This artist’s conception depicts an Earth-like planet orbiting an evolved star that has formed a stunning “planetary nebula.” Earlier in its life, this planet may have been like one of the eight newly discovered worlds orbiting in the habitable zones of their stars. (Image by David A. Aguilar)

Astronomers announced today that they have found eight new planets in the “Goldilocks” zone of their stars, orbiting at a distance where liquid water can exist on the planet’s surface. This doubles the number of small planets (less than twice the diameter of Earth) believed to be in the habitable zone of their parent stars. Among these eight, the team identified two that are the most similar to Earth of any known exoplanets to date.

“Most of these planets have a good chance of being rocky, like Earth,” says lead author Guillermo Torres of the Harvard-Smithsonian Center for Astrophysics (CfA).

These findings were announced today in a press conference at a meeting of the American Astronomical Society.

The two most Earth-like planets of the group are Kepler-438b and Kepler-442b. Both orbit red dwarf stars that are smaller and cooler than our Sun. Kepler-438b circles its star every 35 days, while Kepler-442b completes one orbit every 112 days.

With a diameter just 12 percent bigger than Earth, Kepler-438b has a 70-percent chance of being rocky, according to the team’s calculations. Kepler-442b is about one-third larger than Earth, but still has a 60-percent chance of being rocky.

To be in the habitable zone, an exoplanet must receive about as much sunlight as Earth. Too much, and any water would boil away as steam. Too little, and water will freeze solid.

“For our calculations we chose to adopt the broadest possible limits that can plausibly lead to suitable conditions for life,” says Torres.

Kepler-438b receives about 40 percent more light than Earth. (In comparison, Venus gets twice as much solar radiation as Earth.) As a result, the team calculates it has a 70 percent likelihood of being in the habitable zone of its star.

Kepler-442b get about two-thirds as much light as Earth. The scientists give it a 97 percent chance of being in the habitable zone.

“We don’t know for sure whether any of the planets in our sample are truly habitable,” explains second author David Kipping of the CfA. “All we can say is that they’re promising candidates.”

Prior to this, the two most Earth-like planets known were Kepler-186f, which is 1.1 times the size of Earth and receives 32 percent as much light, and Kepler-62f, which is 1.4 times the size of Earth and gets 41 percent as much light.

The team studied planetary candidates first identified by NASA’s Kepler mission. All of the planets were too small to confirm by measuring their masses. Instead, the team validated them by using a computer program called BLENDER to determine that they are statistically likely to be planets. BLENDER was developed by Torres and colleague Francois Fressin, and runs on the Pleaides supercomputer at NASA Ames. This is the same method that has been used previously to validate some of Kepler’s most iconic finds, including the first two Earth-size planets around a Sun-like star and the first exoplanet smaller than Mercury.

After the BLENDER analysis, the team spent another year gathering follow-up observations in the form of high-resolution spectroscopy, adaptive optics imaging, and speckle interferometry to thoroughly characterize the systems.

Those follow-up observations also revealed that four of the newly validated planets are in multiple-star systems. However, the companion stars are distant and don’t significantly influence the planets.

As with many Kepler discoveries, the newly found planets are distant enough to make additional observations challenging. Kepler-438b is located 470 light-years from Earth while the more distant Kepler-442b is 1,100 light-years away.

The paper reporting these results has been accepted for publication in The Astrophysical Journal and is available online.

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This artist’s depiction shows a gas giant planet rising over the horizon of an alien waterworld. New research shows that oceans on super-Earths, once established, can last for billions of years. (Image by David A. Aguilar)

For life as we know it to develop on other planets, those planets would need liquid water, or oceans. Geologic evidence suggests that Earth’s oceans have existed for nearly the entire history of our world. But would that be true of other planets, particularly super-Earths? New research suggests the answer is yes and that oceans on super-Earths, once established, can last for billions of years.

“When people consider whether a planet is in the habitable zone, they think about its distance from the star and its temperature. However, they should also think about oceans, and look at super-Earths to find a good sailing or surfing destination,” says lead author Laura Schaefer of the Harvard-Smithsonian Center for Astrophysics (CfA).

Schaefer presented her findings today in a press conference at a meeting of the American Astronomical Society.

Even though water covers 70 percent of Earth’s surface, it makes up a very small fraction of the planet’s overall bulk. Earth is mostly rock and iron; only about a tenth of a percent is water.

“Earth’s oceans are a very thin film, like fog on a bathroom mirror,” explains study co-author Dimitar Sasselov (CfA).

However, Earth’s water isn’t just on the surface. Studies have shown that Earth’s mantle holds several oceans’ worth of water that was dragged underground by plate tectonics and subduction of the ocean seafloor. Earth’s oceans would disappear due to this process, if it weren’t for water returning to the surface via volcanism (mainly at mid-ocean ridges). Earth maintains its oceans through this planet-wide recycling.

Schaefer used computer simulations to see if this recycling process would take place on super-Earths, which are planets up to five times the mass, or 1.5 times the size, of Earth. She also examined the question of how long it would take oceans to form after the planet cooled enough for its crust to solidify.

She found that planets two to four times the mass of Earth are even better at establishing and maintaining oceans than our Earth. The oceans of super-Earths would persist for at least 10 billion years (unless boiled away by an evolving red giant star).

Interestingly, the largest planet that was studied, five times the mass of Earth, took a while to get going. Its oceans didn’t develop for about a billion years, due to a thicker crust and lithosphere that delayed the start of volcanic outgassing.

“This suggests that if you want to look for life, you should look at older super-Earths,” Schaefer says.

Sasselov agrees. “It takes time to develop the chemical processes for life on a global scale, and time for life to change a planet’s atmosphere. So, it takes time for life to become detectable.”

This also suggests that, assuming evolution takes place at a similar rate to Earth’s, you want to search for complex life on planets that are about five and a half billion years old, a billion years older than Earth.

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1. Centaurus A – A split-personality elliptical galaxy

Centaurus A isn’t your typical elliptical galaxy. Its most striking feature is a dark dust lane across its middle – a sign that it swallowed a spiral galaxy about 300 million years ago. Beyond the gas and the dust, a team of Smithsonian scientists unveiled a hidden spiral within the galaxy’s core. Read more…

(Photo: ESO)

 2. The Orion Nebula, one of the star-forming regions used to measure the size and heft of our galaxy

Have you ever thought about how big our home galaxy, the Milky Way, is? Smithsonian scientists have shown that the Milky Way is bigger and more massive than previous data suggested, putting us on equal footing with our neighbor, the Andromeda spiral galaxy. Read more…

The Orion Nebula (Photo: NASA)

 3. Supermassive black hole spins super fast

Imagine a sphere more than 2 million miles across – eight times the distance from Earth to the Moon – spinning so fast that its surface is traveling at nearly the speed of light. Such an object exists: the supermassive black hole at the center of the spiral galaxy NGC 1365. Read more…

In this artist’s conception a supermassive black hole is surrounded by a hot accretion disk, while some in-spiraling material is funneled into a wispy blue jet. (Photo: NASA/JPL-Caltech)

 4. NASA’s eye on the sun delivers stunning images

This photograph of the sun was taken by the Atmospheric Imaging Assembly. The color red shows emission from ionized helium at a temperature of 140,000 Fahrenheit, while green shows ionized iron at a temperature of 1,800,000 F. Read more…

Photo: NASA.

