Jupiter +Great Red Spot as seen on January 22nd 2015. Credit:
Did you see the brilliant Full Snow Moon rising last night? Then you might’ve also noticed a bright nearby ‘star’. Alas, that was no star, but the largest planet in our solar system, Jupiter. And it was no coincidence that the king of the gas giants is near the Full Moon this February, as Jupiter reaches opposition this Friday on February 6th at 18:00 Universal Time or 1:00 PM EST.
As the term implies, opposition simply means that an outer planet sits opposite to the Sun. Mercury and Venus can never reach opposition. Orbiting the Sun once every 11.9 years, oppositions for Jupiter occur once every 399 days, or roughly every 13 months. This means that only one opposition for Jupiter can happen per year max, and these events precess forward on the Gregorian calendar by about a month and move one zodiacal constellation eastward per year.
Through a telescope, Jupiter exhibits an ochre disk 40” in diameter striped with two main cloud belts. The northern equatorial belt seems permanent, while the southern equatorial belt is prone to pulling a ‘disappearing act’ every decade of so, as last occurred in 2010. The Great Red Spot is another prominent feature gracing the Jovian cloud tops, though its appeared salmon to brick-colored in recent years and seems to be shrinking.
Jupiter rotates once every 9.9 hours, fast enough that you can watch one full rotation in a single night.
Jupiter near opposition in 2014. Photo by author.
It’s also fascinating to watch the nightly dance of Jupiter’s four large moons Io, Europa, Ganymede and Callisto as they alternatively cast shadows on the Jovian cloud tops and disappear into its shadow. Near opposition, this shadow casting activity is nearly straight back as seen from our perspective. Here is the tiny ‘mini-solar system’ that fascinated Galileo and further convinced him that the Earth isn’t the center of the cosmos. Jupiter has 67 moons in all, though only 4 are within range of modest sized telescopes… Even 5th place runner up Himalia is a challenge near the dazzling disk of Jove at +14th magnitude.
Also watch for a phenomenon known as the Seeliger or Opposition Effect, a sudden surge in brightness like a highway retro-reflector in the night.
Opposition 2015 finds Jupiter just across the Leo-Cancer border in the realm of the Crab. Jupiter crossed from Leo into Cancer on February 4th, and will head back into the constellation of the Lion on June 10th. Jupiter then spends the rest of 2015 in Leo and heads for another opposition next year on March 8th.
Jupiter will also make a dramatic pass just 24’ — less than the diameter of the Full Moon — from Regulus on August 11th, though both are only 11.5 degrees east of the Sun in the dusk sky. Jupiter also forms a 1 degree circle with Regulus, Mercury and Jupiter 14.5 degrees east of the Sun on August 7th.
Jupiter reaches a maximum declination north for 2015 on April 7th at 18 degrees above the celestial equator. We’re still in a favorable cycle of oppositions for Jupiter for northern hemisphere viewers, as the gas giant doesn’t plunge south of the equator until September 2016.
Looking farther ahead, Jupiter reaches east quadrature on May 4th, and sits 90 degrees elongation from the Sun as the planet and its moons cast their shadows far off to the side from our Earthly perspective. We’re still also in the midst of a plane crossing: February 5th is actually equinox season on Jupiter! This also means that there’s still a cycle of mutual eclipses and occultations of the Jovian moons in progress. One such complex ballet includes (moons) on the night of February 26th.
The close grouping of Io, Callisto and Ganymede on the night of February 26th. Created using Starry Night Education software.
And yes, it is possible to see the Earth transit the disk of the Sun from Jove’s vantage point. This last occurred in 2014, and will next occur in 2020.
But wait, there’s more. Jupiter also makes a thrilling pass near Venus on July 1st, when the two sit just 0.4 degrees apart. We fully expect a spike in “what are those two bright stars?” queries right around that date, though hopefully, the conjunction won’t spark any regional conflicts.
Jupiter, Regulus and the rising waning gibbous Moon on the evening of February 4th. Credit: Stellarium.
Solar conjunction for Jupiter then occurs on August 26th, with the planet visible in the Solar Heliospheric Observatory’s (SOHO) LASCO C3 camera from August 16th to September 6th.
Emerging into the dawn sky, Jupiter then passes 0.4 degrees from Mars on October 17th and has another 1.1 degree tryst with Venus on October 26th.
Looking for Jupiter in the daytime near the waxing gibbous Moon. Credit: Stellarium.
Let the Jovian observing season begin!
-Wonder what a gang of rogue space clowns is doing at Jupiter? Read Dave Dickinson’s original tale Helium Party and find out!
The Amazon River near Lago do Erepecu (north of this image) in 2014. Credit: NASA
The Amazon River is a heck of a big tributary. Besides being one of the LONGEST rivers in the world, it also happens to be the WIDEST. While its estimated length of 4,000 miles (6,400 kilometers) puts it under the Nile River, that statistic could be amended as some believe it’s even longer than that.
Nevertheless, its width puts it at a big river that carries more volume than the Nile. We have a few more facts about the Amazon below.
According to Extreme Science, even during the dry season it is about 6.8 miles (11 kilometers) wide, which is still a respectable width. When things get rainy, however, that’s when stuff really begins to open up. It more than doubles its width to 24.8 miles (40 kilometers).
