Posted on by Jason Major

First Images in a New Hunt for Dark Energy

Zoomed-in image from the Dark Energy Camera of the barred spiral galaxy NGC 1365, about 60 million light-years from Earth. (Dark Energy Survey Collaboration)

The ongoing search for dark energy now has a new set of eyes: the Dark Energy Camera, mounted on the 4-meter Victor M. Blanco telescope at the National Science Foundation’s Cerro Tololo Inter-American Observatory in Chile. The culmination of eight years of planning and engineering, the phone-booth-sized 570-megapixel Dark Energy Camera has now gathered its very first images, capturing light from cosmic structures tens of millions of light-years away.

Eventually the program’s survey will help astronomers uncover the secrets of dark energy — the enigmatic force suspected to be behind the ongoing and curiously accelerating expansion of the Universe.

Zoomed-in image from the Dark Energy Camera of the Fornax cluster

“The Dark Energy Survey will help us understand why the expansion of the universe is accelerating, rather than slowing due to gravity,” said Brenna Flaugher, project manager and scientist at Fermilab.

Read more: Polar Telescope Casts New Light on Dark Energy

The most powerful instrument of its kind, the Dark Energy Camera will be used to create highly-detailed color images of  a full 1/8th of the night sky — about 5,000 square degrees — surveying thousands of supernovae, galactic clusters and literally hundreds of millions of galaxies, peering as far away as 8 billion light-years.

The survey will attempt to measure the effects of dark energy on large-scale cosmic structures, as well as identify its gravitational lensing effects on light from distant galaxies. The images seen here, acquired on September 12, 2012, are just the beginning… the Dark Energy Survey is expected to begin actual scientific investigations this December.

Full Dark Energy Camera composite image of the Small Magellanic Cloud

“The achievement of first light through the Dark Energy Camera begins a significant new era in our exploration of the cosmic frontier,” said James Siegrist, associate director of science for high energy physics with the U.S. Department of Energy. “The results of this survey will bring us closer to understanding the mystery of dark energy, and what it means for the universe.”

Read more on the Symmetry Magazine article here, and you can also follow the Dark Energy Survey on Facebook here. (The Fermilab press release can be found here.)

Images: Dark Energy Survey Collaboration. Inset image: the 4-meter Blanco Telescope dome at CTIO (NOAO)

The Dark Energy Survey is supported by funding from the U.S. Department of Energy; the National Science Foundation; funding agencies in the United Kingdom, Spain, Brazil, Germany and Switzerland; and the participating DES institutions.

 

Posted on by Jason Major

A New Species of Type Ia Supernova?

Artist’s conception of a binary star system that produces recurrent novae, and ultimately, the supernova PTF 11kx. (Credit: Romano Corradi and the Instituto de Astrofísica de Canarias)

Although they have been used as the “standard candles” of cosmic distance measurement for decades, Type Ia supernovae can result from different kinds of star systems, according to recent observations conducted by the Palomar Transient Factory team at California’s Berkeley Lab.


Judging distances across intergalactic space from here on Earth isn’t easy. Within the Milky Way — and even nearby galaxies — the light emitted by regularly pulsating stars (called Cepheid variables) can be used to determine how far away a region in space is. Outside of our own local group of galaxies, however, individual stars can’t be resolved, and so in order to figure out how far away distant galaxies are astronomers have learned to use the light from much brighter objects: Type Ia supernovae, which can flare up with a brilliance equivalent to 5 billion Suns.

Type Ia supernovae are created from a special pairing of two stars orbiting each other: one super-dense white dwarf drawing material in from a companion until a critical mass — about 40% more massive than the Sun — is reached. The overpacked white dwarf suddenly undergoes a rapid series of thermonuclear reactions, exploding in an incredibly bright outburst of material and energy… a beacon visible across the Universe.

Because the energy and luminance of Type Ia supernovae have been found to be so consistently alike, distance can be gauged by their apparent brightness as seen from Earth. The dimmer one is when observed, the farther away its galaxy is. Based on this seemingly universal similarity it’s been thought that these supernovae must be created under very similar situations… especially since none have been directly observed — until now.

An international team of astronomers working on the Palomar Transient Factory collaborative survey have observed for the first time a Type Ia supernova-creating star pair — called a progenitor system — located in the constellation Lynx. Named PTF 11kx, the system, estimated to be some 600 million light-years away, contains a white dwarf and a red giant star, a coupling that has not been seen in previous (although indirect) observations.