 5. Distant, dying star gives astronomers preview of the fate of our Sun

Some 550 light-years from Earth, a star very much like our Sun is writhing in its death throes. Chi Cygni has swollen in size to become a red giant star so large that it would swallow every planet out to Mars in our solar system. Moreover, it has begun to pulse dramatically in and out, beating like a giant heart. Close-up photos of the surface of this distant star has given scientists a look into the fate of our Sun five billion years from now, when it will near the end of its life. Read more…

Chi Cygni – artist’s conception

Want to know more about the photos featured in the video? Read the articles!

1. Alien Earths may have formed in Universe earlier than expected

2. New image of the star-forming region 30 Doradus, also known as the Tarantula Nebula

3. Astronomers in distant future might still deduce the Big Bang origin of the Universe

4. Pulverized planet dust might lie around double stars

5. Cosmic “baby photos” of distant solar systems lend insight as to how planets form

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This artist’s conception portrays the first planet discovered by the Kepler spacecraft during its K2 mission. A transit of the planet was teased out of K2’s noisier data using ingenious computer algorithms developed by a CfA researcher. The newfound planet, HIP 116454b, has a diameter of 20,000 miles (two and a half times the size of Earth) and weighs 12 times as much. It orbits its star once every 9.1 days. (Image by
David A. Aguilar)

To paraphrase Mark Twain, the report of the Kepler spacecraft’s death was greatly exaggerated. Despite a malfunction that ended its primary mission in May 2013, Kepler is still alive and working. The evidence comes from the discovery of a new super-Earth using data collected during Kepler’s “second life.”

“Like a phoenix rising from the ashes, Kepler has been reborn and is continuing to make discoveries. Even better, the planet it found is ripe for follow-up studies,” says lead author Andrew Vanderburg of the Harvard-Smithsonian Center for Astrophysics (CfA).

NASA’s Kepler spacecraft detects planets by looking for transits, when a star dims slightly as a planet crosses in front of it. The smaller the planet, the weaker the dimming, so brightness measurements must be exquisitely precise. To enable that precision, the spacecraft must maintain a steady pointing.

Kepler’s primary mission came to an end when the second of four reaction wheels used to stabilize the spacecraft failed. Without at least three functioning reaction wheels, Kepler couldn’t be pointed accurately.

NASA’s Kepler spacecraft has identified more than 996 confirmed exoplanets, ranging in size from Earth to Jupiter, in more than 400 stellar systems.  (Image credit: NASA)

Rather than giving up on the plucky spacecraft, a team of scientists and engineers developed an ingenious strategy to use pressure from sunlight as a virtual reaction wheel to help control the spacecraft. The resulting second mission, K2, promises to not only continue Kepler’s search for other worlds, but also introduce new opportunities to observe star clusters, active galaxies, and supernovae.

Due to Kepler’s reduced pointing capabilities, extracting useful data requires sophisticated computer analysis. Vanderburg and his colleagues developed specialized software to correct for spacecraft movements, achieving about half the photometric precision of the original Kepler mission.

Kepler’s new life began with a 9-day test in February 2014. When Vanderburg and his colleagues analyzed that data, they found that Kepler had detected a single planetary transit.

They confirmed the discovery with radial velocity measurements from the HARPS-North spectrograph on the Telescopio Nazionale Galileo in the Canary Islands. Additional transits were weakly detected by the Microvariability and Oscillations of STars (MOST) satellite.

The newfound planet, HIP 116454b, has a diameter of 20,000 miles, two and a half times the size of Earth. HARPS-N showed that it weighs almost 12 times as much as Earth. This makes HIP 116454b a super-Earth, a class of planets that doesn’t exist in our solar system. The average density suggests that this planet is either a water world (composed of about three-fourths water and one-fourth rock) or a mini-Neptune with an extended, gaseous atmosphere.

This close-in planet circles its star once every 9.1 days at a distance of 8.4 million miles. Its host star is a type K orange dwarf slightly smaller and cooler than our sun. The system is 180 light-years from Earth in the constellation Pisces.

Since the host star is relatively bright and nearby, follow-up studies will be easier to conduct than for many Kepler planets orbiting fainter, more distant stars.

“HIP 116454b will be a top target for telescopes on the ground and in space,” says Harvard astronomer and co-author John Johnson of the CfA.

The research paper reporting this discovery has been accepted for publication in The Astrophysical Journal.

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An artist’s impression of the debris disk around HD 107146. This adolescent star system shows signs that in its outer reaches, swarms of Pluto-size objects are jostling nearby smaller objects, causing them to collide and “kick up” considerable dust.
(Graphic by A. Angelich, NRAO/AUI/NSF)

Astronomers using the Atacama Large Millimeter/submillimeter Array (ALMA) may have detected the dusty hallmarks of an entire family of Pluto-size objects swarming around an adolescent version of our own Sun.

By making detailed observations of the protoplanetary disk surrounding the star known as HD 107146, the astronomers detected an unexpected increase in the concentration of millimeter-size dust grains in the disk’s outer reaches. This surprising increase, which begins remarkably far — about 13 billion kilometers — from the host star, may be the result of Pluto-size planetesimals stirring up the region, causing smaller objects to collide and blast themselves apart.

Dust in debris disks typically consists of material left over from the formation of planets. Very early in the lifespan of the disk, this dust is continuously replenished by collisions of larger bodies, such as comets and asteroids. In mature solar systems with fully formed planets, comparatively little dust remains. In between these two ages — when a solar system is in its awkward teenage years — certain models predict that the concentration of dust would be much denser in the most distant regions of the disk. This is precisely what ALMA has found.

