text
stringlengths 286
572k
| score
float64 0.8
0.98
| model_output
float64 3
4.39
|
|---|---|---|
Wondering what’s that big bright star that was visible all night? It was the planet Jupiter, and it’s far brighter than any true star in the night sky. Jupiter can already be seen twinkling low in the east after twilight, and higher in the southeast as the evening wears on.
Even the skies seemed to be cloudy at night here in the Philippines, Jupiter often still stands out amidst the dark sky. 😀
This giant gas planet is always bright, but it shines brighter this month. On the 21st (8PM PST), Jupiter will swing closer to Earth (368 million miles away) and shine brighter than at any time between 1963 and 2022 . It will remain nearly this close and bright (magnitude -2.9) throughout the second half of September.
The night of its closest approach is also called “the night of opposition” because Jupiter will be opposite the sun, rising at sunset and soaring overhead at midnight. This opposition is special because Jupiter, the largest of all the solar system’s planets, will soon reach perihelion, the closest point in its orbit to the Sun. That means it’s physically closer to Earth during this opposition than a normal one. It will rise below the Circlet asterism in the constellation Pisces the Fish and present its best views high in the sky, when its light travels through less of Earth’s atmosphere.
Because Jupiter is so close to Earth, this is a great opportunity to view it through a telescope. Jupiter is most interesting when the Gred Red Spot is visible and/or when one of the moons is casting a shadow on Jupiter’s disk.
Happy sky viewing! 😀
* * * * * *
Fast facts about Jupiter
- Jupiter is the largest planet in the solar system. More than 1,000 Earths could fit inside Jupiter, and all the other planets together make up only about 70 percent of Jupiter’s volume.
- It takes Jupiter about 12 years to orbit the Sun once, but only about 10 hours to rotate completely, making it the fastest-spinning of all the solar system’s planets.
- Jupiter rotates so rapidly that its polar diameter, 41,600 miles (66,900 kilometers), is only 93 percent of its equatorial diameter, 44,400 miles (71,500 km).
- Jupiter reflects 52 percent of the sunlight falling on it, more than any other planet except Venus (65 percent).
- Jupiter’s four bright moons, Io, Europa, Ganymede, and Callisto, are easily visible through small telescopes. Io takes less than 2 days to orbit, so its relative position visibly changes in an hour or so — less when it appears close to Jupiter.
- Our line of sight lies in the plane of the jovian moons’ orbits, so we see occultations (when a moon moves behind Jupiter), eclipses (when Jupiter’s shadow falls on a moon), and transits (when a moon passes in front of Jupiter) at various times.
- Jupiter’s moon Ganymede is the solar system’s largest satellite, with a diameter of nearly 3,300 miles (5,300 km), greater than that of Mercury.
sources: SkyandTelescope.com, Spacedaily.com, Astronomy.com | 0.874206 | 3.611804 |
Until 500 years ago the premise of an Earth-centric solar system and universe prevailed. And until 100 years ago it was thought that we lived within the confines of a single galaxy, our Milky Way. But in 1915 Albert Einstein introduced general relativity, the highly successful theory of gravity which couples mass, energy and the geometry of space-time. In the 1920s Alexander Friedmann and Georges Lemaitre introduced solutions to the equations of general relativity for an expanding universe. Lemaitre’s work indicated distant galaxies would have their light shifted to be redder than that of nearby galaxies. And by 1929 this was observed by Edwin Hubble. Now with the Hubble Space Telescope we can observe galaxies at much greater distances than Hubble could over 80 years ago. The image above is a very long exposure from the Hubble Space Telescope revealing close to 10,000 galaxies; many of these are billions of light-years away.
Hubble essentially measured the rate of expansion of the universe at the present epoch. The universe is expanding and galaxies are generally receding from one another except when they are gravitationally bound to their near neighbors. The value for the rate of expansion has been refined over the intervening years but is now accurately measured and indicates an age of just under 14 billion years for our universe.
The size of the universe as a whole we are unable to measure! We are limited by our own horizon, due to the finite speed of light. Only galaxies apparently moving away from us at less than the speed of light are within our horizon (also known as light cone). General relativity allows for space itself to stretch at faster than the speed of light if the separations between two galaxies are large enough; objects do not travel faster than light speed within their own local frame.
Our own observable portion of the universe has a lookback time distance of 14 billion light-years and what is known as the comoving distance of nearly 50 billion light-years. The comoving distance takes into account the expansion of the universe as the light moves through it from the Big Bang until now.