“It’s a total surprise to find that thermonuclear supernovae, which all seem so similar, come from different kinds of stars,” says Andy Howell, a staff scientist at the Las Cumbres Observatory Global Telescope Network (LCOGT) and a co-author on the paper, published in the August 24 issue of Science. “How could these events look so similar, if they had different origins?”

The initial observations of PTF 11kx were made possible by a robotic telescope mounted on the 48-inch Samuel Oschin Telescope at California’s Palomar Observatory as well as a high-speed data pipeline provided by the NSF, NASA and Department of Energy. The supernova was identified on January 16, 2011 and supported by subsequent spectrography data from Lick Observatory, followed up by immediate “emergency” observations with the Keck Telescope in Hawaii.

“We basically called up a fellow UC observer and interrupted their observations in order to get time critical spectra,” said Peter Nugent, a senior scientist at the Lawrence Berkeley National Laboratory and a co-author on the paper.

The Keck observations showed the PTF 11kx post-supernova system to contain slow-moving clouds of gas and dust that couldn’t have come from the recent supernova event. Instead, the clouds — which registered high in calcium in the Lick spectrographic data — must have come from a previous nova event in which the white dwarf briefly ignited and blew off an outer layer of its atmosphere. This expanding cloud was then seen to be slowing down, likely due to the stellar wind from a companion red giant.

(What’s the difference between a nova and a supernova? Read NASA’s STEREO Spots a New Nova)

Eventually the decelerating nova cloud was impacted by the rapidly-moving outburst from the supernova, evidenced by a sudden burst in the calcium signal which had gradually diminished in the two months since the January event. This calcium burst was, in effect, the supernova hitting the nova and causing it to “light up”.

The observations of PTF 11kx show that Type Ia supernova can occur in progenitor systems where the white dwarf has undergone nova eruptions, possibly repeatedly — a scenario that many astronomers had previously thought couldn’t happen. This could even mean that PTF 11kx is an entirely new species of Type Ia supernova, and while previously unseen and rare, not unique.

Which means our cosmic “standard candles” may need to get their wicks trimmed.

“We know that Type 1a supernovae vary slightly from galaxy to galaxy, and we’ve been calibrating for that, but this PTF 11kx observation is providing the first explanation of why this happens,” Nugent said. “This discovery gives us an opportunity to refine and improve the accuracy of our cosmic measurements.”

Source: Berkeley Lab news center

Inset images: PTF 11kx observation (BJ Fulton, Las Cumbres Observatory Global Telescope Network) / The 48-inch Samuel Oschin Telescope dome at Palomar Observatory. Video: Romano Corradi and the Instituto de Astrofísica de Canarias

Posted on by Jason Major

Canada Unveils its Contributions to the JWST

Today Canada’s Minister of Industry Christian Paradis unveiled the technologies that comprise Canada’s contribution to the James Webb Space Telescope, a next-generation infrared observatory that’s seen as the successor to Hubble.


CSA will provide JWST with a two-in-one instrument: a Fine Guidance Sensor (FGS) Near-Infrared Imager and Slitless Spectrograph (NIRISS). Both were designed, built and tested by COM DEV International in Ottawa and Cambridge, Ontario, with technical contributions from the Université de Montréal and the National Research Council Canada.

Read: Watch the James Webb Being Built via “Webb-Cam”

“Canada has a proud legacy in space and we are once again pushing the frontier of what is possible. These two outstanding technologies are perfect examples of how Canada has secured its world-class reputation. Our Government is committed to ensuring the long-term competitiveness and prosperity of such a vital economic sector.”
– The Honourable Christian Paradis

The FGS consists of two identical cameras that are critical to Webb’s ability to “see.” Their images will allow the telescope to determine its position, locate its celestial targets, and remain pointed to collect high-quality data. The FGS will guide the telescope with incredible precision, with an accuracy of one millionth of a degree.

The NIRISS will have unique capabilities for finding the earliest and most distant objects in the Universe’s history. It will also peer through the glare of nearby young stars to unveil new Jupiter-like exoplanets. It will have the capability of detecting the thin atmosphere of small, habitable, earth-like planets and determine its chemical composition to seek water vapour, carbon dioxide and other potential biomarkers such as methane and oxygen.

The FGS/NIRISS instruments can be seen in this development video from CSA:

“Imagine the challenge at hand here: to design and deliver technology capable of unprecedented levels of precision to conduct breakthrough science on board the largest, most complex and most powerful telescope ever built,” said Steve MacLean, President of the CSA. “The Webb telescope will be located 1.5 million kilometers from Earth— too far to be serviced by astronauts like Hubble was. At that distance, the technology simply has to work. This is the outstanding level of excellence Canadians are capable of achieving. It’s something for all of us to be proud of.”

