April 6, 2020

Review: Discoverers of the Universe by Michael Hoskin.

Few realize that we owe much of our knowledge to an astronomical dynasty of the 18th-19th century. This week, we review Discoverers of the Universe by Michael Hoskin. This fascinating book covers the life and times of astronomers William and Caroline Herschel and the eventual hand off of the mantle of British astronomy to William’s son John. Much has been written about the pursuits of the Herschels, but Discoverers gives it to you in the kind of detail that we observational astronomers love.

[Read more...]

15.03.11: A Borderline Brown Dwarf.

Oh Be A Fine Girl/Guy Kiss Me Now… the mnemonic for stellar classification running from hottest to coldest has been long overdue overhaul, as brown dwarf classes L, T, and now Y have been placed on the cool end of the scale. And in the past month, a paper by Kevin Luhman and colleges at Pennsylvania State University have reported what may be the coolest brown dwarf known.

[Read more...]

01.02.2011: NEOWISE: Mission Accomplished.

An orbiting sentinel recently completed its secondary science mission. WISE, NASA’s Wide-field Infrared Survey Explorer, recently completed an all sky survey for Near Earth Objects (NEOs). Launched in December 2009, WISE’s primary mission was an all sky survey in the infrared spectrum.

[Read more...]

24.06.10: SOFIA takes flight.

A unique airborne telescope is now open for business after what has seemed like endless delays. On May 26th, NASA’s SOFIA, or the Stratospheric Observatory For Infrared Astronomy took flight to perform its first nighttime observations of the far infrared sky. And what a long road to flight it’s been… SOFIA was first proposed in the mid-90’s as a joint German DLR/NASA venture. The primary instrument consists of a 2.5 meter telescope (similar in size to Hubble) positioned perpendicular to the fuselage of a 747SP peering out a retractable cut away opening. SOFIA operates at a wavelength of 0.3 to 1600 microns, and at a cruising altitude of 41,000 feet should give diffraction limited views at wavelengths exceeding 15 microns. SOFIA needs this lofty perch to put it above 99% of the Earth’s water vapor absorbing atmosphere; at these altitudes, seeing is typically in the 2″ to 4″ arc second range. The entire project was brought back from the brink several times; in 2006, the plug was nearly pulled by Congress as the package had just neared completion! Even with cost overruns, flying telescopes aboard planes or balloons is still many times cheaper and easier than placing them into space… SOFIA is the logical predecessor of the Kuiper Airborne Observatory, a 0.9 meter IR telescope that flew aboard a modified C-141 cargo transport from 1974-95. Already, SOFIA is showing its stuff on its first observing runs, and is expected to reach a goal of 150 flights a year by 2014. Service life of SOFIA is expected to be 20 years, again far longer than that of any IR-dedicated space based telescope. SOFIA will operate out of NASA’s Dryden Aircraft Operations Facility near Palmdale, California. The 747 is a special performance (designated by SP) edition, capable of long duration flights and a range of 6,600 miles, ideally suited for the SOFIA mission. Of the 45 747SPs built, only 14 remain flying, from those flown by several Middle Eastern VIPs to the one owned by televangelist Ernest Angley (!) These are marked by the distinctive “stubby” or shortened fuselage design built to cut down weight. Doubtless, SOFIA has been the noblest use of this unique airframe yet…but hey, we are biased towards all things astronomical. You’ve come a long way, baby!


11.06.10: NASA on Insect Patrol.

