Posted on by Evan Gough

Book Review: The Life and Death of Stars

“The Life and Death of Stars” is a thorough and richly detailed book that will tell you all you want to know about stars. The author, Kenneth R. Lang, is Professor of Astronomy at Tufts University, and he clearly has the knowledge and explanatory ability of someone who has spent his life studying stars. Though its density may deter the casual reader, I found this book engrossing from beginning to end.

If you’ve just been recently bitten by the astronomy bug, this book may not be for you. A more introductory book might be a better choice. But if you’re craving a deeper and more comprehensive understanding of stars, this book will deliver. Make no mistake though; for most readers, it will require some commitment to read your way through this book.

I was never an astrophysics student, but this book seems to me to have a textbook like thoroughness, though not in a dry way. The chapters and topics flow along logically and clearly, with the help of numerous charts and illustrations. For instance, the book starts off with a thorough explanation of light. Since almost all that we know about stars we’ve learned by observing light, where else should a book on astrophysics begin?

From there, the book moves on to chapters titled “Transmutation of the Elements,” “New Stars Arise from the Darkness,” and “Stellar End States,” with other stops in between. The final chapter is titled “Birth, Life, and Death of the Universe.” At the very end of the book, Lang discusses the possible endings of the Universe, and how the mystery of Dark Matter and Dark Energy may dictate the end.

My own understanding of the behaviour and lifecycle of stars has grown enormously from reading this book, and yours will too. For example, if you know that stars form when interstellar gas clouds collapse from their own gravity, but don’t understand exactly how, then “The Life and Death of Stars” will tell you all the detail you’ll need to know. If you know that heavier elements are formed via nucleosynthesis, in the hearts of stars, but you don’t grasp the finer details of that process, then the explanation in this book will bring it to life for you.

Lang is not a populariser of astronomy. His strength is in detailed descriptions, delivered in a comprehensible way. However, he’s not opposed to the occasional poetic turn of phrase: “All stars are impermanent beacons that eventually will cease to shine, vanishing like a circle of fire turning to ash.” True that. He also quotes the Bhagavad Gita, and the poet Shelley.

One of the ways I gauge a book is by my own level of excitement and interest as I’m reading it. I also judge a book by its clarity of explanation and its flow. In both these respects, Lang delivers with this book. After reading it, I’ll definitely be checking out his other books.

“The Life and Death of Stars” broadened and deepened my understanding of all things stellar. It’s a fantastic book, and I wholeheartedly recommend it to Universe Today readers who wish to expand their knowledge of astrophysics.

Posted on by Bob King

Earth is the Most Exotic Place In The Universe

While no elements have been found in space that aren't also present on Earth, there are chemical compounds that are unique to other planets, meteorites and found in the space between the stars. Credit: NASA

I’m often asked by students in my community education astronomy classes whether any new elements have been found in outer space unknown on Earth. The answer to the question is no – nature uses the same 98 natural elements to fashion everything from the familiar stars and planets to those in the farthest galaxies we can see. Outside of an occasional compound or mineral, Earth is the place where you’ll find more exotic elements than anywhere else in the universe.

An element is a pure substance made of just one type of atom. What sets one element apart from another is the number of protons in the nuclei of its atoms. Any atom with six protons will always be carbon, 79 protons gold, 94 protons plutonium and 1 proton hydrogen. The proton number is also the element’s atomic number on the periodic table of elements. Elements in the table are arranged according to their atomic number.

Atoms are made of protons, neutrons and orbiting electrons. The number of protons in atom's nucleus makes it unique from all the others. Hydrogen, the simplest element, has one while carbon has six.
Atoms are made of protons, neutrons and orbiting electrons. The number of protons in atom’s nucleus makes it unique from all the others. Hydrogen, the simplest element, has one; carbon has six.

The two most common elements are hydrogen and helium, numbers 1 and 2 in the periodic table; together they make up 98% of all the visible matter in the universe. The remaining 2% includes everything else from lightweight lithium (number 3) all the way up to californium (98), the heaviest natural element found on Earth and in the stars. Californium is unstable and “decays” into simpler elements. Although scientists make it in the lab by bombarding berkelium (97) with neutrons, trace amounts of this very rare element are found naturally in rich uranium deposits.

