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There may actually be a ninth planet in our solar system after all. Astronomers at Caltech recently presented evidence for a large, gas-giant, planet in a 20,000 year orbit around our sun. They have been quoted as saying, "We have felt a great disturbance in the force." This only adds to the crazy nature of this announcement; but they were not referring to Luke Skywalker's famed Force, but rather the gravitational force that keeps all of the planets and dwarf planets in motion around our sun. Their research suggests that the existence of such a planet, in this large elliptical orbit, is one of the best explanations for the measured orbits of the dwarf planets in the Kuiper Belt. Their argument is presented in an enlightening YouTube video and one of the scientists has been interviewed by CBC's Bob McDonald on the program "Quirks and Quarks." The mass of the planet is said to be greater than that of Earth but less than the mass of Neptune and it is perpetually "very distant" in the solar system. It has not yet been seen with a telescope; but is inferred from its interaction with the features of the Kuiper Belt.
What are the implications of such a discovery? Where should we point our telescopes to begin to look for this planet? There are certain constraints on where this planet could be, but that still leaves a large area to be scanned. The current position in its orbit will be unknown until it can be visualized. This research also invites questions related to the planet’s proximity to other planets in our solar system. What perturbations (dare I say, “disturbances in the force”) will be noted when this planet swings by after a long journey away from the other planets and dwarf planets in our solar system? Might it have noticeable effects on the physics, chemistry, and biology of Earth? Gravity is a relatively weak force but its influence acts over very large distances.
For now, I congratulate Mike Brown and Konstantin Batygin and other contributing researchers for their work in this area. May they inspire many more “planet-hunters.” | 0.867837 | 3.142559 |
Astronomers have spotted a star dancing around a massive black hole in the middle of the Milky Way galaxy — and they said it proves Einstein was right.
The star is the first ever caught circling the enormous black hole in the middle of our galaxy, scientists said.
It was tracked through the massive European Southern Observatory in the Chilean desert — and its orbit is shaped like a rosette as opposed to an ellipse, which is what Isaac Newton’s theory of gravity would suggest, CNN said in a report Thursday.
Instead, the rosette orbit proves that Albert Einstein’s theory of relativity was on the mark, astronomers said.
“Einstein’s general relativity predicts that bound orbits of one object around another are not closed, as in Newtonian gravity, but precess towards in the plane of motion,” Reinhard Genzel, director of the Max Planch Institute for Extraterrestial Physics in Germany, said in a statement, CNN reported.
Scientists first identified the same rosette pattern in Mercury’s orbit around the sun, Genzel said.
Now, the newly observed star dancing around an area in the center of the Milky Way that scientists named “Sagittarius A” “strengthens the evidence” that it is a supermassive black hole with about 4 million times the mass of the sun and 26,000 light-years away.
The star, identified as S2, passes closest to the black hole, within 20 billion kilometers.
While orbits aren’t perfect, the star orbiting the black hole changes its approach with each orbit, creating the rosette pattern, CNN said. Einstein’s theory of relativity predicts how much the orbit changes with each pass.
“If we are lucky, we might capture stars close enough that they actually feel the rotation, the spin, of the black hole,” Andreas Eckart, co-author of the findings and lead scientist at Cologne University in Germany, told the network. “That would be again a completely different level of testing relativity.” | 0.826886 | 3.24927 |
One year ago a mysterious cigar-shaped object dubbed ‘Oumuamua’ raised a lot of eyebrows among astronomers and science enthusiasts alike when it was discovered traveling through our Solar System at blazing speed. Most scientists agreed that the object was just another asteroid or comet, albeit one with an unusually elongated shape. Others, however, suggested that it could be an artificial structure. A structure possibly created by a long-lost alien civilization. Now, a new research paper by Shmuel Bialy and Abraham Loeb from the Harvard Smithsonian Center for Astrophysics is revisiting this possibility and sparking the debate anew.
The paper isn’t so much about alien civilizations as it is about trying to explain some of Oumuamua’s unusual proprieties. Oumuamua is unique not just because of its shape but also because it’s the first interstellar object ever discovered in our Solar System. Another aspect that intrigued the Harvard researchers was its peculiar acceleration as it was traveling away from the Sun and towards the edge of our Solar System. This type of behavior is common among comets, which can accelerate unpredictably when gasses trapped inside them start to expand and evaporate. Asteroids, on the other hand, are completely barren and are propelled solely by gravity.
Researchers Suggest Oumuamua Could be a Lightsail
What’s interesting about Oumuamua is that it seems to be an asteroid but it’s behaving like a comet. However, the Harvard researchers indicate that the object can’t be a comet. Comets leave behind trails (or ‘tails’) as they evaporate and Oumuamua doesn’t have one. So then why does this asteroid-like object accelerate away from the Sun when it shouldn’t be able to? Well, one explanation could be solar radiation pressure. This type of pressure could theoretically push objects away from the Sun and be responsible for Oumuamua’s acceleration. There’s a catch, though: the object would have to be extremely thin.
“For radiation pressure to be effective, the mass-to-area ratio must be very small,” explains the paper. According to NASA, Oumuamua is about half a mile long (around 800 meters). That means the object would have to be millimeter thin in order for this explanation to work. If true, that opens up an interesting possibility.
Those kinds of dimensions and the possibility that it’s propelled by solar radiation would make Oumuamua a lightsail. This is a possibility the Harvard researchers have seriously taken into consideration. “One possibility is that Oumuamua is a lightsail, floating in interstellar space as a debris from an advanced technological equipment,” says Loeb.
The Second Theory Also Points at Aliens
So is Oumuamua just a floating remnant of an alien civilization? Maybe, maybe not but that possibility is certainly intriguing. It’s also not as outlandish as it may sound. Scientists have been working on creating similar lightsails but on a smaller scale for a number of years now. IKAROS and Breakthrough Starshot are just two examples. In other words, a hypothetical alien civilization just one or two decades more advanced than us should be able to pull off a full-scale functional lightsail. That said, the Harvard scientists have yet another theory about Oumuamua that’s a bit more… out there.
“Alternatively, a more exotic scenario is that Oumuamua may be a fully operational probe sent intentionally to Earth vicinity by an alien civilization,” reads the paper. The researchers admit that scenario is very unlikely, but still plausible in theory.
Oumuamua came out of nowhere in 2017 and disappeared from view before scientists were able to properly analyze it. The object already passed Jupiter’s orbit earlier this year and will pass Saturn as well by January 2019 as it rushes towards the edge of our Solar System. Unfortunately, we’re unlikely to observe it again so we may never know its true origins. Was it an alien probe or just a weirdly-shaped asteroid behaving like a comet? Just like the two Harvard researchers, all we can do now is speculate.
Meanwhile, if you’re not a huge fan of speculating and would rather keep an eye on the night skies yourself, we recommend checking out this great comprehensive guide that covers everything you need to know about all the most important astronomical phenomena of 2019. The guide also describes when and where you will be able to catch a good glimpse of our neighboring planets, meteor showers, all the eclipses that will occur throughout the year, and more. | 0.906021 | 3.82022 |
NASA researchers have observed with an infrared telescope that an extremely powerful eruption is about to occur on Io, one of Jupiter's many moons.
Volcano eruption in the land of giants
11 times larger than Earth, Jupiter is undoubtedly one of the biggest planets, with no less than 79 satellites discovered in its orbit. One of them, named 'Io,' is the subject of particular observations because it is about to offer researchers an incredible sight: the eruption of its most massive and powerful volcano.
Io: a volcanic world
If you were to go for a walk on the surface of Io, you would discover a mountainous and inhospitable landscape, as this moon has about 400 volcanoes on its surface and many sulphur lakes. Among all these volcanoes, one seems particularly large and threatening, and NASA has symbolically named it Loki after the Norse god of philosophy. It is the latter who for some time now seems to be showing several signs that it is about to erupt.
The Loki volcano, well known to NASA
In a recent press release, Dr. Julie Rathbun, a researcher at the Planetary Science Institute in Arizona, presented her observations of the volcano from a NASA infrared telescope in Hawaii. The images indicate the presence of repeated light signals suggesting signs of an impending eruption. By observing these variations in light, researchers like Leigh Fletcher will be able to assess Loki's activity:
'For a few hundred days it's going to be pretty dark, not a lot is going to happen. And then, for a few hundred days in a row, the volcano as it becomes active will emit 15 to 20 times as much light'
Having observed Io for a long time, researchers had been able to indicate in the 1990s thatLoki was producing eruptions about every 540 days. But current weekly observations have revealed an unexplained shortening of the intervals, with the volcano erupting on average every 475 days.
It's about to get hot
Remarkably powerful, the eruption of the Loki volcano would be so large that it could represent 15% of the total heat existing on the surface of the moon Io. An event of gigantic proportions that fortunately occurs far away from us, as Julie Rathbun explained:
'There's nothing like it on our planet. If this happened on Earth, it would wipe out all of Southern California.' | 0.876794 | 3.60464 |
The Great Pyramids in Giza, the Parthenon in Athens and Chichen Itza in Mexico have something in common. Besides attracting hordes of tourists, all of these architectural wonders appear to use the golden ratio.
This mathematical number is often written as 1.618, the first few digits of its infinite decimal form. Expressed another way, two quantities —let's call the larger one "a" and the smaller "b" —are in the golden ratio if "a is to b" as "a + b is to a." The result is a composition with aesthetically pleasing proportions.
Now, shapes with the golden ratio, as well as other geometric shapes, have been found in another, unexpected site: the Sun Temple at Mesa Verde National Park in Colorado, built by the ancient Pueblo people who lived in what is now the modern-day Southwest; they had no known written language or written number system. [Chaco Canyon Photos: The Center of an Ancient World]
Sherry Towers, a physicist and statistician at Arizona State University, had been surveying the 800-year-old ruins of the D-shaped temple. She was originally interested in whether this carefully constructed ceremonial temple —which was already thought to be aligned with the solar solstice and lunar standstill (the point at which the moon appears to reverse its path from north to south or south to north) —was also used as an astronomical observatory for people of its time to watch celestial bodies, like the Pleiades and Vega.
"I noticed in my site survey that the same measurements kept popping up over and over again," Towers said in a statement from ASU. "When I saw that the layout of the site's key features also involved many geometrical shapes, I decided to take a closer look."
In the layout of the site, Towers documented rectangles using the golden ratio as well as other geometric shapes such as equilateral triangles, squares, 45-degree right triangles and Pythagorean triangles.
This means that the Sun Temple could represent one of the earliest examples in prehistoric North America of knowledge of several geometrical constructs, Towers wrote in her study, which is detailed in the April issue of the Journal of Archaeological Science: Reports.
"Given that the ancestral Pueblo peoples had no written language or number system, the precision of such a layout would be a remarkable feat," Towers wrote. "It is unclear why these ancients potentially felt the need to employ these constructs in the Sun Temple site. Perhaps the specialized knowledge of how to construct these shapes with a straightedge and a cord formed part of the inherent mysticism of the ceremonial nature of the site."
However the temple was constructed, Towers wrote that the apparent care with which it was designed at least supports the idea that this site was important for ceremonies and rituals in the region. And even with low-tech methods, the measurements of these shapes at the Sun Temple had a relative error of less than 1 percent, she added. The shapes also seem to use a common unit of measurement equal to about 1 modern-day foot (just over 30 centimeters), which is why Towers says she think the shapes aren't just a random chance occurrence in her analysis.
She wants to investigate whether these units and shape are also used at other ancestral Puebloan ceremonial sites, such as Pueblo Bonito, in New Mexico's Chaco Culture National Historical Park.
"Further study is needed to see if that site also has the same common unit of measurement," she said. "It's a task that will keep us busy for some years to come."
Original article on Live Science. | 0.8338 | 3.100227 |
Space Telescope Science
Ten years ago, astronomer John Blakeslee spotted dots of light peppered throughout images of a giant cluster of galaxies, called Abell 1689. Each dot was not one star, but hundreds of thousands of stars crowded together in groupings called globular clusters. Blakeslee counted 500 such clusters, the brightest members of a teeming population of globular clusters.
Now, a new Hubble census of globular clusters in Abell 1689 reveals that an estimated 160,000 such groupings are huddled near the galaxy cluster's core. The Hubble observations break the record for the farthest and the most globular clusters ever seen. Globular clusters are the homesteaders of galaxies, containing some of the oldest surviving stars in the universe. These stellar relics are important to study because they help reveal the story of galaxy formation in the early universe. By comparison, only 150 globular clusters orbit the Milky Way galaxy. | 0.862604 | 3.543743 |
Mercury and Venus Transits
All titles are clickable and link to the original APOD page. Click on an image for a larger view of it.
2006 November 25
Mercury is now visible shortly before dawn, the brightest "star" just above the eastern horizon. But almost two weeks ago Mercury actually crossed the face of the Sun for the second time in the 21st century. Viewed with red/blue glasses, this stereo anaglyph combines space-based images of the Sun and innermost planet in a just-for-fun 3D presentation of the Mercury transit. The solar disk image is from Hinode. (sounds like "hee-no-day", means sunrise). A sun-staring observatory, Hinode was launched from Uchinoura Space Center and viewed the transit from Earth orbit. Superimposed on Mercury's dark silhouette is a detailed image of the planet's rugged surface based on data from the Mariner 10 probe that flew by Mercury in 1974 and 1975.
2006 November 17
The sight of Mercury's tiny round disk drifting slowly across the face of the Sun inspired and entertained many denizens of planet Earth last week. In fact, artist and astronomer Mark Seibold viewed both the 1999 and 2006 transits of the solar system's innermost planet through solar filtered telescopes and composed this rendering of Mercury "hovering in the photosphere" near the edge of an enormous solar disk. The original work is a 23 by 17 inch pastel sketch. While the artist's hand is creatively superimposed, Seibold concentrated on offering an impression of Mercury's silhouette, surrounded by shadings reflecting his visual experience that are not easily captured in photographic exposures. Of course, before the age of cameras drawings were more widely used to record telescopic observations of sunspots and planetary transits.
2006 November 14
What's that dot on the Sun? If you look closely, it is almost perfectly round. The dot is the result of an unusual type of solar eclipse that occurred last week. Usually it is the Earth's Moon that eclipses the Sun. Last week, for the first time in over three years, the planet Mercury took a turn. Like the approach to New Moon before a solar eclipse, the phase of Mercury became a continually thinner crescent as the planet progressed toward an alignment with the Sun. Eventually the phase of Mercury dropped to zero and the dark spot of Mercury crossed our parent star. The situation could technically be labeled a Mercurian annular eclipse with an extraordinarily large ring of fire. From above the cratered planes of the night side of Mercury, the Earth appeared in its fullest phase. Hours later, as Mercury continued in its orbit, a slight crescent phase appeared again. The next Mercurian solar eclipse will occur in 2016.
2006 November 10
Enjoying Wednesday's transit of Mercury from Dallas, Texas, astronomer Phil Jones recorded this detailed image of the Sun. Along with a silhouette of the innermost planet, a network of cells and dark filaments can be seen against a bright solar disk with spicules and prominences along the Sun's edge. The composited image was taken through a telescope equiped with an H-alpha filter that narrowly transmits only the red light from hydrogen atoms. Such images emphasize the solar chromosphere, the region of the Sun's atmosphere immediately above its photosphere or normally visible surface. Left of center, the tiny disk of Mercury seems to be imitating a small sunspot that looks a little too round. But in H-alpha pictures, sunspot regions are usually dominated by bright splotches (called plages) on the solar chromosphere.
2006 November 8
Mercury, the solar system's innermost planet, will spend about five hours crossing in front of the Sun today - beginning at 1912 UT (2:12pm EST), November 8. Specially equipped telescopes are highly recommended to safely spot the planet's diminutive silhouette however, as Mercury should appear about 200 times smaller than the enormous solar disk. This simulated view is based on a filtered solar image recorded on November 3rd. It shows active regions and the Mercury transit across the Sun at six positions from lower left to middle right. Depending on your location, the Sun may not be above the horizon during the entire transit, but webcasts of the event are planned - including one using images from the sun-staring SOHO spacecraft. This is the second of 14 transits of Mercury during the 21st century. The next similar event will be a transit of Venus in June of 2012.
2004 July 20
On June 8, Venus was not the only celestial object to pass in front of the Sun. A few well-situated photographers caught the International Space Station also crossing the Sun simultaneously. Pictured above is a unique time-lapse image of the unprecedented double transit, a rare event that was visible for less than a second from a narrow band on Earth. The above image is a combination of 12 frames taken 0.033 seconds apart and each themselves lasting only 1/10,000 th of a second. The image was taken from the small village of Stupava in Slovakia. The next time Venus will appear to cross the Sun from Earth will be in 2012.
2004 July 17
Venus glides in front of an enormous solar disk in these two frames from the TRACE satellite imaging of the inner planet's 2004 transit. Arranged in a "right/left" stereogram, the frames are intended to be viewed at a comfortable distance from the screen with your eyes gently crossed, allowing the images to merge and produce a pleasing stereo effect. Shown during the ingress (beginning) phase of the transit, the silhouetted portion of the planet appears to float dramatically in front of the Sun's granulated surface. Of course, the dense Cytherian (Venusian) atmosphere also scatters and refracts the intense sunlight. The effect is visible across the portion of the planet still beyond the Sun's edge and viewed against the blackness of space.
2004 June 23
The rare transit of Venus across the face of the Sun earlier this month was one of the better-photographed events in sky history. Both scientific and artistic images have been flooding in from the areas that could see the transit: Europe and much of Asia, Africa, and North America. Scientifically, solar photographers confirmed that the black drop effect is really better related to the viewing clarity of the camera or telescope than the atmosphere of Venus. Artistically, images might be divided into several categories. One type captures the transit in front of a highly detailed Sun. Another category captures a double coincidence such as both Venus and an airplane simultaneously silhouetted, or Venus and the International Space Station in low Earth orbit. A third image type involves a fortuitous arrangement of interesting looking clouds, as shown by example in the above image taken from North Carolina, USA. There the distant orb of giant Venus might have been mistaken, at first glance, for a small but unusually circular cloud.
2004 June 15
An unusual type of solar eclipse occurred last week. Usually it is the Earth's Moon that eclipses the Sun. Last week, for the first time in over 100 years, the planet Venus took a turn. Like a solar eclipse by the Moon, the phase of Venus became a continually thinner crescent as Venus became increasingly better aligned with the Sun. Eventually the alignment became perfect and the phase of Venus dropped to zero. The dark spot of Venus crossed our parent star. The situation could technically be labeled a Venusian annular eclipse with an extraordinarily large ring of fire. From above the thick cloud tops of Venus, the Earth appeared in its fullest phase, brighter in the Venusian sky than even Mars appeared from Earth last August. Hours later, as Venus continued in its orbit, a slight crescent phase appeared again. The next Venusian solar eclipse will occur in 2012.
2004 June 11
Enjoying the 2004 Transit of Venus from Stuttgart, Germany, astronomer Stefan Seip recorded this fascinating, detailed image of the Sun. Revealing a network of cells and dark filaments against a bright solar disk with spicules and prominences along the Sun's limb, his telescopic picture was taken through an H-alpha filter. The filter narrowly transmits only the red light from hydrogen atoms and emphasizes the solar chromosphere -- the region of the Sun's atmosphere immediately above its photosphere or normally visible surface. Here, the dark disk of Venus seems to be imitating a giant sunspot that looks perhaps a little too round. But in H-alpha pictures like this one, sunspot regions are usually dominated by bright splotches (called plages) on the solar chromosphere.
2004 June 10
With Venus in transit at the Sun's edge on June 8th, astronomers captured this tantalizing close-up view of the bright solar surface and partially silhouetted disk. Enhanced in the sharp picture, a delicate arc of sunlight refracted through the Venusian atmosphere is also visible outlining the planet's edge against the blackness of space. The arc is part of a luminous ring or atmospheric aureole, first noted and offered as evidence that Venus did posses an atmosphere following observations of the planet's 1761 transit. The image was recorded using the 1-meter Swedish Solar Telescope located on La Palma in the Canary Islands. For the Institute for Solar Physics, Dan Kiselman, Goran Scharmer, Kai Langhans, and Peter Dettori were at the telescope, while Mats Lofdahl produced the final image. Excellent movies of the transit - including one of the emergence of Venus' atmospheric aureole - are available from the Dutch Open Telescope, also observing from La Palma.
2004 June 9
Did you see the transit? While some watched by webcast, sky gazers in Europe, the Middle East, Africa, and Asia were able to witness the complete 6 hour journey of Venus' silhouetted disk across the face of the Sun. As seen from North America, the much heralded Venus Transit of 2004 was nearing its final stages at sunrise yesterday in this telescopic image. The view looks across the Atlantic from Tybee Island near Savannah, Georgia, USA. In fact, many in eastern North America experienced a dramatic view of a perfect, dark, round Venus against a reddened Sun filtered by banks of low clouds. Ironically, the Sun takes on the appearance of a cloud covered planet itself as Venus marches toward the right through this dreamlike scene.
2004 June 8
Today an astronomical event will occur that no living person has ever seen: Venus will cross directly in front of the Sun. A Venus crossing, called a transit, last occurred in 1882 and was front-page news around the world. Today's transit will be visible in its entirety throughout Europe and most of Asia and Africa. The northeastern half of North America will see the Sun rise with the dark dot of Venus already superposed. Never look directly at the Sun, even when Venus is in front. Mercury's closer proximity to the Sun cause it to transit every few years. In fact, the above image mosaic of Mercury crossing the Sun is from two transits ago, in November 1999. Will anyone living see the next Venus transit? Surely yes since it occurs in 2012.
2003 May 27
Earlier this month, the planet Mercury crossed the face of the Sun, as seen from Earth. Because the plane of Mercury's orbit is not exactly coincident with the plane of Earth's orbit, Mercury usually appears to pass over or under the Sun. The above time-lapse sequence, superimposed on a single frame, was taken from a balcony in Belgium on May 7 and shows the entire transit. The solar crossing lasted over five hours, so that the above 23 images were taken roughly 15 minutes apart. The north pole of the Sun, the Earth, Mercury's orbit, although all different, all occur in directions slightly above the left of the image. Near the center and on the far right, sunspots are visible.
2003 May 13
How big is the Sun? The Sun is not only larger than any planet, it is larger than all of the planets put together. The Sun accounts for about 99.9 percent of all the mass in its Solar System. Merely stating the Sun's diameter is about 1,400,000 kilometers does not do it justice. Last week a chance to gain visual size perspective occurred when planet Mercury made a rare crossing in front to Sun. Mercury, a planet over a third of the diameter of our Earth, is the dark dot on the upper right. In comparison to the Sun, Mercury is so small it is initially hard to spot. Also visible on the Sun are dark circular sunspots, bright plages, and dark elongated prominences -- many of which are larger than Mercury. The above contrast-enhanced picture was captured last week from France.
2003 May 8
Can you spot the planet? The diminutive disk of Mercury, the solar system's innermost planet, spent about five hours crossing in front of the enormous solar disk yesterday (Wednesday, May 7th), as viewed from the general vicinity of planet Earth. The Sun was above the horizon during the entire transit for observers in Europe, Africa, Asia, or Australia, and the horizon was certainly no problem for the sun-staring SOHO spacecraft. Seen as a dark spot, Mercury progresses from left to right (top panel to bottom) in these four images from SOHO's extreme ultraviolet camera. The panels' false-colors correspond to different wavelengths in the extreme ultraviolet which highlight regions above the Sun's visible surface. This is the first of 14 transits of Mercury which will occur during the 21st century, but the next similar event will be a transit of Venus in June of 2004. Need help spotting Mercury? Just click on the picture.
December 10, 1999
OK, it's a picture of the Sun (duh!), but can you spot the planet? Of course, most of the spots you've spotted are sunspots, as large or larger than planet Earth itself. The sunspots are regions of strong surface magnetic fields which are dark in this picture only because they are relatively cool compared to their surroundings. Over the past few years, the number of sunspots has been steadily increasing as the Sun approaches the maximum in its 11 year activity cycle. But also visible in this photograph from November 15, is planet Mercury. At just over 1/3 Earth's size, Mercury is passing in front of the Sun, its silhouette briefly creating a diminutive dark spot drifting across an enormous solar disk. While "transits" of Mercury do occur 13 times a century, this one was additionally a very rare grazing transit of our Solar System's innermost planet. Spotted Mercury yet? Click on the picture for a hint.
November 19, 1999
Just days before the peak of the Leonid meteor shower, skywatchers were offered another astronomical treat as planet Mercury crossed the face of the Sun on November 15. Viewed from planet Earth, a transit of Mercury is not all that rare. The last occurred in 1993 and the next will happen in 2003. Enjoying a mercurial transit does require an appropriately filtered telescope, still the event can be dramatic as the diminutive well-done world drifts past the dominating solar disk. This slow loading gif animation is based on images recorded by the earth-orbiting TRACE satellite. The false-color TRACE images were made in ultraviolet light and tend to show the hot gas just above the Sun's visible surface. Mercury's disk is silhouetted against the seething plasma as it follows a trajectory near the edge of the Sun.
July 2, 1998
This sequence of false color X-ray images captures a rare event - the passage or transit of planet Mercury in front of the Sun. Mercury's small disk is silhouetted against the bright background of X-rays from the hot Solar Corona. It appears just to the right of center in the top frame and moves farther right as the sequence progresses toward the bottom. The dark notch is a coronal hole near the Solar South Pole, while a flaring coronal bright point can be seen to the left of the notch in the top frames. The frames were recorded on November 6, 1993 by the Soft X-ray Telescope on board the orbiting Yohkoh satellite. Transits of Mercury (and Venus) were historically used to discover the geometry of the solar system and to map planet Earth itself. | 0.832972 | 3.232679 |
(TMU) — A comet that hasn’t visited our solar system in about 5,500 years will become visible to the naked eye later this month, gracing skies in the northern hemisphere.
It is believed that the bright comet’s visit to our neighborhood may coincide with the coronavirus pandemic reaching its peak, reports Forbes.
Astronomers discovered Comet C-2019-Y4 (ATLAS)—or Comet Atlas, for short—while working at the Asteroid Terrestrial-impact Last Alert System (Atlas) project in Hawaii.
The comet will be at its brightest at the end of April/beginning of May. Use this sky chart to see where Comet Atlas is now and find it yourself with a telescope. If we’re lucky, Comet Atlas will be visible with binoculars or the naked eye on or around April 30. According to health.com, the Institute for Health Metrics and Evaluation (IHME) estimates the coronavirus pandemic will reach its peak in mid to late April.
It has been described as resembling a large and dirty snowball, but astronomers are hoping the celestial body will put on a bright, brilliant show—not unlike the Hale-Bopp comet which flew close to Earth back in 1997.
— Damian Peach (@peachastro) March 30, 2020
On Tuesday, U.K.-based astronomer George McManus explained:
“Comets tend to develop long, fluorescent tails as they approach the sun before swinging back out into outer space.
We hope that it will become visible to the naked eye in early April reaching closest approach to earth on May 23.
Coming to within 100 million miles of the earth, very close in astronomical terms, it presents no risk to the earth, but does have the potential to lift people’s spirits as we go through the current crisis.”
McManus, who has a 4.5-inch refracting telescope at his East Yorkshire home, noted that a small set of binoculars will be sufficient to view the comet.
Comet C/2019 Y4 (ATLAS) moving from Ursa Major to Camelopardalis. Animation shows movement of last night from 22:58 to 00:50 UTC. 174×30" frames at f/4.8 with @zwoasi 183MM#Comet #CometAtlas #Astrophotography pic.twitter.com/H5EhrA7Ae7
— CosmoNowa (@CosmoNowaMD) March 30, 2020
“Look to the Northern sky. The comet should appear between the Plough and the planet Venus, easily the brightest object in the night sky at the moment other than the moon.
We are hoping it will be as spectacular as Hale-Bopp, which was visible in daylight.”
We don’t know the precise composition of the comet—it could be 90 per cent ice or 90 per cent dust and that could effect whether it throws off a spectacular tail as it gets closer to the sun and the sun’s gravity takes effect.”
While the comet’s timing may shock some readers—especially due to a long history of superstitious beliefs and misperceptions about comets—it’s important to remember that these beautiful spectacles are little more than space dust, ice, and gas that pose no real threat to terrestrial life. | 0.814123 | 3.013941 |
We could have spotted the majestic icy plumes of Saturn’s moon Enceladus 25 years earlier than we did, if only we’d known to look.
The vast fountains of icy material erupting from Enceladus’s south pole enthralled planetary scientists when they were first spotted in images returned by NASA’s Cassini spacecraft in 2005. Further observations suggest that the moon hosts a subsurface sea that could be one of the best places in the solar system to look for life.
Now a space image-processing enthusiast from Tennessee, in the US, believes he’s made a ‘pre-discovery’ of those plumes in archive image data from the Voyager 1 probe, which raced past the Saturn system in 1980.
Ted Stryk – an associate professor of philosophy and English at Roane State Community College who has recently worked with the NASA New Horizons team – processed Voyager 1 data that is publicly available from NASA’s online Planetary Data System to reveal a faint protrusion emanating from the frozen moon’s southern hemisphere.
In order to spot Enceladus’ plumes in the old Voyager data, Stryk needed images taken when the moon was illuminated at a certain angle. But the probe didn’t capture any deliberately targeted shots at those key moments.
So he had to search the archive for where the moon cropped up, under those conditions, in Voyager 1 pictures of other Saturnian subjects. “There was one set where there was a series of eight images that contained Enceladus, just a few pixels across, at a not optimal but useful phase-angle for this kind of work,” he says.
By stacking together and averaging those images, taken in November of 1980, Stryk was able to boost the signal-to-noise ratio of the final picture and so reveal the feature he argues are the plumes found by Cassini decades later. Stryk’s work will be published in the proceedings of the Lunar and Planetary Science Conference, which will take place in The Woodlands, Texas next month.
“It’s remarkable to be able to go back to data taken almost a quarter of a century before Cassini arrived and, armed with the discovery information from Cassini, produce this remarkable processed Voyager image which seems to reveal the plume at that time,” says Andrew Coates, a Cassini scientist at the Mullard Space Science Laboratory in the UK.
If Stryk’s processed image does indeed show the plume from Enceladus’ jets, that could supply researchers with an intriguing new data point, he adds.
“Another detection from 1980 if confirmed has the potential, once the data are fully understood and calibrated, to tell us something about how long the activity has been going on for.”
More on these topics: | 0.846848 | 3.905757 |
McGill University researchers announced yesterday that a Canadian-led team of scientists has found a second repeating fast radio burst (FRB).
As discussed in previous articles on CHIME, FRBs are flash-like bursts of radio energy with an extragalactic origin that only last a few milliseconds. Astronomers only know of about 60 FRBs since the discovery of the first one in 2007.
CHIME proving its worth
According to the news release from McGill the newly discovered repeating FRB “was one of a total of 13 bursts detected over a period of just three weeks during the summer of 2018, while CHIME was in its pre-commissioning phase and running at only a fraction of its full capacity. Additional bursts from the repeating FRB were detected in following weeks by the telescope, which is located in British Columbia’s Okanagan Valley.”
In the video below Perimeter Institute faculty member Kendrick Smith and computational scientist Dustin Lang explain how the CHIME Telescope collaboration zeroed-in on an unprecedented number of FRBs.
A second repeating fast radio burst
Ingrid Stairs, a member of the CHIME team and an astrophysicist at UBC said “until now, there was only one known repeating FRB. Knowing that there is another suggests that there could be more out there. And with more repeaters and more sources available for study, we may be able to understand these cosmic puzzles–where they’re from and what causes them.”
The researchers also said that “the majority of the 13 FRBs detected showed signs of ‘scattering,’ a phenomenon that reveals information about the environment surrounding a source of radio waves. The amount of scattering observed by the CHIME team led them to conclude that the sources of FRBs are powerful astrophysical objects more likely to be in locations with special characteristics.”
Cherry Ng, an astronomer at the University of Toronto and another team member said “that could mean in some sort of dense clump like a supernova remnant. Or near the central black hole in a galaxy. But it has to be in some special place to give us all the scattering that we see.”
The results from the CHIME team were announced at the American Astronomical Society meeting in Seattle and published in two papers in Nature magazine. | 0.898818 | 3.543637 |
March 16 (UPI) -- New research suggests Earth's early magnetic field may have been generated by the liquid portion of the young planet's mantle.
The research, published this week in the journal Earth and Planetary Science Letters, considers a trio of studies that could help scientists better understand the geologic evolution of early Earth.
"Currently we have no grand unifying theory for how Earth has evolved thermally," Stegman said. "We don't have this conceptual framework for understanding the planet's evolution. This is one viable hypothesis."
Geoscientists have long credited Earth's liquid outer core and its molten convection, or dynamo, with generating the planet's magnetic field. In 2007, however, researchers in France published research suggesting Earth's lower mantle wasn't always solid, but was molten. They called it the "the basal magma ocean."
The authors of the latest study, Scripps Oceanography researchers Dave Stegman, Leah Ziegler, and Nicolas Blanc, first published research in 2013 showing a magma ocean in the lower mantle could have been large enough to produce a magnetic field.
Critics claimed that because Earth's mantle is rich in silicate material, a poor conductor of electricity, it's unlikely a liquid mantle could have generated a magnetic field.
For one of the studies reviewed in the latest paper, the scientists set out to determine whether liquid silicate might be more electrically conductive.
"Ziegler and Stegman first proposed the idea of a silicate dynamo for the early Earth," UCLA geophysicist Lars Stixrude said in a news release. "[Results] showed that a silicate dynamo was only possible if the electrical conductivity of silicate liquid was remarkably high, much higher than had been measured in silicate liquids at low pressure and temperature."
Models designed to simulate the electrical properties of silicates inside the basal magma ocean revealed the potential for much greater conductivity than previously estimated.
In another study, Arizona State geophysicist Joseph O'Rourke used the model to show the flowing mantle of Venus could also generate a magnetic field.
"The pioneering studies of Dave Stegman and his collaborators directly inspired my work on Venus," said O'Rourke. "Their recent paper helps answer a question that vexed scientists for many years: How has Earth's magnetic field survived for billions of years?"
If the new hypothesis can gain wider acceptance among geoscientists, it could help researchers develop a theory for how early Earth protected itself from cosmic radiation, allowing for the development of life. The hypothesis could also inspire scientists to rethink the evolution of tectonics on early Earth.
"If the magnetic field was generated in the molten lower mantle above the core, then Earth had protection from the very beginning and that might have made life on Earth possible sooner," Stegman said.
"Ultimately, our papers are complementary because they demonstrate that basal magma oceans are important to the evolution of terrestrial planets," said O'Rourke. "Earth's basal magma ocean has solidified but was key to the longevity of our magnetic field." | 0.816608 | 3.556776 |
Saturn has fascinated amateurs and professionals alike for centuries. As quickly as the planet’s ring system was discovered the popular question became ‘why does Saturn have rings?’ usually followed by ‘what are Saturn’s rings made of?’. Well, here are the answers to both questions.
The simplest answer as to why Saturn has rings and what they are made of is that the planet has accumulated a great deal of dust, particles, and ice at varying distances from its surface. These items are most likely trapped by gravity. The rings appear because of the wavelengths of light reflected by these rings of debris.
Some scientists speculate that Saturn may be too big. Its gravitational pull is so strong that it has been able to snatch debris from space. Some of which is as large as an entire building. That pull is why it has at least 62 moons. Those moons contribute dust to the rings as well as absorb dust from the rings.
A common theory as to how all of the material initially accumulated in Saturn’s rings is a series of asteroid impacts. Not with the planet, but with the moons around it. After the impact the remnants of the asteroids and the debris from the moons could not escape the gravitational pull of the planet.
One other theory holds that the rings of Saturn formed as other moons broke apart in ancient times. Additionally, this theory states that some of the material could be from earlier, during the formation of the solar system, and Saturn could not accrete the material while it was forming and it has been in orbit ever since.
No matter which theory you believe, the rings of Saturn are spectacular. After researching Saturn’s rings a little more, be sure to investigate the ring systems around Neptune, Uranus, and Jupiter. Each system is fainter than Saturn’s, but still interesting.
We’ve also recorded an episode of Astronomy Cast all about Saturn. Listen here, Episode 59: Saturn. | 0.917001 | 3.218055 |
Looking up into the sky is like being in a time machine. Light traveling from the most distant stars and galaxies can take billions of years to reach Earth. So we see them now as they were a long, long time ago. With new telescopes and cameras, astronomers are looking farther back than ever into the dim past.
Two groups of scientists have glimpsed some of the most distant galaxies yet. This is providing new insights into what the universe was like soon after the Big Bang. “We are seeing some of the first galaxies to be born,” says Richard G. McMahon. He works at the University of Cambridge in England.
McMahon’s team looked at images taken with a special camera on the Hubble Space Telescope. The pictures showed six extremely distant galaxies,. One was as far as 12.7 billion light-years away, the researchers report.
The other team was led by Yoshiaki Taniguchi of Tohoku University in Sendai, Japan. It went to Mauna Kea in Hawaii to look through the Subaru telescope, which measures about 25 feet across. This group identified 73 galaxies. One turned out to be the most distant ever seen. It was12.8 billion light-years from Earth, the team reports.
Both groups noticed that the distant galaxies were much dimmer and less dense than similar, closer galaxies. Some scientists speculate that, early on, the universe was filled with smaller galaxies that merged to build the large ones we know today. | 0.802027 | 3.282521 |
From: Jet Propulsion Laboratory
Posted: Friday, October 6, 2006
NASA's long-lived robotic rover Opportunity is beginning to explore layered rocks in cliffs ringing the massive Victoria crater on Mars.
While Opportunity spent its first week at the crater, NASA's newest eye in the Martian sky photographed the rover and its surroundings from above. The level of detail in the photo from the high-resolution camera on the Mars Reconnaissance Orbiter will help guide the rover's exploration of Victoria.
"This is a tremendous example of how our Mars missions in orbit and on the surface are designed to reinforce each other and expand our ability to explore and discover," said Doug McCuistion, director of NASA's Mars Exploration Program in Washington. "You can only achieve this compelling level of exploration capability with the sustained exploration approach we are conducting at Mars through integrated orbiters and landers."
"The combination of the ground-level and aerial view is much more powerful than either alone," said Steve Squyres of Cornell University, Ithaca, N.Y. Squyres is principal investigator for Opportunity and its twin, Spirit. "If you were a geologist driving up to the edge of a crater in your jeep, the first thing you would do would be to pick up the aerial photo you brought with you and use it to understand what you're seeing from ground level. That's exactly what we're doing here."
Caption: This image from the High Resolution Imaging Science Experiment on NASA's Mars Reconnaissance Orbiter shows the Mars Exploration Rover Opportunity near the rim of "Victoria Crater." Victoria is an impact crater about 800 meters (half a mile) in diameter at Meridiani Planum near the equator of Mars. Opportunity has been operating on Mars since January, 2004. Five days before this image was taken, Opportunity arrived at the rim of Victoria, after a drive of more than 9 kilometers (over 5 miles). It then drove to the position where it is seen in this image.
Shown in the image are "Duck Bay," the eroded segment of the crater rim where Opportunity first arrived at the crater; "Cabo Frio," a sharp promontory to the south of Duck Bay; and "Cape Verde," another promontory to the north. When viewed at the highest resolution, this image shows the rover itself, wheel tracks in the soil behind it, and the rover's shadow, including the shadow of the camera mast. After this image was taken, Opportunity moved to the very tip of Cape Verde to perform more imaging of the interior of the crater.
This view is a portion of an image taken by the High Resolution Imaging Science Experiment (HiRISE) camera onboard the Mars Reconnaissance Orbiter spacecraft on Oct. 3, 2006. The complete image is centered at minus 7.8 degrees latitude, 279.5 degrees East longitude. The range to the target site was 297 kilometers (185.6 miles). At this distance the image scale is 29.7 centimeters (12 inches) per pixel (with 1 x 1 binning) so objects about 89 centimeters (35 inches) across are resolved. North is up. The image was taken at a local Mars time of 3:30 PM and the scene is illuminated from the west with a solar incidence angle of 59.7 degrees, thus the sun was about 30.3 degrees above the horizon. At a solar longitude of 113.6 degrees, the season on Mars is northern summer.
Images from NASA's Mars Global Surveyor, orbiting the red planet since 1997, prompted the rover team to choose Victoria two years ago as the long-term destination for Opportunity. The images show the one-half-mile-wide crater has scalloped edges of alternating cliff-like high, jutting ledges and gentler alcoves. The new image by the Mars Reconnaissance Orbiter adds significantly more detail.
Exposed geological layers in the cliff-like portions of Victoria's inner wall appear to record a longer span of Mars' environmental history than the rover has studied in smaller craters. Victoria is five times larger than any crater Opportunity has visited during its Martian trek.
High-resolution color images taken by Opportunity's panoramic camera since Sept. 28 reveal previously unseen patterns in the layers. "There are distinct variations in the sedimentary layering as you look farther down in the stack," Squyres said. "That tells us environmental conditions were not constant."
Within two months after landing on Mars in early 2004, Opportunity found geological evidence for a long-ago environment that was wet. Scientists hope the layers in Victoria will provide new clues about whether that wet environment was persistent, fleeting or cyclical.
The rovers have worked on Mars for more than 10 times their originally planned three-month missions. "Opportunity shows a few signs of aging but is in good shape for undertaking exploration of Victoria crater," said John Callas, project manager for the rovers at NASA's Jet Propulsion Laboratory, Pasadena, Calif.
"What we see so far just adds to the excitement. The team has worked heroically for nearly 21 months driving the rover here, and now we're all rewarded with views of a spectacular landscape of nearly 50-foot-thick exposures of layered rock," said Jim Bell of Cornell. Bell is lead scientist for the rovers' panoramic cameras. NASA plans to drive Opportunity from crater ridge to ridge, studying nearby cliffs across the intervening alcoves and looking for safe ways to drive the rover down. "It's like going to the Grand Canyon and seeing what you can from several different overlooks before you walk down," Bell said.
The orbiter images will help the team choose which way to send Opportunity around the rim, and where to stop for the best views. Conversely, the rover's ground-level observations of some of the same features will provide useful information for interpreting orbital images.
"The ground-truth we get from the rover images and measurements enables us to better interpret features we see elsewhere on Mars, including very rugged and dramatic terrains that we can't currently study on the ground," said Alfred McEwen of the University of Arizona, Tucson. He is principal investigator for the orbiter's High Resolution Imaging Science Experiment camera.
The Jet Propulsion Laboratory manages the rovers and orbiter for NASA's Science Mission Directorate. For images and information about the rovers, visit:
For images and information about the Mars Reconnaissance Orbiter, visit:
// end // | 0.835156 | 3.407001 |
The threat of asteroids crashing into Earth isn’t a new concern. We’ve been warned about it by science fiction authors and Hollywood alike, and any kid that’s ever paid attention to dinosaurs in school knows there are bad outcomes when life and chunks of space rock meet up. The space agencies of Europe and the United States are not blind to the threat, thankfully, and they have a multi-part satellite mission in the works directed to gathering real data on how to redirect an asteroid with bad intentions for our planet, i.e., is on a collision course. Specifically, they’re planning on crashing one satellite into an asteroid and studying the effect with another satellite run by the European Space Agency (ESA).
NASA’s part of the mission is called the Double Asteroid Redirection Test (DART), and it will serve as the first demonstration of changing asteroid motion in space. The launch window begins in late December 2020, most likely on track for June 2021, for arrival at its targeted asteroid, Didymos, in early October 2022. Didymos is Greek for “twin”, the name being chosen because it’s a binary system with two bodies: Didymos the asteroid, about a half mile across, and Didymoon the moonlet, about 530 feet across, acting as a moonlet. The two currently have a Sun-centric orbit and will have a distant approach to Earth around the same time as DART’s launch window and then again in 2024.
After reaching the asteroid, DART will enter orbit around Didymoon, and crash into it at a speed of about 4 mi/s (nine times faster than a bullet) to change its speed by a fraction of one percent, an amount measurable by Earth-based telescopes for easy study. Unsurprisingly, the preferred description is “kinetic impact technique” rather than “crash” – maybe even “impact” or “strike”, if we’re avoiding terms that sound random or accidental. The mission is being led by the Johns Hopkins Applied Physics Laboratory (JHU/APL) and managed by the Planetary Missions Program Office at Marshall Space Flight Center in Alabama for NASA’s Planetary Defense Coordination Office.
NASA’s DART mission is one of two parts of an overall mission dubbed AIDA (Asteroid Impact & Deflection Assessment). Joining the agency’s Earth-protection venture is the ESA with its Hera spacecraft, named after the Greek goddess of marriage, a probe that will follow up DART’s mission with a detailed survey of the asteroid’s response to the impact. Collected data will help formulate planetary defense plans by providing detailed analysis from DART’s real-time asteroid deflection experiment. Its launch is scheduled for 2023.
Just this month, another part was added to Hera’s mission: CubeSats. This class of tiny satellites is about the size of a briefcase, and they recently made their deep space debut during NASA’s Mars InSight landing. During that mission, twin CubeSats collectively named MarCO followed along on the journey to Mars behind InSight, eventually relaying data during the landing event back to NASA’s Mission Control along with a photo of the red planet. ESA’s CubeSats, named APEX (Asteroid Prospection Explorer) and Juventas, will travel inside Hera, gather data on Didymos and its moonlet, and then both will land on their respective rocks and provide imaging from the surface.
Just to recap: Tiny satellites in a class that students and startups can and have developed and launched will travel into deep space and land on asteroids. This is big news for the democratization of space travel. As emphasized by Paolo Martino, Hera’s lead engineer in ESA’s article announcing the CubeSat mission, “The idea of building CubeSats for deep space is relatively new, but was recently validated by NASA’s InSight landing on Mars last November.”
Using kinetic energy – pure ram/crash force – isn’t the only option NASA is looking at for defending Earth from incoming asteroids. A “gravity tractor” concept would orbit a craft in a way that would change the trajectory due to gravitational tugging. Similar to how our moon has an impact on our tides or the Earth makes the Sun wobble ever so slightly, a satellite orbiting an asteroid would give pushes and pulls to set its course elsewhere.
Unfortunately, a gravity tractor likely wouldn’t be very effective for asteroids large enough to seriously threaten our planet. Also, the techniques for achieving it would require decades to develop and test in space. Laser ablation, or using spacecraft lasers to vaporize asteroid rock to change an asteroid’s course, is another technique NASA has considered, but it might be just as feasible or cost-effective to simply launch projectiles to achieve the same purpose.
Watch the below video for a visual overview of the DART and HERA missions: | 0.838251 | 3.565385 |
Detections of planets orbiting nearby stars naturally require establishing what is meant by a “planet” and how do we know a planet when we see one? This question is not as easy to answer as it is to pose. To understand the difficulties, it is useful to examine the answer to: “Is Pluto a planet?”—a simple question without a simple answer.
