Monthly Archives: February 2012

astronomy, astronomy news, eta carinae, hypernova, star death

Attention, Luminous Blue Variable Fans!

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More Outburst Data from Eta Carinae

There’s an unstable star out there that’s on the brink of destruction. It lies some 7,500 light-years away, embedded in a star-forming region called the Carina Nebula. The star itself is called Eta Carinae (Eta Car, for short), and it’s actually a double star system. Some 170 years ago, observers noticed that it was growing very bright. Over time, it became the second-brightest star in the sky.

This unexpected brightening came to be known as the “Great Eruption”, and astronomers of the time watched it with great interest — but didn’t have much in the way of sophisticated instrumentation to really dig into the object to tell what was going on there.  Today, modern telescopes are showing us what really happened during the Great Eruption.

The story goes like this:  the more massive member of the duo — a type of star called a luminous blue variable — began blasting out huge amounts of its own mass. Over the period of 20 years that it was seen to be erupting (from 1837 to 1858), this heaving star lost more than 20 solar masses of material.  Much of that “star stuff” can still be seen in a double-lobed cloud surrounding the system.

These images reveal light from a massive stellar outburst in the Carina Nebula reflecting off dust clouds surrounding a behemoth double-star system. The color image at left shows the Carina Nebula, a star-forming region located 7,500 light-years from Earth. The massive double-star system Eta Carinae resides near the top of the image. The star system, about 120 times more massive than the Sun, produced a spectacular outburst that was seen on Earth from 1837 to 1858. But some of the light from the eruption took an indirect path and is just now reaching our planet. The light bounced off dust clouds (the boxed region at the bottom of the image, indicating an area of space that lies about 100 light-years away ) and was rerouted to Earth, a phenomenon called a light echo. The image was taken in February 2000 by the U.S. National Optical Astronomy Observatory's Curtis Schmidt Telescope at the Cerro Tololo Inter-American Observatory (CTIO) in Chile. The three black-and-white images at right show light from the eruption illuminating dust clouds near the doomed star system as it moves through them. The effect is like shining a flashlight on different regions of a vast cavern. The images were taken over an eight-year span by the U.S. National Optical Astronomy Observatory's Blanco 4-meter telescope at the CTIO. Credit: NASA, NOAO, and A. Rest (Space Telescope Science Institute, Baltimore, Md.)

Eta Car (the LBV) is a massive dying star.  Such stars do not make up the majority of stellar systems in our galaxy, so of course, astronomers are quite interested in what sort of death process Eta Car will go through. Unlike our Sun, which will sort of gently swell to become a red giant (and lose much of its mass in a less-explosive manner), Eta Car will likely go out in a huge cataclysm called a supernova.  Some astronomers suggest it could be such a catastrophic event it would be termed a “hypernova.”

However it blows, Eta Car’s passing will afford astronomers with a ringside seat to stellar mass destruction. The first thing they’ll detect when it blows is a gamma-ray burst that could affect our communications satellites.  After that, they’ll be busy cataloguing the process of the explosion and the ring of debris that will be rushing out to space.  Some astronomers have suggested that this explosion could happen anytime from the next few years to a few million years from now.  Regardless of when it blows, it’s not likely to hurt us much on Earth, since the rotational axis of the system is pointed away from us.

Hubble Space Telescope has been observing Eta Car for a couple of decades now, watching subtle changes in the cloud surrounding the stellar pair, and analyzing the mixes of gas and dust in that cloud. The most recent observations actually pinpoint an echo of the light from the Great Eruption bouncing off more distant parts of the clouds.   The observations of the light echoes mark the first time astronomers have used spectroscopy to analyze a light echo from a star undergoing powerful recurring eruptions, though they have measured this unique phenomenon around exploding stars called supernovae. In spectroscopy, light from an object is captured by the telescope and sent to an instrument (called a spectrograph) that breaks that light into all its wavelengths. Each wavelength of light tells you something about the chemical makeup of the object, its speed through space, whether or not it is spinning, and gives a measure of its temperature.  For the Hubble observations, the spectrograph  captured Eta Car’s characteristic “fingerprints,” providing details about its behavior, including the temperature and speed of the ejected material.