Note from the table below how much larger the universe is than the distance to the center of our galaxy or to the nearest star.
Object Distance (light travel time)
Nearest Star 4.2 years
Center of Milky Way 25,000 years
Andromeda Galaxy 2.5 million years
Oldest Galaxies 13 billion years
Big Bang 13.8 billion years | 0.80961 | 3.80925 |
A Johns Hopkins astronomer is a member of a team briefing fellow scientists about plans to use new technology to take advantage of recent, promising ideas on where to search for possible extraterrestrial intelligence in our galaxy.
Richard Conn Henry, a professor in the Henry A. Rowland Department of Physics and Astronomy at Johns Hopkins’ Zanvyl Krieger School of Arts and Sciences, is joining forces with Seth Shostak of the SETI Institute and Steven Kilston of the Henry Foundation Inc., a Silver Spring, Md., think tank, to search a swath of the sky known as the ecliptic plane. They propose to use new Allen Telescope Array, operated as a partnership between the SETI Institute in Mountain View, Calif., and the Radio Astronomy Laboratory at the University of California, Berkeley.
Comprising hundreds of specially produced small dishes that marry modern, miniaturized electronics and innovative technologies with computer processing, the ATA provides researchers with the capability to search for possible signals from technologically advanced civilizations elsewhere in our galaxy – if, in fact, such civilizations exist and are transmitting in this direction.
Employing this new equipment in a unique, targeted search for possible civilizations enhances the chances of finding one, in the same way that a search for a needle in a haystack is made easier if one knows at least approximately where the needle was dropped, said Henry, who is speaking about the proposal at the American Astronomical Society annual meeting in St. Louis.
According to the researchers, the critical place to look is in the ecliptic, a great circle around the sky that represents the plane of Earth’s orbit. The sun, as viewed from Earth, appears annually to pass along this circle. Any civilization that lies within a fraction of a degree of the ecliptic could annually detect Earth passing in front of the sun. This ecliptic band comprises only about 3 percent of the sky.
“If those civilizations are out there – and we don’t know that they are – those that inhabit star systems that lie close to the plane of the Earth’s orbit around the sun will be the most motivated to send communications signals toward Earth,” Henry said, “because those civilizations will surely have detected our annual transit across the face of the sun, telling them that Earth lies in a habitable zone, where liquid water is stable. Through spectroscopic analysis of our atmosphere, they will know that Earth likely bears life.
“Knowing where to look tremendously reduces the amount of radio telescope time we will need to conduct the search,” he said.
Most of the 100 billion stars in our Milky Way galaxy are located in the galactic plane, forming another great circle around the sky. The two great circles intersect near Taurus and Sagittarius, two constellations opposite each other in the Earth’s sky – areas where the search will initially concentrate.
“The crucial implication is that this targeted search in a favored part of the sky — the ecliptic stripe, if you will – may provide us with significantly better prospects for detecting extraterrestrials than has any previous search effort,” Kilston said.
Ray Villard of the Space Telescope Science Institute, who will join the team in its observations, said that in November 2001, STScI publicized Hubble Space Telescope observations of a transiting planet and “it occurred to me that alien civilizations along the ecliptic would likely be doing similar observations to Earth.”
“Once they had determined Earth to be habitable, they might initiate sending signals,” Villard said.
Shostak of SETI notes that the Allen Telescope Array is ideal for the team’s plans to search the entire ecliptic over time, and not just the intersections of the ecliptic and galactic planes.
The team’s presentation at the AAS meeting also explores possible scenarios for the appearance of civilizations in our galaxy.
“These models are nothing but pure speculation. But hey … it is educational to explore possibilities,” Henry said. “We have no idea how many – if any – other civilizations there are in our galaxy. One critical factor is how long a civilization – for example, our own – remains in existence. If, as we dearly hope, the answer is many millions of years, then even if civilizations are fairly rare, those in our ecliptic plane will have learned of our existence. They will know that life exists on Earth and they will have the patience to beam easily detectable radio (or optical) signals in our direction, if necessary, for millions of years in the hope, now realized, that a technological civilization will appear on Earth.” | 0.886497 | 3.403768 |
Though Venus is more like Earth in size, Mars is the planet that regularly makes headlines. New ice under its sandy cliffs has been caught on camera, causing more hope that life may have been present at some point in the past. Prominent people like Elon Musk are talking about going to Mars in the near future.
