The month of August is upon us once again, bringing with it humid days and sultry nights for North American observers.
You’ll often hear the first few weeks of August referred to as the Dog Days of Summer. Certainly, the oppressive midday heat may make you feel like lounging around in the shade like our canine companions. But did you know there is an astronomical tie-in for the Dog Days as well?
We’ve written extensively about the Dog Days of Summer previously, and how the 1460 year long Sothic Cycle of the ancient Egyptians became attributed to the Greek adoption of Sothis, and later in medieval times to the ‘Dog Star’ Sirius. Like the Blue Moon, say something wrong enough, long enough, and it successfully sticks and enters into meme-bank of popular culture.
Sirius (to the lower right) along with The Moon, Venus and Mercury and a forest fire taken on July 22, 2014. (Note- this was shot from the Coral Towers Observatory in the southern hemisphere). Image credit and copyright: Joseph Brimacombe
A water monopoly empire, the Egyptians livelihood rested on knowing when the annual flooding of the Nile was about to occur. To this end, they relied on the first seasonal spotting of Sirius at dawn. Sirius is the brightest star in the sky, and you can just pick out the flicker of Sirius in early August low to the southeast if you know exactly where to look for it.
Sundown over Cairo during the annual flooding of the Nile river. Image Credit: Travels through the Crimea, Turkey and Egypt 1825-28 (Public Domain).
Sirius lies at a declination of just under 17 degrees south of the celestial equator. It’s interesting to note that in modern times, the annual flooding of the Nile (prior to the completion of the Aswan Dam in 1970) is commemorated as occurring right around August 15th. Why the discrepancy? Part of it is due to the 26,000 year wobbling of the Earth’s axis known as the Precession of the Equinoxes; also, the Sothic calendar had no intercalculary or embolismic (think leap days) to keep a Sothic year in sync with the sidereal year. The Sothic cycle from one average first sighting of Sirius to another is 365.25 days, and just 9 minutes and 8 seconds short of a sidereal year.
The Djoser step pyramid outside of Cairo. Image credit: Dave Dickinson
But that does add up over time. German historian Eduard Meyer first described the Sothic Cycle in 1904, and tablets mention its use as a calendar back to 2781 BC. And just over 3 Sothic periods later (note that 1460= 365.25 x 4, which is the number of Julian years equal to 1461 Sothic years, as the two cycles ‘sync up’), and the flooding of the Nile now no longer quite coincides with the first sighting of Sirius.
Such a simultaneous sighting with the sunrise is known in astronomy as a heliacal rising. Remember that atmospheric extinction plays a role sighting Sirius in the swampy air mass of the atmosphere low to the horizon, taking its usual brilliant luster of magnitude -1.46 down to a more than a full magnitude and diminishing its intensity over 2.5 times.
This year, we transposed the seasonal predicted ‘first sightings’ of Sirius versus latitude onto a map of North America:
Optimal sighting dates for the heliacal rising of Sirius by latitude. Image credit: Dave Dickinson, adapted from data by Ed Kotapish.
Another factor that has skewed the date of first ‘Sirius-sign’ is the apparent motion of the star itself. At 8.6 light years distant, Sirius appears to move 1.3 arc seconds per year. That’s not much, but over the span of one Sothic cycle, that amounts up to 31.6’, just larger than the average diameter of a Full Moon.
Sirius has been the star of legends and lore as well, not the least of which is the curious case of the Dogon people of Mali and their supposed privileged knowledge of its white dwarf companion star. Alvan Graham Clark and his father discovered Sirius B in 1862 as they tested out their shiny new 18.5-inch refractor. And speaking of Sirius B, keep a telescopic eye on the Dog Star, as the best chances to spy Sirius B peeking out from the glare of its primary are coming right up around 2020.
The dazzling visage of Sirius. Image credit: Dave Dickinson
Repeating the visual feat of spying Sirius B low in the dawn can give you an appreciation as to the astronomical skill of ancient cultures. They not only realized the first sighting of Sirius in the dawn skies coincided with the annual Nile flooding, but they identified the discrepancy between the Sothic and sidereal year, to boot. Not bad, using nothing but naked eye observations. Such ability must have almost seemed magical to the ancients, as if the stars had laid out a celestial edge for the Egyptians to exploit.
Man’s best (observing) friend… Image credit: Dave Dickinson
You can also exploit one method of teasing out Sirius from the dawn sky a bit early that wasn’t available to those Egyptian astronomer priests: using a pair of binoculars to sweep the skies. Can you nab Sirius with a telescope and track it up into the daytime skies? Sirius is just bright enough to see in the daytime against a clear blue sky with good transparency if you know exactly where to look for it.
Stephen Hawking, Frank Drake and dozens of journalists gathered at the Royal Society in London last week to hear astronomers announce a ground-breaking new project to search for intelligent extraterrestrial life called “Breakthrough Listen.” They will be using two of the world’s largest radio telescopes (Green Bank Telescope in West Virginia and the Parkes Radio Telescope in Australia) to listen for radio messages from intelligent alien species. Scientists have chosen to target the nearest million stars as well as the nearest 100 galaxies. This project will also monitor the Galactic plane for months at a time. This unprecedented effort is a collaboration between UC Berkeley and the Breakthrough Prize Foundation, and employs an international team of astronomers and data scientists, including Frank Drake – the father of SETI (Search for ExtraTerrestrial Intelligence).
It is perhaps fitting that this new program will make use of the Green Bank Telescope (GBT), since Green Bank, West Virginia was the site of the first modern SETI experiment, called “Project Ozma.” In 1960, Frank Drake pointed the Tatel telescope at two nearby stars to search for the telltale signs of intelligent life; radio signals near 1.420 GHz. He listened on-and-off for four months, collecting 150 hours of data. He heard nothing.
In 1963, astronomers began the first ever continuous monitoring program using the Ohio State University Radio Observatory. Called the “Big Ear,” this observatory was used to monitor the sky continuously for 22 years. They heard nothing. The “Big Ear” was dismantled in 1998 to make room for the expansion of a nearby golf course.
In 2009, UC Berkeley launched the latest incarnation of the Search for Extra-Terrestrial Radio Emissions from Nearby Developed Intelligent Populations (SERENDIP), which employs the Arecibo telescope in Puerto Rico. The idea is to effectively “piggy-back” on other planned radio observations and to use the same data that other astronomers are taking to study galaxies, but search those radio channels to find messages from ET.