Astronomers like categorising objects of astronomical and astrophysical interest, giving them labels such as “planets”, “stars”, “asteroids” and many more. According to the decision of the International Astronomical Union (IAU), Pluto is classified as a “dwarf planet” because it is not the “gravitationally dominant body” on its orbit. Setting aside for a moment what that actually means, it is, however, pretty obvious based on the recent imagery from the NASAs New Horizons mission that Pluto is certainly a world in its own right – something that we could be very tempting to call a planet regardless of what the IAU has decided.
According to the IAU, a planet is defined as follows:
A “planet” is a celestial body that (a) is in orbit around the Sun, (b) has sufficient mass for its self-gravity to overcome rigid body forces so that it assumes a hydrostatic equilibrium (nearly round) shape, and (c) has cleared the neighbourhood around its orbit.
A “dwarf planet” is a celestial body that (a) is in orbit around the Sun, (b) has sufficient mass for its self-gravity to overcome rigid body forces so that it assumes a hydrostatic equilibrium (nearly round) shape, (c) has not cleared the neighbourhood around its orbit, and (d) is not a satellite.
All other objects, except satellites, orbiting the Sun shall be referred to collectively as “Small Solar-System Bodies”.
Although Pluto is in orbit around the Sun and has sufficient self-gravity to assume a roughly spherical shape through hydrostatic equilibrium, it has not cleared the neighbourhood of its orbit by gravitationally tugging smaller objects out of its residential area in the Solar System. IAU therefore decided to classify Pluto as a dwarf planet rather than a full-blown member of the set of planets in the Solar System.
The situation gets more complicated when remembering that Jupiter, for instance, has also failed to clear the neighbourhood around its orbit, as there are thousands of trojan asteroids at and around Jupiter’s orbit. Yet, nobody disagrees whether we should classify Jupiter as a planet or not.
But with respect to extra-solar planets, the IAUs resolution is not valid – it has only been designed to be valid when classifying celestial bodies in the Solar System.
Astronomers consider extra-solar objects that orbit stars other than the Sun to be planets if they (1) are large enough to have reached hydrostatic equilibria, and (2) small enough such that they cannot sustain nuclear fusion in their cores and thus cannot be considered stars or even brown dwarfs. But that is only where the problems begin—it is not at all trivial to determine how large the objects orbiting other stars are when their very presence is difficult to observe.
It is reasonably straightforward to conclude that an object transiting a nearby star, such as the extraordinary haul of worlds found by the Kepler spacecraft, is large enough to have reached hydrostatic equilibrium if it is in fact large enough to be seen blocking the light coming from the stellar surface. But what about the larger objects that are comparable in size to Jupiter? Because the planetary transits can only reveal their radii in relation to their host stars, it cannot be known whether some of them are in fact more than roughly 13 times more massive than the Jupiter, which is sufficient for the fusion of deuterium into helium in their cores. Such objects would then be classified as brown dwarfs rather than planets.
The situation is even more complicated, sometimes frustratingly so, when observing exoplanets with the Doppler spectroscopy technique applied in the Pale Red Dot campaign. Because this technique can only be used to reveal the lower limit for the planetary masses, it is impossible to tell whether any individual discovery actually corresponds to a genuine planet rather than a small star or a brown dwarf even though, on statistical grounds, the vast majority of them are certainly small enough to be considered planets.
But whether extra-solar objects of suitable size to be classified as planets have cleared the neighborhoods of their orbits is beyond our observational capabilities. It is also less than certain what the possible free-floating planetary sized objects should be called as they do not revolve around stars of any kind.
It is quite possible that a general definition of a planet proves as elusive as that of a “continent” that no geographer dares to define—nor are they even interested in doing so. Similarly, biologists cannot produce a general definition for “life” but more often than not simply say that “they know whether it is alive or not when they see it”, which can be seen as an attempt to brush the problem under the carpet. It is probably a human trait to attempt classifying things into rigid categories even when nature has cynically decided that there is simply a continuum of objects and that any and all classifications are thus only subjective opinions without any deeper meanings. In such cases, the definitions do not help in understanding nature any better—and may even hinder scientific developments by providing a biased frame of reference.
And Pluto, as it – in my opinion – certainly is a world in its own right, deserves to be called a planet regardless of any subjective definitions individuals might consider appropriate. Although that might not be acceptable for all, one thing is clear. If an object resembling Pluto was found orbiting a star other than the Sun, I believe it would be called a planet.
About the author. M. Tuomi is working as an astronomer at the University of Hertfordshire, UK. His research interests include detection and characterization of low-mass planets and planetary systems around nearby stars, development of statistical models or Doppler spectroscopy data to understand variability caused by astrophysical and instrumental effects, study of the dynamical properties of tightly packed planetary systems, and exploring the
statistical properties of small planets orbiting the stars in the Solar
neighborhood. He has also worked as an environmental scientist at the Finnish Environment Institute. M. Tuomi is one of the editors of palereddot.org, and can be blamed for first spotting tentative evidence of ‘The signal’ in archival UVES and HARPS data. | 0.901477 | 3.877871 |
Orlando: A NASA explorer is believed to have reached the solar system's outermost region early Tuesday morning, flying close to a space rock 20 miles long and billions of miles from Earth on a mission to gather clues about the creation of the solar system.
The body is farther from Earth than any other that has had such a close encounter with a NASA probe, scientists believe.
The New Horizons probe was slated to reach the "third zone" in the uncharted heart of the Kuiper Belt at 12:33 a.m. Eastern. Scientists will not have confirmation of its successful arrival until the probe communicates its whereabouts through NASA's Deep Space Network at 10:28 a.m. Eastern, about 10 hours later.
Once it enters the peripheral layer of the belt, containing icy bodies and leftover fragments from the solar system's creation, the probe will get its first close-up glance of Ultima Thule, a cool mass shaped like a giant peanut, using seven on-board instruments.
Scientists had not discovered Ultima Thule when the probe was launched, according to NASA, making the mission unique in that respect. In 2014, astronomers found Thule using the Hubble Space Telescope and selected it for New Horizon's extended mission in 2015.
"Anything's possible out there in this very unknown region," John Spencer, deputy project scientist for New Horizons, told reporters on Monday at the Johns Hopkins Applied Physics Laboratory in Maryland.
Launched in January 2006, New Horizons embarked on a 4 billion mile journey toward the solar system's frigid edge to study the dwarf planet Pluto and its five moons.
During a 2015 fly-by, the probe found Pluto to be slightly larger than previously thought. In March, it revealed that methane-rich dunes were on the icy dwarf planet's surface.
After trekking 1 billion miles beyond Pluto into the Kuiper Belt, New Horizons will now seek clues about the formation of the solar system and its planets.
As the probe flies 2,200 miles (3,500 km) above Thule's surface, scientists hope it will detect the chemical composition of its atmosphere and terrain in what NASA says will be the closest observation of a body so remote.
"We are straining the capabilities of this spacecraft, and by tomorrow we'll know how we did," New Horizons principal investigator Alan Stern said during the news conference at the Johns Hopkins Applied Physics Laboratory in Maryland. "There are no second chances for New Horizons."
While the mission marks the farthest close-encounter of an object within our solar system, NASA's Voyager 1 and 2, a pair of deep space probes launched in 1977, have reached greater distances on a mission to survey extrasolar bodies. Both probes are still operational. | 0.826756 | 3.178094 |
With InSight safely on the surface of Mars, the mission team at NASA’s Jet Propulsion Laboratory in Pasadena, California, is busy learning more about the spacecraft’s landing site.
They knew when InSight landed on Nov. 26 that the spacecraft had touched down on target, a lava plain named Elysium Planitia.
Now they’ve determined that the vehicle sits slightly tilted (about 4 degrees) in a shallow dust- and sand-filled impact crater known as a “hollow.” InSight has been engineered to operate on a surface with an inclination up to 15 degrees.
“The science team had been hoping to land in a sandy area with few rocks since we chose the landing site, so we couldn’t be happier,” said InSight project manager Tom Hoffman of JPL.
“There are no landing pads or runways on Mars, so coming down in an area that is basically a large sandbox without any large rocks should make instrument deployment easier and provide a great place for our mole to start burrowing.”
Rockiness and slope grade factor into landing safety and are also important in determining whether InSight can succeed in its mission after landing.
Rocks and slopes could affect InSight’s ability to place its heat-flow probe — also known as “the mole,” or HP3 — and ultra-sensitive seismometer, known as SEIS, on the surface of Mars.
Touching down on an overly steep slope in the wrong direction could also have jeopardized the spacecraft’s ability to get adequate power output from its two solar arrays while landing beside a large rock could have prevented InSight from being able to open one of those arrays. In fact, both arrays fully deployed shortly after landing.
The InSight science team’s preliminary assessment of the photographs taken so far of the landing area suggests the area in the immediate vicinity of the lander is populated by only a few rocks.
Higher-resolution images are expected to begin arriving over the coming days after InSight releases the clear-plastic dust covers that kept the optics of the spacecraft’s two cameras safe during landing.
“We are looking forward to higher-definition pictures to confirm this preliminary assessment,” said JPL’s Bruce Banerdt, principal investigator of InSight.
“If these few images — with resolution-reducing dust covers on — are accurate, it bodes well for both instrument deployment and the mole penetration of our subsurface heat-flow experiment.”
Once sites on the Martian surface have been carefully selected for the two main instruments, the team will unstow and begin initial testing of the mechanical arm that will place them there.
Data downlinked from the lander also indicate that during its first full day on Mars, the solar-powered InSight spacecraft generated more electrical power than any previous vehicle on the surface of Mars.
“It is great to get our first ‘off-world record’ on our very first full day on Mars,” said Hoffman.
“But even better than the achievement of generating more electricity than any mission before us is what it represents for performing our upcoming engineering tasks. The 4,588 watt-hours we produced during sol 1 means we currently have more than enough juice to perform these tasks and move forward with our science mission.”
Launched from Vandenberg Air Force Base in California May 5, InSight will operate on the surface for one Martian year, plus 40 Martian days, or sols — the equivalent of nearly two Earth years.
InSight will study the deep interior of Mars to learn how all celestial bodies with rocky surfaces, including Earth and the Moon, formed.
JPL manages InSight for NASA’s Science Mission Directorate. InSight is part of NASA’s Discovery Program, managed by the agency’s Marshall Space Flight Center in Huntsville, Alabama.
A number of European partners, including France’s Centre National d’Études Spatiales (CNES) and the German Aerospace Center (DLR), are supporting the InSight mission. CNES, and the Institut de Physique du Globe de Paris (IPGP), provided the SEIS instrument, with significant contributions from the Max Planck Institute for Solar System Research (MPS) in Germany, the Swiss Institute of Technology (ETH) in Switzerland, Imperial College and Oxford University in the United Kingdom, and JPL. DLR provided the HP3 instrument, with significant contributions from the Space Research Center (CBK) of the Polish Academy of Sciences and Astronika in Poland. Spain’s Centro de Astrobiología (CAB) supplied the wind sensors.
For more information about InSight, visit: | 0.838261 | 3.408415 |
- Open Access
Dust attenuation in galaxies up to redshift ≃ 2
Earth, Planets and Space volume 65, Article number: 3 (2013)
We want to study dust attenuation at ultraviolet (UV) wavelengths at high redshift, where the UV is redshifted to the observed visible light wavelength range. In particular, we search for a bump at 2175 Å. We use photometric data in the Chandra Deep Field South (CDFS), obtained in intermediate and broad band filters by the MUSYC project, to sample the UV rest-frame of 751 galaxies with 0.95 < z < 2.2. When available, infrared (IR) Herschel/PACS* data from the GOODS-Herschel project, coupled with Spitzer/MIPS measurements, are used to estimate the dust emission and to constrain dust attenuation. The spectral energy distribution of each source is fit using the CIGALE code†. The average attenuation curve found for our sample galaxies exhibits a UV bump whose amplitude is similar to that observed in the extinction curve of the LMC super-shell region. The slope of the average attenuation curve at UV wavelength is found steeper than that for local starburst galaxies. The amount of dust attenuation at UV wavelengths is found to increase with stellar mass and to decrease as UV luminosity increases.
Although dust is a minor component in galaxies, it captures a large fraction of the stellar emission, especially at short wavelengths. This process makes the direct observation of stellar populations from the UV to the near-IR insufficient to recover all the emitted photons. Thus reliable dust corrections are mandatory for measuring the star formation rate (SFR) in the universe and its evolution with redshift from UV-optical surveys. The search for relations between dust attenuation and observed or commonly measured quantities are very useful in this context. It is also particularly important to study the dependence of dust attenuation on wavelength in order to recover the intrinsic spectral distribution of the stellar light, which gives information on the star formation history at work in galaxies.
Models solving radiation transfer rely on numerous free parameters and physical assumptions that are difficult to constrain from the integrated emission from entire galaxies and for very large numbers of objects. Simpler models have been specifically developed to analyze large samples of galaxies, introducing simple recipes and templates. The number of free parameters is considerably reduced. These codes are often developed to measure photometric redshifts and physical parameters such as the SFR and the stellar mass. With the availability of mid and far-IR data for large samples of galaxies, new codes are emerging that combine stellar and dust emission on the basis of the balance between the stellar luminosity absorbed by dust and the corresponding luminosity re-emitted in the IR. Attenuation laws are introduced in these codes. The most popular attenuation curve is that of Calzetti et al. (2000), built for local starburst galaxies. This law, based on spectroscopic data, does not exhibit a bump at 2175 Å such as that observed in the extinction curves of the Milky Way (MW) or the Large Magellanic Cloud supershell (LMC2). Since the Calzetti and collaborators work, numerous studies have tried to search for the presence of a bump in the attenuation curve of nearby, non starbursting, galaxies. Most studies based on very different approaches conclude to a presence of bump in large samples of nearby star forming galaxies (Burgarella et al., 2005; Conroy et al., 2010; Wild et al., 2011). At higher redshifts, the situation is more favorable because of the redshifting of the UV emission into visible. Direct evidence of bumps came from the analysis of the galaxy spectra at 1 < z < 2.5 (Noll et al., 2009). Recently Buat et al. (2011b), (2012) analyzed spectral energy distributions (SEDs) of UV selected galaxies in a redshift range between 0.95 and 2.2, observed through intermediate band filters and with IR detections from Herschel/PACS, and found evidence for a UV bump in the dust attenuation curve of all these galaxies. The present work extends the analysis performed in these two papers. After a brief description of the data (Section 2) and of the fitting tool used for the analysis (Section 3), the average attenuation curve obtained with the dataset is compared to extinction curves of LMC2 and MW and to the models of Inoue et al. (2006) in Section 4. Relations linking dust attenuation to UV luminosity and stellar mass are presented in Section 5.
2. High Redshift Galaxies Selected in the Ultraviolet
The sample selection is described in Buat et al. (2012). We briefly summarize the selection process and the main characteristics of the resulting sample. The field considered is located in the Great Observatories Origins Deep Survey Southern field (GOODS-S). It was observed at 100 and 160 µm over 264 hours by the PACS instrument onboard of the Herschel Space Observatory (Pilbratt et al., 2010) as part of the GOODS-Herschel open time key project (Elbaz et al., 2011). The MUSYC project (Cardamone et al., 2010) compiled a uniform catalogue of optical and IR photometry for sources in this field, incorporating the GOODS Spitzer IRAC and MIPS data as well as intermediate and broad-band optical data. It provides a valuable means of tracing the detailed shape of the UV rest-frame spectrum. We started with the MUSYC catalogue, selecting sources with a spectroscopic redshift between 0.95 and 2.2 and no X ray detection. In this redshift range we have more than ten photometric bands available in the UV rest-frame and a good sampling around 2175 Å. We consider all the optical broad bands (7 bands from U to z) and intermediate-band filters (11 bands) whose 5σ depth was fainter than 25 ABmag. Our sample contains 751 sources, all detected by IRAC at 3.6µm. 290 sources have a 3σ detection at 24 µm, 76 of these sources are also detected by PACS at 100 µm.
3. CIGALE: A SED Fitting Tool Aimed at Studying Dust Attenuation in Galaxies
The CIGALE code (Code Investigating GALaxy Emission, http://cigale.oamp.fr) was developed by Noll et al. (2009). This is a physically-motivated code that derives properties of galaxies by fitting their UV-to-IR SEDs. CIGALE combines a UV-optical stellar SED with a dust component emitting in the IR and fully conserves the energy balance between the dust absorbed stellar emission and its re-emission in the IR. We refer to Noll et al. paper for details on the code. For the purpose of the present work we focus on the dust attenuation treatment performed by CIGALE, the various input parameters introduced for this analysis are discussed in Buat et al. (2012). The dust attenuation is described as
Throughout the paper the wavelength λ will be expressed in Å, λV = 5500 Å, k′(λ) 1 Footnote 1 comes from Calzetti et al. (2000) (Eq. (4)) and Dλ0,γEb(λ), the Lorentzian-like Drude profile commonly used to describe the UV bump, is defined as
The factor produces different slopes without modifying the visual attenuation AV. It implies changes in the value of the effective total obscuration RV, originally equal to 4.05 for the Calzetti et al. law.
The reliability of parameter determinations is extensively discussed in Buat et al. (2012) with the analysis of a catalog of artificial galaxies and that of the 76 galaxies detected by PACS. Parameters are better estimated when at least one IR measurement is available, which is the case for 290 of our objects. Without IR data dust attenuation at UV wavelength is found slightly over-estimated for low values of this parameter (of the order of 0.3 mag for an attenuation of 1 mag), the amplitude of the bump Eb is robustly estimated whereas the slope δ is over-estimated for low values (by 0.1 unit for δ = −0.5). We refer to Buat et al. (2012) for more details about the SED fitting analysis.
E b and δ are estimated for each object as the mean value of their probability distribution function (PDF) given by CIGALE. The resulting distributions obtained for these estimated parameters are shown in Fig. 1. The typical uncertainty for each estimation (dispersion of the PDF) is found to be 0.8 for E b and 0.15 for δ. The average values and standard deviations of the distributions of Fig. 1 are ⟨Eb⟩ = 1.6 ± 0.4 and ⟨δ⟩ = −0.27 ± 0.17. The large uncertainty in the determination of the parameters implies that only 20% of individual sources (40% of the sources detected in IR) exhibit a secure bump and and an attenuation curve steeper than the Calzetti et al. one. In the next section, we will focus on the analysis of the average attenuation curve and not on the dispersion found for individual source. A detailed discussion of the individual measurements can be found in Buat et al. (2012).
4. Average Dust Attenuation Curve
We can tentatively derive an average attenuation curve for our sample.
Models predict a variation of the shape of the attenuation curve and of the amplitude of the bump with the amount of dust attenuation (e.g. Inoue et al., 2006). The mean dust attenuation at 1530 A for the sample is found to be ⟨AFUV⟩= 2.2 mag and the average dust attenuation curve given above is expected to be representative of galaxies with this average attenuation.
The resulting curve is plotted in Fig. 2 with other curves already considered in Fig. 1. As underlined in Buat et al. (2012) the average attenuation curve is close to the extinction curve found for the LMC2 super-shell. Inoue et al. (2006) predicted various attenuation curves for the UV range. In Fig. 3 we compare the result of their models obtained with dust characteristics from Draine (2003) and corresponding to AFUV = 2 mag. The extinction curve for the LMC2 super-shell is also over-plotted. Whereas the amplitude of the bump is well reproduced in the Inoue et al. model with LMC dust, the corresponding attenuation curve is steeper than the one derived from the data. The general shape is better reproduced with a MW type dust but this time the predicted amplitude of the bump is too large. The best agreement is found with the LMC2 extinction curve.
5. Dust Attenuation Variation
In the absence of IR emission to constrain dust attenuation, empirical relations linking the amount of dust attenuation to some galaxy characteristics are particularly useful. Any systematic trend with the observed UV luminosity is important to account for when intrinsic, attenuation corrected luminosity functions are studied. Another crucial physical parameter is the stellar mass. It is mainly constrained by the optical-NIR part of the SED which is not very sensitive to dust attenuation and can be securely estimated even when dust attenuation is badly known. As a consequence any relation between dust attenuation and stellar mass will be particularly useful at least to apply global corrections to large samples of galaxies. Hereafter we will discuss dust attenuation at FUV, with a FUV wavelength taken at 1530 Å (corresponding to the FUV GALEX filter). The FUV luminosity LFUV is defined as λ × Lλ and expressed in solar units (L☉).
5.1 Dust attenuation and observed luminosities
Buat et al. (2012) (see also Heinis et al., MNRAS, submitted) reported a decrease of the mean dust attenuation when the observed FUV luminosity increases with a dispersion increasing at low luminosities. The data points and the average values per bin of FUV luminosity calculated by Buat et al. (2012) are reported in Fig. 4. We perform a linear regression between the average values of AFUV expressed in magnitudes and LFUV in solar units:
the uncertainties on the coefficients (slope and constant) correspond to standard deviations, the global R.M.S. error is found equal to 0.04, and the correlation coefficient R is equal to 0.99.
The detected galaxies become more luminous when the redshift increases because of selection effects as clearly seen in Fig. 4. So any study of the variation of dust attenuation with z must account for this decrease of the attenuation when LFUV increases.
5.2 Dust attenuation and stellar masses
Stellar masses (Mstar) are obtained as an output of the fitting code CIGALE as described in Buat et al. (2012). The adopted IMF is that of Kroupa (2001). Mean dust attenuation factors can be calculated per bin of Mstar, the results are reported in Fig. 5. We perform a linear regression on these average values, the correlation coefficient is found very high (R = 0.97) and the linear regression gives:
the uncertainties on the coefficients (slope and constant) correspond to standard deviations, the global R.M.S. error is found equal to 0.16. This relation can be compared to other ones also obtained for UV selected galaxies from z = 0 to z = 2. Up to z = 1 the FUV rest-frame range is well sampled with GALEX data. Buat et al. (2007) performed a statistical analysis of the GALEX and IRAS surveys and deduced volume corrected relations about far-IR and FUV properties of galaxies in the nearby universe. Here, we use their UV selected sample to calculate the average far-IR to FUV flux ratio per bin of stellar mass following the method explained in Buat et al. (2007). The amount of dust attenuation is then calculated by applying the relation of Buat et al. (2011a). The average values and the result of the linear regression fitted on them is reported in Fig. 5. Garn and Best (2010) obtained a relation between dust attenuation and stellar mass for SDSS galaxies based on the measure of the Balmer decrement, their relation is extrapolated at FUV wavelength using the Meurer et al. (2009) relation AFUV = 1.68AHα and is also reported on Fig. 5. Note that this extrapolation is very crude given the large dispersion in the scatter plot between AFUV and AHα and the uncertainty on the average value of AFUV/AHα (Bell and Kennicutt, 2001; Buat et al., 2002; Boselli et al., 2013). Buat et al. (2009) investigated UV selected galaxies from z = 0 to z = 1 and found a trend with MFUV and no clear evolution with redshift of the AFUV − Mstar scatter plot. We report their average relation corresponding to log(LFUV) = 10.2[L☉], representative of our current sample (see Buat et al. (2012) for more details). At z = 2 Sawicki (2012) built a FUV selected sample from the Ultra-deep Hubble field and found a relation between dust attenuation and stellar mass (estimated from the observed FUV luminosity), his relation is also reported in Fig. 5. The relation obtained in the present work for galaxies with redshift between 0.95 and 2.2 predicts slightly higher dust attenuation factors than the three other ones but remain consistent within the error bars with most of the relations considered in Fig. 5. The relation found at z = 0 by Buat et al. (2007) leads to lower dust attenuation for massive galaxies by ~1 mag for log(Mstar) > 10.5[M☉] but their statistics for high mass galaxies was low. The Garn and Best relation based on larger statistics is found closer the other ones at higher z. We can conservatively conclude to a well defined relation between average dust attenuation and Mstar for UV selected galaxies which does not show a significant evolution from z = 0 to z = 2.
The trend found with the FUV luminosity (i.e. a lower mean dust attenuation when LFUV increases) is clearly visible in Fig. 5, upper panel. It might imply a modification of the mean relation as a function of the luminosity, the FUV luminosity also acting as a parameter in the variation of dust attenuation. A complete analysis of this relation per bin of FUV luminosity and stellar mass at different redshifts has still to be performed. The current samples are too small for such a study. Heinis et al. (in preparation) will analyze a much larger sample of galaxies in the COSMOS field based on stacked Herschel/SPIRE images to better constrain average dust attenuation factors.
k′(λ) = 2.659(−2.156+1.509104/λ− 0.198108/λ2 + 0.0111012/λ3) + 4.05 for 1200 < λ < 6300 Åand k′(λ) = 2.659(−1.857 + 1.040104/λ) + 4.05 for 6300 < λ < 22000 Å
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This work is partially supported by the French National Agency for research (ANR-09-BLAN-0224). PACS has been developed by a consortium of institutes led by MPE (Germany) and including UVIE (Austria); KU Leuven, CSL, IMEC (Belgium); CEA, LAM (France); MPIA (Germany); INAFIFSI/OAA/OAP/OAT, LENS, SISSA (Italy); IAC (Spain). This development has been supported by the funding agencies BMVIT (Austria), ESA-PRODEX (Belgium), CEA/CNES (France), DLR (Germany), ASI/INAF (Italy), and CICYT/MCYT (Spain).
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Cite this article
Buat, V. Dust attenuation in galaxies up to redshift ≃ 2. Earth Planet Sp 65, 3 (2013). https://doi.org/10.5047/eps.2013.02.001
- Galaxies: high-redshift
- galaxies: ISM
- dust: extinction | 0.862476 | 3.965946 |
Deep space images aid dark matter study
New images of deep space are helping shed light on the material that accounts for more than 80 per cent of the universe.
The images are the first from an international project that seeks to aid understanding of dark matter - how much of it is contained, and how it is distributed, in groups of galaxies - such as the group that houses the Milky Way.
The study is also hoped to improve scientists’ knowledge of how galaxies are formed.
Being able to explain dark matter would represent a major scientific breakthrough.
Researchers analysed images of more than two million galaxies, typically 5.5 billion light years away, and used their results to calculate precise measurements of the influence of dark matter.
They examined how light emitted by galaxies is distorted by the pull of gravity as it passes massive clumps of dark matter.
Researchers found that groups of galaxies typically contain 30 times more dark matter than the visible matter seen in stars.
They also showed that the brightest galaxy in each group nearly always sits at the centre of the dark matter clump that surrounds it.
This is the clearest demonstration to date of this phenomenon, predicted by theories of galaxy formation.
Their research, known as the Kilo-Degree Survey (KiDS), uses images captured by the VLT Survey Telescope at the European Southern Observatory in Paranal, Chile.
The study, led by Leiden University in the Netherlands, was carried out in collaboration with scientists from the Universities of Edinburgh and Oxford, University College London, Durham University, and from Italy, Germany, and Australia.
It is published in The Monthly Notices Of The Royal Astronomical Society.
These early results in our quest to create a map of dark matter throughout the Universe are encouraging. We are on our way to a better understanding of the mysteries of this elusive substance, thanks to sophisticated telescope technology and the efforts of our international team of scientists.
We look forward to making many more discoveries about this most elusive of substances, dark matter, in the months ahead. | 0.832998 | 3.481469 |
About Jupiter's Family Secrets
Secrets of the Solar System Family
Our solar system is a family of planets, dwarf planets, comets, and asteroids orbiting our Sun, each harboring clues of our common origins, with their disparate compositions and characteristics.
How do scientists discover those secrets? Ancient civilizations studied the skies and noted the strange travelings of "wanderers," or "planetes" in Greek, which seemed to move against the background of familiar constellations. Telescopes allowed astronomers to view the surfaces of planets; spacecraft instruments now allow us to infer information about the interiors of planets. Instruments like radar, orbital mapping devices, and others that detect wavelengths of light invisible to the human eye are some of the tools that allow spacecraft to explore other worlds.
NASA's Juno mission to Jupiter launched in 2011 and will not only investigate the deepest mysteries of Jupiter's unique personality, but will also plumb the secrets of our solar system's origins.
Our Solar System Was Born from a Cloud of Gas and Dust
Like all families, the members of our solar system family share a common origins story. Their story started even before our solar system formed 4.6 billion years ago.
The prelude to this first chapter was when our universe (all space and time and matter and energy) was born in the Big Bang about 13.7 billion years ago. The universe began as a single point, rapidly expanding into space and time; as the intense radiation that filled the space began to cool, elementary particles began to fill it. Eventually, particles combined and formed clouds of gas and eventually stars and galaxies. More information about the Big Bang is at http://www.cfa.harvard.edu/seuforum/bigbanglanding.htm
The first stars lived out their lives and eventually exploded, sending "star stuff" out into the cosmos. That original stellar material was recycled as another generation of stars, and many of these, too, exploded at the end of their lives. Our Sun is thought to be a third–generation star and our entire solar system is made of the recycled star stuff of previous star generations. Our Sun is a granddaughter of the very first stars!
Our solar system began forming within a concentration of interstellar dust and hydrogen gas which contracted into a solar nebula, forming the proto-Sun and planetesimals that eventually joined into planets. Check out how the planets formed and changed through a series of images at the "Evolution of our Solar System" timeline.
Scientists still have many questions about our solar system's story, and Juno will help scientists begin to piece together the missing clues: How did the planets form so quickly (at least in cosmic terms)? Did the planets form in their present locations, or did the giant planets form closer to the Sun and, through complex gravitational interactions, migrate to their orbits of today?
The Juno Mission Will Unlock Jupiter's Family Secrets
At more than twice the mass of all the other planets combined, Jupiter is the patriarch of our planet family. It grew large enough to capture and hold onto the materials of the solar nebula, so its mixture of about 90% hydrogen and 10% helium by percent volume (with some methane, water, and ammonia mixed in) reflects the composition of the primordial mixture that produced all the planets. Yet, its composition is not exactly like the primordial mixture, leaving scientists uncertain about how exactly Jupiter, and by extension, the solar system, formed. Better understanding Jupiter's traces of methane, water, and ammonia will help scientists piece together exactly how a collection of gas and dust came to form the planets we see today.
Juno will use sophisticated instruments to spy deep into Jupiter's atmosphere in wavelengths of light invisible to the human eye, and it will gather information about the trace components water and ammonia. By measuring how its orbit is very slightly altered by the gravity of the planet, Juno will infer just how massive Jupiter's core is, which will provide additional clues about how Jupiter captured heavy enough materials in its infancy to grow so large. The very stuff of Jupiter holds clues to understanding the story of our solar system's birth!
Jupiter's Atmosphere –Jupiter's clouds shroud a very turbulent place. The immense pressure of the planet's bulk crushed the interior as it formed (and possibly still does as Jupiter continues to contract) and the resulting heat is still leaking from the planet. Jupiter is far from the Sun, but this internal heat warms the planet and plays a major role in its weather. Jupiter radiates twice as much infrared energy as it receives from the Sun! Its core temperature may be about 43,000ºF (24,000°C) — hotter than the surface of the Sun. This heat leaks up through the liquid metallic hydrogen and liquid hydrogen layers to supply energy to the atmosphere. Like a pot of soup on a hot stove, atmospheric gases boil up from the warm bottom layers to the cooler upper layers; temperatures are–261°F(–163°C) at the top of the atmosphere. Juno will map the atmosphere's temperature at different depths.
While it orbits the Sun only once every 12 years, Jupiter spins on its axis once every 10 hours. The rapidly spinning planet generates five jet streams in each hemisphere that produce Jupiter's unique banded appearance. Earth has only about four dynamic jet streams, two — sometimes three — in each hemisphere, which all travel from west to east. Wind speeds are high, up to 330 miles (530 kilometers) per hour, and alternate direction from eastward to westward with latitude. Lightning, produced as ice particles within storms rub past each other, is frequent. The Great Red Spot is a massive storm system larger than the diameter of Earth that has been raging for at least several hundred years.
Both magnetic fields originate from processes deep in each planet's interior. Earth's is generated from the electric current caused by the flow of molten metallic material within its outer core. Jupiter's gases are crushed to such incredible pressures that they are forced beyond the common states of liquid, solid, or gas that we find on Earth. One such a layer inside Jupiter is metallic hydrogen, and the electric current caused by swirling movements in this substance produces a magnetic field so large that its tail end ("magnetotail") extends past the orbit of Saturn.
Juno will map Jupiter's magnetic field. Its unique polar orbit will carry it above the poles to study Jupiter's auroras and how the magnetic field slams invisible charged particles into the atmosphere to produce the beautiful lights. Juno will measure the charged particles and the electric currents they create along the magnetic field lines. Juno will also "listen" for the radio signals given off by these particles as they move through the magnetic field. Its special "eyes" — an ultraviolet spectrometer — will "see" the aurora in a wavelength of light invisible to our eyes. JunoCam will take pictures of the planet, which scientists and students will use to study the poles.
Jupiter's Moons – Jupiter has its own family of at least 63 moons. Ganymede, the largest of Jupiter's moons, is bigger than the planet Mercury. Scientists suspect that the tiny moons Adrastea, Metis, Amalthea, and Thebe have slowly shed particles to create Jupiter's thin, dark rings.
Cousin Earth's Own Story Continues to Unfold
In the inner solar system, a distinct set of sibling planets formed from the primordial nebula: the inner, terrestrial planets Mercury, Venus, Earth, and Mars. These relatively small, rocky, dense planets lack the thick shroud of gases surrounding each of the giant planets, because they are heated by their closeness to the Sun and the blast of solar wind from the early Sun stripped them of their ices and gases.
The process of accretion that formed the rocky planets — bits and pieces gradually clumping together into larger and larger bodies — also left its mark on the planets and their moons. We can see craters on their surfaces.
Earth's Interior and Magnetic Field – Early in their histories, the accumulated heat from accretion, the continuing decay of their radioactive isotopes, and the energy of countless impacts made the terrestrial planets hot enough to separate into distinct layers (differentiate): Dense materials, like iron and nickel, sank to form cores; medium-density, rocky silicate materials formed mantles; and lighter rocks rose to the surfaces and cooled to form crusts. Earth's outer core is molten. Flow of this hot metallic material produces an electric current that generates our magnetic field.
Earth's Atmosphere – Over time, these planets regenerated their lost atmospheres though volcanic outgassing, with the larger planets, Venus and Earth, holding onto thicker atmospheres. Mars also regenerated an atmosphere, but the smaller planet's interior cooled more quickly. It is no longer outgassing at a sufficient rate; in addition, it no longer has a magnetic field to prevent the solar wind from stripping its gases away. Under the protection of their planet's magnetic field, Venus and Earth each accumulated comparatively thick atmospheres. Earth's was further modified by photosynthesis. Distinct from their giant gaseous cousins, however, the inner planets are mainly made of rock.
We are still uncovering the secrets of our own rocky inner planet, but we use it as the standard of comparison for our exploration of all other planets. Earth spins on its axis once a day and orbits the Sun once a year. All other planets are hot or cold compared to Earth's temperate surface temperatures, which range from about –125° to 130°F(–87° to 54°C). Our atmosphere traps energy from sunlight, creating a greenhouse effect that warms the surface. It also moderates the climate and protects the surface from some damaging components of solar radiation. The rotation axis is tilted, giving Earth its seasons. Earth has water, rock, and tectonic cycles, which are important for renewing nutrients. Earth is the only known planet with life, but we continue to search for other areas in our solar system that might harbor primitive life. Unique among all its siblings, it has a single, comparatively large natural satellite — the Moon.
The other members of our solar system family have their own secrets and delightfully diverse personalities. The following sections provide a brief overview of the other giant planets, the inner planets, as well as the smaller asteroids, dwarf planets, and comets that orbit our Sun. In addition, a table summarizing important statistics can be found in Family Portrait ... in Numbers.
Further information: These presentations are made by NASA scientists and engineers, to provide background information for program providers, and not to be used directly in youth programs. These external resources are not necessarily 508 compliant.
- Juno Mission to Jupiter: Unlocking the Giant Planet Story (7MB PowerPoint)
NASA's Juno Mission
- Jupiter: King of the Planets (6MB PowerPoint)
- Unlocking the Giant Planet Story with NASA's Juno Mission
NASA's Juno Mission
- The Magnetism of Jupiter: Erupting Volcanoes and Dazzling Auroras (13MB)
Dr. Fran Bagenal, University of Colorado at Boulder
- Jupiter Versus the Earth: Composition & Structure (1 MB PowerPoint)
Dr. Randy Gladstone, Southwest Research Institute
- Juno: Changing Views of Solar System Formation (10 MB PowerPoint)
Dr. Paul G. Steffes, Georgia Institute of Technology
- Exploring Jupiter with Radio Waves
Dr. W. S. Kurth, The University of Iowa
- NASA's New Horizons Mission (10 MB PowerPoint)
Steve Vernon, The John Hopkins University, Applied Physics Lab
- Explorers "Guide to the Solar System"
This NASA presentation is available to download in PowerPoint format and use in programs. The site also offers a suggested script as well as supporting activities.
- Exploring the Giant Magnetosphere of Jupiter (387 MB QuickTime Movie)
Dr. Fran Bagenal, University of Colorado at Boulder | 0.843444 | 3.263992 |
What do we know about planetary rings? Quite a lot, actually!
Short version of this blog entry: for everything you ever wanted to know about planetary ring systems, read a new review article by Matt Tiscareno titled, laconically, "Planetary Rings," now available on arXiv. (Thanks to Luke Dones for the pointer.)
And now for the longer version. I most commonly write about papers from Science and Nature for the perhaps not very good reason that those papers are short. Their brevity means that it's pretty easy to wrap my head around an article and write a meaningful post about it in the space of a few hours. Sometimes I write about scientific papers published in Icarus or the Journal of Geophysical Research. These papers are invariably more nuanced and based on a much longer span of research work (so are far more likely to stand up to scrutiny than anything published in Science or Nature), but they also take more time for me to understand and synthesize, usually half a day to a day.
NASA / JPL-Caltech / SSI
This view, acquired with the Sun almost directly behind Saturn, reveals a previously unknown faint ring of material coincident with the orbit of the small moon Pallene. This viewing geometry makes microscopic, icy ring particles brighten substantially. Cassini spent nearly 12 hours in Saturn's shadow on 15 September 2006 making observations like this one. The new Pallene ring is a faint narrow band, about 2,500 kilometers across, between the E ring and the G ring. The view looks down from about 15 degrees above the unilluminated side of the rings. Some faint spokes can also be spotted in the main rings, made visible by sunlight diffusing through the B ring.
And then there are review papers. By their very nature, it's impossible to summarize review papers, because they are themselves summaries of decades -- or even centuries -- of work by numerous scientists. So I never write about them. But I'm moved to write about Tiscareno's new paper because it contains answers to so many questions I've attempted to research on the Web while writing stories, and failed to find useful resources. In just the first few pages I've learned a lot of things that made me go "hmm" or "aha!"
Early in the paper there's stuff about Roche limits. The Roche limit, as Tiscareno defines it, "is the distance from a planet within which its tides can pull apart a compact object....However, the Roche limit does not actually have a single value, but depends particularly on the density and internal material strength of the moon that may or may not get pulled apart."
This much I knew, but in the following paragraphs he discusses Saturn's small ringmoons as little probes of the ring's physical properties. Ringmoons are chunks of solid material that are resistant to being torn apart by tidal forces. Over time they accumulate a surface dusting of very fluffy material, but that stops when the density of the whole thing (solid core plus fluffy coating) reaches the Roche critical density. The unusual persistence and expanse of Saturn's rings results from the fact that their Roche critical density is lower than for any other planet, approaching a density only 40% that of water ice. This, in turn, results from the fact that Saturn's rings have a much higher proportion of ice to rock than any other planet's, which lowers their overall density. (Tiscareno doesn't get into why Saturn's rings are more icy than rocky; a recent paper by Robin Canup proposes that Saturn ate the core of a Titan-sized moon and left its icy mantle in orbit.)
Orbits of Uranus' rings and moons
Uranus' rings and moons form a bullseye of orbital paths around the tilted planets. Two new rings, U1 and U2, were announced in December 2005.
There's some fascinating discussion of the other giant planets' Roche limits and what they imply about the densities of their moons. For instance, if you smashed up Uranus' "Portia group" of moons (Cordelia, Ophelia, Bianca, Cressida, Desdemona, Juliet, Portia, Rosalind, Cupid, Belinda, Perdita, and Puck) and spread their mass over the area of your orbits, you'd get something with roughly the same density as Saturn's A ring. So why are they moons instead of an A ring? Likely because they're denser (rockier) than Saturn's A ring: "This moon system may be very similar in origin to the known ring systems, except that the natural density of accreted objects is larger than the Roche critical density...so that any moon that gets disrupted by a collision (which ought to have happened many times over the age of the solar system) will simply re-accrete."
Planetary rings are often described as being small versions of the kinds of disks from which planets form. The parallel is useful but it's interesting that the two systems, both of which consist of rotating disks of particles orbiting a large central mass, are flat disks for entirely different reasons. Ultimately, planetary ring systems are flat because of the oblate (equatorially bulging) shapes of planets, which creates an asymmetric gravity field around the planets. Stellar debris disks don't have these asymmetric gravity fields. They are flat, ultimately, because of the large angular momentum of the disk itself. While the two systems have different causes, they both wind up with particles orbiting in a preferred plane because collisions among particles damp out any motion perpendicular to that plane. Saturn, uniquely, has one set of rings aligned with the planet's rotation plane (due to Saturn's equatorial bulge) and a much larger, more distant ring aligned with its orbital plane (the Phoebe ring, which is too far from Saturn for the equatorial bulge to have an important contribution to the orbital evolution of its particles).
The paper reviews the reasoning for why there should be rings at Mars and Pluto and why they have been difficult to detect (if they exist at all). It reviews the evidence for rings at Saturn's moon Rhea and why they likely do not exist. It reviews the detectability of exoplanetary rings.
After considering all these cases of known or theorized actual rings, the paper goes on to a more theoretical treatment of the types of rings and the phenomena found within them. It explains the difference between spiral density waves (which are compressional and propagate outward) and spiral bending waves (which are transverse and propagate inward) and why they're cool: "Spiral waves, especially weak ones, are useful structures that can be thought of as in situ scientific instruments placed in the rings." You can get masses of small moons from spiral density waves, and deduce properties of the rings themselves from bending waves, under the right lighting conditions, near the equinoxes.
NASA / JPL-Caltech / SSI / processed by Emily Lakdawalla
Pan and Daphnis and their ring waves
Patterns at the outer edge of the A ring are excited by the gravitational influence of Pan, upper left, and Daphnis, near the bottom. In this image the rings have been brightened relative to the moons. Pan's saucer shape -- common for Saturn's ringmoons -- is obvious. Pan's longest axis always points toward Saturn.
There's a fair amount of mathematics in the article, which I instinctively skip while reading. But when I force myself to go back and read the equations I find they're of a general form that even someone who hasn't written down an equation for 12 years can read. We learn about Keplerian shear, and how the scalloped edges of the Encke gap combined with relatively simple mathematics enabled Mark Showalter and his coworkers to predict the location of, and then discover, the embedded moon Pan in archived Voyager images. We learn about propellers and spokes.
There's more, but like I said, it's folly to attempt to summarize a paper that is itself a summary of the results of four centuries of scientific research. Have you ever looked at Cassini images and tried to figure out what makes those cool structures in Saturn's rings? Have you ever wondered what the difference is between a bending wave and a density wave and a ringmoon wake? Have you ever asked questions like "why doesn't Mars have rings" or "do extrasolar planets have rings?" or "what are they talking about when they discuss 'propellers' in Saturn's rings?" Give this paper a try! You'll also learn about "Propeller Belts" and "frog resonances" and the fact that "The F ring is the granddaddy of narrow dusty ringlets" and it contains "an unseen belt of kilometer-sized moonlets."
NASA / JPL-Caltech / SSI
Giant "propeller" in the A ring
"Propeller" features were first spotted in close-up images of the ring taken by Cassini during its orbit insertion. Scientists determined that they indicate the presence of isolated 100-meter-size objects within the rings -- bodies intermediate in size between things that are named as moons and the innumerable individual particles that make up the rings themselves. This propeller, spotted just after equinox on 13 August 2009, is very bright because it sticks up above the ring plane at a time when the sunlight was coming in at a low angle, resulting in dim illumination of the rings. | 0.917876 | 3.609417 |
NASA unveiled a new atlas and catalog of the entire infrared sky today showing more than a half billion stars, galaxies and other objects captured by the Wide-field Infrared Survey Explorer (WISE) mission.
"Today, WISE delivers the fruit of 14 years of effort to the astronomical community," said Edward Wright, WISE principal investigator at UCLA, who first began working on the mission with other team members in 1998.
WISE launched Dec. 14, 2009, and mapped the entire sky in 2010 with vastly better sensitivity than its predecessors. It collected more than 2.7 million images taken at four infrared wavelengths of light, capturing everything from nearby asteroids to distant galaxies. Since then, the team has been processing more than 15 trillion bytes of returned data. A preliminary release of WISE data, covering the first half of the sky surveyed, was made last April.
The WISE catalog of the entire sky meets the mission's fundamental objective. The individual WISE exposures have been combined into an atlas of more than 18,000 images covering the sky and a catalog listing the infrared properties of more than 560 million individual objects found in the images. Most of the objects are stars and galaxies, with roughly equal numbers of each. Many of them have never been seen before.
WISE observations have led to numerous discoveries, including the elusive, coolest class of stars. Astronomers hunted for these failed stars, called "Y-dwarfs," for more than a decade. Because they have been cooling since their formation, they don't shine in visible light and could not be spotted until WISE mapped the sky with its infrared vision.
WISE also took a poll of near-Earth asteroids, finding there are significantly fewer mid-size objects than previously thought. It also determined NASA has found more than 90 percent of the largest near-Earth asteroids.
Other discoveries were unexpected. WISE found the first known "Trojan" asteroid to share the same orbital path around the sun as Earth. Oneof the images released today shows a surprising view of an "echo" of infrared light surrounding an exploded star. The echo was etched in the clouds of gas and dust when the flash of light from the supernova explosion heated surrounding clouds. At least 100 papers on the results from the WISE survey already have been published. More discoveries are expected now that astronomers have access to the whole sky as seen by the spacecraft.
"With the release of the all-sky catalog and atlas, WISE joins the pantheon of great sky surveys that have led to many remarkable discoveries about the universe," said Roc Cutri, who leads the WISE data processing and archiving effort at the Infrared and Processing Analysis Center at the California Institute of Technology in Pasadena. "It will be exciting and rewarding to see the innovative ways the science and educational communities will use WISE in their studies now that they have the data at their fingertips." (learn more) | 0.876755 | 3.798561 |
It’s taken almost an entire decade of travel, but it’s finally there: Today NASA’s New Horizons spacecraft has made its closest planned approached to Pluto, speeding past it at 31,300 miles per hour and at just 7,750 miles above the surface. Compare that with our moon’s 238,900-mile distance from Earth, and you can imagine the kinds of great photos and data we’re going to get from this mission.