Scientists are once again planning sustainable living quarters for the colonization of the fourth planet from our sun. This is not the first time humanity has endeavored to send a manned mission there. For more than a century this planet has been popularized in the news as well as in pop culture. Mars has especially held a rich place in world literature.
In 1877, the Italian astronomer Giovanni Schiaparelli said he saw channel-like structures in his observations of the Martian surface. Partially through mistranslation, some scientists further thought these were actually canals built by intelligent life-forms. A few years later, American astronomer Percival Lowell agreed wholeheartedly with Schiaparelli’s so-called findings. Years later, when better telescopes were more readily available, the scientific community for the most part dismissed the concept of the channels for they were not present on the planet’s surface. However, Lowell was no fool. He predicted that another planet in our solar system existed outside Neptune’s orbit.
This extraterrestrial body was indeed discovered (it was called Pluto). But despite their brilliance, Lowell and Schiaparelli (and others) saw things in their telescopes that weren’t really there. It has been suggested that the optics or even tired eyesight brought on the effect that tricked these astronomers. This is still a bit of a mystery.
Prior to the scientific community’s brushing-off of this concept, another French astronomer, Camille Flammarion, wrote several works that would today be considered sci-fi novels. In one of these, Les Terres du Ciel (1884), Flammarion describes the scenery of bodies such as the moon and Mars to his readers. Flammarion’s interest in the moon may have been sparked by the 1865 novel by his fellow countryman Jules Verne, From the Earth to the Moon.
Percival Lowell was also able to write and have published a number of lengthy essays about the proposed life on the Red Planet. His first was a book that was simply called Mars, originally published in 1895. Two more followed: Mars and Its Canals (1906) and Mars as the Abode of Life (1908). Lowell died in 1916, and Pluto would be discovered in 1930 by Clyde Tombaugh.
Around 1898, a mere three years after the publication of Percival Lowell’s first Martian book, H.G. Wells’s epic sci-fi classic The War of the Worlds was published. The story he tells is one of invaders from Mars coming to Earth and leveling cities with their destructive lasers. Humanity retaliates with what it can, but the Martians’ tech is too advanced and efficient. It is fitting that the Earth finds itself in a desperate fight with the inhabitants of Mars, the name for the ancient god of war. The War of the Worlds enjoyed a host of Hollywood film adaptations. It was also converted into a radio play in 1938, late in the Great Depression, and was broadcast and narrated by Orson Welles. His realistic rendition and delivery of the script famously caused a panic throughout the U.S. (although, this historic aspect has been disputed in recent years).
In 1917, the year after Percival Lowell’s death, a novelization entitled A Princess of Mars was published. This book was the first in the Barsoom series; its author was the renowned Edgar Rice Burroughs. Apart from the Barsoom series, Burroughs other famous story was that of Tarzan. Ten sequels were produced, most of them being attributed to Edgar Rice Burroughs. The last of these was John Carter of Mars, which was published in the early 1940s. Barsoom is the Martian word for Mars itself. Thus, the series is referred to as the “Barsoom series.” (It was the basis for the 2012 film John Carter.)
Sci-fi was a new and rising genre in the 1930s. Stanley G. Weinbaum’s short story “A Martian Odyssey” was published around this time. Many stories of the same caliber were being published in that decade. In 1938 (the year Orson Welles made the renowned radio broadcast), a book called Out of the Silent Planet was published. It is often overlooked by sci-fi fans, and yet is was created and penned by one of the greatest fantasy authors of the 20th century. Its author was none other than British professor C.S. Lewis, a good friend of J.R.R. Tolkien. Out of the Silent Planet was the first installment of Lewis’s sci-fi trilogy. The alien planet on which much of the story takes place is Malacandra, which is meant to be Mars.
The next notable literary work is Robert A. Heinlein’s 1949 novel Red Planet. The Martian Chronicles, a collection of short stories about the colonization of Mars by Ray Bradbury, was published the year later. Then in 1951, Arthur C. Clarke’s The Sands of Mars was published. This whole period was filled with Martian literature. The 1950s and ’60s were the golden era of sci-fi, and so Mars appeared frequently in much of the pop culture of the day. Heinlein’s Stranger in a Strange Land (1961) also takes the reader to Mars.
It was really not until the ’90s when quality literature about Mars and Martians became popular again. This is because it was in the 1990s that high-tech probes like Mars Global Surveyor, Pathfinder, and Sojourner landed on the planet, giving us new, more detailed imagery of the Martian surface. The Mars Society was also founded in the late 1990s. In this decade, astronomer and astrobiologist Carl Sagan said, “Because of the historic romance of the general public with Mars (consider even today the associations of the word ‘martian’), the exploration of Mars has a public resonance and support that probably no other goal of the space program can claim.”