The new program will be “a factor of 100 times more powerful than any current or past SETI program” says astronomer Geoff Marcy, a leading member of the team that will be organizing this search. He goes on to say that the 1.5 GHz bandwidth used for this program will be “like tuning your radio in your car, but instead of collecting the music from just one station, you collect the transmission from 1.5 billion stations.”
Finding funding for SETI projects has been a challenge ever since NASA pulled their support in 1993. Scientists have relied on large private donations for years. Between 2000 and 2007, SETI pulled in nearly $49 million to build the Allen Telescope Array in northern California. Such donations have been sufficient to support some of the smaller projects, but there hasn’t been a new, big-budget SETI endeavor in years. Many scientists are hopeful that the influx of funding from investor Yuri Milner for this program is only the beginning. Jill Tarter, former director of the Center for SETI Research and currently holding the Bernard M. Oliver Chair for SETI at the SETI Institute believes that the time is right for the public to re-invest in SETI. In the past, astronomers have had an uphill battle convincing investors that the search for “little green men” is a legitimate, scientific endeavor, and worth significant attention. Some investors have even been laughed at for spending money on the search for intelligent alien life. Tarter hopes that the public attitude toward SETI is about to change: “The more people like Yuri openly and generously support this endeavor, the more you remove the possibility for being embarrassed or being ridiculed. The people who have funded [SETI] in the past, like Paul Allen, have been very bold. We need more Paul Allens. We need more Yuri Milners.”
Will we find intelligent life?
The question that everyone wants to know is this: How likely is it that this or any other SETI program will actually find evidence of intelligent alien life, either in our galaxy or another? As it turns out, that is a very difficult question to answer. Remember, this SETI program will be searching for intelligent life in the universe. Even if our galaxy is full of planets teeming with microbes, none of them will be sending out radio signals that we could intercept. What are the odds that another planet hosts an intelligent alien species?
Drake Equation (image credit: Colin A Houghton)
To even begin to answer that question, we have to look at the Drake Equation. This is a simple and elegant equation, first proposed by Frank Drake, to calculate the number of intelligent alien species that should reside in our Milky Way galaxy based on a series of probabilities. While the first few factors of this equation are relatively well-known quantities, we have to make educated guesses about some of them.
Number of Stars Born Each Year – 1.0
By studying the light emitted by young stars, astronomers are able to estimate that about 1 new star is born every year in the Milky Way galaxy, though some estimates have gone as high as 7 new stars per year.
Fraction of Stars with Planets – 0.50
The latest studies using results from the Kepler Space Telescope indicate that nearly 100% of stars like the Sun have at least one planet. Many planetary systems we have observed so far appear to be packed with 3 or more planets! Even the most skeptical analysis of the available data leads us to believe that ~50% of all stars have at least one planet.
Kepler 62 contains multiple planets in the habitable zone of the host star. Image credit: NASA Ames/JPL-Caltech
Number of Habitable Planets per Planetary System – 0.2
This number is also motivated by the most recent Kepler data. It is difficult to assign a value to this parameter, since Sun-like stars have more habitable planets than, say, high-mass stars. However, conservative estimates say that there are 0.2 habitable planets around each star, since 1/5 stars host at least one planet in the habitable zone of its star.
Fraction of Habitable Planets that Actually Develop Life – 1.0
From here on, our estimates are much more sketchy. For instance, how many planets that could host life actually do? We have tried to recreate the conditions of the early Earth in laboratories to try to replicate the development of life on our planet, and have been unsuccessful. We don’t entirely understand how life on Earth actually got its start. Geological evidence suggests that life started immediately after the Late Heavy Bombardment – a period of time when Earth was pummeled by comets and asteroids from the outer Solar System. As soon as it was safe for life to begin, it did.We believe that life may have existed on Mars billions of years ago, but have not found any direct evidence (fossils) yet. Such a discovery would suggest that life is created easily on any planet with the right conditions. Since the only habitable planet in our Solar System did develop life, we could estimate that this number is 100%.
Fraction of Life Systems that Develop Intelligence – 0.50
Recall that the mission of SETI is to discover intelligent life on another planet. Human beings are the only species on our planet that could send and receive radio signals. So, how likely is it that life will evolve to become intelligent? There are some who would argue that intelligence is an inevitable consequence of evolution, but this is a highly debated issue. Since probability that a species will develop intelligence is somewhere between 0-100%, we will say that it is 50%.
Fraction of Intelligent Species that Develop Interstellar Communication -0.10
There are different levels of intelligence, and not all intelligent species will be able to send radio signals across interstellar space. Chimpanzees share much of their DNA with humans, but they have not built their own space program. So we need to examine the fraction of intelligent species that will actually develop the ability to communicate with us across space. We might assume that any intelligent species would eventually seek out fellow residents of the Milky Way in an attempt to share knowledge. Conservatively, we might estimate that 10% of intelligent species will develop interstellar communication.
Broadcasting Lifetime
Of course, it is not useful for us if there was an intelligent, broadcasting alien species in our Milky Way 2 billions years ago that has since died off. We want to communicate with ET here and now. Therefore, we have to take into consideration the length of time during which a civilization can broadcast signals into space. Our galaxy is only 10 billion years old, so even if life began on a planet at the moment our galaxy was formed, it could only have been broadcasting for 10 billion years. The first intentional broadcast from Earthlings into space with the intention of reaching alien species was in 1974 from the Arecibo Radio Telescope in Puerto Rico. Let’s assume (conservatively) that intelligent species are able to broadcast radio signals for 10,000 years.
When we plug these numbers into the Drake Equation, we find that there should be about 100 intelligent alien species currently capable of communicating with Earth in our Milky Way galaxy alone. Since there are approximately 150 billion galaxies in the visible universe alone, that means that there should be 15,000,000,000,000 intelligent alien species in our universe.
But what if these numbers are wrong? What if there’s no one out there? When do we pull the plug and stop spending money on a program that hasn’t had any success? Jill Tarter says that the most important results from SETI have nothing to do with extraterrestrial intelligence, but everything to do with our cosmic perspective. “SETI being discussed….SETI being pursued around the globe has this phenomenal ability to make us stop in our day-to-day lives and look at the big picture. And that picture is the ‘Pale Blue Dot.’ That’s us. We’re all the same to someone ‘out there’.” she said in an interview with Universe Today. She went on to explain that the most precious short-term benefit of SETI is the perspective it gives us, which can help us as a species to solve big problems here on Earth. “The ability to trivialize the differences among human beings is something that is incredibly important, because it will help us when we step up and try to solve the challenges we have in our future and when we try to manage our planet as a global civilization.”