When I was in high school studying chemistry, the periodic table of elements ended at Lawrencium (103). At present there are 118 elements, the most recent one created in the lab being ununoctium (you-nah-NOC-tee-um). Matter of fact, all the elements beyond 98 are artificial, brought to life in nuclear reactors or in particle accelerator experiments. They live very short lives. With so many positively-charged protons pushing against one another in their nuclei, these elements quickly break apart into simpler ones in a process called radioactive decay.

Artist's concept of the first stars in the Universe turning on some 200 million years after the Big Bang. These first suns were made of almost pure hydrogen and helium. They and later generations of stars cooked up the heavier elements from these simple ones. Credit: NASA/WMAP Science Team
Artist’s concept of the first stars in the Universe turning on some 200 million years after the Big Bang. These first suns were made of almost pure hydrogen and helium. They and later generations cooked up heavier elements that were later incorporated into the sun and us. Credit: NASA/WMAP Science Team

Back at the time of the Big Bang, when the universe sprang into existence, only the simplest elements – hydrogen, helium and trace amounts of lithium – were cooked up. You can’t build a planet from such fluffy stuff. It took the first generation of stars, which formed from these basic building blocks, to synthesize more complicated elements like carbon, oxygen, sulfur and the like via nuclear fusion in their cores.

When the stars exploded as supernovae, not only were these brand new elements blasted into space, but the enormous heat and pressure during the blast built even heavier elements like gold, copper, mercury and lead. All became incorporated in a second generation of stars. And a third.

The 2% of star-made elements, which include carbon, oxygen, nitrogen and silicon among others, went to build the planets and later became essential for life. We’re made of highly processed material you and I. The atoms of our beings have been in and out of the cores of several generations of stars. Think about this good and hard and you might just get in touch with your own “inner star”.

Common table salt is formed of tight-fitting atoms of sodium and chlorine. Each elements has its own individual character - one's a flammable metal (sodium), the other a dangerous gas. Put them together and you create a safe, tasty edible. Credit: Wikipedia
Common table salt is formed of tight-fitting atoms of sodium and chlorine. Each elements has its own individual character – one’s a flammable metal (sodium), the other a dangerous gas. Put them together and out comes a safe, tasty seasoning. Credit: Wikipedia

Let’s reframe the question about exotic materials in space not present on Earth. Instead of elements, if we look at compounds, we hit paydirt. A compound is also a pure substance but consists of two or more chemical elements joined together. Familiar compounds include water (two hydrogens joined to one oxygen) and salt (one sodium and one chlorine).

A selection of molecules (chemical compounds) including water found in the Orion Nebula detected by the Herschel Space Telescope. Credit: ESA, HEXOS and the HIFI Consortium E. Bergin
A selection of molecules (chemical compounds) including water found in the Orion Nebula detected by the Herschel Space Telescope. Credit: ESA, HEXOS and the HIFI Consortium E. Bergin

Astronomers have found about 220 compounds or molecules in outer space many of them with siblings on Earth but some alien. We don’t have to look far to find them since a few have been delivered right to our doorstep as rocky packages called meteorites.  Here’s a short list of new minerals that formed within asteroids (where meteorites originate) under conditions very different from those found on Earth:

* Barringerite – a metallic compound made of iron, nickel and phosphorus
* Oldhamite – brown mineral made of calcium, magnesium and sulfur
* Kosmochlor  – green mineral containing calcium, chromium, silicon and oxygen

How about new stuff on planets and comets? Astronomers have discovered compounds in the atmospheres of the giant planets Jupiter, Saturn, Uranus and Neptune like silane (silicon-hydrogen), arsine (arsenic-hydrogen) and phosphine (phosphorus-hydrogen) that don’t exist naturally on Earth. Humans have created all three in the lab and put them to good use in various industries including the manufacture of semi-conductors.