If that’s enough for you, consider the amount of land it covers. Dry season, Extreme Science says, sees it at 42,471 square miles (110,000 square kilometers), or roughly the land area of Cuba. That astonishing statistic triples during the wet season, when it reaches 135,135 square miles (350,000 square kilometers) — about approximate to Germany’s size.
Mouth of the Amazon River as seen from STS-58. Credit: NASA
All of this makes the South American river the largest drainage system in the world, according to Encyclopedia Britannica. Its recorded source is in the Andes Mountains and it flows down to its Atlantic Ocean mouth off the coast of Brazil. But as we’ve noted before, there’s controversy both to its source and to its actual length.
The Amazon basin (the areas that are affected by the river) cover a good portion of South America, the encyclopedia adds: Brazil, Peru, Columbia, Ecuador, Bolivia and Venezuela. But it’s Brazil that has most of the basin and two-thirds of the stream.
Aboriginals in the region have explored the river for centuries, but its name comes from European exploration of the river, the encyclopedia says. “Amazon” is a reference from Europe’s first reported explorer, Spanish soldier Francisco de Orellana, who said the fierce female warriors in battle in the area reminded him of Amazons in Greek mythology.
Mouth of Amazon River, Brazil as seen from the Gemini 9-A spacecraft. Credit: NASA
Many of these statistics could change if the source of the Amazon River is also changed. National Geographic says there at least six possible origin points, based on methods ranging from satellite observation to GPS to “ground truth” examinations. You can see more details about the ongoing quest in this article.
Universe Today has articles on the longest river and Europe’s longest river. Astronomy Cast has an episode on Earth you should watch.
A halo rings the bright moon and planet Jupiter (left of moon) Credit: Bob King
The Full Moon celebrates Jupiter’s coming opposition by accompanying the bright planet in a beautiful conjunction tonight.
Even last night Jupiter and the Moon were close enough to attract attention. Tonight they’ll be even more striking. Two reasons for that. The Moon is full this evening and will have crept within 41/2° of the planet. They’ll rise together and roll together all night long.
The Full Snow Moon will share the sky with Jupiter in Cancer tonight not far from the Sickle or head of Leo the Lion. The map shows the scene around 8 o’clock local time. Source: Stellarium
February’s full moon is aptly named the Full Snow Moon as snowfall can be heavy this month. Just ask the folks in Chicago. The Cherokee Indians called it the “Bone Moon”, named for the tough times experienced by many Native Americans in mid-winter when food supplies ran low. With little left to eat people made use of everything including bones and bone marrow for soup.
Not only is the Full Moon directly opposite the Sun in the sky, rising around sunset and setting around sunrise, but in mid-winter they’re nearly on opposite ends of the celestial seesaw.
Jupiter, like tonight’s Full Moon, will be directly opposite the Sun this Friday and in “full moon” phase. Because both planets are lined up on the same side of the Sun, Jupiter will also be at its closest to us for the year. Credit: Bob King
In early February the Sun is still near its lowest point in the sky (bottom of the seesaw) for the northern half of the globe. And while daylight is steadily increasing as the Sun moves northward, darkness still has the upper hand this month. Full Moons like tonight’s lie 180° opposite the Sun, placing the Moon near the top of the seesaw. Come early August, the Sun will occupy the Moon’s spot and the Full Moon will have slid down to the Sun’s current position. Yin and Yang folks.
Now here’s the interesting thing. Jupiter will also be in “full moon” phase when it reaches opposition this Friday Feb. 6. Take a look at the diagram. From our perspective on Earth, Jupiter and the Sun lie on opposite sides of our planet 180° apart. As the Sun sets Friday, Jupiter will rise in the east and remain visible all night until setting around sunrise exactly like a Full Moon.
So in a funny way, we have two Full Moons this week only one’s a planet.
Like me, a lot of you enjoy a good moonrise. That golden-orange globe, the crazy squished appearance at rising and the transition to the bright, white, beaming disk that throws enough light on a winter night to ski in the forest without a headlamp. All good reasons to be alive.
If Jupiter were moved to the Moon’s distance it would span about 20 degrees or 40 times the apparent diameter of the Full Moon. Credit: Roscosmos with additions by the author
To find when the moon rises for your town, click over to this moonrise calculator. As you step outside tonight to get your required Moon and Jupiter-shine, consider the scene if we took neighboring Jupiter and placed it at the same distance as the Moon. A recent series of such scenes was released by the Russian Federal Space Agency (Roscosmos). I included one here and added the Moon for you to compare. Is Jupiter enormous or what?
Artist's conception of an asteroid crashing into the Yucatan Peninsula about 65 million years ago. Credit: Donald E. Davis/NASA
What suddenly made the dinosaurs disappear 65 million or 66 million years ago? Whatever it was, all indications show that it was a massive extinction event. The fossil record not only shows dinosaurs disappearing, but also numerous other species of the era. Whatever it was, there was a sudden change in the environment that changed evolution forever.
The leading theory for this change is a small body (likely an asteroid or a comet) that slammed into Mexico’s Yucatan Peninsula. The impact’s force generated enough debris to block the Sun worldwide, killing any survivors of starvation.
