Has Voyager 1 finally left the Solar System?

An answer to this question has been proclaimed so many times in the last few years that it has almost lost its effect. Part of the confusion lies in how we define “solar system.” Is it the edge of planetary orbits or the end of the Sun’s influence…or is there yet another definition?

Launched in 1977, the craft has been hurtling through space at an incredible 38,000 miles per hour, sprinting nearly 1,000,000 miles per day. It passed the orbit of the farthest planet Neptune on August 25, 1989 (at the time, due to its highly elliptical orbit, the then-planet Pluto was closer to the Sun than Neptune). Its twin spacecraft, Voyager 2, actually flew close to the planet itself. In 1990, with their planetary missions accomplished, both Voyager missions were renamed the Voyager Interstellar Mission. This consists of three phases: detection of the termination shock (the edge of the Sun’s magnetic influence, where the solar wind slows); exploration of the heliopause (the interface between the solar wind and the interstellar wind); and exploration of interstellar space (the region where the interstellar wind dominates). In December 2004, Voyager crossed the termination shock. Roughly ten years later, the craft was expected to transverse the heliopause, which many consider the edge of the Solar System.

And on August 25, 2012, 35 years after its launch and 12 billion miles (125.3 AU) from the Sun, Voyager 1 officially crossed into interstellar space.

The determination that the event actually occurred, however, did not come until last week. What took so long?

The Sun ejects plasma material (called the “solar wind”) out into a bubble called the heliosphere. The plasma outside that sphere comes from stellar explosions millions of years ago and has since been dispersed throughout the galaxy. The interaction between the heliosphere and plasma is the boundary between the two.

Voyager was looking to detect that boundary between plasmas; however, it could not do this directly because the plasma detector on Voyager 1 malfunctioned in 1980, just a few years after launch. Instead, scientists measured the magnetic field of the Sun and of the interstellar wind. The change did not manifest as expected, so scientists could not draw a definite conclusion. Another set of instruments on board, two antennae, are able to measure plasma—but only if it is moving in waves. A solar eruption in March 2012 sent a shock wave that took 400 days to reach Voyager, but caused the plasma to react in a way that Voyager could detect. This signal finally enabled the confirmation of the craft’s passage into interstellar space.

Sadly, our connection with Voyager will eventually end as its power runs out (its current power output is about that of a refrigerator lightbulb—try detecting that from 11 billion miles away!) The craft is expected to lose all power and cease its communications with Earth by 2025. With no friction to slow it down, however, Voyager will continue to drift on, indefinitely. It remains well within the sphere of the Sun’s gravitational dominion, but will take about 30,000 years to pass through the Oort cloud, the cometary halo extending about a light year or so from the Sun and the farthest-known objects orbiting the Sun. So although the plucky spacecraft has entered interstellar space and left the Sun’s magnetic influence, the Voyager team says it will not yet leave the Solar System until it passes through the Oort Cloud. Beyond that, it will take another 70,000 years to travel the 4.3 light year distance between us and the next closest star, Alpha Centari.

But let’s not underestimate the significance of this event. A man-made object has left the confines of the tiny speck of our galactic home for the very first time and entered the space between stars. We have physically entered a space greater than any explored before and taken the first step in ever visiting other star systems. True, it is a mere 16 light hours, but substantially farther than the 1.3 light seconds to the Moon, which is the farthest that humans have gone.

Voyager leads the way in a whole new frontier of exploration.

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

The newest cosmic mystery: four distinct high-energy flashes! (Is the Universe trying to get our attention?) Astronomers are calling them Fast Radio Bursts, but we have yet to determine their origins.

Radio astronomers detected the first burst about six years ago, but it seemed so strange that many people thought it was a fluke. Dan Thornton, a PhD student at England’s University of Manchester and Australia’s Commonwealth Scientific and Industrial Research Organization, decided to investigate. He spent the next six years looking for these strange flashes.

So far Thornton and his team have found four radio bursts. Astonishingly, the flashes—taken from only a small section of the sky—indicate that there should be one of these signals going off every ten seconds.

“The bursts last only a tenth of the blink of an eye,” explained Max-Planck Institute Director and Manchester professor, Michael Kramer. “With current telescopes we need to be lucky to look at the right spot at the right time. But if we could view the sky with ‘radio eyes’ there would be flashes going off all over the sky every day.”

