Stars Archives

July 9, 2012December 23, 2015 by Jason Major

NASA To Launch The Finest Mirrors Ever Made

This Wednesday NASA will launch its High Resolution Coronal Imager (HI-C) mission from White Sands Missile Range in New Mexico, sending a sounding rocket above the atmosphere with some of the best mirrors ever made to capture incredibly-detailed ultraviolet images of our Sun.

HI-C will use a state-of-the-art imaging system to focus on a region near the center of the Sun about 135,000 miles (271,000 km) across. During its brief flight — only ten minutes long — HI-C will return some of the most detailed images of the Sun’s corona ever acquired, with a resolution five times that of previous telescopes… including NASA’s Solar Dynamics Observatory.

While SDO collects images in ten wavelengths, however, HI-C will focus on just one: 193 Angstroms, a wavelength of ultraviolet radiation that best reveals the structures of the Sun’s corona present in temperatures of 1.5 million kelvin. And although HI-C’s mirrors aren’t any larger than SDO’s — about 9.5 inches in diameter — they are “some of the finest ever made.” In addition, an interior “maze” between mirrors effectively increases HI-C’s focal length.

Researchers expect HI-C’s super-smooth mirrors to resolve coronal structures as small as 100 miles (160 km) across (0.1 arcsec/pixel).

“Other instruments in space can’t resolve things that small, but they do suggest – after detailed computer analysis of the amount of light in any given pixel – that structures in the sun’s atmosphere are about 100 miles across,” said Jonathan Cirtain, project scientist for HI-C at NASA’s Marshall Space Flight Center. “And we also have theories about the shapes of structures in the atmosphere, or corona, that expect that size. HI-C will be the first chance we have to see them.”

One of the main goals of HI-C will be to place significant new constraints on theories of coronal heating and structuring, by observing the small-scale processes that exist everywhere in hot magnetized coronal plasma and establishing whether or not there are additional structures below what can currently be seen.

“This instrument could push the limits on theories of coronal heating, answering questions such as why the temperature of the sun’s corona is millions of degrees higher than that of the surface,” said Marshall’s Dr. Jonathan Cirtain, heliophysicist and principle investigator on the mission.

Read more on the NASA news release here.

Top image: A Black Brant sounding rocket containing NASA’s HI-C mission will launch on July 11, 2012 to observe the sun’s corona. (NASA) Bottom image: TRACE image of the Sun at a resolution of 0.5 arcsec/pixel. HI-C will have a resolution 5 times finer.

July 6, 2012December 23, 2015 by Jason Major

The Last Outbursts of a Dying Star

As stars approach the inevitable ends of their lives they run out of stellar fuel and begin to lose a gravitational grip on their outermost layers, which can get periodically blown far out into space in enormous gouts of gas — sometimes irregularly-shaped, sometimes in a neat sphere. The latter is the case with the star above, a red giant called U Cam in the constellation Camelopardalis imaged by the Hubble Space Telescope.

From the Hubble image description:

U Cam is an example of a carbon star. This is a rare type of star whose atmosphere contains more carbon than oxygen. Due to its low surface gravity, typically as much as half of the total mass of a carbon star may be lost by way of powerful stellar winds. Located in the constellation of Camelopardalis (The Giraffe), near the North Celestial Pole, U Cam itself is actually much smaller than it appears in Hubble’s picture. In fact, the star would easily fit within a single pixel at the center of the image. Its brightness, however, is enough to saturate the camera’s receptors, making the star look much bigger than it really is.

The shell of gas, which is both much larger and much fainter than its parent star, is visible in intricate detail in Hubble’s portrait. While phenomena that occur at the ends of stars’ lives are often quite irregular and unstable, the shell of gas expelled from U Cam is almost perfectly spherical.

Image credit: ESA/NASA

July 6, 2012April 26, 2016 by Nancy Atkinson

“Impossible” Binary Star Systems Found

Astronomers think about half of the stars in our Milky Way galaxy are, unlike our Sun, part of a binary system where two stars orbit each other. However, they’ve also thought there was a limit on how close the two stars could be without merging into one single, bigger star. But now a team of astronomers have discovered four pairs of stars in very tight orbits that were thought to be impossibly close. These newly discovered pairs orbit each other in less than 4 hours.

