When is exoplanet news “juicy”? Yesterday at a Kepler press conference held at NASA Ames, Roger Hunter, Kepler project manager, introduced the proceedings as juicy. And as three scientists presented the findings, it turned out to be a good adjective. The researchers believe they have discovered the first water worlds (besides Earth) in our galaxy.

Two systems are providing new evidence of rocky Earth-like planets in the habitable zone—the range of distance from a star where the surface temperature of an orbiting planet might be suitable for liquid water. Kepler 62 has five planets total, but two of those, 62e and 62f, orbit inside the habitable zone. Kepler 69 has two planets but only one in the habitable zone, 69c.

For exoplanets and their stars, size matters when it comes to habitability. At 1,200 light years away, the star Kepler 62 is two-thirds the size of our Sun. That brings the habitable zone in a bit closer to the star. The two planets of interest, 62e and 62f, are 1.6 and 1.4 times the diameter of Earth, respectively. This also puts them in the “just-right” size for habitability.

At the press conference, William Borucki, Kepler science principal investigator at NASA Ames, said that 62e and 62f “are the best candidates to be habitable, not just within the habitable zone.”

Computer models suggest that the largest rocky planets will have a diameter no greater than 1.5 times that of Earth’s, explained Lisa Kaltenegger of the Max Planck Institute for Astronomy and Harvard-Smithsonian Center for Astrophysics. And a planet’s mass, between 1.2-2.5 times Earth’s mass, can be an indicator for liquid water. While Kepler 62e and 62f are too small to measure their mass, Kaltenegger and her team’s modeling makes these planets very wet, indeed.

Kepler 69c, on the other hand, is 2,700 light years away and 1.5 times Earth’s diameter. It orbits near the inner, hotter edge of its star’s habitable zone. Thomas Barclay, Kepler scientist from the Bay Area Environmental Research Institute, likens it to a super Venus, rather than a super Earth. “We don’t have anything like it in our solar system,” he said.

“The Kepler spacecraft has certainly turned out to be a rock star of science,” said John Grunsfeld, at NASA Headquarters in Washington. “The discovery of these rocky planets in the habitable zone brings us a bit closer to finding a place like home. It is only a matter of time before we know if the galaxy is home to a multitude of planets like Earth, or if we are a rarity.”

The findings are published this week in Science (Kepler 62) and the Astrophysical Journal (Kepler 69).

For an interactive on Kepler’s planetary discoveries and their orbits, click here.

Image: NASA Ames/JPL-Caltech

When is an exoplanet not an exoplanet? When it’s a white dwarf, of course. Well, at least in the case of KOI-256 (Kepler Object of Interest, number 256).

NASA’s amazing exoplanet hunter, the space-based Kepler mission, spotted an object transiting the red dwarf star, KOI-256, using its standard technique—as the object passes in front of its star, Kepler detects a decrease in the star’s light.

But something looked different about this star. In addition to the dip in brightness from the transiting object, the star’s brightness seemed to vary in a way that suggested it was behaving quite oddly. So Phil Muirhead, of the California Institute of Technology, began to explore further.

Muirhead and colleagues first used a ground-based telescope to get another look. Measuring the star’s radial velocity, they discovered that the red dwarf was wobbling around like a spinning top. Because of this, the scientists suspected the object wasn’t an exoplanet after all, but something much more massive—likely a white dwarf.

A white dwarf is essentially what a dead star leaves behind—a hot cinder, incredibly massive for its size. It “weighs” a lot more than an exoplanet, so Muirhead needed to figure out how much mass exists in the KOI-256 system.

To measure the combined mass of the two objects in the binary pair, the researchers used a technique called gravitational lensing: one of the consequences of Einstein’s general theory of relativity is that gravity bends light, so scientists use gravitational lensing to figure out how much mass is bending (or lensing) light from more distant sources. And while the technique has been utilized to measure the mass of galaxies, it’s the first time it has been used to “weigh” a binary star system. Since we know the approximate mass of a red dwarf, we can then estimate the mass of the companion, which indeed turns out to be a white dwarf.

“This white dwarf is about the size of Earth but [with] the mass of the Sun,” says Muirhead. “It’s so hefty that the red dwarf, though larger in physical size, is circling around the white dwarf.”

