AAVSO Writer’s Bureau Digest For 22 April 2014

2013dec20_aavso_logoThe AAVSO Writer’s Bureau, hosted by the American Association of Variable Star Observers (www.aavso.org), is a selective aggregator of high-quality science content for the amateur astronomer. Several astronomy bloggers, science writers, and official astronomy publishers and organizations provide articles free-of-charge for redistribution through the AAVSO-WB. The five most recent Writer’s Bureau posts are presented below with direct links to the full articles on the author’s own website. CNYO thanks the authors and the AAVSO for making these articles available for free to all astronomy groups!

Starbirth in the Neighborhood

C.C. Petersen, The Spacewriter

2014april22__5_M83Galaxies are huge collections of stars, gas, dust, black holes, and planets. The Milky Way is a good example of a spiral galaxy. It also happens to have a bar of gas and dust and stars across its center, and many places where stars are being born. It turns that when astronomers look at other galaxies, particular spiral galaxies (and many colliding galaxies), they also see regions of starbirth.

Hubble Space Telescope has been astronomy’s “go to” machine in space when astronomers want to look at something like a distant galaxy. This Hubble image shows the pinwheel (spiral) galaxy M83, which lies in our southern hemisphere skies in the constellation Hydra. It’s about 15 million light-years away, and, as you can see here, is ablaze with starbirth regions spread across 50,000 light-years of space.

Read the full article at: thespacewriter.com/wp/2014/01/26/starbirth-in-the-neighborhood/

A Cosmic Bubble That’ll Soon Pop. Hard.

Phil Plait, slate.com

2014april22__4_jeffhusted_sharpless2_308Sometimes, I’m pretty happy our planet circles a relatively calm, normal star. Because when I look at stars like EZ Canis Majoris (aka WR 6, HR 2583, HD 50896, and other aliases), I think that things around here could be a lot less conducive for life.

Why? Because this:

Pretty, isn’t it? But the beauty belies a true monster.

This photo was taken by Jeff Husted, an astrophotographer who observers in the western US. It shows the star EZ CMa (for short), the star just left of center of that ethereal glowing bubble of gas. It’s what’s called a Wolf-Rayet star, one of the more terrifying beasts in the galaxy’s menagerie. It’s a star that started out life with more than 40 times the mass of the Sun, which made it super-hot and extraordinarily luminous. Stars like that can be hundreds of thousands of times as bright as the Sun! A planet orbiting it as close as the Earth to the Sun would be cooked to a vapor pretty rapidly.

Read the full article at: www.slate.com/blogs/…cosmic_bubble_from_a_galactic_monster.html

The Final Countdown Before a Supernova

Phil Plait, slate.com

2014april22__3_hst_sbw1I’m sometimes asked what I think the next exploding star in our galaxy will be. Most people expect I’ll say Betelgeuse, the red supergiant marking Orion’s right shoulder.

But Betelgeuse may not go supernova for another million years, which is a long, long time. There are several stars much closer to The End, and I recently learned of a new one: SBW1.

The star is a blue supergiant, a hot, energetic beast probably about 20 or so times the mass of the Sun. Stars like that don’t live long, just a few million years tops. But we know (we think) it’ll explode much sooner than that, because of that ring you see in the Hubble picture above. How does that ring tell us anything? Ah, glad you asked.

Read the full article at: www.slate.com/blogs/…/sbw1_a_star_on_the_verge_of_supernova.html

A Superluminous Supernova

CfA News, Harvard

2014april22__2_su201401Supernovae are the explosive deaths of massive stars. Among the most momentous events in the cosmos, they disburse into space all of the chemical elements that were produced inside their progenitor stars, including most of the elements essential for making planets and life. Astronomers have recognized for decades that there are several different kinds of supernovae, most fundamentally those that originate from a single massive star and those that develop when one member of a pair of binary stars becomes massive by feeding on its neighbor. Other factors like the stellar composition also come into account. Sorting out all these various complications is critical if astronomers want to be able to reliably classify any particular supernovae and thereby infer its intrinsic brightness, and then use its observed brightness as a measure of its distance.

Recent wide-field surveys searching for supernovae have found that the conventional schema for classifying supernovae may be even more complicated than previously thought. A few years ago a new class called superluminous supernovae was found, characterized by their emitting total radiated energies equal to about ten billion suns shining for a year. Some of these new objects were discovered at cosmological distances, helping to cement the notion that new types were being discovered, and further studies have found even more subdivisions, also based among other things on composition. These new superluminous supernovae can be identified and characterized by the particular way their light fades away after the brightness peak, driven in part by the radioactive decay of elements manufactured in the explosions.

Read the full article at: www.cfa.harvard.edu/news/su201401

New Cutoff For Star Sizes

John Bochanski, Sky & Telescope

2014april22__1_Brown_DwarfAstronomers have found a gap between “real” and “failed” stars.

What does the smallest star look like? This question is deceptively difficult to answer. Stars spend most of their lives fusing hydrogen in their cores, a prime time of life called the “main sequence.” As you go down the scale of stellar sizes on this sequence, stars become dimmer, cooler, and less massive. But determining the absolute properties of the smallest stars — their mass, radius, temperature, and overall light output — is challenging for at least three big reasons.

Read the full article at: www.skyandtelescope.com/astronomy-news/new-cutoff-for-star-sizes/

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