In 1993, Greg Bear published his award-winning novel Moving Mars, a futuristic story that discusses many political themes. Kim Stanley Robinson also published numerous Martian novels throughout this decade. Dr. John Gray published a book entitled Men Are from Mars, Women Are from Venus (1992), which covered topics about the psychological differences between men and women. It employed the metaphor of the title to get its point across, picturing that the two sexes originated from two different planets of drastically different societies. Apparently, it was the longest-running nonfiction bestseller of the ’90s. And in 1999, bringing the decade to a close, the novel The Martian Race by Gregory Benford was released.
The most popular Martian-related literary tale next to the classical War of the Worlds did not reach its readers until 2011. This of course is Andy Weir’s widely acclaimed The Martian which, unlike The War of the Worlds, actually takes place on Mars itself. It was adapted for the silver screen and released to theaters in 2015. This obviously helped in popularizing the novel itself.
It was also in 2011 that the poetry collection Life on Mars by Tracy K. Smith was first published. The work features creative pieces that include imagery of numerous objects seen throughout the cosmos. Smith was likely inspired by the life of her father, a scientist involved with the development of the Hubble Space Telescope. Even more recently, Martian anthologies such as Old Mars which was edited by George R.R. Martin and Gardner Dozois have been published.
Even music writers have shown a great fascination with the Red Planet. For instance, English composer Gustav Holst wrote the classical suite “The Planets” between 1914 and 1916. Mars is given tribute in its own section entitled, “Mars—Bringer of War.” In hearing it, it can easily remind the listener of various John Williams soundtracks such as that of Star Wars. Nearly a century after Holst’s composition, in 2012, the singer, voice actor, and songwriter will.i.am had his piece “Reach for the Stars” broadcast from Earth to Mars and back again.
We are entering a new age of Martian exploration in both science and science fiction. Our efforts are being directed at colonizing the sandy celestial body. As humanity strives to reach out toward the Red Planet, more imaginations will be sparked, more pens put to work. Someday soon, writers may find themselves living on a red planet, writing even more far-fetched fantasies than those of their forebears.
Image Credit: Wikipedia. | 0.890575 | 3.311328 |
Experiment with CCD Camera Images
For an astronomer, an image is not necessarily a pretty picture. Indeed the information in each image usually goes far beyond what you can see at first look. Image processing is the technique by which an image can be transformed to reveal (or suppress) selected features, or to extract quantitative information in other forms.
There are three programs we use often in astronomy to acquire, analyze, and modify images:
SAOImage ds9 Aladin ImageJ or AstroImageJ
We may use these in different instances because they offer a different set of features. Aladin, for example is excellent for comparing images with one another and with astronomical data bases, and for making quick color images from several images through different filters. SAOImage ds9 is versatile for acquiring images and interacts in real time with our cameras. ImageJ, written and maintained for biomedical imaging, can be modified for special tasks, and is ideal when we are measuring the brightesses of stars.
In this activity we will use ImageJ because it provides for sensitive control of the colors in an image and preserves all of the information of the original data.
Astronomical images are most often created by placing an electronic detector such as a Charge Coupled Device camera at the focus of a telescope. CCD cameras have an array of sensors exposed to light focused by the telescope. Each sensor records the light from its share of the image. At the end of an exposure, a computer reads them and measures how much light was received point by point in the image. An element of this record is called a pixel. Just as in the camera of your cell phone, state of the art large telescopes use millions of pixels per CCD detector, and may have arrays of detectors side-by-side to cover large swaths of the sky. We use a camera ourselves in other activities. First, however, we will see how we can view and measure the data they return.
We will work with four images recorded in short exposures with our CDK20 south telescope at Mt. Kent, in Queensland, Australia. We have selected images of the Tarantula Nebula, a region of gas and young hot stars in the nearby Large Magellanic Cloud galaxy. There are four images in the data set, taken on the night of October 4, 2010, at about 15:50 UTC by Dr. Rhodes Hart. Each one is a 30 second exposure -- short by astronomical standards, but just long enough to get the nebula without completely saturating the bright stars. He took 4 images through 4 different filters, each one seeing sky in a different range of wavelengths or colors:
The filters are chosen for making precision measurements of the light from stars, not necessarily ideal for making color images that match what the eye sees. The eye is most sensitive at 550 nm, and only 10% as sensitive at 475 nm in blue, and 650 nm in the red. The CCD camera can sense wavelengths as long as 1100 nm.