If this were before 2006, we would have said that for the first time, humanity has finally reached and explored all nine planets. But Pluto is (correctly) no longer classified as a planet, now that we know what we know about Kuiper-belt objects. And with that knowledge comes hope that we will learn much more about how our solar system originally formed, among many other things.
“The exploration of Pluto and its moons by New Horizons represents the capstone event to 50 years of planetary exploration by NASA and the United States,” said NASA Administrator Charles Bolden in a statement. “Once again we have achieved a historic first. The United States is the first nation to reach Pluto, and with this mission has completed the initial survey of our solar system, a remarkable accomplishment that no other nation can match.”
Note that the image at the top of this story isn’t by any means the best we’re going to get. It will take at least a few days for data to come back to us from today’s flyby. Even so, the picture above shows us just how much we didn’t know before about Pluto’s appearance, composition, and internal makeup. (Check out the Planetary Society for Emily Lakdawalla’s solid explanation of why even the amazing Hubble Space Telescope couldn’t get us a halfway decent photo of Pluto, either.)
“I’m delighted at this latest accomplishment by NASA, another first that demonstrates once again how the United States leads the world in space,” said John Holdren, assistant to the President for Science and Technology and director of the White House Office of Science and Technology Policy.
“New Horizons is the latest in a long line of scientific accomplishments at NASA, including multiple missions orbiting and exploring the surface of Mars in advance of human visits still to come; the remarkable Kepler mission to identify Earth-like planets around stars other than our own; and the DSCOVR satellite that soon will be beaming back images of the whole Earth in near real-time from a vantage point a million miles away. As New Horizons completes its flyby of Pluto and continues deeper into the Kuiper Belt, NASA’s multifaceted journey of discovery continues,” Holdren said.
New Horizons launched in January 2006 and traveled three billion miles to reach Pluto, “threading the needle” through a 36-by-57-mile window in space — “the equivalent of a commercial airliner arriving no more off target than the width of a tennis ball.” New Horizons arrived 72 seconds earlier than predicted, as well. The next step: Waiting for confirmation that the photos made it to the craft’s onboard memory, which should happen sometime tonight.
For more on the New Horizons mission, read our earlier piece on Pluto’s discovery and the history of our scientific endeavors to understand more about this incredibly distant and fascinating object in our solar system. | 0.897948 | 3.323202 |
The enjoyment of astronomy can be lifelong or just a fad but a lot will depend on how you have your first experience. Tables Astronomy constants, physical constants, planets (orbital properties, bodily traits, atmospheres), 100 nearest stars, and 100 brightest stars as seen from the Earth. Generally called Barnard’s Runaway Star, it is among the finest identified stars within the historical past of astronomy and in fashionable culture.
The nine planets that orbit the sun are (in order from the Solar): Mercury , Venus , Earth , Mars , Jupiter (the biggest planet in our Solar System), Saturn (with large, orbiting rings), Uranus , Neptune , and Pluto (a dwarf planet or plutoid). Our photo voltaic system is positioned within the Milky Method Galaxy, a set of 200 billion stars (along with their planetary programs).
Darkish matter and darkish power are the present leading subjects in astronomy, sixty five as their discovery and controversy originated during the research of the galaxies. From the Center Kingdom, constellations had been often depicted on coffins as star clocks, displaying the size of time stars have been visible or invisible.
If you happen to’d reasonably listen while below the celebrities, obtain our monthly astronomy podcast and take it with you whenever you enterprise out tonight for a guided tour to the night time sky. Moreover you’ll be able to look for different landmarks within the sky, like stars, in an effort to begin explaining the astronomical constellations.
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Modern astronomy is concerned with understanding the character of the universe and the various constructions — galaxies, stars, planets, atoms — inside it. Astronomy is fascinated not only in describing this stuff, however in understanding how they are shaped and how they change, and, ultimately, in reconstructing the historical past of the understanding is always primarily based upon the same set of theories and practices—physics, chemistry, supplies science, mathematics, laptop science—that are used to understand the earth and its instant this reason, college students are strongly encouraged to base their study of the universe upon a firm grounding in certainly one of these disciplines.
Observational astronomy is targeted on buying data from observations of astronomical objects, which is then analyzed using fundamental rules of physics. The research of the bodily universe past the Earth’s atmosphere , including the method of mapping places and properties of the matter and radiation in the universe. | 0.842392 | 3.204097 |
Fireballs explode in Earth's atmosphere all the time, usually unremarkably. And a fireball that exploded over the Australian desert in 2016 might have been mistaken for any other bolide, if not for a network of cameras monitoring the sky to search for just such events.
It was thanks to images taken by these cameras - called the Desert Fireball Network - that astronomers were able to ascertain the fireball was no ordinary exploding space rock.
Instead, velocity data revealed the rock had probably been in orbit around Earth before meeting its fiery end; a phenomenon known as a temporarily captured orbiter, or, colloquially, a minimoon.
There are a whole bunch of rocks out there, zipping past Earth, so it stands to reason that some of them are going to penetrate the atmosphere at some point. Most of these end up as bolides - a meteor that explodes in mid-air before it can reach the ground.
(This is because, scientists think, high-pressure air in front of the falling meteor seeps into cracks in the rock, increasing internal pressure and causing the rock to break apart.)
But every now and again, one of these asteroids gets captured in Earth's orbit for a little while. Not often, though: according to a supercomputer simulation published in 2012 involving 10 million virtual asteroids, only 18,000 got captured in Earth orbit.
We're not sure exactly how many asteroids are out there close to Earth. Estimates put the number in the millions, but as of 30 November 2019, only 21,495 have been discovered. That's because they're small and very hard to see - and this detection difficulty also extends to minimoons.
We've detected temporary moons around other planets - Jupiter is particularly adept at minimoon capture - but here on Earth, minimoon detections are extremely rare.
Prior to the 2016 bolide, we'd only seen two Earth minimoons: an asteroid called 2006 RH120, which orbited Earth for about a year from 2006 to 2007; and a bolide in January 2014, with a low velocity that indicated an orbital origin.
With six cameras spanning hundreds of kilometres across the Australian desert, the fireball that streaked across the sky on 22 August 2016 was observed in great detail. The researchers, led by planetary scientist Patrick Shober of Curtin University in Australia, were able to determine the object's velocity (a slow 11 kilometres per second, or 6.8 miles per second) and trajectory (almost vertical).
The slow velocity indicates that the object had been orbiting Earth, and the angle rules out satellite debris. Based on the team's calculations, there is a 95 percent probability the object was a temporarily captured orbiter.
There is a good reason these objects are interesting. Sending spacecraft to asteroids is time-consuming and costly, and involves some pretty vast distances. If there were an asteroid just hanging around orbiting Earth for a bit, it would be much easier to get to.
It's obviously not possible to send a spacecraft to a rock that has exploded in the atmosphere, but we can study these bolides to try to figure out how and why some asteroids get captured in Earth orbit.
In this respect, the team reports that there's a lot more work to be done.
"We find that the probable capture time, capture velocity, capture semimajor axis, capture [near-Earth object] group, and capture mechanism all vary annually, with most captures occurring during Earth's aphelion or perihelion," they write in their paper.
"We also discover that the probability of capture occurring as a result of a close lunar encounter varies according to the lunar month for this event."
That's a lot of variables. However, with more telescopes coming online in the near future, it's possible more minimoon fireballs will be discovered, helping construct a more complete picture of Earth's minimoon situation at any given time.
"We caution future analysis of possible [temporarily captured orbiter] events to explore the effects of small variations in the initial conditions and various triangulation methodologies," the researchers explain.
The paper has been published in The Astronomical Journal. | 0.869669 | 3.901642 |
Paul M. Sutter is an astrophysicist at The Ohio State University, host of Ask a Spaceman and Space Radio, and author of "Your Place in the Universe." Sutter contributed this article to Space.com's Expert Voices: Op-Ed & Insights.
One of the most surprising discoveries in the past couple decades is the existence of so-called "hot Jupiters," which are giant exoplanets that orbit way too close for comfort to their parent stars. In short, they shouldn't exist. Gas giant planets need a lot of gas to become giant (hence the name), but there isn't a lot of gas near stars. So they must have formed farther out and migrated in like a gaseous moth to a flame. In the process, any icy moons may have become detached and started to disintegrate in the blaze, leading to something that's not quite a moon and not quite a planet — a "ploonet." Detection of these hybrid creatures may tell us how hot Jupiters came to be so hot.
The making of a giant
We might be tempted to think that the majority of solar systems out there in the galaxy look a lot like our own — a small collection of rocky worlds orbiting close to a star, with gassy and icy giants, surrounded by retinues of moons big and small, dominating the outer orbits.
Boy is that wrong.
Astronomers were in for a nasty surprise once they first started detecting planets outside the solar system. The earliest methods depended on detecting the "wobble" of the parent star as one of its children gravitationally tugged it back and forth in the course of its usual orbit. The biggest wobbles will come from bigger planets orbiting at smaller distances.
And guess what: that's exactly what we found.
Big planets — in some cases even bigger than our own reigning heavyweight champion, Jupiter — orbiting in frankly ridiculously close orbits. I'm talking closer than the orbit of Mercury.
In the decades since those first surprising discoveries, we've come to know that these so-called hot Jupiters are actually pretty common. However the heck nature is able to fashion these systems, it's able to do it pretty efficiently.
Related: 7 Ways to Discover Alien Planets
There and not back again
Of course, we're not exactly sure how hot Jupiters get so hot. The main problem is that stars are kind of warm objects, emitting a lot of radiation. In a young planetary system, an infant star is surrounded by a swirling cloud of gas and dust that will eventually coalesce into planets.
Near the star, pulses and outbursts blow away any lingering lighter elements like hydrogen and helium, and the heat turns frozen ice into more pliable water. Thus the inner worlds are dominated by heavier molecules and usually acquire a healthy dose of liquid.
In the colder outer reaches, dirt and rocks and glue together with ices, forming much more massive bodies than can be found inwards. With that enhanced mass, the newly formed planet can really bulk up by slurping on as much gas as it can possibly get its greedy gravitational hands on, building up to truly impressive sizes.
There's usually a bit of shuffling and rearranging as a planetary system starts sorting itself out, with planets moving inward or outward, crashing together, or even getting an unfortunate ejection from the system altogether. Through a mechanism we don't fully understand — possibly involving a complex dance between a newly forming planet and its surrounding gas that flows toward it to continue its feeding — sometimes giant planets barrel inward toward the star, crowding out anybody else.
So one mysterious mechanism pulls the big planets in (sometimes), but another mysterious process has to make the planet stop its inward migration; otherwise it would just go all the way and slam into the star itself. But once in place, the planet can last for at least a few million years. With the intense heat, the hot Jupiter's gaseous atmosphere slowly evaporates, but with so much raw bulk the planet can withstand the assault for some time.
But giant planets don't come alone. Thy have lots of little friends — their moons, usually numbering in the dozens. While most are small and barely qualify as anything meaningful, some can be quite large, as big as Earth's own moon, swathed in layers of rock-hard water ice.
Despite decades of searching, astronomers have not yet confirmed the existence of any exomoons — moons orbiting a planet outside the solar system. If any hot Jupiters have a moon, we haven't seen one.
Did they lose all their moons in the chaotic processes that led to their inward trek? Did the moons detach and fall into the star? Did they instead get ejected from the system altogether?
The likely answer is "yes, usually", but recently a team of astronomers detailed a scenario where the moons not only survive the migration to the hot inside regions of the solar system, but manage to detach themselves from the gravitational grips of their parent planets and orbit the star on their very own.
The team called these objects "ploonets," because why not.
These ploonets, if they survive the travails of their giant parent plants in the transformation from regular Jupiters to hot Jupiters, would be similarly affected by the uncomfortable proximity to the star. All those layers of rock-hard ices become much less rock-hard at those extreme temperatures, and begin evaporating off in a thick haze surrounding the ploonet.
This makes for intriguing observational consequences, as the spectrum of starlight passing through the haze would show an unmistakable signature. A potential close-in small planet may not be a planet at all, but the leftover remnants of an icy moon. Should such a ploonet be discovered, it would tell us that this scenario is not only possible, but viable, giving astronomers a vital clue in the formation of hot Jupiters, and solar systems in general.
- Alien Planet Quiz: Are You an Exoplanet Expert?
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- Magnetic Fields of 'Hot Jupiter' Exoplanets Are Much Stronger Than We Thought
You can listen to the Ask A Spaceman podcast on iTunes and on the Web at http://www.askaspaceman.com. Ask your own question on Twitter using #AskASpaceman or by following Paul @PaulMattSutter and facebook.com/PaulMattSutter. Follow us on Twitter @Spacedotcom or Facebook. | 0.907616 | 3.978166 |
NASA has narrowed to four the number of potential landing sites for the agency’s next mission to the surface of Mars, a 2016 lander to study the planet’s interior.
The stationary Interior Exploration Using Seismic Investigations, Geodesy and Heat Transport (InSight) lander is scheduled to launch in March 2016 and land on Mars six months later.
It will touch down at one of four sites selected in August from a field of 22 candidates. All four semi-finalist spots lie near each other on an equatorial plain in an area of Mars called Elysium Planitia.
“We picked four sites that look safest,” said geologist Matt Golombek of NASA’s Jet Propulsion Laboratory in Pasadena, Calif. Golombek is leading the site-selection process for InSight. “They have mostly smooth terrain, few rocks and very little slope.”
Scientists will focus two of NASA’s Mars Reconnaissance Orbiter cameras on the semi-finalists in the coming months to gain data they will use to select the best of the four sites well before InSight is launched.
The mission will investigate processes that formed and shaped Mars and will help scientists better understand the evolution of our inner solar system’s rocky planets, including Earth. Unlike previous Mars landings, what is on the surface in the area matters little in the choice of a site except for safety considerations.
“This mission’s science goals are not related to any specific location on Mars because we’re studying the planet as a whole, down to its core,” said Bruce Banerdt, InSight principal investigator at JPL. “Mission safety and survival are what drive our criteria for a landing site.”
Each semifinalist site is an ellipse measuring 81 miles (130 kilometers) from east to west and 17 miles (27 kilometers) from north to south. Engineers calculate the spacecraft will have a 99-percent chance of landing within that ellipse, if targeted for the center.
Elysium is one of three areas on Mars that meet two basic engineering constraints for InSight.
One requirement is being close enough to the equator for the lander’s solar array to have adequate power at all times of the year. Also, the elevation must be low enough to have sufficient atmosphere above the site for a safe landing. The spacecraft will use the atmosphere for deceleration during descent.
All four semifinalist sites, as well as the rest of the 22 candidate sites studied, are in Elysium Planitia. The only other two areas of Mars meeting the requirements of being near the equator at low elevation, Isidis Planitia and Valles Marineris, are too rocky and windy. Valles Marineris also lacks any swath of flat ground large enough for a safe landing.
InSight also needs penetrable ground, so it can deploy a heat-flow probe that will hammer itself 3 yards to 5 yards into the surface to monitor heat coming from the planet’s interior. This tool can penetrate through broken-up surface material or soil, but could be foiled by solid bedrock or large rocks.
“For this mission, we needed to look below the surface to evaluate candidate landing sites,” Golombek said.
InSight’s heat probe must penetrate the ground to the needed depth, so scientists studied Mars Reconnaissance Orbiter images of large rocks near Martian craters formed by asteroid impacts. Impacts excavate rocks from the subsurface, so by looking in the area surrounding craters, the scientists could tell if the subsurface would have probe-blocking rocks lurking beneath the soil surface.
InSight also will deploy a seismometer on the surface and will use its radio for scientific measurements. | 0.858809 | 3.501271 |
Scientists have long thought that exoplanets—planets beyond the solar system—were restricted to the confines of our Milky Way. After all, our galaxy is a warped disc about a hundred thousand light-years across and a thousand light-years thick, so it's incredibly difficult to see beyond that. But now, a new study is saying there could be extragalactic exoplanets.
The study, published February 2 in The Astrophysical Journal Letters, gives the first evidence that more than a trillion exoplanets could exist beyond the Milky Way.
Beyond Our Galaxy
Using information from NASA's Chandra X-ray Observatory and a planet detection technique called microlensing to study a distant quasar galaxy, scientists at the University of Oklahoma found evidence that there are approximately 2,000 extragalactic planets for every one star beyond the Milky Way. Some of these exoplanets are as (relatively) small as the Moon, while others are as massive as Jupiter. Unlike Earth, most of the exoplanets are not tightly bound to stars, so they're actually wandering through space or loosely orbiting between stars.
"We can estimate that the number of planets in this [faraway] galaxy is more than a trillion," says Xinyu Dai, the astronomy and astrophysics professor who led the study.
Microlensing works like magnification, says co-author Eduardo Guerras. It's a highly nuanced process that looks at frequencies emitted by moving celestial objects, meant to observe how they distort and magnify light that comes in from the objects near them. This light then illuminates things that aren't otherwise visible.
"This microlensing is amplifying something that is very small and changing colours, which makes no sense," Guerras says, "or it's amplifying a small region of a bigger object and that object has different colours."
Since these objects are so distant—the extragalactic bodies are some 3.8 billion years away—microlensing is the only way to get a sense of their shape. The researchers know they're looking at planets because of the speed at which they're moving.
"You can have this effect with stars, but it would be much, much less likely. It would be way less frequent," Guerras says. "If you have only one planet, the chances of observing it twice is astronomically small."
In Search of Exoplanets
Considering scale, detecting exoplanets can be tricky. Directly viewing exoplanets within the Milky Way is nearly impossible, so astrophysicists have to sift through data and use other detection techniques that give way to evidence of planet signatures. Normally, it takes multiple methods to confirm if there is actually an exoplanet out there, and in some cases, detections have turned out to be false positives.
"These stars are really far away. There's no way you can observe them by any [traditional] means," Guerras says.
The researchers are hoping that with the publication of their study, other scientists will pick up the data and develop another technique to verify whether or not these extragalactic planets exist.
"We hope other teams publish independent analyses to confirm our findings," Dai says. "I think this is a case where scientific discoveries can be triggered by the spark of ideas."
Extra on Exoplanets
Exoplanets have been discovered in our Milky Way galaxy in the past. In fact, 5,287 planets have been confirmed and thousands more could still be out there. Previous efforts have been databased and archived.
In our galaxy, there's about one planet around every star, which means that there could be up to a trillion planets in the Milky Way. Many of these exoplanets could be Earth-size.
Dai says the study opens up the new field of studying starless planets beyond our galaxy, and could help us compare free extragalactic exoplanets with their intragalactic counterparts.
Lead Image: Milky Way from Cerro Paranal observatory in the Atacama Desert, Chile. PHOTOGRAPH BY BABAK TAFRESHI, NATIONAL GEOGRAPHIC CREATIVE | 0.846995 | 3.982494 |
After three weeks of tests, NASA controllers have given the newly upgraded Hubble Space Telescope a clean bill of health. Initial tests are largely complete; however, calibrations of the observatory’s instruments are expected to continue for another two months. Routine science observations have now resumed using the telescope’s Imaging Spectrograph and the Wide Field and Planetary Camera 2.
After three weeks of in-orbit checkout, following its deployment from Space Shuttle Columbia on March 9, the Hubble Space Telescope has been declared healthy and fit by engineers and scientists at NASA’s Goddard Space Flight Center in Greenbelt, Md., and the Space Telescope Science Institute in Baltimore.
Initial checkout of the spacecraft and instruments has largely been completed. However, the calibration process for the instruments will continue for another two months. The new rigid solar arrays, coupled with the new Power Control Unit, are working perfectly, generating 27 percent more electrical power than the old arrays. This increase in power roughly doubles the power available to the scientific instruments. The new reaction wheel is operating normally.
The powerful new Advanced Camera for Surveys (ACS) is now undergoing its final optical alignment and focus checks. The image quality of individual stars observed in a standard calibration field is excellent. The Advanced Camera’s light-sensing detectors are also working very well. It is anticipated that the first Early Release Observations of astronomical targets taken with the Advanced Camera for Surveys will be available around the first week in May.
The new, high-tech mechanical cooler inserted by the Astronauts during SM3B has been working continuously and properly since March 18. The cooler?s intended purpose is to attempt to resuscitate the dormant Near-Infrared Camera and Multi-Object Spectrometer (NICMOS), which depleted its expendable solid nitrogen coolant in January 1999. Although this new ?refrigerator?, dubbed the NICMOS Cooling System (NCS), has been reliably generating the amount of cooling power expected, Hubble engineers report that the NICMOS instrument is cooling down more slowly than originally expected. Because it will take longer to reach the proper operating temperature, below approximately 80 degrees Kelvin, the initial checkout and scientific observations with NICMOS will be delayed for several weeks.
Routine science observations have now resumed with the Space Telescope Imaging Spectrograph and the Wide Field and Planetary Camera 2, the two instruments that were operating on Hubble prior to Servicing Mission 3B. On another note, a gyro (Gyro 3) that had not been performing as well as it should prior to the mission resumed perfect operation after it was turned off and re-started while Hubble was in Columbia’s payload bay.
The Space Shuttle Columbia journeyed to the Hubble Space Telescope for the fourth servicing mission on March 1, 2002. During a series of five spacewalks, Astronauts installed new hardware and upgraded older systems, leaving the telescope better than ever. After a successful mission spanning 11 days in orbit, the shuttle landed safely on March 12 at Kennedy Space Center, Fla.
Original Source: NASA News Release | 0.835602 | 3.227952 |
This might be a good time to look up.
So said writer and physicist André Bormanis. He may be biased, because he has been telling true and fictional stories set in space for more than 25 years. Many of us now have more time, and if you can safely step outside, you can spy the skies and navigate the universe.
“In your imagination, you can travel to different worlds simply by looking up at night,” he said.
Bormanis, who has a master’s degree in science, technology and public policy from George Washington University, served as a science consultant for the “Star Trek” television and film franchise in the 1990s, then went on to write for “Star Trek: Voyager,” “Star Trek: Enterprise” and other series.
He wrote the narration for “Centered in the Universe,” the Griffith Observatory’s long-running planetarium show, and serves as co-executive producer and writer for the Fox/Hulu series “The Orville” and consulting producer for National Geographic’s “Cosmos.”
We asked Bormanis for a beginner’s introduction to the sky —a handful of celestial highlights you can see without a telescope. He gave us seven. All should be visible to the naked eye on a cloudless night, especially if there’s not too much light pollution in your neighborhood. (For his bonus suggestion, No. 7, you might need binoculars.)
“When one looks toward the southwest just after dark, Venus is the most prominent object in the night sky after the moon,” he said. “Venus is currently about 60 million miles away from the Earth. Which means it took the light from Venus about six minutes to hit your eye. You’re seeing Venus six minutes in the past.”
The Pleiades, also in the southwest sky, lie within the constellation of Taurus the Bull. Just after dusk, look a bit below and to the right of the waxing crescent moon (the night of April 25). “That’s an open star cluster 440 light-years away.” Because a light-year is 6 trillion miles, “the light that you’re seeing left that star cluster 440 years ago, which, if I’m correct, is 1580 — 30 years before Galileo first turned a telescope toward the night sky.”
“This is a great time of year to look for Orion. Orion is very prominent low in the southwest. It is facing Taurus the Bull. Orion is trying to slay Taurus the Bull, in fact. … And Orion’s hunting dogs, Canis Major and Canis Minor, are to his left.”
“The brightest star in Canis Major is Sirius, the dog star, and it’s the brightest star in the sky.” To find it, look low in the southwest sky, to the left of Orion. (Venus and Jupiter are brighter, but they’re planets, not stars.)
Betelgeuse marks Orion’s right arm and “has been behaving strangely in recent months. It’s been dimming. It is a red supergiant star, destined to end its life in a supernova explosion. We don’t know when. It will be sometime in the next few hundred thousand years, most probably.”
“If you go out under the predawn sky, Saturn, Mars and Jupiter are doing a little dance in the southeast.” And if you watch them from morning to morning, “you can watch their relative positions changing. We’re all orbiting the sun in the same direction. Mars is the next planet out from Earth, then Jupiter, then Saturn. So it takes Earth one year to go around the sun. It takes Mars a little over two years. It takes Jupiter 12 years. And Saturn, 30 years.”
If you have binoculars, “look beneath the belt of Orion at his sword sheath. One of the ‘stars’ in that sheath will look a little fuzzy. That’s the Orion Nebula, a huge complex of gas and dust where stars are being born. It’s a stellar nursery about 1,500 light-years from Earth.” | 0.92132 | 3.290053 |
Fomalhaut aka Imset, one of the four Royal Stars, is rising in the South!
Fomalhaut b, also known as Dagon, is a confirmed,directly imaged extrasolar object and candidate planet orbiting the A-type main-sequence star Fomalhaut, approximately 25 light-years away in the constellation of Piscis Austrinus. The object was initially announced in 2008 and confirmed as real in 2012 from images taken with the Advanced Camera for Surveys (ACS) on the Hubble Space Telescope and, according to calculations reported in January 2013, has a 1,700-year, highly elliptical orbit. It has a periastron of 7.4 billion km (~50 AU) and an apastron of about 44 billion km (~300 AU). As of May 25, 2013 it is 110 AU from its parent star.
Etymology and cultural significance
Fomalhaut has had various names ascribed to it through time and has been recognized by many cultures of the northern hemisphere, including the Arabs, Persians and Chinese. It marked the solstice in 2500 BC. It was also a marker for the worship of Demeter in Eleusis.
It was called Hastorang by the Persians, one of the four “royal stars“.
The Latin names are ōs piscis merīdiāni, ōs piscis merīdionālis, ōs piscis notii “the mouth of the Southern Fish”.
The name Difda al Auwel comes from the colloquial Arabic الضفدع الأول aḍ-ḍifdiˤ al-’awwal “the first frog” (the second frog is Beta Ceti).
The Chinese name 北落師門/北落师门 (Mandarin: Běiluòshīmén) meaning North Gate of the Military Camp, because this star is marking itself and stand alone in North Gate of the Military Camp asterism, Encampment mansion (see : Chinese constellation). 北落师门 (Běiluòshīmén) westernized into Pi Lo Sze Mun in R.H. Allen’s work.
To the Moporr Aboriginal people of South Australia, it is a masculine being called Buunjill. The Wardaman people of the Northern Territory called Fomalhaut Menggen —white cockatoo.
Fomalhaut/Earthwork B in Mounds State Park near Anderson, Indiana, lines up with the rising of the star Fomalhaut in the fall months, according to the Indiana Department of Natural Resources. In 1980, astronomer Jack Robinson proposed that the rising azimuth of Fomalhaut was marked by cairn placements at both the Bighorn and Moose Mountain Medicine Wheels in Wyoming, USA and Saskatchewan, Canada, respectively.
The New Scientist magazine termed it the “Great Eye of Sauron” due to its shape and debris ring, when viewed from a distance, bearing similarity to the aforementioned “Eye” in the Peter Jackson Lord of the Rings films.
In Walter Tevis’ novel Steps of the Sun, Fomalhaut is visited by the protagonist and two potentially inhabitable planets are found (and described). Parts of Philip K Dick’s novel Lies, Inc (originally titled The Unteleported Man) are set on the fictional planet Fomalhaut IX. Ursula K. Le Guin’s first novel Rocannon’s World is also set on a fictional planet in the Fomalhaut system.
[In astrology, the Royal Stars of Persia are Aldebaran, Regulus, Antares and Fomalhaut. They were regarded as the guardians of the sky in approximately 3000 BCE during the time of the Ancient Persians in the area of modern-day Iran. The Persians believed that the sky was divided into four districts with each district being guarded by one of the four Royal Stars. The stars were believed to hold both good and evil power and the Persians looked upon them for guidance in scientific calculations of the sky, such as the calendar and lunar/solar cycles, and for predictions about the future.
“In Egyptian mythology, Imset (also transcribed Imseti, Amset, Amsety, Mesti, and Mesta) is a funerary deity, one of the Four sons of Horus, who are associated with the canopic jars, specifically the one that contained the liver. Unlike his brothers, Imset is not associated with any animal and is always depicted as human. Isis is considered his protector, and is himself considered patron of the direction of the south.
Spectacular dust ring surrounds ‘whale’s mouth’ star
Astronomers at the University of California, Berkeley, and NASA’s Goddard Space Flight Center have released a rather remarkable Hubble image of a ring of dust around star Fomalhaut, described by New Scientist as resembling “the Great Eye of Sauron”.
Google search: 10/30
Two Suns In The Sky
“NASA have now confirmed a planet located 25 light years away. Just as implied by Nibiru conspiracy theories the planet, named Formalhaut b and three times the mass of Jupiter, is surrounded by a gigantic dust cloud which is the reason for it not showing up using infra-red imaging. Formalhaut b was actually discovered in 2008 but scientists were skeptical due to the fact that the planet didn’t leave an infra-red signature and that the planet’s orbit was too fast – they therefore claimed that it was a dust cloud.” …
“Quick! Name the widest double star in the sky. If you chose Alpha Centauri and its faint, distant companion Proxima (separation 2.2°), you would have been correct … prior to 2013. That year, Eric Mamajek (University of Rochester) and his colleagues announced the discovery of Fomalhaut C, a companion star located a whopping 5.7° northwest of Fomalhaut (Alpha Piscis Austrini) in a different constellation, Aquarius. ” …
Fomalhaut is a star in the Southern Hemisphere in the constellation Piscis Austrinus. At least one planet orbits this bright star: Fomalhaut b, which was dubbed a “zombie” planet by NASA after its 2005 discovery was debunked as gas, and then proven again in 2012. | 0.8672 | 3.104544 |
The moon was first spotted on a plate taken at the Royal Greenwich Observatory on the night of February 28, 1908. Inspection of previous plates found it as far back as January 27. It received the provisional designation1908 CJ, as it was not clear whether it was an asteroid or a moon of Jupiter. The recognition of the latter case came by April 10.
Pasiphae did not receive its present name until 1975; before then, it was simply known as Jupiter VIII. It was sometimes called "Poseidon" between 1955 and 1975.
Pasiphae orbits Jupiter on a high eccentricity and high inclination retrograde orbit. It gives its name to the Pasiphae group, irregular retrograde moons orbiting Jupiter at distances ranging between 22.8 and 24.1 million km, and with inclinations ranging between 144.5° and 158.3°. The orbital elements are as of January 2000. They are continuously changing due to solar and planetary perturbations. The diagram illustrates its orbit in relation to other retrograde irregular satellites of Jupiter. The eccentricity of selected orbits is represented by the yellow segments (extending from the pericentre to the apocentre). The outermost regular satellite Callisto is located for reference.
Pasiphae is also known to be in a secular resonance with Jupiter (tying the longitude of its perijove with the longitude of perihelion of Jupiter).
With diameter estimated at 60 km Pasiphae is the largest retrograde and third largest irregular satellite after Himalia and Elara.
Spectroscopical measurements in infrared indicate that Pasiphae is a spectrally featureless object, consistent with the suspected asteroidal origin of the object. Pasiphae is believed to be a fragment from a captured asteroid along with other Pasiphae group satellites. | 0.877232 | 3.465991 |
BeppoSAX – The enigma of the Gamma-ray bursts
One of the greatest successes of the recent scientific history Italian, BeppoSAX (Satellite per Astronomia X, “Beppo” as the nickname the Italian astronomer Giuseppe Goggles, one of the pioneers of the study of cosmic rays) was born of a collaboration between the Agency Italian Space agency (ASI) and the Netherlands Agency for aerospace programs (NIVR).
Launched on April 30, 1996, BeppoSAX was originally scheduled to stay in operation until 1998. Instead, it remained operational for seven years until April 29 of 2003, when it has been dropped into the Pacific Ocean. More than the duration, it was the fallout of the scientific mission was to be exceptional. Already in 2002, when the mission was drawing to a close, there were more than 1500 scientific publications based on data provided by BeppoSAX.
The fundamental purpose of the mission was to study the cosmic emissions of X-rays, but they were impossible to study from the Earth due to shielding of the Earth’s atmosphere. In particular, it wanted to contribute to the study of those cosmic phenomena that emit radiation at the same time on a wide range of energy levels, groped to understand its mechanisms astrophysicists.
The trump card of BeppoSAX was precisely the spectral coverage (the range of energy levels of emissions observable) particularly wide, which ranged from 0.1 to 200 keV. This was the first mission capable of studying X-ray sources on an energy range as wide. This way SAX could contribute to the study of a wide variety of cosmic phenomena as compact galactic sources, active galactic nuclei, clusters of galaxies, supernova remnants, normal galaxies, stars, gamma ray bursts.
The greatest successes have come from the observation of the Gamma Ray Burst (GRB), ‘flashes’ of very high energy gamma rays coming from the Universe that before this mission, they had always been an enigma to astrophysicists. Revealing the X-ray emission that accompanies the band range, BeppoSAX has allowed the reconstruction of some fundamental pieces of the puzzle. Throughout its life, the satellite observed more than thirty gamma ray bursts, and their appearance was able to launch immediately alert signals to other space or terrestrial instruments. Guided by BeppoSAX observations, astronomers from around the world have discovered that these mysterious gamma-ray bursts come from very remote galaxies, and have an energy equal to that which would be obtained in light annihilating all the mass of our Sun, in a few moments. They are, in other words, the biggest explosions of the Universe after the Big Bang.
The great skill displayed in this field by the scientific and technological Italian (continued with the launch of the satellite for gamma astronomy AGILE) ensured Italy a leading role also in the SWIFT mission, which NASA hopes to permanently solve the mystery of gamma-ray bursts.
AGILE (Astro‐Rivelatore Gamma a Immagini Leggero) is an X-ray and Gamma ray astronomical satellite of the Italian Space Agency (ASI). AGILE’s mission is to observe gamma-ray sources in the universe. Key scientific objectives of the AGILE Mission include the study of: Active Galactic Nuclei (AGN), Gamma-Ray bursts, X-ray and gamma galactic sources, non-identified gamma sources, diffuse galactic gamma emissions, diffuse extra-galactic gamma emissions and fundamental physics. | 0.869042 | 4.007585 |
The most arrogant astronomer in Switzerland in the mid-20th century was a solar physicist named Max Waldmeier. Colleagues were so relieved when he retired in 1980 that they nearly retired the initiative he led as director of the Zurich Observatory. Waldmeier was in charge of a practice that dated back to Galileo and remains one of the longest continuous scientific practice in history: counting sunspots.
The Zurich Observatory was the world capital for tallying sunspots: cool dark areas on the sun’s surface where the circulation of internal heat is dampened by magnetic fields. Since the 19th century, astronomers had correlated sunspots with solar outbursts that could disrupt life on Earth. Today scientists know the spots mark areas in the sun that generate colossal electromagnetic fields that can interfere with everything from the Global Positioning System to electricity grids to the chemical makeup of our atmosphere.
What alienated Waldmeier’s potential Swiss successors was his hostility toward methods other than his own. In the space age, he insisted on counting sunspots by eye, using a Fraunhofer refracting telescope, named after its 18th-century inventor, installed by the first Zurich Observatory director, Rudolf Wolf, in 1849. (With Waldmeier’s legacy uncertain, his assistant walked off with the Fraunhofer telescope and installed it in his garden.) Automated observation—and solar monitoring by satellite—seemed like obvious improvements, far less subjective than squinting.
Yet for all the animosity toward Waldmeier, his method persisted. Sunspots appear in cycles. Their number steadily increases over a period of approximately 11 years, followed by about 11 years of decrease. Waldmeier understood the interpretation cannot be hurried because of the inherent slowness of the cycle itself. “You cannot speed up the process,” says astronomer Frederic Clette, director of the Solar Influences Data Analysis Center, based at the Royal Observatory of Belgium. “If you want to understand the sun, you must keep a record of the cycle continuously over long durations.”
Astronomer William Herschel believed sunspots were portholes into a dark subsolar world where people lived beneath the sun’s radiant sheath.
The best way to ensure data remains consistent, explains Clette, is to employ a method of observation that links the past and present. In contrast to most new science, which progresses in tandem with technological developments, the most stable apparatus for detecting change in the star that gives us life is the human brain and eye.
“Modern techniques and equipment are powerful, but the technologies span over only a few solar cycles, so they don’t show how cycles differ over centuries,” says Clette, who is the custodian of the worldwide sunspot count, begun by Wolf in Zurich, and now known as the International Sunspot number. Under Clette’s watch, blemishes are still counted by eye. “When we count by eye, what we observe now can be connected to what was observed in the distant past.”
It’s a remarkable story, says Clette. One of the most enduring scientific methods is simply observing. “It’s a long and systematic evolution of accumulating information that has led to an understanding of the sunspot phenomenon, and the jewel on the crown, the ability to predict the future.”
The observation of sunspots predates modern astronomy by at least three millennia. Since the sun was central to several ancient religions, any blemish was sure to be seen as significant. For ancient Africans living on the Zambezi River, sunspots were mud spattered in the face of the sun by a jealous moon. Ancient Chinese saw sunspots as the building blocks of a floating palace or even brushstrokes signifying the character for king. Virgil was more practical. “When [the sun] has checkered with spots his early dawn ... beware of showers,” he warned in his Georgics.
Galileo studied sunspots more scientifically, seeing them as useful markings to calibrate his study of the solar disc. From careful telescopic observation of their daily changes in appearance, he correctly deduced that the sun was spherical and rotated on its own axis, carrying the mutable blemishes with it. But to his eyes, and those of other early astronomers, the meandering of sunspots seemed random. That left plenty of opportunity for speculation: Philosopher Rene Descartes thought the spots were oceans of primordial scum. Astronomer William Herschel believed they were portholes into a dark subsolar world where people lived beneath the sun’s radiant sheath.
Yet there was one amateur astronomer who was simply content to watch the sky and document what he saw. An apothecary by trade, Heinrich Schwabe started observing the sun in 1826, and did so continuously, more than 300 days a year, for four decades. Initially he was searching for undiscovered planets inside Mercury’s orbit. Finding nothing solid, his focus gradually shifted to the speckled solar surface.
By 1844, having counted tens of thousands of spots, Schwabe grew convinced that there was a cycle to the blotchiness: The number of sunspots seemed to wax and wane every 10 years. He had no explanation, but reckoned that others might learn from his observation, so he published a page-long note in Astronomische Nachrichten. His paper was read by Rudolf Wolf, the 30-year-old director of the Bern Observatory. When Wolf took over as director of the Zurich Observatory in 1864, he decided to make the sunspot cycle a focus of study.
Wolf was not content to count only forward in time. To determine whether there truly was a cycle, and to get its true measure, he shrewdly sought to collect past data—starting with Schwabe’s—and to integrate it with his own daily observations.
The trouble was the figures didn’t sync. Their numbers didn’t match even when they counted on the same day, as they did thousands of times between 1849 and Schwabe’s final count in 1868. Wolf’s Fraunhofer telescope was considerably more powerful than Schwabe’s old instrument, revealing that many of Schwabe’s spots were actually clusters. To compensate, Wolf made two crucial decisions. The first was to censor his count—tallying clusters instead of individual spots—reasoning that the relative amount of sunspot activity was what really mattered. Wolf’s second important decision was to establish a ratio between himself and Schwabe by comparing their counts on days that both men observed the sun. That gave him a coefficient he dubbed k, a multiple that could be applied to all of Schwabe’s pre-1849 observations, statistically aligning them with Wolf’s newer data.
Climatologists want to know whether little ice ages are caused by periods when the sun is spotless, as was the case in the 18th century.
The coefficient permitted something even more remarkable. By a series of coincidental overlaps in observation, Wolf could work his way back from Schwabe to establish k coefficients for other scientists, and reliably extend his sunspot data all the way to 1700. Wolf then created a continental network of sunspot counters, and their daily tallies, ranging from zero to a couple hundred, became one of the most reliable datasets in astronomy.
The data showed that Schwabe was right about the sunspot cycle, but not its duration. At first Wolf recalculated the period to 11 years, which led him to believe he’d discovered the cause: Eleven years is the time it takes Jupiter to orbit the sun. Yet the more sunspot cycles he collected, the less plausible his correlation seemed. Some cycles were as long as 14 years. Others were as short as nine. Since Jupiter’s orbital period was invariant, he had to concede defeat.
He kept counting, confident that someone would figure out the sunspot mechanism given enough data. He counted all the way up to his death in 1893. By then his assistant, Alfred Wolfer, had been counting alongside him for 17 years. Their k coefficient made the observational transition seamless to subsequent directors at the Zurich Observatory, including the haughty Waldmeier, who developed an evolutionary classification of sunspots, and method of forecasting geomagnetic storms, that greatly advanced solar science.
So why are there periods of dark spottiness followed by periods when the sun is clear? “The truth is that we still don’t know for sure what causes the periodicity,” admits Clette. Even with 315 years of sunspot data, the inner workings of the sunspot cycle have yet to be illuminated in full.
Still, a lot of progress has been made since Schwabe’s era, notably on the impact of the solar outbursts. In 1859, two amateur astronomers in Wolf’s observational network noticed two bright flares inside a cluster of sunspots. Over the following days, telegraph service was disrupted and auroras could be seen across Europe. Several episodes convinced scientists that there was a connection, the explanation for which came in 1908 when astronomer George Ellery Hale used a spectroscope to determine that sunspots are magnetic. (Magnetism subtly interferes with the color spectrum.) The sun’s dark blemishes could finally be understood. They weren’t primordial scum or signs of solar habitation, but areas where magnetism suppressed the movement of heat through the sun, a process known as solar convection.
Today, thanks to solar physics, we know the sunspot cycle is driven by the rotational motion of plasma within the spinning sun. Because the plasma is electrically charged, and layers of plasma rotate at different speeds, the solar sphere behaves like a dynamo, producing electromagnetic fields that are thousands of times stronger than Earth’s polar magnetism. The circulation of plasma that creates a solar dynamo is now being modeled on supercomputers. Centuries of sunspot data help scientists to refine and validate those models by running simulations, seeing which models most closely match the varying periodicity of successive cycles. And the more perfect models become, the better the sunspot cycle itself will be understood.
The urgency for counting sunspots, explains Clette, has only increased as we’ve moved from an era of telegraphs to satellites. “The sunspot number helps establish the trend over the coming months and years for predicting the frequency and magnitude of disturbances,” he says. The Royal Observatory of Belgium receives regular requests for data from telecommunications and power companies. Commercial airlines also depend on sunspot trends because solar magnetism affects the rate at which radio waves pass through the ionosphere, warping GPS coordinates. If solar weather is trending toward storminess, pilots will shift their attention to alternative navigational instruments.
There also are more speculative correlations between sunspots and life on Earth. Medical researchers are keen to find connections between solar magnetism and cancer. Economists look for relationships between sunspot cycles and agriculture. And climatologists want to know whether little ice ages are caused by periods of “grand minimum”—when the sun is almost spotless—as was the case in the early 18th century. (Period paintings show people ice skating on the Thames and Venice’s lagoons.)
Progress in climatology is especially compelling. Solar radiation is known to change the chemistry of the upper atmosphere, and sunspots are known to modulate the intensity of different wavelengths—from infrared to X-rays—bombarding our planet. By linking the sunspot number to variations in the solar spectrum, climatologists will soon be able to deduce the spectral signature of the sun during the 18th-century grand minimum.
It’s an application that Wolf could never have anticipated, and a lesson to would-be Wolfs present and future: Solving one of the most pressing problems in contemporary science—how the global climate changes—will depend on data collected long before the problem was known. “I think it’s the essence of scientific research when you observe a new phenomenon that you cannot understand,” says Clette. “It’s like discovering a new territory. You know that new knowledge will be gained, even if it comes from different directions than you expect.”
Explaining the sunspot cycle would be the ultimate vindication of Wolf’s multi-century gambit. Yet in his role as custodian of sunspots, Clette is as jubilant about another breakthrough: He has recently established contact with the man who inherited Wolf’s instruments from Waldmeier’s renegade assistant. Observations from the old Fraunhofer telescope are once again contributing to the international sunspot count.
Clette’s elation is not at all sentimental, but celebrates Wolf’s central role in making sunspot counting consistent. “I’ve been able to establish the k coefficient on the telescope,” he says. “It matches perfectly what Wolf established in the 19th century—and keep in mind that the present observer is not Wolf. The matching k coefficient is an indication that the eye-brain system hasn’t evolved in the past couple centuries.”
And if the past couple centuries are a good measure, then simple observation will be viable far into the future. The sunspot count can be a model for any study that requires ultra-long-term data collection, such as the subtle changes in an ancient star’s behavior in the thousands of years before a supernova. Spanning tens or hundreds of generations, a supernova study would make sunspot counting seem as quick as scoring a baseball game.
This experiment in deep time will be an epic challenge. It will depend on statistical cleverness worthy of Wolf and stubborn traditionalism worthy of Waldmeier. Yet to reach its fullest potential, it will take the placid mindset of Schwabe, who didn’t need to know what would eventually be found in his data, only that there was merit in observing.
Jonathon Keats is a writer, artist and experimental philosopher based in San Francisco and Northern Italy. His new book, on the legacy of Buckminster Fuller, will be published by Oxford University Press next year.
The lead photocollage was created from an image from NASA. | 0.835101 | 3.830034 |
From past so many years Astrologers have and are still saying that the position of planets affects the personalities and feelings of a person. Even though this fact lacked scientific proof, but now it turns out that the alignment of planets does influence a few things on earth. As George Dvorsky reports for Gizmodo, another investigation gives a physical verification which expresses that Venus and Jupiter’s gravity can cause a move in earth’s orbit; and swings in its climate every 405,000 years. Astronomers who have given long hypothesis regarding other planets effect of earth’s orbit lacked scientific and physical evidence.
Astronomers who have given long hypothesis regarding other planets effect of earth’s orbit lacked scientific and physical evidence. A new study which was published in the Proceedings of the National Academy of Sciences, demonstrates the impact of our planetary neighbor’s drag using a 1.500 foot rock core which was gathered in 2013 from a butte in Arizona’s Petrified Forest National Park and cores from the site of old lake beds in New York and New Jersey.
The samples taken from these sites were around 6 centimeters in breadth across and around 500 meters long. The more profound the analysts went, the deeper they went, and the more they went back in time where they finally entered the Triassic Period, the age of dinosaurs. By analyzing the samples, the team recorded long-term information on inversion of the magnetic poles of the Earth. These periodic however unusual inversions can be found in residue containing zircon minerals with uranium, which can be used for radiocarbon dating, empowering the example to fill in as a clock.