Over the last three decades, observations have shown a large population of stellar binaries, and none of them had an orbital period shorter than 5 hours. Most likely, the stars in these systems were formed close together and have been in orbit around each other from birth onwards.

A team of astronomers using the United Kingdom Infrared Telescope (UKIRT) in Hawaii made the first investigation of red dwarf binary systems. Red dwarfs can be up to ten times smaller and a thousand times less luminous than the Sun. Although they form the most common type of star in the Milky Way, red dwarfs do not show up in normal surveys because of their dimness in visible light.

But astronomers using UKIRT have been monitoring the brightness of hundreds of thousands of stars, including thousands of red dwarfs, in near-infrared light, using its state-of-the-art Wide-Field Camera (WFC).

“To our complete surprise, we found several red dwarf binaries with orbital periods significantly shorter than the 5 hour cut-off found for Sun-like stars, something previously thought to be impossible,” said Bas Nefs from Leiden Observatory in the Netherlands, lead author of the paper which was published in journal Monthly Notices of the Royal Astronomical Society. “It means that we have to rethink how these close-in binaries form and evolve.”

Since stars shrink in size early in their lifetime, the fact that these very tight binaries exist means that their orbits must also have shrunk as well since their birth, otherwise the stars would have been in contact early on and have merged. However, it is not at all clear how these orbits could have shrunk by so much.

One possible scenario is that cool stars in binary systems are much more active and violent than previously thought.

The astronomers said it is possible that the magnetic field lines radiating out from the cool star companions get twisted and deformed as they spiral in towards each other, generating the extra activity through stellar wind, explosive flaring and star spots. Powerful magnetic activity could apply the brakes to these spinning stars, slowing them down so that they move closer together.

“The active nature of these stars and their apparently powerful magnetic fields has profound implications for the environments around red dwarfs throughout our Galaxy, ” said team member said David Pinfield from the University of Hertfordshire.

UKIRT has a 3.8 meter diameter mirror, and is the second largest dedicated infrared telescope in the world. It sits at an altitude of 4,200 m on the top of the volcano Mauna Kea on the island of Hawaii.

Read the team’s paper.

Lead image caption: This artist’s impression shows the tightest of the new record breaking binary systems. Two active M4 type red dwarfs orbit each other every 2.5 hours, as they continue to spiral inwards. Eventually they will coalesce into a single star. Credit: J. Pinfield.

July 5, 2012December 23, 2015 by Jason Major

The Case of the Disappearing Dust

Astronomy has always taught us that planets form from vast clouds of dust and gas orbiting young stars. It’s a gradual process of accretion that takes hundreds of thousands, perhaps even millions, of years… or does it?

During a 1983 sky survey with the Infrared Astronomical Satellite (IRAS) astronomers identified a young Sun-like star with a large cloud of dust surrounding it. The star, named TYC 8241 2652 1, is 450 light years away and what they had found around it was thought to be the beginnings of a solar system – the protoplanetary disc from which planets form.

Fast forward to 2008. Astronomers observed at the same star with a different infrared telescope, the Gemini South Observatory in Chile. What was observed looked a lot like what was previously seen in ’83.

Then, in 2009, they looked again. Curiously, the brightness of the dust cloud was only a third of what it was the year before. And in WISE observations made the very next year, it had disappeared entirely.

“It’s like the classic magician’s trick: now you see it, now you don’t. Only in this case we’re talking about enough dust to fill an inner solar system, and it really is gone.”

– Carl Melis, lead author and postdoctoral fellow at UC San Diego

Abracadabra?

“It’s as if you took a conventional picture of the planet Saturn today and then came back two years later and found that its rings had disappeared,” said study co-author and circumstellar disk expert Ben Zuckerman of UCLA.