The crater
There have been numerous theories proposed for the dinosaurs’ death, but in 1980 more evidence arose for a huge impact on the Earth. This happened when a father-son University of California, Berkeley research team — Luis Alvarez and Walter Alvarez — discovered a link with a 110-mile (177-kilometer) wide impact crater near the Yucatan coast of Mexico. It’s now known as Chicxulub.
Chicxulub crater in Mexico. Credit: Wikipedia/NASA
It sounds surprising that such a huge crater wasn’t found until that late, especially given satellites had been doing Earth observation for the better part of 20 years at that point. But as NASA explains, “Chicxulub … eluded detection for decades because it was hidden (and at the same time preserved) beneath a kilometer of younger rocks and sediments.”
The data came from a Mexican company that was seeking oil in the region. The geologists saw the structure and guessed, from its circular shape, that it was an impact crater. Further observations were done using magnetic and gravity data, NASA said, as well as space observations (including at least one shuttle mission).
The layer
The asteroid’s impact on Earth was quite catastrophic. Estimated at six miles (9.7 kilometers) wide, it carved out a substantial amount of debris that spread quickly around the Earth, aided by winds in the atmosphere.
K-T Boundary. Image Credit: NASA Earth Observatory
If you look in the fossil record all over the world, you will see a layer that is known as the “K-T Boundary”, referring to the boundary between the Cretaceous and Tertiary periods in geologic history. This layer, says the University of California, Berkeley, is made up of “glassy spheres or tektites, shocked quartz and a layer of iridium-enriched dust.”
Of note, iridium is a rare element on the surface of the Earth, but it’s fairly common in meteorites. (Some argue that the iridium could have come from volcanic eruptions churning it up from inside the Earth; for more information, see this Universe Today story.)
Was it simply ‘the last straw’?
While an asteroid (or comet) striking the Earth could certainly cause all the catastrophic events listed above, some scientists believe the dinosaurs were already on their last legs (so to speak) before the impact took place. Berkeley points to “dramatic climate variation” in the million years preceding the event, such as very cold periods in the tropical environment that the dinosaurs were used to.
Impactors strike during the reign of the dinosaurs (image credit: MasPix/devianart)
What might have caused this were several volcanic eruptions in India around the same time. Some scientists believe it was the volcanic eruptions themselves that caused the extinction and that the impact was not principally to blame, since the eruptions could also have produced the iridium layer. But Berkeley’s Paul Renne said the eruptions were more a catalyst for weakening the dinosaurs.
“These precursory phenomena made the global ecosystem much more sensitive to even relatively small triggers, so that what otherwise might have been a fairly minor effect shifted the ecosystem into a new state,” Renne stated in 2013. “The impact was the coup de grace.”
New images returned by the Planck telescope (right) begin to rival the complexity and beauty of a great artists imagination - Starry Night.A visulization of the Planck data represents the interaction of interstellar dust with the galactic magnetic field. Color defines the intensity of dust emisions and the measurements of polarized light reveals the direction of the magnetic field lines. (Credits: Vincent Van Gogh, ESA)
From the vantage point of a window in an insane asylum, Vincent van Gogh painted one of the most noted and valued artistic works in human history. It was the summer of 1889. With his post-impressionist paint strokes, Starry Night depicts a night sky before sunrise that undulates, flows and is never settled. Scientific discoveries are revealing a Cosmos with such characteristics.
Since Vincent’s time, artists and scientists have taken their respective paths to convey and understand the natural world. The latest released images taken by the European Planck Space Telescope reveals new exquisite details of our Universe that begin to touch upon the paint strokes of the great master and at the same time looks back nearly to the beginning of time. Since Van Gogh – the passage of 125 years – scientists have constructed a progressively intricate and incredible description of the Universe.
New images returned by the Planck telescope (right) begin to rival the complexity and beauty of a great artists imagination – Starry Night.A visulization of the Planck data represents the interaction of interstellar dust with the galactic magnetic field. Color defines the intensity of dust emisions and the measurements of polarized light reveals the direction of the magnetic field lines. (Credits: Vincent Van Gogh, ESA)
The path from Van Gogh to the Planck Telescope imagery is indirect, an abstraction akin to the impressionism of van Gogh’s era. Impressionists in the 1800s showed us that the human mind could interpret and imagine the world beyond the limitations of our five senses. Furthermore, optics since the time of Galileo had begun to extend the capability of our senses.
A photograph of James Clerk Maxwell and a self-portrait of Vincent van Gogh. Maxwell’s equations and impressionism in the fine arts in the 19th Century sparked an enhanced perception, expression and abstraction of the World and began a trek of knowledge and technology into the modern era. (Credit: National Gallery of Art, Public Domain)
Mathematics is perhaps the greatest form of abstraction of our vision of the World, the Cosmos. The path of science from the era of van Gogh began with his contemporary, James Clerk Maxwell who owes inspiration from the experimentalist Michael Faraday. The Maxwell equations mathematically define the nature of electricity and magnetism. Since Maxwell, electricity, magnetism and light have been intertwined. His equations are now a derivative of a more universal equation – the Standard Model of the Universe. The accompanying Universe Today article by Ramin Skibba describes in more detail the new findings by Planck Mission scientists and its impact on the Standard Model.
