NASA/Serge Brunier
Hard Science

These Maps Reveal How Little We Know About Our Own Galaxy

Welcome to the never-ending search for exoplanets.

Our Mysterious Universe

It is surprisingly easy to forget how vast our universe truly is. Since we are able to glimpse light from stars that are an astonishing distance away, it’s easy to assume that we have a pretty firm grasp on the cosmos. True, we may need to use telescopes in order to peer across the expanse and truly see distant objects; however, the mere fact that we can see this far is reassuring.

But in fact, we know surprisingly little about even our own galaxy.

The Search for Other Worlds

It may be a little hard to believe that the Milky Way is largely unexplored, but keep in mind that there’s a lot that we don’t know about our very own planet. Indeed, according to the National Oceanic and Atmospheric Administration, we have explored less than 5% of the ocean. Considering the ocean covers some 70% of our planet, that is a lot of unexplored territory. Moreover, although the surface of the Earth is littered with people, researchers exploring the recesses of our world discover dozens of new species each day (literally).

Like early explorers mapping the continents of our globe, astronomers are busy charting the spiral structure of our galaxy, the Milky Way. Using infrared images from NASA's Spitzer Space Telescope, scientists have discovered that the Milky Way's elegant spiral structure is dominated by just two arms wrapping off the ends of a central bar of stars. Previously, our galaxy was thought to possess four major arms. This artist's concept illustrates the new view of the Milky Way, along with other findings presented at the 212th American Astronomical Society meeting in St. Louis, Mo. The galaxy's two major arms (Scutum-Centaurus and Perseus) can be seen attached to the ends of a thick central bar, while the two now-demoted minor arms (Norma and Sagittarius) are less distinct and located between the major arms. The major arms consist of the highest densities of both young and old stars; the minor arms are primarily filled with gas and pockets of star-forming activity. The artist's concept also includes a new spiral arm, called the "Far-3 kiloparsec arm," discovered via a radio-telescope survey of gas in the Milky Way. This arm is shorter than the two major arms and lies along the bar of the galaxy. Our sun lies near a small, partial arm called the Orion Arm, or Orion Spur, located between the Sagittarius and Perseus arms.
Map showing recently discovered exoplanet compared to most distant ever found. Image credit: NASA

With this in mind, the above map, which was recently released by NASA, shows the range of the Kepler Space Telescope. This is the primary instrument used to discover exoplanets (worlds that reside in alien solar systems). Kepler’s field of view is the small, red cone.

That’s it. That little cone is nearly all we have to detect other worlds.

The yellow dots show all of the planets discovered with microlensing. This method of detection is much harder. So the problem is thus: While Kepler has discovered thousands of alien worlds in its field of view, its range is limited to a short, narrow band. And while microlensing can find planets much farther out, it is a bit trickier, resulting in just a handful of discoveries.

So. There we are. This is the expanse of space in which we’ve been able to search for alien worlds. A little cone of red and a few smatterings of yellow.

Notably, the map also shows one of the latest exoplanets confirmed via microlensing, which is 13,000 light years away from Earth. Ultimately, this planet is about half as far away as the farthest exoplanet ever discovered, which you can also see in the image.

These Maps Reveal How Little We Know About Our Own Galaxy
Image Credit: Las Cumbres Observatory

In essence, microlensing is a celestial phenomenon that sees light become distorted by an object’s gravity. Basically, when stars or galaxies appear to overlap with background objects, the distortion caused by the warping of spacetime magnifies the farthest of the two sources, helping us study a distant object more closely.

The above image gives you a pretty good breakdown of how this works.

For exoplanets, when microlensing is in effect, planets orbiting the frontmost source might leave a discernible signature on the magnified object, thus allowing us to deduce the existence of planets that are much too distant to be seen traditionally. Overall, around 30 planets have been detected using this method, the most distant of which is believed to be 25,000 light-years away.

These Maps Reveal How Little We Know About Our Own Galaxy

If you need a final breakdown of just how immense our cosmos truly is, the above image is a clearer view of what Kepler can (and cannot) see.

But of course, that’s not to say we don’t know anything. Indeed, the amount of data Kepler has given us is rather staggering (just maybe not when considered alongside the true immensity of our cosmos). The latest significant discovery was made by the mission in July 2015, when the spacecraft found a high value exoplanet named Kepler-452b, which is orbiting its parent star only 20 percent brighter than our Sun.

The newly-found planet was dubbed a “bigger, older cousin” to Earth, as it’s 60 percent larger in diameter than our world and has spent six billion years in the habitable zone of its star (that’s a few billion years longer than Earth has been around).

With the Kepler-452b discovery, the total number of confirmed planets has increased to 1,030.

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