Helium was first discovered in the spectrum of the sun by French astronomer Pierre Janssen in 1868 by observing sunlight through a prism during an eclipse. It was discovered on Earth in 1895. Credit: Bob King
Helium, the gas that floats our balloons, was first discovered in the spectrum of the sun by French astronomer Pierre Janssen in during a solar eclipse in 1868. Scientists finally found it on Earth in 1895. Click to learn the helium story. Credit: Bob King

And then there’s Brownleeite, a manganese silicide found in 2003 in a dust particle shed by comet 26P/Grigg-Skjellerup. Moving beyond the solar system, astronomers see unusual long-chained carbon molecules in space that couldn’t form on Earth because oxygen would tear them apart. Space is their safe haven.

So, Earth is the location in the Universe where you’ll find more exotic elements than anywhere else. Thanks to human activity and the complicated molecules that wound together to form life, Earth’s the most exotic place in the universe.

Posted on by Nancy Atkinson

Astrophoto: Paint the Sky with Clouds

Composite of 300 images of the sky at sunset over Palmerston North, New Zealand. Credit and copyright: Manoj Kesavan.

Here’s a great – and beautiful! – example of what you can do with image stacking. Manoj Kesavan, an avid astrophotographer based at Massey University, New Zealand shot 300 images during 45 minutes at sunset (6:45 pm to 7.30 pm local time) from Palmerston North, New Zealand. “It’s a stack of 300 images, which means virtually putting all 300 photos on top of each other,” Kesavan explained via email. “So the cloud formation, movement and the transformation of sky color from blue to purple to red are captured on one single final image. And the saturation has been pumped up during the post processing.”

Kesavan said he shot this as part of an upcoming timelapse, using a Canon 7D using SIgma 10-20mm at 10mm, iso 100 & f8.

It’s a beautiful result and we look forward to seeing the timelapse! See more of Kesavan’s photography at his Facebook page or Flickr stream.

Want to get your astrophoto featured on Universe Today? Join our Flickr group or send us your images by email (this means you’re giving us permission to post them). Please explain what’s in the picture, when you took it, the equipment you used, etc.

Posted on by Nancy Atkinson

A New Look at the Horsehead Nebula for Hubble’s 23rd Anniversary

A new view of the Horsehead Nebula in infrared. Credit: NASA, ESA, and the Hubble Heritage Team (STScI/AURA).

Here’s the iconic Horsehead Nebula as we’ve not seen it before. As the Hubble team so poetically puts it, the nebula looks “like an apparition rising from whitecaps of interstellar foam.” The new image of the Horsehead was photographed in celebration of the 23rd anniversary of the launch of Hubble aboard the space shuttle Discovery, on April 24, 1990.

Can you believe the Hubble Space Telescope has been in space for 23 years? … and it’s been churning out great images for almost 20 years since it was fixed in space during the first Hubble servicing mission in 1993.

This view shows the nebula in infrared wavelengths. When seen in optical light (see below), it appears dark and shadowy, but is “transparent and ethereal when seen in the infrared, represented here with visible shades. The rich tapestry of the Horsehead Nebula pops out against the backdrop of Milky Way stars and distant galaxies that are easily seen in infrared light,” the Hubble team said.

Gas clouds surrounding the Horsehead have already dissipated, but the tip of the jutting pillar contains a slightly higher density of hydrogen and helium, laced with dust. This casts a shadow that protects material behind it from being photo-evaporated, and a pillar structure forms. Astronomers estimate that the Horsehead formation has about five million years left before it too disintegrates.

The Horsehead Nebula is part of a much larger complex in the constellation Orion. Known collectively as the Orion Molecular Cloud, it also houses other famous objects such as the Great Orion Nebula (M42), the Flame Nebula, and Barnard’s Loop. At about 1,500 light-years away, this complex is one of the nearest and most easily photographed regions in which massive stars are being formed.

Hubble’s pairing of infrared sensitivity and unparalleled resolution offers a tantalizing hint of what the upcoming James Webb Space Telescope, set for launch in 2018, will be able to do.

Here’s a view in optical from Hubble:

The Horsehead Nebula is a cold, dark cloud of gas and dust, silhouetted against the bright nebula IC 434. The bright area at the top left edge is a young star still embedded in its nursery of gas and dust. Image Credit: NASA, NOAO, ESA and The Hubble Heritage Team (STScI/AURA)
The Horsehead Nebula is a cold, dark cloud of gas and dust, silhouetted against the bright nebula IC 434. The bright area at the top left edge is a young star still embedded in its nursery of gas and dust.
Image Credit: NASA, NOAO, ESA and The Hubble Heritage Team (STScI/AURA)

For more details, see the HubbleSite

Posted on by David Dickinson

How Micrometeoroid Impacts Pose a Danger for Today’s Spacewalk

Astronauts perform an EVA outside of the ISS during STS-110. (Credt: NASA).