Click the links to download the images to your own computer, or if you doing this in the astronomy lab, look for them in the directory called "Image Processing".
- ngc2070_I_ij.fits through the I filter
- ngc2070_R_ij.fits through the R filter
- ngc2070_V_ij.fits through the V filter
- ngc2070_B_ij.fits through the B filter
We have already done some processing on them for you by subtracting the response of the camera to no light (a so-called "dark frame"), and by aligning the images so that when superimposed the stars and other features register.
If your own computer will run Java, then you may load ImageJ or run it from the web site. It is already installed on the computers in the astronomy lab. To access ImageJ from your own computer, use this link to our servers:
Select "Download ImageJ for your own computer". We have a version that has additional features for astronomy, but you won't need those for this activity.
Once you have the software running you'll see a window that looks like this:
Click on File in menu bar to select an image. Other entries offer different options for display and processing. The best way to learn what they can do is to try them out once you have one or more images on the screen.
Load the images
Load the three images taken in visible light in the order R, G, and B:
- File -> Open -> ngc2070_R_ij.fits "R" is red
- File -> Open -> ngc2070_V_ij.fits "V" is the astronomer's visual or green
- File -> Open -> ngc2070_B_ij.fits "B" is blue
It's important to do them in this order because we will make a color image out of them, and the order determines which file becomes which color.
These will appear as 32-bit images, that is values stored in them can be from large negative to large positive numbers.
Run the cursor around and look at the values in the ImageJ control window and you'll see something like this
but it will change as you move the cursor around. The x and y are the coordinates of the pixel, and image is the value representing how much light fell on the image at that spot during the exposure. The numbers may be negative! Oddly that may happen because of how they are stored in the file. Just remember that it's all relative to the lowest possible value, which would be black if no light fell in that spot. For these images black reads -32768.
The first thing you should do, then, is to process the images to change all the numbers in them. Since there are abotu 18,000,000 values in all three images, it's good to know how to make the program do this almost instantly.
Select the "R" image by a mouse click on the top bar of the window.
Process -> Math -> Add -> Value: 32768 -> OK
Repeat for the other two windows.
Make a stack
Notice that we did this operation on each image, one by one. It's simpler to manage several images at once by placing them together in what is called a stack.
Convert all the images to one stack with this simple action
Images -> Stack -> Images to Stack -> OK
Now there is a slider at the bottom of the image display, and if you move it from left to right you select one of the three images. Use the lower slider to select the red image of the stack. Notice that as you move the slider to the right there are three positions, and the "R", "V", and "B" image names will appear sequentially in the label of the image window. Select the leftmost position of the slider to have the red image.
If the new image display range after the math operation makes everything white, then the image may seem to be empty. Just run the cursor around and you'll see that the value changes from place to place.
Image -> Adjust -> Window/Level -> Auto
on the red image. You can experiment with the sliders, but for a start simply let the software do its work with "Auto" which will adjust all three layers of the stack. You wil probably see some stars, but not much detail. The detail is in the low signal levels that are not bright enough on the screen to see.
At this point if you are happy with the result you may save the stack by using
File -> Save as -> Tiff and then enter a name that you will remember, perhaps mystackname.tif
You may load this file and be back at this step instantly should something go wrong later.
Make a color composite
The smallest value in all three images should be around 0, the largest probably less than 32767. A bright star might be 16000 or so, but the nebula that is hidden in this image is only a few 100. If we used a scale of 0 to 255 with the star as 255, then the nebula would be around 255 * 100/16000 = 2. You would not see it. That's what happens on the display you are looking at. It takes a value from 0 to 255 and turns that into a brightness on the screen. At each element you see on the screen there are three numbers from 0 to 255 that tell the display how much red, green, and blue light to show.
Let's make a color composite image so that we can work with this and see the colors.
Image -> Color -> Make composite
The first image will be red, the second green and the third blue. You'll see the color composite of all three on the screen. Each layer has its full range of data, but what you see is limited by the screen's display to a range from to 255 values.
You should also see a "Channels Tool" on the screen that will allow you to turn off the effects of one or more layers. For now, keep them all on. Use the bottom slider to be sure you have the first layer selected.
Image -> Adjust -> Window/Level -> Set
Window Center: 500 Window Width: 1000
This means that values from 0 to 999 will be in the range from black to fully "on" on the screen. The bright parts of the image will probably look red.