These periodic however unpredictable inversions can be seen in sediments containing zircon minerals with uranium, which can be utilized for radiocarbon dating, enabling the sample to serve as a clock. Climate changes have been observed in sediments in the form of alternating periods of dry and wet weather. As noted in the study, these samples were correlated with a remarkably continuous cycle going back nearly 215 million years to the Triassic time frame.
“Climatic cycles are directly identified with how the Earth rotates around the Sun, and slight variation in sunlight reaching earth which leads to climate and ecological changes,” the scientist said in an announcement, taking note of in passing that Earth’s orbit is growing by around 5% at regular intervals.
As noted in the investigation, Venus, the planet nearest to Earth, and Jupiter, the largest planet in the nearby planetary group, appear to influence our orbital direction because of their combined severity and this happens every 405,000 years. Therefore, the scientist recommends that occasional changes on Earth could then be more pronounced; creating hotter summers, colder winters, wetter stormy seasons and more parched dry seasons. Right now, our planet is amidst the cycle, with the last major orbital impact happening around 200,000 years ago. | 0.828152 | 3.376424 |
“When you look at the stars and the galaxy, you feel that you are not just from any particular piece of land, but from the solar system.” —Kalpana Chawla, Astronaut
It’s easy to get caught up in the day-to-day struggles of being down here on Earth. We’re only Earthlings, after all, and all the comings and goings, highs and lows of life down here… well, they’re all we really know. Of course, it all seems incredibly important to us. We’re focused on our own experiences.
But there’s a whole solar system out there! There’s an almost uncountable number of stars beyond our own. Earth might seem unique right now, but every day scientists and astronomers are peering deeper into the blackness around us, and discovering more and more planets that just might be something like our own. And for all we know, we’re not the only ones looking…
Here are 42 perspective-altering facts about our solar system that you might not have known.
42. What’s in a Name?
When most people think of “the solar system,” they think of the planets and moons surrounding the Sun, but there’s a lot of solar systems out there. The Sun is just another star, and every star in the sky has gravity that attracts different celestial objects to it.
Every single star that you can see could have its own solar system. Think about that next time you’re looking out at the night sky.
41. You Thought the Pyramids Were Old
By studying moon rocks (which are some of the oldest objects we can find) scientists have estimated the age of our solar system to be somewhere around 4.5 billion years old.
How did our solar system start, you might ask? Read on, brave scientist. It’s a pretty incredible story…
40. Still Young
First, though, it’s important to give some context. Our solar system might seem old, but it is actually still pretty new to the universe.
Yes, it’s been around for 4.5 billion years… but it’s also estimated that the universe itself is 13.8 billion years old.
That’s right. Old as we might think our neighborhood is, it’s basically a new development in the city that is our universe. The universe existed for over 9 billion years before our Sun even started to form.
39. Looking Cloudy
Before there were asteroids, planets, or even the Sun, our solar system began as a massive cloud of gas and dust particles floating in space. This cloud is called a “solar nebula,” and you can see other nebulae in space today if you have a good enough telescope.
38. Where Did It all Start?
Eventually, the giant cloud of dust that existed before our solar system began to collapse. The Sun began to form at the centre of this cloud, and it started getting bigger and bigger, like a snowball rolling down a hill. The initial collapse, from nebula to early solar system, probably only took around 100,000 years, which is like the blink of an eye as far as the universe goes.
37. Spinning Disks
As the solar nebula formed into the Sun, it began to spin and form together into an enormous flat circle called a “circumstellar” or “protoplanetary” disk. This massive ring of matter would get flatter and flatter as the solar system spun, and out of that disk the planets would eventually form.
36. Orbits Around Orbits Around Orbits
Most people know that the planets orbit around the Sun, but did you know that the Sun itself is moving too? The solar system is part of the Milky Way, and it’s orbiting a supermassive blackhole at the centre of the galaxy. That means the Sun is constantly moving at around 220 km per second, and we’re just being towed along.
35. You Thought Pluto Was Far
A lot of maps of the solar system end around Pluto, but it goes out much further than that. Pluto is about 3.67 billion miles from the Sun, and edge of our solar system is still around 1,000 times farther away than that!
Pluto and Charon
34. One Massive Star
When it formed, the Sun consumed the vast majority of matter in the solar nebula that came before it. Despite how large the solar system is, 99.86% of its mass is contained in the Sun. Most of the rest is in Jupiter, Saturn, Uranus, and Neptune, and the rocky planets like Earth consist of just the tiniest fraction of the total mass.
33. Nuclear Power
Ever wonder what the Sun is exactly? It’s actually a giant nuclear reactor, where hydrogen atoms fuse to become helium. This reaction creates an absolutely huge amount of power. Just a tiny amount of that energy reaches the Earth, but it’s still enough to meet all of humanity’s power needs in just two minutes if it could all be harnessed.
There’s only so much hydrogen in our Sun to keep it going, and eventually it will fuse all of it into helium. But don’t worry, the sun has enough hydrogen to keep burning for around 5 billion more years, and since it’s been going for about 4.5 billion years already, it’s right in the middle of its lifespan.
31. Just Like in Fairy Tales
There are many different kinds of stars. Our Sun is called a yellow dwarf, and it will continue to be one for another 5 billion years or so, at which point it will expand and become a red giant.
30. Recipe for a Star
The vast majority of the Sun is made up of hydrogen (~70%) and helium (~28%). Another 1.5% consists of carbon, nitrogen and oxygen, and then the final 0.5% is split between various other elements.
29. Giant of the Solar System
The Sun is far, far bigger than anything else in the Solar System. Its diameter is 864,575.9 miles, meaning you could fit 1 million Earths inside of it.
28. Hot Hot Hot
The reason we can feel the Sun’s heat all the way from the earth is because it’s hot. Really hot—around 9932ºF at the surface— but that’s nothing compared to its core, where it gets as hot as 27 million ºF.
27. It’s All Relative
Our Sun is the biggest thing in our solar system, but there are stars in the universe that get much, much bigger. It all depends on the conditions that led to a star’s formation. Although the Sun is considered to be of average size, the largest star currently known, UY Scuti, has a radius that’s 1,700 times bigger than our Sun. But since it’s not nearly as dense, it only has 30 times as much mass.
26. Close to Perfect
There’s only a difference of about 6 miles when you compare the polar diameter (north/south) to the equatorial diameter (east/west) of the Sun. That’s pretty impressive when you consider how huge it is. It’s actually the closest thing to a perfect sphere that’s ever been found in nature.
25. They Call Me a Wanderer
The origin of the word “planet” is the greek word planetes, which means “wanderer.” The Greeks called planets this because unlike the stars that stayed in place, the planets wandered across the night’s sky.
24. Laws of Attraction
If the solar system was originally just a huge disk of matter, what made that matter turn into planets? Through a process called accretion, the matter in that disk began to clump together until those clumps were large enough to have gravity. That drew in more and more matter until eventually all of the planets and other celestial objects were formed, leaving mostly empty space between them. Nonetheless, there are other competing and/or concurrent theories that help explain the gas giants, which are formed slightly differently than this, and other phenomena of our Solar System.
23. Let’s See What You’re Made Of
Not all the planets are made of the same stuff. The inner planets (Mercury, Venus, Earth, and Mars) are mostly made of rock and different minerals. But the outer planets, the “gas giants” (Jupiter, Saturn, and “ice giants” Uranus and Neptune) are made of, you guessed it, gases such as helium and hydrogen.
22. Some Planets Never Learned to Share
When they were young, the “gas giants” were likely rocky like the rest of the planets. However, they formed earlier than the inner planets and collected much, much more mass than the closer planets. That’s why even the smallest of them, Neptune, still has a radius around four times as large as the Earth’s. The biggest, Jupiter, is 2.5 times more massive than all the other planets combined.
21. Strong Winds
Why are the planets beyond Mars so much bigger than the rest? One answer is solar wind. There was a huge amount of hydrogen and helium, the lightest elements, in the solar system when it was new. When the Sun was forming, solar wind pushed almost all of the hydrogen and helium that was left over very far away. The less common, heavier elements weren’t pushed quite so far, and that’s why the small, rocky planets are close, while the massive, gassy planets are far.
20. Oldest and Biggest
Studies of meteorites show that Jupiter is likely the oldest planet, having begun to form less than a million years after the solar system began. After just 2 or 3 million more years, it was already 50 times the mass of Earth.
19. The Youngest Siblings
Though scientists aren’t sure which of the planets is the youngest, they’re quite sure that the four rocky planets closest to the sun (Mercury, Venus, Earth, and Mars) began to form last, when the Sun was a little older and less reactive than when it was brand new.
18. Sorry Everyone, But Pluto’s Not a Planet
To be a planet, an object needs to meet three criteria: It needs to orbit the sun, it needs to be mostly spherical, and it needs to have cleared the neighborhood of its orbit. That means that, aside from moons, everything else in its orbit should have been absorbed into it by gravity when it was being formed. Every planet did this, but Pluto didn’t. There are still a lot of other objects in the neighborhood of its orbit, so it’s not a planet. Don’t @ us.
17. Like a Planet, But Different
Pluto is one of many dwarf planets in the solar system. That means it meets only the first two criteria of a planet: it orbits the sun (ie. doesn’t orbit another planet like the moon) and is mostly spherical. On top of Pluto, there are four other recognized dwarf planets: Ceres, Eris, Makemake, and Haumea, but scientists believe there may be as many as 100 of them in our Solar System.
16. It Came From Planet 9!
We still don’t know everything about the solar system. Based on the way some objects far beyond Pluto orbit the sun, astrologers have hypothesized that another real planet, the so-called “Planet Nine,” exists, almost invisible and 20 times farther out than Neptune.
15. No Spring Chicken
Although it isn’t the oldest planet in the solar system, the Earth still started forming not long after the Sun was born, around 4.5 billion years ago. Scientists made this estimate by dating rocks and meteorites found all over the world.
14. Not Always a Blue Planet
Around two thirds of the Earth today is covered by water, but it wasn’t always that way. When the Earth was brand new, its entire surface was molten rock. There was no atmosphere, no water, and it was constantly being battered by meteorites and asteroids.
13. A Part of Us
Scientists currently believe that early in the Earth’s history, a massive rock the size of Mars collided with it. That sent a huge amount of debris spinning out into space, and over the years the debris eventually formed into the moon.
12. One Big Precious Gem
Almost every element on Earth is rare by solar system standards. By far the majority of the solar system is made up of hydrogen and helium, while the iron, oxygen, silicon, magnesium, sulfur, nickel, calcium, sodium, and aluminum that make up the Earth are extremely uncommon almost everywhere else.
11. Four Big Asteroids
There are millions of asteroids more than a kilometer wide in the asteroid belt between Mars and Jupiter, but half of the mass of the entire belt is in just three asteroids, Vesta, Palla, and Hygiea, and one dwarf planet, Ceres.
10. Not So Fast George Lucas!
Because of movies like Star Wars, most people assume that the Asteroid Belt is completely crowded with the giant rocks, but that’s not the case. True, there are millions of asteroids in the belt, but it covers such a broad area that chances are if you flew through it you’d never even see one, let alone crash into something.
9. Skipping Stones
Even though there are over a million asteroids in the asteroid belt that are at least a kilometer across, that doesn’t actually mean they’re that common. The vast majority of objects in the region are the size of pebbles.
8. Close But No Cigar
One leading theory as to why the asteroid belt between Mars and Jupiter formed is that early in the life of the solar system, a planet started to form in the region, but the pull of Jupiter’s gravity was too strong to let it happen. So instead, the matter in the area just formed millions of small asteroids and meteorites.
7. Plenty of Belts to go Around
The asteroid belt between Mars and Jupiter is the most well known, but it’s not the only one in the solar system. Starting around the orbit of Neptune and extending for around 20 astronomical units (the distance from the Earth to the Sun), the Kuiper Belt is a massive, ring shaped region of space that likely contains hundreds of thousands of icy objects, leftovers from the formation of the sun and the planets. That’s where you’d find Pluto if you went looking.
6. Can You Spell That?
If you were to go 2,000 astronomical units away from the Sun, way beyond the Kuiper Belt, scientists believe there is something called the Oort Cloud. When the planets first first formed, their gravity sent millions of icy objects out to the very edge of the solar system, and the Oort Cloud was created.
5. The Land of the Comets
There are generally two kinds of comets: short-period comets that come around more often than every 200 years and long-period comets that come around less often than every 200 years. Astrologers believe that most short-period comets come from the Kuiper Belt while most long-period comets come from the Oort Cloud.
4. Galactic Proportions
Our Sun and entire solar system are just the tiniest fraction of the Milky Way, an enormous, rotating galaxy that’s 100,000 lightyears across (for perspective, a single lightyear is around 5.9 trillion, or 5,900,000,000,000 miles). But galaxies get even bigger—one called M87 is 980,000 lightyears in diameter!
3. Not So Unique
We still have a lot to learn about our own solar system, but it’s far from the only one out there. In the Milky Way alone, it’s estimated that there are around 100 billion stars, each with their own solar system that probably formed in a similar way to ours.
2. So Close But So Far
Although we share the Milky Way with so many other stars, even the closest stars are really, really far away. The average distance between stars is around five lightyears or 30 trillion miles.
1. Beyond Comprehension
It’s hard to wrap your mind around 100,000,000,000 different stars in the Milky Way, but that’s just the tip of the iceberg. In 1995, the Hubble Telescope was aimed at a tiny portion of sky for 10 days, and it found more than 3,000 entire galaxies. This picture was called “Hubble Deep Field,” and based on more images like it, scientists estimate that there are likely at least 100,000,000,000 galaxies in the Universe, each of them with billions and billions of stars.
All of these dots are not stars, but galaxies. | 0.864714 | 3.12823 |
This week’s photo, from NASA, we see two galaxies experiencing a close encounter:
The spiky stars in the foreground of this sharp cosmic portrait are well within our own Milky Way Galaxy. The two eye-catching galaxies lie far beyond the Milky Way, at a distance of over 300 million light-years. Their distorted appearance is due to gravitational tides as the pair engage in close encounters. Cataloged as Arp 273 (also as UGC 1810), the galaxies do look peculiar, but interacting galaxies are now understood to be common in the universe. In fact, the nearby large spiral Andromeda Galaxy is known to be some 2 million light-years away and approaching the Milky Way. Arp 273 may offer an analog of their far future encounter. Repeated galaxy encounters on a cosmic timescale can ultimately result in a merger into a single galaxy of stars. From our perspective, the bright cores of the Arp 273 galaxies are separated by only a little over 100,000 light-years. The release of this stunning vista celebrates the 21st anniversary of the Hubble Space Telescope in orbit. | 0.895022 | 3.145109 |
New research lends credence to an unorthodox retelling of the story of early Earth first proposed by a geophysicist at Scripps Institution of Oceanography at UC San Diego.
In a study appearing March 15 in the journal Earth and Planetary Science Letters, Scripps Oceanography researchers Dave Stegman, Leah Ziegler, and Nicolas Blanc provide new estimates for the thermodynamics of magnetic field generation within the liquid portion of the early Earth's mantle and show how long that field was available.
The paper provides a "door-opening opportunity" to resolve inconsistencies in the narrative of the planet's early days. Significantly, it coincides with two new studies from UCLA and Arizona State University geophysicists that expand on Stegman's concept and apply it in new ways.
"Currently we have no grand unifying theory for how Earth has evolved thermally," Stegman said. "We don't have this conceptual framework for understanding the planet's evolution. This is one viable hypothesis."
The trio of studies are the latest developments in a paradigm shift that could change how Earth history is understood.
It has been a bedrock tenet of geophysics that Earth's liquid outer core has always been the source of the dynamo that generates its magnetic field. Magnetic fields form on Earth and other planets that have liquid, metallic cores, rotate rapidly, and experience conditions that make the convection of heat possible.
In 2007, researchers in France proposed a radical departure from the long-held assumption that the Earth's mantle has remained entirely solid since the very beginnings of the planet. They argued that during the first half of the planet's 4.5-billion-year history, the bottom third of Earth's mantle would have had to have been molten, which they call "the basal magma ocean." Six years later, Stegman and Ziegler expanded upon that idea, publishing the first work showing how this once-liquid portion of the lower mantle, rather than the core, could have exceeded the thresholds needed to create Earth's magnetic field during that time.
The Earth's mantle is made of silicate material that is normally a very poor electrical conductor. Therefore, even if the lowermost mantle were liquid for billions of years, rapid fluid motions inside it wouldn't produce large electrical currents needed for magnetic field generation, similar to how Earth's dynamo currently works in the core. Stegman's team asserted the liquid silicate might actually be more electrically conductive than what was generally believed.
"Ziegler and Stegman first proposed the idea of a silicate dynamo for the early Earth," said UCLA geophysicist Lars Stixrude. The idea was met with skepticism because their early results "showed that a silicate dynamo was only possible if the electrical conductivity of silicate liquid was remarkably high, much higher than had been measured in silicate liquids at low pressure and temperature."
A team led by Stixrude used quantum-mechanical computations to predict the conductivity of silicate liquid at basal magma ocean conditions for the first time.
According to Stixrude, "we found very large values of the electrical conductivity, large enough to sustain a silicate dynamo." The UCLA study appeared in the Feb. 25 issue of Nature Communications.
In another paper, Arizona State geophysicist Joseph O'Rourke applied Stegman's concept to consider whether it's possible that Venus might have at one point generated a magnetic field within a molten mantle.
These new studies are signs that the premise is starting to take hold, but is still far from being widely accepted.
"No one is going to believe it until they do it themselves and now two other highly esteemed scientists have done it themselves," said Stegman.
"The pioneering studies of Dave Stegman and his collaborators directly inspired my work on Venus," said O'Rourke. "Their recent paper helps answer a question that vexed scientists for many years: How has Earth's magnetic field survived for billions of years?"
If Stegman's premise is correct, it would mean the mantle could have provided the young planet's first magnetic shield against cosmic radiation. It could also underpin studies of how tectonics evolved on the planet later in history.
"If the magnetic field was generated in the molten lower mantle above the core, then Earth had protection from the very beginning and that might have made life on Earth possible sooner," Stegman said.
"Ultimately, our papers are complementary because they demonstrate that basal magma oceans are important to the evolution of terrestrial planets," said O'Rourke. "Earth's basal magma ocean has solidified but was key to the longevity of our magnetic field."
The Scripps Oceanography study was funded by the National Science Foundation, the U.S. Department of Energy, and a UC San Diego SEED Fellowship. | 0.816608 | 3.57569 |
A more realistic simulation of the black hole featured in the movie Interstellar. (Credit: James et al./IOP Science)
In the 2014 movie Interstellar, astronauts investigate planets orbiting a supermassive black hole as potential homes for human life. A supermassive black hole warps surrounding space-time, according to Einstein’s theory of general relativity, and at least one of the planets in the movie, called Miller’s planet, experienced time passing at a slowed-down rate. For each hour the astronauts spent on the planet, several years passed outside the black hole’s influence.
The time shifting would dramatically affect whether a planet near a supermassive black hole could support life, according to a new paper posted to the preprint server arXiv. General relativity’s time warp affects not only the passage of time, but also the kind of light reaching the planet, with implications for any life there.
Though the likelihood that a habitable planet would orbit a supermassive black hole is unclear, thought experiments like these are helpful for better understanding the universe, says the paper’s author, Jeremy Schnittman.
“It’s a little bit whimsical, it’s a little bit tongue-in-cheek,” says Schnittman, an astrophysicist at NASA’s Goddard Space Flight Center. “But it helps us think about the way the universe works. So even if there really is no such thing as a planet around a black hole, it’s still fun to think about.”
A New Kind of “Habitable Zone”
When astronomers think of potential extraterrestrial life, they often define a “habitable zone” in a planetary system where conditions might support life. These zones usually mark where in a planetary system temperatures could allow for liquid water, which depends on factors including how much light the system’s star emits and how far a planet is from it.
It’s also possible to define habitable zones around supermassive black holes, Schnittman says — if planets orbiting these types of black holes exist. However, any such planets would get their light and warmth from sources other than sunlight.
For example, these black holes would probably have accretion disks, the hot halos of gas and matter that collect around massive black holes. These disks can be very bright and could provide light to orbiting planets, though it would likely be very different from sunlight on Earth.
When Schnittman watched Interstellar, the time warping on Miller’s planet got him thinking about other effects a planet might experience near a supermassive black hole. He realized that the effect that slows time on the planet would also shift light it receives from surrounding space to higher energies.
The effect, called “blueshift,” would potentially make light reaching a planet near a black hole more dangerous. Incoming light would get amplified to much higher frequencies, including the UV range. Exposure to such high-energy radiation can damage living cells, so a planet too close to a supermassive black hole may not be hospitable to life as we know it.
“Time really affects everything around us,” says Schnittman. “Not just our perception of reality, if you will, but it actually changes the reality, changes the blueshift. It can really make everything very, very different when time is running at a different rate.” | 0.87801 | 4.104092 |
A European spacecraft that launched late last year could eventually discover 70,000 exoplanets, helping researchers better understand the number and characteristics of alien worlds throughout the galaxy, a new study reports.
The European Space Agency's star-monitoring Gaia mission, which launched in December 2013, should find about 21,000 alien planets over the course of its five-year mission and perhaps 70,000 distant worlds if it keeps operating for 10 years, the study found.
"It’s not just about the numbers. Each of these planets will be conveying some very specific details, and many will be highly interesting in their own way," lead author Michael Perryman of Princeton University said in a statement. "If you look at the planets that have been discovered until now, they occupy very specific regions of discovery space. Gaia will not only discover a whole list of planets, but in an area that has not been thoroughly explored so far." [Images: Gaia Spacecraft to Map Milky Way Galaxy]
The first alien world around a sunlike star was spotted in 1995. Since then, astronomers have found nearly 2,000 exoplanets, with more than half of the discoveries made by NASA's Kepler space telescope.
But there are many more out there, waiting to be discovered. Astronomers think that, on average, every star in the Milky Way hosts at least one planet, meaning the galaxy probably teems with more than 100 billion alien worlds.
The $1 billion Gaia mission operates from a gravitationally stable spot 930,000 miles (1.5 million kilometers) from Earth called the Earth-Sun Lagrange Point 2. The spacecraft's main goal is to catalog and closely monitor 1 billion Milky Way stars, helping researchers create a detailed 3D map that should shed light on the galaxy's structure and evolution.
But Gaia's precise tracking work should also reveal the presence of many alien planets by noting how their gravity tugs the stars slightly this way and that, researchers say.
Perryman and his colleagues wanted to get a better idea of just how many alien worlds Gaia could be expected to find. They arrived at their estimates after integrating a number of sources of information, including a comprehensive model of Milky Way star and planet positions, the latest exoplanet-distribution data (much of it from Kepler) and details of Gaia's measurement capabilities, researchers said.
"Our assessment will help prepare exoplanet researchers for what to expect from Gaia," Perryman said. "We’re going to be adding potentially 20,000 new planets in a completely new area of discovery space. It’s anyone’s guess how the field will develop as a result."
The new study has been accepted for publication in The Astrophysical Journal and is available now on the preprint site arXiv. | 0.879815 | 3.535826 |
Stretching over 300 light-years from the supernova remnant
Space news (astrophysics: supernovae; Cassiopeia A remnant) – 11,000 light-years from Earth toward the northern constellation Cassiopeia the Queen –
On the day in 1667 when a brilliant new star appeared in the sky in Cassiopeia the Queen, no written account is left to tell of the stellar event. The supernova remnant left over is called Cassiopeia A. It consists of a neutron star, with the first carbon atmosphere ever detected, and an expanding shell of material that was ejected from the star as it contracted under its own mass. The progenitor star of this supernova remnant was a supermassive star estimated to be between 15 to 20 times as massive as Sol.
The composite image of the Cassiopeia A supernova remnant seen above was made using six processed images taken over a three year period by NASA’s Spitzer Space Telescope. It shows the largest light echoes ever detected at over 300 light-years in length, which were created as light from the explosion passed through clumps of dust surrounding the supernova remnant. This light illuminated and heated surrounding dust clumps, making them briefly glow in infrared, like a series of colored lights lighting up one after the other. This resulted in an optical illusion in which the dust appears to be traveling away from the remnant at the speed of light. This apparent motion is represented in this image by different dust colors, with dust features unchanged over time appearing gray, and changes in surrounding dust over time represented by blue or orange colors.
Supernova remnant Cassiopeia A is the brightest radio emission source in the night sky above the frequency of 1 Gigahertz. It’s expanding shell of material reaches speeds above 5,000 km/s and temperatures as high as 50 million degrees Fahrenheit. First detected by Martin Ryle and Francis Graham-Smith in 1948, since this time it has become one of the most studied supernova remnants during the human journey to the beginning of space and time.
The startling false-color image above shows the many brilliant, stunning faces of the supernova remnant Cassiopeia A. Composed of images collected by three of the greatest space observatories in history, in three different wavebands of light. This view highlights the beauty hidden within one of the most violent events ever detected close by in the Milky Way.
NASA’s Spitzer Space Telescope infrared images used to create this stunning picture show warm dust in the outer shell of the supernova remnant Cassiopeia A highlighted in red. Hubble Space Telescope images added reveal delicate filaments of hot gas around 10,000 degrees Kelvin (18,000 degrees Fahrenheit) in yellow, while x-ray data collected by NASA’s Chandra X-ray Observatory is shown in green and blue. Look a little closer and deeper at the image and one sees hints of older infrared echoes from after the supernova hundreds of years ago.
Learn more about Cassiopeia A.
Take a tour of the cosmos with NASA here.
Learn more about the discoveries of the Spitzer Space Telescope.
Journey to the beginning of space and time aboard the Hubble Space Telescope.
View the cosmos in x-rays aboard NASA’s Chandra X-ray Observatory.
Learn more about supernovae here.
Learn and read about the incredible Polynesian islander navigators who used the stars, winds, current and other natural phenomena to colonize the islands of the Pacific Ocean tens of thousands of years ago. | 0.844914 | 3.830519 |
A joint European-Russian mission aiming to search for traces of life on Mars has left Earth's orbit to begin a seven-month unmanned journey to the Red Planet.
- Spacecraft detached from its Briz-M rocket booster just after 7:00am (AEDT)
- Trace Gas Orbiter will examine methane around Mars
- Lander component will spend several days measuring climatic conditions on Red Planet
The Proton rocket — carrying the Trace Gas Orbiter to examine Mars' atmosphere and a descent module that will conduct a test landing on its surface — had earlier launched from the Russian-operated Baikonur cosmodrome in the Kazakh steppe at 8:31pm (AEDT).
The spacecraft detached from its Briz-M rocket booster just after 7:00am (AEDT) before beginning its 496-million-kilometre voyage through the cosmos, the European Space Agency (ESA) said.
The ExoMars 2016 mission — a collaboration between the ESA and its Russian equivalent Roscosmos — is the first part of a two-phase exploration aiming to answer questions about the existence of life on Earth's neighbour.
The Trace Gas Orbiter (TGO) will examine methane around Mars, while a lander dubbed Schiaparelli will detach and descend to the surface of the fourth planet from the Sun.
The cost of the ExoMars mission to the European Space Agency, including the second part due in 2018, is expected to be about $1.9 billion. Russia's contribution comes on top of that.
The landing of the module on Mars is designed as a trial run ahead of the planned second stage of the mission in 2018, which will see the first European rover land on the surface to drill for signs of life.
However, problems with financing may mean it could be delayed.
TGO will be like a big nose in space: ExoMars scientist
One key goal of the TGO is to analyse methane — a gas, which on Earth is created in large part by living microbes, and traces of which were observed by previous Mars missions.
"TGO will be like a big nose in space," said Jorge Vago, ExoMars project scientist.
Methane is normally destroyed by ultraviolet radiation within a few hundred years, which implied that in Mars' case "it must still be produced today," the ESA said.
TGO will analyse Mars' methane in more detail than any previous mission in order to try to determine its likely origin.
One component of TGO, a neuron detector called FREND, can help provide improved mapping of potential water resources on Mars, amid growing evidence the planet once had as much if not more water than Earth.
A better insight into water on Mars could aid scientists' understanding of how the Earth might cope in conditions of increased drought.
Schiaparelli will spend several days measuring climatic conditions — including seasonal dust storms on the Red Planet — while serving as a test lander ahead of the rover's anticipated arrival.
The module takes its name from 19th century Italian astronomer Giovanni Schiaparelli whose discovery of "canals" on Mars caused people to believe, for a while, that there was intelligent life on our neighbouring planet.
The ExoMars spacecraft was built and designed by Franco-Italian contractor Thales Alenia Space.
Manned mission to Mars maybe in 20–30 years: Reiter
As for the next phase of ExoMars, ESA director general Jan Woerner has mooted a possible two-year delay.
"We need some more money" due to cost increases, said Ms Woerner in January:
The rover, scheduled for 2018, has been designed to drill up to two metres into the Red Planet in search of organic matter — a key indicator of life past or present.
ESA said the rover landing "remains a significant challenge" however.
Although TGO's main science mission is scheduled to last until December 2017, it has enough fuel to continue operations for years after, if all goes well.
Thomas Reiter, director of human spaceflight at ESA, said in televised remarks ahead of the launch he believed a manned mission to Mars would take place "maybe in 20 years or 30 years".
Russian-American duo Mikhail Kornienko and Scott Kelly earlier this month returned from a year-long mission at the International Space Station seen as a vital precursor to such a mission.
The ExoMars mission will complement the work of NASA's "Curiosity" rover which has spent more than three years on Mars as part of the Mars Science Laboratory (MSL) mission.
Curiosity, a car-sized mobile laboratory, aims to gather soil and rock samples on Mars and analyse them "for organic compounds and environmental conditions that could have supported life now or in the past," according to NASA.
Space has been one of the few areas of cooperation between Moscow and the West that has not been damaged by ongoing geopolitical tensions stemming from the crises in Ukraine and Syria. | 0.803281 | 3.443445 |
Taiji Programme in Space is proposed to detect GWs with frequencies covering the range of 0.1mHz to 1.0Hz with higher sensitivity around 0.01–1Hz than eLISA. The Taiji program proposes to use a triangle of three spacecrafts in orbit around the Sun. Laser beams are sent both ways between each pair of spacecrafts, and the differences in the phase changes between the transmitted and received laser beams at each spacecraft are measured. The preliminary design for the Taiji mission is based on 3-million-kilometer separations between the spacecrafts, and the expected launch date is about 2033.
The purpose of Taiji programme is to study the most challenging issues concerning massive black holes, such as how the intermediate mass seed black holes were formed in the early universe, whether dark matter could form a black hole, how seed black hole grows into a large or extremely large black holes and what is the nature of gravity.
2. Progress and Results
Taiji-01 is the first experimental satellite of Taiji Programme. It marks the first under the Phase-II of the Strategic Priority Program on Space Science (SPPSS-II) sponsored by the Chinese Academy of Sciences (CAS). As professor Yueliang Wu, director of ICTP-AP, is the chief scientist of Taiji programme, ICTP-AP is responsible for the implement, scientific research and management works.
ICTP-AP was responsible for the overall planning and coordination of the Taiji-01 project. Moreover, ICTP-AP undertook the construction and development of the scientific operation system which was one of the six systems of Taiji-01 project. Moreover, ICTP-AP joined the research of the hall-effect micro thruster system.
On August 31st, 2019, Taiji-01 launched successfully from Jiuquan Satellite Launching Center in northwestern China. By the end of 2019, the in-orbit tests were successfully completed, the functions and performance indexes of the satellite met the general requirements, and the results exceed expectations.
The in-orbit tests showed that the accuracy of displacement measurement of the laser interferometer on Taiji-01 could reach a 100-picometer order of magnitude. The accuracy of the gravitational reference sensor on the satellite reached ten billionths of the magnitude of the earth's gravitational acceleration. The thrust resolution of the micro-thruster on the satellite reached submicron-Newton scale.Taiji-01 achieved China’s highest accuracy of spatial laser interferometry; successfully conducted China’s first on-orbit drag free control technology test; firstly and internationally on-orbit verification of micro-newton level radio frequency ion propulsion technology and dual mode hall-effect micro thruster technology.
3. Taiji Consortium
In May 2017, Taiji working group initiated and founded the ‘Consortium of Gravitational Wave Detection Taiji Program in Space’ on the International Symposium on Space Gravitational Wave Detection. The consortium is an academic consortium developed by the national scientific research institutions and institutions of higher learning involved in the detection of gravitational waves，which is based on the "Taiji Programme" working group of the CAS.
As an academic consortium, it aims at leveraging the strengths of long-standing multi-disciplinary talents in and out of CAS, comprehensive platform of long accumulated high-end forward-looking technology and large scientific equipment as well as the characteristics of interdisciplinary and integration of science and education in an effort to congregate all researchers nationwide dedicated to study of theory and experiment of gravitational waves to conduct research on Space Gravitational Wave Detection.
The members of the consortium are all the scientists participating in the research of Taiji Programme, and they are the specific implementation and completion personnel of the scientific research tasks of Taiji Programme.
4. Link to Programme Site | 0.849383 | 3.114049 |
This newly released Hubble image shows Proxima Centauri, which is located just over four light-years from Earth.
Shining brightly in this Hubble image is our closest stellar neighbor: Proxima Centauri.
Proxima Centauri lies in the constellation of Centaurus (The Centaur), just over four light-years from Earth. Although it looks bright through the eye of Hubble, as you might expect from the nearest star to the Solar System, Proxima Centauri is not visible to the naked eye. Its average luminosity is very low, and it is quite small compared to other stars, at only about an eighth of the mass of the Sun.
However, on occasion, its brightness increases. Proxima is what is known as a “flare star”, meaning that convection processes within the star’s body make it prone to random and dramatic changes in brightness. The convection processes not only trigger brilliant bursts of starlight but, combined with other factors, mean that Proxima Centauri is in for a very long life. Astronomers predict that this star will remain middle-aged — or a “main sequence” star in astronomical terms — for another four trillion years, some 300 times the age of the current Universe.
These observations were taken using Hubble’s Wide Field and Planetary Camera 2 (WFPC2). Proxima Centauri is actually part of a triple star system — its two companions, Alpha Centauri A and B, lie out of frame.
Although by cosmic standards it is a close neighbor, Proxima Centauri remains a point-like object even using Hubble’s eagle-eyed vision, hinting at the vast scale of the Universe around us.
Credit: ESA/Hubble & NASA | 0.863441 | 3.784924 |
Before dawn on Tuesday, May 23, 2017, look very low in the east – very shortly before sunrise – for the extremely thin waning crescent moon and elusive planet Mercury. Will they be as close together as the 2016 photo of the moon and Mercury shown at the top of this post? No. The moon will sweep 1.6 degrees south of Mercury this month; that’s about three moon diameters. Still, if you manage to catch them, they will be beautiful in the dawn light.
If you look eastward before dawn, you’ll easily notice a bright object. That’ll be Venus, which is due to shine in our dawn sky for most of the rest of 2017. The moon has been shifting down in the east before dawn, sweeping past Venus and getting closer to Mercury, in the past few mornings:
So Mercury and the moon will be lower in the sky than Venus on the morning of May 23. Mercury is fainter than Venus, but still pretty bright for being so low in the sky, and so near the sunrise.
However, Mercury is much tougher to see from Earth’s Northern Hemisphere now than it is from Earth’s Southern Hemisphere. The farther south you are on Earth’s globe, the bigger advantage you have in seeing the moon and Mercury on May 23. That’s because these two worlds will rise earlier with respect to the sunrise, from the more southerly latitudes. Read more about the northern versus southern view of Venus and Mercury at our sky post from yesterday.
Mercury is the innermost planet in our solar system and always stays near the sun in our sky. So it shifts between the morning and evening skies; it’s been up before dawn throughout May 2017, but again the Southern Hemisphere has had the better view. Have you seen Mercury this month? If so, tell us in the comments below!
Now about that image of Mercury at the top of this post. It’s a crop from a larger photo from 2016, by astrophotographer Yuri Beletsky, who frequently shares his photos with EarthSky from the vantage point of Chile’s Atacama Desert. The entire photo is below. Isn’t it stunning?
Bottom line: The farther south you are on Earth’s globe, the better view you’ll have of the very thin waning moon and Mercury on the morning of May 23, 2017.
Deborah Byrd created the EarthSky radio series in 1991 and founded EarthSky.org in 1994. Today, she serves as Editor-in-Chief of this website. She has won a galaxy of awards from the broadcasting and science communities, including having an asteroid named 3505 Byrd in her honor. A science communicator and educator since 1976, Byrd believes in science as a force for good in the world and a vital tool for the 21st century. "Being an EarthSky editor is like hosting a big global party for cool nature-lovers," she says. | 0.865043 | 3.237827 |
Oddly shaped gaps found in Saturn's rings hint at the existence of long sought "moonlets" and support the theory that the rings are the broken remains of an icy moon shattered long ago in a violent collision, scientists say.
Scientists think a comet or asteroid collided with one of Saturn's moons about 100 million years ago. Such an impact would have created debris in a range of sizes, but until now, scientists only had evidence for chunks of rock that were miles in diameter and smaller particles that were about 65 feet (20 km) across or less. The medium-sized moonlets-so named because their size would be between that of a moon and smaller particles-predicted by theory were missing.
But in July 2004, NASA's Cassini spacecraft was hovering directly above Saturn's ring system when it detected strange gaps resembling S-shaped propellers in the planet's bright A-ring. Scientists think the gaps were formed by chunks of rock 300 feet (100 m) wide as they plowed through smaller particles in the ring.
The finding is detailed in the March 30 issue of the journal Nature.
Propellers in space
The propellers are the result of differences in the speed of material orbiting in Saturn's rings and because of the average size of the moonlets themselves, scientists think. Because the strength of gravity decreases with distance, material circling closer to a planet moves faster than material that is orbiting farther away.
As a result, small ring particles flanking the two sides of an orbiting moonlet would appear to be moving in opposite directions to a viewer standing on a moonlet. Picture three trains moving on parallel tracks but at different speeds. The train on the far left is moving fast; the middle train is moving slightly slower and the train on the far right is moving slowest of all. If an observer in the middle train were to look out her window, the train on her left would appear to be moving forward while the train on her right would look like it was trailing behind.
The moonlets in Saturn's rings are like the middle train. But because they are so large, the moonlets impede the movement of smaller ring particles to the left and right of them. This creates gaps on their left and right sides.
"Disturbances on one side [of the moonlet] get carried ahead but those on the other get carried behind," explained study leader Matthew Tiscareno from Cornell University. "That's what draws it out into the propeller shape."
The gaps taper off farther away from the moonlets as smaller ring particles gradually refill the empty space.
Scientists think that only intermediate sized rocks can create the propeller shapes. Small particles aren't massive enough to have any effect on their neighbors, while Saturnian moons like Encke and Pan-which are 4 miles (7 km) and 19 miles (30 km) wide, respectively-are so large that their gravity prevents the gaps from closing back up. Through their sheer size, the moons achieve what the moonlets can't: they harrow out rings of empty space that stretch around the entire planet.
More space propellers
The propellers were predicted from computer models but had never been observed in nature before now. They're probably found under other conditions as well, scientists think. In fact, Saturn itself might have created such gaps around the Sun as it formed in the early solar system.
According to the standard theory, planets form from swirling discs of gas, dust and debris around nascent stars. Large chunks of rock and ice in the disc collide and clump together, forming protoplanets and eventually planets.
"The planets in our solar system, the precursors anyway, probably went through this stage," said study team member Derek Richardson from the University of Maryland.
Galaxies like our own Milky Way are also swirling discs of matter that have large objects, such as stars and planets, embedded within them, so could propellers also form in galaxies?
Probably not, Richardson said.
"The analogy in a galactic disc would be a large star with lots of little stars getting strongly perturbed by it," he said. "You don't really see that kind of process operating in galaxies. Stars are far apart."
- Kinks Seen in Theft of Saturn's Ring Material
- Ring Around the Planet: Cassini's First Images of Saturn from Orbit
- ARRIVAL! Cassini Enters Orbit Around Saturn | 0.887784 | 3.891124 |
NASA’s Hubble Space Telescope captures this iridescent tapestry of star birth in a neighboring galaxy in this panoramic view of glowing gas, dark dust clouds, and young, hot stars. The star-forming region, catalogued as N11B, lies in the Large Magellanic Cloud (LMC), located only 160,000 light-years from Earth. With its high resolution, the Hubble Space Telescope is able to view details of star formation in the LMC as easily as ground-based telescopes are able to observe stellar formation within our own Milky Way galaxy. This new Hubble image zooms in on N11B, which is a small subsection within an area of star formation cataloged as N11. N11 is the second largest star-forming region in the LMC. Within the LMC, N11 is surpassed in size and activity only by the immense Tarantula nebula (also known as 30 Doradus.)
The image illustrates a perfect case of sequential star formation in a nearby galaxy where new star birth is being triggered by previous-generation massive stars. A collection of blue- and white-colored stars near the left of the image are among the most massive stars known anywhere in the universe. The region around the cluster of hot stars in the image is relatively clear of gas, because the stellar winds and radiation from the stars have pushed the gas away. When this gas collides with and compresses surrounding dense clouds, the clouds can collapse under their own gravity and start to form new stars. The cluster of new stars in N11B may have been formed this way, as it is located on the rim of the large, central interstellar bubble of the N11 complex. The stars in N11B are now beginning to clear away their natal cloud, and are carving new bubbles in turn. Yet another new generation of stars is now being born in N11B, inside the dark dust clouds in the center and right-hand side of the Hubble image. This chain of consecutive star birth episodes has been seen in more distant galaxies, but it is shown very clearly in this new Hubble image.
Farther to the right of the image, along the top edge, are several smaller dark clouds of interstellar dust with odd and intriguing shapes. They are seen silhouetted against the glowing interstellar gas. Several of these dark clouds are bright-rimmed because they are illuminated and are being evaporated by radiation from neighboring hot stars.
This image was taken with Hubble’s Wide Field Planetary Camera 2 using filters that isolate light emitted by hydrogen and oxygen gas. The science team, led by astronomers You-Hua Chu (University of Illinois) and Y?el Naz? (Universite de Li?ge, Belgium) are comparing these images of N11B, taken in 1999, with similar regions elsewhere in the LMC. This color composite image was co-produced and is being co-released by the Hubble Heritage Team (STScI) and the Hubble European Space Agency Information Center (HEIC).
Original Source: Hubble News Release | 0.892105 | 3.961094 |
Let us terraform the moon.
Mars seems to have stolen the limelight in terms of the first body to terraform (alter to make earthlike surface conditions). The moon seems not to be considered because, I am guessing, it is nearly devoid of volatiles (carbon, oxygen, nitrogen, water) and has no atmosphere at all. I think people assume that, since it is airless, it is incapable of keeping an atmosphere.
However, if the the moon had an atmosphere, it would keep it for millions of years [Calculation. 2 pages. PDF.]. That is short compared to the 4.5 billion year age of the moon, but very, very long compared to a human lifetime. Over time spans of a few millennia, there would be no perceptible change in atmospheric pressure. A lunar atmosphere would be essentially permanent.
The moon has other advantages compared to Mars. It is one light-second away, not 4 to 24 light-minutes. That’s a couple of days by rocket, as opposed to 3 to 12 months. You can have a chat by radio between earth and the moon. It gets the same amount of sunlight as earth, so terrestrial plants could easily adapt and solar power is more efficient.
This article outlines how we can terraform the moon using two basic schemes. First, atomize moon rocks to generate oxygen, and second, bring in water from the outer solar system. The small body 2060 Chiron lends itself as a good example for the latter.
The Atmosphere Furnace
The moon lacks an atmosphere. However, oxygen is very common in the lunar crust. The most common mineral is Anorthite, that is mostly CaAl2Si2O8. If one were to split that mineral one would have a metallic alloy of Ca, Al, and Si, and gaseous oxygen. The energy required to atomize Anorthite is about 4000 kilojoules per mole, which releases 4 moles, or 0.128 kg, of O2.
The mass in O2 atmosphere for a breathable lunar atmosphere is around 5 × 1017 kg [How to calculate this (PDF, 2 pages)], which implies a hefty energy expenditure of 1.5 × 1025 J of energy to get the moon to self-create an atmosphere. Now suppose we cover a 100 km by 100 km patch of the moon with solar panels. That’s 0.3% of the surface; a patch of real estate big enough to be detected by eye from earth. Assuming a conversion efficiency of 50%, we use that energy to start making air. The machines we would invent feed rock into a furnace, then separate the metals from the oxygen, letting the oxygen fly free. The power from the solar panels is 6 × 1014 watts. Power supplied at this rate creates a full atmosphere in 2.5 × 1010 seconds, or 750 years. All of this is trivially scalable. For example, if we covered the whole moon in solar panels, the job would go 300 times faster. In that case, the job would be finished in two and a half years.
We would also produce bricks of silicon, aluminum, sodium, and calcium as a byproduct. Much of this might be landfilled, so to speak, but these metals are excellent structural materials (on the moon) and could be used to build roads and buildings and other infrastructure.
I envision this as a mobile army of truck sized robots, slowly crawling artfully across the regolith, powdering rock and feeding into the furnace-separator unit. The furnace itself is a parabolic mirror that bounces sunlight to a focus point. The tractor treads and rock grinder and element separator require electricity and some photovoltaic panels, but the furnace itself is straight conversion of sunlight to heat, a nearly 100% efficient conversion.
Chiron the Water Tanker
Water is the second volatile that the moon is largely missing, except of course for small polar ice deposits discovered by the Clementine mission. Water is composed of oxygen and hydrogen, and hydrogen is the flightiest, most volatile element of all. However, in the outer solar system there is abundant water. Every small body out there is very icy, and many are more ice than rock.
I propose we bring some of that ice to us. Enter Chiron, one of countless icy remnants left over from solar system formation in the outer solar system. Chiron wobbles around between Saturn and Uranus, and shows cometary outbursts, meaning its water ices turn to steam when the sun heats it, though the sunlight is only 1% as intense as we feel here on earth. As a thought experiment, let us move Chiron to the inner solar system, then crash it on the moon. And so: water. How much water? Chiron is around 110 km in radius, so there is about 5 × 1018 kg of H2O, and a similar amount in carbon- and nitrogen-rich rocky material. Those elements are needed for fertilizer.
The technology to move moonlets is partially in hand. Ion propulsion engines, for example, are clearly the way to move small icy bodies. Their high nozzle velocities mean they don’t consume very much fuel. Their gentle thrusts are perfectly suited for patient orbit changes. The fuel they need can be mined on site. [Calculations (PDF, 2 pages)] Moving Chiron itself, these calculations show, is energetically challenging because it is such a large body. We will have to move smaller bodies, nearer bodies such at the Trojan asteroids in Jupiter’s orbit, or slice chunks off Chiron and float those home, instead, using gravitational de-assists from Jupiter and Saturn to ease the energy requirements. Or, we could pony up the energy, which seems to require a mature fusion technology for energy expenditures much larger than anything in the human experience to date.