Video streaming by Ustream

Our very own International Space Station is in the cosmic crosshairs.

As cosmonauts are to begin Extra Vehicular Activity (EVA) this morning to perform routine maintenance, an article reminding us of the hazards of such activity came to us via NASA’s Orbital Debris Quarterly Newsletter.

The problem is Micrometeoroid and Orbital Debris (MMOD) impacts. These are nothing new. Pits and tiny cratering has been observed during post-flight inspections of space shuttle orbiters. But this is the first time we’d seen talk of damage caused by tiny impacts on the exterior of the International Space Station.

The handrails are a particularly sensitive area of concern.

The study examined damage incurred on handrails exposed to the environment of space for years on end. These present a hazard to spacewalking astronauts who rely on the handles to move about. These craters often become spalled, presenting a sharp metal rim raised from the surface of the handle.

Close-up of a micro-meteoroid impact on a handrail. (Credit: NASA/JSC Image & Science Analysis Group).
Close-up of a micro-meteoroid impact on a handrail. (Credit: NASA/JSC Image & Science Analysis Group).

Of course, these razor sharp rims present a problem, especially to space suit gloves. One 34.8 centimeter long handrail returned on the final Space Shuttle mission STS-135 had six impact craters along its length. The handrail had been in service and exposed to the vacuum of space for 8.7 years.

Craters as large as 1.85 millimetres (mm) in diameter with raised lips of 0.33mm have been observed on post-inspection. In studies conducted by NASA engineers, craters with lip heights as little as 0.25mm have been sufficient to snag and tear spacesuit gloves.

There have also been reported incidents of glove tears during EVAs conducted from the ISS over the years. For example, the report cites a tear noticed by astronaut Rick Mastracchio during STS-118 that cut the EVA short.

Analysis of an impact seen on STS-122. (Credit: NASA
Analysis of an impact seen on STS-122. (Credit: NASA/JSC Image & Science Analysis Group).

To protect astronauts and cosmonauts during EVAs, the following measures have been instituted:

–          Toughening space suit gloves by adding reinforcement to areas exposed to potential MMOD damage.

–          Monitoring and analyzing MMOD impacts along handrails and maintaining a database of problem areas.

–          Equipping spacewalkers with the ability to cover and/or repair hazardous MMOD areas during spacewalks.

The studies were carried out by the Johnson Space Center Hypervelocity Impact Technology Group in conjunction with a test facility at White Sands, New Mexico. Astronaut Rick Mastracchio can also be seen talking about the hazards of spacewalking on this video.

Today’s 6 hour EVA by cosmonauts Vinogradov & Romanenko begins at 14:06 UT 10:06AM EDT.

This will be the 32nd Russian EVA from the International Space Station and will use the Pirs hatch on Zvezda.

Tasks include retrieving and installing experiment packages and replacing a defective retro-reflector device on the station’s exterior.  The device is a navigational aid necessary for the Albert Einstein ATV-4 mission headed to the ISS on June 5th.

Progress 51P is also scheduled to launch towards the ISS next week on April 24 for docking on April 26th.

Debris in Low Earth Orbit is becoming an increasing concern. The Chinese anti-satellite test in 2007 and the collision of Kosmos 2251 and Iridium 33 in 2009 have increased hazards to the ISS. Many fear that a tipping point, known as an ablation cascade, could eventually occur with one collision showering LEO with debris that in turn trigger many more. The ISS was only finished in 2011, and it would be a tragic loss to see it abandoned due to a catastrophic collision only years after completion.

More than once, ISS crew members have sat out a debris conjunction that was too close to call in their Soyuz life boats, ready to evacuate the station if necessary. DAMs (Debris Avoidance Maneuvers) are now common for the ISS throughout the year.