With the new SETI initiative, astronomers are betting that there is someone out there, trying to communicate with us right now, and all we have to do is listen. As astronomer Geoff Marcy put it, “Every explorer has ventured out. They have crossed a river…or gone over a hill, not knowing what they would find. The most exquisite and fantastic types of exploration are journeys where you don’t know what you’re going to find. SETI is like that. We don’t know if we will find anything. But we are explorers, crossing a cosmic ocean, and these two radio telescopes are our ocean liner.”
This image contains the initial, informal names being used by the New Horizons team for the features on Pluto’s largest moon, Charon. Names were selected based on the input the team received from the Our Pluto naming campaign. Names have not yet been approved by the International Astronomical Union (IAU). Click for a pdf. Credit: NASA/Johns Hopkins University Applied Physics Laboratory/Southwest Research Institute
A big smile. That was my reaction to seeing the names of Uhura, Spock, Kirk and Sulu on the latest map of Pluto’s jumbo moon Charon. The monikers are still only informal, but new maps of Charon and Pluto submitted to the IAU for approval feature some of our favorite real life and sci-fi characters. Come on — Vader Crater? How cool is that?
This image contains the initial, informal names being used by the New Horizons team for the features and regions on the surface of Pluto. The IAU will still need to give final approval. Click for a large pdf file. Credit: NASA/Johns Hopkins University Applied Physics Laboratory/Southwest Research Institute
Pluto’s features, in contrast, are named for both real people and places as well as mythological beings of underworld mythology. Clyde Tombaugh, the dwarf world’s discoverer, takes center stage, with his name appropriately spanning 990 miles (1,590 km) of frozen terrain nicknamed the “heart of Pluto”. Perhaps the most intriguing region of Pluto, it’s home to what appear to be glaciers of nitrogen ice still mobile at temperatures around –390°F (–234°C).
A close-up slice of Plutonian landscape centered on Tombaugh Regio with informal names waiting for approval. Click for a large pdf file. Credit: NASA/Johns Hopkins University Applied Physics Laboratory/Southwest Research Institute
Pluto, being a physically, historically and emotionally bigger deal than Charon, comes with six themes. I’ve listed a few examples for each:
* Space Missions and Spacecraft – Sputnik, Voyager, Challenger
* Scientists and Engineers– Tombaugh, Lowell, Burney (after Venetia Burney, the young girl who named Pluto) * Historic Explorers– Norgay, Cousteau, Isabella Bird
* Underworld Beings– Cthulu, Balrog (from Lord of the Rings), Anubis (Egyptian god associated with the afterlife)
* Underworlds and Underworld Locales– Tartarus (Greek “pit of lost souls”), Xibalba (Mayan underworld), Pandemonium (capital of hell in Paradise Lost)
* Travelers to the Underworld– Virgil (tour guide in Dante’s Divine Comedy), Sun Wukong (Monkey king of Chinese mythology), Inanna (ancient Sumerian goddess)
Global map of Pluto’s moon Charon pieced together from images taken at different resolutions. Credit: NASA/Johns Hopkins University Applied Physics Laboratory/Southwest Research Institute
There’s nothing like a name. Not only do names make sure we’re all talking about the same thing, but they’re how we begin to understand the unique landscapes presented to us by Pluto and its wonderful system of satellites. To keep them all straight, astronomers at the International Astronomical Union’s Working Group on Planetary System Nomemclature are charged with choosing themes for each planet, asteroid or moon along with individual names for craters, canyons, mountains, volcanoes based on those themes. Astronomers help the group by providing suggested themes and names. In the case of the Pluto system, the public joined in to help the astronomers by participating in the Our Pluto Naming Campaign.
Craters and fissures (fossae) on Charon photographed during the flyby. Credit: NASA/Johns Hopkins University Applied Physics Laboratory/Southwest Research Institute
If you’ve followed naming conventions over the years, you’ve noticed more Latin in use, especially when it comes to basic land forms. I took Latin in college and loved it, but since few of us speak the ancient language anymore, we’re often at a loss to understand what’s being described. What’s a ‘Krun Macula’ or ‘Soyuz Colles’?
Image I dug out of New Horizon’s LORRI archive shows Pluto’s nitrogen ice flows in Tombaugh Regio also shows several clumps of “colles”. Credit: NASA/Johns Hopkins University Applied Physics Laboratory/Southwest Research Institute
The first name is the proper name, so Krun denotes the Mandean god of the underworld. The second name – in Latin – describes the land form. Here’s a list of terms to help you translate the Plutonian and Charonian landscapes (plurals in parentheses):
Regio (Regi): Region
Mons (Montes): Mountain
Collis (Colles): Hill
Chasma (Chasmae): Canyon
Terra (Terrae): Land
Fossa (Fossae): Depression or fissure
Macula (Maculae): Spot
Valles (Valles): Valley
Rupes (Rupes): Cliff
Linea (Linea): Line
Dorsum (Dorsa): Wrinkle ridge
Cavus (Cava): Cavity or pit
Another LORRI photo showing icy Tombaugh Regio butting up against rugged, mountainous (montes) terrain. Credit: NASA/Johns Hopkins University Applied Physics Laboratory/Southwest Research Institute
A colorful piece of rainbow begs the question - why Roy G. Biv? Credit: Bob King
Children often ask simple questions that make you wonder if you really understand your subject. An young acquaintance of mine named Collin wondered why the colors of the rainbow were always in the same order — red, orange, yellow, green, blue, indigo, violet. Why don’t they get mixed up?
The familiar sequence is captured in the famous Roy G. Biv acronym, which describes the sequence of rainbow colors beginning with red, which has the longest wavelength, and ending in violet, the shortest. Wavelength — the distance between two successive wave crests — and frequency, the number of waves of light that pass a given point every second, determine the color of light.
The familiar colors of the rainbow spectrum with wavelengths shown in nanometers. Credit: NASA
The cone cells in our retinas respond to wavelengths of light between 650 nanometers (red) to 400 (violet). A nanometer is equal to one-billionth of a meter. Considering that a human hair is 80,000-100,000 nanometers wide, visible light waves are tiny things indeed.
So why Roy G. Biv and not Rob G. Ivy? When light passes through a vacuum it does so in a straight line without deviation at its top speed of 186,000 miles a second (300,000 km/sec). At this speed, the fastest known in the universe as described in Einstein’s Special Theory of Relativity, light traveling from the computer screen to your eyes takes only about 1/1,000,000,000 of second. Damn fast.