ALMA image of the dust surrounding the star HD 107146. Dust in the outer reaches of the disk is thicker than in the inner regions, suggesting that a swarm of Pluto-size planetesimals is causing smaller objects to smash together. The dark ring-like structure in the middle portion of the disk may be evidence of a gap where a planet is sweeping its orbit clear of dust. Image courtesy L. Ricci, ALMA (NRAO/NAOJ/ESO) and B. Saxton (NRAO/AUI/NSF)

“The dust in HD 107146 reveals this very interesting feature — it gets thicker in the very distant outer reaches of the star’s disk,” said Luca Ricci, an astronomer at the Harvard-Smithsonian Center for Astrophysics (CfA), and lead author on a paper accepted for publication in the Astrophysical Journal. At the time of the observations, Ricci was with the California Institute of Technology.

“The surprising aspect is that this is the opposite of what we see in younger primordial disks where the dust is denser near the star. It is possible that we caught this particular debris disk at a stage in which Pluto-size planetesimals are forming right now in the outer disk while other Pluto-size bodies have already formed closer to the star,” said Ricci.

According to current computer models, the observation that the density of dust is higher in the outer regions of the disk can only be explained by the presence of recently formed Pluto-sized bodies. Their gravity would disturb smaller planetesimals, causing more frequent collisions that generate the dust ALMA sees.

The new ALMA data also hint at another intriguing feature in the outer reaches of the disk: a possible “dip” or depression in the dust about 1.2 billion kilometers wide, beginning approximately 2.5 times the distance of the Sun to Neptune from the central star. Though only suggested in these preliminary observations, this depression could be a gap in the disk, which would be indicative of an Earth-mass planet sweeping the area clear of debris. Such a feature would have important implications for the possible planet-like inhabitants of this disk and may suggest that Earth-size planets could form in an entirely new range of orbits than have ever been seen before.

The star HD 107146 is of particular interest to astronomers because it is in many ways a younger version of our own Sun. It also represents a period of transition from a solar system’s early life to its more mature, final stages where planets have finished forming and have settled into their final orbits around their host star.

“This system offers us the chance to study an intriguing time around a young, Sun-like star,” said ALMA Deputy Director and coauthor Stuartt Corder. “We are possibly looking back in time here, back to when the Sun was about 2 percent of its current age.”

The star HD 107146 is located approximately 90 light-years from Earth in the direction of the constellation Coma Berenices. It is approximately 100 million years old. Further observations with ALMA’s new long-baseline, high-resolution capabilities will shed more light on the dynamics and composition of this intriguing object.

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This artist’s conception shows the super-Earth 55 Cancri e (right) compared to the Earth (left). Astronomers using a ground-based telescope have measure the transit of 55 Cancri e for the first time. It is the shallowest transit ever detected from the ground. (NASA/JPL image)

Astronomers have measured the passing of a super-Earth in front of a bright, nearby Sun-like star using a ground-based telescope for the first time. The transit of the exoplanet 55 Cancri e is the shallowest detected from the ground yet. Since detecting a transit is the first step in analyzing a planet’s atmosphere, this success bodes well for characterizing the many small planets that upcoming space missions are expected to discover in the next few years.

The international research team used the 2.5-meter Nordic Optical Telescope on the island of La Palma, Spain, a moderate-sized facility by today’s standards but equipped with state-of-the-art instruments, to make the detection. Previous observations of this planet transit had to rely on space-borne telescopes.

The host star, 55 Cancri, is located just 40 light-years away from us and is visible to the naked eye. During its transit, the planet crosses 55 Cancri and blocks a tiny fraction of the starlight, dimming the star by 1/2000th (or 0.05%) for almost two hours. This shows that the planet is about twice the size of Earth, or 16,000 miles in diameter.

“Our observations show that we can detect the transits of small planets around Sun-like stars using ground-based telescopes,” says Ernst de Mooij of Queen’s University Belfast in the United Kingdom, lead author of the study.

He continues, “This is especially important because upcoming space missions such as TESS and PLATO should find many small planets around bright stars and we will want to follow up the discoveries with ground-based instruments.”

The Nordic Optical Telescope is located at the Roque de los Muchachos Observatory on the island of La Palma, Spain.

TESS is a NASA mission scheduled for launch in 2017, while PLATO is to be launched in 2024 by the European Space Agency; both will search for transiting terrestrial planets around nearby bright stars.

“With this result we are also closing in on the detection of the atmospheres of small planets with ground-based telescopes,” says co-author Mercedes Lopez-Morales of the Harvard-Smithsonian Center for Astrophysics. “We are slowly paving the way toward the detection of bio-signatures in Earth-like planets around nearby stars.”

“It’s remarkable what we can do by pushing the limits of existing telescopes and instruments, despite the complications posed by the Earth’s own turbulent atmosphere,” says study co-author Ray Jayawardhana of York University in Canada. “Remote sensing across tens of light-years isn’t easy, but it can be done with the right technique and a bit of ingenuity.”

The planet 55 Cancri e is about twice as big and eight times as massive as Earth. With a period of 18 hours, it is the innermost of five planets in the system. Because of its proximity to the host star, the planet’s dayside temperature reaches over 3100° Fahrenheit (1700° Celsius), hot enough to melt metal, with conditions far from hospitable to life. Initially identified a decade ago through radial velocity measurements, it was later confirmed through transit observations with the MOST and Spitzer space telescopes.

Until now, the transits of only one other super-Earth, GJ 1214b circling a red dwarf, had been observed with ground-based telescopes. The Earth’s roiling air makes such observations extremely difficult. But the team’s success with 55 Cancri e raises the prospects of characterizing dozens of super-Earths likely to be revealed by upcoming surveys.

“We expect these surveys to find so many nearby, terrestrial worlds that space telescopes simply won’t be able to follow up on all of them. Future ground-based instrumentation will be key, and this study shows it can be done,” adds Lopez-Morales.

The research team also includes Raine Karjalainen and Marie Hrudkova of the Isaac Newton Group of Telescopes. Their findings appear in a paper to be published in The Astrophysical Journal Letters.

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Philae’s touchdown on the comet – artist’s depiction .(Image: DLR German Aerospace Center)

A few images of comet 67P/Churyumov-Gerasimenko just sent back by the European spaceship Rosetta appear to be a snowboarder’s dream: pristine slopes covered in powder. Yet one mogul would easily be enough to launch a snowboarder deep into space. At only 2.5 miles wide the comet has an extremely weak gravity. That’s why Rosetta’s probe Philae must be anchored to the comet’s surface or otherwise it may fall off.

Since 1950 comets and snow have been synonymous after Smithsonian astronomer Fred Whipple published a landmark paper describing the composition of comet nuclei as icy conglomerates, or dirty snowballs, composed of ice water, ammonia, methane and dust. People previously believed comets were formless floating sand banks made up of loose particles.

Now 64 years later, the spaceship Rosetta has landed a probe on comet 67P/Churyumou-Gerasimenko’s icy surface. Here geologist Tom Watters of the Center for Earth and Planetary Studies at the Smithsonian’s National Air and Space Museum answers a few questions about this remarkable achievement.