The work of Maxwell and experimentalists such as Faraday, Michelson and Morley built an overwhelming body of knowledge upon which Albert Einstein was able to write his papers of 1905, his miracle year (Annus mirabilis). His theories of the Universe have been interpreted, verified time and again and lead directly to the Universe studied by scientists employing the Planck Telescope.
The first Solvay Conference in 1911 was organized by Max Planck and Hendrik Lorentz. Planck is standing, second from left. The first Solvay, by invitation only, included most of the greatest scientists of the early 20th Century. While Planck is known for his work on quanta, the groundwork for quantum theory – the Universe in minutiae , the Planck telescope is surveying the Universe in the large. Physicists are closer to unifying the nature of the two extremes. Insets – Planck (1933, 1901).
In 1908, the German physicist Max Planck, for whom the ESA telescope is named, recognized the importance of Einstein’s work and finally invited him to Berlin and away from the obscurity of a patent office in Bern, Switzerland.
As Einstein spent a decade to complete his greatest work, the General Theory of Relativity, astronomers began to apply more powerful tools to their trade. Edwin Hubble, born in the year van Gogh painted Starry Night, began to observe the night sky with the most powerful telescope in the World, the Mt Wilson 100 inch Hooker Telescope. In the 1920s, Hubble discovered that the Milky Way was not the whole Universe but rather an island universe, one amongst billions of galaxies. His observations revealed that the Milky Way was a spiral galaxy of a form similar to neighboring galaxies, for example, M31, the Andromeda Galaxy.
Pablo Picasso and Albert Einstein were human wrecking balls in their respective professions. What began with Faraday and Maxwell, van Gogh and Gaugin were taken to new heights. We are encapsulated in the technology derived from these masters but are able to break free of the confinement technology can impose through the expression and art of Picasso and his contemporaries.
Einstein’s equations and Picasso’s abstraction created another rush of discovery and expressionism that propel us for another 50 years. Their influence continues to impact our lives today.
The Andromeda Galaxy, M31, the nearest spiral galaxy to the Milky Way, several times the angular size of the Moon. First photographed by Isaac Roberts, 1899 (inset), spirals are a function of gravity and the propagation of shock waves, across the expanses of such galaxies are electromagnetic fields such as reported by Planck mission scientists.
Telescopes of Hubble’s era reached their peak with the Palomar 200 inch telescope, four times the light gathering power of Mount Wilson’s. Astronomy had to await the development of modern electronics. Improvements in photographic techniques would pale in comparison to what was to come.
The development of electronics was accelerated by the pressures placed upon opposing forces during World War II. Karl Jansky developed radio astronomy in the 1930s which benefited from research that followed during the war years. Jansky detected the radio signature of the Milky Way. As Maxwell and others imagined, astronomy began to expand beyond just visible light – into the infrared and radio waves. Discovery of the Cosmic Microwave Background (CMB) in 1964 by Arno Penzias and Robert Wilson is arguably the greatest discovery from observations in the radio wave (and microwave) region of the electromagnetic spectrum.
From 1937 to the present day, radio astronomy has been an ever refining merger of electronics and optics. Karl Jansky’s first radio telescope, 1937 (inset) and the great ALMA array now in operation studying the Universe in the microwave region of the electromagnetic spectrum. (Credits: ESO)
Analog electronics could augment photographic studies. Vacuum tubes led to photo-multiplier tubes that could count photons and measure more accurately the dynamics of stars and the spectral imagery of planets, nebulas and whole galaxies. Then in the 1947, three physicists at Bell Labs , John Bardeen, Walter Brattain, and William Shockley created the transistor that continues to transform the World today.
For astronomy and our image of the Universe, it meant more acute imagery of the Universe and imagery spanning across the whole electromagnetic spectrum. Infrared Astronomy developed slowly beginning in the 1800s but it was solid state electronics in the 1960s when it came of age. Microwave or Millimeter Radio Astronomy required a marriage of radio astronomy and solid state electronics. The first practical millimeter wave telescope began operations in 1980 at Kitt Peak Observatory.
An early work of Picasso (center), the work at Bell Labs of John Bardeen, Walter Brattain, and William Shockley and the mobile art of Alexander Calder. As artists attempt to balance color and shape, the Bell Lab engineers balanced electrons essentially on the head of a pin, across junctions to create the first transistor.
With further improvements in solid state electronics and development of extremely accurate timing devices and development of low-temperature solid state electronics, astronomy has reached the present day. With modern rocketry, sensitive devices such as the Hubble and Planck Space Telescopes have been lofted into orbit and above the opaque atmosphere surrounding the Earth.
In 1964, the Cosmic Microwave Background (CMB) was discovered. In the early 1990s, the COBE space telescope returned even more detailed results and now Planck has refined and expanded upon IRAS, COBE and BICEP observations of the CMB. Inset, first light observations of the Planck mission. (Photo Credits: ESA)
Astronomers and physicists now probe the Universe across the whole electromagnetic spectrum generating terabytes of data and abstractions of the raw data allow us to look out into the Universe with effectively a sixth sense, that which is given to us by 21st century technology. What a remarkable coincidence that the observations of our best telescopes peering through hundreds of thousands of light years, even more so, back 13.8 billion years to the beginning of time, reveal images of the Universe that are not unlike the brilliant and beautiful paintings of a human with a mind that gave him no choice but to see the world differently.