But when we look beyond the screen to the big, wide universe, light seems to slow to a crawl, taking all of 4.4 hours just to reach Pluto and 25,000 years to fly by the black hole at the center of the Milky Way galaxy. Isn’t there something faster? Einstein would answer with an emphatic “No!”
A laser beam (left) shining through a glass of water demonstrates how many times light changes speed — from 186,222 miles per second (mps) in air to 124,275 mps through the glass. It speeds up again to 140,430 mps in water, slows down when passing through the other side of the glass and then speeds up again when leaving the glass for the air. Credit: Bob King
One of light’s most interesting properties is that it changes speed depending on the medium through which it travels. While a beam’s velocity through the air is nearly the same as in a vacuum, “thicker” mediums slow it down considerably. One of the most familiar is water. When light crosses from air into water, say a raindrop, its speed drops to 140,430 miles a second (226,000 km/sec). Glass retards light rays to 124,275 miles/second, while the carbon atoms that make up diamond crunch its speed down to just 77,670 miles/second.
Why light slows down is a bit complicated but so interesting, let’s take a moment to describe the process. Light entering water immediately gets absorbed by atoms of oxygen and hydrogen, causing their electrons to vibrate momentarily before it’s re-emitting as light. Free again, the beam now travels on until it slams into more atoms, gets their electrons vibrating and gets reemitted again. And again. And again.
A ray of light refracted by a plastic block. Notice that the light bends twice – once when it enters (moving from air to plastic) and again when it exits (plastic to air). The beam slows down on entering and then speeds up again when it exits.
Like an assembly line, the cycle of absorption and reemission continues until the ray exits the drop. Even though every photon (or wave – your choice) of light travels at the vacuum speed of light in the voids between atoms, the minute time delays during the absorption and reemission process add up to cause the net speed of the light beam to slow down. When it finally leaves the drop, it resumes its normal speed through the airy air.
Light rays get bent or refracted when they move from one medium to another. We’ve all seen the “broken pencil” effect when light travels from air into water.
Let’s return now to rainbows. When light passes from one medium to another and its speed drops, it also gets bent or refracted. Plop a pencil in a glass half filled with water and and you’ll see what I mean.
Up to this point, we’ve been talking about white light only, but as we all learned in elementary science, Sir Isaac Newton conducted experiments with prisms in the late 1600s and discovered that white light is comprised of all the colors of the rainbow. It’s no surprise that each of those colors travels at a slightly different speed through a water droplet. Red light interacts only weakly with the electrons of the atoms and is refracted and slowed the least. Shorter wavelength violet light interacts more strongly with the electrons and suffers a greater degree of refraction and slowdown.
Isaac Newton used a prism to separate light into its familiar array of colors. Like a prism, a raindrop refracts incoming sunlight, spreading it into an arc of rainbow colors with a radius of 42. The colors spread out when light enter the drop and then spread out more when they leave and speed up. Left: NASA image, right, public domain with annotations by the author
Rainbows form when billions of water droplets act like miniature prisms and refract sunlight. Violet (the most refracted) shows up at the bottom or inner edge of the arc. Orange and yellow are refracted a bit less than violet and take up the middle of the rainbow. Red light, least affected by refraction, appears along the arc’s outer edge.
Rainbows are often double. The secondary bow results from light reflecting a second time inside the raindrop. When it emerges, the colors are reversed (red on the bottom instead of top), but the order of colors is preserved. Credit: Bob King
Because their speeds through water (and other media) are a set property of light, and since speed determines how much each is bent as they cross from air to water, they always fall in line as Roy G. Biv. Or the reverse order if the light beam reflects twice inside the raindrop before exiting, but the relation of color to color is always preserved. Nature doesn’t and can’t randomly mix up the scheme. As Scotty from Star Trek would say: “You can’t change the laws of physics!”
So to answer Collin’s original question, the colors of light always stay in the same order because each travels at a different speed when refracted at an angle through a raindrop or prism.
Light of different colors have both different wavelengths (distance between successive wave crests) and frequencies. In this diagram, red light has a longer wavelength and more “stretched out” waves compared to purple light of higher frequency. Credit: NASA
Not only does light change its speed when it enters a new medium, its wavelength changes, but its frequency remains the same. While wavelength may be a useful way to describe the colors of light in a single medium (air, for instance), it doesn’t work when light transitions from one medium to another. For that we rely on its frequency or how many waves of colored light pass a set point per second.
Higher frequency violet light crams in 790 trillion waves per second (cycles per second) vs. 390 trillion for red. Interestingly, the higher the frequency, the more energy a particular flavor of light carries, one reason why UV will give you a sunburn and red light won’t.
When a ray of sunlight enters a raindrop, the distance between each successive crest of the light wave decreases, shortening the beam’s wavelength. That might make you think that that its color must get “bluer” as it passes through a raindrop. It doesn’t because the frequency remains the same.
We measure frequency by dividing the number of wave crests passing a point per unit time. The extra time light takes to travel through the drop neatly cancels the shortening of wavelength caused by the ray’s drop in speed, preserving the beam’s frequency and thus color. Click HERE for a further explanation.
Why prisms/raindrops bend and separate light
Before we wrap up, there remains an unanswered question tickling in the back of our minds. Why does light bend in the first place when it shines through water or glass? Why not just go straight through? Well, light does pass straight through if it’s perpendicular to the medium. Only if it arrives at an angle from the side will it get bent. It’s similar to watching an incoming ocean wave bend around a cliff. For a nice visual explanation, I recommend the excellent, short video above.
We've never seen a comet as close as this. Taken shortly before touchdown by the Philae lander on November 12, 2014, you're looking across a scene just 32 feet from side to side (9.7-meters) or about the size of a living room. Part of the lander is visible at upper right. Credit: ESA/Rosetta/Philae/ROLIS/DLR
With just 12 days before Comet 67P/Churyumov-Gerasimenko reaches perihelion, we get a look at recent images and results released by the European Space Agency from the Philae lander along with spectacular 3D photos from Rosetta’s high resolution camera.
Slow animation of images taken by Philae’s Rosetta Lander Imaging System, ROLIS, trace the lander’s descent to the first landing site, Agilkia, on Comet 67P/Churyumov–Gerasimenko on November 12, 2014. Credits: ESA/Rosetta/Philae/ROLIS/DLR
Remarkably, some 80% of the first science sequence was completed in the 64 hours before Philae fell into hibernation. Although unintentional, the failed landing attempt led to the unexpected bonus of getting data from two collection sites — the planned touchdown at Agilkia and its current precarious location at Abydos.