The light echoes from Eta Car are telling astronomers that this restless, heaving old star system does not behave like other stars of its class.  The temperature of the outflow from Eta Carinae’s central region, for example, is about 8,500 degrees Fahrenheit (5,000 Kelvin), which is much cooler than that of other erupting stars. So,this gives some important clues about what’s happening inside the star.  There are other clues in the stream of light HST is studying, and light from the outburst is still on its way to Earth. Astronomers are expecting another brightening in about six months and that will give them more data to chew on as they seek to understand how this star is going through its death process. So, stay tuned.  There’s more news on the way from Eta Car!

astronomy

Black Holes, Stars, Planets, Galaxies, and the Cosmos

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That’s What I Write About

I’ve been running this blog since just after the Cosmic Dark Ages ended (about the time blogs began), and in it, I write about astronomy and space topics.  If you analyze what I’ve written about over the years, you’ll see that I like to write about Mars or black holes, or colliding galaxies, or other such fascinating topics.  They are part and parcel of understanding the origin and evolution of everything in the universe.

Black holes are objects that were once just an idea in a scientist’s brain, but as more and more observations of strange objects came through our telescopes, and as we were able to apply the laws of physics, motion, and gravity to explain these observations, our understanding of black holes grew. Today, we find them all over the place — they’re not new objects, but our discovery and understanding of them is relatively new (in the grand scheme of things, as one of my astronomy professors used to say).

Stars are all over the place.  The closest one is the Sun, and that’s the one that we based our understanding of other stars — and their formation, evolution, and deaths — upon. Of course, nowadays, we study many different types of stars, and know that the formation is roughly the same for all stars. The evolution is similar, up to a point. The deaths, however, are wildly different, depending on the mass of the star.  So, a star like the Sun forms in a cloud of gas and dust, just as every other star does.  It consumes nuclear fuel in its core and in return, puts out light and heat.  Most stars do that. But,when the Sun dies, it will go quietly — in comparison to a star with several tens of solar masses or larger. Those massive stars will explode as supernovae.  Big difference.

In dying, all stars lose mass to the cosmos. That mass, in the form of gas and dust, enriches the interstellar medium, and from that “enrichment” we get the materials from which other stars — and planets (and comets, asteroids, rings, moons) are made.  Planets are the ashes of dead stars… as are we, since we evolved on a planet, and our bodies contain the same materials.

All stars and planets are part of galaxies, which are huge conglomerations of stars and varying amounts of interstellar material.  Galaxies first formed a few hundred million years after the universe began, and they have formed and reformed, collided, reshaped themselves into larger galaxies, ever since.

These are the objects (and some of the processes) that I like to write about in this blog. Occasionally, I will stray into other topics, such as politics, or how you can view the sky, and that’s fine.  As long as the subject is somehow related to astronomy, planetary science, space science — you get the idea — I write about it. It’s my blog, my rules. And, it’s my way of sharing (for free) the topics I learned about in graduate school with people who are also interested in those topics.

I don’t get a lot of comments from people who want to talk about those sciences. When I do, I allow them to be posted (I moderate comments).  Mostly, though, I weed out crap from the comment feed.  Most of the comments that get posted are not related to the subject, or they’re spam.  Luckily, I moderate comments, and I have a good spam filter. So, all those half-literate, fake English spam comments that tell me that the writer is part of a collective that wants to start blogging and will I help, or tell me that my blog looks weird in some browser I’ve never heard of, or that post gibberish with a link to a pr0n site — those bots are wasting the sender’s time and money. They don’t get posted here.

What do I NOT write about?  It’s easier to say what this blog isn’t. It’s NOT a public relations device.  It’s not an instant “news” service where someone can send me a story and I’ll publish it unread. And, it’s not a place where they can send some fluffy press release that has nothing to do with the topics I DO write about and expect me to give free publicity. Same goes with half-baked, illogical conspiracy theories that the senders want me to use to “expose” the government, the Trilateral Commission, NASA, the medical profession, big pharma, big Farma, the Greys, the Pleiadeians, etc. etc.

Not gonna happen.  I make a living as a writer talking about scientific exploration; so folks who expect me to be their free publicity machine should consider respecting my expertise and interests, rather than expecting a free ride.

I DO happily accept press releases each day from vetted sources that talk about recent discoveries in astronomy, space science, planetary science, astrobiology, related technologies, legitimate cosmology, and so forth.  And, I use that information to do more research into the topics they discuss, and then create stories that share the cosmos (and our exploration of it) with my readers.

All that stuff I DO like to write about is the stuff of the cosmos. It teaches the wonders of the universe. It’s science at its purest, hardest, and most satisfying. What could be better than that?