Q: What is your first take on this achievement?

Watters: I just think it is another milestone in planetary exploration. To be able to successfully land this probe–modest in scale yet very ambitious if you look at its suite of instruments—on a comet 315 million miles away is amazing.

This is certainly an unusual comet, dumbbell shaped with sharp topographic features and remarkably bouldered, not what I would have envisioned.

Q: A comet moves through empty space yet leaves a trail of water vapor. What erosive process is removing this material from the comet’s surface?

Watters: It’s actually radiation pressure—the mix of light and charged particles coming from the sun. The photons and charged particles strike the comet to exert a small amount of pressure that sends the comet’s water vapor and dust away, thus the tail of gas and dust.

This enhanced image of Comet C/2012 S1 (ISON) reveals the subtle structure in the inner coma of the comet. (Image: NASA HQ)

Q: Was this comet once part of a larger icy planet?

Watters: Many comets are located in the Kuiper Belt, an area outside our Solar System and some are of fairly good size—some comparable in size with Pluto.

Comets are incredibly primitive material some 4.6 billion years old. They are building blocks left over from a period in the early solar system when the planets were accreting. Everything we know in our solar system was once formed from the accretion of cometary material.

Q: What do they hope to learn from the landing of the probe Philae on this comet?

Watters: Comets are the collectors of that first material that formed as the solar nebula cooled, so one of the big questions is: Was the liquid water that we have on Earth delivered to it by comets?

A second thing they are certainly going to be looking for is what kind or organic compounds are present on this comet. If so, did comets seed the building blocks of life on planet earth?

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This galactic fireworks display is taking place in NGC 4258 (also known as M106), a spiral galaxy like the Milky Way. (Image credit: NASA/CXC/JPL-Caltech/STScI/NSF/NRAO/VLA)

Unless you live under a lunar rock, you’ve probably heard about or seen director Christopher Nolan’s latest blockbuster “Interstellar.” Starring Anne Hathaway and Matthew McConaughey, the movie explores the possibility of humans leaving Earth, which has become devastated by severe drought and famine, for another planet. While the idea seems far-fetched, astronomers do know there are planets out there that mirror some of Earth’s features and leave open the possibility for life to exist. These exoplanets revolve around stars like our own sun but are far beyond our solar system. Here are some recently discovered facts about planets, and the search for planets, that may possibly support life.

1. The “Mega-Earth”

“Mega-Earth” Kepler-10c dominates the foreground in this artist’s conception. Its sibling, the lava world Kepler-10b, is in the background. Both orbit a sunlike star. Kepler-10c has a diameter of about 18,000 miles, 2.3 times as large as Earth, and weighs 17 times as much. Therefore it is all solids, although it may possess a thin atmosphere shown here as wispy clouds. (David A. Aguilar, CfA)

Discovered in June 2014, Kepler-10c or “Mega-Earth,” as it’s been dubbed, lives in the constellation Draco, 560 light-years away. Kepler-10c orbits the old star of the Kepler system, formed around 11 billion years ago. A planet of Mega-Earth’s size and mass—mostly rock—was previously thought impossible, especially since it was formed when the universe was mostly gaseous. Its diameter is more than two times as large as Earth, and it is nearly 17 times heavier. Research on Kepler-10c “implies that astronomers shouldn’t rule out old stars when they search for Earth-like planets,” because “if old stars can host rocky Earths too, then we have a better chance of locating potentially habitable worlds in our cosmic neighborhood.” Good news!

2. Kepler-56b and Kepler-56c

In this artist’s conception, the doomed world Kepler-56b is being tidally shredded and consumed by its aging host star. New research shows that Kepler-56b will be engulfed by its star in about 130 million years, while its sibling Kepler-56c will be swallowed in 155 million years. This is the first time that two known exoplanets in a single system have a predicted “time of death.” (David A. Aguilar, CfA)

Some like it hot, but planets Kepler-56b and Kepler-56c might be too close to a blistering star for comfort. According to Gongjie Li of the Harvard-Smithsonian Center for Astrophysics, Kepler-56b and Kepler-56c—exoplanets that orbit the Kepler-56 star, which shines about 2,800 light-years from Earth—will be swallowed by the star in a relatively short amount of time. “As far as we know, this is the first time two known exoplanets in a single system have a predicted ‘time of death,’” Li said. These planets are located very close to the Kepler-56 star, closer than Mercury is to the sun in our solar system. Because the star will continue to grow, the two planets will be subjected to immense heat while their atmospheres boil away.

3. Red-dwarf Planets

This artist’s conception shows a hypothetical alien world orbiting a red dwarf star. Although it is in the star’s habitable zone, this planet faces an extreme space environment that is stripping its atmosphere and generating powerful aurorae. Since they are subjected to such harsh physical conditions, red-dwarf planets may not be habitable after all, so life in the universe might be even rarer than we thought. (Image by David A. Aguilar, CfA)

In looking for potentially habitable worlds beyond Earth, astronomers have focused on planets orbiting red dwarf stars. These stars are the most common star type, but research is starting to reveal that their orbiting planets may not be the best place to relocate a human population. “The space environment of close-in exoplanets is much more extreme than what the Earth faces,” said Jeremy Drake of the Harvard-Smithsonian Center for Astrophysics. These extreme weather conditions could include constant darkness and brutal stellar winds. “The ultimate consequence is that any planet potentially would have its atmosphere stripped over time.”

4. Planets circling white dwarf stars

In this artist’s conception, the atmosphere of an Earth-like planet displays a brownish haze – the result of widespread pollution. New research shows that the upcoming James Webb Space Telescope potentially could detect certain pollutants, specifically CFCs, in the atmospheres of Earth-sized planets orbiting white dwarf stars. (Image by Christine Pulliam, CfA)

Theorists at the Harvard-Smithsonian Center for Astrophysics have a clever idea: If we look for traces of industrial pollutants on other planets, this may lead to proof of advanced civilizations living on distant worlds. Soon, scientists will be able to use the new, specialized James Webb Space Telescope, which should be able to detect ozone-destroying chemicals, like those found in solvents and aerosols, on other planets. Of course, there’s a catch. The telescope is only able to detect these pollutants on planets similar to Earth that orbit a white dwarf star. When stars like our sun die, white dwarf stars are what are left behind. The James Webb Space Telescope is cannot detect pollutants on a planet that orbits a star that is still burning like our sun. Nevertheless, this intriguing theory about pollutants in distant planets could very well lead to news of advanced civilizations of extraterrestrials living in a parallel universe to ours. “People often refer to ETs as ‘little green men,’ but the ETs detectable by this method should not be labeled ‘green’ since they are environmentally unfriendly,” said Avi Loeb of Harvard, one of the co-authors of the theory.