After first touching down, Philae was able to use its gas-sniffing Ptolemy and COSAC instruments to determine the makeup of the comet’s atmosphere and surface materials. COSAC analyzed samples that entered tubes at the bottom of the lander and found ice-poor dust grains that were rich in organic compounds containing carbon and nitrogen. It found 16 in all including methyl isocyanate, acetone, propionaldehyde and acetamide that had never been seen in comets before.
While you and I may not be familiar with some of these organics, their complexity hints that even in the deep cold and radiation-saturated no man’s land of outer space, a rich assortment of organic materials can evolve. Colliding with Earth during its early history, comets may have delivered chemicals essential for the evolution of life.
This 3D image focuses on the largest boulder seen in the image captured 221 feet (67.4 m) above Comet 67P/Churyumov–Gerasimenko looks best in a pair of red-blue 3D glasses. Many fractures, along with a tapered ‘tail’ of debris and excavated ‘moat’ around the 5 m-high boulder, are plain to see. Credit: ESA/Rosetta/Philae/ROLIS/DLR
Ptolemy sampled the atmosphere entering tubes at the top of the lander and identified water vapor, carbon monoxide and carbon dioxide, along with smaller amounts of carbon-bearing organic compounds, including formaldehyde. Some of these juicy organic delights have long been thought to have played a role in life’s origins. Formaldehyde reacts with other commonly available materials to form complex sugars like ribose which forms the backbone of RNA and is related to the sugar deoxyribose, the “D” in DNA.
ROLIS (Rosetta Lander Imaging System) images taken shortly before the first touchdown revealed a surface of 3-foot-wide (meter-size) irregular-shaped blocks and coarse “soil” or regolith covered in “pebbles” 4-20 inches (10–50 cm) across as well as a mix of smaller debris.
Philae used its thermal sensor to measure daily highs and lows on the comet (top graph). The bottom graph shows time vs. depth when Philae used its penetrator to hammer into the soil. Credit: Spacecraft graphic: ESA/ATG medialab; data from Spohn et al (2015)
Agilkia’s regolith, the name given to the rocky soil of other planets, moons, comets and asteroids, is thought to extend to a depth of about 6 feet (2 meters) in places, but seems to be free from fine-grained dust deposits at the resolution of the images. The 16-foot-high boulder in the photo above has been heavily fractured by some type of erosional process, possibly a heating and cooling cycle that vaporized a portion of its ice. Dust from elsewhere on the comet has been transported to the boulder’s base. This appears to happen over much of 67P/C-G as jets shoot gas and dust into the coma, some of which then settles out across the comet’s surface.
Another suite of instruments called MUPUS used a penetrating “hammer” to reveal a thin layer of dust about an inch thick (~ 3 cm) overlying a much harder, compacted mixture of dust and ice at Abydos. The thermal sensor took the comet’s daily temperature which varies from a high around –229° F (–145ºC) to a nighttime low of about –292° F (–180ºC), in sync with the comet’s 12.4 hour day. The rate at which the temperature rises and falls also indicates a thin layer of dust rests atop a compacted dust-ice crust.
Based on the most recent calculations using CONSERT data and detailed comet shape models, Philae’s location has been revised to an area covering 69 x 112 feet (21 x 34 m). The best fit area is marked in red, a good fit is marked in yellow, with areas on the white strip corresponding to previous estimates now discounted. Credit: ESA/Rosetta/Philae/CONSERT
CONSERT, which passed radio waves through the nucleus between the lander and the orbiter, showed that the small lobe of the comet is a very loosely compacted mixture of dust and ice with a porosity of 75-85%, about that of lightly compacted snow. CONSERT was also used to help triangulate Philae’s location on the surface, nailing it down to an area just 69 x 112 feet ( 21 x 34 m) wide.
The orbit of Comet 67P/Churyumov–Gerasimenko and its approximate location around perihelion, the closest the comet gets to the Sun. The positions of the planets are correct for August 13, 2015. The comet will pass closest to Earth in February 2016 at 135.6 million miles but will be brightest this month right around perihelion. Copyright: ESA
In fewer than two weeks, the comet will reach perihelion, its closest approach to the Sun at 116 million miles (186 million km), and the time when it will be most active. Rosetta will continue to monitor 67P C-G from a safe distance to lessen the chance an errant chunk of comet ice or dust might damage its instruments. Otherwise it’s business as usual. Activity will gradually decline after perihelion with Rosetta providing a ringside seat throughout. The best time for viewing the comet from Earth will be mid-month when the Moon is out of the morning sky. Watch for an article with maps and directions soon.
Comet 67P/C-G on July 20, 2015 taken from a distance of 106 miles (171 km) from the comet’s center. Rosetta has been keeping a safe distance recently as 67P/C-G approaches the August 13th perihelion. Credit: ESA/Rosetta/NAVCAM – CC BY-SA IGO 3.0
“With perihelion fast approaching, we are busy monitoring the comet’s activity from a safe distance and looking for any changes in the surface features, and we hope that Philae will be able to send us complementary reports from its location on the surface,” said Philae lander manager Stephan Ulamec.
OSIRIS narrow-angle camera image showing the smooth nature of the dust covering the Ash region and highlighting the contrast with the more brittle material exposed underneath in Seth. Credits: ESA/Rosetta/MPS for OSIRIS Team MPS/UPD/LAM/IAA/SSO/INTA/UPM/DASP/IDA
More about Philae’s findings can be found in the July 31 issue of Science. Before signing off, here are a few detailed, 3D images made with the high-resolution OSIRIS camera on Rosetta. Once you don a pair of red-blue glasses, click the photos for the high-res versions and get your mind blown.
Mosaic of two images showing an oblique view of the Atum region and its contact with Apis, the flat region in the foreground. This region is rough and pitted, with very few boulders. Credits: ESA/Rosetta/MPS for OSIRIS Team MPS/UPD/LAM/IAA/SSO/INTA/UPM/DASP/IDAImage highlighting an alcove structure at the Hathor-Anuket boundary on the comet’s small lobe. The layering seen in the alcove could be indicative of the internal structure of the comet. Credits: ESA/Rosetta/MPS for OSIRIS Team MPS/UPD/LAM/IAA/SSO/INTA/UPM/DASP/IDAImhotep region in 3D. Credit: ESA/Rosetta/MPS for OSIRIS Team MPS/UPD/LAM/IAA/SSO/INTA/UPM/DASP/IDA
It’s a staple of scifi, and a requirement if we’re going to travel long-term in space. Will we ever develop artificial gravity?
