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New Horizons Spots Pluto’s Largest Moon

By David Reneke

David Reneke’s wrap-up of space and astronomy news.

Pluto is looming larger as NASA’s robotic spacecraft mission “New Horizons” heads for a rendezvous with the dwarf planet on 14 July 2015. It’s expected to be the first spacecraft to fly by and study Pluto and its moons. NASA may then also attempt fly-bys of one or more other Kuiper Belt objects.

Pluto could quite easily be classified as an enigma wrapped in a puzzle with a question mark tacked on the end. What is it and where did it come from? Is it an errant moon of Neptune or an asteroid? Its orbit is eccentric, it hasn’t cleared its orbital path and it was too small to be called a planet in 1930 anyway. Hopefully we’ll have the answers soon.

Using its highest resolution telescopic camera, New Horizons has spotted Pluto’s largest ice-covered moon, Charon, for the first time. This represents a milestone on the spacecraft’s 10-year journey to conduct the initial reconnaissance of the Pluto system and the Kuiper Belt.

“The image itself might not look very impressive to the untrained eye, but compared to the discovery images of Charon from Earth, these initial images from New Horizons look great!” says Project Scientist Hal Weaver of the Johns Hopkins University. “We’re very excited to see Pluto and Charon as separate objects for the first time from New Horizons.”

The spacecraft was still 880 million km from Pluto when its Long Range Reconnaissance Imager (LORRI) snapped a total of six images in July. “These new LORRI images of Charon and Pluto should provide some interesting science too,” says Alan Stern of the Southwest Research Institute.

These images are just a hint of what’s to come when New Horizons gets closer to the Pluto system. In 2015, the spacecraft is scheduled to pass just 12,500 km above Pluto’s surface, where LORRI will be able to spot features about the size of a football field.

Birth of a Monster Milky Way Star

Astronomers have observed in unprecedented detail the birth of a massive star within a dark cloud core of our Milky Way galaxy, about 10,000 light years from Earth. It’s the best observation yet of a massive star embryo growing within a dark cloud.

The team used the new Atacama Large Millimetre Array (ALMA) telescope in Chile, the most powerful radio telescope in the world, to view the stellar womb that, at 500 times the mass of the Sun and many times more luminous, is the largest ever seen in our galaxy.

The researchers say their studies reveal how matter is being dragged into the centre of the huge gaseous cloud by the gravitational pull of the forming star, or stars, along a number of dense threads or filaments.

“The remarkable observations from ALMA allowed us to get the first really in-depth look at what was going on within this cloud,” said lead author Dr Nicolas Peretto of Cardiff University. “We wanted to see how monster stars form and grow, and we certainly achieved our aim. One of the sources we have found is an absolute giant – the largest protostellar core ever spotted in the Milky Way!

Although they already believed that the region was a candidate for a massive star-forming cloud, astronomers were not expecting to find such a massive embryonic star at its centre. This cloud is expected to form at least one star 100 times more massive than the Sun and up to a million times brighter. Only about one in 10,000 of the stars in the Milky Way eventually reach that kind of mass.

Different theories exist as to how these massive stars form, but the team’s findings lend weight to the idea that the entire cloud core begins to collapse inwards, with material raining in towards the centre to form one or more massive stars. It’s a long-held but cherished theory.

Prof Gary Fuller of the University of Manchester said: “Not only are these stars rare, but their births are extremely rapid and childhood short, so finding such a massive object so early in its evolution in our galaxy is a spectacular result”.

Observations reveal in superb detail the filamentary network of dust and gas flowing into the central compact region of the cloud, and strongly support the theory of global collapse for the formation of massive stars. Matter is drawn into the centre of the cloud from all directions, but the filaments around the star contain the densest gas and dust.

Dr Peretto added: “Astronomers believe that’s how these distinct patterns are generated. We managed to get these very detailed observations using only a fraction of ALMA’s ultimate potential. ALMA will definitely revolutionise our knowledge of star formation, solving some current problems and certainly raising new ones.”

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