The red dwarf orbits the white dwarf in just 1.4 days. This orbital period is so short that at an earlier time the stars must have previously undergone a “common-envelope” phase in which the red dwarf orbited within the outer layers of its companion star—a giant star that eventually died and left behind the white dwarf we see today.

The short orbital period also means the red dwarf’s days are numbered. In a few billion years, the intense gravity of the white dwarf will strip material off the red dwarf, forming a hot accretion disk of in-falling material around the white dwarf.

New Scientist offers an animation of the two stars currently in action (with a rockin’ soundtrack). The research is published in the Astrophysical Journal.

Image: NASA/JPL-Caltech

Several weeks ago, I wrote about a lively session at the AAAS Meeting about dark matter. At the meeting, Nobel laureate Samuel Ting hinted that he may have further evidence of the mysterious matter that makes up a quarter of the mass of our universe. He said the results would be published in a few weeks, and much to reporters dismay, left it at that.

Today, speaking from CERN, Ting finally announced the results. They will be published on Friday in the journal Physical Review Letters.

Ting spent several years (almost two decades!) convincing NASA and others to establish a detector in space to measure dark matter. Now, the Alpha Magnetic Spectrometer (AMS) experiment, installed on the International Space Station in 2011, studies cosmic rays before they have a chance to interact with the Earth’s atmosphere, and the secret to dark matter could lie in these cosmic rays.

Scientists believe that an excess of positrons in the cosmic ray flux could be the result of dark matter particles colliding and annihilating. One of the leading explanations for dark matter, a subset of particles collectively known as “weakly-interacting massive particles” (or “WIMPs”), would create positrons as a by-product of colliding with one another: individual collisions would happen rarely, but scattered throughout the Universe, they would result in a detectable bath of positrons of different energies. And AMS indeed detected an excess of these particles. While this has been measured in the past by other space-based observatories, the data from AMS represents the largest collection of positron particles recorded in space.

“As the most precise measurement of the cosmic ray positron flux to date, these results show clearly the power and capabilities of the AMS detector,” Ting remarked. “Over the coming months, AMS will be able to tell us conclusively whether these positrons are a signal for dark matter, or whether they have some other origin.”

However promising the results, they may not signal dark matter at all. The positrons could originate from pulsars distributed around the galactic plane. Now AMS will further refine the measurement’s precision, and gather and analyze more data. Ting believes there’s no question that in the next year or two, we will understand exactly what these results indicate. It could be dark matter. Stay tuned…

On Monday, I described a night of observing at Chile’s Las Campanas Observatory, and yesterday, I gave some background on the objects known as Y dwarfs—the coldest and least massive category of stellar wannabes known as brown dwarfs. I’m tagging along with two researchers—Jackie Faherty, an NSF fellow at the Universidad de Chile, and Chris Tinney, a professor at the University of New South Wales—to describe some of their research on these objects.

Most importantly, the two astronomers are chasing a short “target list” of Y dwarfs, making careful measurements to determine their distances and velocities—where they are, and where they’re going. One aspect of this research could make headlines quite easily, if one of these brown dwarfs turns out to lie closer to the Sun than the nearest star, Proxima Centauri (but not so close as the fabled Nemesis object proposed as a resident of the outer Solar System). Such a discovery would beat out even the recent announcement of “the closest star system found in a century,” and indeed, Faherty and Tinney used some of their observing time to take a look at that object to learn more about it.

To accomplish their program, Faherty and Tinney use the principal of stellar parallax, or the apparent shift of an object as the Earth travels around the Sun over the course of a year.  “Parallaxes offer the most reliable distance estimates we have in astronomy. They take care and time but the scientific return is enormous,” says Faherty. Forgive me as I digress for the rest of the paragraph, and feel free to skip to the beginning of the next… Typically, when people teach about parallax (even in three detailed videos), they treat it as a two-dimensional problem, possibly because the trigonometry is easiest to draw on the surface of a blackboard or a video screen. In reality, Earth‘s orbit and distant stars represent a three-dimensional relationship that includes a lot more information than a perceived back-and-forth movement of an object observed in six-month intervals. Over the course of a year, a stars path actually inscribes a tiny ellipse on the sky as perceived from different points in (elliptical, BTW) orbit around the Sun. I won’t go into details, but it turns out that astronomers are trying to measure the size of these elliptical movements (they already know the shape based on the star’s position in our sky), a much more manageable task than measuring a linear shift in six-month increments.