Now 125 years later, this sixth sense forces us to see the World in a similar light. Peer up into the sky and you can imagine the planetary systems revolving around nearly every star, swirling clouds of spiral galaxies, one even larger in the sky than our Moon, and waves of magnetic fields everywhere across the starry night.
Artist's conception of asteroids and a gas giant planet. Credit: Harvard-Smithsonian Center for Astrophysics
At first glance, looking at a bunch of space rocks doesn’t sound that exciting. Like, aren’t they just a bunch of rubble? What use can they be in understanding the Solar System compared to looking at planets or moons?
Turns out that asteroids are key to figuring out how the Solar System came to be, and that they’re more interesting than they appear at first glance. Below, we have 10 facts about asteroids that will make you reconsider that biased first impression.
Asteroids are leftovers of the early Solar System.
The leading theory about how our neighborhood came to be is this: the Sun coalesced from a compressed grouping of gas that eventually began fusing atoms and creating a protostar. Meanwhile, the dust and debris nearby the Sun began to coalesce. Small grains became small rocks, which crashed into each other to form bigger ones. The survivors of this chaotic period are the planets and the moons that we see today … as well as a few smaller bodies. By studying asteroids, for example, we get a sense of what the Solar System used to look like billions of years ago.
This image shows the Themis Main Belt which sits between Mars and Jupiter. Asteroid 24 Themis, one of the largest Main Belt asteroids, was examined by University of Tennessee scientist, Josh Emery, who found water ice and organic material on the asteroid’s surface. His findings were published in the April 2010 issue of Nature. Credit: Josh Emery/University of Tennessee, Knoxville
Most asteroids are in a “belt”.
While there are asteroids all over the Solar System, there’s a huge collection of them between the orbits of Mars and Jupiter. Some astronomers think that could have formed into a planet if Jupiter was not nearby. By the way, this “belt” may erroneously create the impression that it is chock full of asteroids and require some fancy Millennium Falcon-style maneuvering, but in reality there are usually hundreds or thousands of miles in between individual asteroids. This shows the Solar System is a big place.
Asteroids are made of different things.
In general, an asteroid’s composition is determined by how close it is to the Sun. Our nearby star’s pressure and heat tends to melt ice that is close by and to blow out elements that are lighter. There are many kinds of asteroids, but these are the three main types, according to NASA:
Dark C (carbonaceous) asteroids, which make up most asteroids and are in the outer belt. They’re believed to be close to the Sun’s composition, with little hydrogen or helium or other “volatile” elements.
Bright S (silicaceous) asteroids and are in the inner belt. They tend to be metallic iron with some silicates of iron and magnesium.
Bright M (metallic) asteroids. They sit in the middle of the asteroid belt and are mostly made up of metallic iron.
Illustration of small asteroids passing near Earth. Credit: ESA / P. Carril
Asteroids also lurk near planets.
NASA also has classifications for this asteroid type. Trojans stay in the same orbit as a planet, but they “hover” in a special spot known as a Lagrangian point that balances the pull of the planet’s gravity and the pull of the Sun. Trojans near Mars, Jupiter and Neptune have been discovered — as well as at least one near Earth in 2011. We also have near-Earth asteroids, which cross our orbit and could (statistically speaking) one day pose a threat to our planet. That said, no one has yet identified any one asteroid that will one day collide with our planet for sure.
Asteroids have moons.
While we think of moons as something that orbits a planet, asteroids also have smaller bodies that orbit them! The first known one was Dactyl, which was discovered in 1993 to be orbiting a larger asteroid called Ida. More than 150 asteroids are known to have moons, with more being discovered periodically. A more recent example is one discovered orbiting Asteroid 2004 BL86, which passed 750,000 miles (1.2 million kilometers) from Earth in early 2015.
Another set of images of 2004 BL86 and its moon. Credit: NAIC Observatory / Arecibo Observatory
We have flown by, orbited and even landed on asteroids. NASA says there are more than 10 spacecraft that accomplished at least one of these, so we’ll just cover a couple of examples here. NEAR Shoemaker touched down and survived for weeks on 433 Eros in 2001 despite not being designed to do it. NASA’s Dawn spacecraft spent months orbiting Vesta — the second-largest member of the asteroid belt — in 2011 and 2012. And in 2010, Japan’s Hayabusa spacecraft made an astonishing return to Earth bearing samples of asteroid Itokawa that it nabbed in 2005.
Asteroids are too small to support life as we know it. That’s because they’re too tiny to even hold on to atmospheres. Their gravity is too weak to pull their shape into a circle, so they’re irregularly shaped. To get a sense of just how small they are in aggregate, NASA says the mass of all the asteroids in the Solar System is less than our Moon — which only has a tenuous “exosphere” itself.
Impactors strike during the reign of the dinosaurs (image credit: MasPix/devianart)
Despite their small size, water may flow on asteroid surfaces. Observations of Vesta released in 2015 show gullies that may have been carved by water. The theory is that when a smaller asteroid slams into a bigger one, the small asteroid releases a layer of ice in the bigger asteroid it hit. The force of the impact briefly turned the ice into water, which streaked across the surface. (As for how the ice got there in the first place, it’s possible that comets deposited it in some way — but that’s still being investigated as well.)