The instruments will be delivered to NASA on July 30.

Read more on the CSA press release here, and learn more about the James Webb here.

Images/video: CSA and NASA

Posted on by Jason Major

Pulsar Sets New Speed Record

A pulsar may have been spotted racing through space at over 6 million miles per hour (9.65 million km/h), setting a new speed record for these curious cosmic objects. If observations are what they appear to be, astronomers will have to recalculate the incredible forces created by supernova explosions.

Seen in observations made with 3 different telescopes — NASA’s Chandra X-ray Observatory, ESA’s XMM-Newton, and the Parkes radio telescope in Australia — the x-ray-emitting object IGR J11014-6103 appears to be racing away from the remnants of a supernova in the constellation Carina, 30,000 light-years from Earth.

The comet-shaped object is thought to be a pulsar, the rapidly-spinning, superdense remains of a star. The facts that it’s dim in optical and infrared wavelengths and hasn’t changed in x-ray brightness between XMM-Newton observations in 2003 and Chandra measurements in 2011 support the claim.

IGR J11014’s comet-like shape may be the result of its breakneck speed through space as its pulsar wind nebula gets blown back by the high-energy bow shock created at the forefront of its passage.

Pulsar wind nebulae are the results of charged particles streaming out from the pulsar itself. The particles, traveling at nearly light-speed, are rapidly decelerated by the interstellar medium and create a visible shock wave. In the case of IGR J11014, the pulsar wind is formed into a “tail” by its bow shock — effectively a sonic boom in front of it.

Further observations will be needed to confirm that IGR J11014 is indeed a pulsar, especially considering that actual pulsations have not yet been detected. If it is a pulsar, and is really traveling at the record-breaking speeds it appears to be — between 5.4 and 6.5 million miles per hour, more than 12 times faster than the Sun travels around the center of the galaxy — a new model of supernova explosions may be required.

Read more on the Chandra news release here.

Image: X-ray: NASA/CXC/UC Berkeley/J.Tomsick et al & ESA/XMM-Newton, Optical: DSS; IR: 2MASS/UMass/IPAC-Caltech/NASA/NSF. Video: NASA/CXC/A. Hobart.

Posted on by Jason Major

James Webb Mirrors Pass Deep-Freeze Exams

The James Webb Space Telescope mirrors have completed deep-freeze tests and are removed from the X-ray and Cryogenic test Facility at Marshall Space Flight Center. Credit: Emmett Given, NASA Marshall

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The last of the 21 mirrors for the James Webb Space Telescope have come out of deep freeze – literally! – and are now approved for space operations, a major milestone in the development of the next generation telescope that’s being hailed as the “successor to Hubble.”

“The mirror completion means we can build a large, deployable telescope for space,” said Scott Willoughby, vice president and Webb program manager at Northrop Grumman Aerospace Systems. “We have proven real hardware will perform to the requirements of the mission.”

The all-important mirrors for the Webb telescope had to be cryogenically tested to make sure they could withstand the rigors and extreme low temperatures necessary for operating in space. To achieve this, they were cooled to temperatures of -387F (-233C) at the X-ray and Cryogenic Test Facility at Marshall Space Flight Center.

When in actual use, the mirrors will be kept at such low temperatures so as not to interfere with deep-space infrared observations with their own heat signatures.

JWST engineers anticipate that, with such drastic cooling, the mirrors will change shape. The testing proved that the mirrors would achieve the shapes needed to still perform exactly as expected.

“This testing ensures the mirrors will focus crisply in space, which will allow us to see new wonders in our universe,” said Helen Cole, project manager for Webb Telescope mirror activities.

Planned for launch in 2018, the JWST will be the premier observatory of the next decade, serving thousands of astronomers worldwide. It will study every phase in the history of the Universe, ranging from the first luminous glows after the Big Bang to the formation of solar systems capable of supporting life on Earthlike planets.

Learn more about the James Webb Space Telescope here.

Posted on by Jason Major

Underwater Neutrino Detector Will Be Second-Largest Structure Ever Built

Artist's rendering of the KM3NeT array. (Marco Kraan/Property KM3NeT Consortium)

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The hunt for elusive neutrinos will soon get its largest and most powerful tool yet: the enormous KM3NeT telescope, currently under development by a consortium of 40 institutions from ten European countries. Once completed KM3NeT will be the second-largest structure ever made by humans, after the Great Wall of China, and taller than the Burj Khalifa in Dubai… but submerged beneath 3,200 feet of ocean!