Now select green "V" image and do this again, and then the blue "B" image.
The composite image you see will now probably look yellow. Much of the faint detail will be visible, but many bright stars will be white.
Modify the color
The remaining (difficult and arty) step is to get a color balance that you think is reasonable.
The camera is more sensitive to red light than it is to blue light (as is your eye), and slightly more sensitive to red than green. Your eye is more sensitive to green than to red or blue.
You can compensate for the lower sensitive for blue by increasing its importance in the final image. Select the blue (right) layer with the lower slider and set its image levels to something like this
Image -> Adjust -> Window/Level -> Set
Window Center: 100 Window Width: 200
Then experiment with the green and red to see if there is a combination that makes the nebula look white with a green cast.
As a trial you might try
Red: 350/750 Green: 300/600 Blue: 100/200
If you get something you like, save it as a tif file with a unique name. That way you can recover it later if you need to.
You may also save a jpg image that you can email, display or modify by saving as a jpg:
File -> Save as -> Jpeg
Make fine detail visible
Lastly you can process the composite to create effects to highlight structure. When an image is masked, you replace selected pixels in the image with any value you want. With unsharp masking, an image is intentionally altered to blur it and remove �ne detail. This fuzzy image is then subtracted from the original to reduce the influence of coarse structure and leave the detail of the original in an enhanced final image. Let's try this trick with ImageJ and our color image of the Tarantula Nebula.
Start with the last saved tif, because the next step will destroy the intermediate image.
Process -> Filters -> Unsharp Mask
Radius: 1 pixel
Mask Weight 0.6
will gently highlight the detail. It also makes noise more apparent, so while larger values are useful on some images, this is about as much as tolerable on the Tarantula example.
But there are other tricks! Use a larger unsharp mask radius, and then try a little "Gaussian blur". It gets very interesting. Be creative, and look for a display that seems reasonable and shows features in the nebula.
1. Save the image as a jpg file. You will need to submit it for credit for this activity.
Compare to the sky
Change the orientation of the image
When a camera is attached to a telescope it may be rotated around in almost any direction. We'll see too that as a telescope looks in different directions in the sky, the image may have a different orientation on the camera's detector. Add the complication that either optically or in how the data are stored the image may be inverted top to bottom and/or left to right. Let's see if we can figure out what the orientation of the image you have made actually is, and then modify the image so that north is up and west is to the right, as it would appear in the sky.
Exit ImageJ if it is still running, start it again, and load the processed color jpg image you saved from your work. In the ImageJ menu bar there is an entry Image, and under that Transform, which leads to Flip and Rotate options that you will use. First, however we need to see what this nebula looks like in the Digital Sky Survey that is a reference archive of the whole sky. One way you can access this through Sky-Map with the web site
Once you are in that site, enter Tarantula in the search box and you'll see an image of the nebula in the Large Magellanic Cloud. Compare that you your image and see if you can figure out how your image must be transformed to match the north up and west to the right standard.
Alternatively, you have more control in the display if you use Aladin. Use our gateway to Aladin
and select the option "Run the Aladin Sky Atlas applet in your browser", or if you already have it installed on your computer you may run it without needing the browser. After it has started, enter Tarantula in the search box and Aladin should load a color version of the Digital Sky Survey. This will be roughly on the same scale as your image. The color version is over saturated and may be hard to compare with your short exposure image. Instead, now click the "DSS" button that will load a single gray scale blue image. At this point you will probably start to recognize the features.
2. How must you transform your image (flip and/or rotate) to make it match the image of the DSS with north up and west to the right?
The Tarantula Nebula is about 170,000 light years away, in another galaxy. It's as far as our telescopes can pick out individual stars at birth, and at that mostly the brightest ones. You'll notice some stars in the image are very red. These are most likely red giants, massive stars that have already used their supply of hydrogen in their core, and are evolving toward becoming a supernova.
There is an image of the Tarantula taken with a 1.5 meter telescope of the European Southern Observatory on their website that is also worth comparing to yours. | 0.846611 | 3.639579 |
I had had enough of calling telephone numbers on hand-written memos. There was a strange eddy in the stream of cars
November 5, 2013 § Leave a comment
There is no air in space, and there cannot be sound without air. So what did NASA researchers mean when they recently stated that they had detected “interstellar music” which provided strong evidence that Voyager 1 had left the magnetic bubble surrounding the sun and planets known as the heliosphere?