An asteroid could have killed the dinosaurs. The fossil record for dinosaurs and other creatures of their era show them rapidly disappearing around 65 million or 66 million years ago. According to National Geographic, there are two hypotheses for this event: an asteroid or comet hitting the Earth, or a huge volcano eruption. The case for an asteroid comes from a layer of iridium (a rare element on Earth, but not in meteorites) that is found all over the world, and a crater called Chicxulub in Mexico’s Yucatan Peninsula that is about 65 million years old. Iridium, however, is also found inside the Earth, which lends credence to some theories that it was volcanoes instead. In either case, the resulting debris blocked the Sun and eventually starved those survivors of the impact.
At least one asteroid has rings. Called Chariklo, scientists made the surprise discovery in 2013 when they watched it pass in front of a star. The asteroid made the background star “blink” a few times, which led to the discovery that two rings are surrounding the asteroid.
Planck view of BICEP2 field. Credit: ESA/Planck Collaboration. Acknowledgment: M.-A. Miville-Deschênes, CNRS – Institut d'Astrophysique Spatiale, Université Paris-XI, Orsay, France.
Last March, international researchers from the Background Imaging of Cosmic Extragalactic Polarization (BICEP2) telescope at the South Pole claimed that they detected primordial “B-mode” polarization of the cosmic microwave background (CMB) radiation. If confirmed, this would have been an incredibly important discovery for astrophysics, as it would constitute evidence of gravitational waves due to cosmic inflation in the first moments of the universe. Nevertheless, as often happens in science, the situation turns out to be more complicated than it initially appeared.
In a joint analysis of data from BICEP2/Keck Array in the South Pole and the space-based Planck telescope, scientists from both collaborations now have a more complete picture and argue that the interpretation of the evidence is muddier than they had previously thought. Their paper will appear in the arXiv pre-print server in a few days and is submitted for publication in the journal Physical Review Letters. [Update: the paper is now available on the arXiv.] The European Space Agency issued a press release about the paper on Friday after a summary of it was leaked and briefly posted on a French website.
Courtesy: Jet Propulsion Laboratory
According to inflationary theory, the universe expanded for a brief period at an exponential rate 10-36 seconds after the Big Bang. As a result, models of inflation predict that this rapid acceleration would create ripples in space, generating gravitational waves that would remain energetic enough to leave an imprint on the last-scattered photons, the CMB radiation, approximately 380,000 years later. The CMB spectrum, the “afterglow of the hot Big Bang,” has rich structure in it and has been measured to a “ridiculous level of precision,” according to Professor Martin White (University of California, Berkeley), who gave a plenary talk on cosmology results from Planck at the recent American Astronomical Society meeting.
The twists in the polarization signal of the CMB, known as B-modes (shown below) and quantified by a nonzero tensor-to-scalar ratio r, would be evidence in favor of inflation but they are much more difficult to detect. Scientists are trying to decipher a signal on the level of parts per trillion of ambient temperature, mere fractions of a nano-degree! Since inflation would explain why the universe appears to have no overall curvature, why it approximately appears the same in all directions, and why it has structures of galaxies in it, BICEP2’s result last year—the first claimed detection of cosmic inflation—excited physicists around the world. But last summer, Planck scientists presented a map of polarized light from interstellar dust grains and argued that the polarization signal BICEP2 detected could be due to “foreground” dust in our own Milky Way galaxy rather than due to primordial gravitational waves in the distant universe. The hotly debated controversy remained unresolved and led to the new joint analysis by scientists from both teams.
Courtesy: BICEP2
BICEP2 is sensitive to low frequencies (150 GHz) while Planck is more sensitive to higher ones (353 GHz). As Professor Brian Keating (University of California, San Diego), a member of the BICEP2 collaboration, puts it, “it’s as if you’re listening to an opera, but BICEP2 could only hear the tenors and Planck could only hear the sopranos.” Unfortunately, the joint analysis produced only an upper limit to the value of r, meaning that the evidence for B-mode polarization due to inflation remains elusive for now. “It’s probably at best an admixture of Milky Way dust and gravitational waves,” says Keating. [Full disclosure: until last year, Ramin Skibba was a research scientist in the same department but in a different field as Keating at UC San Diego.]
This result must seem disappointing to BICEP2 scientists, but science often works this way, especially for such a difficult phenomenon to study. The signal is strong, but the interpretation is more complicated than it first appeared. On a positive note, the analysis shows that CMB researchers are faced with a foreground challenge rather than one due to the Earth’s atmosphere or to their detectors.
Illustration by Andy Freeberg, SLAC / South Pole Telescope photo by Keith Vanderlinde
Although Planck will have additional polarization measurements and more assessments of systematic uncertainties in a later data release, they will not be able to settle this debate for now. But new experiments will come online soon, including a BICEP3, and they will produce more precise measurements that could effectively remove the contribution from dust. The signal is tractable, and scientists are looking forward to the day when they can declare with strong statistical significance that they have finally discovered evidence of inflation.
Individual radar images of 2004 BL86 and its moon. The asteroid appears very lumpy, possibly from unresolved crater rims. The moon appears elongated but that may be an artifact and not its true shape. Credit: NASA
New video of 2004 BL86 and its moon
Newly processed images of asteroid 2004 BL86 made during its brush with Earth Monday night reveal fresh details of its lumpy surface and orbiting moon. We’ve learned from both optical and radar data that Alpha, the main body, spins once every 2.6 hours. Beta (the moon) spins more slowly.