Astronomers have ruled out terrestrial sources for the Fast Radio Bursts and the origins in the high galactic latitudes suggest that they originate from beyond the Milky Way.

The brightness and distance of the mysterious flashes also hint that they originated when the Universe was about half its current age. “They have come such a long way that by the time they reach the Earth, the Parkes telescope would have to operate for one million years to collect enough to have the equivalent energy of a flying mosquito,” said Thornton.

Co-author Professor Matthew Bailes, from the Swinburne University of Technology in Melbourne, Australia, thinks that burst energies indicate that they come from events involving relativistic objects—maybe even from a type of neutron star called a magnetar. “Magnetars can give off more energy in a millisecond than our Sun does in 300,000 years and are a leading candidate for the burst.”

Astronomers have a lot more research to do before we can solve the radio burst puzzle, but the findings may also help crack some other astronomical mysteries. “We are still not sure about what makes up the space between galaxies, so we will be able to use these radio bursts like probes in order to understand more about some of the missing matter in the Universe,” said Ben Stappers, from Manchester’s School of Physics and Astronomy.

So these Fast Radio Bursts could even speed up cosmic discovery!

Alyssa Keimach is an astronomy and astrophysics student at the University of Michigan and interns for the Morrison Planetarium.

Image: Diceman Stephen West

Cause for celebration! The 10,000th near-Earth object (NEO) has been discovered.

Asteroid 2013 MZ5 joined the ranks of asteroids and comets whose orbits pass near Earth. On an astronomical scale, “near” means within 28 million miles…

The Near-Earth Object Program looks for all NEOs, especially large ones with the potential to harm Earth (called a Potentially Hazardous Asteroid). This type of candidate would need to be at least about 100 feet (about 30 meters) across to do significant damage a populated area—and about 3,200 feet (nearly a kilometer) in diameter to cause global devastation.

As you might expect, large asteroids are easier to find than small ones. NASA estimates that we have discovered all but a few dozen of the largest asteroids, those 460 feet (140 meters) in diameter or larger. (Whew!) Therefore, NASA is shifting its attention to medium-sized threats. If 90% of these were found, the threat of an unexpected impact would be greatly reduced, perhaps even to one percent!

“Finding 10,000 near-Earth objects is a significant milestone,” said Lindley Johnson, program executive for NASA’s Near-Earth Object Observations Program. “But there are at least 10 times that many more to be found before we can be assured we will have found any and all that could impact and do significant harm to the citizens of Earth.”

Discovered by the Pan-STARRS-1 telescope in Hawaii, this new asteroid is about 1,000 feet in diameter. That would put it in a pretty dangerous category if it were headed toward Earth, but its orbit does not pass close enough to us to be a significant threat.

“The first near-Earth object was discovered in 1898,” said Don Yeomans, manager of the Near-Earth Object Program Office at NASA’s Jet Propulsion Laboratory. “Over the next hundred years, only about 500 had been found. But then, with the advent of NASA’s NEO Observations program in 1998, we’ve been racking them up ever since. And with new, more capable systems coming on line, we are learning even more about where the NEOs are currently in our solar system, and where they will be in the future.”

A privately-funded mission called Sentinel might extend the search with a space-based telescope that will likely identify hundreds of thousands of NEOs. You can watch Science Today story on Sentinel or watch an animation narrated by former astronaut Ed Lu describing the mission.

10,000 down, how many to go…?

Alyssa Keimach is an astronomy and astrophysics student at the University of Michigan and interns for the Morrison Planetarium.

Image: PS-1/UH

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

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

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

I’m not going to get into exoplanet announcements such as this one or this one from yesterday morning’s meeting (as one attendee tweeted in summary, “There’s more exoplanets than you can shake an exostick at.”). We have ten press conferences scheduled, and three of them revolve around (pun intended) exoplanet discoveries. So I’ll plan for an exoplanet wrap-up toward the end of the conference.

Instead, I’d like to talk about the work of a few of those spiffy space-based telescopes—yes, the ever-popular Hubble Space Telescope, but also Chandra X-Ray Observatory and a new mission known as NuSTAR.