KM3NeT – so named because it will encompass an area of several cubic kilometers – will be composed of lengths of cable holding optical modules on the ends of long arms. These modules will stare at the sea floor beneath the Mediterranean in an attempt to detect the impacts of neutrinos traveling down from deep space.

Successfully spotting neutrinos – subatomic particles that don’t interact with “normal” matter very much at all, nor have magnetic charges – will help researchers to determine which direction they originated from. That in turn will help them pinpoint distant sources of powerful radiation, like quasars and gamma-ray bursts. Only neutrinos could make it this far and this long after such events since they can pass basically unimpeded across vast cosmic distances.

“The only high energy particles that can come from very distant sources are neutrinos,” said Giorgio Riccobene, a physicist and staff researcher at the National Institute for Nuclear Physics. “So by looking at them, we can probe the far and violent universe.”

Each Digital Optical Module (DOM) is a standalone sensor module with 31 3-inch PMTs in a 17-inch glass sphere.

In effect, by looking down beneath the sea KM3NeT will allow scientists to peer outward into the Universe, deep into space as well as far back in time.

The optical modules dispersed along the KM3NeT array will be able to identify the light given off by muons when neutrinos pass into the sea floor. The entire structure would have thousands of the modules (which resemble large versions of the hovering training spheres used by Luke Skywalker in Star Wars.)

In addition to searching for neutrinos passing through Earth, KM3NeT will also look toward the galactic center and search for the presence of neutrinos there, which would help confirm the purported existence of dark matter.

Read more about the KM3NeT project here, and check out a detailed article on the telescope and neutrinos on Popsci.com.

Height of the KM3NeT telescope structure compared to well-known buildings

Images property of KM3NeT Consortium 

Posted on by Jason Major

Asteroid 2005 YU55: See It For Yourself!

Passage of of 2005 YU55 near Altair from 6:03 p.m. – 6:12 p.m. EST (11:03 – 11:12 UTC)

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It’s already been stated several times here on Universe Today that 2005 YU55, a 400-meter-wide roughly spherical asteroid, will not pose any threat to Earth as it passes by on Tuesday, November 8… even though it will come within 80% of the distance to the Moon. Many experts have come forward to state this fact, including Don Yeomans of JPL’s Near-Earth Object Observation Program and Lance Benner, a radio astronomer with the Deep Space Network in Goldstone, CA.  But it will still be a notable event, being the first time since 1976 such a large object will pass so closely by our planet. So, with the eve of YU55’s approach upon us, let’s turn our curiosity toward another aspect of this cosmic visitation: how can we see it?

Unfortunately there are a couple of factors working against the casual observer being able to witness YU55’s pass. One: it’s a dark object. A very dark object. 2005 YU55 is a C-type asteroid, which means it is composed of carbonaceous material and is thus effectively darker than coal, reflecting less than 1% of the sunlight that it receives. It probably won’t be brighter than magnitude 10. (On the backwards-ranked scale of apparent magnitude, 6 is the limit of best visibility to the average human eye, while -1 or 0 would be a very bright star. Jupiter is about -3 right now, while the full moon would be -12.7. In a typical suburban neighborhood 3 or 4 is the limit of naked-eye visibility.)

And two: the Moon will be close to full on the night of the 8th, and YU55 will be headed in its direction. That sure won’t help visibility.

But, should you be located in a dark area, and should you have a 6″ or larger telescope at your disposal, you may want to give a go at spotting the asteroid that’s caused quite a fuss over the past few months for yourself. It won’t be a simple task, but it’s not impossible – and to help you out teacher, writer and astronomy enthusiast David Dickinson has posted an article about it on his blog, Astro Guyz.

Here’s an exerpt:

Closest approach to Earth occurs at 11:29 UTC/06:29 EST at about 202,000 miles distant, placing it high to the southwest for observers on the US Eastern Seaboard. At its closest approach, 2005 YU55 will glide along at one degree every 7 minutes, easily noticeable after a few minutes of observation at low power. I plan to target selected areas with my GOTO mount, sketch the field, then watch for changes. I may also take some wide-field piggyback stills with the DSLR, but mostly, this one will just be fun to watch.

Visually tracking a Near-Earth asteroid can be thrilling to watch; for example, I’ve actually seen 4179 Toutatis years ago show discernable movement after tracking it for a few moments in the eyepiece!