The images were made by bouncing radio waves off the surface of the bodies using NASA’s 230-foot-wide (70-meter) Deep Space Network antenna at Goldstone, Calif. Radar “pinging” reveals information about the shape, velocity, rotation rate and surface features of close-approaching asteroids. But the resulting images can be confusing to interpret. Why? Because they’re not really photos as we know it.
For one, the moon appears to be revolving perpendicular to the main body which would be very unusual. Most moons orbit their primary approximately in the plane of its equator like Earth’s moon and Jupiter’s four Galilean moons. That’s almost certainly the case with Beta. Radar imagery is assembled from echoes or radio signals returned from the asteroid after bouncing off its surface. Unlike an optical image, we see the asteroid by reflected pulses of radio energy beamed from the antenna. To interpret them, we’ll need to put on our radar glasses.
Bright areas don’t necessarily appear bright to the eye because radar sees the world differently. Metallic asteroids appear much brighter than stony types; rougher surfaces also look brighter than smooth ones. In a sense these aren’t pictures at all but graphs of the radar pulse’s time delay, Doppler shift and intensity that have been converted into an image.
Another set of images of 2004 BL86 and its moon. Credit: NAIC Observatory / Arecibo Observatory
In the images above, the left to right direction or x-axis in the photo plots the toward and away motion or Doppler shift of the asteroid. You’ll recall that light from an object approaching Earth gets bunched up into shorter wavelengths or blue-shifted compared to red-shifted light given off by an object moving away from Earth. A more rapidly rotating object will appear larger than one spinning slowly. The moon appears elongated probably because it’s rotating more slowly than the Alpha primary.
Meanwhile, the up and down direction or y-axis in the images shows the time delay in the reflected radar pulse on its return trip to the transmitter. Movement up and down indicates a change in 2004 BL86’s distance from the transmitter, and movement left to right indicates rotation. Brightness variations depend on the strength of the returned signal with more radar-reflective areas appearing brighter. The moon appears quite bright because – assuming it’s rotating more slowly – the total signal strength is concentrated in one small area compared to being spread out by the faster-spinning main body.
If that’s not enough to wrap your brain around, consider that any particular point in the image maps to multiple points on the real asteroid. That means no matter how oddly shaped 2004 BL86 is in real life, it appears round or oval in radar images. Only multiple observations over time can help us learn the true shape of the asteroid.
You’ll often notice that radar images of asteroids appear to be lighted from directly above or below. The brighter edge indicates the radar pulse is returning from the leading edge of the object, the region closest to the dish. The further down you go in the image, the farther away that part of the asteroid is from the radar and the darker it appears.
Imagine for a moment an asteroid that’s either not rotating or rotating with one of its poles pointed exactly toward Earth. In radar images it would appear as a vertical line!
If you’re curious to learn more about the nature of radar images, here are two great resources:
There’s darkness out there in the cold corners of the solar system.
And we’re not talking about a Lovecraftian darkness, the kind that would summon Cthulhu himself. We’re talking of celestial bodies that are, well. So black, they make a Spinal Tap album cover blinding by comparison.
We recently came across the above true color comparison of Comet 67/P Churyumov-Gerasimenko adjusted for true reflectivity contrasted with other bodies in the solar system. 67/P is definitely in the “none more black” (to quote Nigel Tufnel) category as compared to, well, nearly everything.
Welcome to the wonderful world of albedo. Bob King wrote a great article last year discussing the albedo of Comet 67/P. The true albedo (or lack thereof) of 67/P as revealed by Rosetta’s NAVCAM continues to astound us. Are all comets this black close up? After all, we’re talking about those same brilliant celestial wonders that can sometimes be seen in the daytime, and are the crimson harbingers of regal change in The Game of Thrones, right?
There was also a great discussion of the dark realms of 67/P in a recent SETI Talk:
As with many things in the universe, it’s all a matter of perspective. If you live in the U.S. Northeast and are busy like we were earlier today digging yourself out from Snowmageddon 2015, then you were enjoying a planetary surface with a high albedo much more akin to Enceladus pictured above. Except, of course, you’d be shoveling methane and carbon dioxide-laced snow on the Saturnian moon… Ice, snow and cloud cover can make a world shinny white and highly reflective. Earthshine on the dark limb of the crescent Moon can even vary markedly depending on the amount of cloud and snow cover on the Earth that’s currently rotated moonward.
A brilliant Earthshine, or the ‘Old Moon in the New Moon’s arms’ from earlier last week. Photo by author.
To confound this, apparent magnitude over an extended object is diffused over its surface area, making the coma of a comet or a nebula appear fainter than it actually is. Engineers preparing for planetary encounters must account for changes in light conditions, or their cameras may just record… nothing.
For example, out by Pluto, Charon, and friends, the Sun is only 1/1600th as bright as seen here on sunny Earth. NASA’s New Horizons spacecraft will have to adjust for the low light levels accordingly during its historic flyby this July. On the plus side, Pluto seems to have a respectable albedo of 50% to 65%, and may well turn out to look like Neptune’s large moon, Triton.