That “interstellar music” is actually plasma waves detected by the probe’s Plasma Wave Science Instrument. As University of Iowa professor Don Gurnett, a space physicist and the chief investigator overseeing the Plasma Wave Science Instrument, explained during a September press conference, the instrument does not actually detect sound.
Instead, it detected electron waves in the plasma (ionized gas) which Voyager traveled through. While those plasma waves cannot be detected by the human ear, they occur at audio frequencies between a few hundred and a few thousand hertz, Gurnett explained. For that reason, he and his colleagues are able to listen to the data through a loudspeaker, determining the density of the gas surrounding the spacecraft through the pitch and frequency.
Gurnett played some of the plasma wave data for those in attendance at the September press conference, explaining that they indicated that the US space agency’s probe had left the heliosphere, which is essentially the sun’s magnetic field expanded to massive proportions by the solar wind. NASA officials have been waiting for the Voyager probes to exit the heliosphere for decades, and apparently Voyager 1 did so months before they realized it.
“It took almost a year for NASA to realize the breakthrough had occurred,” the US space agency said. “The reason is due to the slow cadence of transmissions from the distant spacecraft. Data stored on old-fashioned tape recorders are played back at three to six month intervals. Then it takes more time to process the readings. Gurnett recalls the thrill of discovery when some months-old data … reached his desk in the summer of 2013.”
He said that the sounds conveyed by the data conclusively demonstrated that Voyager 1 “had made the crossing.” While the probe was within the heliosphere, the tones detected by the Plasma Wave Science Instrument were low (approximately 300 hertz). Those sounds are typical of plasma waves coursing through solar wind.
Outside the heliosphere, the frequency rose to a higher pitch (between two and 3 kilohertz), corresponding to the denser gas located in the interstellar medium. Thus far, NASA said that Voyager 1 has only recorded two outbursts of this so-called “interstellar plasma music” – one that took place in October-November of 2012, and another which occurred in April-May of 2013. Both incidents were excited by solar activity. listen
CHARACTERS: Angela Genusa after Gertrude Stein
October 1, 2013 § Leave a comment
This is our best estimate for the number of potentially life-bearing worlds among the planets spotted by Kepler. But we’re missing much of the picture.
Kepler could spot only planets that passed between their parent stars and the telescope’s viewpoint – even a slight tilt in a planet’s orbit could make it invisible to the telescope. And the farther out a planet orbits, the more likely it was to be missed.
After extrapolating for all the missing worlds, Kepler’s field of view becomes dense with planets that may be like Earth.
Now consider this: Kepler observed just 0.28 per cent of the sky. And the telescope was able to peer out to only 3000 light years away, studying less than 5 per cent of the stars in its field of view. So how many Earths might really be out there? read more
PHOTOGRAPH: Bob Mazzer
Unpleasant? Strange. I’ve been told I have a very winning personality. The very best shoe clerk the store ever had
April 22, 2013 § Leave a comment
NASA’s Kepler mission has been hunting for worlds beyond our solar system for a little over four years now, and it’s been enormously successful. In that time, it’s spotted literally thousands of planetary candidates. Today, three distant worlds – dubbed Kepler-62f, Kepler-62e, and Kepler-69c – have achieved planetary confirmation, while joining an elite cadre of so-called habitable planets.
Kepler-62f and 62e possess radii just 1.4- and 1.6-times that of Earth’s, respectively, and orbit a star some 1,200 light years away, along with three other newly discovered planets. Kepler-69c, on the other hand, has a radius 1.7-times that of Earth, and orbits a star around 2,700 light years distant from our own. Together, the three newly discovered worlds have become the second, third, and fourth known bodies to wear the badge of “Earth-like, habitable zone planet.”…
“Kepler-62e probably has a very cloudy sky and is warm and humid all the way to the polar regions,” said co-author Dimitar Sasselov in a statement. “Kepler-62f would be cooler, but still potentially life-friendly.”
The pair belong to a five-planet system that includes 62d, 62c and 62b. These latter three planets vary in size, but orbit far too close to the system’s parent star to have any chance of harboring water or life.
“There may be life [on 62f and 62e], but could it be technology-based like ours? Life on these worlds would be under water with no easy access to metals, to electricity, or fire for metallurgy,” said lead author Lisa Kaltenegger in a statement.