– David Dickinson

Wide field finder of 2005 YU55 from sunset until 8:30PM EST.

The asteroid will pass through the constellations Aquila, Delphinus, and Pegasus as it heads westward. Interestingly, 2005 YU55 passes within a degree of Altair centered on 6:07:30PM EST only 27 minutes after local sunset, and also makes a very close pass of the star Epsilon Delphini during closest approach. These both make good visual “anchors” to aim your scope at during the appointed time and watch. Keep in mind, the charts provided are rough and “Tampa Bay-centric…”

On an approach as close as this one, two factors muddle the precise prediction coordinates of the asteroid; one is the fact the gravitational field of the Earth will change the orbit of 2005 YU55 slightly, and two is that the position will change due to the position of the observer on the Earth and the effect of parallactic shift. Many prediction programs assume the Earthly vantage as a mere point in space, fine for positioning deep sky objects but not so hot for ones passing near the planet. A good place to get updated coordinates is JPL Horizons website which lets you generate an accurate ephemeris for your exact longitude latitude and elevation.

David goes on to add:

2005 YU55 will pass our Moon at 8 AM Universal Time on November 9th at a distance only marginally closer than it did the Earth, at 140,000 miles. Interestingly, it also transited Sun on November 3rd as seen from the Moon, but would have appeared <1” in size, a tough target for any would-be lunar-based observer. Its next close predicted passage of the Earth won’t be until 2056 at nearly 3 times the distance.

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Excellent information… many thanks to David for sharing with us! (You can read the full article on his website here.) And if you do witness the pass of this asteroid and somehow manage to get some photos of it, you can share them on the Universe Today Flickr group… they may be featured in an upcoming article!

Read more about 2005 YU55’s close pass by Earth tomorrow.

Charts and excerpts by David Dickinson, created with Starry Night and Paint.

 

Posted on by Jason Major

Senate Approves Bill Funding JWST

Full scale model of the JWST at the EADS Astrium in Munich. Credit: EADS Astrium

This afternoon the U.S. Senate approved H.R. 2112, a FY 2012 bill from Maryland Senator Barbara Mikulski that would fund the James Webb Space Telescope to launch in 2018. This is another step forward for the next-generation space telescope, which many have called the successor to Hubble… all that now remains is for the House to reconcile.

“We are creating the building blocks that we need for a smarter America. Our nation is in an amazing race – the race for discovery and new knowledge, the race to remain competitive,” Chairwoman Mikulski said. “This bill includes full funding of the James Webb Telescope to achieve a 2018 launch. The Webb Telescope supports 1,200 jobs and will lead to the kind of innovation and discovery that have made America great. It will inspire America’s next generation of scientists and innovators that will have the new ideas that lead to new products and new jobs.”

Full scale model of the JWST at the EADS Astrium in Munich. Credit: EADS Astrium

The bill was approved by a vote of 69 to 30.

Thanks to everyone who contacted their representatives in support of the JWST and to all the websites out there that helped make it simple to do so… and of course to all the state representatives who listened and stood behind the JWST!

In addition to continued funding for the telescope the 2012 bill also allots the National Aeronautics and Space Administration $17.9 billion (still a reduction of $509 million or 2.8 percent from the 2011 enacted level) and preserves NASA’s portfolio balanced among science, aeronautics, technology and human space flight investments, including the Orion Multipurpose Crew Vehicle, the heavy lift Space Launch System, and commercial crew development.

It also supports funding for the NOAA.

“We are creating the building blocks that we need for a smarter America. Our nation is in an amazing race – the race for discovery and new knowledge, the race to remain competitive.”

– U.S. Senator Barbara A. Mikulski

Of course, we must remember that spending and allocation of funds is not necessarily creating funds. As with everything, money has to come from somewhere and it remains to be seen how this will affect other programs within NASA. Not everyone is in agreement that this is the best course of action for the Administration at this point, not with the overall reduction of budget being what it is.

Read the bill summary here.

You can show your continued support for the JWST by liking the Save the James Webb Space Telescope Facebook page and – even more importantly – by contacting your congressperson and letting them know you care!

Posted on by VirtualAstro

Beginner’s Guide to Astronomy – Refractor Telescopes

If you ask someone to describe or draw a telescope, nine times out of ten it will be a refractor.

The refractor telescope is quite possibly the most common or easily recognized telescope. It is a very simple design, which has been around for hundreds of years.