5. KOI-314c

KOI-314c, shown in this artist’s conception, is the lightest planet to have both its mass and physical size measured. It orbits a dim, red dwarf star (shown at left) about 200 light-years from Earth. (Image by C. Pulliam & D. Aguilar)

This planet has astonishingly similar attributes to Earth, so maybe we’re on to something! Or maybe not. In January 2014, an international team of astronomers discovered the first exoplanet that has the same mass as Earth. However, its differences from Earth are crucial. KOI-314c has a very low density compared to Earth; it’s only 30 percent denser than water. This means we couldn’t walk on its surface. It’s also much too hot for human life. Estimates put the planet’s temperature at around 220 degrees Fahrenheit. “It [KOI-314c] proves that there is no clear dividing line between rocky worlds like Earth and fluffier planets like water worlds or gas giants,” said David Kipping, the lead author of the discovery from the Harvard-Smithsonian Center for Astrophysics.

Even with ongoing research and incredible discoveries at the hands of skilled scientists, a planet where humans could create lives for themselves away from Earth has yet to be found. Keeping Earth in tip-top shape is clearly our best bet for now.

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The moon passed between the Earth and the sun on Thursday, Oct. 23. While avid stargazers in North America looked up to watch the spectacle, the best vantage point was several hundred kilometers above the North Pole.

Astrophysicist Patrick McCauley from the Smithsonian’s Astrophysical Observatory explains how the Hinode satellite, which has a polar orbit, was in the perfect position to record a very different view of the solar eclipse.

What does the footage from the satellite show?

McCauley: We are looking at an annular eclipse that was observed by an X-ray telescope on the Hinode satellite. An annular eclipse occurs when the moon passes directly between the observer and the sun. In this type of eclipse the moon’s shadow is not quite large enough to cover the full disc of the sun, resulting in a visible ring.

The x-ray telescope on the Hinode satellite is used to monitor the outer atmosphere of the sun, called the corona. The sun’s outer atmosphere is much hotter than its surface. The surface is about 5000 Kelvin and the corona can get up to 10 million Kelvin. That is hot enough to produce X-rays, which is what we are seeing with this telescope.

Why couldn’t we see an annular eclipse from North America?

McCauley: We could only see a partial eclipse because the Moon did not pass directly in front of the sun from our perspective on the ground. Instead, the center of the moon’s shadow was cast above Earth’s north pole, which allowed it to be viewed as an annular from Hinode’s perspective in orbit.

What can scientists learn by recording this solar eclipse?

McCauley: The eclipse observation allows us to better calibrate the instruments aboard Hinode. When the moon passes in front of the sun the detector on the X-ray telescope should go completely dark – you shouldn’t be able to see anything where the moon is. In fact, you do see a little bit of light and that is because of scattered light within the telescope. The eclipse observations allow us to better understand this scattered light and improve calibrations of the instrument.

X-ray image of the solar eclipse observed, on Nov. 3, 2013. (Photo: NASA/Hinode)

What other things do you study with the X-ray telescope?

McCauley: We are very interested in studying solar flares. Flares are most dramatic in X-rays and we’re using the X-ray telescope to better understand the physical mechanisms that drive flares so that they might someday be forecasted. We’re also interested in understanding why the corona is so much hotter than the Sun’s surface. Read more on how tiny nanoflares might heat the Sun’s corona.

Hinode is a Japanese mission developed and launched by the Institute of Space and Astronautical Science (ISAS) /Japan Aerospace Exploration Agency (JAXA), with the National Astronomical Observatory of Japan (NAOJ) as a domestic partner. NASA and the Science & Technology Facilities Council are Hinode international partners. It is operated by these agencies in cooperation with the European Space Agency (ESA) and the Norwegian Space Center (NSC). 

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This image from the Interface Region Imaging Spectrograph (IRIS) shows emission from hot plasma in the Sun’s transition region-the atmospheric layer between the surface and the outer corona. The bright, C-shaped feature at upper center shows brightening in the footprints of hot coronal loops, which is created by high-energy electrons accelerated by nanoflares. The vertical dark line corresponds to the slit of the spectrograph. The image is color-coded to show light at a wavelength of 1,400 Angstroms. The size of each pixel corresponds to about 120 km (75 miles) on the Sun.
(NASA/IRIS image)

Why is the Sun’s million-degree corona, or outermost atmosphere, so much hotter than the Sun’s surface? This question has baffled astronomers for decades. Today, a team led by Paola Testa of the Harvard-Smithsonian Center for Astrophysics (CfA) is presenting new clues to the mystery of coronal heating using observations from the recently launched Interface Region Imaging Spectrograph (IRIS). The team finds that miniature solar flares called “nanoflares” – and the speedy electrons they produce – might partly be the source of that heat, at least in some of the hottest parts of the Sun’s corona.

A solar flare occurs when a patch of the Sun brightens dramatically at all wavelengths of light. During flares, solar plasma is heated to tens of millions of degrees in a matter of seconds or minutes. Flares also can accelerate electrons (and protons) from the solar plasma to a large fraction of the speed of light. These high-energy electrons can have a significant impact when they reach Earth, causing spectacular aurorae but also disrupting communications, affecting GPS signals, and damaging power grids.

Those speedy electrons also can be generated by scaled-down versions of flares called nanoflares, which are about a billion times less energetic than regular solar flares. “These nanoflares, as well as the energetic particles possibly associated with them, are difficult to study because we can’t observe them directly,” says Testa.

This image from the Atmospheric Imaging Assembly on board NASA’s Solar Dynamics Observatory was taken simultaneously with the IRIS observations. It shows emission from hot coronal loops in a solar active region. IRIS observed brightenings occurring at the footpoints of these hot loops. The image is color-coded to show light at a wavelength of 94 Angstroms. The size of each pixel corresponds to about 430 km (270 miles) on the Sun.
(NASA/SDO image)

Testa and her colleagues have found that IRIS provides a new way to observe the telltale signs of nanoflares by looking at the footpoints of coronal loops. As the name suggests, coronal loops are loops of hot plasma that extend from the Sun’s surface out into the corona and glow brightly in ultraviolet and X-rays.

IRIS does not observe the hottest coronal plasma in these loops, which can reach temperatures of several million degrees. Instead, it detects the ultraviolet emission from the cooler plasma (~18,000 to 180,000 degrees Fahrenheit) at their footpoints. Even if IRIS can’t observe the coronal heating events directly, it reveals the traces of those events when they show up as short-lived, small-scale brightenings at the footpoints of the loops.