It’s safe to say we’ve spent a significant amount of our lives consuming science fiction.
Berks, videos, movies and games.
Science fiction is great for the imagination, it’s rich in iron and calcium, and takes us to places we could never visit. It also helps us understand and predict what might happen in the future: tablet computers, cloning, telecommunication satellites, Skype, magic slidey doors, and razors with 5 blades.
These are just some of the predictions science fiction has made which have come true.
Then there are a whole bunch of predictions that have yet to happen, but still might, Fun things like the climate change apocalypse, regular robot apocalypse, the giant robot apocalypse, the alien invasion apocalypse, the apocalypse apocalypse, comet apocalypse, and the great Brawndo famine of 2506. Continue reading “Could We Make Artificial Gravity?”
Tenth planet? Artists concept of the view from Eris with Dysnomia in the background, looking back towards the distant sun. Credit: Robert Hurt (IPAC)
Ask a person what Dysnomia refers to, and they might venture that it’s a medical condition. In truth, they would be correct. But in addition to being a condition that affects the memory (where people have a hard time remembering words and names), it is also the only known moon of the distant dwarf planet Eris.
In fact, the same team that discovered Eris a decade ago – a discovery that threw our entire notion of what constitutes a planet into question – also discovered a moon circling it shortly thereafter. As the only satellite that circles one of the most distant objects in our Solar System, much of what we know about this ball of ice is still subject to debate.
Discovery and Naming:
In January of 2005, astronomer Mike Brown and his team discovered Eris using the new laser guide star adaptive optics system at the W. M. Keck Observatory in Hawaii. By September, Brown and his team were conducting observations of the four brightest Kuiper Belt Objects – which at that point included Pluto, Makemake, Haumea, and Eris – and found indications of an object orbiting Eris.
Provisionally, this body was designated S/2005 1 (2003 UB³¹³). However, in keeping with the Xena nickname that his team was already using for Eris, Brown and his colleagues nicknamed the moon “Gabrielle” after Xena’s sidekick. Later, Brown selected the official name of Dysnomia for the moon, which seemed appropriate for a number of reasons.
For one, this name is derived from the daughter of the Greek god Eris – a daemon who represented the spirit of lawlessness – which was in keeping with the tradition of naming moons after lesser gods associated with the primary god. It also seemed appropriate since the “lawless” aspect called to mind actress Lucy Lawless, who portrayed Xena on television. However, it was not until the IAU’s resolution on what defined a planet – passed in August of 2006 – that the planet was officially designated as Dysnomia.
Size, Mass and Orbit:
The actual size of Dysnomia is subject to dispute, and estimates are based largely on the planet’s albedo relative to Eris. For example, the IAU and Johnston’s Asteroids with Satellites Database estimate that it is 4.43 magnitudes fainter than Eris and has an approximate diameter of between 350 and 490 km (217 – 304 miles)
However, Brown and his colleagues have stated that their observations indicate it to be 500 times fainter and between 100 and 250 km (62 – 155 miles) in diameter. Using the Herschel Space Observatory in 2012, Spanish astronomer Pablo Santo Sanz and his team determined that, provided Dysnomia has an albedo five times that of Eris, it is likely to be 685±50 km in diameter.
Eris and its moon, Dysnomia, as imaged by the W.M. Keck Observatory in Hawaii. Credits:NASA/ESA and M. Brown/Caltech
In 2007, Brown and his team also combined Keck and Hubble observations to determine the mass of Eris, and estimate the orbital parameters of the system. From their calculations, they determined that Dysnomia’s orbital period is approximately 15.77 days. These observations also indicated that Dysnomia has a circular orbit around Eris, with a radius of 37350±140 km. In addition to being a satellite of a dwarf planet, Dysnomia is also a Kuiper Belt Object (KBO) like Eris.
Composition and Origin:
Currently, there is no direct evidence to indicate what Dysnomia is made of. However, based on observations made of other Kuiper Belt Objects, it is widely believed that Dysnomia is composed primarily of ice. This is based largely on infrared observations made of Haumea (2003 EL61), the fourth largest object in the Kuiper Belt (after Eris, Pluto and Makemake) which appears to be made entirely of frozen water.
Astronomers now know that three of the four brightest KBOs – Pluto, Eris and Haumea – have one or more satellites. Meanwhile, of the fainter members, only about 10% are known to have satellites. This is believed to imply that collisions between large KBOs have been frequent in the past. Impacts between bodies of the order of 1000 km across would throw off large amounts of material that would coalesce into a moon.
Artist’s concept of Kuiper Belt Object Eris and its tiny satellite Dysnomia. The Hubble Space Telescope and Keck Observatory took images of Dysnomia’s movement from which astronomer Mike Brown (Caltech) precisely calculated Eris to be 27 percent more massive than Pluto. Credit: NASA/ESA/Adolph Schaller (for STScI)
This could mean that Dysnomia was the result of a collision between Eris and a large KBO. After the impact, the icy material and other trace elements that made up the object would have evaporated and been ejected into orbit around Eris, where it then re-accumulated to form Dysnomia. A similar mechanism is believed to have led to the formation of the Moon when Earth was struck by a giant impactor early in the history of the Solar System.
Since its discovery, Eris has lived up to its namesake by stirring things up. However, it has also helped astronomers to learn many things about this distant region of the Solar System. As already mentioned, astronomers have used Dysnomia to estimate the mass of Eris, which in turn helped them to compare it to Pluto.
While astronomers already knew that Eris was bigger than Pluto, but they did not know whether it was more massive. This they did by measuring the distance between Dysnomia and how long it takes to orbit Eris. Using this method, astronomers were able to discover that Eris is 27% more massive than Pluto is.
With this knowledge in hand, the IAU then realized that either Eris needed to be classified as a planet, or that the term “planet” itself needed to be refined. Ergo, one could make that case that it was the discovery of Dysnomia more than Eris that led to Pluto no longer being designated a planet.
Move over, Pluto... Disney already has dibs on Mercury as seen in this MESSENGER photo. Image credit: NASA/JHAPL/Carnegie institution of Washington
“Look, it has a tiny face on it!”
This sentiment was echoed ‘round the web recently, as an image of Pluto’s tiny moon Nix was released by the NASA New Horizons team. Sure, we’ve all been there. Lay back in a field on a lazy July summer’s day, and soon, you’ll see faces of all sorts in the puffy stratocumulus clouds holding the promise of afternoon showers.