A grand effort known as the Hubble Ultra Deep Field (HUDF) has imaged the same, small, seemingly-dull part of the sky repeatedly at numerous, finely-tuned wavelengths of light, revealing distant galaxies that reside farther than just about anything we can see. Looking out into space means looking back into time, so the HUDF reveals an important epoch in the history of the Universe.

It turns out the Universe in its youth went through an unusual phase when most of the hydrogen in deep space was in the form of molecules, with no net electrical charge… By the time the Universe reached the age of about 800 million years, however, most of the hydrogen had become ionized, which is to say broken down into electrons and protons (both of which have electrical charge). But it takes energy to ionize hydrogen, so where did that energy come from?

This is the kind of puzzle that keeps astronomers busy (and employed) for decades. Since 2004, astronomers have refined and extended the HUDF observations to eke out more information about this epoch, and the most recent observations have allowed scientists to reach some well-founded, long-sought conclusions.

We know that young galaxies would emit radiation that could ionize the Universe, but can they produce enough radiation to light up the “Cosmic Dawn,” as it’s sometimes called? Astronomers love to come up with more exotic theories, such as the annihilation of dark matter, to explain things like this, but are such puzzling processes required?

Turns out they aren’t. Galaxies can do the job on their own. That’s not the sexiest answer, but it should ultimately feel quite satisfying: the Universe behaves in a way that we understand and can predict. But it took a remarkable amount of sleuthing to come up with this relatively mundane response.

First off, we tally up the galaxies we see, and we estimate how much radiation they would emit. And the first surprise? Small, faint (the researchers like to call ’em “feeble”) galaxies make a significant contribution to the total energy output, and the large, luminous can’t do the job on their own.

Turns out that the currently-observed population of galaxies does not produce enough radiation to ionize all that intergalactic hydrogen. Bummer. But we know that we’re not seeing all the galaxies! We can detect only the brightest ones at these great distances, and the HUDF team’s work suggests that an earlier generation of galaxies existed before the ones we’re seeing. So how can we estimate the energy contribution from what we’re not seeing directly?

The team of astronomers undertook the challenge of tallying the luminous galaxies versus the number of feeble galaxies, and projecting those estimates back in time. Based on HUDF and other observations from, for example, the Wilkinson Microwave Anisotropy Probe (WMAP), we can determine when stars and galaxies started lighting up the Universe, so when the team added up all the light from all the galaxies they estimated to have existed over that time… Bingo! Just enough light energy to ionize the Universe’s hydrogen.

All this work actually pushed Hubble to its limits. And it promises many more discoveries from the James Webb Space Telescope, due to launch in 2018, which will peer back farther in time to see earlier generations of galaxies.

Hubble isn’t alone out there, and x-ray astronomy in particular benefits from having telescopes in space. Stephen S. Murray from Johns Hopkins gave a review of “50 Years of X-Ray Astronomy,” describing remarkable successes in the field. From 1962 to 1999, x-ray astronomy has experienced an increase in sensitivity of 10 billion! (And Murray noted that it took astronomers 400 years to achieve that kind of gain in optical sensitivity…) That kind of revolutionary change has led to spectacular discoveries related to some of the most exotic objects in astronomy—including black holes, pulsars, and supernovae.

An impressive video from Chandra shows a curlicue jet streaming from the pulsar at the center of the Vela Supernova Remnant. This complex structure provides a nifty puzzle for astronomers to describe its origin.

And the recently-launched Nuclear Spectroscopic Telescope Array (NuSTAR), one of the least expensive missions ever launched by NASA, has released its first images. The pair of telescopes spotted two bright, energetic sources of x-rays in the galaxy IC 342—capturing black holes in the process of “feeding” (as NuSTAR team leader Fiona Harrison puts it).

Stay tuned for more spacy stuff the rest of the week…

NuSTAR image courtesy of CalTech

The third Thursday of every month, give or take, Morrison Planetarium hosts “Universe Update” at the 6:30 planetarium shows during NightLife. We select our favorite astronomy stories from the past month, and give a brief run-down of current discoveries while taking audiences on a guided tour of the Universe.

We always start at Earth and work our way out to cosmological distances, and we’ll list the news stories in the same order—from closest to farthest from home.

Let’s start at Mars. Curiosity, the latest addition to our growing team of Martian rovers, landed on the Red Planet just a few months ago.  Previous landers sent back pictures and performed basic measurements, but Curiosity brought an entire geology and chemistry lab on a 225-million-kilometer expedition to Gale Crater, where the rover is using its instruments to search for evidence of Mars’s past.