The team inferred the presence of high-energy electrons using IRIS high-resolution ultraviolet imaging and spectroscopic observations of those footpoint brightenings. Using computer simulations, they modeled the response of the plasma confined in loops to the energy transported by energetic electrons. The simulations revealed that energy likely was deposited by electrons traveling at about 20 percent of the speed of light.

The high spatial, temporal, and spectral resolution of IRIS was crucial to the discovery. IRIS can resolve solar features only 150 miles in size, has a temporal resolution of a few seconds, and has a spectral resolution capable of measuring plasma flows of a few miles per second.

Finding high-energy electrons that aren’t associated with large flares suggests that the solar corona is, at least partly, heated by nanoflares. The new observations, combined with computer modeling, also help astronomers to understand how electrons are accelerated to such high speeds and energies – a process that plays a major role in a wide range of astrophysical phenomena from cosmic rays to supernova remnants. These findings also indicate that nanoflares are powerful, natural particle accelerators despite having energies about a billion times lower than large solar flares.

“As usual for science, this work opens up an entirely new set of questions. For example, how frequent are nanoflares? How common are energetic particles in the non-flaring corona? How different are the physical processes at work in these nanoflares compared to larger flares?” says Testa.

The paper reporting this research is part of a special issue of the journal Science focusing on IRIS discoveries.

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On Sept. 18, 2014, audience members who attended the Observatory Night talk “What is a Planet?” voted to choose one of three possible definitions for a planet. The result: a planet is “the smallest spherical lump of matter than formed around stars or stellar remnants,” and Pluto IS a planet! (Photo: Harvard-Smithsonian CfA)

What is a planet? For generations of kids the answer was easy. A big ball of rock or gas that orbited our Sun, and there were nine of them in our solar system. But then astronomers started finding more Pluto-sized objects orbiting beyond Neptune. Then they found Jupiter-sized objects circling distant stars, first by the handful and then by the hundreds. Suddenly the answer wasn’t so easy. Were all these newfound things planets?

Since the International Astronomical Union (IAU) is in charge of naming these newly discovered worlds, they tackled the question at their 2006 meeting. They tried to come up with a definition of a planet that everyone could agree on. But the astronomers couldn’t agree. In the end, they voted and picked a definition that they thought would work.

Pluto (left) and Charon (right) dominate this view of the outer solar system. Charon is about half the size of Pluto. Pluto also hosts four tiny moons – Nix, Hydra, Kerberos, and Styx – two of which are seen as small crescents at top left and right. In the distance, a faint Sun illuminates dust within the asteroid belt. (Photoo David A. Aguilar, CfA)

The current, official definition says that a planet is a celestial body that:
1. is in orbit around the Sun,
2. is round or nearly round, and
3. has “cleared the neighborhood” around its orbit.

But this definition baffled the public and classrooms around the country. For one thing, it only applied to planets in our solar system. What about all those exoplanets orbiting other stars? Are they planets? And Pluto was booted from the planet club and called a dwarf planet. Is a dwarf planet a small planet? Not according to the IAU. Even though a dwarf fruit tree is still a small fruit tree, and a dwarf hamster is still a small hamster.

Eight years later, the Harvard-Smithsonian Center for Astrophysics decided to revisit the question of “what is a planet?” On September 18th, we hosted a debate among three leading experts in planetary science, each of whom presented their case as to what a planet is or isn’t. The goal: to find a definition that the eager public audience could agree on!

Science historian Dr. Owen Gingerich, who chaired the IAU planet definition committee, presented the historical viewpoint. Dr. Gareth Williams, associate director of the Minor Planet Center, presented the IAU’s viewpoint. And Dr. Dimitar Sasselov, director of the Harvard Origins of Life Initiative, presented the exoplanet scientist’s viewpoint.

Gingerich argued that “a planet is a culturally defined word that changes over time,” and that Pluto is a planet. Williams defended the IAU definition, which declares that Pluto is not a planet. And Sasselov defined a planet as “the smallest spherical lump of matter that formed around stars or stellar remnants,” which means Pluto is a planet.

After these experts made their best case, the audience got to vote on what a planet is or isn’t and whether Pluto is in or out. The results are in, with no hanging chads in sight.

According to the audience, Sasselov’s definition won the day, and Pluto IS a planet.

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Before iPhones and laptops there were human computers, some of whom worked at the Harvard College Observatory. Women like Henrietta Swan Leavitt, Williamina Fleming, and Annie Jump Cannon made some of the most important discoveries in astronomy in the early 20th century. Their work was even featured in the TV series Cosmos, hosted by Neil deGrasse Tyson. Now, Harvard is seeking your help to transcribe the logbooks that record the century-long observations behind (and beyond) their discoveries.

The Horsehead Nebula was discovered on this photographic plate in 1888. It is the dark smudge near the center of the image. The three brightest stars in the field are overexposed, creating the surrounding rings and other image artifacts.
(Harvard College Observatory)

“Digitizing the ~500,000 glass plate images covering the full sky will foster new scientific discoveries for the currently ‘hot’ field of studying variability of astronomical objects, or Time Domain Astronomy, as we bring to light these long-hidden archives,” says Harvard professor Josh Grindlay, the leader of the Digital Access to a Sky Century at Harvard (DASCH) project.

The telescope logbooks record vital information associated with a 100-year-long effort to record images of the sky. By transcribing logbook text to put those historical observations in context, volunteers can help to unlock hidden discoveries.

To participate in this new “citizen scientist” initiative, interested parties are invited to sign up at https://transcription.si.edu/browse?filter=owner:11

We need to transcribe more than 100 logbooks containing about 10,000 pages of text. We seek volunteers to type in a few numbers per line of text onto web-based forms, since optical character recognition (OCR) doesn’t work on these hand-written entries. Harvard is partnering with the Smithsonian Transcription Center to recruit Digital Volunteers. This effort is part of a larger Smithsonian-wide initiative that was publicly launched last month. By transcribing historic documents and collection records, the resources of the Smithsonian and its partners are being brought to a new, global audience via the web.

“By simply typing in selected parts of the logbook entries for each plate, the public can partner with us as we make new discoveries while preserving the past,” explains Harvard Curatorial Assistant David Sliski, who led the effort to make this transcription project possible.

A Century of Sky Observations

Between 1885 and 1992, the Harvard College Observatory (now part of the Harvard-Smithsonian Center for Astrophysics) repeatedly photographed the night sky with telescopes in both the northern and southern hemispheres. As a result the Observatory’s archives hold more than 500,000 glass photographic plates (each 8 by 10 inches), nearly three times as many as the next largest collection in the world.

