For the first time astronomers have obtained an image of a likely planet orbiting a distant but sun-like star. Like a lot of claims back in the 1990s about repeated “first” discoveries of black holes, there are a number of issues to consider about these early announcements. We’re going to see a lot more “first” planet images of various sorts in years to come, and have already seen a couple around low-mass brown dwarf stars. Still, this is wicked cool and a hint of a flood of information to come about planets in our galaxy. Let’s see the picture.
The big thing in the middle is the sun-like star, some 500 light-years away from us. The faint speck circled in red is our purported exoplanet, thought to be some 330 astronomical units (AU) from its sun (Earth is 1 AU from the sun, and Jupiter is 5 AUs). The bar on the bottom left shows an angle of one arcsecond, which is 1/3600 of a degree. The official caption for the image reads:
Gemini adaptive optics image of 1RSX J160929.1-210524 and its likely ~8 Jupiter-mass companion (within red circle). This image is a composite of J-, H- and K-band near-infrared images. All images obtained with the Gemini Altair adaptive optics system and the Near-Infrared Imager (NIRI) on the Gemini North telescope. Photo Credit and Press Release: Gemini Observatory.
First we have what the astronomers call the “phone number” of the star, based on its position in the sky. Easy to say and remember, isn’t it? Second, the image isn’t actually an optical picture; it’s a pseudocolor image based on near-infrared colors. One reason for using the infrared is that our adaptive optics system work in the infrared, and these adaptive optics systems are what let us create such sharp images using ground-based telescopes. Without these high-tech optics the faint light of the little speck of the planet would be smeared over an area larger than the red circle, and much harder to detect, as well as more difficult to distinguish from its sun. Another reason for using the infrared is that this planet is hot. Not quite star-hot, but 1500ºC. Its way far from its sun, so why so hot?
The astronomers have been very clever, looking at a cluster of young stars, where the planets also will be young. A giant planet like Jupiter or this one, eight times larger, takes billions of years to fully contract and cool. Young hot planets like this one put out most of their light in the infrared part of the spectrum, and much, much more light than they would if they had time to cool.
Using this sort of approach, the easiest planets to see will be large, young planets at large orbital distances, exactly what we have here. The first detections of planets using spectroscopy and the Dopplershift wobbles of their suns was tailor-made to find large planets at small orbital distances, exactly what was first discovered.
Astronomers once thought that planets were very rare, the result of a chance close encounter between two stars. That was wrong. Then there was the notion that planets might be common, and that most star systems would resemble ours. That was wrong. Now we have the possibility of a giant planet forming at huge distances from its sun, and we have no idea theoretically how this happens, but it seems that it does.
This is cool for me as both an astronomer and science fiction writer. Solar systems have all sorts of things going on we don’t understand, and this makes this great for research and speculation. It makes me want to see a lot more stories set in systems that don’t resemble ours at all and possess a lot more strange possibilites.
Rather than shutting the door on speculation and creativity, it seems to me that astronomy is blowing open doors as fast as we can invent new technologies. The next generation of writers like Hal Clement and Robert Forward have no excuses not to top their originality while maintaining scientific accuracy.
We’re still more than a decade away from imaging an Earth-like planet, or to see a planet outside our solar system as anything but a point of light, but it’s a cool time to be a fan of science or science fiction.
Anyone have recommendations about novels pushing the world-building since we’ve started to learn about real exoplanets?