Nonetheless, measuring parallaxes requires numerous precise determinations of a star’s position on the sky over multiple years, and it only works for the objects quite nearby in astronomical terms. Luckily, these Y dwarfs are some of the closest things outside our Solar System (cf. that previous comment about hoping to find a brown dwarf closer than the nearest star), so they exhibit enormous parallaxes.

Of course, Y dwarfs also happen to be quite faint, which makes the observations trickier, and they also don’t sit still. The classic parallax description assumes that the star remains motionless relative to us (a good assumption for most stars), but some nearby stars zip along on their own trajectory through three-dimensional space. Any movement not toward or away from us shows up as the star’s proper motion, or apparent motion on the sky from year to year, turning the neat ellipse described above into a squiggly path across the sky.

But that turns out to be a bonus! The proper motion of the star can suggest a relationship to other stars nearby. Stars that move together probably share a common origin, so a Y dwarf’s association with such a “moving group” (e.g., the ones associated with Ursa Major or Beta Pictoris) gives a clear indication of its age. You can’t determine the age of most lone stars, but a group of stars that share a common origin show color and temperature relationships that allow for an accurate estimate of the group’s collective age.

Age provides a critical benchmark for understanding Y dwarfs. As Faherty describes it:

In a nutshell, brown dwarfs lack the nice relationship that exists for stars whereby you can get an idea of the mass if you know its temperature. Anything goes for objects below 3,000 Kelvin. Without an age you might be studying an old low-mass star, a cool brown dwarf, or a hot planet. In each case, their light fingerprint would appear the same.

Faherty and Tinney will return to these Y dwarfs for many nights over the next several years, catching them at the right times to refine estimates of their positions and velocities, and figuring out how these objects fit into the awkward conceptual space between stars and planets. They started their parallax program in March of 2012, and they published their first paper from the campaign last fall.

Eventually, their observations will lead to a clearer understanding of these exotic objects, and these studies also pave the way to understanding the hundreds upon hundreds of planets we’re finding orbiting other stars. Faherty summarizes:

We are at an interesting crossroad with brown dwarf science. We’ve found the objects with temperatures that inch up next to Jupiter. They are faint but they are sitting out in space all by their lonesome waiting to be studied in detail. Y dwarfs with parallaxes will be a critical key to understanding the composition of exoplanets.

Thus, each night of observing plays a role in piecing together a much larger puzzle, revealing a picture of objects that reside along a continuum from planet to brown dwarf to star.

By the way, if you’re in San Francisco and looking for something tomorrow night, come to NightLife! At the 6:30 planetarium show, I’ll talk about “Color of the Cosmos” and describe how astronomers don’t see (or talk about) color the way most people do. I might even mention brown dwarfs…

Ryan Wyatt is the director of the Morrison Planetarium and Science Visualization at the California Academy of Sciences.

Image credit: Karl Schultz

In yesterday’s piece, I described an evening’s work making precision measurements of brown dwarfs at the 6.5-meter Baade Telescope in Chile. But why go to so much trouble to figure out where these objects are in the sky? Well, to figure out how far away they are and how fast they are moving…

In particular, astronomers Jackie Faherty, an NSF fellow at the Universidad de Chile, and Chris Tinney, a professor at the University of New South Wales, are looking at the coolest brown dwarfs, called “Y dwarfs.” Fervently sought after for more than a decade, Y dwarfs have temperatures more similar to a human body than a star—the missing link between giant planets (such as Jupiter) and the lowest mass stars. The evening’s targets were discovered using NASA’s Wide-field Infrared Survey Explorer (WISE) mission, and although some are already confirmed brown dwarfs, the list also includes suspects that need further exploration.