The DASCH project is conserving the plates by digitizing them on a high-speed scanner (up to 400 plates per day) and measuring the position and brightness of every star or distinct object on each plate. To put the mountains of data in context, each plate scan must be linked to the logbook “metadata” – handwritten entries recording details like the date, time, exposure length, and location on the sky.

The logbook data is required because it is the only record of the date and time for each exposure, which is essential to measure how the brightness and position of each object on each plate changes with time. Without these transcriptions the DASCH project would not be possible.

From just the early phase of “production scanning,” Harvard-Smithsonian scientists have found unexpected phenomena. For example, one rare class of object is a star paired with a black hole, which flares in brightness for a month every 50-100 years. Before DASCH, only two historical outbursts from such star-black hole pairs were known. In the past two years, with fewer than 10 percent of the plates having been digitized, DASCH has found three more. By measuring their historical outbursts and recurrence times, astronomers can deduce how many such systems remain hidden in our Galaxy.

The DASCH project website is http://dasch.rc.fas.harvard.edu. DASCH is supported by grants from the National Science Foundation.

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We’ve seen a serious series of super moons this summer and the show’s not over yet. Mark your calendars: the next one will light up on Tuesday, Sept. 9.

While it may seem sunny and clear up on a super moon, a steady rain of space dust and particles is zipping in and striking the moon day in and day out. Undetectable from Earth, these tiny travelers are moving fast.

“Most particles hit the ground at several kilometers per second or more,” explains Bruce Campbell, a geologist at the Smithsonian’s National Air and Space Museum. “A particle of dust moving at that speed will break a pretty good chunk off a rock.” This particle rain is the dominant erosive effect on the moon, part of an endless process of the rocks being broken down and the dust gradually building up.

This radar image reveals how the lunar impact crater known as Aristillus looks beneath its cover of dust. The radar echoes reveal geologic features of the large debris field created by the force of the impact. The dark “halo” surrounding the crater is due to pulverized debris beyond the rugged, radar-bright rim deposits. The image also shows traces of lava-like features produced when lunar rock melted from the heat of the impact. The crater is approximately 34 miles in diameter and 2 miles deep. Click to enlarge. (Credit: Bruce Campbell, Smithsonian’s National Air and Space Museum; Arecibo/NAIC; NRAO/AUI/NSF)

So what you see when you look at the moon is dust,15- to 60-feet-deep in places, built up over 4 billion years.

Recently, however, Campbell and his colleagues have figured out a way to peek through that dust layer. Two new radar images published recently in the Journal of Geophysical Research show the moon’s true face, and it’s not a pretty picture. The moon’s pockmarked surface tells a violent tale of thousands of meteor and asteroid explosions, ancient lava flows and the passage of billions of years of deep time. Smithsonian Science asked Campbell about these latest images.

Q: How does one take a radar picture of the moon?

Campbell: Radar signals are beamed from a transmitter at the Arecibo Observatory in Puerto Rico, strike the moon, bounce back and are caught by receivers at the National Radio Astronomy Observatory in Green Bank, W.Va. We use radar with a long 70-centimeter wavelength that penetrates through the moon’s dust, sometimes reaching a hard surface below. By measuring minute differences in the time it takes for the radar waves to return, and their radio frequency, we can make an accurate image of the moon’s surface. This technique has been used to study many objects in our Solar System, including asteroids and other planets.

Q: One of your new images is of the impact crater Aristillus. What does it show that can’t be seen in a telescope image?

Campbell: We can see large boulders and fragmented rocks really close to the crater that have been thrown up and flipped over. They didn’t go very far – they were just lifted out of the hole as the meteorite exploded underground. Some of this material slumps back into the hole as the crater forms. Beyond that you can see a dark “halo” of pulverized debris that’s been thrown ballistically, catapulted out and traveling great distances. The radar exaggerates these subtle compositional changes and differences in rock abundance below the dust layer. We are also able to detect lava-like melt flows formed from the heat of the impact.

This image reveals previously dust-hidden features around an area known as Mare Serenitatis, or the Sea of Serenity, which is near the Apollo 17 landing site. The radar observations were able to “see” approximately 33-50 feet below the lunar surface. The light and dark features are the result of compositional changes in the lunar dust and differences in the abundance of rocks buried within the soil. Click to enlarge. (Credit: Bruce Campbell (Smithsonian’s National Air and Space Museum; Arecibo/NAIC; NRAO/AUI/NSF)

Q: A second image shows the Mare Serenitatis (Sea of Tranquility), a feature of the moon that can be seen from earth. What did you find there?

Campbell: Mare Serenitatis was carved out of the moon some 4 billion years ago by a massive asteroid impact. We don’t see impacts like that in our solar system anymore because asteroids of this enormous scale were pretty much depleted from the inner solar system about 3.5 billion years ago. Still, the moon has several dozen large basins carved out by giant impacts like that.

One big finding from our latest image of Mare Serenitatis is a kind of ghostly outline in the middle of the crater that defines two large fields of lava that formed at different times in the moon’s history. When the Mare Serenitatis crater was formed the moon was still warm enough for magma to come close to the surface, and hundreds or thousands of lava flows emerged in the crater’s bottom and began to fill it up. The lava would flow for a period of time, stop, and then another round of eruptions would occur.Over a billion years these layers stacked up between 2 and 3 kilometers deep. The radar exaggerates the differences in the mineral composition between these lava flows and we are able to see some of the later flows quite clearly.

Q: Most of the moon’s craters are very circular in shape as if meteors and asteroids only strike its surface directly from above, and never from an angle. Why is that?

Campbell: Meteorites and asteroids are moving so fast when they hit the moon that the time it takes for one to burrow deep into the moon’s surface (as deep as two or three miles) is actually less than the time it takes for the shockwave to pass through the object and break it up. A shockwave caused by the impact reaches the back of the meteorite after the meteorite is far underground and then it explodes. The meteorite is completely fragmented in the explosion, and most of it is distributed out over the crater. So, it is almost like you detonated something underground. This is why most of the moon’s craters look so circular; only a few meteorites arrive at a large enough angle to make an oblong crater.  

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New data from NASA’s Chandra X-ray Observatory offer a glimpse into the environment of a star before it exploded earlier this year, and insight into what triggered one of the closest supernovas witnessed in decades.

Chandra data is being used to help determine what caused SN 2014J to explode. Astronomers first spotted SN 2014J in the M82 galaxy on January 21, 2014, making it one of the closest supernovas discovered in decades. SN 2014J is a Type Ia supernova, an important class of objects used to measure the expansion of the Universe. The non-detection of X-rays from Chandra gives information about the environment around the star before SN 2014J exploded.
(Image by NASA/CXC/SAO/R.Margutti et al)

The data gathered on the Jan. 21 explosion, a Type Ia supernova, allowed scientists to rule out one possible cause. These supernovas may be triggered when a white dwarf takes on too much mass from its companion star, immersing it in a cloud of gas that produces a significant source of X-rays after the explosion.