Several ideas have been proposed to deal with space debris. In the past year, NanoSail-2D demonstrated the ability to deploy a solar sail from a satellite for reentry at the end of a spacecraft’s life span. Such technology may be standard equipment on future satellites.

Expect reentries to increase as we near the solar maximum for cycle #24 in late 2013 & early 2014. This occurs because the exosphere of Earth “puffs out” due to increased solar activity and increases drag on satellites in low Earth orbit.

All food for thought as we watch today’s EVA… space travel is never routine!

The April 2013 edition of the Orbital Debris Quarterly News is available for free online.

 

Posted on by Nancy Atkinson

Habitable Worlds? New Kepler Planetary Systems in Images

Relative sizes of Kepler habitable zone planets discovered as of 2013 April 18. Left to right: Kepler-22b, Kepler-69c, Kepler-62e, Kepler-62f, and Earth (except for Earth, these are artists' renditions). Credit: NASA/Ames/JPL-Caltech.

The Kepler mission has discovered two new planetary systems that include three super-Earth-size planets in the “habitable zone,” the range of distance from a star where the surface temperature of an orbiting planet might be suitable for liquid water.

The Kepler-62 system has five planets; 62b, 62c, 62d, 62e and 62f. The Kepler-69 system has two planets; 69b and 69c. Kepler-62e, 62f and 69c are the super-Earth-sized planets. (Read all the details in our full article here.)

The new planets brings the number of confirmed exoplanets to 861. According to the Planetary Habitability Laboratory, there are now nine potential habitable worlds outside of our solar system, with 18 more potentally habitable planetary candidates found by Kepler waiting to be confirmed. Additionally, astronomers predict there are 25 potentially habitable exomoons.

Here is some of the imagery (sorry, but they are artists concepts!), graphs and video used in today’s briefing about the new discoveries, as well as some some from the Planetary Habitability Laboratory:

Here’s a flythrough of the Kepler 62 system:

The diagram compares the planets of the inner solar system to Kepler-69, a two-planet system about 2,700 light-years from Earth. Image credit: NASA Ames/JPL-Caltech
The diagram compares the planets of the inner solar system to Kepler-69, a two-planet system about 2,700 light-years from Earth.
Image credit: NASA Ames/JPL-Caltech
Much like our solar system, Kepler-62 is home to two habitable zone worlds. The small shining object seen to the right of Kepler-62f is Kepler-62e. Orbiting on the inner edge of the habitable zone, Kepler-62e is roughly 60 percent larger than Earth. Image credit: NASA Ames/JPL-Caltech.
Much like our solar system, Kepler-62 is home to two habitable zone worlds. The small shining object seen to the right of Kepler-62f is Kepler-62e. Orbiting on the inner edge of the habitable zone, Kepler-62e is roughly 60 percent larger than Earth. Image credit: NASA Ames/JPL-Caltech.
The diagram compares the planets of the inner solar system to Kepler-62, a five-planet system about 1,200 light-years from Earth. Image credit: NASA Ames/JPL-Caltech
The diagram compares the planets of the inner solar system to Kepler-62, a five-planet system about 1,200 light-years from Earth. Image credit: NASA Ames/JPL-Caltech
Current known potentially habitable exoplanets. Credit: Planetary Habitability Laboratory/University of Puerto Rico, Arecibo.
Current known potentially habitable exoplanets. Credit: Planetary Habitability Laboratory/University of Puerto Rico, Arecibo.
Current potentially habitable exoplanets showing the new additions, Kepler-62e and Kepler-62f. Credit: Planetary Habitability Laboratory/University of Puerto Rico, Arecibo.
Current potentially habitable exoplanets showing the new additions, Kepler-62e and Kepler-62f. Credit: Planetary Habitability Laboratory/University of Puerto Rico, Arecibo.
Comparison of the orbit and size of the exoplanets of Kepler-62 with the terrestrial planets of our Solar Systems. The darker green shaded area corresponds to the 'conservative habitable zone' while its lighter borders to its 'optimistic habitable zone' extension. Planet sizes and orbits are not to scale between them. Credit: Planetary Habitability Laboratory/University of Puerto Rico, Arecibo.
Comparison of the orbit and size of the exoplanets of Kepler-62 with the terrestrial planets of our Solar Systems. The darker green shaded area corresponds to the ‘conservative habitable zone’ while its lighter borders to its ‘optimistic habitable zone’ extension. Planet sizes and orbits are not to scale between them. Credit: Planetary Habitability Laboratory/University of Puerto Rico, Arecibo.