In its “rocknest,” Curiosity found wind-swept dunes containing material similar to volcanic soil in Hawaii.  After vaporizing samples with its onboard laser, Curiosity’s CheMin instrument then used X-ray diffraction to search for clues to understanding the history of Mars’s atmosphere.  Evidence suggests that Mars once had a much thicker atmosphere, which disappeared a long time ago, leaving the thin layer we observe today.  As previous landers found layers of frozen water beneath Mars’s surface, Curiosity is taking the next step, equipped to hunt for methane, an organic molecule that’s a good indicator of life.  So far, Gale Crater seems devoid of this malodorous precursor, but Curiosity has two years and many kilometers of Martian soil to cover.

Our next stop is the giant asteroid Vesta: over 500 kilometers in diameter (the distance from San Francisco to Los Angeles), it’s the second-largest asteroid in our solar system.  The Dawn mission photographed it for over a year, looking at Vesta as a good example of what Earth may have looked like when it was just a wee baby protoplanet.  The big differences between light and dark in these photos puzzled scientists, since asteroid terrain isn’t usually so varied.  Space weathering should homogenize the surface, leaving a matte gray all over the surface.  But scientists now think that the dark material comes not from Vesta but from 300 smaller asteroid impacts over the last 3.5 billion years, each of which brought material such as the metallic dust, carbon, and hydrated minerals (minerals containing water) Dawn detected.  This mélange can account for the difference in light and dark areas, wrapping Vesta in powdered asteroid debris, one-to-two meters thick.

With a constant influx of data, astronomers are discovering new exoplanets faster than ever.  Re-examining old data can produce useful results, too, and astronomers have just announced that a planet somewhere between Earth- and Neptune-sized is orbiting HD 40307.  Despite only being three quarters as massive as our Sun, this star hosts six planets in total.  Most importantly, the new planet is orbiting right in that habitable sweet spot: not too cold and not too hot, this is a strong contender to have liquid water, that necessary ingredient for life on Earth (and very possibly elsewhere).

Our view of the stars from Earth is strictly two-dimensional, and even with visualizations like the planetarium’s Digital Universe, we still rely on our Earth-bound view to determine distances to objects in space.  A new image (see above) from a 340-megapixel camera on a telescope in Hawaii has found a heretofore unidentified cluster of stars in the familiar Orion constellation.  The most studied part of our night sky, the Orion Nebula turns out to have many layers, and the stars we see in the middle are in fact older stars closer to us than we previously suspected.

Two twelve-billion-year-old supernovae live far, far from our starting point on Earth: because looking out into space also means looking back in time, the Universe has changed a lot since these stars exploded, so it’s hard to give you a distance in kilometers or even lightyears, but one of them holds the record as the most distant supernova yet observed.  Needless to say, these are very, very old explosions that came from even older, supermassive stars, the likes of which don’t exist in the nearby, more recent Universe.

As the Universe continues to accelerate outward, the light we can see here on Earth fades into the cosmos.  In a few billion years, information from these distant galaxies simply won’t make it to Earth anymore, and we’ll be living in a rather empty neighborhood.  The parallels with the economic downturn are a little alarming, and a press release from a group of European cosmologists hammers it home.  It turns out that stars in the Universe are only forming at 1/30 the rate they once were: a cosmic market crash that looks to continue till the end of time.  The Universe seemed to peak about 11 billion years ago… Let’s hope the same isn’t true for the American GDP!

Dan Brady is a planetarium presenter at the California Academy of Sciences. He earned his BS in Physics from UCLA and has taught science since 2008.

Image: CFHT/Coelum (J.-C. Cuillandre & G. Anselmi)

The galaxy, dubbed with the melodic name MACS 1149-JD, was spotted using  the combined power of NASA’s Spitzer and Hubble space telescopes as well as the phenomenon of gravitational lensing – using the gravity of nearer massive galaxies to bend and magnify the light of more distant ones behind them, which would otherwise remain invisible.

Small and compact, the galaxy appears to contain the equivalent of only about 1 percent of the Milky Way’s mass. The galaxy is quite young, only about 200 million years old, but we see it far back in time, when the Universe was quite young. (Imagine looking at an old photograph of your great grandparents: an old image showing a perhaps quite young couple.)  Light from the young galaxy captured by the orbiting observatories shone forth when the 13.7-billion-year-old Universe was just 500 million years old.