Gentle thrusting with ion engines strapped to a moonlet would drive it at a leisurely pace toward the inner solar system. As it nears the earth-moon system, steam will erupt from all exposed surfaces, making a spectacular comet. To bring it all the way home, we will build an array of ordinary chemical rocket motors for short-lived, high-thrust burns. These will fire off for the final orbit insertions, when the moonlet moves from sun-orbit to moon-orbit. They will fire again for the final deceleration phases, to crash-land the icy body into the moon. Gentle landings are best for reasons of safety. It is probably pointless to waste too much energy on deceleration, so the moonlets will impact at speeds around 2 km/s. Impacts will make new craters and be generally messy. But the clouds of steam leftover will soon condense and precipitate. The moon will have its first rain shower.
Project Chiron is feasible with today’s technology plus a few generous oodles of engineering. Technology tests could begin soon, if we, we meaning the global community, had the collective will to try. Given sufficient interest, in 200 years, people could be frolicking in their skivvies on the shores of lunar lakes. | 0.844961 | 3.680168 |
The Dutch-Japanese made DESHIMA instrument has passed its first practical tests when measuring the distances and ages of distant galaxies. The core of the instrument is a chip the size of two euro coins that measures 49 shades of far infrared light. The developers of the spectrometer publish the results of their first measurement campaign (first light) on Monday in the journal Nature Astronomy.
Measuring distances and ages in the universe is a problem. The brightness of a star or a galaxy says little about age. Astronomers bypass this problem by measuring the doppler effect of light from galaxies. The redder the light, the higher the speed, the farther the galaxy. Unfortunately, the redshift of many galaxies in the early Universe cannot be measured with visible light, because starlight is shaded by dust clouds surrounding these galaxies. Measuring the redshift of these galaxies requires observing in far infrared.
In October 2017, Dutch and Japanese researchers, led by Akira Endo (Delft University of Technology, The Netherlands), mounted the special chip on the Japanese ASTE telescope in North Chile. The superconducting chip is developed by Delft University of Technology and SRON, Netherlands Institute for Space Research. The chip contains one antenna, 49 filters and 49 detectors. The antenna captures radiation of various wavelengths. The filters unravel the radiation in 49 tones of infrared. The 49 detectors measure the intensity of the radiation. When a detector picks up a signal, it can be seen as a peak in a graph.
The first tests with the telescope, the so-called first light, were promising. The astronomers first focused the telescope-with-chip on Mars, Saturn and a number of well-known stars and galaxies. When they saw the expected brightness without significant problems, the researchers aimed the telescope at the well-known distant galaxy VV114 and saw the predicted redshift.
The researchers are now working on a chip that can cope with 300 tones of infrared instead of the current 49. This allows them to determine the distances to galaxies that have hitherto been hidden behind dust clouds. In addition, the researchers want to link multiple chips so that they can study multiple galaxies at the same time. The development must lead to a handy-sized imaging spectrometer that is easy to use on a ground based telescope and is a must for use with space telescopes.
Help from jeweler
Incidentally, the first tests on the telescope in Chile almost failed due to material problems. There was something wrong with the cooling system of the chip. The researchers had brought spare parts for the cooling system, but they had forgotten the pins to align the parts. After searching for hours in the town of San Pedro de Atacama, the researchers came to jeweler Jose Pinto. In Pinto’s toolbox, they found a piece of copper wire with exactly the right diameter. With that they could make the forgotten pins. And so the instrument was rescued and the tests could start. | 0.88871 | 3.836447 |
Time travel has been the subject of many science-fiction books and films for the last few decades. But is it possible? Are there any time travel theories that could actually work?
Understanding Time Travel
We are all time travellers. That is to say, we all travel through time. We travel at the same time as each other; one hour per hour, and moving forward in a straight line, towards the future.
But what if we could speed up or slow down time? What if we could visit the past? Take a sneak peek into the future? What if we could really time travel? Some think the concept of time travel is promising.
Before we examine time travel theories, we should first visit Albert Einstein’s explanation of time.
Einstein, Space and Time
The majority of people view time as a constant, linear construct. One that moves forward at a regular pace. After all, we organise our lives around a 24-hour clock, a 12-month calendar, and so on.
However, Einstein showed that time can change, depending on your position in space. Space is the three dimensions we inhabit; length, width and height. We use these dimensions to pinpoint our location.
Imagine you are walking to work. The space you inhabit includes the length of the road, the width of a path and the height of buildings around you. But there is another dimension and that’s time. Time is the fourth dimension which shows our direction, which is always moving forward.
Now, Einstein’s Theory of Special Relativity proposes that time does not pass at the same rate for everyone. It varies depending on your particular position through space. For example, whether you are an observer or travelling yourself. Time can speed up or slow down depending on how fast you are moving in relation to another object.
Now we know that time does not remain the same for everyone, it is conceivable that there are plausible theories of time travel.
In fact, all astronauts are time travelling as we speak. This is because you move faster in space through time than you do on earth. Which leads us onto the first theory of time travel:
4 Time Travel Theories
Travelling at the Speed of Light
Experts have calculated the speed of light at 186,282 miles per second. This equates to 299,792 kilometres per second or an incredible 670,616,629 mph.
In theory, there is nothing that travels faster than light. But if we turn to Einstein’s special theory again, we know that time is not a single construct for everyone. Time passes at different speeds depending on the observer, their motion and the speed.
British Professor Brian Cox explains that the closer we get to the speed of light, the more time slows down. It’s all to do with how fast we go in relation to those who are standing still. Time slows down but only for the object that is moving.
“If you go fast, your clock runs slow relative to people who are still. As you approach the speed of light, your clock runs so slow you could come back 10,000 years in the future.” Prof Brian Cox
Build A Faster-Than-Light Machine
So how can we travel backwards or forwards in time? Using the ‘speed of light’ time travel theory, building a Faster-Than-Light (FTL) Machine is the way to go. It would have to be the fastest ever man-made spaceship as it would need to travel at over 670 million mph.
As a reference, the fastest NASA has ever managed to produce is the Helios 2 space probe. This blasted off in 1976 and got up to 160,000 mph when in space.
However, if we did manage to build a spacecraft capable of faster-than-light speeds, the consequences to time and our ages would be incredibly interesting. For instance, even if we didn’t manage to travel at the top speed of light, at 99%, every year spent on the FTL spacecraft would result in seven years back on earth. At 99.999%, this increases to one year on the spacecraft to 223 back on earth.
In fact, some experts believe that we could reverse time if we actually manage to travel at the speed of light. Unfortunately, Einstein states that anything with a mass cannot physically reach the speed of light, let alone pass it.
Still, if we can’t travel faster than the speed of light, are there other theories that don’t involve speed but suggest time travel is plausible?
How often have we heard Captain Kirk or Picard instructing their engineers to set engines to warp drive on Star Trek? But as so many sci-fi programmes start off, so do scientists take over.
Experts are now saying that warp drive could be possible, and it’s all to do with stretching the fabric of space-time. Imagine space is a large piece of material. On the material are the planets, stars, constellations, galaxies etc. One way to time travel would be to move space around the object travelling.
This is the Alcubierre Drive. Our spaceship pushes up the fabric of space in front of the ship. This causes the fabric to contract at the front and expand at the back. The ship rides this bubble of space-time which is constantly contracting and expanding. But it’s not violating the laws of physics as it is not travelling faster than light.
As with all of our time travel theories, there are some problems, and these are pretty big ones at that. Early estimates of the energy required to power a spaceship just 200m wide came out at billions x the mass of the observable universe. Now scientists have refined this estimate to the equivalent mass of Jupiter, but it’s still woefully unachievable.
We also don’t know how to stop the bubble once we arrive at our destination.
Speaking about the fabric of the universe, perhaps the way the universe formed can assist our quest for time travel? Astrophysicist at Princeton University J. Richard Gott certainly thinks so. In 1991, he proposed the idea of Cosmic Strings.
These strings are present throughout the universe. They resemble string-like phenomenon and are described as ‘cracks in the universe’.
Gott explains them as:
“Cosmic strings are either infinite or they’re in loops, with no ends. So they are either like spaghetti or Spaghetti Os.” J. Richard Gott
Cosmic strings are everywhere in the universe. They are similar to black holes in that they’re under tremendous pressure. This means they have a significant gravitational pull, and warp the space around them, just like black holes.
But whereas black holes crush everything they pull inside, cosmic strings could enable an object to attach onto it and fly through space at amazing speeds.
“The approach of two such strings parallel to each other, will bend space-time so vigorously and in such a particular configuration that might make time travel possible – in theory,” Gott interviewed for Live Science.
Even so, this is just one of many theories of time travel. Because as yet, no cosmic strings have ever been discovered.
All of these theories show that time travel is either outlandishly impossible, not proven or will require unheard amounts of energy. So should we still be pursuing time travel? Or, with the recent climate change problems on earth, perhaps our resources would be better spent here on this planet?
I’ll leave the last word to Joseph Agnew – an undergraduate engineer and research assistant from the University of Alabama (PRC). He’s currently working on the theory of time travel via warp drive:
“In terms of justifications for allocation of resources, it is not hard to see that the ability to explore beyond our Solar System, even beyond our Galaxy, would be an enormous leap for mankind. And the growth in technology resulting from pushing the bounds of research would certainly be beneficial.” Joseph Agnew
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Copyright © 2012-2020 Learning Mind. All rights reserved. For permission to reprint, contact us. | 0.859946 | 3.412192 |
Big asteroid population doubles in new census
(CNN) -- A new census in the solar system doubles the number of large asteroids thought to lurk between Mars and Jupiter.
Astronomers estimate that roughly 1.5 million space boulders 0.6 mile (1 km) or larger in diameter orbit in the main asteroid belt.
Rocks of such size could cause catastrophic results if they slammed into our planet, but European scientists caution that the new survey could have little bearing on risks to Earth.
The search was the first systematic one in infrared light rather than visible light. In using the European Space Agency Infrared Space Observatory, researchers looked for absorbed sunlight rather than reflected sunlight from asteroids.
Asteroids often possess dark, dusty surfaces, making them difficult to spot in visible light. But such dirty rocks soak in sun and emit infrared heat.
The infrared sampler, which ESA announced on Friday, suggests that between 1.1 million and 1.9 million large asteroids reside in the main asteroid belt, a ring of rocks orbiting the sun and thought to be the remnants of a failed planet.
"The result is about twice as high as that estimated by two other recent studies in the visible light," said Edward Tedesco of ESA.
The earlier surveys, concluded in 1998 and 2001, tallied 860,000 and 750,000 asteroids 0.6 mile (1 km) or larger in the belt.
Tedesco acknowledged that infrared and visible light surveys each have strengths and weaknesses in hunting elusive asteroids, which streak quickly across the field of vision of observatories and can vary considerably in brightness within a matter of minutes.
Taking into account the findings of the different surveys, the best population estimate would be "1.2 million asteroids larger than 1 kilometer in the main belt, give or take 500,000," Tedesco said in a statement.
Astronomers speculate that so-called Near Earth Asteroids originated in the main belt, but the gravitational pull of Jupiter disrupted their orbits eons ago and pushed them closer to our planetary neighborhood.
About 500 NEAs have been identified so far. None pose much of a risk to our planet for a century or more, but astronomers suspect that hundreds more remain undiscovered.
The new infrared survey did not include NEAs and preliminary calculations suggest that the survey will not affect the NEA risk assessment, ESA scientists said.
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Apr 17, 2013
Dione exhibits some unusual features that may indicate electrical forces at work.
Recently, the Cassini-Solstice spacecraft made a close flyby of the moon Enceladus. As the Picture of the Day from May 3, 2012 discussed, the bright plumes emanating from the 500 kilometer moon are most likely the result of an electrical connection between it and the gas giant planet Saturn. On the same day, Cassini also flew fairly close to Dione, another of Saturn’s enigmatic moons.
The formerly named Cassini-Huygens mission was launched from Cape Canaveral on October 15, 1997. Few now remember the public outcry against the mission. There were several attempts by citizens groups to stop the launch because of the 33 kilograms of plutonium-238 that provides electrical power to the orbiter. Since there had been failures of other launch vehicles, the concern was that an explosion of the Titan IV-B rocket would scatter radiation over many hundreds of square kilometers in southern Florida.
However, the launch was uneventful, and after several years flight time Cassini entered orbit around Saturn on July 1, 2004. A few months later, Cassini deployed the Huygens lander, which descended by parachute to the surface of the Solar System’s largest moon, Titan.
In the last eight years, Cassini has made close approaches to a number of Saturn’s moons, Dione among them. This time, the spacecraft looked at Dione from a distance of about 8000 kilometers, but it has come as close as 67 kilometers on previous passes.
Dione’s mean diameter is 1123 kilometers. In comparison, the diameter of Earth’s Moon is 3475 kilometers, so Dione is among the medium-large moons in the Solar System. Iapetus, Rhea, and Tethys are similar in size, as are Uranus’ moons Ariel, Titania, and Oberon.
The first images of Dione revealed a moon whose surface appeared to be dominated by bright “wisps” that wound around its face. Later, when higher resolution pictures were decoded, the wisps were discovered to be deep chasms and trenches that split large craters, running for hundreds of kilometers. Mission specialists remain baffled by the extent to which the moon has been “fractured”, although some form of faulting due to tectonic activity continues as their best guess.
According to a March 2, 2012 press release, ionized oxygen molecules have been detected on Dione. This means that Dione joins Saturn’s moon Rhea in possessing a highly rarified atmosphere. Planetary scientists speculate that the oxygen comes from solar wind ions impacting the water ice on both moons, causing it to crack into hydrogen and ionized oxygen.
Dione also joins its sisters Tethys and Enceladus in spewing charged particles into the ring structure around Saturn. Like Enceladus, the “plumes” are ejected from numerous hot spots. Evidence exists that Dione also contributes to the plasma trapped within Saturn’s magnetosphere. Jim Burch of the Southwest Research Institute used data from Cassini’s Plasma Spectrometer (CAPS) to determine that the plasma electrons were emitted from Tethys and Dione.
In the Electric Universe hypothesis, the charged particles from Dione (and Tethys) are due to plasma discharges that are ejecting material into space, in the same way that Jupiter’s moon Io contributes sulfur plasma to the magnetospheric torus around Jupiter. It seems likely that conditions in the past were far more energetic, forming Dione’s present day etched terrain.
The grooves and canyons run parallel to each other. They have sharp rims and begin abruptly with no gradually eroded look to them. They have side canyons running off at ninety-degree angles and craters along their length, often in chains. The craters are shallow with no debris around them and have central peaks.
The moons of Saturn orbit within its plasmasphere and exchange electrical energy with one another, so electricity must be considered whenever we observe unusual morphology. Projecting earthly geologic forces and the slow progress of erosion onto other planets and moons misses the point. Wind and rain erode our planet and presumably create canyons and valleys. When no wind or rain exists, such as on Dione, how does the fresh looking and unique topography occur? Should we then question whether wind and rain alone have sculpted the Earth? | 0.858318 | 3.603143 |
The dwarf planet has a paucity of big pockmarks because it has somehow erased them.
Ceres is the largest body in the asteroid belt. It spans about 940 km (580 miles), more than half again as big as one of the next largest asteroids, Vesta (525 km/326 mi). Over the course of the solar system’s 4½ billion years, these bodies have received an almighty pummeling from rocks and comets, leaving their surfaces battle-scarred.
But, as Simone Marchi (Southwest Research Institute) and others report July 26th in Nature Communications, when it comes to big craters Ceres is strangely smooth.
Vesta, which NASA’s Dawn spacecraft visited before it arrived at Ceres in 2015, has a devastated-looking surface. Its largest crater (Rheasilvia) is nearly as wide as the asteroid itself. Planetary scientists estimated that Ceres would also look ragged, with roughly a dozen craters bigger than 400 km. Yet its largest crater, Kerwan, spans only 280 km. And of the 40-plus pockmarks the dwarf planet “should” have that are larger than 100 kilometers, it has only 16.
Ceres does, however, have a bunch of smaller craters — so many that in some areas the surface is saturated with them, meaning that for every new crater created, another one is erased. These could hide older, larger structures.
And in fact the team has now found the echo of an 800-km-wide crater: the low-lying Vendimia Planitia, hidden to the eye but apparent (barely) in a topographic map. Kerwan lies within its southern edge. The putative basin also looks distinctly different in terms of chemical makeup than the rest of Ceres, suggesting the impact might have excavated stuff with a different composition or triggered its creation when the body hit.
Even with that finding, though, there still aren’t enough large craters to satisfy scientists — it’s very difficult to explain why there are so few in the 100- to 400-km range.
The solution is that Ceres has likely erased its scars with time. This process could have happened a couple of ways. Recent analysis by the Dawn team suggests the dwarf planet’s subsurface is 30% to 40% ice by volume. Without a rigid rock makeup, Ceres’s surface would relax over time, like skin does after you press it hard with your fingertip. This relaxation would slowly obliterate craters. And since big craters happened more often in the solar system’s early history — when more big hunks of rock were flying around — those would be more faded relative to smaller ones.
Another possibility is that ice volcanism resurfaced Ceres. The infamous bright spots in the crater Occator and elsewhere are salt deposits, and they may have been left there by water rising from below and then evaporating away. If so, then this world was geologically active (maybe it still is?) and could have remade its façade.
Reference: S. Marchi et al. “The missing large impact craters on Ceres.” Nature Communications. July 26, 2016.
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This is a further update about the G2 cloud which is observed to be on a high-speed trajectory toward the Galactic core; see Figure 1. For the last postings on this click here or here. The evidence now looks almost certain that the G2 cloud contains an embedded star (or stars). Eckart, et al., 2013 have detected a K band infrared image of the cloud and have concluded that their results indicate that the cloud contains a star having a mass somewhere between one solar mass and 30 solar masses (Eckart, 2013a; Eckart, 2013b). They refer to the G2 cloud as a DSO, or “Dusty S-cluster Object.”
About 45% of all one solar mass stars are observed to have a binary companion star, about 60% of all 10 solar mass stars are seen to have stellar companions, and about 75% of all 30 solar mass stars have companion stars. So for the stated mass range for the G2 cloud star, there is about a 50:50 chance that it will have a stellar companion, and if it doesn’t have a stellar companion, there still remains about a 100% chance that it will have a giant planet or brown dwarf companion. So the situation is beginning to look pretty serious.
Papers published so far on the G2 cloud have failed to discuss the possibility that an embedded star might carry with it a companion. And yet this is the most important aspect to consider in this upcoming cloud-core encounter, because tidal stripping of a companion star and entrainment into the Galactic core would almost certainly trigger a core explosion with consequent prompt superwave impact on our solar system.
Whether or not the companion star is stripped away will depend on whether it orbits outside or inside the primary star’s L1 Lagrange point, the point of no return beyond which orbiting dust, planets, or companion stars come under the influence of the Galactic core’s dominant gravitational pull. The L1 point is located close to the star on the side facing the Galactic core; see Figure 2. If a companion star orbits its primary star at a distance closer than this L1 point distance, it will remain under the influence of the primary’s gravitational pull and remain bound in a binary orbit. If not, it will enter the core’s Roche lobe and get sucked in.
The statistics do not look to favor the companion’s survival. Binary stars are separated from one another on average by about 8 astronomical units (AU), although they can be located as close as 0.1 AU in very close binaries. By comparison, Eckart, et al. note that when the G2 cloud is at periastron distance, and if its embedded primary star has a mass of one solar mass, its L1 Lagrange point will be positioned about 0.1 AU away; if the embedded star is an 8 solar mass star, its L1 point will lie further out, about 0.5 AU away; and if the cloud contains a 30 solar mass star, its Lagrange point will lie still further out, about 1 AU away. So with the Lagrange point being so close to the primary star (0.1 to 1 AU), the chances are that when the G2 cloud makes its closest approach to Sgr A*, the companion star will be orbitting outside the L1 Lagrange point and within the Galactic core’s Roche Lobe. This means that it will almost certainly be stripped off and end up getting pulled into the core. If the tidally stripped body is of lower mass, such as an Earth sized planet or jovian planet instead of a star, then it is likely that the triggered core outburst will be much smaller. How large or small cannot be said. There is no way to predict.
At periastron, its closest approach to the Galactic core, the G2 cloud will be somewhere between 125 and 200 AU from the core following the highly eccentric orbit shown in Figure 1. At its closest approach, it will come about as close to the core as the S2 star, when that star is at periastron. Since S2 makes has an orbital period of a bit over 15 years, it has made many close approaches to the core in the past centuries with no serious consequences. Since no outburst activity was observed when the S2 star passed close to the core in 2002, one might ask whether we have anything to worry about from the G2 cloud. For the S2 star to make repeated passages of the Galactic core with no noticeable consequences, we may conclude that it is a single star and that any companion objects such as stars or planets were long ago stripped away by the core’s gravitational field. In fact, it is possible that S0 is the remnant of an inbound star system which had its companion mass stripped off some time in the past and resulting a core explosion. For example, it may have triggered one of the 13 minor core outbursts that took place in the past 5300 years. The G2 cloud, however, is making its first pass of the core, and the statistics are stacked in favor of it having a companion.
Tidal stripping will be most likely begin to occur when the G2 cloud has reached its periastron, point of closest approach to the Galactic core. Based on predictions of various authors, this is most likely to occur sometime between March and May of 2014; see Table 1 Once we see the G2 cloud divide and a mass split off, we will only have two to three weeks before the mass reaches the core surface and triggers an explosion. So we should keep close watch should something be about to happen.
The research that went into the preparation of this posting was financed by the Starburst Foundation. Those who feel that these G2 Cloud postings are of interest and of general importance please visit the Starburst Foundation website and make a donation. | 0.875718 | 3.872067 |
Shocked crystals give better Mars dating
Martian timeline Debate over the true age of Martian meteorites could be over thanks to a new dating technique, which suggests the red planet was forming rocks billons of years longer than previously thought.
The study, reported in the journal Nature, has determined the age a rare volcanic meteorite, known as a shergottite, to be no more than 200 million years old -- not four billion as previously thought.
Researchers made the discovery by combining secondary ion mass spectroscopy and electron backscatter diffraction to date tiny mineral grains in a meteorite called NWA 5298, found in Morocco in 2008.
"These two techniques, which are both relatively new, have never been combined ... to study a Martian meteorite," says study co-author Professor Kevin Chamberlain of the University of Wyoming.
Martian meteors are pieces of rock blasted from the planet's crust into space as the result of an impact by an asteroid or comet.
Shergottites have a composition similar to volcanic basalts found on Earth, indicating they originated from regions such as the Tharsis bulge, an ancient volcanic hotspot that includes the solar system's tallest volcano, Olympus Mons.
The researchers used the new technique to accurately date the nanometre-sized grains called baddeleyite crystals, embedded throughout the meteorite. These crystals formed from magma that had solidified on the Martian surface.
Shock damaged crystals
Many showed signs of 'shock damage' as a result of the impact that launched the meteor into space.
"We measured multiple baddeleyite crystals, which all recorded differing degrees of shock," says Chamberlain.
By comparing the ratio of uranium to lead isotopes in the crystals, the researchers found a clear correlation between the age of the crystal and how much shock it had experienced. Those closer to the surface of the meteorite displayed the most shock.
"The ages of those crystals ranged from 187 million down to 22 million years," says Chamberlain.
This implies that the meteorite probably formed 187 million years ago and was blasted into space about 165 million years later.
The team also found the impactor hit with enough force to melt minerals within the shergottites, forming microscopic zircon crystals.
"Those crystals were completely unshocked, they were pristine, meaning they formed after the impact."
The new technique also allowed the authors to identify an underlying signature that had confused researchers trying to determine the age of shergottites.
Previous estimations of the meteors suggested they may have formed four billion years ago. Chamberlain says this measure is more likely the result of an upper mantle melting event that first formed the magma in the planet's history, which may still sit under the crust today. | 0.895664 | 3.810376 |
Speeding through the atmosphere high above Jupiter’s equator is an east–west jet stream that reverses course on a schedule almost as predictable as a Tokyo train’s.
Now, a NASA-led team has identified which type of wave forces this jet to change direction.
Similar equatorial jet streams have been identified on Saturn and on Earth, where a rare disruption of the usual wind pattern complicated weather forecasts in early 2016. The new study combines modeling of Jupiter’s atmosphere with detailed observations made over the course of five years from NASA’s Infrared Telescope Facility, or IRTF, in Hawai’i. The findings could help scientists better understand the dynamic atmosphere of Jupiter and other planets, including those beyond our solar system.
“Jupiter is much bigger than Earth, much farther from the Sun, rotates much faster, and has a very different composition, but it turns out to be an excellent laboratory for understanding this equatorial phenomenon,” said Rick Cosentino, a postdoctoral fellow at NASA’s Goddard Space Flight Center in Greenbelt, Maryland, and lead author of the paper published in the Journal of Geophysical Research-Planets.
Earth’s equatorial jet stream was discovered after observers saw debris from the 1883 eruption of the Krakatoa volcano being carried by a westward wind in the stratosphere, the region of the atmosphere where modern airplanes achieve cruising altitude. Later, weather balloons documented an eastward wind in the stratosphere. Scientists eventually determined that these winds reversed course regularly and that both cases were part of the same phenomenon.
The alternating pattern starts in the lower stratosphere and propagates down to the boundary with the troposphere, or lowest layer of the atmosphere. In its eastward phase, it’s associated with warmer temperatures. The westward phase is associated with cooler temperatures. The pattern is called Earth’s quasi-biennial oscillation, or QBO, and one cycle lasts about 28 months. The phase of the QBO seems to influence the transport of ozone, water vapor and pollution in the upper atmosphere as well as the production of hurricanes.
Jupiter’s cycle is called the quasi-quadrennial oscillation, or QQO, and it lasts about four Earth years. Saturn has its own version of the phenomenon, the quasi-periodic oscillation, with a duration of about 15 Earth years. Researchers have a general understanding of these patterns but are still working out how much various types of atmospheric waves contribute to driving the oscillations and how similar the phenomena are to each other.
Previous studies of Jupiter had identified the QQO by measuring temperatures in the stratosphere to infer wind speed and direction. The new set of measurements is the first to span one full cycle of the QQO and covers a much larger area of Jupiter. Observations extended over a large vertical range and spanned latitudes from about 40 degrees north to about 40 degrees south. The team achieved this by mounting a high-resolution instrument called TEXES, short for Texas Echelon Cross Echelle Spectrograph, on the IRTF.
“These measurements were able to probe thin vertical slices of Jupiter’s atmosphere,” said co-author Amy Simon, a Goddard scientist who specializes in planetary atmospheres. “Previous data sets had lower resolution, so the signals were essentially smeared out over a large section of the atmosphere.”
The team found that the equatorial jet extends quite high into Jupiter’s stratosphere. Because the measurements covered such a large region, the researchers could eliminate several kinds of atmospheric waves from being major contributors to the QQO, leaving gravity waves as the primary driver. Their model assumes gravity waves are produced by convection in the lower atmosphere and travel up into the stratosphere, where they force the QQO to change direction.
The results of simulations were an excellent match to the new set of observations, indicating that they correctly identified the mechanism. On Earth, gravity waves are considered most likely to be responsible for forcing the QBO to change direction, though they don’t appear to be strong enough to do the job alone.
“Through this study we gained a better understanding of the physical mechanisms coupling the lower and upper atmosphere in Jupiter, and thus a better understanding of the atmosphere as a whole,” said Raúl Morales-Juberías, the second author on the paper and an associate professor at the New Mexico Institute of Mining and Technology in Socorro. “Despite the many differences between Earth and Jupiter, the coupling mechanisms between the lower and upper atmospheres in both planets are similar and have similar effects. Our model could be applied to study the effects of these mechanisms in other planets of the solar system and in exoplanets.”
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It has long been known ‘possibly since the time of the Babylonians’ that the relation of the movements of the planets Venus and Earth is geometrically structured according to the number five. When we continually plot the movement of Venus from a geocentric view we obtain a fivefold loop figure. If we connect the subsequent positions of conjunction of both the planets by lines this leads to a nearly exact pentagram. As shown in Fig. 2.1, one pentagram which forms in an 8-year period is turned only by 2.4 degrees compared to the preceding one.
Figure 2.1 Venus/Earth-loops as seen from Venus over a period of 15.987 years (including 10 conjunctions). The pentagrams show the positions of the conjunctions and oppositions (on the outside). A view from Earth yields the same figure, only turned by 180 degrees.
In the representation of the linklines or ‘Raumgeraden’, (i.e. the imaginary connecting lines between two planets within a fixed period), a concept developed by the author, it can be seen that the geometrical formative principle repeats itself in the heliocentric view. After about eight years we witness the full blossom of a fivefold starflower shown in Figure 2.2
Figure 2.2 Linklines between Venus and Earth, continually plotted, stepping interval 3 days (1000 times). Scale in millions of km. Sun in the centre of the co-ordinate plane. © Keplerstern Verlag
The evenness of these figures results from the very exact 13/8 proportion of the periods of revolution of both planets (and is independent of the chosen 3-day interval). Ratios of small integers of this type are called resonances in celestial mechanics. In the long term they can influence the stability of the orbits of planets or asteroids. This influence can have a reinforcing but also a destabilising effect, depending on the gravitational interaction between the celestial bodies, caused by the build-up of resonance. The graphics of movements shown here, give an overall impression of these influences. Up to the number 12 there is only one more geometrically distinct resonance among the relations of any two planets within our solar system, as shown in Fig. 2.3. (Why the number 12 serves as the upper limit the planets will explain “for themselves” shortly).
Figure 2.3 Linklines between Jupiter and Uranus, continually plotted, stepping interval 60.78 days (1000 times), total space of time 166.4 years. © Keplerstern Verlag
Strangely enough the pentagram, which has been associated with the human being since ancient times, manifests itself in the inner solar system, in the relation of Earth and Venus, the goddess of love. In outer regions, on the other hand, we see the hexagram, a symbol for the permeation of two polar principles, which constitute the order of the material world. To delve more deeply into the symbolic language, which seems to be incorporated in our cosmic home, we now have to consider other planets, i.e. the constellations of three of them at a time. As already mentioned the Venus/Earth pentagram forms, when we plot the positions of their conjunctions continually and draw lines between them (in geocentric as well as in heliocentric view).
If we plot the position of Mars after each complete formation of a pentagram and connect the various points, we obtain an almost fully resonant square. It is just slightly distorted, due to the relatively high eccentricity of the Mars revolution (compare Figure 2.4).
Figure 2.4 Mars in relation to Venus/Earth-pentagrams (150 times); from inside to outside: orbits of Venus, Earth and Mars over a total period of approx. 1195 years. The Venus/Earth pentagram is noted only once in each orbit. © Keplerstern Verlag.
The symbol of the human being is thus placed into a quadrangle; one could also say, man is nailed to the cross of the world or of the god of war. A cross arises if one connects the opposite corners of the square, but it materialises also in other diagrams, or patterns, of planetary movement, but this goes beyond the scope of this summary. Even without this interpretation the geometrical constellation between our home planet and its two cosmic neighbours is so remarkable, that you have to wonder, why it has never been mentioned in any relevant literature on the planetary system. … …
The geometrical relationship of any three planets can also be represented in two other types of graphic, the geocentric (or, more generally speaking, planetocentric) loop diagram on the one hand, and the heliocentric linklines diagram on the other. We obtain these diagrams by continually plotting the position of one planet as seen from a second one, when the first (or the second) is in conjunction with a third. In addition we plot the link lines at the given points in time. The result are general graphical representations of the gravitational interaction between any three planets. Among the great number of all possible constellations involving the nine planets of our solar system all numbers up to twelve emerge exactly once! Furthermore the different figures stand in an internal numerical order, i.e. in a network of relations organized by small integers, with a mysterious overall architecture, which can only be briefly mentioned here. For example, the hexagram of Jupiter and Uranus combined with Mars or Earth or Venus transforms into geometrical forms, that are governed by the number 5 (Mars) and its multiples 10 (Earth) or 20 (Venus).
The observed doubling of numbers – which obviously determines the formation of the figures between the planets involved and which corresponds musically to the octave and double octave – seems somewhat mystical; at least there are no mathematical reasons known to the author. Moreover, in the opposite direction, a sixfold blossom springs from the Venus/Earth pentagram (the starflower), when Pluto is included as the third planet. The most impressive figure, however, emerges in a similar manner from the relation of the three most massive planets Jupiter, Saturn and Neptune. As we have seen, Jupiter, which is by far the biggest planet, had its share in the formation of the hexagram. Now, in co-operation with the two other mentioned members of the outer region, the symbol of polarity reaches perfection, raised, so to speak, into its higher octave.
In the outer planetary system, which is the space that borders on the stars with their zodiac, the ancient symbolic number that was associated with the sky and heaven in different cultures appears before our eyes and our mind. In heliocentric view this would also result in a star shape, if less expressive, organized by the number twelve. In the planetocentric graph shown the connecting lines of the constellations produce two hexagons, while the succession of positions arrange themselves ‘as though guided by an invisible hand’ in three quadrangular, star-shaped forms. These figures individually are called astroids. Three astroids are woven into a twelve-pointed star and together with the web formed by the connecting lines a degree of geometrical perfection is achieved, which may touch the human heart almost like music.
Pythagoras never said, argued the German philosopher Friedrich W.J. Schelling, that these movements (of the planets) cause the music, but that they themselves are the music. This indwelling movement needed no external medium through which it might become music, for it was of itself music. | 0.912968 | 3.844282 |
We’re all gonna die! A rogue cloud galaxy is coming and it’s going to smash into the Milky Way, make its black hole bigger and knock our planet out of the galaxy like a bocce ball!
Well, yes, yes, yes and possibly … although the people riding Earth as it hurdles through space will not be us. While astronomers have always known that galaxies can and do collide and the Milky Way is on a slow crash course towards Andromeda, new models have found a more immediate danger from something called the Large Magellanic Cloud which is headed our way much sooner than expected. How soon? Is it OK to spend the money you were planning to pass down to your grandkids?
“Ultimately, there is no escape.”
That would be a great opening line for “The Day Milky Way Met the Large Magellanic Cloud” but it’s actually the scary warning from Marius Cautun, an astrophysicist at Durham University’s Institute for Computational Cosmology and lead researcher on “The aftermath of the Great Collision between our Galaxy and the Large Magellanic Cloud,” a study published in the latest edition of the Monthly Notices of the Royal Astronomical Society. The Large Magellanic Cloud is a so-called ‘satellite’ galaxy, the second- or third-closest galaxy to the Milky Way and the fourth-largest galaxy in the Local Group – the group of 54 galaxies that includes the larger Andromeda, Milky Way and Triangulum galaxies. It’s visible as a faint cloud from the southern hemisphere between the constellations of Dorado and Mensa.
And it’s headed our way.
“The collision between our galaxy and the [Large Magellanic Cloud] takes place in the majority of cases—over 93 percent.”
Cautun led a team ran eight new supercomputer simulations using data from new observations that the Large Magellanic Cloud is much bigger than previously thought. While it’s currently headed away from the Milky Way, it is expected to turn around and head towards the black hole in its center and wreak havoc the likes of which the galaxy has not seen since the last collision, whenever that was. While that sounds pretty bad – it will cause the black hole to expand to five times its current size, spew jets of radiation, move stars around, knock planets out of orbit and possibly send solar systems out of the galaxy – Cantus, like a true astronomer with a rose-colored telescope, sees some good in the collision.
“This catastrophic and long-overdue event will restore the MW to normality.”
The “MW” (Milky Way) apparently has a small central black hole in comparison to other galaxies and this will give it a normal one. And how long will it be before MW can stop getting counseling to deal with its small black hole?
“Even though the LMC is currently heading away from the MW, dynamical friction acting on such a heavy galaxy will cause its orbit rapidly to lose energy and, approximately a billion years from now, to turn around and head towards the centre where it is destined to merge in another 1.5 billion years or so.”
That’s 2.5 billion years from now. If humans are still around, Cautun says the possibility that they will be knocked out of the galaxy is there but remote. More likely, they will witness a light show in the sky that will change the constellations considerably and get them ready for the bigger collision 2.5 billion years after that when Andromeda and the Milky Way begin to smash together with such force that only one will survive. If there are still bookies around, humans should put their money (or whatever they bet with in the year 5,000,000,002,019) on Andromeda.
If you’re smart, you’ll hide that last part from your grandkids as you spend their inheritance. | 0.811065 | 3.641528 |
Scientists have found evidence for a large number of double supermassive black holes, likely precursors of gigantic black hole merging events.
Scientists have found evidence for a large number of double supermassive black holes, likely precursors of gigantic black hole merging events. The research, published in the journal Monthly Notices of the Royal Astronomical Society, confirms the current understanding of cosmological evolution — that galaxies and their associated black holes merge over time, forming bigger and bigger galaxies and black holes.
Astronomers from the University of Hertfordshire in the UK and colleagues looked at radio maps of powerful jet sources and found signs that would usually be present when looking at black holes that are closely orbiting each other. Before black holes merge they form a binary black hole, where the two black holes orbit around each other.
Gravitational wave telescopes have been able to find evidence of the merging of smaller black holes since 2015, by measuring the strong bursts of gravitational waves that are emitted when binary black holes merge. However, current technology cannot be used to demonstrate the presence of supermassive binary black holes.
Supermassive black holes emit powerful jets. When supermassive binary black holes orbit, it causes the jet emanating from the nucleus of a galaxy to periodically change its direction. Astronomers studied the direction that these jets are emitted in, and variances in these directions. They compared the direction of the jets with the one of the radio lobes (that store all the particles that ever went through the jet channels) to demonstrate that this method can be used to indicate the presence of supermassive binary black holes.
“We have studied the jets in different conditions for a long time with computer simulations,” said Martin Krause from the University of Hertfordshire. “In this first systematic comparison to high-resolution radio maps of the most powerful radio sources, we were astonished to find signatures that were compatible with jet precession in three quarters of the sources,” Krause said.
The fact that the most powerful jets are associated with binary black holes could have important consequences for the formation of stars in galaxies; stars form from cold gas, jets heat this gas and thus suppress the formation of stars. A jet that always heads in the same direction only heats a limited amount of gas in its vicinity, researchers said.
However, jets from binary black holes change direction continuously. they said. They can heat much more gas, suppressing the formation of stars much more efficiently, and thus contributing towards keeping the number of stars in galaxies within the observed limits. PTI SAR SAR 10261512 | 0.867311 | 4.132892 |
New data from NASA’s Swift spacecraft have led to the discovery of a rare subclass of neutron star and will help astronomers decipher the physical nature of X-ray flares.
Recent observations by NASA’s Swift spacecraft have provided scientists a unique glimpse into the activity at the center of our galaxy and led to the discovery of a rare celestial entity that may help them test predictions of Albert Einstein’s theory of general relativity.
This week, at the annual meeting of the American Astronomical Society in National Harbor, Maryland, scientists presented their research into images captured by Swift, explaining how these images will help decipher the physical nature of X-ray flares and enabled their discovery of a rare subclass of neutron star.
This sequence from the X-ray Telescope aboard NASA’s Swift shows changes in the central region of the Milky Way galaxy from 2006 through 2013. Watch for flares from binary systems containing a neutron star or black hole and the changing brightness of Sgr A* (center), the galaxy’s monster black hole. Image Credit: NASA/Swift/N. Degenaar (Univ. of Michigan)
Swift’s seven-year campaign to monitor the center of the Milky Way has doubled the number of images available to scientists of bright X-ray flares occurring at the galaxy’s central black hole, dubbed Sagittarius A* (Sgr A*).
Sgr A* sits in the center of the Milky Way’s innermost region, 26,000 light-years away in the direction of the constellation Sagittarius. Its mass is at least 4 million times that of the sun. Despite its considerable size, it is not nearly as bright as it could be if it was more active, according to one expert.
“Given its size, this supermassive black hole is about a billion times fainter than it could be,” said Nathalie Degenaar, principal investigator on the Swift galactic center campaign and an astronomer at the University of Michigan in Ann Arbor. “Though it’s sedate now, it was quite active in the past and still regularly produces brief X-ray flares today.”
To better understand the black hole’s behavior over time, the Swift team began making regular observations of the Milky Way’s center in February 2006. Every few days, the Swift spacecraft turns toward the innermost region of the galaxy and takes a 17-minute-long snapshot with its X-ray Telescope (XRT).
This simulation shows the future behavior of the G2 gas cloud now approaching Sgr A*, the supermassive black hole at the center of the Milky Way. X-ray emission from the cloud’s tidal interaction with the black hole is expected sometime this spring. Image Credit: ESO/MPE/M.Schartmann
To date, Swift’s XRT has detected six bright flares during which the black hole’s X-ray emission was as much as 150 times brighter for a couple of hours. These new detections enabled the team to estimate that similar flares occur every five to 10 days. Scientists will look at differences between the outbursts to decipher their physical nature.
The Swift XRT team expects 2014 to be a banner year for the campaign. A cold gas cloud named G2, about three times the mass of Earth, will pass near Sgr A* and already is being affected by tides from the black hole’s powerful gravitational field. Astronomers expect G2 will swing so close to the black hole during the second quarter of the year that it will heat up to the point where it produces X-rays.
If some of the cloud’s gas actually reaches Sgr A*, astronomers may witness a significant increase in activity from the black hole. The event will unfold over the next few years, giving scientists a front-row seat to study the phenomena.
“Astronomers around the world are eagerly awaiting the first sign that this interaction has begun,” said Jamie Kennea, a team member at Pennsylvania State University in University Park, Pennsylvania. “With the invaluable help of Swift, our monitoring program may well provide that indicator.”
Scientists saw what they thought was a sign in April, when Swift detected a powerful high-energy burst and a dramatic rise in the X-ray brightness of the Sgr A* region. They were excited to discover the activity came from separate source very near the black hole: a rare subclass of neutron star.
A neutron star is the crushed core of a star destroyed by a supernova explosion, packing the equivalent mass of a half-million Earths into a sphere no wider than Washington. The neutron star, named SGR J1745-29, is a magnetar, meaning its magnetic field is thousands of times stronger than an average neutron star. Only 26 magnetars have been identified to date.
The discovery of SGR J1745-29 may aid scientists in their exploration of important properties of the Sgr A* black hole. As it spins, the magnetar emits regular X-ray and radio pulses. As it orbits Sgr A*, astronomers could detect subtle changes in the pulse timing because of the black hole’s gravitational field, a prediction of Einstein’s theory of general relativity.
“This long-term program has reaped many scientific rewards, and due to a combination of the spacecraft’s flexibility and the sensitivity of its XRT, Swift is the only satellite that can carry out such a campaign,” said Neil Gehrels, the mission’s principal investigator at NASA’s Goddard Space Flight Center in Greenbelt, Maryland.
Goddard manages Swift, which was launched in November 2004. Goddard operates the spacecraft in collaboration with Pennsylvania State University, the Los Alamos National Laboratory in New Mexico and Orbital Sciences Corp. in Dulles, Virginia. International collaborators are located in the United Kingdom and Italy. The mission includes contributions from Germany and Japan.
- N. Degenaar, et al., “The X-ray flaring properties of Sgr A* during six years of monitoring with Swift,” 2013, ApJ, 769, 155; doi:10.1088/0004-637X/769/2/155
- J. A. Kennea, et al., “Swift Discovery of a New Soft Gamma Repeater, SGR J1745–29, near Sagittarius A*,” 2013, ApJ, 770, L24; doi:10.1088/2041-8205/770/2/L24
PDF Copies of the Studies:
- The X-ray flaring properties of Sgr A* during six years of monitoring with Swift
- Swift Discovery of a New Soft Gamma Repeater, SGR J1745-29, near Sagittarius A*
Image: NASA/Swift/N. Degenaar (Univ. of Michigan) | 0.912461 | 3.939961 |
The biggest volcano on the Jupiter moon Io should erupt any day now, a new study suggests.
Loki Patera, a 125-mile-wide (200 kilometers) lava lake on the most volcanically active body in the solar system, has had fairly regular activity over the past few decades. And it's due for an outburst very soon.
"If this behavior remains the same, Loki should erupt in September 2019, around the same time as the EPSC-DPS meeting in Geneva," Julie Rathbun, a senior scientist at the Planetary Science Institute in Tucson, Arizona, said in a statement yesterday (Sept. 17). "We correctly predicted that the last eruption would occur in May of 2018."
EPSC-DPS is a joint conference held by the European Planetary Science Congress and the American Astronomical Society's Division for Planetary Sciences, and it's going on now. Rathbun presented the new results at the meeting yesterday.
Scientists aren't sure what drives Loki Patera's outbursts, but the leading explanation posits a process very different than what's behind typical volcanic eruptions here on Earth: The top layer of Loki Patera solidifies, then falls into the still-liquid portion below.
And the intrigue surrounding Loki Patera doesn't stop there; the periodicity of the lake's eruptions has changed over the decades as well. The outbursts occurred every 540 Earth days or so in the 1990s. The periodic behavior seemed to stop in the early 2000s but reappeared around 2013, with eruptions now happening roughly every 475 days.
Given all these shifts and uncertainties, Rathbun isn't exactly betting the farm on a Loki Patera flare-up in the next few days.
"Volcanoes are so difficult to predict because they are so complicated. Many things influence volcanic eruptions, including the rate of magma supply, the composition of the magma — particularly the presence of bubbles in the magma, the type of rock the volcano sits in, the fracture state of the rock and many other issues," Rathbun said in the same statement.
"We think that Loki could be predictable because it is so large," she added. "Because of its size, basic physics are likely to dominate when it erupts, so the small complications that affect smaller volcanoes are likely to not affect Loki as much. However, you have to be careful because Loki is named after a trickster god [in Norse mythology], and the volcano has not been known to behave itself."
Loki Patera's activity cycle is far too lengthy to be tied to Io's orbit around Jupiter, which is supertight; the moon completes one lap every 1.77 Earth days. So, researchers think that gravitational interactions among Io and some of its fellow moons may be responsible for the (semi) regularity.
Jupiter's powerful gravity is the root cause of Io's volcanism overall, however. The planet's constant tug stretches Io's innards, melting moon rock into magma via tidal heating. (Reminder: Lava is just magma that has reached the surface of a planet or moon.)
- Photos: The Galilean Moons of Jupiter
- Photos: Mars Volcano Views Revealed by Spacecraft
- Weird Volcanoes Are Erupting Across the Solar System
Mike Wall's book about the search for alien life, "Out There" (Grand Central Publishing, 2018; illustrated by Karl Tate), is out now. Follow him on Twitter @michaeldwall. Follow us on Twitter @Spacedotcom or Facebook. | 0.90354 | 3.655245 |
A Crab Walks Through Time
Next year marks the 20th anniversary of NASA's Chandra X-ray Observatory launch into space. The Crab Nebula was one of the first objects that Chandra examined with its sharp X-ray vision, and it has been a frequent target of the telescope ever since.