It’s always been thought that planets take some time to form, in the order of hundreds of thousands of years. Although that may seem like forever to humans, it’s quick in cosmic time scales. But if what they’ve seen here with TYC 8241 is in fact planetary formation, well… it may happen a lot faster than anyone thought.

On the other hand, the star could have somehow blown all the dust out of the system. More research will be needed to see if that was the case.

The really interesting thing here is that astronomers have traditionally looked for these kinds of dust clouds around stars to spot planetary formation in action. But if planets form quicker than we thought, and the dust clouds are only fleeting features, then there may be a lot more solar systems out there that we can’t directly observe.

“People often calculate the percentage of stars that have a large amount of dust to get a reasonable estimate of the percentage of stars with planetary systems, but if the dust avalanche model is correct, we cannot do that anymore,” said study co-author Inseok Song, assistant professor of physics and astronomy at the University of Georgia. “Many stars without any detectable dust may have mature planetary systems that are simply undetectable.”

Top image: Gemini Observatory/AURA artwork by Lynette Cook.

July 5, 2012December 23, 2015 by Jason Major

WISE Spies a Hunter’s Flame

A vast star-forming cloud of gas and dust in the constellation Orion shines brightly in this image from NASA’s WISE space telescope, where infrared light is represented in visible wavelengths. It’s part of a recent data release from WISE, a trove of infrared images acquired during the telescope’s second sky scan from August to September of 2010 — just as it began to run out of its essential cryogenic coolant.

Shining brightly in infrared radiation, the Flame nebula (NGC 2024) is at the heart of the cloud. Just below it is the reflection nebula NGC 2023, and the small, bright loop protruding from the edge of the gas and dust cloud just to its lower right is the Horsehead nebula — whose famous equine profile appears quite different in infrared light than it does in visible.

The two bright blue stars at the upper right portion of the image are both stars in Orion’s belt. Alnitak, the brighter one closer to the Flame nebula, is a multiple star system located 736 light-years away whose stellar wind is responsible for ionizing the Flame nebula and causing it to shine in infrared. Alnilam, the dimmer star at the uppermost corner, is a blue supergiant 24 times the radius of our Sun and 275,000 times as bright, but 1,980 light-years distant.

The red arc at lower right is the bow shock of Sigma Orionis, a multiple-star system that’s hurtling through space at a speed of 5,260,000 mph (2,400 kilometers per second). As its stellar wind impacts the interstellar medium and piles up before it, an arc of infrared-bright radiation is emitted.

Sigma Orionis is also the star responsible for the glow of the Horsehead nebula.

This rich astronomical scene is an expanded view from WISE’s previously-released image of the region (at right) which used data from only three of its four infrared detectors. In contrast, all four detectors were used in the image above, making more of the nebulae’s intricate structures visible as well as providing comparative information for researchers.

“If you’re an astronomer, then you’ll probably be in hog heaven when it comes to infrared data,” said Edward (Ned) Wright of UCLA, the principal investigator of the WISE mission. “Data from the second sky scan are useful for studying stars that vary or move over time, and for improving and checking data from the first scan.”

Read more on the NASA news release here.

Top and right images: NASA/JPL-Caltech/WISE team. Horsehead nebula visible light image was taken with the 0.9-meter telescope at Kitt Peak National Observatory. Photo credit & copyright: Nigel Sharp (NOAO), KPNO, AURA, NSF. Comparison by J. Major/Universe Today.

June 27, 2012December 23, 2015 by Jason Major

How to Measure a Hot Jupiter

An international team of astronomers has figured out a way to determine details of an exoplanet’s atmosphere from 50 light-years away… even though the planet doesn’t transit the face of its star as seen from Earth.

Tau Boötis b is a “hot Jupiter” type of exoplanet, 6 times more massive than Jupiter. It was the first planet to be identified orbiting its parent star, Tau Boötis, located 50 light-years away. It’s also one of the first exoplanets we’ve known about, discovered in 1996 via the radial velocity method — that is, Tau Boötis b exerts a slight tug on its star, shifting its position enough to be detectable from Earth. But the exoplanet doesn’t pass in front of its star like some others do, which until now made measurements of its atmosphere impossible.

