February 17, 2019

05.06.10: An Exoplanet Family Portrait.

Astronomers have recently accomplished another amazing first; the first images of an exoplanetary system taken with modest sized optics. But to perform this feat, several ground-breaking techniques had to first be pioneered. The target was HR 8799, a known exoplanetary system 120 light-years distant in the constellation Pegasus. The instrument was the Hale telescope just north of San Diego, and the team was out of NASA’s Jet Propulsion Laboratory in San Diego. Using a combination of coronagraph and masking the scope down to a diameter of 1.5 meters in diameter, the team was able to capture the above resulting image. The revolutionary “funnel coronagraph” was necessary to block the swamping light of the parent star; the masking was used to maximize the use of adaptive optics. The image was also taken in the infrared, an area of the spectrum in which the young hot planets generate the most energy. “The trick is to suppress the starlight without suppressing the planet light,” Stated JPL Astrophysicist Gene Serabyn. To give you a sense of scale, the three exoplanets pictured lay about 24 to 68 A.U. from their host sun; our own Jupiter orbits at a distance of about 5 A.U. Not only will the technique be capable of being scaled up for the observatory big guns, but it could also prove effective for space-based platforms, where a tension always exists between what astronomers would like to launch and payload limitations. Expect to see more exoplanet images via this method in the near future!

Review: The Telescope by Geoff Anderson.

Few inventions are as near and dear to our hearts as that of the telescope. Before its invention, astronomy was scarcely better than its pseudo-science companion of astrology in its knowledge of predicting the universe as it truly is. In this week’s review, we’ll look at The Telescope by Geoff Anderson out from Princeton Press as it traces the history of this noble instrument, its origins, the theory of optics, and our present day understandings and the exciting realm of telescopes yet to come.Out from Princeton University Press!

Think you know everything about telescopes? The Telescope will take you through designs from classical refractors to Coudè focus complexities. This would serve as a good 101 for anyone thinking of building or even purchasing a telescope, as a lot of the optical basics are discussed. You can even skip through chapters, and the author even suggests that you don’t have to struggle through chapters on interferometry (but of course we did!) unless you really want to.

The study of how early astronomers actually functioned always personally fascinates me. We all know the discoveries of Galileo, but just how did he make those refractors in a renaissance era work shop? The absurdity of some of the focal lengths used was astounding; this was required to overcome the fringes on chromatic aberration until 2-element crown and flint objectives were perfected. And don’t forget, they had to handcraft eye-pieces, as well. Just how many modern day telescope makers do that?

The evolution of site selection and observatory construction is also discussed; it’s a generally underappreciated fact that seeing and turbulence makes up about 90% of your ultimate astronomical success. Early telescope users were content to perch their tubes on the ledge of a study window. It’s only been in the last century or so that site selection prior to observatory construction has really matured. In the modern era, the effects of encroaching light pollution also has to be accounted for. Telescopes have gone from backyard curiosities to behemoths of national significance.

The modern era of scopes is also traced, from the Hale and Keck telescopes to the Hubble Space Telescope, which is appropriately given its own chapter. The chapter “When Good Telescopes go Bad” is particularly illuminating, as it demonstrates the engineering challenges that seem to plague every great instrument. It’s been said that it’s never truly a great scientific or engineering breakthrough until someone has had a nervous breakdown, and building cutting edge telescopes is certainly a case in point.  The author also addresses the innovative methods the have been developed to squeeze as much information as possible out of every photon of light. Just think, we can know speed, direction, composition and more just from “tasting” starlight. This was first developed by the breakthrough of spectroscopy, and further refinements such as interferometry and adaptive optics have pushed the envelope even further. adaptive optics itself used to be classified, as it was used primarily to peek at Russian payloads in low-Earth orbit. Some of this technology is truly amazing; for example, did you know it’s possible to “record” a conversation in a room just by measuring via laser the vibrations imparted on the windows? To this effect, the Oval Office actually employs “shakers” on its outer panes, probably not much different than the vibrate mode on your cell phone.

A look at the key discoveries of the telescope and some of the more bizarre and unusual telescopes is also given treatment; two of our favorite are the use of liquid metal (mercury in a precisely rotated dish!) telescopes, and of course, the Laser Interferometry Gravitational wave Observatory, a “telescope” used to hunt for gravity waves.

And that’s just the beginning. The future of telescopes will see the James Webb Space Telescope, mega observatories such as the Thirty Meter Telescope (TMT) and the 100-meter OverWhelmingly large telescope (OWL) and perhaps even more exotic arrays such as the Terrestrial Planet Finder or a large crater-based instrument on the Lunar far-side.

Do give the Telescope a look if you are thinking of buying, building, or just have a passion for these grand old instruments. Telescopes represent the cutting edge of human technology, and never fail to inspire. And as astronomers, observatories are the closest thing to a cathedral to the stars that we possess!