Posted on by Tammy Plotner

Bright Blazar’s Emission Defies Explanations

Artist's concept of the Hubble Space Telescope viewing ultraviolet light from the jet of the active galactic nucleus of PKS 1424+240. Clouds of hydrogen gas along the line of sight absorb the light at known frequencies, allowing the redshift and distance of each cloud to be determined. The most distant gas cloud determines the minimum distance to PKS 1424+240. Data from the Fermi Gamma-ray Space Telescope, shown on the horizon at the left, were also used for this study. (Image composition by Nina McCurdy, component images courtesy of NASA)

When it comes to sheer wattage, blazars definitely rule. As the brightest of active galactic nuclei, these sources of extreme high-energy gamma rays are usually associated with relativistic jets of material spewing into space and enabled by matter falling into a host galaxy’s black hole. The further away they are, the dimmer they should be, right? Not necessarily. According to new observations of blazar PKS 1424+240, the emission spectrum might hold a new twist… one that can’t be readily explained.

David Williams, adjunct professor of physics at UC Santa Cruz, said the findings may indicate something new about the emission mechanisms of blazars, the extragalactic background light, or the propagation of gamma-ray photons over long distances. “There may be something going on in the emission mechanisms of the blazar that we don’t understand,” Williams said. “There are more exotic explanations as well, but it may be premature to speculate at this point.”

The Fermi Gamma-ray Space Telescope was the first instrument to detect gamma rays from PKS 1424+240, and the observation was then seconded by VERITAS (Very Energetic Radiation Imaging Telescope Array System) – a terrestrially based tool designed to be sensitive to gamma-rays in the very high-energy (VHE) band. However, these weren’t the only science gadgets in action. To help determine the redshift of the blazar, researchers also employed the Hubble Space Telescope’s Cosmic Origins Spectrograph.

To help understand what they were seeing, the team then set a lower limit for the blazar’s redshift, taking it to a distance of at least 7.4 billion light-years. If their guess is correct, such a huge distance would mean that the majority of the gamma rays should have been absorbed by the extragalactic background light, but again the answers didn’t add up. For that amount of absorption, the blazar itself would be creating a very unexpected emission spectrum.

“We’re seeing an extraordinarily bright source which does not display the characteristic emission expected from a very high-energy blazar,” said Amy Furniss, a graduate student at the Santa Cruz Institute for Particle Physics (SCIPP) at UCSC and first author of a paper describing the new findings.

Bright? You bet. In this circumstance it has to over-ride the ever-present extragalactic background light (EBL). The whole Universe is filled with this “stellar light pollution”. We know it’s there – produced by countless stars and galaxies – but it’s just hard to measure. What we do know is that when a high-energy gamma ray photo meets with a low-energy EBL photon, they essentially cancel each other out. It stands to reason that the further a gamma ray has to travel, the more likely it is to encounter the EBL, putting a limit on the distance to which we can detect high-energy gamma ray sources. By lowering the limit, the new model was then used to ” calculate the expected absorption of very high-energy gamma rays from PKS 1424+240″. This should have allowed Furniss’ team to gather an intrinsic gamma-ray emission spectrum for the most distant blazar yet captured – but all it did was confuse the issue. It just doesn’t coincide with expected emissions using current models.

“We’re finding very high-energy gamma-ray sources at greater distances than we thought we might, and in doing so we’re finding some things we don’t entirely understand,” Williams said. “Having a source at this distance will allow us to better understand how much background absorption there is and test the cosmological models that predict the extragalactic background light.”

Original Story Source: University of California Santa Cruz News Release. For further reading: The Firm Redshift Lower Limit of the Most Distant TeV-Detected Blazar PKS 1424+240.