The history of the refractor is that it was first invented in the Netherlands in 1608, and is credited to 3 individuals; Hans Lippershey, Zacharias Janssen – spectacle-makers and Jacob Metius.

In 1609 Galileo Galilei heard about the refracting telescope and made his own design, publically announcing his invention and further developing it through extensive experimentation. Galileo’s friend Johannes Kepler further experimented with the design, introducing convex lenses at both ends, improving the operation of the telescope.

Many advances were made and the refracting telescope became the primary instrument for astronomical observations, but there was one problem; they were huge and some were many tens of feet long!

But now, after more than 400 years and — luckily — through advances in know-how and technology, the refractor has become much more powerful and compact than some of the behemoths in the early days.

Refractors or refracting telescopes employ a simple optical system comprising of a hollow tube with a large primary or “objective lens” at one end, which refracts light collected by the objective lens and bends light rays to make them converge at a focal point.

Light waves which enter at an angle converge on the focal plane. It is the combination of both which form an image that is further refracted and magnified by a secondary lens which is actually the eyepiece. Different eyepieces give different magnifications.

The larger the size of the objective or primary lens = more light gathered. So a 6 inch refractor gathers more light than a 2 inch one. This means more detail can be seen.

There are two main types of refractor telescopes: “Chromatic” – entry level and upwards with 2 lens elements and “Apochromatic” – premium, advanced and expert level telescopes with 3 or more very high quality lens elements with exotic mixes of materials.

Chromatic refractor telescopes are particularly good for observing bright objects such as the moon, planets and resolving things like double stars, but many astronomers who image deep sky and other objects use very high quality apochromatic refractors, due to their superior optics.

Refractor telescopes are very low maintenance due to being a sealed system and it is a simple case of setup and enjoy, without the fiddling lengthy setup times you may get with other telescopes.

Refractors give clean and crisp views due to the sealed nature, unlike other telescopes like Newtonians which are subject to cooling and air turbulence issues.

Due to their small size they are very portable and can also be used for terrestrial observations the same as binoculars, which are basically two refractors bolted together.

Posted on by Matt Williams

Convex Lens

Convex Lens

As every child is sure to find out at some point in their life, lenses can be an endless source of fun. They can be used for everything from examining small objects and type to focusing the sun’s rays. In the latter case, hopefully they choose to be humanitarian and burn things like paper and grass rather than ants! But the fact remains, a Convex Lens is the source of this scientific marvel. Typically made of glass or transparent plastic, a convex lens has at least one surface that curves outward like the exterior of a sphere. Of all lenses, it is the most common given its many uses.

A convex lens is also known as a converging lens. A converging lens is a lens that converges rays of light that are traveling parallel to its principal axis. They can be identified by their shape which is relatively thick across the middle and thin at the upper and lower edges. The edges are curved outward rather than inward. As light approaches the lens, the rays are parallel. As each ray reaches the glass surface, it refracts according to the effective angle of incidence at that point of the lens. Since the surface is curved, different rays of light will refract to different degrees; the outermost rays will refract the most. This runs contrary to what occurs when a divergent lens (otherwise known as concave, biconcave or plano-concave) is employed. In this case, light is refracted away from the axis and outward.

Lenses are classified by the curvature of the two optical surfaces. If the lens is biconvex or plano-convex, the lens is called positive or converging. Most convex lenses fall into this category. A lens is biconvex (or double convex, or just convex) if both surfaces are convex. These types of lenses are used in the manufacture of magnifying glasses. If both surfaces have the same radius of curvature, the lens is known as an equiconvex biconvex. If one of the surfaces is flat, the lens is plano-convex (or plano-concave depending on the curvature of the other surface). A lens with one convex and one concave side is convex-concave or meniscus. These lenses are used in the manufacture of corrective lenses.

For an illustrated example of how images are formed with a convex lens, click here.

We have written many articles about lenses for Universe Today. Here’s an article about the concave lens, and here’s an article about telescope lens.

If you’d like more info on convex lens, check out these articles from The Physics Classroom and Wikipedia.

We’ve also recorded an episode of Astronomy Cast all about the Telescope. Listen here, Episode 33: Choosing and Using a Telescope.

Sources:
http://en.wikipedia.org/wiki/Lens_(optics)
http://homepage.mac.com/cbakken/obookshelf/cvreal.html
http://www.play-hookey.com/optics/lens_convex.html
http://www.answers.com/topic/convex-lens-1
http://www.physicsclassroom.com/class/refrn/u14l5a.cfm
http://www.tutorvista.com/content/science/science-ii/refraction-light/formation-convex.php