MACS 1149-JD existed during an important era when the Universe began to emerge from the cosmic Dark Ages. During this period, the Universe went from a dark, starless expanse to a recognizable cosmos full of galaxies. The discovery of the faint, small galaxy opens up a window into the deepest, remotest periods of cosmic history.

“This galaxy is the most distant object we have ever observed with high confidence,” says Wei Zheng, lead researcher on a paper appearing in Nature this week. “Future work involving this galaxy—as well as others like it that we hope to find—will allow us to study the universe’s earliest objects and how the Dark Ages ended.”

According to leading cosmological theories, the first galaxies should have started out tiny like MACS 1149-JD. They then progressively merged, eventually accumulating into the sizable galaxies of the more modern universe.

These first galaxies likely played the dominant role in the “epoch of reionization,” the event that signaled the demise of the universe’s dark ages. This epoch began about 400,000 years after the Big Bang when neutral hydrogen gas formed from cooling particles. The first luminous stars and their host galaxies emerged a few hundred million years later. The energy released by these earliest galaxies is thought to have caused the neutral hydrogen strewn throughout the Universe to ionize, or lose an electron, a state that the gas has remained in since that time.

Astronomers plan to study the rise of the first stars and galaxies and the epoch of reionization with the successor to both Hubble and Spitzer, NASA’s James Webb Telescope, which is scheduled for launch in 2018. The newly described distant galaxy likely will be a prime target.

Image: NASA/ESA/STScI/JHU

The latest Mars rover, Curiosity, will soon begin its adventure on the Red Planet! Curiosity will land in Gale Crater this August 5th.

With less than a month before Curiosity’s landing, Dr. David Blake gave a Benjamin Dean Lecture at the California Academy of Sciences on July 9th, 2012. A senior staff scientist in the Exobiology Branch at NASA Ames Research Center, Dr. Blake designed one of Curiosity’s science instruments, CheMin (Chemistry and Mineralogy).

CheMin will use X-ray diffraction to measure the mineral structure in samples of Mars dust: an X-ray beam shot through a dust sample will scatter in a distinctive pattern that depends on the arrangement of atoms and molecules present in the sample. CheMin also measures the energy of individual X-ray photons to determine what elements make up the sample.

Other important instruments onboard Curiosity will photograph the rover’s surroundings, drill into rock samples, look for traces of organic compounds, and conduct a variety of experiments that earned Curiosity its original name, “Mars Science Laboratory.”

The 900-kilogram roving laboratory requires a landing sequence different from previous, smaller rovers’ landings. Smaller rovers descended to the Martian surface protected by giant airbags, bouncing to a stop before deflating the airbags and beginning operations. Curiosity needs to complete an elaborate series of steps nicknamed the “Seven Minutes of Terror,” so called because NASA engineers have no way to control what happens during the seven minutes it takes the spacecraft to traverse the thickness of the Martian atmosphere. Dr. Blake showed the audience an interesting clip of the simulated landing process…

After its eight-month journey from Earth, the capsule is racing toward Mars. The Aeroshell, on the outside, includes a heat shield that protects the craft during its initial entry into the Martian atmosphere. At a designated point in its descent, the Aeroshell deploys a parachute. The heat shield drops away, and the Sky Crane carrying the rover then separates and executes a controlled descent under its own power before deploying a cable to lower the rover down to a carefully selected landing site. Flight engineers have refined Curiosity’s landing site during the eight-month voyage, pinpointing a relatively small area inside Gale Crater.

For the first few months that Curiosity is surveying Mars, Dr. Blake will live on “Mars time.” The days on Mars are about 40 minutes longer than our 24-hour Earth day, and scientists and engineers will adjust to the longer day, working on the same schedule as the rover. But all this extra time definitely adds up: Dr. Blake compares it to shifting a time zone a day for the duration of the switch, and when he practiced living on Mars time for a week, he didn’t relish the experience.

Keep up to date with Curiosity’s progress here!

Alyssa Keimach is an astronomy and astrophysics student at the University of Michigan and volunteers for the Morrison Planetarium.

Image credit: NASA/JPL-Caltech