Today, an international team of scientists working with the Very Large Telescope (VLT) at ESO’s Paranal Observatory in Chile have announced the success of a “clever new trick” of examining such non-transiting exoplanet atmospheres. By gathering high-quality infrared observations of the Tau Boötis system with the VLT’s CRIRES instrument the researchers were able to differentiate the radiation coming from the planet versus that emitted by its star, allowing the velocity and mass of Tau Boötis b to be determined.

“Thanks to the high quality observations provided by the VLT and CRIRES we were able to study the spectrum of the system in much more detail than has been possible before,” said Ignas Snellen with Leiden Observatory in the Netherlands, co-author of the research paper. “Only about 0.01% of the light we see comes from the planet, and the rest from the star, so this was not easy.”

Using this technique, the researchers determined that Tau Boötis b’s thick atmosphere contains carbon monoxide and, curiously, exhibits cooler temperatures at higher altitudes — the opposite of what’s been found on other hot Jupiter exoplanets.

“Maybe one day we may even find evidence for biological activity on Earth-like planets in this way.”

– Ignas Snellen, Leiden Observatory, the Netherlands

In addition to atmospheric details, the team was also able to use the new method to determine Tau Boötis b’s mass and orbital angle — 44 degrees, another detail not previously identifiable.

“The new technique also means that we can now study the atmospheres of exoplanets that don’t transit their stars, as well as measuring their masses accurately, which was impossible before,” said Snellen. “This is a big step forward.

“Maybe one day we may even find evidence for biological activity on Earth-like planets in this way.”

This research was presented in a paper “The signature of orbital motion from the dayside of the planet Tau Boötis b”, to appear in the journal Nature on June 28, 2012.

A Tribute to Hubble… and Humanity

Here’s a excellent video compilation featuring images from the Hubble Space Telescope, along with music by Kanye West and quotes from astronomers Neil deGrasse Tyson, Lawrence Krauss and Carl Sagan reflecting on our place in the Universe… and the Universe’s place within each of us.

Uploaded to YouTube by video editor Brandon Fibbs, this is a reminder of how Hubble has opened our eyes to the wonders of the cosmos. Enjoy.

“The cosmos is also within us. We’re made of star stuff… we are a way for the cosmos to know itself.”
– Carl Sagan

May 29, 2012December 23, 2015 by Tammy Plotner

Weekly SkyWatcher’s Forecast: May 28 – June 3, 2012

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Greetings, fellow SkyWatchers! As the Venus Transit draws closer, our bright neighboring planet is quickly disappearing into the sunset glow. As we await this astronomical piece of history, let’s take the time this week to have a look at a host of wonderful lunar features and bright stars. Be sure to catch the conjunction of Spica, Saturn and the Moon – and to catch a shooting star from the Tau Herculid meteor shower! If you’re ready to learn more about the history, mystery and magic of astronomy, then grab your optics and meet me in the back yard…

Monday, May 28 – On this day in 1959, the first primates made it to space. Abel (a rhesus monkey) and Baker (a squirrel monkey) lifted off in the nose cone of an Army Jupiter missile and were carried to sub-orbital flight. Recovered unharmed, Abel died just three days later from anesthesia during an electrode removal, but Baker lived on to a ripe old age of 27.

Our first challenge for the evening will be a telescopic one on the lunar surface known as the Hadley Rille. Using our past knowledge of Mare Serenitatis, look for the break along its western shoreline that divides the Caucasus and Apennine mountain ranges. Just south of this break is the bright peak of Mons Hadley. You’ll find this area of highest interest for several reasons, so power up as much as possible.

Impressive Mons Hadley measures about 24 by 48 kilometers at its base and reaches up an incredible 4572 meters. If this mountain was indeed caused by volcanic activity on the lunar surface, this would make it comparable to some of the very highest volcanically caused peaks on Earth, such as Mount Shasta or Mount Rainer. To its south is the secondary peak Mons Hadley Delta – the home of the Apollo 15 landing site just a breath north of where it extends into the cove created by Palus Putredinus.