Astronomers used NASA’s Swift and Chandra telescopes to search the nearby Messier 82 galaxy, the location of the explosion, for such an X-ray source. However, no source was found, revealing the region around the site of the supernova is relatively devoid of material.

“While it may sound a bit odd, we actually learned a great deal about this supernova by detecting absolutely nothing,” said Raffaella Margutti of the Harvard-Smithsonian Center for Astrophysics (CfA) in Cambridge, Massachusetts, who led the study. “Now we can essentially rule out that the explosion was caused by a white dwarf continuously pulling material from a companion star.”

This supernova, SN 2014J, could instead have been caused by the merger of two white dwarf stars, an event that should result in little or no X-rays after the explosion. Further observations could rule out or confirm other possible triggers.

“Being able to eliminate one of the main possible explanations for what caused SN 2014J to explode is a big step,” said CfA’s Atish Kamble, a co-author of the study. “The next step is to narrow things down even further.”

Type Ia supernovas are used as cosmic distance-markers, and have played a key role in the discovery of the universe’s accelerated expansion. At about 12 million light-years from Earth, SN 2014J and its host galaxy are close — from a cosmic perspective. This offers scientists a chance to observe details that would be too hard to detect in more distant supernovas.

“It’s crucial that we understand exactly how these stars explode because so much is riding on our observations of them for cosmology,” said co-author Jerod Parrent also from CfA. “SN 2014J might be a chance of a lifetime to study one of these supernovas in detail as it happens.”

The study of SN 2014J is similar to a study led by Margutti about another supernova, SN 2011fe, in the nearby galaxy M101.

This study was conducted by CfA’s Supernova Forensics Team, led by Alicia Soderberg. The results were published online and in the July 20 print issue of The Astrophysical Journal.

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Over the vast, empty reaches of interstellar space, countless small molecules tumble quietly though the cold vacuum. Forged in the fusion furnaces of ancient stars and ejected into space when those stars exploded, these lonely molecules account for a significant amount of all the carbon, hydrogen, silicon and other atoms in the universe. In fact, some 20 percent of all the carbon in the universe is thought to exist as some form of interstellar molecule.

This graph shows absorption wavelength as a function of the number of carbon atoms in the silicon-terminated carbon chains SiC_(2n+1)H, for the extremely strong pi-pi electronic transitions. When the chain contains 13 or more carbon atoms – not significantly longer than carbon chains already known to exist in space – these strong transitions overlap with the spectral region occupied by the elusive diffuse interstellar bands. (Image by D. Kokkin, ASU)

Many astronomers hypothesize that these interstellar molecules are also responsible for an observed phenomenon on Earth known as the “diffuse interstellar bands,” spectrographic proof that something out there in the universe is absorbing certain distinct colors of light from stars before it reaches the Earth. But since we don’t know the exact chemical composition and atomic arrangements of these mysterious molecules, it remains unproven whether they are, in fact, responsible for the diffuse interstellar bands.

Now in a paper appearing in The Journal of Chemical Physics a group of scientists led by researchers at the Harvard-Smithsonian Center for Astrophysics in Cambridge, Mass. has offered a tantalizing new possibility: these mysterious molecules may be silicon-capped hydrocarbons like SiC3H, SiC4H and SiC5H, and they present data and theoretical arguments to back that hypothesis.

At the same time, the group cautions that history has shown that while many possibilities have been proposed as the source of diffuse interstellar bands, none has been proven definitively.

“There have been a number of explanations over the years, and they cover the gamut,” says Michael McCarthy a senior physicist at the Harvard-Smithsonian Center for Astrophysics who led the study.

Molecules in space and how we know they are there

Over the vast, empty reaches of interstellar space, countless small molecules tumble quietly though the cold vacuum. Forged in the fusion furnaces of ancient stars and ejected into space when those stars exploded, these lonely molecules account for a significant amount of all the carbon, hydrogen, silicon and other atoms in the universe. Now a group of scientists led by researchers at the Harvard-Smithsonian Center for Astrophysics suggest these mysterious molecules may be silicon-capped hydrocarbons like SiC3H, SiC4H and SiC5H, and they present data and theoretical arguments to back that hypothesis.

Astronomers have long known that interstellar molecules containing carbon atoms exist and that by their nature they will absorb light shining on them from stars and other luminous bodies. Because of this, a number of scientists have previously proposed that some type of interstellar molecules are the source of diffuse interstellar bands — the hundreds of dark absorption lines seen in color spectrograms taken from Earth.

In showing nothing, these dark bands reveal everything. The missing colors correspond to photons of given wavelengths that were absorbed as they travelled through the vast reaches of space before reaching us. More than that, if these photons were filtered by falling on space-based molecules, the wavelengths reveal the exact energies it took to excite the electronic structures of those absorbing molecules in a defined way.

Armed with that information, scientists here on Earth should be able to use spectroscopy to identify those interstellar molecules — by demonstrating which molecules in the laboratory have the same absorptive “fingerprints.” But despite decades of effort, the identity of the molecules that account for the diffuse interstellar bands remains a mystery. Nobody has been able to reproduce the exact same absorption spectra in laboratories here on Earth.

“Not a single one has been definitively assigned to a specific molecule,” said Neil Reilly, a former postdoctoral fellow at Harvard-Smithsonian Center for Astrophysics and a co-author of the new paper.

Now Reilly, McCarthy and their colleagues are pointing to an unusual set of molecules — silicon-terminated carbon chain radicals — as a possible source of these mysterious bands.

As they report in their new paper, the team first created silicon-containing carbon chains SiC3H, SiC4H and SiC5H in the laboratory using a jet-cooled silane-acetylene discharge. They then analyzed their spectra and carried out theoretical calculations to predict that longer chains in this family might account for some portion of the diffuse interstellar bands.

However, McCarthy cautioned that the work has not yet revealed the smoking gun source of the diffuse interstellar bands. In order to prove that these larger silicon capped hydrocarbon molecules are such a source, more work needs to be done in the laboratory to define the exact types of transitions these molecules undergo, and these would have to be directly related to astronomical observations. But the study provides a tantalizing possibility for finding the elusive source of some of the mystery absorption bands — and it reveals more of the rich molecular diversity of space.

“The interstellar medium is a fascinating environment,” McCarthy said. “Many of the things that are quite abundant there are really unknown on Earth.”–by Jason S. Bardi, American Institute of Physics

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