Terrestrial satellite imagery has found an unlikely application as of late; the tracking of ticks. These fiendish little parasitic insects predominate in the warm, moist environs of the southern United States, latching on to deer, house pets, and perhaps you on that next weekend hiking trip. Often, ticks can dig in and feast without the host even being aware, secreting a numbing neurotoxin as they feed. Perhaps, at most, one may recognize a large “bulls-eye” rash after a few days. Organisms injected into your bloodstream may go on to cause Southern Tick Associated Rash illness, Rocky Mountain spotted fever, and of course the infamous Lyme disease. Caused by a spirochete infection, Lyme disease can lay dormant for years an actually shares some traits with its dreaded medieval cousin, syphilis. Now, researchers at the University of Alabama Birmingham have devised a new method of tracking the seasonal spread of ticks; using data from NASA’s Terra observation satellite, graduate students Stephen Firsing and Nathan Renneboog have been able to pinpoint areas that are likely tick habitats. Ticks like warm moist thick undergrowth; by working with mentors at NASA’s Marshall Space Flight Center, researchers were able to differentiate between 12 distinct types of vegetation as seen on infrared imagery. Nerve center for this operation was the UAB’s Laboratory for Global Health Observation. But the actual “tick hunt” must be conducted the old fashioned way; on the ground. Using the satellite imagery to select likely tick locales, the students then had the unenviable weekend task of dragging the woods with white cloth to perform a tick census. This study should ultimately benefit the tracking and spread of tick borne diseases, which are still relatively new on the medical scene and still poorly understood. This is just another example of space science in action, helping to benefit research on the ground in an unexpected way.

10.06.10: Herschel Celebrates its 1st Year in Space.

While everyone was celebrating Hubble’s 20th this past April, and equally amazing instrument past a quiet milestone: the European Space Agencies’ Herschel Space Observatory passed its first anniversary in space. On May 14, 2009, Herschel was launched as part of a dual payload along with the Planck spacecraft which is in the midst of mapping the cosmic microwave background. Sporting an 11.5 foot mirror (larger than HSTs) Herschel specializes in the far-infrared to submillimeter wavelengths of 55 to 670 microns. To this end, Herschel must be kept “on ice” and is placed at the L2 point in a Lissajous orbit to observe its infrared quarry. This also means that it is well beyond any hope of repair, which will also be the case for the James Webb Space telescope when it’s launched in 2014. An onboard supply of liquid helium keeps the detectors cooled down; cooling of the primary is completed by deployment of an enormous sunshade. Herschel sports three instruments: The PACS (the Photodetecting Array Camera and Spectrometer) and SPIRE (the Spectral and Photometric Imaging Receiver) cameras, and the on-again, off again ultra-high-precision spectrometer (HIFI, or the Heterodyne Instrument for the Far Infrared) detector. Herschel allows us to probe the “cold universe” in ways that would be impossible from the ground. Images such as the famous Horsehead Nebula in the far-infrared have given us key insight as to the inner workings of these dusty regions. In addition, studies have zeroed in on key star forming regions inaccessible from ground based telescopes, such as the enormous RCW 120 interstellar bubble 4,300 light years distant, which may one day collapse into an ultra-massive star. And that’s just the beginning… a proposed program known as ATLAS (the Astrophysical Terahertz Large Area Survey) may utilize Herschel’s capabilities to map a 550 square degree area (about 23.5 degrees on a side) of the sky at five wavelengths as a sort of “Herschel Deep Field” in the submillimeter. Such as task is expected to take up to 600 hours of exposures to complete and uncover perhaps a quarter million primordial galaxies at new wavelengths… Hershel is definitely a platform worth keeping tabs on!

03.06.10: Do “Dirty” White Dwarfs Provide a Key Spectral Signature?


If astronomers at the Leicester University in the United Kingdom are correct, the key elements and chemicals that comprise life may be common throughout our Milky Way. The evidence comes from an unlikely source; spectral examinations of populations of galactic white dwarfs. These ancient remnants of stars exist in vast numbers, and our Sun will indeed share their fate one day. The study, led by researcher Jay Farihi, looked at over 100 million objects in the Sloan Digital Sky Survey, which provides a map of the sky and our galaxy as seen in the infrared spectrum. Their findings conclude that up to 20% of all white dwarfs surveyed are contaminated with trace metals, most likely the result of interplanetary debris. In the field of astronomy, the term “metal” refers to anything that isn’t hydrogen or helium, a little different definition than what you learned (hopefully) in high school chemistry. The thinking goes that where heavier elements are seen, terrestrial planets and perhaps life may be sure to follow. Our Sun itself is a good case in point; a Population I star that is relatively metal rich, allowing for a large retinue of rocky planets, including the Earth. How common or rare we are is still hotly debated, but this analysis of the atmospheres of white dwarfs may prove that terrestrial worlds are perhaps abundant throughout the cosmos.  In terms of this study, astronomers are in a sense looking at the “ruins” of older terrestrial systems that will be recycled and incorporated into new, metal dense populations… perhaps one could argue that as time in universe marches on and heavier elements become more abundant, the odds are that life will become more frequent, at least until the stelliferous era runs its course!