Pluto’s moon Nix as imaged by New Horizons from 590,000 kilometers distant. Image credit: NASA/JHUAPL/SWRI
This predilection is so hard-wired into our brains, that often our facial recognition software sees faces where there are none. Certainly, seeing faces is a worthy survival strategy; not only is this aspect of cognition handy in recognizing the friendlies of our own tribe, but it’s also useful in the reading of facial expressions by giving us cues of the myriad ‘tells’ in the social poker game of life.
And yes, there’s a term for the illusion of seeing faces in the visual static: pareidolia. We deal lots with pareidolia in astronomy and skeptical circles. As NASA images of brave new worlds are released, an army of basement bloggers are pouring over them, seeing miniature bigfoots, flowers, and yes, lots of humanoid figures and faces. Two craters and the gash of a trench for a mouth will do.
Now that new images of Pluto and its entourage of moons are pouring in, neural circuits ‘cross the web are misfiring, seeing faces, half-buried alien skeletons and artifacts strewn across Pluto and Charon. Of course, most of these claims are simply hilarious and easily dismissed… no one, for example, thinks the Earth’s Moon is an artificial construct, though its distorted nearside visage has been gazing upon the drama of humanity for millions of years.
Do you see the ‘Man in the Moon?’ Image credit: Dave Dickinson
The psychology of seeing faces is such that a whole region of the occipital lobe of the brain known as the fusiform face area is dedicated to facial recognition. We each have a unique set of neurons that fire in patterns to recognize the faces of Donald Trump and Hillary Clinton, and other celebs (thanks, internet).
Damage this area at the base of the brain or mess with its circuitry, and a condition known as prosopagnosia, or face blindness can occur. Author Oliver Sacks and actor Brad Pitt are just a few famous personalities who suffer from this affliction.
The ‘Snowman of Vesta,’ as imaged by NASA’s Dawn spacecraft. Image credit: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA
Conversely, ‘super-recognizers’ at the other end of the spectrum have a keen sense for facial identification that verges on a super-power. True story: my wife has just such a gift, and can immediately spot second-string actors and actresses in modern movies from flicks and television shows decades old.
It would be interesting to know if there’s a correlation between face blindness, super-recognition and seeing faces in the shadows and contrast on distant worlds… to our knowledge, no such study has been conducted. Do super-recognizers see faces in the shadowy ridges and craters of the solar system more or less than everyone else?
A well-known example was the infamous ‘Face on Mars.’ Imaged by the Viking 1 orbiter in 1976, this half in shadow image looked like a human face peering back up at us from the surface of the Red Planet from the Cydonia region.
Image credit: The ‘Face on Mars’: HiRISE vs Viking 1 (inset): Image credit: NASA/JPL
But when is a face not a face?
Now, it’s not an entirely far-fetched idea that an alien entity visiting the solar system would place something (think the monolith on the Moon from Arthur C. Clarke’s 2001: A Space Odyssey) for us to find. The idea is simple: place such an artifact so that it not only sticks out like a sore thumb, but also so it isn’t noticed until we become a space-faring society. Such a serious claim would, however, to paraphrase Carl Sagan, demand serious and rigorous evidence.
But instead of ‘Big NASA’ moving to cover up the ‘face,’ they did indeed re-image the region with both the Mars Reconnaissance Orbiter and Mars Global Surveyor at a much higher resolution. Though the 1.5 kilometer feature is still intriguing from a geological perspective… it’s now highly un-facelike in appearance.
A ‘face’ or… more fun with ‘scifi spacecraft pareidolia.’ Image credit: NASA/JPL/Paramount Pictures
Of course, it won’t stop the deniers from claiming it was all a big cover-up… but if that were the case, why release such images and make them freely available online? We’ve worked in the military before, and can attest that NASA is actually the most transparent of government agencies.
We also know the click bait claims of all sorts of alleged sightings will continue to crop up across the web, with cries of ‘Wake up, Sheeople!’ (usually in all caps) as a brave band of science-writing volunteers continue to smack down astro-pareidolia on a pro bono basis in battle of darkness and light which will probably never end.
What examples of astro-pareidolia have you come across in your exploits?
An artificially created 'Blue Moon,' using the white balance settings on the camera. Image credit and copyright: John Chumack
Brace yourselves for Blue Moon madness. The month of July 2015 hosts two Full Moons: One on July 2nd and another coming right up this week on Friday, July 31st at 10:43 Universal Time (UT)/6:43 AM EDT.
In modern day vernacular, the occurrence of two Full Moons in one calendar month has become known as a ‘Blue Moon.’ This is a result of the synodic period (the amount of time it takes for the Moon to return to a like phase, in this case Full back to Full) of 29.5 Earth days being less than every calendar month except February.
In the ‘two Full Moons in one month’ sense, the last time a Blue Moon occurred was on August 31st, 2012, and the next is January 31st, 2018. The next time a Blue Moon occurs in the month of July is 2034, and the last July Blue Moon was 2004.
We say “once in a blue Moon,” as if it’s a rarity, but as you can see, they’re fairly frequent, occurring nearly once every 2-3 years or so.
Now, we’ll let you in on a secret. Like its modern internet meme cousin the ‘Super-Moon,’ astronomers don’t sit in mountain top observatories discussing the vagaries of the Blue Moon. In fact, astronomers rarely like to observe during the weeks surrounding the light-polluting Full Moon, and often compile data from the comfort of their university offices rather than visit mountaintop observatories these days…
The modern Blue Moon is now more of a cultural phenomenon. We’ve written previously about how an error brought us to the current ‘two Full Moons in one month definition.’ A more convoluted old timey definition was introduced in ye ole Maine Farmer’s Almanac circa 1930s as “the third Full Moon in an astronomical season with four.”
Legend has it that the Maine Farmer’s Almanac denoted this pesky extra seasonal Full Moon with ‘blue’ instead of black ink… to our knowledge, no examples exist to support this intriguing tale. Anyone have any old almanacs in the attic holding such a revelation out there?
The ghostly glow of the gibbous moon in Jean-Francois Millet’s The Sheepfold. Image Credit: Public Domain
The rising waxing gibbous Moon on the night of September 23rd, 1950. Image credit: Stellarium
Of course, the Moon most likely won’t appear to be physically blue, no matter what friends/family/co-workers/anonymous persons on Twitter say. The Moon can actually appear blue, as it did on September 23rd, 1950 for much of the eastern United States and Canada through the haze of several forest fires in western Canada. The Moon was actually at waxing gibbous phase on the evening of this phenomenon, and as far as we can tell, no photographic documentation of this event exists. Spaceweather, has, however gathered a gallery of blue moon eyewitness reports over the years, including a few images. This occurs when moonlight is filtered through suspended oil drops about a micrometer in diameter which scattered yellow and red light, leaving a Moon with a ghostly indigo glow.