There are many reasons that the Crab Nebula is such a well-studied object. For example, it is one of a handful of cases where there is strong historical evidence for when the star exploded. Having this definitive timeline helps astronomers understand the details of the explosion and its aftermath.
In the case of the Crab, observers in several countries reported the appearance of a "new star" in 1054 A.D. in the direction of the constellation Taurus. Much has been learned about the Crab in the centuries since then. Today, astronomers know that the Crab Nebula is powered by a quickly spinning, highly magnetized neutron star called a pulsar, which was formed when a massive star ran out of its nuclear fuel and collapsed. The combination of rapid rotation and a strong magnetic field in the Crab generates an intense electromagnetic field that creates jets of matter and anti-matter moving away from both the north and south poles of the pulsar, and an intense wind flowing out in the equatorial direction.
The latest image of the Crab is a composite with X-rays from Chandra (blue and white), NASA's Hubble Space Telescope (purple) and NASA's Spitzer Space Telescope (pink). The extent of the X-ray image is smaller than the others because extremely energetic electrons emitting X-rays radiate away their energy more quickly than the lower-energy electrons emitting optical and infrared light.
This new composite adds to a scientific legacy, spanning nearly two decades, between Chandra and the Crab Nebula. Here is a sample of the many insights astronomers have gained about this famous object using Chandra and other telescopes.
1999: Within weeks of being deployed into orbit from the Space Shuttle Columbia during the summer of 1999, Chandra observed the Crab Nebula. The Chandra data revealed features in the Crab never seen before, including a bright ring of high-energy particles around the heart of the nebula.
2002: The dynamic nature of the Crab Nebula was vividly revealed in 2002 when scientists produced videos based on coordinated Chandra and Hubble observations made over several months. The bright ring seen earlier consists of about two dozen knots that form, brighten and fade, jitter around, and occasionally undergo outbursts that give rise to expanding clouds of particles, but remain in roughly the same location.
These knots are caused by a shock wave, similar to a sonic boom, where fast-moving particles from the pulsar are slamming into surrounding gas. Bright wisps originating in this ring are moving outward at half the speed of light to form a second expanding ring further away from the pulsar.
2006: In 2003, the Spitzer Space Telescope was launched and the space-based infrared telescope joined Hubble, Chandra, and the Compton Gamma-ray Observatory and completed the development of NASA's "Great Observatory" program. A few years later, the first composite of the Crab with data from Chandra (light blue), Hubble (green and dark blue), and Spitzer (red) was released.
2008: As Chandra continued to take observations of the Crab, the data provided a clearer picture of what was happening in this dynamic object. In 2008, scientists first reported a view of the faint boundary of the Crab Nebula's pulsar wind nebula (i.e., a cocoon of high-energy particles surrounding the pulsar).
The data showed structures that astronomers referred to as "fingers", "loops", and "bays". These features indicated that the magnetic field of the nebula and filaments of cooler matter are controlling the motion of the electrons and positrons. The particles can move rapidly along the magnetic field and travel several light years before radiating away their energy. In contrast, they move much more slowly perpendicular to the magnetic field, and travel only a short distance before losing their energy.
2011: Time-lapse movies of Chandra data of the Crab have been powerful tools in showing the dramatic variations in the X-ray emission near the pulsar. In 2011, Chandra observations, obtained between September 2010 and April 2011, were obtained to pinpoint the location of remarkable gamma-ray flares observed by NASA's Fermi Gamma Ray Observatory and Italy's AGILE Satellite. The gamma-ray observatories were not able to locate the source of the flares within the nebula, but astronomers hoped that Chandra, with its high-resolution images, would.
Two Chandra observations were made when strong gamma-ray flares occurred, but no clear evidence was seen for correlated flares in the Chandra images.
Despite this lack of correlation, the Chandra observations helped scientists to home in on an explanation of the gamma-ray flares. Though other possibilities remain, Chandra provided evidence that accelerated particles produced the gamma-ray flares.
2014: To celebrate the 15th anniversary of Chandra's launch, several new images of supernova remnants were released, including the Crab Nebula. This was a "three color" image of the Crab Nebula, where the X-ray data were split into three different energy bands. In this image, the lowest-energy X-rays Chandra detects are red, the medium range are green, and the highest-energy X-rays from the Crab are colored blue. Note that the extent of the higher energy X-rays in the image is smaller than the others. This is because the most energetic electrons responsible for the highest energy X-rays radiate away their energy more quickly than the lower-energy electrons.
2017: Building on the multiwavelength images of the Crab from the past, a highly detailed view of the Crab Nebula was created in 2017 using data from telescopes spanning nearly the entire breadth of the electromagnetic spectrum. Radio waves from the Karl G. Jansky Very Large Array (red), Hubble optical data (green), infrared data from Spitzer (yellow), and X-ray data from XMM-Newton (blue) and Chandra (purple) produced a spectacular new image of the Crab.
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Their study, titled “MIRAGE” --- which stands for Measuring Interstellar Reactions of Aromatics by Gas-phase Experiments --- aims to measure chemical reactions of a particular organic molecule, benzene, down to the low temperatures found in interstellar space.
Scientists studying a cold nebula in the Taurus constellation with radio telescopes recently detected an aromatic molecule called benzonitrile. Aromatic molecules contain at least one especially stable hexagonal ring of carbon atoms and are abundant throughout the Universe. Despite this, the detection of benzonitrile marks the first time a specific aromatic molecule has been identified in space using radio astronomy. Its presence in Taurus at very cold temperatures (around -263 °C) is not easy to explain.
The objective of the project
To understand how benzonitrile and other aromatics could form in Taurus, the team led by Ian Sims will conduct laboratory experiments to accurately measure how fast reactions of benzene proceed at different temperatures. To do this, they will use a new technique in development at the Université de Rennes 1 that uses microwave spectroscopy, the same kind of detection technique used in radio telescopes. This apparatus will be able to measure not only the speed of the reaction, but also the proportion of aromatic rings formed compared to other molecules. Scientists at the Green Bank telescope in West Virginia will then use the laboratory data from Rennes to make measurements of other aromatic molecules in cold interstellar space.
European project MIRAGE - Marie S. Curie Action
Funding: European Commission HORIZON 2020 Program
Establishment: Université de Rennes 1
Beneficiary: Ilsa COOKE
Scientific Leader Name: Ian SIMS
Laboratory / UMR: IPR (Institute of Physics of Rennes) UMR CNRS 6251
Duration of the project: From 01/05/2019 to 30/04/2021 (2 years) | 0.907697 | 3.321669 |
Cartography isn’t restricted to the planet that we inhabit. Imagery and maps have long been made for other planets, moons, stars and (recently) comets in our solar system and, indeed, of the solar system itself. They are a key mechanism by which we record information about the surface composition, geology or topography whether that be by remotely sensed imagery or through the capture and analysis of samples from human exploration or robotic means. Being the closest major celestial body to Earth, the Moon is perhaps unsurprisingly the earliest and most detailed to have been mapped to date.
Prepared for the National Aeronautics and Space Administration by U.S. Department of the Interior and U.S. Geological Survey as part of the Geologic Atlas of the Moon, 1:5,000,000, this map was the first of its kind. It was compiled from NASA Lunar Orbiter and Apollo photographs and Soviet Zond photographs as well as geochemical and geophysical data obtained from orbiting spacecraft to show the detailed geological character of the Moon in glorious detail.
The map illustrates the topography as a technicolour mosaic that is almost Jackson Pollock-esque in design. The engaging palette of colours immediately attracts interest in the map which accentuates the strange form of the Lunar landscape. What might appear to be a small design element, the thin black line outlining each feature helps to accentuate the image and delineate one feature from another as distinct forms in contrast to the monotonous appearance of the real landscape. The colours themselves allow the reader to quickly differentiate between neighbouring detail and also to identify where similar information exists elsewhere. It’s also possible to pick out craters and other morphological detail.
The map is in two versions, one that includes geological notation and grids and a version without. It’s a magnificent scientific tool of record and discovery but it’s also a piece of cartographic art and one which has inspired many subsequent maps of the moon and other bodies that generally comprise an interest in planetary cartography. | 0.860738 | 3.259521 |
Our galaxy is teeming with planets unlike those seen in our Solar System, including planets the size of Neptune and larger that orbit their host stars in just a few days. These hot, puffy planets are likely experiencing ongoing atmospheric evaporation. With the recently launched TESS satellite, we expected to discover thousands of new exoplanets, but before investing the evolution of their atmospheres, we need their masses. Stars wobble as their planets’ tug at them gravitationally, and with SALT/HRS we can measure this very small wobble and determine the masses of exoplanets. We are proposing to measure the masses for a few of the most exciting planets that we will discover with TESS.
Scientific papers using data produced by SALT.View publications
Planning a trip to Sutherland? Be sure to book your tour of SALT in advance!Book a tour
RECENT OBSERVATIONS *
HRS study of long-period eclipsing binaries: towards the true mass-luminosity relation. Step two.
Calibrating global parameters and interior structures of massive stars
Probing a galaxy assembly history for the counter-rotating disc galaxy PGC 066551
* Observation titles do not imply any actual discoveries.View more observations | 0.824622 | 3.132552 |
There were emotional scenes at mission control today as space probe Rosetta’s big adventure finally came to an end on the surface of the comet it had been orbiting for two years.
At 11.19 UT, the ESA spacecraft ploughed gently into the dust and rubble of Comet 67P/Churyumov-Gerasimenko, 447 million km from Earth.
At the European Space Operations Centre (ESOC) at Darmstadt, Germany, project scientist Matt Taylor responded to the moment with a single word: “Bugger!” Then he told Skymania News: “I didn’t think I would feel like this. We’ve just killed something.”
Surrounded by the world’s media, Matt held his head in his hands, deep in thought before taking the stage. After praising his team, he added: “I don’t know what to say. Rosetta was rock’n roll. It turned everything up to 11. Rock’n roll, Rosetta!”
Rosetta was expected to take its final picture of the 4.7 metre wide oncoming comet from just 5 metres above the surface. Then, as it collided at walking speed, onboard software automatically switched off all the instruments. But the spacecraft was already unable to communicate any longer, because its antenna no longer pointed at Earth.
The landing reunited the mothership with a fridge-sized companion, called Philae, that it had carried piggyback to the comet. Philae touched down in November, 2014, before bouncing twice into a ditch and losing contact. Rosetta came down just a kilometre – less than a mile – from its former companion.
Rosetta was directed to crash-land as gently as possible in a flat region called Ma’at, an Egyptian name in honour of the Rosetta Stone, a stone tablet from the second century BC that allowed 19th century scholars to decipher ancient Egyptian hieroglyphics.
At 9am UK time, the last commands were sent to the spacecraft to fine-tune its trajectory. It allowed mission controllers to calculate the landing time as 11h 19m 8s, UT. (This is the time the final signal was received on Earth after travelling across space – the actual descent ended about 40 minutes earlier.) As the probe sank lower, it was able to observe how comet material became the observed gas and dust.
The comet is a pristine remnant from the material around before the Sun and planets were made, and scientists hope it will unlock the secrets of how the Solar System formed.
On the descent, scientists were keen to get to a zone called the acceleration region, where material ejected by the comet changes from ice to gas, forming the ghostly halo seen around comets’ heads.
Rosetta was one of the most complex and ambitious space mission ever. It became the first spacecraft to orbit and land on a comet, following a ten-year, four billion mile journey through the Solar System. The mission, which launched in 2004, was full of drama. It gained momentum by flying past Earth, taking a stunning crescent image and Mars. On one approach to Earth, it was briefly mistaken for a threatening asteroid!
On the way it flew past two asteroids – Steins in September, 2008, and Lutetia, in July 2010, sending back pictures. Then it went into hibernation in July 2011 to save energy for the final leg of its journey.
In January 2014, to the great relief of the mission team, Rosetta woke up on schedule and “phoned home”. Then, as it neared its target comet, named after the two Ukrainian astronomers who discovered it, they got a big surprise. Instead of resembling a giant snowball, 67P/Churyumov-Gerasimenko looked more like a rubber duck, with two separate lobes.
The next big event was the landing of Rosetta’s fridge-sized companion probe, Philae, which was sent to land on the comet on November 12, 2014. But its harpoons failed to fire and the little probe bounced twice before ending up trapped in a crevasse. Despite that, it sent back valuable data for three days before, unable to receive any sunlight to charge its batteries, it fell silent.
The final part of ESA’s charming Rosetta animation ends with a surprise. Credit: ESA
During 2015, the comet reached its closest point to the Sun and became highly active, spewing out vast jets of gas and dust which made it too dangerous for Rosetta to get close.
Mission controllers did not know exactly where Philae had ended up, and it was only located earlier this month when Rosetta was finally able to move in and take high-resolution photos. Even so, it was like trying to find a needle in a haystack.
By mission’s end, Rosetta had flown a distance of 7.9 billion km.
Professor Ian Wright, of the UK’s Open University, told Skymania News: “Unquestionably, we have now got data which is going to help us learn more about the origins of the Solar System. The data has been coming down faster than anyone can deal with. It is just piling up. Which is great.
“Will it help us discover the origin of life? Any time you study the chemistry of alien bodies, there is the potential to make some connection. What we will know at the end of the mission is that this was the likely collection of materials from four and a half billion years ago at the start of the Solar System. So if you took that package, along with its inorganic components, and all the rest of it, and then put it in the right environment, is that ultimately how life got started?”
★ Keep up with space news and observing tips. Click here to sign up for alerts to our latest reports. No spam ever - we promise! | 0.857237 | 3.122527 |
Using Chandra observations, astronomers have discovered one of the nearest supermassive black holes to Earth that is currently undergoing powerful outbursts. Such outbursts are part of the “feedback” process that is important to the evolution of the black hole and its host galaxy.
Evidence for powerful blasts produced by a giant black hole has been discovered using NASA’s Chandra X-ray Observatory. This is one of the nearest supermassive black holes to Earth that is currently undergoing such violent outbursts.
Astronomers found this outburst in the supermassive black hole centered in the small galaxy NGC 5195. This companion galaxy is merging with a large spiral galaxy NGC 5194, also known as “The Whirlpool.” Both of these galaxies are in the Messier 51 galaxy system, located about 26 million light years from Earth.
“For an analogy, astronomers often refer to black holes as ‘eating’ stars and gas. Apparently, black holes can also burp after their meal,” said Eric Schlegel of The University of Texas in San Antonio, who led the study. “Our observation is important because this behavior would likely happen very often in the early universe, altering the evolution of galaxies. It is common for big black holes to expel gas outward, but rare to have such a close, resolved view of these events.”
In the Chandra data, Schlegel and his colleagues detect two arcs of X-ray emission close to the center of NGC 5195.
“We think these arcs represent fossils from two enormous blasts when the black hole expelled material outward into the galaxy,” said co-author Christine Jones of the Harvard-Smithsonian Center for Astrophysics (CfA) in Cambridge, Mass. “This activity is likely to have had a big effect on the galactic landscape.”
Just outside the outer X-ray arc, the researchers detected a slender region of emission of relatively cool hydrogen gas in an optical image from the Kitt Peak National Observatory 0.9-meter telescope. This suggests that the hotter, X-ray emitting gas has “snow-plowed,” or swept up, the hydrogen gas from the center of the galaxy. This is a clear case where a supermassive black hole is affecting its host galaxy in a phenomenon that astronomers call “feedback.”
In NGC 5195, the properties of the gas around the X-ray-glowing arcs suggest that the outer arc has plowed up enough material to trigger the formation of new stars.
“We think that feedback keeps galaxies from becoming too large,” said co-author Marie Machacek of CfA. “But at the same time, it can be responsible for how some stars form. This shows that black holes can create, not just destroy.”
The astronomers think the outbursts of the supermassive black hole in NGC 5195 may have been triggered by the interaction of this smaller galaxy with its large spiral companion, causing gas to be funneled in towards the black hole. The energy generated by this infalling matter would produce the outbursts. The team estimates that it took about one to three million years for the inner arc to reach its current position, and three to six million years for the outer arc.
The arcs are also significant because of their location in the galaxy. They are well outside the region where rapid outflow, or winds, have been detected from active supermassive black holes in other galaxies, yet inside the much larger cavities and filaments observed in the hot gas around many massive galaxies. As such they may represent a rare view an intermediate stage in the feedback process operating between the interstellar gas and the black hole.
These results were presented in January 2016 at the 227th meeting of the American Astronomical Society meeting in Kissimmee, FL, and have been submitted in a paper to The Astrophysical Journal. Laura Vega, of the Fisk University and Vanderbilt University Bridge Program, in Nashville, Tennessee was also a co-author of the paper. NASA’s Marshall Space Flight Center in Huntsville, Alabama, manages the Chandra program for NASA’s Science Mission Directorate in Washington. The Smithsonian Astrophysical Observatory in Cambridge, Massachusetts, controls Chandra’s science and flight operations. | 0.805157 | 4.093453 |
Authors: Hanno Rein and Daniel Tamayo
First Author’s Institution: Department of Physical and Environmental Sciences, University of Toronto at Scarborough
Status: Submitted to MNRAS, open access
It is simply astronomical, everything in astronomy: there are too many objects, everything happens on mega glacial time scale over mega glacial distance, space is too big, and objects are almost always certainly too faint. With our finite resources and human lifetimes, it is impossible to observe everything and to follow their evolution religiously from the beginning to the end. However, (super)computers have endowed astronomers with divine powers, allowing us to manipulate the Universe at our fingertips. In the absence of data, they are also the next favorite playgrounds to put theories to the test. Simulations have become the bread and butter of astronomical research.
The underlying schemes used in simulations can be divided into those that deal with collisional fluid (hydrodynamics simulations) and those that deal with pure gravitational dynamics (N-body simulation), although there are growing instances of hybrid simulations. The Millennium Simulation is an example of an N-body simulation. In today’s bite, we focus on N-body simulation and discuss a numerical method (aka an integrator) that solves a problem facing all dynamical integrators, which is that of time-reversibility.
If we back-evolve a system under the influence of gravity after some time by reversing the sign of the velocity of each particle, it should faithfully return to its initial configuration. This is because the equations of motion in gravitational problems are the same under the reversal of time. However, this time reversibility is not satisfied by current numerical methods, even ones that are time-symmetric by construction. This is because floating point operations which are widely used in numerical methods are not reversible due to rounding errors (loss of digits). When there are multiple successive floating point operations, the loss of digits from each operation accumulates and makes it impossible to recover the initial conditions. The authors of today’s paper got around this problem using integer operations, which are exactly precise.
The authors adapted a standard integrator known as leapfrog into its integer-ized version, which they call JANUS. In the leapfrog method, given initial positions (x0, y0) at t=0 and initial velocity v1/2 at t=1/2, the positions of the particles are leapfrogged forward to t=1 based on the half time-step velocity v1/2, and the velocity to t=3/2 based on the new positions. The positions and velocities at subsequent times are updated similarly; here is a simple visual. In this paper, rather than floating point numbers, the authors stored the position and velocity of each particle as integers on an extremely fine grid, where the resulting relative accuracy can be as good as or better than that of double precision numbers. However, they still need to perform floating point arithmetic to evaluate the gravitational forces and because of divisions and multiplications. What makes their method precisely reversible is that these floating point operations are performed in the middle of each time step which are then rounded to the nearest integer on the grid, ensuring that the same floating point number is retrieved going forward and backward. The final operations are then done in integers.
The authors tested the time-symmetry of JANUS by studying the gravitational collapse of 1000 particles. The particles are evolved forward for a certain time until they collapse, after which the velocities of the particles are reversed and they are then evolved backward for the same amount of time. Figure 1 compares the result using JANUS and the leapfrog integrator. Using JANUS, the authors are able to recover the initial conditions of all the particles exactly. This holds as well for simulations at longer times.
What about an even more complicated dynamical system, such as that of our Solar System? Veiled by the seemingly stable motion of the planets over human history, the Solar System is actually chaotic — think the butterfly effect on a much larger and slower scale, where a different starting position of Earth by mere meters would cause it to end up in a completely different orbit in over 5 Myr. In other words, it would be impossible to predict the location of our planet beyond ~ 5 Myr if we do not know its position to better than meters today. The authors used JANUS to study the evolution of our Solar System for 300 Myr and ran 24 simulations where the initial position of Mercury is perturbed by 1 m each time. Figure 2 shows the differences in the eccentricity of Mercury between pairs of simulations over 300 Myr. Any pairs of simulation diverge exponentially over 6.5 Myr (red line), which is consistent with a 5 Myr chaotic time scale found by previous studies.
It is important to note that the robustness of results from previous integrators suggest that time-reversibility is not a limiting feature for accurately representing reality. Nonetheless, with time-reversibility, one can imagine being able to recover the present-day Solar System from simulations with close gravitational encounters between/among the planets and to perform backward integration of cosmological simulations for various interesting studies. A practically time-reversible integrator therefore opens up doors to intriguing venues of exploration. | 0.851162 | 3.810051 |
In the latter 1700’s Charles Messier, a French astronomer, compiled a list of approximately 100 visible night sky objects that were difficult to distinguish from comets through the available telescopes of those times. Comet hunting was a way to make a name for yourself in astronomy in those days and Messier wanted to create a list to help distinguish deep sky objects from comets.
Today, the Messier Catalog is considered a collection of some of the most magnificent objects in the sky including nebulae, star clusters, and galaxies. Each year in March or early April, all 110 recognized Messier objects are visible from the northern hemisphere which makes the perfect time for amateur astronomers to view them.
In the 70’s Messier Marathon became popular and now represent the culmination of viewing these celestial objects. The marathon is an attempt by amateur astronomers to find as many Messier objects as possible in one night with the ultimate goal of finding all 110 in one viewing.
This year a New Moon will occur on March 24 and many astronomy clubs and individuals will participate in Messier Marathons on the weekends of March 21/22 (primary time to view) and March 28/29, 2020 (secondary time to view). On both these dates, there will be a good opportunity to attempt to hunt down all Messier Objects in one night from suitable northern latitude locations.
Messier objects not evenly distributed in the nighttime sky. There are heavily crowded regions in the sky, especially the Virgo Cluster and the region around the Galactic Center, while other regions are virtually empty of them. In particular, there are no Messier objects at all at Right Ascensions 21:40 to 23:20, and only the very northern M52 is between RA 21:40 and 0:40.
You can learn more here. | 0.867657 | 3.191283 |
Using ground penetrating radar the European Space Agency has detected liquid water underneath the frozen Planum Astrale region of Mars. By observing how electromagnetic waves reflect off different layers underground they’ve spotted signals characteristic of liquid water.
On Wednesday, the research was published by the Italian Space Agency in the journal Science
This data was obtained by the Mars Advanced Radar for Subsurface and Ionosphere Sounding instrument i.e. MARSIS on the European Space Agencys Mars Express Spacecraft
Mars Express Spacecraft courtesy of ESA
The presence of liquid water on Mars has implications for astrobiology i.e. the possibility extraterrestrial life, as well as space exploration and colonization. Water can be used for life support or to create fuel via hydrolysis both of which are vital to humanities continued expansion in to outer space.
MARSIS surveyed the Planum Australe region between May 2012-December 2015 sending radar pulses through polar ice caps. Using this method which is central to dozens of surveillance technologies patented by the US government, they obtained 29 different samples which indicate a drastic change almost one mile below the surface.
This anomaly appeared very similar to lakes underneath the Greenland and Antarctican ice sheets indicating a divergence from surrounding solid matter due to an increase in reflectivity.
“Quantitative analysis of the radar signals shows that this bright feature has high relative dielectric permittivity (>15), matching that of water-bearing materials. We interpret this feature as a stable body of liquid water on Mars.”
The anomaly stretched for 12.5 miles across Planum Australe.
From Journal Science
“This is just one small study area; it is an exciting prospect to think there could be more of these underground pockets of water elsewhere, yet to be discovered,” said Roberto Orosei in a statement. Orosei is the lead study author and principal investigator of the MARSIS experiment.
Since the readings were taken below one of the coldest regions on Mars you ‘d expect that it would remain frozen however salt compounds found on the planet could theoretically aid in retaining a liquid state by creating a type of brine. The pressure of the ice above it may play a role as well. More dense solid matter floats to the top of liquid similar to how lakes are frozen at the surface on Earth. So technically any liquid water would be more likely to exist underneath ice rather then on the surface.
Example of Underground Lake on Earth @ Lost Sea
“The long duration of Mars Express, and the exhausting effort made by the radar team to overcome many analytical challenges, enabled this much-awaited result, demonstrating that the mission and its payload still have a great science potential,” said Dmitri Titov in a statement, Mars Express project scientist.
“This thrilling discovery is a highlight for planetary science and will contribute to our understanding of the evolution of Mars, the history of water on our neighbor planet and its habitability.”
“The lake could possibly host life, despite the extreme cold and salinity, as microbes survive on Earth in similar conditions”, claims lead author Roberto Orosei.
“It is not a place where life would be expected to have an easy time, but it is possible based upon terrestrial analogues,” said the researcher, who also serves as principal investigator of the MARSIS experiment. | 0.835802 | 3.574617 |
Using data acquired by the Hubble Space Telescope, scientists at NASA have updated their maps of Jupiter. The new images — shown in 4K ultra high definition — reveal changes to the Great Red Spot and rare waves not seen since the Voyager 2 mission.
NASA updates its maps of Jupiter each year, but this year’s project proved to be particularly fascinating.
The two new maps were captured by Hubble’s high-performance Wide Field Camera 3 and analysed by planetary scientists at NASA’s Goddard Space Flight Center in Greenbelt, Maryland. The maps, which show back-to-back rotations of the planet, make it possible to study a broad range of features, including winds, clouds, storms, and atmospheric chemistry.
Close-ups of the Great Red Spot reveals a unique filamentary feature not previously seen. (Image and caption credit: NASA/ESA/Goddard/UCBerkeley/JPL-Caltech/STScI)
Analysis of the Great Red Spot shows that it’s getting smaller and more circular. The spot, which is now more orange than red, measures 150 miles (240 km) along its long axis. The NASA scientists noticed an unusual wispy filament within the spot, which has never been seen before. This filamentary streamer is being tossed around by winds reaching upwards of 330 mph (150 meters/second).
This false-colour close-up of Jupiter shows cyclones (arrows) and the elusive wave (vertical lines). (Image and caption credits: NASA/ESA/Goddard/UCBerkeley/JPL-Caltech/STScI)
The scientists also noticed a rare wave just north of the planet’s equator. The phenomenon was first spotted by the Voyager 2 spacecraft during its historic flyby in 1979, but hasn’t been seen since. The wave is situated in an area replete with cyclones and anticylones. Similar waves, called baroclinic waves, have been seen in Earth’s atmosphere where cyclones are forming.
[ NASA ] | 0.852039 | 3.585662 |
NASA had everyone excited when they announced the discovery of a planetary system with seven Earth-sized planets around the star Trappist-1 last week, but noted astrophysicist Neil deGrasse Tyson has some bad news for the alien hunters out there. He says that Trappist-1, being a red dwarf, just might have blasted its train of worlds with its plasma and electromagnetic particles to the point of being uninhabitable.
Neil deGrasse Tyson, in speaking with TMZ via video chat, told the celebrity news outlet that although the discovery of the seven planets was great news, there was a “problem they did not tell you in the headlines” about the newly discovered exoplanets.
“Because the star is a dwarf — it’s small — it’s still generating energy and the like, but it’s not as hot as the Sun is. Red dwarf stars a hugely turbulent on their surface and they are spewing forth plasma particles at high speeds.
Tyson went to say that scientists do calculations of the “spewing,” which is known as solar winds in the Solar System. “This can ablate [process of removal through melting, vaporization, erosion, etc.]” — Tyson accompanies this explanation with a sweeping away motion of his hands — “a planet’s atmosphere, and so it is likely that any atmosphere these seven planets had have been completely stripped from them billions of years ago.”
Still, the scientist told TMZ that there was still a possibility that life might exist on the Trappist-1 planets.
Early excitement over the discovery of the planet, Proxima b, around the nearest stellar neighbor, Proxima Centauri, produced all sorts of speculation on whether or not there was a chance the planet might be habitable, what manner of alien life might thrive there, how long it might take to get there and how long it might take to detect and/or confirm the presence of life. But Proxima b also orbits a red dwarf star, which fires off, according to NASA, “torrents of X-ray and extreme ultraviolet radiation from superflares occurring roughly every two hours.” Its close proximity to its parent star (0.05 AU, where 1.0 AU — Astronomical Unit — would equal the distance between the Sun and the Earth) and the red dwarf’s age, along with the two-hour bombardments, suggest that life on Proxima b, at least as we understand it, could not survive.
Scientists from NASA concluded (per Wired) that the harsh X-ray and ultraviolet radiation slamming into the planet would dissipate any atmosphere like Earth’s and any oxygen in Planet b’s atmosphere would dissipate within 10 million years. That lack of oxygen would also contribute to the planet not having liquid water on its surface.
The work of the NASA scientists, which was published in The Astrophysical Journal Letters in early February, found that planets orbiting young red dwarfs would likely suffer similar fates.
Which is more bad news for future astronomical discoveries around red dwarf stars…
But Neil deGrasse Tyson was upbeat about future discoveries. He told TMZ that the discovery of seven exoplanets revolving around Trappist-1 gave scientists “confidence that there may be more planets than stars in the galaxy.”
And even though the chances of finding life on a Trappist-1 world, where new research suggests that the number of planets orbiting in the star’s habitable zone could be upgraded from three to four, might be exceeding slim to none, Tyson did leave alien hunters with the consolation of knowing that alien life, when (if?) eventually discovered, might not fit into the biological parameters that necessitate life on Earth.
“So how many possible ways exist for being alive comes the next question we should all be asking,” he said.
Which then reopens the door to the possibility of alien life on a Trappist-1 planet. Very alien life, as it were, but life.
And so the search for alien life continues…
[Featured Image by manjik/Shutterstock] | 0.846934 | 3.364494 |
NASA's mission to explore the two largest objects in the → asteroid belt, the asteroid Vesta and the → dawarf planet Ceres, gathering data relating to their composition, internal structure, density and shape. Launched in September 2007, Dawn entered the orbit of → Vesta in July 2011 and spent 16 months there before leaving for → Ceres. It entered Ceres orbit on March 6, 2015. The Dawn spacecraft is made of aluminium and graphite composite, it has a dry mass of 747.1 kg and a mass of 1217.7 kg when fully fuelled prior to launch. The spacecraft is a box-shaped design measuring 1.64m × 1.27m × 1.77m.
Fr.: sonde Galileo
A space mission whose main goal was to explore → Jupiter and its moons and rings. The spacecraft was launched on October 19, 1989, arrived at Jupiter in December 1995. It disappeared on September 21, 2003, after eight years orbiting Jupiter, when mission controllers crashed it into → Jupiter's atmosphere. On December 7, 1995, Galileo's probe dived into Jupiter's atmosphere, and measured atmospheric pressure, density, and composition, and explored the planet's → radiation belts. Galileo had two parts: an orbiter and a descent probe that parachuted into Jupiter's atmosphere. The orbiter sent back hundreds of pictures of the four large → Galilean satellites of Jupiter (→ Io, → Europa, → Ganymede, and → Callisto). It made many discoveries during its eight years looping around Jupiter. It found evidence for layers of salt water below the surface on Europa, Ganymede, and Callisto, and measured high levels of volcanic activity on Io. When → Shoemaker-Levy slammed into Jupiter in 1994, Galileo had the only direct view of the → comet striking Jupiter's atmosphere. Galileo determined that → Jupiter's rings are formed from dust hurled up by → meteorite impacts on planet's inner moons. Measurements by the orbiter's → magnetometer revealed that Io, Europa, and Ganymede have metallic cores, while Callisto does not. Also, Galileo discovered that Ganymede possesses its own → magnetic field; it is the first moon known to do so. The orbiter also found that the Galilean satellites all have thin atmospheres. During it's trip from Earth to Jupiter, Galileo passed by and studied two asteroids: → Gaspra in 1991 and → Ida in 1993, around which it discovered → Dactyl, the first moon orbiting an asteroid (windows2universe.org).
teleskop-e fazâyi-ye Kepler
Fr.: télescope spatial de Kepler
A → NASA space telescope launched in March 2009 to discover Earth-size planets using the → transit method. The telescope has a diameter of 0.95 m and its only instrument is a → photometer that continuously monitors the brightness of over 145,000 → main sequence stars in a fixed field of view of 115 deg2 (about 12° diameter). The expected mission lifetime is 3.5 years extendible to at least 6 years.
Fr.: vaisseau spatial | 0.886122 | 3.836332 |
Relevant Degree Programs
Graduate Student Supervision
Doctoral Student Supervision (Jan 2008 - Nov 2019)
Observations suggest that almost half of the total light emitted by stars in the Universe is absorbed by dust, and the emission is re-radiated at far-infrared and submillimeter wavelengths. Dusty star-forming galaxies play a significant role in the stellar mass build-up at high redshift, but their contribution to the cosmic star formation rate density at z > 4 is still unknown, due to the currently limited availability of statistically significant high-redshift dusty galaxy samples. In this thesis we analyze data from two large area surveys, the HerMES Large Mode Survey (HeLMS) and the Herschel Stripe 82 Survey (HerS), observed with the Herschel-SPIRE instrument at far-infrared wavelengths of 250, 350 and 500 μm. We describe the process of constructing maps from detector data that provide an unbiased estimate of the sky signal, then we use a map-based detection method to assemble a large catalog of candidate z > 4 dusty star-forming galaxies detected in HeLMS. The large area of the survey allows us to detect a significant number of sources and we are able to determine the differential number counts of these galaxies at 500 μm. We find an excess of such high-redshift galaxies compared to model predictions, and our counts suggest strong evolution in their properties.We examine the properties of our sources at different wavelengths. Follow-up observations with ALMA, SCUBA-2 and ACT strengthen our initial assumption that the detected population consists of high-z dusty galaxies with their spectrum dominated by thermal dust emission, best fitted with an optically thick modified blackbody. These follow-up observations also allow us to examine the biasing effects in our number counts due to blending of nearby sources. We also investigate the mean dusty star formation activity in moderate redshift massive galaxy clusters detected by the Atacama Cosmology Telescope. We find that, on average, there is an excess of far-infrared emission in the line of sight of these clusters. Finding dusty star-forming galaxies in massive clusters implies that the environment can affect the star formation activity in galaxies.
Observations of the Cosmic Microwave Background (CMB) are crucial components of our understanding of cosmology. Modern high resolution, ground-based CMB survey instruments provide important information about the mass and energy content of our present Universe and the high-energy physics of the Big Bang.In this work we present several aspects of our work on the Atacama Cosmology Telescope (ACT), a 6m telescope in Northern Chile that observed the CMB in three millimetre wavelength bands from 2007–2010. We begin with a description of the Multi-Channel Electronics readout system, an important component of the data acquisition systems for ACT and several other CMB observatories. The system provides room-temperature electronics and software for controlling and reading out arrays of Transition Edge Sensor bolometers via a cryogenic time-domain multiplexing system.We next present our measurement of the ACT point spread function, or beam, using observations of Solar System planets. An accurate understanding of the beam and its covariant error is essential for interpretation of astrophysical and cosmological signal in the ACT data. We then use our understanding of the beam and the instrument calibration to measure the brightness temperatures of Uranus and Saturn at millimetre wavelengths. Precise measurements of planetary brightnesses provide convenient calibration sources for other observatories at these wavelengths.Finally we present a sample of galaxy clusters detected in the ACT maps. We develop a new approach for the analysis of Sunyaev-Zeldovich signal that incorporates a model for the typical cluster pressure to better understand selection effects and evaluate cluster masses. Addressing the current level of systematic uncertainty in the overall mass calibration of clusters, we explore the cosmological constraints obtained when calibrating the mass relation based on pressure profile measurements from X-ray data and from models that take different approaches to the cluster physics. Ultimately we use dynamical mass estimates based on optical velocity dispersion measurements to obtain constraints on the amplitude of scalar fluctuations, the matter density, the Dark Energy equation of state parameter, and the sum of the neutrino mass species.
Master's Student Supervision (2010 - 2018)
CHIME is a new radio interferometer located at the Dominion Radio Astrophysical Observatory (DRAO) in Penticton, BC. The primary goal of CHIME is to constrain the dark energy equation of state by measuring the expansion history of the Universe using the Baryon Acoustic Oscillation (BAO) scale as a standard ruler. CHIME consists of 4 cylindrical reflectors, each populated with 256 dual-polarization antennas along its focal-line. Prior to digitization, each signal chain consists of a low noise amplifier, 50m of coaxial cable, and a filter amplifier. In order to obtain accurate interferometric imaging, we need to determine the relative complex gain (amplitude and phase vs. frequency) of each analog chain to 0.3%. The complex gain of each receiver depends primarily on temperature. This thesis discusses efforts to construct a thermal model of the CHIME’s coaxial cables that will allow us to meet our calibration requirements.
A compact, wide-bandwidth, dual-polarization cloverleaf-shaped antenna has been developed to feed the CHIME radio telescope. The antenna has been tuned using a commercial antenna simulation program, CST, to have a very good impedance match to our amplifiers. Specifically, the return loss is smaller than -10dB for over an octave of bandwidth, covering the full CHIME band from 400MHz to 800MHz and this performance has been confirmed by measurement. The antennas are made of conventional low-loss circuit boards and can be mass produced economically, which is important because CHIME requires 1280 feeds. They are compact enough to be placed 30cm apart in a linear array at any azimuthal rotation. 128 of these feeds have now been built, tested and deployed on CHIME pathfinder.
The Canadian Hydrogen Intensity Mapping Experiment (CHIME) will measure the distribution of neutral hydrogen in the universe to constrain dark energy models. A two element radio interferometer operating between 425 and 850 MHz was built at the Dominion Radio Astrophysical Observatory as a CHIME technology prototype. The system temperature is approximately 80 K midband, of which almost 40 K is caused by feed loss and ground spill. A band defining filter used in the receiver allows the signal to be alias sampled at 850 MHz and unfolded to 425-850 MHz. Delayed crosstalk between channels in the interferometer causes prominent spectral ripple with 3.8 MHz period in the cross correlations. Further baseline spectral ripple with 41 MHz period is caused by standing waves between the reflector and the feed ground plane. Sky maps between declinations 52° | 0.915578 | 4.051368 |
As Nasa’s rover Curiosity seeks to answer the question ‘Is there life on Mars?’, scientists elsewhere have found the first evidence of a planetary body outside our solar system that was potentially capable of having once sustained life
The shattered remains of a planetary body, or asteroid, are currently orbiting a white dwarf star called GD 61 and are about 170 light years away from Earth, according to astronomers at the Universities of Warwick and Cambridge. Both rocks and water have been detected on the asteroid; two ‘ingredients’ considered vital for the origin of life.
Researchers believe the asteroid comprises remnants from a small watery planet that was knocked out of its original orbit and pulled so close to its sun that it was broken up in the process.
Professor Boris Gänsicke, from the department of physics at the University of Warwick, said: “At this stage in its existence, all that remains of this rocky body is simply dust and debris that has been pulled into the orbit of its dying parent star.
“However, this planetary graveyard swirling around the embers of its parent star is a rich source of information about its former life.”
Jay Farihi from Cambridge’s Institute of Astronomy said: “Our results demonstrate that there was definitely potential for habitable planets in this exoplanetary system.” | 0.900426 | 3.231745 |
Carbonaceous chondrites or C chondrites are a class of chondritic meteorites comprising at least 8 known groups and many ungrouped meteorites. They include some of the most primitive known meteorites. The C chondrites represent only a small proportion (4.6%) of meteorite falls.
|— Class —|
|Alternative names||C chondrites|
Composition and classificationEdit
Carbonaceous chondrites are grouped according to distinctive compositions thought to reflect the type of parent body from which they originated. These C chondrite groups are now each named with a standard two-letter CX designation, where C stands for "carbonaceous" (other types of chondrites do not begin with this letter) plus a capital letter in the spot X, which is very often the first letter of the name of a prominent meteorite—often the first to be discovered—in the group. Such meteorites are often named for the place where they fell, thus giving no clue as to the physical nature of the group. Group CH, where H is for "high metal" is so far the only exception. See below for name derivations of each group.
Several groups of carbonaceous chondrites, notably the CM and CI groups, contain high percentages (3% to 22%) of water, as well as organic compounds. They are composed mainly of silicates, oxides and sulfides, with the minerals olivine and serpentine being characteristic. The presence of volatile organic chemicals and water indicates that they have not undergone significant heating (>200 °C) since they were formed, and their compositions are considered to be close to that of the solar nebula from which the Solar System condensed. Other groups of C chondrites, e.g., CO, CV, and CK chondrites, are relatively poor in volatile compounds, and some of these have experienced significant heating on their parent asteroids.
This group, named after the Ivuna meteorite (Tanzania), have chemical compositions that are close to that measured in the solar photosphere (aside from gaseous elements, and elements such as lithium which are underrepresented in the Sun's photosphere by comparison to their abundance in CI chondrites). In this sense, they are chemically the most primitive known meteorites.
CI chondrites typically contain a high proportion of water (up to 22%), and organic matter in the form of amino acids and PAHs. Aqueous alteration promotes a composition of hydrous phyllosilicates, magnetite, and olivine crystals occurring in a black matrix, and a possible lack of chondrules. It is thought they have not been heated above 50 °C (122 °F), indicating that they condensed in the cooler outer portion of the solar nebula.
Six CI chondrites have been observed to fall: Ivuna, Orgueil, Alais, Tonk, Revelstoke, and Flensburg. Several others have been found by Japanese field parties in Antarctica. In general, the extreme fragility of CI chondrites causes them to be highly susceptible to terrestrial weathering, and they do not survive on Earth's surface for long after they fall.
CV chondrites observed falls:
The group takes its name from Mighei (Ukraine), but the most famous member is the extensively studied Murchison meteorite. Many falls of this type have been observed and CM chondrites are known to contain a rich mix of complex organic compounds such as amino-acids and purine/pyrimidine nucleobases. CM chondrite famous falls:
CR chondrites observed falls:
Other famous CR chondrites:
"H" stands for "high metal" because CH chondrites may contain up to as much as 40% of metal. That makes them the most metal-rich of any chondrite group. The first meteorite discovered was ALH 85085. Chemically, these chondrites are closely related to CR and CB groups. All specimens of this group belong only to petrologic types 2 or 3.
The group takes its name from the most representative member: Bencubbin (Australia). Although these chondrites contain over 50% nickel-iron metal, they are not classified as mesosiderites because their mineralogical and chemical properties are strongly associated with CR chondrites.
The group takes its name from Ornans (France). The chondrule size is only about 0.15 mm on average. They are all of petrologic type 3.
Famous CO chondrite falls:
The most famous members:
Ehrenfreund et al. (2001) found that amino acids in Ivuna and Orgueil were present at much lower concentrations than in CM chondrites (~30%), and that they had a distinct composition high in β-alanine, glycine, γ-ABA, and β-ABA but low in α-aminoisobutyric acid (AIB) and isovaline. This implies that they had formed by a different synthetic pathway, and on a different parent body from the CM chondrites. Most of the organic carbon in CI and CM carbonaceous chondrites is an insoluble complex material. That is similar to the description for kerogen. A kerogen-like material is also in the ALH84001 Martian meteorite (an achondrite).
The CM meteorite Murchison has over 70 extraterrestrial amino acids and other compounds including carboxylic acids, hydroxy carboxylic acids, sulphonic and phosphonic acids, aliphatic, aromatic and polar hydrocarbons, fullerenes, heterocycles, carbonyl compounds, alcohols, amines and amides.
- Bischoff, A.; Geiger, T. (1995). "Meteorites for the Sahara: Find locations, shock classification, degree of weathering and pairing". Meteoritics. 30 (1): 113–122. Bibcode:1995Metic..30..113B. doi:10.1111/j.1945-5100.1995.tb01219.x. ISSN 0026-1114.
- Norton, O. Richard (2002). The Cambridge Encyclopedia of Meteorites. Cambridge: Cambridge University Press. pp. 121–124. ISBN 978-0-521-62143-4.
- Ehrenfreund, Pascale; Daniel P. Glavin; Oliver Botta; George Cooper; Jeffrey L. Bada (2001). "Extraterrestrial amino acids in Orgueil and Ivuna: Tracing the parent body of CI type carbonaceous chondrites". Proceedings of the National Academy of Sciences. 98 (5): 2138–2141. Bibcode:2001PNAS...98.2138E. doi:10.1073/pnas.051502898. PMC 30105. PMID 11226205.
- Wing, Michael R.; Jeffrey L. Bada (1992). "The origin of the polycyclic aromatic hydrocarbons in meteorites". Origins of Life and Evolution of the Biosphere. 21 (5–6): 375–383. Bibcode:1991OLEB...21..375W. doi:10.1007/BF01808308.
- "Carbonaceous chondrite" Meteorite.fr: All About Meteorites: Classification Archived 2009-10-12 at the Wayback Machine
- Nemiroff, R.; Bonnell, J., eds. (28 April 2012). "Sutter's Mill Meteorite". Astronomy Picture of the Day. NASA. Retrieved 2012-05-06.
- Pearce, Ben K. D.; Pudritz, Ralph E. (2015). "Seeding the Pregenetic Earth: Meteoritic Abundances of Nucleobases and Potential Reaction Pathways". Astrophysical Journal. 807 (1): 85. arXiv:1505.01465. Bibcode:2015ApJ...807...85P. doi:10.1088/0004-637X/807/1/85.
- Norton, O. Richard (2002). The Cambridge Encyclopedia of Meteorites. Cambridge: Cambridge University Press. p. 139. ISBN 978-0-521-62143-4.
- Carbonaceous chondrites at The Encyclopedia of Astrobiology, Astronomy, and Spaceflight
- Gilmour, I.; Wright, I.; Wright, J. (1997). Origins of earth and life. Bletchley: The Open University. ISBN 978-0-7492-8182-3.
|Wikimedia Commons has media related to Carbonaceous chondrites.|
- Carbonaceous Chondrite Images from Meteorites Australia - Meteorites.com.au | 0.834516 | 4.007628 |
Mineral dusts in the atmosphere, originating primarily from dry regions like the Sahara desert, have significant influence on climate. Because of this they need to be accurately represented in climate and weather prediction models. Recent observations of atmospheric Saharan dust by our scientists provide strong evidence for the existence in mineral dust layers of particles that are predominantly vertically aligned. This finding is totally unexpected, as until now atmospheric aerosol particles have been thought to be randomly aligned. The alignment is thought to be due to atmospheric electricity associated with the dust layers. Computer modelling indicates that the alignment can significantly alter the properties of the dust layers, including the amount of light they transmit, absorb and reflect. This has been termed a "Venetian blind effect" from the way particle "tilt" can influence the amount of light and heat transmitted through the atmosphere. Change in this and other properties can have significant impact on measurements of dust clouds from satellites and ground-based remote sensing instruments, and possibly also on dust movement through the atmosphere.