Triton as imaged by Voyager 2: a dead ringer for Pluto? Credit: NASA/JPL.
And albedo has a role in heat absorption and reflection as well, in a phenomenon known as global dimming. The ivory snows of Enceladus have an albedo of over 95%, while gloomy Comet 67/P has an albedo of about 5%, less than that of flat black paint. A common practice here in Aroostook County Maine is to take fireplace ashes and scatter them across an icy driveway. What you’re doing is simply lowering the surface albedo and increasing the absorption of solar energy to help break up the snow and ice on a sunny day.
A high albedo snow cover blanketed New England earlier this week! Photo by author.
Ever manage to see Venus in the daytime? We like to point out the Cytherean world in the daytime sky to folks whenever possible, often using the nearby Moon as a guide. Most folks are amazed at how easy this daytime feat of visual athletics actually is, owing to the fact that the cloud tops of Venus actually have a higher albedo of 90%, versus the Moon’s murky 8 to 12%.
Venus (upper left) by daylight. Photo by author.
Apollo 12 command module pilot Richard Gordon remarked that astronauts Al Bean and Pete Conrad looked like they’d been “playing in a coal bin” on returning from the surface of the Moon. And in case you’re wondering, Apollo astronauts reported that moondust smelled like ‘burnt gunpowder’ once they’d unsuited.
The surface of the Moon closeup: darker than you think! Credit: Apollo 12/NASA.
Magnitude, global dimming and planetary albedo may even play a role in SETI as well, as we begin to image Earthlike exoplanets… will our first detection of ET be the glow of their cities on the nightside of their homeworld? Does light pollution pervade the cosmos?
And a grey cosmos awaits interstellar explorers as well. Forget Captain Kirk chasing Khan through a splashy, multi-hued nebula: most are of the light grey to faded green varieties close up. Through a telescope, most nebulae are devoid of color. It’s only when a long time exposure is completed that colors too faint to see with the naked eye emerge.
All strange thoughts to consider as we scout out the dark corners of the solar system. Will the Philae lander reawaken as perihelion for Comet 67/P approaches on August 13th, 2015? Will astronauts someday have to navigate over the dark surface of a comet?
I can’t help but think as I look at the duck-like structure of 67/P that one day, those two great lobes will probably separate in a grand outburst of activity. Heck, Comet 17P/Holmes is undergoing just such an outburst now — one of the best it has generated since 2007 — though it’s still below +10th magnitude. How I’d love to get a look at Comet 17P/Holmes up close, and see just what’s going on!
Toes of a pahoehoe flow advance across a road in Kalapana on the east rift zone of Kilauea Volcano, Hawaii and the binary asteroid 2004 BL86. Credit: U.S. Geological Survey (left) and NASA/JPL-Caltech
At first glance, you wouldn’t think Hawaii has any connection at all with asteroid 2004 BL86, the one that missed Earth by 750,000 miles (1.2 million km) just 3 days ago. One’s a tropical paradise with nightly pig roasts, beaches and shave ice; the other an uninhabitable ball of bare rock untouched by floral print swimsuits.
But Planetary Science Institute researchers Vishnu Reddy and Driss Takir would beg to differ.
Using NASA’sInfrared Telescope Facility on Mauna Kea, Hawaii they discovered that the speedy “space mountain” has a composition similar to the very island from which they made their observations – basalt.
“Our observations show that this asteroid has a spectrum similar to V-type asteroids,” said Reddy. “V-type asteroids are basalt, similar in composition to lava flows we see in Hawaii.
Minerals on the surface of an object like the moon or an asteroid absorb wavelengths of light to create a series of “blank spaces” or absorption lines that are unique to a particular element or compound. Credit: NASA
The researchers used a spectrograph to study infrared sunlight reflected from 2004 BL86 during the flyby. A spectrograph splits light into its component colors like the deli guy slicing up a nice salami. Among the colors are occasional empty spaces or what astronomers call absorption lines, where minerals such as olivine, pyroxene and plagioclase on the asteroid’s surface have removed or absorbed particular slices of sunlight.
You’re looking straight down into the 310-mile-wide (500 km) Rheasilvea crater / impact basin on the asteroid Vesta. It’s though that many of the Vesta-like asteroids, including 2004 BL86, originated from the impact. It Credit: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA
These are the same materials that not only compose earthly basalts – all that dark volcanic rock that underlies Hawaii’s reefs and resorts – but also Vesta, considered the source of V-type asteroids. It’s thought that the impact that hollowed out the vast Rheasilvia crater at Vesta’s south pole blasted chunks of mama asteroid into space to create a family of smaller siblings called vestoids.
This animation, created from individual radar images, shows the binary asteroid 2004 BL86 on January 26th. The moon’s orbital period is about 13.8 hours. Credit: NASA/JPL-Caltech
So it would appear that 2004 BL86 could be a long-lost daughter born through impact and released into space to later be perturbed by Jupiter into an orbit that periodically brings it near Earth. Close enough to watch in wonder as it inches across the field of view of our telescopes like it did earlier this week.
The little moonlet may or may not be related to Vesta, but its presence makes 2004 BL86 a binary asteroid, where each object revolves about their common center of gravity. While the asteroid is unlikely to become future vacation destination, there will always be Hawaii to satisfy our longings for basalt.