Posted on by Nancy Atkinson

Kepler Team Finds System with Two Potentially Habitable Planets

The newly discovered planets named Kepler-62e and -f are super-Earths in the habitable zone of a distant sun-like star. The largest planet in the image, Kepler-62f, is farthest from its star and covered by ice. Kepler-62e, in the foreground, is nearer to its star and covered by dense clouds. Closer in orbits a Neptune-size ice giant with another small planet transiting its star. Both habitable-zone planets may be capable of supporting life. Credit: David A. Aguilar (CfA)

This might be the most exciting exoplanet news yet. An international team of scientists analyzing data from NASA’s Kepler mission has found a planetary system with two small, potentially rocky planets that lie within the habitable zone of their star. The star, Kepler-62, is a bit smaller and cooler than our Sun, and is home to a five-planet system. Two of the worlds, Kepler-62e and Kepler-62f are the smallest exoplanets yet found in a habitable zone, and they might both be covered in water or ice, depending on what kind of atmosphere they might have.

“Imagine looking through a telescope to see another world with life just a few million miles from your own. Or, having the capability to travel between them on a regular basis. I can’t think of a more powerful motivation to become a space-faring society,” said Harvard astronomer Dimitar Sasselov, who is co-author of a new paper describing the discovery.

Masses and sizes for selected planets. The curves show the mass-radius-relation (average density) for different types of planets: The blue line indicates the loci of planets made mostly (75%) of water, the black line that of planets like our Earth that consist almost exclusively of rock (represented here by the mineral Enstatite, MgSiO3, a member of the pyroxite silicate mineral series that makes up most of the Earth's mantle), and so on. The measured radii of Kepler-62e and Kepler-62f plus an estimate of their mass places them in a region (blue areas) where it is highly probable for them to be earth-like planets, that is: planets with a solid (if possibly covered in water) surface. Kepler-11f, on the other hand, is a Mini-Neptune, showing clearly that a comparatively low mass does not necessarily make for a solid planet. Image: L. Kaltenegger (MPIA)
Masses and sizes for selected planets. The curves show the mass-radius-relation (average density) for different types of planets: The blue line indicates the loci of planets made mostly (75%) of water, the black line that of planets like our Earth that consist almost exclusively of rock (represented here by the mineral Enstatite, MgSiO3, a member of the pyroxite silicate mineral series that makes up most of the Earth’s mantle), and so on. The measured radii of Kepler-62e and Kepler-62f plus an estimate of their mass places them in a region (blue areas) where it is highly probable for them to be earth-like planets, that is: planets with a solid (if possibly covered in water) surface. Kepler-11f, on the other hand, is a Mini-Neptune, showing clearly that a comparatively low mass does not necessarily make for a solid planet. Image: L. Kaltenegger (MPIA)

Kepler-62 in the constellation Lyra, and is about 1,200 light-years from Earth.

62e is 1.61 times Earth’s size, circles the star in 122.4 (Earth) days. 62f is 1.4 times the size of Earth, and orbits its star in 267.3 days. Previously, the smallest planet with known radius inside a habitable zone was Kepler-22b, with a radius of 2.4 times that of the Earth.

A third planet in another star system was also announced at a press briefing today. Kepler-69c is 70 percent larger than the size of Earth, and orbits in the habitable zone of a star similar to our Sun. Researchers are uncertain about the composition of Kepler-69c, but astronomer Thomas Barclay from the BAER Institute said its closer orbit of 242 days around a Sun-like star means it is likely more like a super-Venus rather than a super-Earth.

The habitable zone (in which liquid water on a planet's surface can exist) for different types of stars. The inner planets of our Solar System are shown on top, with Earth and Mars in the habitable zone. Kepler-62 is a notably cooler star, and Kepler-62e and -62f are in its habitable zone. For Kepler-69c, another planet announced today by NASA, the error bars for the star's radiation are such that it could possibly in the habitable zone as well. Kepler-22b, the smallest planet found in a habitable zone before the recent discoveries, is very likely a Mini-Neptune, and not a solid planet. In what is denoted the empirical habitable zone, liquid water can exist on the surface of a planet if that planet has sufficient cloud cover. In the narrow habitable zone, liquid water can exist on the surface even without the presence of a cloud cover. Image: L. Kaltenegger (MPIA)
The habitable zone (in which liquid water on a planet’s surface can exist) for different types of stars. The inner planets of our Solar System are shown on top, with Earth and Mars in the habitable zone. Kepler-62 is a notably cooler star, and Kepler-62e and -62f are in its habitable zone. For Kepler-69c, another planet announced today by NASA, the error bars for the star’s radiation are such that it could possibly in the habitable zone as well. Kepler-22b, the smallest planet found in a habitable zone before the recent discoveries, is very likely a Mini-Neptune, and not a solid planet. In what is denoted the empirical habitable zone, liquid water can exist on the surface of a planet if that planet has sufficient cloud cover. In the narrow habitable zone, liquid water can exist on the surface even without the presence of a cloud cover. Image: L. Kaltenegger (MPIA)

