October 21, 2018

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!

15.05.10: A Speedy Binary.

Think that new Ducati in your garage is fast? Let me introduce you to HM Cancri. An unassuming +21 magnitude binary in the constellation Cancer, HM Cancri is comprised of two white dwarfs locked in a tight embrace. In fact, this binary system has the shortest orbital period known, handily knocking down distant contender V407 Vulpeculae with its “stately” 9.5 minute orbit. The facts are dizzying; the pair weigh in at 0.5 and 0.25 solar masses respectively, are about 24,000 miles apart (think geosynchronous orbit!) and revolve around each other in 5.4 minutes, about the time you hopefully spend glancing over this blog before returning to Facebook.  Get your calculators out; this makes orbital velocity for the pair an impressive 230 miles per second! Discovered in 1999, Observations using the Keck telescope have upheld HM Cancri’s record holding status by analyzing opposing spectral shifts of ionized helium as the two stars whirl about. This rules out other candidates such as a single neutron star.  Such a system must have had a very unique history, perhaps starting as a pair of Sun-like stars that later spiraled in. Will the two merge one day? Conservation of angular momentum cannot fully explain what we see as the system is speeding up; perhaps more accreting matter is present than we currently account for. The pair are approaching each other by about two feet per day, and of course, relativity comes into play in such an extreme system. Clearly, something interesting is occurring in this system. HM Cancri is also a strong x-ray source, and should generate copious amounts of gravity waves, especially in the event of a merger. Said waves may be within the realm of Advanced LIGO, due to come online in 2014, or LISA, ESA’s proposed Laser Interferometer Space Antenna. HM Cancri lies about 16,000 light years distant, and may be the strongest source of gravity waves in our galaxy.

30.10.09:The World’s Largest Telescope is Unveiled.

Move over Keck… the world’s largest telescope is now in service! The Gran Telescopio Canaris (GTC) was commissioned this summer on July 24th. Perched on La Palma island in the Canary Islands, this beast sports a 10.4-meter segmented mirror. This gives it a collection area over 6 square meters larger than contending 8 to 10 meter instruments world-wide. A joint effort of Spain, Mexico, and the University of Florida, this instrument is expected to further push back our understanding of the frontiers of astronomy. Of course, as reported earlier, bigger scopes are on the drawing board; but as astronomy moves out beyond the Earth’s atmosphere, the age of the terrestrial mega-scope may be coming to an end in our lifetime. Scopes like the GTC rely of computer sensors to keep its 36 mirror segments aligned and acting as one. This is much easier than the old school method of casting one giant parabolic mirror, which would be cumbersome and nearly impossible from an engineering standpoint. The GTC sits at an altitude of 2,400 meters, well above a good bulk of the blurring atmosphere. Other scopes, such as the Large Binocular Telescope (LBT) on Mount Graham, Arizona, rely on a technique known as interferometry to increase resolution. This places two telescopes along a precisely measured base line, and thus provides the resolution of one large mirror. Terrestrial scopes up to 100 meters (!) in size have been proposed and are on the drawing board…let the scope wars begin!

13.10.09:A Hawaiian Mega-scope?

The green light was given earlier this year in mid-July as to the site selection for a telescope that if built, will be the largest in the world. The Thirty Meter Telescope (TMT) will be parked atop Mauna Kea in Hawaii, home to a collection of scopes, including the Keck, Subaru, and Gemini instruments. As its name suggests, this telescope will sport a reflecting 30 meter mirror comprised of 492 hexagonal segments and operate in the near infrared as well as visible light. Its to be seen whether this will move the environmental lobby to protest as construction on Mauna Kea did in 2002. A point often missed in these debates is that the telescopes themselves need pristine dark skies to operate; this assures that over-development in the form of Costcos and subdivisions won’t visit the slopes of Mauna Kea anytime soon. A follow-up contender for the TMT is Mt. Cerro Armazones in the Atacama Desert in Chile, also dubbed the “most eligible mountain without an observatory.” The seeing is also a bit better in the Atacama, but of course that would mean the exodus of more American science (and dollars) overseas. The European Union is also eying Armazones for a possible site for its two main contenders: the Giant Magellan Telescope (GMT) at 24.5 meters, and the European Extremely Large Telescope (EELT) at a whooping 42 meters. Its sobering to think that these mega scopes may be the final say of large aperture on Earth; at a proposed 2 billion dollars to build the TMT, it becomes more cost effective to carry on further “aperture wars” in space!

09.10.09: An LCROSS Update.

NASA’s LCROSS spacecraft performed its promised “moon crash” early this AM at 0731 AM EDT… all eyes, electronic and otherwise were on Cabeus crater. Unfortunately, no impact was detected here at Astroguyz HQ in Hudson, Florida, although we did have a rising Sun and a brightening sky to contend with. The 10 AM news conference at the Ames research center revealed that the secondary control module of LCROSS did detect the impact in both UV and IR signatures as well as a visual fix on the crater created by the Centaur booster. The controller itself met its fiery end four minutes later. Ground based observatories from Apache Point, New Mexico to the Keck telescopes in Hawaii to observatories in South Korea as well as Hubble, LRO, and Sweden’s ODIN in orbit all gathered data. Its to be seen if any amateur ‘scopes recorded this event. Kitt Peak did record a sodium flash during the event. Of course, the data itself will need to be compiled and analyzed before any meaningful scientific conclusions can be done…I smell a follow up post! Kudos to all that woke up early to look at our nearest neighbor in space, as well as NASA scientists that are no doubt now getting some much needed sleep!