The observations, described in a paper published in Atm. Chem. Phys. 7, pp.6161-6173 (2007) were carried out on La Palma in the Canary Islands (shown at a later date in the image above). Our team used a very high-sensitivity instrument for measuring the polarization of light. This PlanetPol polarimeter was developed jointly by Centre for Atmospheric and Climate Physics (CACP) and the Centre for Astrophysics Research (CAR), initially for use in astronomy. The observations coincided with a dust storm which, for a brief period, between 3rd and 7th May 2005 stretched from the Sahara to cover La Palma - see the AURA-OMI satellite image animation showing daily "aerosol index" over the Atlantic between south America and north Africa.
A long-standing puzzle surrounds long-range transport of atmospheric dust, namely that large particles are frequently observed in the atmosphere where according to models they should have been removed by gravitational settling. It is now well documented that a hitherto unknown atmospheric process appears to slow down the so called "dry deposition" of larger dust particles (see e.g. Maring et al. (2003) J. Geophys. Res. 108, 8592). To provide a potential explanation, we have proposed that the electric field associated with the alignment can also modify dust transport by aiding the retention of charged, larger particles within dust layers [ACP 7, p.6161]. The process works like this. Small and large dust particles tend to be charged with opposite polarity. Since larger particles fall faster under gravity, separate areas of positive and negative charge will form. The resulting electric field can then counteract gravitational settling of larger particles by coupling them to smaller ones via electrostatic attraction. This coupling effectively increases the surface area of large particles, slowing down their settling (generally, large particles tend to dominate by mass, while small ones dominate by surface area). We have now modelled this process and the results indicate that particles as large as 8 micrometers can be effectively "levitated" by the electric field. The plots below compare the vertical concentration profiles of 0.2 and 8 micron particles, initially and after 4 days of transport through the atmosphere, with and without the effect of dust charging.
A field campaign called DREAME (Dust Radiation, Electrification and Alignment in the Middle East) will take place in Kuwait and Saudi Arabia in April and May 2009. The campaign will answer questions concerning the precise origin, magnitude, extent and impact of the dust-charging phenomenona by the use of sun photometry, optical polarimetry, lidar, and in situ measurements of electrical properties and particle alignment. Specially developed radiosondes will provide vertical profiles of charging and particle sie distribution.
DREAME involves collaboration between Universities of Hertfordshire, Reading, Alexandria, Energy Research Institute in Riyadh, UK Met Office, Public Authority for Applied Education and Training (College of Health Sciences), and Directorate General of Civil Aviation in Kuwait.
Preliminary results show that mineral dust was generally accompanied by electric charging, and the field may in some cases reach sufficiently high values for dust particle alignment to occur.
Eyjafjallajökull volcanic eruption
The aerosol radiosondes developed for DREAME were used to profile volcanic ash concentration and size distribution during the 2010 Eyjafjalla eruption.
Saharan dust in Hertfordshire
Saharan dust intrusions have been detected several times over our remote sensing observatory in Bayfordbury, not far from Hatfield. One such event occurred on the 28 of June 2012. | 0.84464 | 3.464179 |
Advancing Basic Science for Humanity
01/14/2016 - Record-Shattering Cosmic Blast Could Help Crack the Case of Extreme Supernova Explosions
(View the Spanish-language version of this press release)
January 14, 2016
An artist's impression of the record-breakingly powerful, superluminous supernova ASASSN-15lh as it would appear from an exoplanet located about 10,000 light years away in the host galaxy of the supernova. (Credit: Beijing Planetarium / Jin Ma)
Records are made to be broken, as the expression goes, but rarely are records left so thoroughly in the dust. Stunned astronomers have witnessed a cosmic explosion about 200 times more powerful than a typical supernova—events which already rank amongst the mightiest outbursts in the universe—and more than twice as luminous as the previous record-holding supernova.
At its peak intensity, the explosion—called ASASSN-15lh—shone with 570 billion times the luminosity of the Sun. If that statistic does not impress, consider that this luminosity level is approximately 20 times the entire output of the 100 billion stars comprising our Milky Way galaxy.
The record-breaking blast is thought to be an outstanding example of a "superluminous supernova," a recently discovered, supremely rare variety of explosion unleashed by certain stars when they die. Scientists are frankly at a loss, though, regarding what sorts of stars and stellar scenarios might be responsible for these extreme supernovae.
As described in a new study published today in Science, ASASSN-15lh is amongst the closest superluminous supernovae ever beheld, at around 3.8 billion light years away. Given its uncanny brightness and closeness, ASASSN-15lh might offer key clues in unlocking the secrets of this baffling class of celestial detonations.
Two of the 14-centimeter diameter lens telescopes in use for the All Sky Automated Survey for SuperNovae (ASAS-SN) that discovered ASASSN-15lh. Since this photo was taken, two more telescopes have been added to the ASAS-SN station in Cerro Tololo, Chile. (Credit: Wayne Rosing)
"ASASSN-15lh is the most powerful supernova discovered in human history," said study lead author Subo Dong, an astronomer and a Youth Qianren Research Professor at the Kavli Institute for Astronomy and Astrophysics (KIAA) at Peking University. "The explosion's mechanism and power source remain shrouded in mystery because all known theories meet serious challenges in explaining the immense amount of energy ASASSN-15lh has radiated."
ASASSN-15lh was first glimpsed in June 2015 by twin telescopes with 14-centimeter diameter lenses in Cerro Tololo, Chile conducting the All Sky Automated Survey for SuperNovae (ASAS-SN), an international collaboration headquartered at The Ohio State University. (Hence ASASSN-15lh's somewhat menacing moniker.) These two tiny telescopes sweep the skies to detect suddenly appearing objects like ASASSN-15lh that are intrinsically very bright, but are too far away for human observers to notice.
"ASAS-SN is the first astronomical project in history to frequently scan the entire optical sky for optical transients," said Krzysztof Stanek, professor of astronomy at the Ohio State University and the co-Principal Investigator of ASAS-SN. "Every time in science we open up a new discovery space, exciting findings should follow. The trick is not to miss them."
Dong and colleagues immediately put out word about the sighting of ASASSN-15lh in order for as much data as possible to be gathered. Multiple, far larger ground-based telescopes across the globe, as well as NASA's Swift satellite, have since taken part in an intense observing campaign that continues to this day.
In just the first four months after it went kablooie, so much energy beamed out of ASASSN-15lh that it would take our Sun in its current state more than 90 billion years to equal its emissions. By examining this bright, slowly fading afterglow, astronomers have gleaned a few basic clues about the origin of ASASSN-15lh.
Using the 2.5 meter du Pont telescope in Chile, Dong's colleagues Ben Shappee and Nidia Morrell at the Carnegie Observatories in the United States took the first spectrum of ASASSN-15lh to identify the signatures of chemical elements scattered by the explosion. This spectrum puzzled the ASAS-SN team members, for it did not resemble any of spectra from the 200 or so supernovae the project had discovered to date.
Pseudo-color images showing the host galaxy before the explosion of ASASSN-15lh taken by the Dark Energy Camera (DECam) [Left], and the supernova by the Las Cumbres Observatory Global Telescope Network (LCOGT) 1-meter telescope network [Right]. (Credit: The Dark Energy Survey, B. Shappee and the ASAS-SN team)
Inspired by suggestions from Jose Prieto at Universidad Diego Portales and Millennium Institute of Astrophysics in Chile and Stanek, Dong realized that ASASSN-15lh might in fact be a superluminous supernova. Dong found a close spectral match for ASASSN-15lh in a 2010 superluminous supernova, and if they were indeed of a kind, then ASASSN-15lh's distance would be confirmable with additional observations. Nearly 10 days passed as three other telescopes, stymied by bad weather and instrument mishaps, attempted to gather these necessary spectra. Finally, Dong’s colleague Saurabh Jha at Rutgers University was able to use the 10-meter Southern African Large Telescope (SALT) to secure the observations of elemental signatures verifying ASASSN-15lh's distance and extreme potency.
"Upon seeing the spectral signatures from SALT and realizing that we had discovered the most powerful supernova yet, I was too excited to sleep the rest of the night,” said Dong, who had received word of the SALT results at 2 AM in Beijing on July 1, 2015.
The ongoing observations have further revealed that ASASSN-15lh bears certain features consistent with "hydrogen-poor" (Type I) superluminous supernovae, which are one of the two main types of these epic explosions so named for lacking signatures of the chemical element hydrogen in their spectra. ASASSN-15lh has likewise shown a rate of temperature decrease and radius expansion similar to some previously discovered Type I superluminous supernova.
Yet in other ways, besides its brute power, ASASSN-15lh stands apart. It is way hotter, and not just brighter, than its apparently nearest of supernova kin. The galaxy it calls home is also without precedent. Type I superluminous supernova seen to date have all burst forth in dim galaxies both smaller in size and that churn out stars much faster than the Milky Way.
The light curves of ASASSN-15lh and other supernovae for comparison. At maximum, ASASSN-15lh is about 200 times more powerful than a typical Type I supernova, and it is more than twice as luminous as the previous record-holding supernova, named iPTF13ajg. (Credit: the ASAS-SN team)
Noticing the pattern, astronomers hoped this specific sort of galactic environment had something to do with superluminous supernovae, either in the creation of the exotic stars that spawn them or in setting these stars off. Exceptionally, however, ASASSN-15lh's galaxy appears even bigger and brighter than the Milky Way. On the other hand, ASASSN-15lh might in fact reside in an as-yet-unseen, small, faint neighboring galaxy of its presumed, large galactic home.
To clear up where exactly ASASSN-15lh is located, as well as numerous other mysteries regarding it and its hyper-kinetic ilk, the research team has been granted valuable time this year on the Hubble Space Telescope. With Hubble, Dong and colleagues will obtain the most detailed views yet of the aftermath of ASASSN-15lh's stunning explosion. Important insights into the true wellspring of its power should then come to light.
One of the best hypotheses is that superluminous supernovae's stupendous energy comes from highly magnetized, rapidly spinning neutron stars called magnetars, which are the leftover, hyper-compressed cores of massive, exploded stars. But ASASSN-15lh is so potent that this compelling magnetar scenario just falls short of the required energies. Instead, ASASSN-15lh-esque supernovae might be triggered by the demise of incredibly massive stars that go beyond the top tier of masses most astronomers would speculate are even attainable.
"The honest answer is at this point that we do not know what could be the power source for ASASSN-15lh," said Dong. "ASASSN-15lh may lead to new thinking and new observations of the whole class of superluminous supernova, and we look forward to plenty more of both in the years ahead."
1] The preprint of the paper can be accessed at: https://arxiv.org/abs/1507.03010
2] A review article on superluminous supernova by Prof. Avishay Gal-Yam published in Science in 2012 can be found at: https://arxiv.org/abs/1208.3217 | 0.891167 | 3.680846 |
Astronomers have discovered why the upper atmosphere of giant planets such as Saturn and Jupiter are hot, although they are much farther from the Sun than the Earth. The heat source was one of the great mysteries of the solar system, which for a long time remained unsolved. The discovery is reported by Phys.org.
This mechanism helps to solve the problem of why the upper part of the atmosphere is so hot and the rest of the air shell remains cold, as expected due to the remoteness of Saturn from the Sun.
The temperature of the upper layers was measured by observing the refraction of light from bright stars in the constellations Orion and Big Dog at the boundary of Saturn’s atmosphere during the flight of Cassini. This made it possible to know the density of the air envelope, which decreases with height, but the rate of decrease depends on temperature. It turned out that the temperature reaches a maximum near the auroras. | 0.800088 | 3.480084 |
By the end of this section, you will be able to:
- Describe the geological activity during the evolution of the planets, particularly on the terrestrial planets
- Describe the factors that affect differences in elevation on the terrestrial planets
- Explain how the differences in atmosphere on Venus, Earth, and Mars evolved from similar starting points in the early history of the solar system
While we await more discoveries and better understanding of other planetary systems, let us look again at the early history of our own solar system, after the dissipation of our dust disk. The era of giant impacts was probably confined to the first 100 million years of solar system history, ending by about 4.4 billion years ago. Shortly thereafter, the planets cooled and began to assume their present aspects. Up until about 4 billion years ago, they continued to acquire volatile materials, and their surfaces were heavily cratered from the remaining debris that hit them. However, as external influences declined, all the terrestrial planets as well as the moons of the outer planets began to follow their own evolutionary courses. The nature of this evolution depended on each object’s composition, mass, and distance from the Sun.
We have seen a wide range in the level of geological activity on the terrestrial planets and icy moons. Internal sources of such activity (as opposed to pummeling from above) require energy, either in the form of primordial heat left over from the formation of a planet or from the decay of radioactive elements in the interior. The larger the planet or moon, the more likely it is to retain its internal heat and the more slowly it cools—this is the “baked potato effect” mentioned in Other Worlds: An Introduction to the Solar System. Therefore, we are more likely to see evidence of continuing geological activity on the surface of larger (solid) worlds (Figure 1). Jupiter’s moon Io is an interesting exception to this rule; we saw that it has an unusual source of heat from the gravitational flexing of its interior by the tidal pull of Jupiter. Europa is probably also heated by jovian tides. Saturn may be having a similar effect on its moon Enceladus.
The Moon, the smallest of the terrestrial worlds, was internally active until about 3.3 billion years ago, when its major volcanism ceased. Since that time, its mantle has cooled and become solid, and today even internal seismic activity has declined to almost zero. The Moon is a geologically dead world. Although we know much less about Mercury, it seems likely that this planet, too, ceased most volcanic activity about the same time the Moon did.
Mars represents an intermediate case, and it has been much more active than the Moon. The southern hemisphere crust had formed by 4 billion years ago, and the northern hemisphere volcanic plains seem to be contemporary with the lunar maria. However, the Tharsis bulge formed somewhat later, and activity in the large Tharsis volcanoes has apparently continued on and off to the present era.
Earth and Venus are the largest and most active terrestrial planets. Our planet experiences global plate tectonics driven by convection in its mantle. As a result, our surface is continually reworked, and most of Earth’s surface material is less than 200 million years old. Venus has generally similar levels of volcanic activity, but unlike Earth, it has not experienced plate tectonics. Most of its surface appears to be no more than 500 million years old. We did see that the surface of our sister planet is being modified by a kind of “blob tectonics”—where hot material from below puckers and bursts through the surface, leading to coronae, pancake volcanoes, and other such features. A better understanding of the geological differences between Venus and Earth is a high priority for planetary geologists.
The geological evolution of the icy moons and Pluto has been somewhat different from that of the terrestrial planets. Tidal energy sources have been active, and the materials nature has to work with are not the same. On these outer worlds, we see evidence of low-temperature volcanism, with the silicate lava of the inner planets being supplemented by sulfur compounds on Io, and replaced by water and other ices on Pluto and other outer-planet moons.
Let’s look at some specific examples of how planets differ. The mountains on the terrestrial planets owe their origins to different processes. On the Moon and Mercury, the major mountains are ejecta thrown up by the large basin-forming impacts that took place billions of years ago. Most large mountains on Mars are volcanoes, produced by repeated eruptions of lava from the same vents. There are similar (but smaller) volcanoes on Earth and Venus. However, the highest mountains on Earth and Venus are the result of compression and uplift of the surface. On Earth, this crustal compression results from collisions of one continental plate with another.
It is interesting to compare the maximum heights of the volcanoes on Earth, Venus, and Mars (Figure 2). On Venus and Earth, the maximum elevation differences between these mountains and their surroundings are about 10 kilometers. Olympus Mons, in contrast, towers more than 20 kilometers above its surroundings and nearly 30 kilometers above the lowest elevation areas on Mars.
One reason Olympus Mons (Figure 3) is so much higher than its terrestrial counterparts is that the crustal plates on Earth never stop moving long enough to let a really large volcano grow. Instead, the moving plate creates a long row of volcanoes like the Hawaiian Islands. On Mars (and perhaps Venus) the crust remains stationary with respect to the underlying hot spot, and so a single volcano can continue to grow for hundreds of millions of years.
A second difference relates to the strength of gravity on the three planets. The surface gravity on Venus is nearly the same as that on Earth, but on Mars it is only about one third as great. In order for a mountain to survive, its internal strength must be great enough to support its weight against the force of gravity. Volcanic rocks have known strengths, and we can calculate that on Earth, 10 kilometers is about the limit. For instance, when new lava is added to the top of Mauna Loa in Hawaii, the mountain slumps downward under its own weight. The same height limit applies on Venus, where the force of gravity is the same as Earth’s. On Mars, however, with its lesser surface gravity, much greater elevation differences can be supported, which helps explain why Olympus Mons is more than twice as high as the tallest mountains of Venus or Earth.
By the way, the same kind of calculation that determines the limiting height of a mountain can be used to ascertain the largest body that can have an irregular shape. Gravity, if it can, pulls all objects into the most “efficient” shape (where all the outside points are equally distant from the center). All the planets and larger moons are nearly spherical, due to the force of their own gravity pulling them into a sphere. But the smaller the object, the greater the departure from spherical shape that the strength of its rocks can support. For silicate bodies, the limiting diameter is about 400 kilometers; larger objects will always be approximately spherical, while smaller ones can have almost any shape (as we see in photographs of asteroids, such as Figure 4).
The atmospheres of the planets were formed by a combination of gas escaping from their interiors and the impacts of volatile-rich debris from the outer solar system. Each of the terrestrial planets must have originally had similar atmospheres, but Mercury was too small and too hot to retain its gas. The Moon probably never had an atmosphere since the material composing it was depleted in volatile materials.
The predominant volatile gas on the terrestrial planets is now carbon dioxide (CO2), but initially there were probably also hydrogen-containing gases. In this more chemically reduced (hydrogen-dominated) environment, there should have been large amounts of carbon monoxide (CO) and traces of ammonia (NH3) and methane (CH4). Ultraviolet light from the Sun split apart the molecules of reducing gases in the inner solar system, however. Most of the light hydrogen atoms escaped, leaving behind the oxidized (oxygen-dominated) atmospheres we see today on Earth, Venus, and Mars.
The fate of water was different on each of these three planets, depending on its size and distance from the Sun. Early in its history, Mars apparently had a thick atmosphere with abundant liquid water, but it could not retain those conditions. The CO2 necessary for a substantial greenhouse effect was lost, the temperature dropped, and eventually the remaining water froze. On Venus the reverse process took place, with a runaway greenhouse effect leading to the permanent loss of water. Only Earth managed to maintain the delicate balance that permits liquid water to persist on its surface.
With the water gone, Venus and Mars each ended up with an atmosphere of about 96 percent carbon dioxide and a few percent nitrogen. On Earth, the presence first of water and then of life led to a very different kind of atmosphere. The CO2 was removed and deposited in marine sediment. The proliferation of life forms that could photosynthesize eventually led to the release of more oxygen than natural chemical reactions can remove from the atmosphere. As a result, thanks to the life on its surface, Earth finds itself with a great deficiency of CO2, with nitrogen as the most abundant gas, and the only planetary atmosphere that contains free oxygen.
In the outer solar system, Titan is the only moon with a substantial atmosphere. This object must have contained sufficient volatiles—such as ammonia, methane, and nitrogen—to form an atmosphere. Thus, today Titan’s atmosphere consists primarily of nitrogen. Compared with those on the inner planets, temperatures on Titan are too low for either carbon dioxide or water to be in vapor form. With these two common volatiles frozen solid, it is perhaps not too surprising that nitrogen has ended up as the primary atmospheric constituent.
We see that nature, starting with one set of chemical constituents, can fashion a wide range of final atmospheres appropriate to the conditions and history of each world. The atmosphere we have on Earth is the result of many eons of evolution and adaptation. And, as we saw, it can be changed by the actions of the life forms that inhabit the planet.
One of the motivations for exploration of our planetary system is the search for life, beginning with a survey for potentially habitable environments. Mercury, Venus, and the Moon are not suitable; neither are most of the moons in the outer solar system. The giant planets, which do not have solid surfaces, also fail the test for habitability.
So far, the search for habitable environments has focused on the presence of liquid water. Earth and Europa both have large oceans, although Europa’s ocean is covered with a thick crust of ice. Mars has a long history of liquid water on its surface, although the surface today is mostly dry and cold. However, there is strong evidence for subsurface water on Mars, and even today water flows briefly on the surface under the right conditions. Enceladus may have the most accessible liquid water, which is squirting into space by means of the geysers observed with our Cassini spacecraft. Titan is in many ways the most interesting world we have explored. It is far too cold for liquid water, but with its thick atmosphere and hydrocarbon lakes, it may be the best place to search for “life as we don’t know it.”
We now come to the end of our study of the planetary system. Although we have learned a great deal about the other planets during the past few decades of spacecraft exploration, much remains unknown. Discoveries in recent years of geological activity on Titan and Enceladus were unexpected, as was the complex surface of Pluto revealed by New Horizons. The study of exoplanetary systems provides a new perspective, teaching us that there is much more variety among planetary systems than scientists had imagined a few decades ago. The exploration of the solar system is one of the greatest human adventures, and, in many ways, it has just begun.
Key concepts and summary
After their common beginning, each of the planets evolved on its own path. Different possible outcomes are illustrated by comparison of the terrestrial planets (Earth, Venus, Mars, Mercury, and the Moon). All are rocky, differentiated objects. The level of geological activity is proportional to mass: greatest for Earth and Venus, less for Mars, and absent for the Moon and Mercury. However, tides from another nearby world can also generate heat to drive geological activity, as shown by Io, Europa, and Enceladus. Pluto is also active, to the surprise of planetary scientists. On the surfaces of solid worlds, mountains can result from impacts, volcanism, or uplift. Whatever their origin, higher mountains can be supported on smaller planets that have less surface gravity. The atmospheres of the terrestrial planets may have acquired volatile materials from comet impacts. The Moon and Mercury lost their atmospheres; most volatiles on Mars are frozen due to its greater distance from the Sun and its thinner atmosphere; and Venus retained CO2 but lost H2O when it developed a massive greenhouse effect. Only Earth still has liquid water on its surface and hence can support life. | 0.882241 | 4.029754 |
Van Allen radiation belts are zones of high-energy particles (especially protons) trapped by earth’s magnetic field. Most of these high-energy particles originate from the solar wind, that were captured by and held around a planet by that earth’s magnetic field. The van Allen belt is formed like a torus above the equator. There are two van Allen radiation belts, an internal belt is centered at about 3,000 kilometers and an outer belt is centered at about 22,000 kilometers from the earth’s surface. It contains mainly energetic protons in the 10-100 MeV range.
Spacecraft travelling beyond low Earth orbit enter the zone of radiation of the Van Allen belts. Beyond the belts, they face additional hazards from cosmic rays and solar particle events. A region between the inner and outer Van Allen belts lies at two to four Earth radii and is sometimes referred to as the “safe zone”. | 0.825876 | 3.104825 |
Given the impact that such a mission would have had on the public, everyone knows that there have never been astronauts or cosmonauts near Venus. Nevertheless, several projects have been established but have never gone very far.
Apollo application program
The first project is probably one of the most serious was born in the mid-1960s in the middle of the Apollo program. It is part of the Apollo application program (AAP) missions that sought to reuse elements of the lunar program for other purposes. The three astronauts should have spent more than a year in interplanetary space for only a few hours of flyby. The mission was reportedly launched by a modified Saturn V that launched an Appolo command and service ship (CSM). The third floor (SIVB) would not have been dropped, but was added solar panels and communication antennas. After use, its hydrogen tank would have been emptied and then filled with air to make it a living module. This concept of using a reservoir as habitat is called wet workshop. The lunar exploration module would have been replaced by a compartment attached to the SIVB that would have included the equipment needed to develop the hydrogen tank. In some respects, the CSM would have had its only AJ10 engine replaced by two shorter engines in order to free up space and have redundancy. In addition to its cockpit role during launch and return to Earth, the CSM could have been used for trajectory corrections. These engines were also to be used to brake at the end of the mission for the ground return to be done at an acceptable speed.
This program should have been divided into three phases. Phase A was formed solely by putting into orbit, a CSM and a modified SVIB to test the feasibility of a development of the latter. Phase B consists of a long-duration mission in high orbit over the Van Allen belt, which is therefore more exposed to radiation. This would have made it possible to simulate an interplanetary flight at best but with a fast return capability. Phase C was the Venusian flyby mission itself. The redeveloped saturn V should have taken off in October 31, 1973 for a flyby of Venus 5 months later and return to Earth at the end of 1974. But while none of these 3 missions were launched, the SIVB planning studies were used to build Skylab.
The Soviet equivalent of the AAP project is the TMK project (for heavy interplanetary spacecraft in Russian). It was a series of interplanetary missions launched by a giant N1 rocket. One version of these missions was the MAVR for MArs-VeneRa because it was to consist of a two-year flight during which the spacecraft was to fly over Mars and Venus. The 75-t spacecraft was to be launched in one go by an N1 rocket with a hydrogen upper stage. The spacecraft included solar panels, communication antennas, probes to drop on different planets and a capsule that, once dropped, would allow the return of the three cosmonauts to Earth. Of course, since the N1 rocket never worked, the TMK project never saw the light of day.
In 2015, a NASA team conducted a manned mission architecture study on Venus called the Venus High Altitude Operational Concept (HAVOC). The program would have been divided into three phases. The first is fully automatic with a 30m long Venusian airship that would test the technologies of future stages and carry many scientific instruments. The second phase is to send astronauts into orbit around Venus without entering the atmosphere. The final phase is to allow two astronauts to explore venus’ atmosphere in a 130 m airship for a month during a one-year, 3-month mission.
The mission requires the launch into low Earth orbit of two elements as well as propulsion stages to launch it towards Venus. The first is an interplanetary habitat that houses astronauts during the 110-day outbound journey and then 300 days of return and would remain in orbit around Venus during the 30 days of exploration. The second element includes the folded airship and would be launched before habitat. Once the two elements were in orbit around Venus, they would dock to allow astronauts to pass from the habitat to the airship. The latter, now inhabited, plunges into the atmosphere and unfolds during the fall. At the end of the 30 days of atmospheric exploration, the astronauts enter the launcher attached under the airship to regain the habitat element that would bring them back to Earth.
Each mission requires 2 SLS super-lourd launchers, 8 heavy commercial launchers and 2 manned launchers to bring and bring astronauts back between Earth and habitat in low Earth orbit. Taking into account this profusion of launchers, the exorbitant development costs of the various elements and the lack of scientific benefits, this mission is economically unrealistic. The Havoc project must therefore be taken for what it is, a feasibility study and a reminder of the possibilities of alternative inhabited exploration to Mars.
The images presented here are from the attached HAVOC project report. | 0.83014 | 3.066677 |
To quote the late sci-fi author Douglas Adams, “Space is big, really big. You just wouldn’t believe how hugely, vastly, mindbogglingly big space is. You might think it’s a long way down the road to the chemist but that’s just peanuts to space.” It takes a really long time to traverse the vast distance of even interplanetary space from Earth to Mars. The recently deceased comet ISON spent the better part of a year travelling between Jupiter to the Sun before its demise in the Sun’s inferno. Jupiter is roughly 778,000 kilometers from the Sun and Saturn is nearly twice that far away at 1.4 billion kilometers away. Twice the distance from the Sun to Saturn is Uranus sitting a whopping 2.8 billion kilometers from the Sun. Even further still is icy Neptune, so far away it’s existence was predicted before it was directly observed sits an incredible 4.8 billion kilometers from the Sun. At this point in the solar system the Sun is nothing more than a small point of light almost appearing as just another background star in the Milky Way. But the orbit of Neptune is just the seashore of the cosmic ocean that is our solar system. Far beyond the orbit of Neptune lies a huge area known as the Kuiper Belt which is home to an unknown number of tiny icy worlds. The most well-known of the Kuiper Belt objects (KBO) is the dwarf planet Pluto. Until 2006 Pluto was recognized as the ninth planet in the solar system but was downgraded to dwarf planet when astronomers began discovering objects in its neighborhood that were both larger and smaller. Pluto lies a mindbogglingly 5.8 billion kilometers from the Sun. Together with its large moon Charon, Pluto marks the beginning of unexplored territory in our solar system. No human spacecraft has ever visited Pluto. Much of Pluto’s characteristics are unknown to us. The same goes for all of the KBO’s in Pluto’s neighborhood.
NASA is on the verge of changing that. The New Horizons spacecraft which was launched in January 2006 is just a year away from the beginning of its mission at Pluto. New Horizons is travelling at about 1 million miles per day as it speeds into uncharted waters so to speak. Currently approaching the orbit of Neptune, New Horizons is approximately 4 billion kilometers from the Sun. The probe will arrive at its closest approach of Pluto on July 14, 2015 but the science will begin well before that in January 2015. New Horizons is equipped with many instruments to help scientists analyze Pluto. One such instrument is the Long Range Reconnaissance Imager (LORRI) which is essentially a long focal length telescope with a CCD imager to take high resolution images of the Plutonian surface beginning in January 2015.
An Historic Mission
Pluto is part of a vast unexplored trans-Neptune region of the solar system called the Kuiper Belt. The inhabitants of the Kuiper Belt are thought to be the leftovers of planetary formation when rocky and icy bodies were being flung around the solar system. These icy worlds didn’t quite form into full-fledged planets but they are worlds nonetheless. Only five human spacecraft have ever traveled in this cold void before. New Horizons is the first spacecraft to be sent to directly study a new body since the Voyager probes thirty years ago. For my generation (milllennials) this is akin to the Apollo 11 moon landing in its scientific value. I can’t think of any mission that is more important to the understanding of our solar system than New Horizons.
New Horizons will provide scientists with a smorgasbord of priceless data about Pluto and the KBO’s nearby. Besides LORRI New Horizons is equipped with an ultraviolet spectrometer (ALICE) which will be used to analyze Pluto’s atmosphere, an optical/infrared instrument (RALPH) that will be used to create maps of the surfaces of Pluto and Charon, a particle detection instrument (PEPSSI) used to detect molecules escaping from the atmosphere, a particle instrument (SWAP) to measure the solar wind at Pluto, a radio instrument (REX) to observe the atmosphere and a student created instrument to collect dust particles that have traveled from the inner solar system. The only thing we know about the surface of Pluto is from Hubble which provide a low resolution map that can only resolve surface features that are hundreds of kilometers in size.
One of the more interesting observations New Horizons will make is the study of Pluto’s atmosphere. Pluto’s orbit is highly inclined to the ecliptic, the plane all the planets orbit in, and is highly eccentric (oval shaped). This means that Pluto’s distance from the Sun varies greatly depending on where it is in its orbit. The vast distance change is thought to cause molecules in Pluto’s atmosphere to condensate and sublimate and be lost to space. The ALICE, PEPSSI, and REX instruments on New Horizons will measure the constitution of Pluto’s atmosphere and the rate at which it is being lost to space.
Once New Horizons has completed its mission objectives for Pluto and Charon it will move on to studying some nearby KBO’s if any are in the vicinity. So little is known about the Kuiper Belt and its citizens so any information on these icy worlds is practically invaluable. The mission is slated to end in 2026 but if the spacecraft is still operational NASA has targeted the edge of the solar system just like with the Voyagers 1 and 2 missions. Hopefully New Horizons will be able to reach the heliopause (the region where the solar wind from the Sun begins to interact with interstellar particles) and map this boundary point. With the data from Voyager still inconclusive it is necessary to continue to explore this strange region of space. The spacecraft is predicted to be inoperable by 2038 signally the end of its lifetime. By then New Horizons will have contributed a massive volume of science and radically changed the way we view our solar system’s outer reaches. Who knows what we’ll see when it finally reached Pluto next July? Besides the data New Horizons provides, the probe is fulfilling our human curiosity and our desire to explore. Space is the last frontier and there sure is a lot out there!
Big news came from the Hubble Space Telescope today. Observations from the famous telescope made in ultraviolet light show a large plume of hydrogen and oxygen spewing from, Jupiter’s moon, Europa’s south polar region. Europa is one of Jupiter’s four largest moons, known as the Galilean Moons, after their discoverer Galileo Galilei in the 17th century. The plume is guessed to be water gushing from cracks in the ice that covers the entire surface of Europa. This is the first observation of geysers on Europa although it has been suspected for some time now.
Europa is roughly the same size our our moon and is covered with ice. This has been known for centuries since Galileo discovered the moon in 1610. Europa is easily visible in binoculars and small telescopes and is extremely bright. It was correctly guessed that Europa was covered in a layer of ice because it reflects a very high amount of sunlight. Ice is one of the most reflective materials, about 70% of sunlight is reflected back off the surface. The spacecraft we have sent to Jupiter such as Voyagers 1 and 2 and the Galileo probe confirmed the existence of an icy surface.
The surface of Europa is interesting because it doesn’t contain any craters or any marks of impacts like the vast majority of moons in the solar system. That means that Europa is constantly re-making its surface. The same way glaciers and tectonic plates reform the surface of Earth, giant cracks along the surface of Europa indicate that the surface is geologically active. Where there is surface tectonics there should be geological events such as volcanoes or geysers. That’s what Hubble confirmed today.
The observations from Hubble showed a massive plume of water gushing from the moon’s south polar region. The plume extends approximately 200 km (125 miles) into space. Europa has no atmosphere and much less gravity than Earth so the vapor is able to spew well beyond the surface of Europa. The water from the geyser was blasted from beneath the icy surface at a whopping 700 kilometers per hour (1,500 mph). That’s three times faster than a commercial jet! Two questions remain to be answered: How do we know the geyser is shooting out water and where does that water come from?
A Veritable Waterworld
The existence of water on Europa has actually been known for a long time. To know how this works we have to know a little bit about Europa’s orbital properties. Europa orbits Jupiter, the solar system’s largest planet. Jupiter’s gravity is so intense that it actually effects the insides of its closest moons. Europa’s orbit is slightly elliptical, meaning that it isn’t a perfect circle, an ellipse or oval-shaped orbit. Most celestial bodies have slightly elliptical orbits but Europa’s is more pronounced. When Europa is closer to Jupiter the massive gravity of the planet literally squeezes the moon and stretches the rocky core. This pressure and friction creates heat under the icy surface and has created a subsurface ocean on Europa. It is guessed that Europa actually contains more water than Earth as Europa’s ocean is global, there are no landmasses. NASA and the European Space Agency hope to eventually send a probe to Europa to explore this massive subsurface ocean because where water exists the possibility of life also exists.
The Giant Plume
We’ve answered where the water comes from, but how are scientists sure it is indeed water that was spewed from the surface and how does such a tiny moon have geysers that powerful? Hubble doesn’t just do visible light observations. The telescope is also equipped with a camera that can image in ultraviolet light. The actual images taken by Hubble don’t show what we think of as a geyser like Old Faithful in Yellowstone National Park. What Hubble observed was actually individual hydrogen and oxygen atoms in the plume. Since Europa has no atmosphere the hydrogen and oxygen atoms were in space. Jupiter, like Earth, generates an magnetic field in its solid metal core. When the water from the geyser interacts with the electrons from Jupiter the water separates into its constituent hydrogen and oxygen atoms which glow in ultraviolet light. That’s the best possible explanation for why Hubble observed these two individual atoms.
But where did the geyser come from? Well as we saw earlier about Europa’s elliptical orbit, the moon is closer at some points and further away at others. As Europa moves closer to Jupiter it is squeezed and crunched by Jupiter’s immense gravity. Then as Europa moves further away from Jupiter cracks in the ice open up and allow the subsurface water to rise up and spew out. As it so happens, Hubble recorded these observations while Europa was moving away from Jupiter so it makes sense that the cracks in the icy surface were opened up.
Teeming With Life?
The prospect of life swimming in Europa’s ocean has long been intriguing. The discovery of geysers on Europa make the question even more worth exploring. As we see from geysers on Earth, a lot of power in needed to blast material out from under the surface. On Earth this comes from heat and pressure that builds up beneath cracks in the Earth’s crust. When the heat and pressure becomes too great water and gases burst forth in a steaming awesome display of geological activity.
One of the theories of how life began involves water and heat in the prehistoric oceans of Earth. Hydrothermal vents on the ocean floor mix heat and amino acids to create the first organic materials. To this day life thrives around hydrothermal vents despite the extremely alien conditions. We know there is heat in Europa’s oceans due to the gravitational heating of the core from Jupiter and there’s water which is a universal solvent. Could the mixing of amino acids, water, and heat have occurred on Europa as well? The prospect is certainly intriguing and worthy of further exploration. Curiosity is one of humanity’s definite traits so hopefully in a decade or two we will have a spacecraft on its way to Europa to explore the subsurface ocean and attempt to find evidence of life. Imagine fish (or something totally alien) swimming around on the moon of a distant planet! How that would change our views of life and its frequency throughout our galaxy!
Unless you’ve lived under a rock for the last 20 years (or on another planet) you’ve seen a plethora of beautiful images from the Hubble Space Telescope. Many of Hubble’s images are some of the most iconic and awe-inspiring pictures of all time. Since 1990, Hubble has been constantly observing the visible universe collecting scientific data for astronomers that has been used to determine the origin of our universe and further explore the vastness of the cosmos. Hubble’s archive, however, is massive and many thousands of images have never been seen by anyone, save only a few scientists. For a while now the scientists at the European Space Agency have been processing the data from the Hubble vault and producing mind-blowingly beautiful pictures of the data and releasing them as the Hubble Picture of the Week. But the vault is just too large and there are thousands of hidden treasures still inside Hubble’s vault waiting to be unearthed.
The folks over at Spacetelescope.org have created a contest called Hubble’s Hidden Treasures to help plumb the depths of riches of the archive of the world’s most well known telescope. Between now and May 31st you can access the Hubble Legacy Archive website to search for images that Hubble has captured. The browser-based image processing tools allow you to then adjust the basic properties of the image such as contrast, zoom, color balance, and more to turn the image into a spectacular photograph. Prizes will be given away for the top images once the contest is over.
For those who own professional-grade image processing software there’s a contest for you too! You can enter Hubble’s Hidden Treasures 2012 Image Processing Contest. It works the same way as the normal contest but you can download the data from the Hubble Legacy Archive to your computer and use your favorite image processing software to create truly stunning photos. For more information on both of these contests go to www.spacetelescope.org and happy imagulating!
The Hubble Space Telescope really is an amazing piece of machinery! We are approaching the 22nd anniversary of Hubble next month so I believe a little tribute is in order. For the last 22 years Hubble has been constantly blowing our minds with stunning images of our solar system, our galaxy, and the universe. Named after the great 20th century astronomer Edwin Hubble, the HST was charged with unlocking the mystery of Edwin Hubble’s greatest project: the expansion of the universe. The observatory has since succeeded with remarkably accurate precision.
Without a doubt, Hubble is the great triumph of the Shuttle era. From its infamously defective mirror correction mission and several repair and upgrade missions over the years, all made possible by the Space Shuttle; Hubble has proven to be tougher and more effective than anyone could have imagined in 1990 when it was launched. With Hubble we have peered into the furthest visible depths of the universe and seen what we could have previously only imagined. We owe so much of our knowledge of the universe to the images and data Hubble has sent back to us. We’ve more accurately determined the rate of expansion of the universe, estimated the age of the universe, discovered ancient supernovae, and discovering that galaxies may have black holes at their centers. Some of the most stunning images of our universe have come from Hubble. The HST is known for its incredibly sharp visible light images.
The most recent image to be released by Hubble is one of Messier 9, a globular cluster about 5,500 light years from the galactic center in the constellation Ophiuchus. The recently captured image is the most detailed ever taken of M9. The photo shows a myriad of differently colored stars, which number in the thousands. One can clearly observe several different types of stars in the cluster. The hotter bluish stars crowd the center of the cluster while the cooler red/orange stars are scattered mostly around the edges. M9 has a total luminosity of roughly 120,000 times that of our Sun while only occupying the space of a pin point at arm’s length in the sky. At 25,800 light years from Earth M9 is one of the closer globular clusters to Earth. Globulars are interesting to astronomers because they contain some of the oldest stars in the galaxy and are a remnant of the galaxy’s infancy and formation.
There are countless other images sent back from Hubble and I’m sure you’ve seen many of them. Needless to say, Hubble surely ranks up near the top of NASA’s greatest hits. The telescope is expected to remain in orbit and functional until at least 2014. Hubble’s successor, the James Webb Space Telescope is expected to be launched by 2018 but delays and budget concerns have plagued the project for several years now. Whenever Hubble de-orbits it will surely be remembered as one of mankind’s greatest scientific instruments. Long live Hubble! | 0.87742 | 3.460645 |
Perhaps the most impressive thing about LightSail is that it was funded almost entirely by citizen donations to The Planetary Society, a non-profit space advocacy organisation co-founded by the late astronomer Carl Sagan and currently headed by Bill Nye, the Science Guy.
“After six years of development, we're ready at last to see how LightSail flies,” said Nye in a press release.
“LightSail is technically wonderful, but it's also wonderfully romantic," he said. "We'll sail on sunbeams.”
The planned launch is an important first step toward demonstrating solar sailing technology, which some people say is humanity’s best bet to achieve interstellar space travel (even if it might take a sail the size of Texas or the help of some fancy, super accurate lasers to get beyond our Solar System).
The LightSail spacecraft won’t be up for any Matthew McConaughey-style interstellar missions just yet. In fact, this first flight won’t even take it beyond Earth’s orbit, or the limitations posed by atmospheric drag. Nevertheless, it’s still pretty impressive.
The LightSail consists of three 10cm by 10cm cubesats stacked together, and is about the size of a standard loaf of bread. Folded inside its external casing are four triangular sails. These reflective sails will unfurl along 4-metre-long retractable booms, creating a large 32-square metre reflective surface that will catch the Sun's energy and momentum-carrying photons - much like fabric sails on a boat catch wind.
The sails have been made of Mylar, which is a type of aluminium-coated plastic film developed by chemical engineering company DuPont in the 1950s. It traps and reflects heat, and has been widely used by NASA - and other space agencies - to protect and insulate spacecraft. It’s also the stuff used to make emergency blankets. The Mylar sheets employed on LightSail are about one-quarter the thickness of a plastic garbage bag.
The Planetary Society’s new LightSail website explains the theory behind solar sailing:
"Light is made of packets of energy called photons. While photons have no mass, a photon traveling as a packet of light has energy and momentum. Solar sail spacecraft capture light momentum with large, lightweight mirrored surfaces—sails. As light reflects off a sail, most of its momentum is transferred, pushing on the sail. The resulting acceleration is small, but continuous. Unlike chemical rockets that provide short bursts of thrust, solar sails thrust continuously and can reach higher speeds over time."
When the sails are deployed (likely sometime in June, depending on the launch date), the craft will become visible from Earth.
And while this test flight won’t demonstrate true solar sailing, it will pave the way for a second test in 2016.
This second flight will be on a SpaceX Falcon Heavy rocket, and will reach an altitude where solar radiation can be used to maneuver the craft.
In 2005, the Planetary Society attempted to launch its first solar sail spacecraft, known as the Cosmos 1. However, 83 seconds into the launch, a rocket failure ended the mission.
As IEEE’s Spectrum reports, since that failed attempt, “other spacecraft have used radiation pressure to adjust their orbits," and there have been successful solar sail missions.
In 2010, Japan’s space agency, JAXA, launched a solar sail-powered craft called IKAROS on a mission past Venus, which was eventually meant to travel around the Sun. This bold demonstration was followed by NASA successfully deploying NanoSail-D in low-Earth orbit in 2011. | 0.869931 | 3.555355 |
For six years, the Japan Aerospace Exploration Agency's Hayabusa2 spacecraft has been in space, on a mission to explore the near-Earth asteroid Ryugu.
The spacecraft was launched in 2014, and in 2018, it reached its target: the asteroid Ryugu (our earlier article here).
Now, Hayabusa2 is returning home, after accomplishing many space “firsts" including the release of a lander on an asteroid and the collection of surface and below-surface material for analysis!
The Mission to Meet Ryugu
The goal of the mission was to analyze the asteroid to learn more about the intricacies of space.
Asteroids are small, jagged rocks that orbit the Sun, like planets. Asteroid Ryugu is shaped like a top and is about 3,000 feet wide, with many large (but light) boulders.
The Japanese lander MASCOT took pictures of Ryugu, discovering that it was composed of equal amounts of dark, rough rocks and bright, smooth ones. This suggests that it was formed from the leftover rubble of a collision. The rocks were also very carbon-rich, similar to carbonaceous chondrites (a type of meteorite), and help explain Ryugu’s dark color.
The lack of a dust layer on Ryugu has puzzled scientists. They speculate that either solar radiation is charging and pulling dust particles away, or that collision with space objects or the movement of the asteroid is stripping dust from the surface.
A Scientific Explosion!
The Hayabusa2 also carried a Small Carry-on Impactor with explosives to blast a crater onto Ryugu to study how craters form.
The explosion created a 33-foot-wide, semi-circle shaped crater and sent up a plume of material. The material’s loose, sand-like properties suggest that the asteroid is only 9 million years old, a youngling in the space world. The plume also never fully left the surface, probably due to the asteroid’s gravitational pull.
A heat map of Ryugu shows that it absorbs and releases heat very quickly -- this indicates that the asteroid is porous with more than 50% holes. This is very different from meteorites found on Earth. It is possible that these porous and carbon-rich meteorites rarely crash into Earth and burn up in the atmosphere instead.
When Hayabusa2 finally returns to Earth, scientists can learn even more from the samples of Ryugu’s surface and interior, helping us uncover more about our mysterious galaxy.
Sources: Nature, New Scientist, Phys.org, CNN, Science News | 0.830561 | 3.939406 |
From: Jet Propulsion Laboratory
Posted: Thursday, March 4, 2010
New studies of ripples and dunes shaped by the winds on Mars testify to variability on that planet, identifying at least one place where ripples are actively migrating and another where the ripples have been stationary for 100,000 years or more.
Patterns of dunes and the smaller ripples present some of the more visually striking landforms photographed by cameras orbiting Mars. Investigations of whether they are moving go back more than a decade.
Two reports presented at the 41st Lunar and Planetary Sciences Conference near Houston this week make it clear that the answer depends on where you look. Both reports used images from the High Resolution Imaging Science Experiment (HiRISE) camera on NASA's Mars Reconnaissance Orbiter, which allows examination of features as small as about a meter, or yard, across.
One report is by Simone Silvestro of the International Research School of Planetary Sciences at Italy's G. d'Annunzio University, and his collaborators. They investigated migration of ripples and other features on dark dunes within the Nili Patera area of Mars' northern hemisphere. They compared an image taken on Oct. 13, 2007, with another of the same dunes taken on June 30, 2007. Most of the dunes in the study area are hundreds of meters long. Ripples form patterns on the surfaces of the dunes, with crests of roughly parallel ripples spaced a few meters apart.
