I just read somewhere that March 10th is the International Day of Awesomeness. It’s probably not an official government holiday or anything, but seems to exist to celebrate all things awesome. So, what could be more awesome than the starry sky? Living where I do (high in the mountains) with reasonably clear skies on many nights, I can step outside and look up and grok the awesomeness of the stars. And, this past week or so — and into March — the awe-inspiring sight of the planets Venus, Jupiter and Mercury just after sunset. Mars is rising in the East, and if you wait a few more hours, you can see Saturn rising very late in the evening. If you have binoculars or some kind of telescope, so much the better. You can check out Jupiter’s moons, for example. Or, if our own Moon is up, you can scan its cratered surface. That’s the kind of astronomy awesomeness that gets people hooked on stargazing for life.
Speaking of telescopes, I know that people have a lot of preconceptions and misconceptions about ‘scopes. When I worked at Sky & Telescope, we regularly answered questions in our magazines about the “best” scope to buy, the “most economical” and so on. Truth is, what you buy depends on what you want to look at, or if you’re planning to do astrophotography. Or, if you just want something you can easily pick up and take outside. That’s where binoculars come in handy, and I’ve always recommended people start out with a pair of 10x50s as a good choice. But, telescopes can give you awesome views, too. I’d recommend you peruse Sky&Telescope.com or Astronomy.com for some good advice there.
The Galileoscope. Courtesy Galileoscope.org.
A former colleague from Sky & Telescope got involved a few years ago in a cool project called the Galileoscope. It was originally created to help celebrate the Interational Year of Astronomy in 2009. The Galileoscope is a small, build-it-yourself telescope that thousands and thousands of people have constructed and used to look at the sky. It’s a perfect way to introduce children to the sky and the instruments we use to observe it with. You can learn more about the Galileoscope here, including where it can be purchased. By the way, if any readers work in or run planetarium or science center gift shops, there are special discounts for bulk purchases to sell in gift shops. Check it out! It’s awesome in its own right and worthy of celebration!
I mentioned above about how the planets are lining up for some gorgeous views in the next few weeks. In fact, I focus on those views in the latest installment of Our Night Sky, the monthly stargazing program I produce for Astrocast.TV. So, if you’re into some planetary viewing awesomeness, check it out. It’s about four minutes long, and along with the planets, we look at a few constellations and a couple of deep-sky objects. It’s enough to get you started on some awe-inspiring sightseeing through the cosmos!
Supernova 1987A, in the Large Magellanic Cloud, a nearby galaxy. Astronomers in the Southern hemisphere witnessed the brilliant explosion of this star on Feb. 23, 1987. Shown in this NASA/ESA Hubble Space Telescope image, the supernova remnant, surrounded by inner and outer rings of material, is set in a forest of ethereal, diffuse clouds of gas. This three-color image is composed of several pictures of the supernova and its neighboring region taken with the Wide Field and Planetary Camera 2 in Sept. 1994, Feb. 1996 and July 1997. Courtesy Hubble Heritage Team (AURA/STScI/NASA/ESA).
It had to have been quite an exciting thing for Ian Shelton and Oscar Duhalde when they first saw a brightening star on a photographic plate that hadn’t been there night before. Or, for Albert Jones of New Zealand, and Rob McNaught in Australia, who saw the same brightening and must have wondered “What??!”. In Chile, Ian stepped outside the Las Campanas Observatory in Chile to visually check that area of the sky. Sure enough, there was a hugely bright star in the Large Magellanic Cloud that wasn’t that bright the night before. All three observers had discovered the supernova of the century, named Supernova 197a. It was the last explosive gasp of the dying blue supergiant star Sanduleak -69° 202 (called the “progenitor star”), and an eye-opener for scientists studying supernovae, particularly a type called “core collapse” or Type II.
When massive stars like the one that died to form Supernova 1987a come to the ends of their lives, they have basically run out of fuel to consume in their cores. Stars begin by fusing hydrogen to helium in their cores. The result is heat and light. Eventually the star runs out of hydrogen as fuel, so it begins to fuse helium, then carbon, and so forth, until it gets to iron. At that point, fusing iron takes more energy than the process can put out, and that’s when the fusion action stops. Dead. And, there’s no way that the core can support the mass of the layers above it. So, it collapses. The outer layers collapse, too, and when they hit the core, they rebound out, forming a huge shock waves that blows everything but the core out into space. That’s what we detect as a supernova.