Strictly speaking, brown dwarfs fall shy of the star categorization because they don’t have enough mass to sustain the fusion of hydrogen into helium—the primary thermonuclear reaction that causes stars to shine. “The little stars that couldn’t,” Tinney quips. Too small to ignite, brown dwarfs smolder at temperatures less than a third as hot as the Sun, or much cooler, as noted above.

We humans (even astronomers) tend to create categories more readily than nature does. If the difference between “star” and “brown dwarf” causes some confusion, then so does the difference between “brown dwarfs” and “giant planets”… Does the difference come down to the manner in which they form—planets building up from gas and dust around stars versus brown dwarfs from the collapse of gas clouds in isolation? Or do the composition differences define them—brown dwarfs burn a little hydrogen at birth, planets do not?

Certainly brown dwarfs start to look a lot more like planets… We classify stars based on elements we observe in their spectra (studying their light fingerprints, in a sense), and typically, that means looking for hydrogen and helium as well as trace quantities of elements such as calcium, silicon, and even iron. But as stars get colder, molecules take over and start absorbing light before it can escape the surface. By the time we reach brown dwarf temperatures, complicated chemistry takes over, and everything from silicates to methane can be found absorbing light. NASA scientists even think they’ve detected weather patterns in different layers of a brown dwarf atmosphere! Sounds a lot more like a planet than a star.

Based on the laws of physics and the witches’ brew of molecules observed in these objects, astronomers use computers to model the evolution of different kinds of brown dwarfs.

As Faherty explains:

Using a laboratory understanding of the complicated chemistry that exists at their low temperatures, modelers can make predictions about what the light fingerprints from brown dwarfs should look like. However, there is one major piece of the puzzle required to fully understand what brown dwarfs are made of: precise distances. These lead to intrinsic brightness values which grounds all other measurements we can make regarding brown dwarf compositions and evolution.

Thus, Faherty and Tinney have taken on the challenge of determining precise distances to the coldest brown dwarfs. In order to make the much needed measurements, they take repeated images of their targets, over many nights during the year, specifically timed to figure out the Y dwarfs’ distances and velocities—where they are, and where they’re going.

Knowing an object’s distance tells astronomers a lot: most critically, you can determine its intrinsic brightness, which helps lead to estimates of its temperature and age. Knowing an object’s kinematics (basically where’s its going and how quickly compared to other objects in the galaxy) can help astronomers understand how it fits into the populations of other objects in the galaxy.

Tomorrow, I’ll recap more of what these results will mean for understanding the nature of stars, planets, and the intriguing objects in between.

Ryan Wyatt is the director of the Morrison Planetarium and Science Visualization at the California Academy of Sciences.

Image credit: NASA/JPL-Caltech

I’m writing this from more than 8,000 feet (around 2,500 meters, for the more metric-ly inclined) above sea level, in the control room of one of the twin 6.5–meter Magellan telescopes at Las Campanas Observatory, near the southern end of Chile’s Atacama Desert. I’m tagging along on a night of observing with Jackie Faherty and Chris Tinney as they measure distances and chemical compositions of exotic objects known as brown dwarfs. For the next three Science Today entries, I’ll try my best to tell the story of this one night of observing and to give a sense of what Faherty and Tinney are attempting to learn about these tiny, faint stellar wannabes.

The night’s work starts in the afternoon. The instruments require calibration, which can take place long before the sky gets dark. Because the observations will involve taking both images (basically photographs) and spectra (a “fingerprint” of the light) of the brown dwarfs, they will use both the FourStar camera and the FIRE spectrograph. Astronomers have a more fastidious approach to their images than, say, your average Instagram user, so they carefully characterize the camera’s responsiveness and uniformity. For the spectrograph, they create a map of how the light splits into its constituent wavelengths using the equivalent of neon billboard lights aimed at the instrument.

At sunset, a few clouds in the southwest cause some concern: astronomers prefer their sunsets dull, unimpressive, and cloud-free. The worry passes, however, and as the sky darkens, the work begins in earnest.

Only four days from full, the moon brightens the sky considerably. For astronomers who observe in visible wavelengths (what we see with our eyes), this would ruin a perfectly good night. Consequently, many seek out “dark time,” defined as the first few nights before or after the new moon. Luckily, brown dwarfs show up best in infrared light, so tonight’s observations can take place in the “bright time,” three to five nights before or after the full moon. Indeed, the astronomers appreciate not having to deal with pitch-black observing conditions: “It’s inconvenient. You can’t see the clouds, and you trip over things,” Tinney notes.