30.05.10: The Faces of Gum 19.

Take a look at the Nebula pictured above. This is the current visual state of affairs of the nebula known as Gum 19, 22,000 light-years distant in the southern constellation Vela. This rich star forming region is pictured in the Digitized Sky Survey above, and the seemingly non-descript Gum 19 Nebula is perched towards center. Using a an infra-red spectrograph known as Sofia coupled to ESO’s New Technology Telescope, astronomers were able to capture Gum 19 as never before. The nebula itself seems to be canted about 90 degrees to our line of sight, hence its two-faced, dark/light appearance. Gum 19 also houses a monster; a supergiant blue star known as V391 Velorum. This tempestuous star illuminates its nebulous surroundings, and has a surface temperature of 50,000°F. Such a beast is not destined to last for long; blue giants typically go supernova within a 10 million year time span. Will V391 be the next visual supernova in our galaxy to pop? Whatever is the case, enjoy the above ESO provided view while you can!

19.04.10- The Rise of WISE.

NASA has a new orbiting infrared eye on the universe. WISE, the Wide-field Infrared Space Explorer, is now open for business, and returning some fairly cool images. Launched out of Vandenberg AFB on December 12th of last year, the telescope is now parked in a sun-synchronous orbit at an inclination of 97.5° degrees. This allows WISE to keep its solar panels in a sunward orientation, while the telescope itself looks off at right angles to the Sun. This will also allow it to image continuous swaths of the sky as it orbits the Earth. WISE sports a 16” 40cm gold-plated mirror (talk about tricked out!) optimized for IR work and will conduct an all-sky survey with an unprecedented resolution across its 47 arc minute field of view. A successor to the IRAS and Spitzer, which ran out of coolant last year, WISE has an on-board supply on frozen hydrogen that should sustain it for a 10 month mission. To perform its mission, WISE must be cooled to -430° F, or about 15 Kelvins. It will also narrow in on possible targets for the James Webb Space telescope to be launched in 2014. JWST is much touted as the “successor to Hubble” but will actually be optimized for work in the infrared as well. IR work is virtually impossible to do from ground based telescopes, due to the absorption of IR wavelengths by water vapor in our atmosphere. Already, WISE has discovered comets, Near Earth objects, and opened a new window on nebulae and star formation… more discoveries to come!

17.04.10- The Case of the Vanishing Moon: Solved.

Since its discovery by Giovanni Cassini in 1671, Saturn’s moon Iapetus has confounded astronomers. Even early on, observers knew something curious was going on with this far off moon; Iapetus varies in brightness between +10 & +12th magnitude as it orbits the ringed planet, nearly vanishing from sight for half its orbit! Late last year, NASA’s Cassini spacecraft and the Spitzer Space Infrared Telescope fingered the culprit; a tenuous outer ring of material now known as the Phoebe Ring that is raining down material on its surface. Like our own Moon, Iapetus is tidally locked in its 79 day orbit. As a consequence, the leading edge plows through this dusty stream of debris. This also causes sunlight to warm and sublimate icy material on the leading side, which streams and re-condenses on the trailing end. This nicely explains the sharply defined and complex boundary seen between the two hemispheres. Alas, no monolith as depicted in Clarke’s original 2001 novel adaptation. .. but perhaps a fine site one day for a cosmic ski resort!

18.03.10: ALMA in Action.