The 2012 Blue Moon as seen rising from Hudson, Florida. Image credit: Dave Dickinson
So there’s definitely another challenge to catch and photograph a truly ‘Blue Moon’ under such rare atmospheric circumstances… and remember, the Moon doesn’t have to be near Full to do it!
Watch that Moon, as we’ve got a few red letter dates coming up through the remainder of 2015. First up: the Supermoon season cometh in August, as we have a series of three Full Moons falling less than 24 hours from perigee on August 29th, September 28th, and October 27th. Our money is on that middle one as having the potential to generate the most online lunacy, as it’s also the last total lunar eclipse of the current tetrad of four total lunar eclipses for 2014 and 2015, a ‘super-blood moon eclipse’ anyone? Though the dead won’t rise from the grave to mark such an occasion, you can be sure that many a sky aficionado will stumble zombie-like into the office the next day after pulling an all-nighter for the last good North American total lunar eclipse until 2018.
And it’s worth noting the path of the Moon, as it reaches its shallow mid-point in the last half of 2015. The Moon’s orbit is tilted about five degrees relative to the ecliptic, meaning that it can ride anywhere from 18 degrees—as it does this year—to 28 degrees from the celestial equator. This cycle takes about 19 years to complete, and a wide-ranging ‘long nights Moon’ last occurred in 2006, and will next occur in 2025.
A ‘mock Blue Moon…’ induced by use of a military flashlight filter. Image credit: Dave Dickinson
So don’t fear the Blue Moon, but be sure to take a stroll under its light this coming Friday… and perhaps enjoy a frosty Blue Moon beer on the eve of the sultry month of August.
This artist's concept depicts one possible appearance of the planet Kepler-452b, the first near-Earth-size world to be found in the habitable zone of star that is similar to our sun. Credit: NASA Ames/JPL-Caltech/T. Pyle
Scientists say NASA’s Kepler Space Telescope has discovered Earth’s “older, bigger first cousin” – a planet that’s about 60 percent bigger than our own, circling a sunlike star in an orbit that could sustain liquid water and perhaps life.
“Today, Earth is a little bit less lonely, because there’s a new kid on the block,” Kepler data analysis lead Jon Jenkins, a computer scientist at NASA’s Ames Research Center, said Thursday during a NASA teleconference about the find.
The alien world, known as Kepler-452b, is about 1,400 light-years away in the constellation Cygnus – too far away to reach unless somebody perfects interstellar transporters. But its discovery raises the bar yet again in the search for Earth 2.0, which is a big part of Kepler’s mission.
Jenkins said that Kepler-452b has a better than even chance of being a rocky planet (though there’s some question about that). Its size implies that it’s about five times as massive as Earth. He said the planet might be cloudier than Earth and volcanically active, based on geological modeling. Visiting Earthlings would weigh twice as much as they did on Earth – until they walked around for a few weeks and “lost some serious pounds,” he joked.
An artist’s impression shows the surface of Kepler 452b. In the scenario depicted here, the planet is just entering a runaway greenhouse phase of its climate history. Kepler 452b could be giving us a preview of what Earth will undergo more than a billion years from now as the sun ages and grows brighter. Credit: Danielle Futselaar / SETI Institute
The planet is about 5 percent farther from its parent star than Earth is from our sun, with a year that lasts 385 days. Its sun is 10 percent bigger and 20 percent brighter than our sun, with the same classification as a G2 dwarf. But Kepler-452b’s star is older than our 4.6 billion-year-old home star – which suggests the cosmic conditions for life could be long-lasting.
“It’s simply awe-inspiring to consider that this planet has spent 6 billion years in the habitable zone of its star, which is longer than the age of the Earth,” Jenkins said. Models for planetary development suggest that Kepler-452b would experience an increasing warming trend and perhaps a runaway greenhouse effect as it aged, he said.
Kepler-452b’s advantages trump the mission’s earlier planetary discoveries. One involved a rocky planet, just a little bigger than Earth, that was found in its parent star’s habitable zone – that is, the kind of orbit where liquid water could exist. But that star, known as Kepler-186, is a shrunken red dwarf rather than a close analog to the sun.
Kepler research scientist Jeff Coughlin said it’s not clear how hospitable a planet circling a red dwarf might be. A rocky planet in the right orbit around a sunlike star is a surer bet. “We’re here on Earth, we know there’s life here,” he said.
Scientists said Kepler-452b is on the target list for the SETI Institute’s search for radio signals from extraterrestrial civilizations, using the Allen Telescope Array in California – but no alien detection has been reported. “So far, the 452b-ians have been coy,” Seth Shostak, the institute’s senior astronomer and director of the Center for SETI Research, told Universe Today in an email.
This size and scale of the Kepler-452 system compared alongside our own solar system, plus another planetary system with a habitable-zone planet known as Kepler-186f. The Kepler-186 system has a faint red dwarf star.
John Grunsfeld, NASA’s associate administrator for science, characterized the newly announced planet as the “closest twin” to Earth discovered so far. However, he said further analysis of the Kepler data may turn up even closer relatives.
Launched in 2009, Kepler detects alien worlds by looking for the faint dimming of a star as a planet crosses its disk. The SUV-sized telescope has spotted more than 4,600 planet candidates.
So far, about 1,000 of those have been confirmed as planets using other methods, ranging from detecting their parent stars’ Doppler shifts to carefully measuring the time intervals between the passages of planets. For Kepler-452b, scientists used ground-based observations and computer models to estimate the mass and confirm the detection to a level of 99.76 percent, Jenkins said.
The findings were due to be published online Thursday by the Astrophysical Journal, Jenkins said. In addition to Kepler-452b, another 521 planet candidates have been added to the mission’s checklist – including 12 candidates that appear to be one to two times as wide as Earth and orbit in their parent stars’ habitable zones. Nine of the stars are similar to our own sun in size and temperature, NASA said in a news release.
There’s sure to be more to come. In 2013, Kepler was crippled by failures of its fine-pointing navigation system, but it returned to its planet-hunting mission last year, thanks to some clever tweaking that makes use of the solar wind as an extra stabilizer. “It’s kind of the best-worst thing that ever happened to Kepler,” Jenkins said.