A little more calibration occurs as the sky darkens, including pointing and focusing the telescope, and then the observations begin. “The focus at the beginning of the night changes rapidly because the temperature is dropping,” Faherty explains. “So we take shorter exposures, and continually monitor the images for out-of focus stars, which look like little donuts.”

Ultimately, Faherty and Tinney want to determine each object’s precise location in the sky—a process known as astrometry—as well as its light fingerprint—a process known as spectroscopy.

Particularly for this kind of project, astronomers need excellent “seeing,” which refers to “the blurring the atmosphere produces,” as Tinney describes succinctly. More blurring means the light gets spread out over a larger area of the detector, making precision work on faint brown dwarfs far more challenging.

Astronomers describe the quality of seeing in terms of the apparent angular diameter of a star. Optimal observing conditions at Las Campanas can yield seeing of 0.4 arcseconds or better—equivalent to the diameter of a penny observed from a distance of twelve miles (nearly twenty kilometers). This evening started with seeing around 0.5 arcseconds, but as the night wears on, the seeing drops to nearly 0.3 arcseconds! A great night! (Or perhaps simply observational karma: on Faherty’s last visit to the Magellan telescope, the seeing averaged 1.4 arcseconds, and the observatory shut down because of high winds. C’est l’astronomie.)

Amazingly, these high-quality observations can translate into even more impressive precision when it comes to locating the brown dwarfs relative to the other stars in the image. The resolution of the detector (about 0.16 arcseconds per pixel for FourStar) combined with good seeing means they can pinpoint an object’s location down to a few milliarcseconds—that’s right, 4% the apparent size of the object itself! Such excellent conditions also make it possible to tease apart the atmospheric properties of some of the faintest compact sources in the vicinity of the Sun.

Tomorrow, I’ll share a little more about brown dwarfs and the particular challenge that Faherty and Tinney plan to address, and on Wednesday, I’ll give a summary of how the evening’s work went and what it could mean for the next steps in brown dwarf science.

Ryan Wyatt is the director of the Morrison Planetarium and Science Visualization at the California Academy of Sciences.

Image:  Karl Schultz

At the recent AAAS meeting in Boston, I met Amanda Hendrix from NASA’s Cassini Mission. Dr. Hendrix, a planetary scientist, has been with Cassini since 1999, when Cassini flew by Earth’s Moon. “I became involved with the UVIS (the Ultraviolet Imaging Spectrograph) team to analyze the Moon data. The next year, I began working with the Cassini Project team at JPL as part of the Science Planning team, to plan out the science investigations that would happen during each icy satellite flyby.” Now she uses data from UVIS to study the icy moons of Saturn.

Cassini has returned so many stunning results over the last nine years, I thought I’d get the latest from her. Here’s an excerpt of our email interview.

Where is Cassini right now? What is it studying?

Cassini is in a highly inclined portion of its tour of the system, so that its path is ~60° out of the plane of Saturn’s equator. This provides Cassini’s instruments access to wonderful views of the polar regions of Saturn and Titan, and also a unique perspective on the rings system.

After spending the last couple of years in the equatorial plane, it is great to get some beautiful views of the rings, and to understand how they are evolving on the timescales of a few years. High latitude views of the planet and Titan mean that we can observe critical seasonal variations happening in the Saturn atmosphere (such as the development of the giant “serpent” storm) and the Titan atmosphere (such as the formation of the southern hemisphere polar hood) and on the Titan surface (we can watch for changes in the lakes and seas at the southern and northern polar regions).

Looking for and studying seasonal variations is important because it helps us to piece together the clues to understand solar system processes and will ultimately aid in the study of the formation and evolution of the solar system.

Can you highlight some of Cassini’s recent discoveries?

There are several studies being undertaken to understand the variability (if any) of Enceladus’ activity, and its ice grain and water vapor output, with orbital location. Some models have shown that the gravitational stresses vary, depending on where Enceladus is in its orbit, and this might affect the plume output. So those studies are ongoing and interesting.

