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.

Search for Life Suggests Alien Solar Systems More Habitable than Ours

Scattered around the Milky Way are stars that resemble our own sun—but a new study is finding that any planets orbiting those stars may very well be hotter and more dynamic than Earth.

That’s because the interiors of any terrestrial planets in these systems are likely warmer than Earth—up to 25 percent warmer, which would make them more geologically active and more likely to retain enough liquid water to support life, at least in its microbial form.

The preliminary finding comes from geologists and astronomers at Ohio State University who have teamed up to search for alien life in a new way.

They studied eight “solar twins” of our sun—stars that very closely match the sun in size, age, and overall composition—in order to measure the amounts of radioactive elements they contain.

Those stars came from a dataset recorded by the High Accuracy Radial Velocity Planet Searcher spectrometer at ESA's European Southern Observatory in Chile.

They searched the solar twins for elements such as thorium and uranium, which are essential to Earth’s plate tectonics because they warm our planet’s interior.

Plate tectonics helps maintain water on the surface of the Earth, so the existence of plate tectonics is sometimes taken as an indicator of a planet’s hospitality to life.

Of the eight solar twins they’ve studied so far, seven appear to contain much more thorium than our sun—which suggests that any planets orbiting those stars probably contain more thorium, too.

That, in turn, means that the interior of the planets are probably warmer than ours.

“If it turns out that these planets are warmer than we previously thought, then we can effectively increase the size of the habitable zone around these stars by pushing the habitable zone farther from the host star, and consider more of those planets hospitable to microbial life,” said Ohio State doctoral student Cayman Unterborn, who presented the results at the American Geophysical Union meeting in San Francisco this week.

“At this point, all we can say for sure is that there is some natural variation in the amount of radioactive elements inside stars like ours,” he added.

“With only nine samples including the sun, we can’t say much about the full extent of that variation throughout the galaxy. But from what we know about planet formation, we do know that the planets around those stars probably exhibit the same variation, which has implications for the possibility of life.”

His advisor, Wendy Panero, associate professor in the School of Earth Sciences at Ohio State, explained that radioactive elements such as thorium, uranium, and potassium are present within Earth’s mantle. These elements heat the planet from the inside, in a way that is completely separate from the heat emanating from Earth’s core.


Read more of this article at scienceblog.com

Dwarf planet Makemake: Confirmation that it lacks atmosphere

Dwarf planet Makemake is about two thirds of the size of Pluto, and travels around the Sun in a distant path that lies beyond that of Pluto but closer to the Sun than Eris, the most massive known dwarf planet in the Solar System.

Previous observations of chilly Makemake have shown it to be similar to its fellow dwarf planets, leading some astronomers to expect its atmosphere, if present, to be similar to that of Pluto.

However, the new study now shows that, like Eris, Makemake is not surrounded by a significant atmosphere.

The team, led by Jose Luis Ortiz (Instituto de Astrofisica de Andalucia, CSIC, Spain), combined multiple observations using three telescopes at ESO's La Silla and Paranal observing sites in Chile - the Very Large Telescope (VLT), New Technology Telescope (NTT), and TRAPPIST (TRAnsiting Planets and PlanetesImals Small Telescope) - with data from other small telescopes in South America, to look at Makemake as it passed in front of a distant star.

"As Makemake passed in front of the star and blocked it out, the star disappeared and reappeared very abruptly, rather than fading and brightening gradually. This means that the little dwarf planet has no significant atmosphere," says Jose Luis Ortiz.

"It was thought that Makemake had a good chance of having developed an atmosphere - that it has no sign of one at all shows just how much we have yet to learn about these mysterious bodies. Finding out about Makemake's properties for the first time is a big step forward in our study of the select club of icy dwarf planets."

Makemake's lack of moons and its great distance from us make it difficult to study, and what little we do know about the body is only approximate.

The team's new observations add much more detail to our view of Makemake - determining its size more accurately, putting constraints on a possible atmosphere and estimating the dwarf planet's density for the first time.

They have also allowed the astronomers to measure how much of the Sun's light Makemake's surface reflects - its albedo. Makemake's albedo, at about 0.77, is comparable to that of dirty snow, higher than that of Pluto, but lower than that of Eris.

It was only possible to observe Makemake in such detail because it passed in front of a star - an event known as a stellar occultation.

These rare opportunities are allowing astronomers for the first time to find out a great deal about the sometimes tenuous and delicate atmospheres around these distant, but important, members of the Solar System, and providing very accurate information about their other properties.

Occultations are particularly uncommon in the case of Makemake, because it moves in an area of the sky with relatively few stars.

Accurately predicting and detecting these rare events is extremely difficult and the successful observation by a coordinated observing team, scattered at many sites across South America, ranks as a major achievement.

"Pluto, Eris and Makemake are among the larger examples of the numerous icy bodies orbiting far away from our Sun," says Jose Luis Ortiz.

"Our new observations have greatly improved our knowledge of one of the biggest, Makemake - we will be able to use this information as we explore the intriguing objects in this region of space further."