Along this ridgeline and smooth floor, look for a major fault line known as the Hadley Rille, winding its way across 120 kilometers of lunar surface. In places, the rille spans 1500 meters in width and drops to a depth of 300 meters below the surface. Believed to have been formed by volcanic activity some 3.3 billion years ago, we can see the impact that lower gravity has had on this type of formation, since earthly lava channels are less than 10 kilometers long and only around 100 meters wide.

During the Apollo 15 mission, Hadley Rille was visited at a point where it was only 1.6 kilometers wide – still a considerable distance as seen in respect to astronaut James Irwin and the lunar rover. Over a period of time, its lava may have continued to flow through this area, yet it remains forever buried beneath years of regolith.

Now let’s head about four fingerwidths northwest of Beta Virginis for another unusual star – Omega. Classed as an M-type red giant, this 480 light-year distant beauty is also an irregular variable which fluxes by about half a magnitude. Although you won’t notice much change in this 5th magnitude star, it has a very pretty red coloration and is worth the time to view.

Tuesday, May 29 – Today in 1919, a total eclipse of the Sun occurred and stellar measurements taken along the limb agreed with predictions based on Einstein’s General Relativity theory – the first such confirmation. Although we call it gravity, space/time curvature deflects the light of stars near the limb, causing their apparent positions to differ slightly. Unlike today’s astronomy, at that time you could only observe stars near the Sun’s limb (within less than an arc second) during an eclipse. It’s interesting to note that even Newton had his own theories on light and gravitation which predicted some deflection!

Tonight on the Moon we’ll be looking for another challenging feature and a crater which conjoins it – Stofler and Faraday.

Located along the terminator to the south, crater Stofler was named for Dutch mathematician and astronomer Johan Stofler. Consuming lunar landscape with an immense diameter of 126 kilometers and dropping 2760 meters below the surface, Stofler is a wonderland of small details in an eroded surrounding. Breaking its wall on the north is Fernelius, but sharing the southeast boundary is Faraday. Named for English physicist and chemist Michael Faraday, it is more complex and deeper at 4090 meters, but far smaller at 70 kilometers in diameter. Look for myriad smaller strikes which bind the two together!

If you’re up for a bit more of a challenge, then let’s head about 59 light-years away in Virgo for star 70. You’ll find it located about 6 degrees northeast of Eta and right in the corner of the Coma, Bootes, and Virgo border. So what’s so special about this G-type, very normal-looking 5th magnitude star?

It’s a star that has a planet.

Long believed to be a spectroscopic binary because of its 117 day shifts in color, closer inspection has revealed that 70 Virginis actually has a companion planet. Roughly 7 times larger than Jupiter and orbiting no further away than Mercury from its cooler-than-Sol parent star, 70 Virginis B just might well be a planet cool enough to support water in its liquid form.

How “cool” is that? Try about 85 degrees Celsius…

Wednesday, May 30 – Are you ready to explore some more history? Then tonight have a look at the Moon and identify Alphonsus – it’s the centermost in a line of rings which looks much like the Theophilus, Cyrillus and Catharina trio.

Alphonsus is a very old, Class V crater which spans 118 kilometers in diameter and drops below the surface by about 2730 meters and contains a small central peak. Partially flooded, Eugene Shoemaker had made of study of this crater’s formation and found dark haloes on the floor. Again, this could be attributed to volcanism and Shoemaker believed them to be maar volcanoes, and the haloes to be dark ash. Power up and look closely at the central peak, for not only did Ranger 9 hard land just northeast, but this is the only area on the Moon where an astronomer has observed a change and back up that observation with photographic proof.

On November 2, 1958 Nikolai Kozyrev’s long and arduous study of Alphonsus was about to be rewarded. Some two years earlier Dinsmore Alter had taken a series of photographs from the Mt. Wilson 60? reflector that showed hazy patches in this area that could not be accounted for. Night after night, Kozyrev continued to study at the Crimean Observatory – but with no success. During the process of guiding the scope for a spectrogram the unbelievable happened – a cloud of gas containing carbon molecules had been captured! Selected as the last target for the Ranger photographic mission series, Alphonsus delivered 5814 spectacular high-resolution images of this mysterious region before Ranger 9 splattered nearby.
Capture it yourself tonight!