On another topic, Cassini images have been used to show that Titan “glows” from deep in its atmosphere, as seen while Titan was in Saturn’s shadow. The likely cause is deeply-penetrating particles (such as cosmic rays) that excite the atmospheric gases. Another discovery is that there could be icebergs—of hydrocarbon ice—floating on the lakes of Titan. This comes from the radar images of the lakes along with calculations that if some amount of Titan atmosphere is contained within the methane ice, it will float rather than sink.

What’s next for Cassini? 

Cassini will remain in the inclined phase of orbits until around February 2015 (it recently passed the peak in inclination and is now heading back down), then it will execute orbits roughly in the equatorial plane (for about a year), and this is when we will have two Dione and three Enceladus flybys. The final close flyby of the moon Rhea took place Saturday, March 9, 2013. We have numerous upcoming Titan flybys to study this intriguing moon and track its seasonal variations.

How much longer will Cassini be operational?

The plan is for Cassini to remain in operation, in orbit at Saturn, until September of 2017. An exciting end-of-mission is being planned, whereby Cassini orbits closer and closer to Saturn, with its orbital periapse (closest point to Saturn in the orbit) between the top of the atmosphere and the inner edge of the D-ring (the innermost ring), at high inclination. Such close passes will tremendously help the instruments on Cassini to measure the internal structure and magnetic field of Saturn, and will allow for a careful measurement of the mass of the rings—which is important in ultimately understanding their age and source! Finally, Saturn’s gravity will capture Cassini and the mission will be over.

What are some of your favorite findings?

The discovery of activity at Enceladus is one of my favorites! That such a small moon puts out so much material, with great effect on the rest of the system, is really astonishing and wonderful. This discovery was great because it was such a multi-instrument discovery and really highlights the utility of synergistic investigations on a mission.

Another one of my favorites is the discovery of liquid lakes on Titan—the only body in the solar system other than Earth with liquid on the surface! The landing of the Huygens probe on the surface of Titan was a really exciting time. Another of my favorite findings was the up-close views of bizarre Iapetus that we obtained during our close flybys with that moon.

Why do the data and images Cassini provides move people so much?

Cassini is such a great mission because the payload includes a complementary instrument suite that allows us to probe nearly every aspect of the Saturn system. The datasets are stunning and moving partly because the Saturn system is very beautiful. The intricate detail revealed in the images is wonderfully mind-boggling!

Recent Cassini image (with Venus hiding in Saturn’s rings): NASA/JPL-Caltech/Space Science Institute

We know that our galaxy, the Milky Way, with its hundreds of billions of stars (and potentially equal or greater number planets) is only one of perhaps 100 billion galaxies within our observable Universe.

And with that many galaxies to observe, we find plenty of surprises.

A mere 20 million light years away lies the plainly named M106, or Messier 106, a spiral galaxy like the Milky Way. Though discovered in 1781, it was posthumously added to Charles Messier’s catalog nearly two centuries later—in 1947, 23 years after astronomers had accepted the concept of galaxies beyond our own. The massive nearby galaxy remains an object of interest today.

Recently, award-winning amateur astrophotographer Robert Gendler combined his own work with amateur astronomer Jay GaBany’s, along with data collected from the Hubble Space Telescope, to produce a stunning mosaic of one of best images yet of M106, revealing a secret of our cosmic neighbor.

Like the Milky Way, M106 has bright arms that form its spiral and reach out from the supermassive black hole in its center. While most spiral galaxies show evidence for central black holes, M106 harbors a very active one at its core that is devouring surrounding matter at an alarming rate. By comparison, the black hole at the center of the Milky Way pulls in wisps of gas only occasionally.

The new amalgamated image shows multiple arms on two different planes rather than two arms on one plane. M106 has two arms filled with the glowing blue of newly forming stars on one plane, and starless, gas-composed arms—viewed in X-ray and radio waves—on the other plane. As matter falls into the black hole, it forms a huge flat disk called an accretion disk and spews high-speed jets of particles.  These collide with the relatively stationary gas of the other arms and create a shock wave that heats the material to over one million degrees. This energy causes the anomalous arms to glow red, the color of excited hydrogen.