Careful comparison of the images revealed places where ripples on the surface of the dunes had migrated about 2 meters (7 feet) -- the largest movement ever measured in a ripple or dune on Mars. The researchers also saw changes in the shape of dune edges and in streaks on the downwind faces of dunes.
"The dark dunes in this part of Mars are active in present-day atmospheric conditions," Silvestro said. "It is exciting to have such high-resolution images available for comparisons that show Mars as an active world."
The other report is by Matthew Golombek of NASA's Jet Propulsion Laboratory, Pasadena, Calif., and collaborators. They checked whether ripples have been moving in the southern-hemisphere area of Mars' Meridiani Planum where the Mars Exploration Rover Opportunity has been working since 2004. They used observations by Opportunity as well as by HiRISE, surveying an area of about 23 square kilometers (9 square miles). Examination of ripples at the edges of craters can show whether the ripples were in place before the crater was excavated or moved after the crater formed.
"HiRISE images are so good, you can tell if a crater is younger than the ripple migration," Golombek said. "There's enough of a range of crater ages that we can bracket the age of the most recent migration of the ripples in this area to more than 100,000 years and probably less than 300,000 years ago."
Winds are still blowing sand and dust at Meridiani. Opportunity has seen resulting changes in its own wheel tracks revisited several months after the tracks were first cut.
Golombek has a hypothesis for why the ripples at Meridiani are static, despite winds, while those elsewhere on Mars may be actively moving. Opportunity has seen that the long ripples in the region are covered with erosion-resistant pebbles, nicknamed "blueberries," which the rover first observed weathering out of softer matrix rocks beside the landing site. These spherules -- mostly about 1 to 3 millimeters (0.04 to 0.12 inches) in diameter -- may be too large for the wind to budge.
"The blueberries appear to form a armoring layer that shields the smaller sand grains beneath them from the wind," he said.
HiRISE Principal Investigator Alfred McEwen, of the University of Arizona, Tucson, said, "The more we look at Mars at the level of detail we can now see, the more we appreciate how much the planet differs from one place to another."
The Mars Reconnaissance Orbiter and the Mars Exploration Rover missions are managed by JPL for NASA's Science Mission Directorate in Washington. Lockheed Martin Space Systems in Denver was the prime contractor for the orbiter and supports its operations. The University of Arizona operates the HiRISE camera, which was built by Ball Aerospace & Technologies Corp., Boulder, Colo.
// end // | 0.839157 | 3.831121 |
As early as 700 million years after the Big Bang, galaxies were already filled with cosmic dust. But where did it come from? There are two known sources of dust: old stars and supernovae. Astronomers studied nearby supernovae SN 2003gd using the Spitzer space telescope, and found that it had produced tremendous amounts of dust. Since there were many supernovae in the early Universe, they could be the source of all this dust.
When the universe was only 700 million years old, some of its galaxies were already filled with lots of dust. But where did all of this dust come from? Astronomers using NASA’s Spitzer Space Telescope think they may have found the source in type II supernovae, the violent explosions of the universe’s most massive stars.
Cosmic dust is an important component of galaxies, stars, planets, and even life. Until recently, astronomers knew of only two places where dust formed: in the outflows of old sun-like stars that are billions of years old, and in space through the slow condensation of molecules. The problem with these two scenarios is that neither explains how the universe got so dusty only a few hundred million years after its birth. Astronomers have theorized that the missing dust might be produced in supernova explosions, but evidence for this has been hard to find.
Using the space-based Spitzer and Hubble Space Telescopes and the ground-based Gemini North Telescope atop Mauna Kea in Hawaii, Dr. Ben Sugerman of the Space Telescope Science Institute in Baltimore, Md. and his colleagues found a significant amount of heated dust in the remains of a massive star called supernova SN 2003gd. The supernova remnant is located approximately 30 million light-years away in the spiral galaxy M74.
Stars like the progenitor of supernova SN 2003gd have relatively short lives of just tens of millions of years. Since Sugerman’s work shows supernovae produce copious amounts of dust, he believes the explosions could account for much of the dust in the early universe. His findings will be published in the June 8 issue of Science Express.
“This discovery is interesting because it is finally showing that supernovae are significant contributors to dust formation, when evidence up to now has been inconclusive,” said Sugerman.
Because supernovae fade fairly quickly, scientists need very sensitive telescopes to study them even a few months after the initial explosions. Scientists have suspected that most supernovae do produce dust, but their ability to study this dust production in the past has been limited by technology.
“People have suspected for 40 years that supernovae could be producers of dust, but the technology to confirm this has only recently become available,” said Sugerman. “The advantage of using Spitzer is that we can actually see the warm dust as it forms.”
“Dust particles in space are the building blocks of comets, planets, and life, yet our knowledge of where this dust was made is still incomplete. These new observations show that supernovae can make a major contribution to enriching the dust content of the universe,” said Dr. Michael Barlow of University College London in the United Kingdom.
This research is part of a collaboration called the Survey for Evolution of Emission from Dust in Supernovae (SEEDS), which is led by Barlow.
Original Source: Spitzer Space Telescope | 0.877712 | 4.089303 |
Let 2 represent the height above the midplane. Dotting the last equation with the unit vector z and transposing yields
Phi dz dz where PHI and pHI are, respectively, the pressure and mass density of the atomic gas. These two quantities are related by
Here the quantity cHI, which has the dimensions of velocity, represents the random internal motion of the medium. It is also the speed of sound, assuming the medium keeps a fixed temperature during passage of the waves. For an ideal gas, cHI is given in terms of the temperature and mean molecular weight by (RT/^)1/2, with R being the gas constant. If we assume that cHI does not vary with z, then substitution of equation (2.6) into (2.5) and a single integration yields the relation between p and :
* * Figure 2.6 Motion of HI gas in the Galaxy. * * Discrete clouds move away from the Galactic * midplane at z = 0, reaching an average dis* tance hm above and below it. This distance is * less than ht, the scale height for low-mass stars.
To make further progress, we need to specify the gravitational potential. This quantity is related to p*, the total mass density in the Galaxy, through Poisson's equation:
In a thin disk, we may safely ignore horizontal gradients and write (2.8) as
Most of the Galactic matter consists of low-mass stars, which have a scale height h* greater than that of the neutral gas (Figure 2.6). Hence, we may safely replace p*(z) in equation (2.9) by its midplane value p* (0). We then integrate this equation twice, noting that the gravitational force at the midplane, which is —d$g/dz, must vanish by symmetry. The resulting potential is given by
Equations (2.7) and (2.10) together imply that the cold neutral medium has a Gaussian distribution. The corresponding scale height is h-Hi =
Was this article helpful? | 0.803454 | 3.787416 |
Mt. Teide Observatory
The study of astronomy has always been closely associated iwith Mt. Teide. Its advantages as an observation post were well known by naturalists and astronomers centuries ago. Piazzi Smyth set up an observation post at 3,300 metres in the mid 19th century, taking advantage of the unbeatable potential of the skies of Las Cañadas. Lunar features were named Teide and Tenerife as a tribute to his work.
This astronomic tradition was continued in the early 20th century, with studies made of Halley´s Comet by French astronomer Jean Mascart in 1910 in Alto de Guajara, at an altitude of 2,718 metres. The importance of Las Cañadas as an outstanding platform for astronomic studies is reflected by the fact that the Mt. Teide Astrophysics Observatory was built at Izaña, where there has also been a weather station since 1916. The Mt. Teide Observatory – together with the Roque de los Muchachos Observatory, on the island of La Palma – belong to the CANARY ISLAND ASTROPHYSICS INSTITUTE (IAC, from its initials in Spanish), which has its head offices in La Laguna.
Modern Astrophysics took its first steps in the Canary Islands in this Observatory, in the early sixties, in the area of Izaña, at an altitude of 2,400 m, where the municipal boundaries of La Orotava, Fasnia and Güimar converge. The first telescope started to operate in 1964, to study zodiacal light, the light scattered by inter-planetary matter.
Area: 50 hectares
Altitude: 2.400 metres
Latitude: 28º18´00″ North
There are currently telescopes and other astronomic instruments from over 60 institutions of 19 different countries installed in the Mt. Teide Observatory (Island of Tenerife) and the Roque de Los Muchachos Observatory (Island of La Palma). These observation facilities, plus the scientific and technical facilities available in the IAC´s Astrophysics Institute in La Laguna (Tenerife) and in the IAC´s La Palm Common Astrophysics Centre in Breña Baja (La Palma), make up the European Northern Observatory (ENO).
Their geographic location, between the solar observatories of the east and the west, together with the transparency and excellent astronomic quality of the skies, have meant that the Mt. Teide Observatory gives priority to studying the Sun, concentrating the best European solar telescopes at these sites.
Solar Vacuum Tower Telescope (VTT), 70 cm.
THEMIS solar telescope, 90 cm.
GREGOR solar telescope, 1.5 m.
Spectrophotometers (MARK-I, IRIS-T, ECHO)
High resolution photometer TON
Fourier tachometer GONG
„Carlos Sanchez” infra-red telescope (TCS), 155 cm.
Mons reflector telescope, 50 cm.
IAC-80 telescope, 80 cm.
OGS telescope, 100 cm. (Optical Ground Station)
STARE telescope, 10 cm.
Bradford robot telescope
STELLA robot telescopes
COSMIC MICROWAVE BACKGROUND
COSMO10 and 15
VSA (Very Small Array) interferometer network
Vacuum Tower Solar Telescope VTT
The Vacuum Tower Telescope belongs to the Kiepenheuer Institute of Solar Physics of Frieburg (Germany). It has a primary mirror with a diameter of 70 cm and a 15 metre long vertical spectrograph. It was installed in the Mt. Teide Observatory in the late eighties. This telescope enables astronomers to study the dynamics, structure and chemical composition of the solar atmosphere, and offers them the possibility of studying solar granulation trends. For this kind of observations, which require a high degree of spatial resolution, the telescope has a „Solar Correlator”,an instrument that is unique in its class that was developed by the Canary Island Institute of Astrophysics.
Themis Solar Telescope
French astronomers have been interested in the Canary Island skies ever since Jean Mascart, of the Paris Observatory, visited the Canary Islands in 1910, to watch the passage of Halley0s Comet. In fact, the first telescope to be installed in the Mt. Teide Observatory belonged to the Observatory of Bordeaux.
The THEMIS (Heliographic Telescope for Studying Magnetism and Solar Instabilities) was designed by a team of French astronomers from the Observatory of Meudon-Paris. The THEMIS is now a Franco-Italian co-operation project.
With a diameter of 90 cm, THEMIS is the largest solar telescope of the Mt. Teide Observatory, and it is designed to measure the intensity and the direction of the solar magnetic field. One of the features of THEMIS is its ability to operate in several different bands at the same time, a characteristic that is essential for studies of this kind. Moreover, the THEMIS instrumentation provides experimental data on the structure of the solar atmosphere in 3 dimensions.
Visits to the Mt. Teide Observatory
The educational work conducted by the Canary Island Institute of Astrophysics, to disseminate astronomic know-how to society, includes organised visits to the Observatory for schools and other groups. The Mt. Teide Observatory now has a Visitors´ Centre, created from an empty dome, which has been equipped for educational work. With a capacity for forty people, it is used to explain to school children what an observatory is, how the telescopes work and the importance of Astronomy for mankind.
IMPORTANT: The Teide Observatory visits are suspended during the months of November to March due to meteorological reasons. They will be offered to the public from April onwards. Soon will be more information on the IAC website available: http://www.iac.es/eno.php?op1=3&op2=421&lang=en
Fax: 34 / 922 329 117
Web site: www.iac.es
Visits to the Institute of Astrophysics
Visits to the head offices can be arranged with the IAC Management Board
Canary Island Institute of Astrophysics
C/ Vía Lactea, s/n
38200 – La Laguna (Tenerife)
Telephone: 922 605 200 / 207
Web site: http://www.iac.es/ | 0.815667 | 3.477414 |
Habitable TRAPPIST 1 Planets
Last year, NASA astronomers announced the discovery of a solar system with seven Earth-like planets. The TRAPPIST-1 system marked not only the highest number of Earth-like planets ever found around a star, but also the highest number in the “habitable zone,” a region where temperatures aren’t so extreme as to extinguish the planets’ chances of supporting life.
Of the three potentially habitable TRAPPIST 1 planets, scientists now have new evidence that two could support life. Their research has been published in Astronomy & Astrophysics.
For their study, the team, which was led by Amy Barr, a planetary geophysicist at the Planetary Science Institute, first produced compositional models of the seven TRAPPIST-1 planets and their interiors. Using those models, they determined that six of the worlds likely bear either liquid water or ice, with one of the planets potentially home to a global ocean.
The next step was to plot each planet’s orbit in order to estimate its surface temperature. The planets in the Trappist-1 system have unusual, egg-shaped orbits, which cause them to stretch and squeeze in a way that can create heat in their interiors.
This phenomenon, known as tidal heating, not only warms up a planet, it can also promote chemistry and flow in its mantle, which produces conditions conducive to life as we’ve observed on Earth.
The researchers determined that planets b, c, d, and e all experience tidal heating. However, d and e experience much less and are the two most likely habitable TRAPPIST 1 planets.
Barr told The Guardian that d and e sit in a “kind of temperate region” with “very reasonable surface temperatures.” The team believes planet d has a temperature between around 15 degrees Celsius (59 degrees Fahrenheit) and just above the melting point of ice. Planet e would be colder, according to Barr, roughly akin to the temperatures found at Earth’s Antarctic region.
The Search Continues
At present, mathematical models are our best method of learning about the conditions of the various planets in the TRAPPIST-1 system. However, they leave some major gaps in our knowledge, like the question of whether any of the planets possess a significant atmosphere.
Thankfully, various projects are underway that will allow us to observe exoplanets, include the potentially habitable TRAPPIST 1 planets, in more detail.
One of those is the James Webb Space Telescope (JWST). The highly anticipated telescope is scheduled to launch in early 2019, and once it’s up and running, exoplanets will be among the first bodies it’s used to study.
Besides the JWST, a number of Earth-based observatories are on track to be completed the near future, and they’ll also contribute to exoplanet research. Both the Giant Magellan Telescope (GMT) and the Extremely Large Telescope, set for completion in 2025 and 2021, respectively, could potentially tell us a great deal about whether or not these planets are habitable.
Our study of exoplanets is still in its earliest stages — we only just confirmed they existed in 1992. Since then, we’ve confirmed 3,726 planets across 2,792 systems, including around 20 that could potentially be habitable. As we develop better tools to observe these worlds, we’ll be able to make more informed assumptions about their conditions. | 0.894844 | 3.834028 |
Barnard's star is a red dwarf, and has the largest proper motion (apparent motion across the sky) of all known stars. At a distance of 1.8 parsecs1, it is the closest single star to the Sun; only the three stars in the α Centauri system are closer. Barnard's star is also among the least magnetically active red dwarfs known2,3 and has an estimated age older than the Solar System. Its properties make it a prime target for planetary searches; various techniques with different sensitivity limits have been used previously, including radial-velocity imaging4-6, astrometry7,8 and direct imaging9, but all ultimately led to negative or null results. Here we combine numerous measurements from high-precision radial-velocity instruments, revealing the presence of a low-amplitude periodic signal with a period of 233 days. Independent photometric and spectroscopic monitoring, as well as an analysis of instrumental systematic effects, suggest that this signal is best explained as arising from a planetary companion. The candidate planet around Barnard's star is a cold super-Earth, with a minimum mass of 3.2 times that of Earth, orbiting near its snow line (the minimum distance from the star at which volatile compounds could condense). The combination of all radial-velocity datasets spanning 20 years of measurements additionally reveals a long-term modulation that could arise from a stellar magnetic-activity cycle or from a more distant planetary object. Because of its proximity to the Sun, the candidate planet has a maximum angular separation of 220 milliarcseconds from Barnard's star, making it an excellent target for direct imaging and astrometric observations in the future.
- Pub Date:
- November 2018
- Astrophysics - Earth and Planetary Astrophysics;
- Astrophysics - Solar and Stellar Astrophysics
- 38 pages, 7 figures, 4 tables, author's version of published paper in Nature journal | 0.833924 | 3.958469 |
Astrophysicist Neil deGrasse Tyson’s smooth voice and cool manner steered the Ship of Imagination through the known history of the cosmos and through the development of modern science in the debut episode of “Cosmos: A Spacetime Odyssey” on Sunday.
Reviving the immensely popular show “Cosmos: A Personal Voyage,” hosted by the late Carl Sagan, Tyson has some big shoes to fill.
Here’s a look at Tyson’s maiden voyage, taking the Ship of Imagination’s helm and setting it on course for a 13-episode series (the Ship of Imagination was a feature of Sagan’s show, adopted also in the current series).
Episode 1, titled “Standing up in the Milky Way” begins with a promise. Tyson tells the audience he will explore everything we know from the “infinitesimal to the infinite,” taking us through universes smaller than atoms and other wonders of the cosmos.
He breaks up the known universe into various lines of our cosmic address. The solar system is one line; the Milky Way galaxy is another; the Virgo supercluster—a group of about 100 billion galaxies of which ours is but one— is the last known line of our address.
File photo of star cluster M13. (Shutterstock)
The perspective in the episode continually pans out for a broader and broader perspective in which our world is a smaller and smaller speck.
Skimming over Venus, we see the “runaway greenhouse effect has turned it into a kind of hell,” says Tyson. Understanding this effect on Venus was one of Sagan’s major contributions to science. Jupiter’s red spot, a hurricane three times the size of Earth, provides the first comparison by which we see our planet’s size diminishing in the ever-expanding view.
Beyond Voyager 1—the spacecraft that has traveled farther than any other launched from Earth—and beyond the cloud of comets that encircles our solar system, we enter “the deeper waters of this vast cosmic ocean.”
Seeing What We Couldn’t Before
On the subject of extraterrestrials, Tyson speaks of the possibility that life may exist outside our concept of life. “But what do we know about life?” he asked. “We’ve met only one kind before—Earth life.”
Our eyes have limited sight. Tyson shows that when we first started to view space in infrared, the kind of technology used in night-vision, we found way more stars and planets than we could see before.
The visuals are engaging, and even elegant in the way they flow. Tyson’s descriptions are even poetic at times; he describes the rogue planets detected by infrared as “orphans cast away from their mother stars during the chaotic birth of their native star systems.”
On the right is the Orion Nebula as seen with infrared, on the left is the same nebula without infrared. (NASA/JPL-Caltech/Univ. of Toledo/NOAO)
‘Feeling a Little Small’
The bubble theory has its place in this episode. The screen pans out to show our universe as a bubble surrounded by many other bubbles—so many, in the end, that each universe is like a droplet of water in a massive, rushing waterfall.
“Feeling a little small?” asks Tyson. “We may just be little guys living on a speck of dust afloat in a staggering immensity.”
This is where he takes us back to Earth.
Niagara Falls (Shutterstock)
An animated episode tells the story of Giordano Bruno, a 16th-century friar who said the sun is simply a star like so many others. He burned at the stake for his heresy.
A thread that ran through the episode was the idea that science has been wrong before—that the scientific community has been so certain of its knowledge that it would shun bold individuals who proposed different perspectives.
Will we see Tyson propose any bold or new perspectives throughout the series? Thus far, it all seems to fit fairly well within the bounds of conventional scientific understandings.
Bruno had a vision, a startlingly accurate vision of the structure of the cosmos. He was not a scientist. Tyson calls Bruno’s understanding and vision a “lucky guess.” He falls short of considering Bruno’s ability to accurately understand the cosmos through a spiritual vision an ability that may relate to the little-understood wonders of the human mind.
Portrait, a derivative modern illustration of Giordano Bruno taken from a modern version of “Livre du Recteur” (1578), University of Geneva. (Wikimedia Commons)
History of the Cosmos in a Scale That’s Easier to Understand
File photo of a calendar. (Shutterstock)
Another historical perspective fills the second part of the cosmic saga. The history of the known universe is put in terms of a calendar year. Jan. 1 is the Big Bang, Dec. 31 is now. Every month is a billion years and every day is 40 million years.
The Big Bang is presented like a scene from an action movie, with Tyson facing the huge explosion, a silhouette with his arms heroically outstretched.
The first stars appeared on Jan. 10, our sun appeared on Aug. 31 (4.5 billion years ago), and the final 14 seconds of Dec. 31 are recorded human history.
Moses was born seven seconds ago, Buddha six seconds ago, Jesus five seconds ago, Mohammed three seconds ago, and at the very last second came the scientific method.
Tyson wrapped up the episode with thoughts of Sagan. Tyson first met Sagan in 1975. Sagan, already famous, took the time to meet with this 17-year-old from the Bronx who had aspirations of becoming a scientist. They spent a Saturday afternoon together in Ithaca, N.Y. Sagan signed a book for Tyson with the message, “For Neil, a future astronomer.”
Forty years later, Tyson has taken the torch from Sagan and continued on a mission to bring scientific exploration to a broad audience. He closed the first episode with the words, “Now, come with me, our journey is just beginning.”
Carl Sagan, a co-founder of The Planetary Society, at the incorporation of the Society in 1980. (NASA/JPL)
Nat Geo will rebroadcast the episode on Monday, March 10 at 10 p.m. ET with extra content. The next episode, “Some of the Things That Molecules Do,” will air on March 16, 2014 at 9 p.m. ET in the United States across 10 networks of 21st Century Fox. This includes Fox, FX, FXX, FXM, Fox Sports 1, Fox Sports 2, National Geographic Channel, Nat Geo WILD, Nat Geo Mundo, and Fox Life. It will air in other countries on Fox channels and National Geographic Channels International. | 0.900027 | 3.34755 |
where L = M2I2 in Figs. 2.11 and 2.12. In terms of ray trace parameters L = s2. Note that Eq. (2.57) is only valid if |L| > |d1|, i.e. if b > 0, since otherwise the true length of the system is given by |d1|, not |L|.
Another fundamental parameter of these compound telescope forms is the axial obstruction ratio Ra. This is given by
yi / f from the geometry of Figs. 2.11 and 2.12. Eqs. (2.57) and (2.58) give the simple relationship
This result essentially explains why the compound (2-mirror) telescope has triumphed over the single mirror form and is the standard solution for modern astronomy. Historically it was desirable to have a large scale (see § 2.2.6 below) and therefore a long focal length f . A solution with a large T giving reduced length is exactly what is needed. The fact that a large value of T gives a small axial obstruction from (2.59) is a marvellous added attraction. Of course, we have said nothing about the difficulties of manufacture and test which, as we shall see in Chap. 5 and in RTO II, Chap. 1 and 3, have been formidable.
Formally, from (2.57) and (2.59), there is no difference between the Gregory and Cassegrain solutions. However, there is a further parameter to be introduced which makes the Cassegrain solution much superior for normal purposes, i.e. where a real primary image is of no consequence. The notable exception is the Gregory form for solar telescopes, in which the intense heat of the bulk of the solar image can be absorbed at the real prime focus. The parameter favouring the Cassegrain form is the position of the final image I2. For a fixed, convenient position behind the primary and a given value of
Ra, the Cassegrain allows a larger relative aperture u2 or a shorter value of / because L is shorter. This is evident from Figs. 2.11 and 2.12 but will be proven by the formulae below.
Applying (2.34) and (2.35) to the secondary, we have
giving with L = s2
Was this article helpful? | 0.826155 | 3.512973 |
CAPE CANAVERAL, Fla. — For the first time, astronomers have discovered what could be an exomoon, a moon outside our solar system.
The so-called exomoon, which is estimated to be the size of Neptune, was found in orbit around a gigantic gas planet 8,000 light-years from Earth.
Although moons are common in our solar system, which has nearly 200 natural satellites, the long search for interstellar moons has been an empty one.
Astronomers have had success locating exoplanets around stars outside our solar system, but exomoons are harder to pinpoint because of their smaller size.
“This would be the first case of detecting a moon outside our solar system,” said David Kipping, an assistant professor of astronomy at Columbia University and one of the discoverers of the potential exomoon.
“If confirmed by follow-up Hubble observations, the finding could provide vital clues about the development of planetary systems and may cause experts to revisit theories of how moons form around planets.”
Kipping has spent a decade working on the “exomoon hunt.”
But the scientists behind this discovery are hesitant to confirm that the new find is an exomoon because of some of its peculiarities and the fact that more observation is needed. Their results were published Wednesday in the journal Science Advances.
“This is not by itself a proof of an exomoon,” Kipping said. “It’s the unknown of unknowns which are ultimately uncharacterizeable.”
However, the finding is both promising and intriguing.
The moon, which orbits a giant exoplanet called Kepler-1625b, is incredibly large, comparable to the size of the gas giant Neptune in our solar system.
There’s no analog for such a large moon in our own system. In our sky, it would appear two times bigger than Earth’s moon, the researchers said.
But that size is why it was easier to find, the researchers said.
It’s comparable to so-called hot Jupiters, gas giant exoplanets that are closer to their stars than Jupiter is to its own, and warmer.
These were common discoveries during the early days of exoplanet hunting because they were easy to find, but they represent only about 1 percent of known exoplanets now.
The planet that the potential exomoon orbits, Kepler-1625b, is several times the mass of Jupiter, which means their mass-ratio is similar to that of Earth and its moon.
It was discovered when Columbia astronomers Kipping and Alex Teachey used NASA’s Hubble Space Telescope to follow up on an intriguing find from data in the Kepler Space Telescope’s exoplanet catalog.
This catalog included 284 planets found by Kepler with wide orbits around their host stars. Kepler-1625b stood out.
“We saw little deviations and wobbles in the light curve that caught our attention,” Kipping said.
The researchers were awarded with 40 hours of observation time using Hubble, and the data they gathered were four times more precise than what Kepler had captured.
During a transit period, in which the planet passed in front of its star, Hubble detected a second decrease in the star’s brightness after the planet.
It was like “a moon trailing the planet like a dog following its owner on a leash,” Kipping said. “Unfortunately, the scheduled Hubble observations ended before the complete transit of the moon could be measured.”
Hubble was also able to measure that the planet began its transit earlier than expected, consistent with the “wobble” that occurs when a planet and moon orbit the same center of gravity. This also happens with Earth, the moon and the sun.
Perhaps that wobble could be due to the presence of a second planet, the researchers thought. But Kepler didn’t find any other planets around this star.
“A companion moon is the simplest and most natural explanation for the second dip in the light curve and the orbit-timing deviation,” Teachey said.
“It was a shocking moment to see that light curve. My heart started beating a little faster, and I just kept looking at that signature. But we knew our job was to keep a level head, testing every conceivable way in which the data could be tricking us until we were left with no other explanation.”
Although the planet and its possible moon are within the habitable zone of their star, both are considered to be gas giants and “unsuitable for life as we know it,” Kipping said.
It’s not like the exomoon in “Avatar” or Endor from “Star Wars,” Teachey said, “but going forward, I think we’re opening doors to finding worlds like that.”
The researchers believe the star system to be 10 billion years old, which means it’s had time to evolve. This could explain why the moon is 3 million kilometers from its planet; they were probably closer in the past.
They estimate the surface temperature of both to be 176 degrees.
The star was probably cooler in the past, so this heat could be a reason for the size of the moon, inflating the gas giant as the temperature rises. But until they have more data, this is only speculation, Kipping said.
How did this moon form in the first place? There are three primary theories about how moons form.
One is when planets impact larger bodies and the blasted-off material becomes a moon.
Another is capture, when objects are captured and pulled into orbit around a large planet — like Neptune’s moon Triton, which is believed to be a captured Kuiper Belt object.
And the third is moons forming from the disc materials that created the planets in the early days of the solar system.
Impact isn’t possible here because these are both gaseous objects. And this moon’s size defies explanation. So it remains a mystery — for now.
Teachey and Kipping are submitting proposals for more time on Hubble to observe this planet and its moon during another transit.
If they are able to observe a full transit, representative of a “clean moonlike event, then I think we’re done,” Kipping said.
That would confirm that the find is an exomoon.
But for now, the researchers welcome comment and criticism of their hypothesis from other astronomers as part of the scientific process.
In the Kepler exoplanet catalog, there are only a few Jupiter-size planets that are farther from their star than Earth is from the sun — good candidates for moons because of the distance.
Once the James Webb Space Telescope launches in 2021, the search for exomoons may be full of possibilities. “We can expect to see really tiny moons,” Kipping said. | 0.903244 | 3.861605 |
There are many matters in the Universe we are nonetheless to have an understanding of. It’s a major previous device just churning out mysteries, and we tiny specks crawling on the floor of a tiny blue dot are carrying out our darnedest to unravel them.
Not long ago, information emerged about a person of the most tantalising mysteries. For the 1st time, a rapid radio burst (FRB) has been detected emitting in a pattern – a 16-day cycle, with four days of intermittent bursts and twelve days of silence.
We still really don’t know what results in these really strong, millisecond blasts of radio waves from up to billions of gentle-several years absent. Most of them haven’t been detected repeating, most of them are wildly unpredictable, and only 5 out of around 100 have been traced to a source galaxy.
It’s established really tricky to come across a cosmic phenomenon that fits the profile of FRBs. Violent, very magnetised neutron stars identified as magnetars are rather near, but you will find some doubt as to no matter whether they can emit the nova-scale energies detected in rapid radio bursts.
But the absence of a good explanation consequently far will not signify we really should quickly transform to aliens, as so many headlines have done. When uncommon cosmic phenomena look, rampant speculation comes at this recommendation all also immediately.
“Invoking aliens has come to be also systematic, also quick, and also sensationalist a way to get the public’s consideration … [It] reminds me of the way we utilised to invoke gods,” planetary scientist and astrobiologist Charley Lineweaver of the Australian National University (ANU) advised ScienceAlert.
“Rather of ‘gods of the gaps’ we now have ‘aliens of the gaps’.”
Alien communication complications
In 2017, some physicists proposed that the rapid radio burst alerts could be generated by radiation leaking from alien spaceship propulsion systems. Others have place forward that it could be a person-way alien communication.
“My knowing is that those explanations are not excluded by the readily available proof,” physicist Paul Ginsparg of Cornell University, and the founder of arXiv, advised ScienceAlert.
“But also that they are not expected by it, in the feeling that there stay similarly or far more plausible explanations that really don’t use extraterrestrial intelligence.”
One major difficulty for the alien thought is the variety of places and distances concerned. Of the FRBs that have been localised, some are from billions of gentle-several years absent others are from hundreds of hundreds of thousands.
As astronomer Seth Shostak of the SETI Institute has noted, that by yourself is cause sufficient to price reduction the hypothesis that FRBs are extraterrestrial communications.
“How could aliens organise so substantially of the Universe to have interaction in broadcasting the very same sort of signal?” he wrote in a site put up final year.
“You can find barely been sufficient time considering that the Massive Bang to coordinate these prevalent teamwork, even if you can imagine of a cause for it!”
For the bursts to have an artificial origin, at minimum 100 various alien species would have to be technologically state-of-the-art to generate these a strong signal that it can transfer across room and still be detected by us.
For context, here on Earth, we only developed know-how that could beam radio waves into room just all over 125 several years ago. That indicates that any radio transmission from Earth would only have travelled, at a maximum, 125 gentle-several years. By the time the signal has propagated that far, it would have come to be also attenuated to be detected.
That is not to say that a far more state-of-the-art civilisation could not generate a strong signal… but you will find another difficulty. All these hypothetical alien civilisations would’ve had to have developed their systems at just the correct time, so that all their alerts are reaching Earth in the very same handful of several years.
Are we by yourself?
To day, we have had no credible proof that there are other smart, state-of-the-art civilisations out there. This lack of proof for other civilisations seems paradoxical in the context of the Drake Equation, which implies there really should be very a number of of these civilisations all over.
But really should there? Of all the multitudinous species on Earth, only individuals have human-like intelligence. In transform, this implies that our form of intelligence is a quite extended way from inescapable.
“My studying of organic evolution on Earth is that human-like intelligence is not a convergent element of evolution,” Lineweaver advised ScienceAlert.
“The base line to my contemplating is that the finest info we have (info from evolution here on Earth) strongly suggest that our closest family members in the Universe are here on Earth.”
So, there are logistical causes to imagine that rapid radio bursts are natural in origin. As was also inevitably uncovered with interstellar object ‘Oumuamua, another goal of enthusiasm for alien presence – there is in fact proof in the info that the phenomenon is a natural a person.
“I imagine the finest argument towards the extraterrestrial hypothesis is that we see FRBs with all types of weird qualities (some vast, some narrow, some polarised, others not, some have various pulses, some are a solitary pulse),” an FRB astronomer, who wished to stay anonymous for problem of remaining targeted by conspiracy theorists, advised ScienceAlert.
“If I have been developing a spacecraft propulsion process (which would be bloody excellent fun), I am not absolutely sure some of those qualities (e.g. changing polarisation around the pulse), would make a much better spacecraft engine.
“On the other hand, we do see a identical diversity of qualities in pulsars, which everyone agrees are a natural phenomenon.”
This line of contemplating is also supported by astronomer Andy Howell of Las Cumbres Observatory and the University of California Santa Barbara.
Why #FRBs usually are not aliens, part three. The frequency sweep predicted how far absent #FRBs would be, and then they have been uncovered to be reliable with those distances. That is discussed by a natural approach. For communication you want a little something unnatural. 14/
— Andy Howell (@d_a_howell) February twelve, 2020
The worth of wild concepts
All that just isn’t to say you will find no worth in thinking about the alien explanation. It’s vital for experts to preserve an open up mind, to be receptive to prospects, even if they are tiny kinds.
Consider the situations – even nevertheless they only constitute a tiny proportion – of hypotheses in the beginning derided by the scientific community, only afterwards to be broadly approved. The existence of tectonic plates will come to mind.
Wild concepts can also support to have interaction the public with science not just the discoveries by themselves, but the work experts do to existing the hypothesis, deliver proof for it, and produce a theory.
And there are realistic prospects, also.
“These discussions give non-experts an indication of the types of the astounding observations remaining created, the fun that experts have contemplating about them, and the prospects that are out there,” Ginsparg advised ScienceAlert.
“Wild speculation can at times inform the up coming technology of instrumentation, which can then both validate or refute the wild hypothesis, or see a little something else solely and surprising. And that also is what would make science fun.”
The issue lies in knowing the change in between pondering wild concepts as a assumed exercise, and proof primarily based on info and prior knowledge, observation and conclusions.
Or, as Ginsparg place it, “in a discussion about string theory, a senior physicist once argued to me that a person won’t be able to ‘prove’ you will find no Santa Claus, but we have alternate methods of detailing the noticed phenomena with fewer unneeded assumptions.”
So, for now, we will be keeping off on the aliens until finally the aliens convey to us normally. | 0.918703 | 3.005661 |
Scientists at the Harvard-Smithsonian Center for Astrophysics (CfA) and their colleagues at the Heidelberg Institute for Theoretical Studies (HITS) have invented a new computational approach that can accurately follow the birth and evolution of thousands of galaxies over billions of years. For the first time, it’s now possible to build a universe from scratch that brims with galaxies like those we observe around us.
Our cosmic neighborhood is littered with majestic spiral galaxies such as the Andromeda, the Pinwheel, and the Whirlpool. Spirals are common, but previous simulations had trouble creating them. Instead, they produced lots of blobby galaxies clumped into balls, without the broad disks and outstretched arms of a typical spiral.
The new software, called Arepo, solves this problem. Created by Volker Springel, group leader at HITS, Arepo generates a full-fledged simulation of the universe, taking as input only the observed afterglow of the big bang and evolving forward in time for 14 billion years.
“We took all the advantages of previous codes and removed the disadvantages,” explained Springel.
“Our simulations improve over previous ones as much as the Giant Magellan Telescope will improve upon any telescope that exists now,” said Debora Sijacki of the CfA and a fellow at the Harvard College Observatory.
(When completed later this decade, the Giant Magellan Telescope’s 24.5-meter aperture will make it the largest telescope in the world.)
One of Arepo’s key advantages is the geometry it uses. Previous simulations divided space into a bunch of cubes of fixed size and shape. Arepo uses a grid that flexes and moves in space to match the motions of the underlying gas, stars, dark matter, and dark energy.
The simulations ran on Harvard’s Odyssey high-performance supercomputer, using in total 1,024 processor cores. This fast machine allowed the scientists to compress 14 billion years into only a few months — an endeavor that would have kept a desktop computer busy for hundreds of years!
The team’s future goals include simulating much larger volumes of the universe at unprecedented resolution, thus creating the largest and most realistic model of the universe ever made. | 0.836835 | 3.746692 |
Last week, the Planetary Society's Red Rover Goes to Mars Student Scientists made planetary exploration history. They were the first members of the public to direct a camera aboard a spacecraft orbiting another world, the NASA Mars Global Surveyor (MGS). One of the pictures they targeted shows something new about the planet's surface -- a surprising cluster of dark-colored boulders smack dab in the middle of light-colored terrain. How the boulders got there and what geological history they represent on Mars are questions scientists still need to answer.
"It's puzzling," said Michael Carr of the US Geological Survey. "I looked at a few pictures around [the area] and couldn't find anything to explain it. Very puzzling! These are huge boulders. There are no indications of any outcrops that could shed such boulders."
"Wow! These have me totally stumped," commented Ron Greeley of Arizona State University. "Not only is the dark color of the boulders a surprise, but they appear totally out of context in the surrounding terrain. There is nothing in the rest of the image to suggest a source for such large boulders, nor their arrangement on the surface."
The Red Rover Goes to Mars Training Mission is comprised of an international team of nine students -- aged 10 - 16 years old. They gathered in Carlsbad, California during the week of February 11-17 to work at Malin Space Science Systems, which built and operates the camera on MGS, to select and image several sites on the Martian surface.
Michael Malin, of Malin Space Science Systems, remarked, "The location and nature of these boulders is unusual, but their shape and distribution -- in respect to the slope upon which they sit -- is consistent with a boulder shattered by weathering. The fall to their present location could also have broken the boulders apart. The mystery is why so much of the rest of the slope is smooth and devoid of blocks."
At Malin Space Science Systems in San Diego, the team imaged three sites that coincided with the MGS spacecraft's orbital position during the week of their visit, as well as another site that the students deemed a candidate landing site for a possible sample return mission at some future date. That image will be taken when the MGS spacecraft's orbit takes it past the target area some time in the next five months. Michael Malin, Ken Edgett, and Becky Williams of Malin Space Science Systems personally supervised the Student Scientists.
While all three images of Mars taken last week by the Student Scientists are fascinating, one is particularly intriguing as much for its simplicity as for its implications. That view of fretted terrain includes the Nilosyrtis Mensae Valleys, sand dunes and the mysterious black boulders, which are clustered in the lower left hand portion of the image in a tight grouping.
The Student Team captioned the image on Malin Space Science Systems' website:
"This image was taken in the fretted terrain area located in the middle latitudes of Mars. Interesting features in this area are dunes, valleys, and mysterious black boulders that are as big as 15 to 25 meters (49 to 82 feet). The puzzling position of these mysterious rocks and the lack of our ability to understand how they got there reminds us how much there is still left to discover about our mystery planet."
The other two Student Scientist-directed images of Mars include a view of what may be alluvial fan material, with evidence of possible flowing water, and the layered terrain of the polar ice cap.
All of the images, including a close-up of the mystery boulders, can be accessed on The Planetary Society's website.
The Student Scientists were selected from over ten thousand entrants worldwide. The team includes four girls and five boys who hail from around the globe: Brazil, Hungary, India, Poland, Taiwan, and the United States. These young people were chosen from a field of 80 semi-finalists, who represented 16 nations. Forty-four nations participated in the contest.
LEGO is a principal sponsor of the Red Rover Goes to Mars project of the Society, which is being conducted in cooperation with NASA and the Jet Propulsion Laboratory. LEGOLAND California also helped sponsor the Student Scientists' visit to the United States. No government funding is used for this educational project. Mars Global Surveyor is managed by NASA's Jet Propulsion Laboratory, Pasadena, California.
Reports about the Red Rover Goes to Mars Training Mission are available on The Planetary Society's website
The Red Rover Goes to Mars team members are Zsofia Bodo, 16, Hungary; Kimberly DeRose, 14, USA; Bernadett Gaal, 14, Hungary; Shaleen Harlalka, 15, India; Iuri Jasper, 12, Brazil; Hsin-Liu Kao, 11, Taiwan; Tanmay Khirwadkar, 13, India; Wojciech Lukasik, 10, Poland; and Vikas Sarangadhara, 10, India. | 0.871957 | 3.706975 |
A study by the Instituto de Astrofísica de Canarias (IAC), led by researchers Nushkia Chamba, Ignacio Trujillo and Johan H. Knapen, reveals that the enigmatic ultra-diffuse galaxies, very low-luminosity and low-density star galaxies, are similar in size to dwarf galaxies. The results, which are published in the journal Astronomy & Astrophysics, provide new clues about the number and type of galaxies in our Universe and about the nature of dark matter.
IAC scientists have taken a major step towards understanding the nature of the mysterious and ghostly ultra-diffuse galaxies (UDGs). These galaxies have caught the attention of astronomers due to their extreme properties, such as their low luminosity and very low stellar density. In fact, UDGs can be about 10 times fainter than the night sky or about a 100 times fainter than our Milky Way.
Until now, it was thought that these kinds of galaxies were either enormous objects, like our Milky Way, but comparatively very inefficient in forming stars, or were simply small galaxies without active star formation in their centres. Now IAC astronomers have discovered that the extensions or sizes of UDGs are more similar to those of dwarf galaxies, ending an intense scientific debate on this issue. On average, UDGs are 10 times smaller than the Milky Way analogues.
“Its really a step forward to discover that the sizes of these very faint ultra-diffuse galaxies are not at all as large as our Milky Way and that they are more similar to the small dwarf galaxies”, says Nushkia Chamba, IAC researcher and first author of the article. “It definitely changes how the community has been viewing the nature of these objects and how they compare with other classes of galaxies”.
The researchers have managed to measure the luminous size of the UDGs through a new physically motivated definition of galaxy size. “To address this problem, we have had to rethink from scratch the meaning of size for galaxies”, explains Ignacio Trujillo, an IAC researcher who is also participating in the study. “This is not at all a trivial problem because galaxies do not have clear edges like regular, everyday objects such as tables, humans, cars, etc."
Usually, astronomers use parameters such as the effective radius, that is, the radius within which half of the total light emitted by the galaxy is concentrated, to measure the luminous sizes of galaxies. However, these parameters were introduced when images of galaxies were much shallower than current ones, so they have no direct physical meaning and are defined arbitrarily. Instead, the new measurement is based on the location of the gas density threshold of required for star formation in galaxies, which better represents what the human eye identifies as the edges or boundaries of galaxies.
The new parameter allows us to fairly compare the nature of different types of galaxies, which has strong consequences for the understanding of the number and class of galaxies in our Universe, and ultimately give us clues about the nature of dark matter.
This study has been carried out within the framework of the SUNDIAL project (SUrvey Network for Deep Imaging Analysis and Learning), an Innovative Training Network of the European Union whose objective is to train young researchers in the fields of computer science and astronomy, and to develop innovative algorithms to study the very large databases from current telescopes.
For IAC researcher and also author of the article Johan H. Knapen, “This is a great example of how the work we do within our EU-funded training network SUNDIAL, a close collaboration between astronomers and computer scientists, leads to real advances in our understanding of how galaxies are structured and how they evolve”.
Article: Chamba, N., Trujillo, I. & Knapen, J. H. “Are ultra-diffuse galaxies Milky Way-sized?” 2020, A&A, 633, L3. DOI: https://doi.org/10.1051/0004-6361/201936821 y
Article "What are the sizes of galaxies?" by Nushkia Chamba in the SUNDIAL blog
SUNDIAL web page: and
Nushkia Chamba, IAC researcher: chamba [at] iac.es
Ignacio Trujillo, IAC researcher: trujillo [at] iac.es
SUNDIAL (SUrvey Network for Deep Imaging Analysis & Learning) is an ambitious interdisciplinary network of nine research groups in The Netherlands, Germany, Finland, France, the United Kingdom, Spain, Belgium and Italy. The aim of the network is to develop novel algorithms to study the very large databases coming from current-day telescopes to
Astronomy and computer science will be the fields for training young European researchers in order to understand the formation and evolution of galaxies. | 0.818658 | 4.04816 |
Table of Contents
Introduction to Black Hole
Black holes are supermassive objects from where nothing can escape, not even light. The edges of black hole are the point of no return called event horizon. But scientists finally succeeded in designing the first ever image of the shadowy edge of a supermassive black hole. This huge discovery in the history of mankind has led us to a different way of understanding the universe.
Although we have got an image of a black hole, the topic of black hole is not new. The existence of black hole was predicted by Albert Einstein’s general theory of relativity more than 100 years ago. Many scientists supported it including latest great scientist, Stephen Hawking. Now we have got a solid proof the existence of black hole after about 65 years of passage of Einstein.
About First Image of Black Hole
On Wednesday, April 10, 2019, scientists have released the image of an active supermassive black hole which is located in the center of an elliptical galaxy. The black hole is named as Meisser 87 (M87)and is present about 15 million light years from us. It is 6.5 billion times the solar mass and 40 billion kilometers across. The image was captured by using the Event Horizon Telescope (EHT).
It is circular but on one side, light is brighter because the light is approaching the earth.
“The image had an orange, yellow and black ring which was obviously a black hole and its surrounding”, said Havard’s shepherd Doelemon, Director of EHT team.
An EHT team member and astronomer at University of Waterloo, Broderick said,” The shadow exists in nearly circular and the inferred mass matches estimates due to dynamics of stars 100,000 times farther away.”
Prediction by Einstein’s General Theory of Relativity
It was theoretically predicted by Einstein’s general theory of relativity more than 100 years ago. The image of black hole fully supports the theory of relativity. It is crescent – shaped as predicted by Einstein. The circular disc is an event horizon from where nothing can escape. The portion is the core of black hole and is totally black. Einstein’s prediction about the shape and glow of a big black hole is also proved right.
Einstein’s theory has not only passed this test but every challenge over the last 100 years. He has been right all along.
E.g. Einstein predicted gravitational wave which is created by massive accelerating objects.
In 2015, LIGO (Laser Interferometer Gravitational Waves Observatory) confirmed the ripples in space-time which were gravitational waves.
It was observed when two small black holes were merging.
After a decade, we have finally figured out about black hole which Einstein explained earlier. It took a lot of efforts for many scientists working for years and collecting millions of GBs of data to create a single picture of black hole. Hats off to all the scientists who theorized, supported, researched and proved about the existence of black hole. | 0.866382 | 3.784539 |
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