Hubble images show the sequence of ring expansion around Supernova 1987a. Courtesy Mark McDonald via Creative Commons Share-Alike License.
Supernova 1987a was immediately surrounded by an expanding ring of debris. Astronomers immediately began looking for that ring, and eventually the Hubble Space Telescope took images and data of it a few years later. Today, 25 years after the first detection, astronomers are still watching the debris expand. As it does, it collides with material (gas and dust clouds) that the star shed earlier in its death process. When the shock wave and expanding debris make contact with that material, everything lights up.
Supernova 1987a has given astronomers new insight into the types of stars that become Type II supernovae. For one thing at the time of Supernova 1987a’s discovery, blue supergiants were not considered likely supernova candidates for a variety of reasons. Yet, here was one exploding in a supernova. So, astronomers had to go back and re-examine their ideas and theories about these kinds of high-mass stars.
For one thing, the progenitor star, Sanduleak -69° 202, just wasn’t on people’s radar as a possible supernova candidate. It didn’t show any hints that it was about to blow itself up. That raises a lot of questions about what we know of high-mass stars and their death cycles.
A composite image of supernova 1987a taken 20 years after the explosion was first detected. Data came from NASA's Chandra X-ray Observatory and Hubble Space Telescope. The outburst was visible to the naked eye, and is the brightest known supernova in almost 400 years. This shows the effects of a powerful shock wave moving away from the explosion. Bright spots of X-ray and optical emission arise where the shock collides with structures in the surrounding gas. These structures were carved out by the wind from the destroyed star. Hot-spots in the Hubble image (pink-white) now encircle Supernova 1987A like a necklace of incandescent diamonds. The Chandra data (blue-purple) reveals multimillion-degree gas at the location of the optical hot-spots. These data give valuable insight into the behavior of the doomed star in the years before it exploded. Credit: X-ray: NASA/CXC/PSU/S.Park & D.Burrows.; Optical: NASA/STScI/CfA/P.Challis
The progenitor star was a very compact and blue; not the kind of star to explode like this. So, there had to be another influence. It turns out there was more than one star involved; this system was a binary. One idea is that both the progenitor star and its companion were engulfed in an envelope of material. The companion may have dissolved in some way, and that affected the progenitor star, and helped send it down the road to supernova-hood. There are other explanations, and current and ongoing studies of the supernova remmants and the immediate neighborhood may help solve the mystery of why a blue supergiant exploded as it did.
Once the explosion DID occur, aside from the shock wave and light, there was also a huge burst of neutrinos — fast-moving particles that whiz across space. One expert estimated that 1057neutrinos were generated by the explosion, speeding away in all directions. A few of them hit Earth and were detected by the Kamioka experiment in Japan, and by detectors in Cleveland and the former Soviet Union.
All in all, only 19 neutrinos were detected from 1987a, but they told astronomers a story of core-collapse inside a massive star. They also suggest that a neutron star formed in the wake of the core collapse of the supernova 1987a progenitor star. As of today, that neutron star has yet to be observed. There are a number of reasons for that, including the formation of a black hole at the same site. Astronomers are still looking.
So, 25 years after the appearance of Supernova 1987a, there’s still something to study. The continued expansion of the shock waves and debris rings into the surrounding material in interstellar space will provide much data about the material and those interactions. The search for the neutron star (or whatever’s left of the progenitor star), continues. And, astronomers continue to use this event to bolster and tweak theories about massive stars and their ultimate ends. It’s been a fascinating quarter-century, and the data continues to flow. No doubt Hubble Space Telescope and ESA’s Herschel Space Observatory will continue to watch this object, as will the other facilities (such as Gemini Observatory) around the world. It will likely be a target for James Webb Space Telescope. So, stay tuned for new images and data to mark the 25-year mark of this cosmic event. Supernova 1987a might have exploded, but it’s not dead yet.