Now let’s add to our double star list as we hunt down Zeta Bootes located about 7 degrees southeast of Arcturus. This is a delightful multiple star system for even small telescopes.

Thursday, May 31 – As we begin the evening, be sure to note a splendid conjunction. Tonight the waxing Moon will dominate the sky, but it’s joined by the visage of Spica and Saturn. Look for the brilliant star located just to the lunar north and the gentle giant planet about 10 degrees or so further north.

Now, let’s have a look at awesome crater Clavius. As a huge mountain-walled plain, Clavius will appear near the terminator tonight in the lunar southern hemisphere, rivaled only in sheer size by similar structured Deslandres and Baily. Rising 1646 meters above the surface, the interior wall slopes gently downward for a distance of almost 24 km and a span of 225 km. Its crater-strewn walls are over 56 km thick!

Clavius is punctuated by many pockmarks and craters; the largest on the southeast wall is named Rutherford. Its twin, Porter, lies to the northeast. Long noted as a test of optics, Clavius crater can offer up to thirteen such small craters on a steady night at high power. How many can you see?

While the glare will make it difficult to do many things, we can still have a look at other bright objects! Let’s start tonight by going just north of Zeta Bootes for Pi. With a wider separation, this pair of whites will easily resolve to the smaller telescope.

Now skip up northeast about a degree for Omicron Bootes. While this is not a multiple system, it makes for a nice visual pairing for a binocular challenge. For telescopes, the southeastern star holds interest as a small asterism.
Continue northeast another two degrees to discover Xi Bootes. This one is a genuine multiple star system with magnitude 5 and 7 companions. Not only will you enjoy this G-type sun for its duplicity, but for the fine field of stars in which it resides!

Now have a look at Mars. Over the last few weeks it has dropped significantly in brightness and has now reached an approximate +0.5 magnitude. Have you been watching its progress against the background stars? It won’t be long until it crosses constellation boundaries again.

Friday, June 1 – Tonight on the Moon, crater Copernicus will try to steal the scene, head further south to capture another lunar club challenge – Bullialdus. Even binoculars can make out this crater with ease near the center of Mare Nubium. If you’re scoping – power up – this one is fun! Very similar to Copernicus, note Bullialdus’ thick, terraced walls and central peak. If you examine the area around it carefully, you can note it is a much newer crater than shallow Lubiniezsky to its north and almost non-existent Kies to the south. On Bullialdus’ southern flank, it’s easy to make out its A and B craters, as well as the interesting little Koenig to the southwest.

Now let’s have a look at a tasty red star – R Hydrae. You’ll find it about a fistwidth south of Spica or about a fingerwidth west of Gamma Hydrae.

R was the third long term variable star to be discovered and it is credited to Maraldi in 1704. While it had been observed by Hevelius some 42 years earlier, it was not recognized immediately because its changes happen over more than a year. At maximum, R reaches near 4th magnitude – but drops well below human eye perception to magnitude 10. During Maraldi’s and Hevelius’ time, this incredible star took over 500 days to change, but it has speeded up to around 390 days in the present century.

Why such a wide range? Science isn’t really sure. R Hydrae is a pulsing M-type giant whose evolution may be progressing more rapidly than expected due to changes in structure. What we do know is that it is around 325 light-years away and is approaching us at around 10 kilometers per second.

In the telescope, R will have a pronounced red coloration which deepens near minima. Nearby is 12th magnitude visual companion star Ho 381, which was first measured for position angle and distance in 1891. Since that time no changes in separation have been noted, which leads us to believe that the pair may be a true binary.

Saturday, June 2 – Tonight would be a wonderful opportunity for Moongazers to return to the surface and have a look at the peaceful Sinus Iridum area. If you’ve been clouded out before, be sure to have a look for telescopic lunar club challenges – Promontoriums Heraclides and LaPlace.