A unique trio of antennae has been successfully installed in the high Chilean desert. ALMA, the Atacama Large Millimeter Array, is a series of 12-meter diameter antennae that will scan the sky between the infrared and radio wavelengths. This area of the spectrum is strongly absorbed by atmospheric water vapor, hence the high and dry locale of 9,500 on the Chanjnantor plateau. Recently, engineers linked the first of three antennae to observe an astronomical source; quasar 1924-292. The link up is crucial to ALMA’s use as an interferometer, and should start producing its first scientific results in 2011. Ultimately, ALMA will be a series of 66 dishes working in unison to probe the cosmos.

27.01.10: As Titan Turns.

Think that this winter is brutal here on Earth? As February is about to set in, we here at Astroguyz invite you to contemplate the seasons on Titan, the largest moon of Saturn. At over 3,000 miles in diameter, Titan is larger than some planets, and possesses an opaque hydro carbon smog veil of an atmosphere. There, a balmy summer day might reach 290°F on the thermometer, and sunshine is a dim murk at best. Scientists have recently found out that this seemingly dismal world is in fact a dynamic place, and a world well worth further scrutiny. The Cassini spacescraft has already conducted fly-bys of the mysterious moon since its orbital insertion in 2004, and even deposited the Huygens probe, which still stands as the most distant soft landing of a manned spacecraft ever made. Now, scientists Emily Schaller of the University of Hawaii and Henry Roe of the Lowell Observatory have been successful in tracking storms in Titan’s turbulent atmosphere. Like Earth, Titan is one of the very few rocky worlds in the solar system that possesses a hydrological cycle and weather. On Titan, however, it rains liquid methane and pools of ammonia dot the surface of this bizarre world. Using the 3-meter Infra-red Telescope Facility, Schaller and Roe monitored Titan 138 nights over 2.2 years in the 2.1 micron range, using the much more sensitive Gemini North telescope also on Mauna Kea for follow up observations when things started to look interesting. Titan is a tough target to image; at its best, it presents a disk no more than 0.8” in diameter. The 2008 storm pictured about demonstrates that Titan is indeed a changing world, one that deserves further examination. Cassini has already performed another flyby of Titan earlier this month on January 12th as part of its mission extension.

21.01.10-Joint U.S.-Mexico Telescope to Survey the Infrared Sky.

Construction has begun on a telescope that will scan a little understood part of the electromagnetic spectrum. Last summer, optical engineers at the University of Arizona in Tucson began the casting process for the 6.5 meter mirror that will ultimately be part of the San Pedro Martir Telescope in the Mexican observatory complex of the same name. Located in Baja, California, the site will offer pristine views of the northern and much of the southern skies.  The mirror is being figured for a very fast, f/1.4 focal ratio for a very special purpose; to complete the most comprehensive survey of the infrared sky. When completed in 2017, the San Pedro Martir Telescope will survey the infrared sky with unprecedented accuracy, going 100 to 500 times fainter than the Two Micron All Sky Survey (2MASS) completed in 2004. This is part of the Synoptic All-Sky Infrared Imaging Survey (SASIR) and will open up a new realm of infrared astronomy. Among the goodies expected to be uncovered are distant quasars, super massive black holes, and perhaps nearby faint red dwarf stars in our own solar neighborhood. For example, the jury is still out on whether or not our own Sun might have a faint, small companion on a long term orbit… now that discovery would be  would be some serious news!

27.07.9: What Ails Jupiter?

Something has slapped the largest planet in our solar system as of late. A large black spot has emerged in Jupiter’s southern polar region, reminiscent of the Shoemaker-Levy 9 collision of 15 years ago. Initially discovered by Anthony Wesley of Australia utilizing a 14.5” reflector early last week, the discovery was backed up mid-week by NASA’s Infrared Telescope Facility in Mauna Kea, Hawaii. Looking similar to a Galilean satellite shadow, it has all the hallmarks of an impact. Will it evolve and develop over the coming weeks and months? By the time this goes to (word)press, we hope to get a glimpse of it here at Florida Astroguyz HQ. [Read more...]