The team says that while the sizes of Kepler 62e and 62f are known, their mass and densities are not. However, every planet found in their size range so far has been rocky, like Earth.

Kepler-62 system. Five planets, two of which are in the Habitable Zone. Credit: NASA
Kepler-62 system. Five planets, two of which are in the Habitable Zone. Credit: NASA

“These planets are unlike anything in our solar system. They have endless oceans,” said lead author Lisa Kaltenegger of the Max Planck Institute for Astronomy and the Harvard Smithsonian Center for Astrophysics. “There may be life there, but could it be technology-based like ours? Life on these worlds would be under water with no easy access to metals, to electricity, or fire for metallurgy. Nonetheless, these worlds will still be beautiful blue planets circling an orange star — and maybe life’s inventiveness to get to a technology stage will surprise us.”

As the warmer of the two worlds, Kepler-62e would have a bit more clouds than Earth according to computer models. More distant Kepler-62f would need the greenhouse effect from plenty of carbon dioxide to warm it enough to host an ocean. Otherwise, it might become an ice-covered snowball.

“Kepler-62e probably has a very cloudy sky and is warm and humid all the way to the polar regions. Kepler-62f would be cooler, but still potentially life-friendly,” said Harvard astronomer and co-author Dimitar Sasselov. “The good news is — the two would exhibit distinctly different colors and make our search for signatures of life easier on such planets in the near future. “

The Kepler spacecraft is able to detect planets that transit or cross the face of their host star. Measuring a transit tells astronomers the size of the planet relative to its star.

“All of the other interesting planets in the habitable zone were until now discovered by what is known as the radial velocity method,” said Kaltenegger. “This method gives you a lower limit for the planet’s mass, but no information about its radius. This makes it difficult to assess whether or not a planet is rocky, like the Earth. A small radius (less than 2 Earth radii), on the other hand, is a strong indicator that a planet around is indeed rocky – unless we are talking about a planet around a very young star.”

“What makes Kepler-62e and Kepler-62f so exciting is a combination of two factors,” Kaltenegger added. “We know their radius, which indicates that these are indeed rocky planets, and they orbit their star in the habitable zone. That makes them our best candidates for habitable planets out there yet.

Kaltenegger provides more details on these exoplanets in this video:

Sources: Max Planck Institute for Astronomy, CfA

Posted on by Dan Majaess

Astronomers Hint that our Sun won’t Terminate as the Typical Planetary Nebula

An artist's illustration of a planetary nebula engulfing its orbiting planets (image credit: Regulus36/deviantart, adjusted by DM to mitigate compression effects).

Textbooks often cite that planetary nebulae (PNe, plural) represent an endstate for lower-mass single stars. But conversely, recent research suggests that most PNe stem from binary systems. The lowest mass star theorized to form the typical PN is near 1 solar mass, and thus without a companion the Sun may not surpass the mass limit required to generate the hot glowing (ionized) nebula typically tied to PNe.  New research continues to question our original understanding of how the Sun’s life may end.

A new study spearheaded by G. Jacoby aimed in part to test that binary hypothesis by searching for PNe in star clusters occupying M31.  The team remarked that, “while the binary interaction model explains some of the anomalies associated with the observed planetary nebula population, this theory awaits final confirmation.”

“The traditional theory states that the progenitors of PNe are low- to intermediate-mass single stars … However, this theory does not provide a natural explanation for the non-spherical morphologies observed for the great majority of PNe, nor their low rate of formation. For these and other inconsistencies, a new paradigm has been developed, wherein most PNe are shaped via the interaction … with a binary companion,” said Jacoby et al. 2013.
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