Now let’s return again to R Hydrae. While observing a variable star with either the unaided eye, binoculars, or a telescope can be very rewarding, it’s often quite difficult to catch changes in long-term variables, because there are times when the constellation is not visible. While R Hydrae is unique in color, let’s drop about half a degree to the southeast to visit another variable star – SS Hydrae.

SS is a quick change artist – the Algol-type. While you will need binoculars or a telescope to see this normally 7.7 magnitude star, at least its fluctuations are far more rapid, with a period of only 8.2 days. With R Hydrae we have a star that expands and contracts causing the changes in brightness – but SS is an eclipsing binary. While less than a half magnitude is not a noteworthy amount, you will notice a difference if you view it over a period of time. Be sure to note that this is actually a triple star system, for there is also a 13th magnitude companion star located 13? from the primary. Watch if as often as possible and see if you can detect changes in the next few weeks!

Sunday, June 3 – If you’re up early, why not keep a watch out for the peak of the Tau Herculids meteor shower? These are the offspring of comet Schwassman-Wachmann 3, which broke up in 2006. The radiant is near Corona Borealis and we’ll be in this stream for about a month. At best when the parent comet has passed perihelion, you’ll catch about 15 per hour maximum. Most are quite faint and the westering Moon will interfere, but sharp-eyed observers will enjoy it.

Tonight let’s have a look at a very bright and changeable lunar feature that is often over-looked. Starting with the great grey oval of Grimaldi, let your eyes slide along the terminator towards the south until you encounter the bright crater Byrgius. Named for Joost Burgi, who made a sextant for Tycho Brahe, this “seen on the curve” crater is really quite large with a diameter of 87 kilometers. Perhaps one of the most interesting features of all is high albedo Byrgius A, which sits along its east wall line and produces a wonderfully bright ray system. While it is not noted as a lunar club challenge, it’s a great crater to help add to your knowledge of selenography!

Now let’s try a visual double for the unaided eye – Eta Virginis. Can you distinguish between a 4th and 6th magnitude pair?

The brighter of the two is Zaniah (Eta), which through occultation had been discovered to be a triple star. In 2002, Zaniah became the first star imaged by combining multiple telescopes with the Navy Prototype Optical Interferometer. This was the first time the three were split. Two of them are so close that they orbit in less than half the distance between the Earth and Sun!

Binocular users should take a look at visual double Rho Virginis about a fistwidth west-southwest of Epsilon. This pair is far closer and will require an optical aid to separate. The brighter of this pair – Rho – is a white, main sequence dwarf with a secret… It’s a variable! Known as a Delta Scuti type, this odd star can vary slightly in magnitude in anywhere from 30 minutes to two and a half hours as it pulsates.

For mid-to-large telescopes, Rho offers just a little bit more. The visual companion star has a visual companion as well! Less than a half degree southwest of Rho is a small, faint spiral galaxy – NGC 4608 (Right Ascension: 12 : 41.2 – Declination: +10 : 09) – at 12th magnitude, it’s hard to see because of Rho’s brightness…but it’s not alone. Look for a small, but curiously shaped galaxy labeled NGC 4596 (Right Ascension: 12 : 39.9 – Declination: +10 : 11). Its resemblance to the planet Saturn makes it well worthwhile!

Until next week? Ask for the Moon, but keep on reaching for the stars!

May 11, 2012December 23, 2015 by Jason Major

By Thor’s Mighty Helmet!

Image of the Thor's Helmet nebula (NGC 2359) Credit: R. Barrena (IAC) and D. López

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Going to see the new Avengers movie this weekend, either for the first or fortieth time? You may not see much of Thor’s helmet in the film (as he opts for more of a “Point Break” look) but astronomers using the Isaac Newton Group of telescopes on the Canary Islands have succeeded in spotting it… in this super image of the Thor’s Helmet nebula!

Named for its similarity to the famous horned Viking headgear (seen horizontally), the Thor’s Helmet nebula is a Wolf-Rayet structure created by stellar winds from the star seen near the center blowing the gas of the bluish “helmet” outwards into space via pre-supernova emissions.