While we know of many galaxies containing super massive black holes, M106 lends itself to study for numerous reasons. It is in a near perfect position for astronomers on Earth to view the perpendicular axis of the X-ray particles. And it’s also very close by—relatively speaking, of course!

In a time when we are only beginning to understand the composition and mysteries of our own galactic home, observations and images such as those of M106 provide rare opportunities for astronomers to study the workings and structures of other, more distant galaxies. And the more we learn of other galaxies, the more we can understand how the Milky Way compares.

Perhaps the most exciting aspect of this discovery is that the contribution comes from amateur astronomers, helping to highlight the immense value of dedicated volunteers in sifting through the massive quantities of data recorded by telescopes such as Hubble.

Elise Ricard holds a master’s degree in museum education and is a presenter at Morrison Planetarium.

Image: NASA, ESA, the Hubble Heritage Team (STScI/AURA), and R. Gendler (for the Hubble Heritage Team). Acknowledgment: J. GaBany, A van der Hoeven)

Discovered in June 2011, Comet C/2011 L4 Pan-STARRS (yeah, quite a mouthful) is one of two comets that astronomershope will flare to spectacular brightness this year, becoming easily visible to the naked eye. While the December appearance of Comet C/2012 S1 ISON is still too far away to predict its brightness accurately, Comet Pan-STARRS has been putting on a good show for Southern Hemisphere observers for the past few weeks, swinging up through the plane of the solar system from below.

Now past perihelion (its closest approach to the Sun), the cometcontinues to drift northward, and Northern Hemisphere observers can now take a gander. However, it isn’t quite as bright as astronomers originally hoped it would be. While photos taken from Southern Hemisphere locations have been quite striking, the comet is now starting to fade as it retreats from the Sun, gradually climbing out of the evening twilight for northern viewers.

Skywatchers will need binoculars to see it low in the west about 30-45 minutes after sunset, after the twilight glow has dimmedenough to not wash it from view, but before the comet sets. Still, any comet that can be seen at all is a beautiful, ethereal sight, and Pan-STARRS has been noted for its bright head anddelicate, fan-shaped tail.

The next few nights offer the waxing Moon as a reference to help locate the comet. On the evening of Tuesday the 12th, look for it just to the left of the razor-thin, day-old crescent, and on Wednesday the 13th, with the Moon slightly higher in the sky, the comet will lie below it.

Where did that mouthful of a name come from, anyway? Following the tradition of naming comets after their discoverers,Comet Pan-STARRS got its moniker from the telescope array used to discover it, the Panoramic Survey Telescope and Rapid Response System in Hawaii.

Black holes seem to pique everyone’s interest. From the first theories to the first (indirect) observations, pretty much everyone has wanted to know more.

Unfortunately, black holes have remained notoriously tight-lipped with their secrets; by definition, these objects are so massive and compact that light itself cannot escape their gravitational influence, which makes studying them directly almost impossible.

Most of what we know about black holes has been inferred from their influence on the objects around them, such as the incredibly fast stars that orbit the supermassive black hole in the center of our galaxy (a relatively lightweight juggernaut that weighs in at merely millions of times the mass of the Sun). Other galaxies may have similar black holes within them, but this has been speculation until now.

In a recent paper from Tim Davis, of the University of Hertfordshire, scientists can observe the carbon dioxide clouds in the center of some galaxies to measure (again indirectly, but with great precision) the mass of black holes contained within. By watching the carbon dioxide molecules “circling the drain” these scientist have developed a new way to determine the mass of very distant black holes, ones so far away that there was no hope of ever seeing individual stars in orbit around them.

These distant galaxies are important to scientists for a number of reasons, but perhaps the biggest is that since they lie so far away, light takes millions or billions of years to span that distance. The further away a galaxy, the further “back in time” we see it! By observing these distant galaxies, scientist are hoping to determine the role these supermassive black holes play in the formation of galaxies and perhaps better understand our own galaxy’s evolution and how we came to be within it.

Josh Roberts is a program presenter and astronomer at the California Academy of Sciences. He also contributes content to Morrison Planetarium productions.

Image courtesy of University of Hertfordshire