in a chaotic and hostile environment."

More information: Paper: DOI: 10.1038/nature12279

Astronomers' Capture Hercules Star Cluster

The hundreds of thousands of stars that make the mighty Hercules globular cluster shine bright in this astronomers' photo.

Astrophotography team Bob and Janice Fera took this image in May 18 and 20, 2012 from Eagle Ridge Observatory in Foresthill, Calif.

Also known as M13, this cluster has more than 100,000 stars that shine from about 25,000 light-years away. The brightest stars  are packed tightly at the core and sometimes slam into each other creating new stars called “blue stragglers.”

These blue stars shine a bluish-white because their core temperatures are extremely hot. Bright red stars found within the cluster are cooler because they are older stars that have expanded in size. These stars are often called ancient red giants.

The Feras used an Officina Stellare RC-360AST 14" f/8 Ritchey Chretien Cassegrain telescope with two-element field flattener to observe the M13 cluster. An Apogee Alta U16M CCD camera with Astrodon filters was used to capture the image.