The colors of the image above, acquired with the ING’s Isaac Newton Telescope, correspond to light emitted in hydrogen alpha, doubly-ionised oxygen and single-ionised sulfur wavelengths.

Super-sized for the thunder god himself, Thor’s Helmet measures at about 30 light-years across. It’s located in the constellation Canis Major, approximately 15,000 light-years from Earth. (You’d think Thor would have left his favorite accessory in a more convenient location… I suspect Loki may be behind this.)

Astronomers, assemble!

Read more about this and see other images from the ING telescopes here.

The Isaac Newton Group of Telescopes (ING) is owned by the Science and Technology Facilities Council (STFC) of the United Kingdom, and it is operated jointly with the Nederlandse Organisatie voor Wetenschappelijk Onderzoek (NWO) of the Netherlands and the Instituto de Astrofísica de Canarias (IAC) of Spain. The telescopes are located in the Spanish Observatorio del Roque de los Muchachos on La Palma, Canary Islands, which is operated by the Instituto de Astrofísica de Canarias (IAC).

May 4, 2012December 23, 2015 by Jason Major

The Secret Origin Story of Brown Dwarfs

Artist's impression of a Y-dwarf, the coldest known type of brown dwarf star. (NASA/JPL-Caltech)

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Sometimes called failed stars, brown dwarfs straddle the line between star and planet. Too massive to be “just” a planet, but lacking enough material to start fusion and become a full-fledged star, brown dwarfs are sort of the middle child of cosmic objects. Only first detected in the 1990s, their origins have been a mystery for astronomers. But a researchers from Canada and Austria now think they have an answer for the question: where do brown dwarfs come from?

If there’s enough mass in a cloud of cosmic material to start falling in upon itself, gradually spinning and collapsing under its own gravity to compress and form a star, why are there brown dwarfs? They’re not merely oversized planets — they aren’t in orbit around a star. They’re not stars that “cooled off” — those are white dwarfs (and are something else entirely.) The material that makes up a brown dwarf probably shouldn’t have even had enough mass and angular momentum to start the whole process off to begin with, yet they’re out there… and, as astronomers are finding out now that they know how to look for them, there’s quite a lot.

So how did they form?

According to research by Shantanu Basu of the University of Western Ontario and Eduard I. Vorobyov from the University of Vienna in Austria and Russia’s Southern Federal University, brown dwarfs may have been flung out of other protostellar disks as they were forming, taking clumps of material with them to complete their development.

Basu and Vorobyov modeled the dynamics of protostellar disks, the clouds of gas and dust that form “real” stars. (Our own solar system formed from one such disk nearly five billion years ago.) What they found was that given enough angular momentum — that is, spin — the disk could easily eject larger clumps of material while still having enough left over to eventually form a star.

Basu-Vorobyov model — Model of how a clump of low-mass material gets ejected from a disk (S. Basu/E. Vorobyev)

The ejected clumps would then continue condensing into a massive object, but never quite enough to begin hydrogen fusion. Rather than stars, they become brown dwarfs — still radiating heat but nothing like a true star. (And they’re not really brown, by the way… they’re probably more of a dull red.)

In fact a single protostellar disk could eject more than one clump during its development, Basu and Vorobyov found, leading to the creation of multiple brown dwarfs.

If this scenario is indeed the way brown dwarfs form, it stands to reason that the Universe may be full of them. Since they are not very luminous and difficult to detect at long distances, the researchers suggest that brown dwarfs may be part of the answer to the dark matter mystery.

“There could be significant mass in the universe that is locked up in brown dwarfs and contribute at least part of the budget for the universe’s missing dark matter,” Basu said. “And the common idea that the first stars in the early universe were only of very high mass may also need revision.”

Based on this hypothesis, with the potential number of brown dwarfs that could be in our galaxy alone we may find that these “failed stars” are actually quite successful after all.

The team’s research paper was accepted on March 1 into The Astrophysical Journal.

Read more on the University of Western Ontario’s news release here.