“Nonetheless, these worlds will still be beautiful blue planets circling an orange star — and maybe life’s inventiveness to get to a technology stage will surprise us.” read more
PHOTOGRAPH: Patrick Joust
I’ve done boring jobs. I’ve worked in abattoirs stunning pigs and musicians and by the end of the day your back aches
October 19, 2012 § Leave a comment
One historical irony of this transition from the intensive, state-coordinated investment in these grand projects (with their significant blue-sky R&D components) to our current model (with its emphasis on “results,” i.e., profitable applications) is the extent to which the current crop of profitable technologies came out of that previous era of state development.
Rather than a mystical substance exuded through the pores of entrepreneurial ubermenschen, like Steve Jobs, most of the actual innovations that have driven capitalist profitability over the last several decades—including computerization and the internet—were first developed through research intensive, collective state projects, like NASA or DARPA.
Entrepreneurial “innovation” in our neoliberal period could be likened to a process of enclosure, whereby, in John Gulick’s words, corporate capitalists and a reconfigured neoliberal capitalist state commodify and reapportion already existing technical infrastructure and cultural wealth, “rather than creating anything new.” Leigh Philips details these more recent uses of space technology in “Put Whitey Back On The Moon,” in the process of advocating a return to manned space exploration as part of a comprehensively social democratic program that includes “guaranteed incomes, well-funded pensions, a transformation to a low-carbon (or even carbon-negative) economy, and investment in space exploration.”
In other words, rather than ceding the utopian legacy of space travel to the likes of Newt Gingrich, while offering a standard neoliberal “austerian” justification for such a rejection, leftists should wholeheartedly embrace the old dream of modernity. The specter of communism, in interstellar form, haunts this call.
Communism put human beings in space. The Moon landing was the Soviets’ greatest accomplishment: a quip that transcends its most immediate nationalist point of reference, as evinced—Newt Gingrich aside—in the American right-wing’s longstanding antipathy toward the space program, or “big government” in space (unless it’s say Ronald Reagan touting a Star Wars-style space weapons program run by conservatives’ command economy of choice). read more
PHOTOGRAPH: Diane Arbus | 0.896487 | 3.302524 |
On Saturn’s moon Titan, plentiful lakeside views, but with liquid methane
17 April, 2019, 7:15 pm
WASHINGTON (Reuters) – Scientists on Monday provided the most comprehensive look to date at one of the solar system’s most exotic features: prime lakeside property in the northern polar region of Saturn’s moon Titan – if you like lakes made of stuff like liquid methane.
Using data obtained by NASA’s Cassini spacecraft before that mission ended in 2017 with a deliberate plunge into Saturn, the scientists found that some of frigid Titan’s lakes of liquid hydrocarbons in this region are surprisingly deep while others may be shallow and seasonal.
Titan and Earth are the solar system’s two places with standing bodies of liquid on the surface. Titan boasts lakes, rivers and seas of hydrocarbons: compounds of hydrogen and carbon like those that are the main components of petroleum and natural gas.
The researchers described landforms akin to mesas towering above the nearby landscape, topped with liquid lakes more than 300 feet (100 meters) deep comprised mainly of methane. The scientists suspect the lakes formed when surrounding bedrock chemically dissolved and collapsed, a process that occurs with a certain type of lake on Earth.
The scientists also described “phantom lakes” that during wintertime appeared to be wide but shallow ponds – perhaps only a few inches (cm) deep – but evaporated or drained into the surface by springtime, a process taking seven years on Titan.
The findings represented further evidence about Titan’s hydrological cycle, with liquid hydrocarbons raining down from clouds, flowing across its surface and evaporating back into the sky. This is comparable to Earth’s water cycle.
Because of Titan’s complex chemistry and distinctive environments, scientists suspect it potentially could harbor life, in particular in its subsurface ocean of water, but possibly in the surface bodies of liquid hydrocarbons.
“Titan is a very fascinating object in the solar system, and every time we look carefully at the data we find out something new,” California Institute of Technology planetary scientist Marco Mastrogiuseppe said.
Titan, with a diameter of 3,200 miles (5,150 km), is the solar system’s second largest moon, behind only Jupiter’s Ganymede. It is bigger than the planet Mercury.
“Titan is the most Earth-like body in the solar system. It has lakes, canyons, rivers, dune fields of organic sand particles about the same size as silica sand grains on Earth,” Johns Hopkins University Applied Physics Laboratory planetary scientist Shannon MacKenzie said.
The research was published in the journal Nature Astronomy. | 0.861572 | 3.542498 |
Back in May 2008 a New Scientist article outlined a NASA Review that almost meant the end for Gravity Probe B, a project conceived in the 1960s to measure how the Earth warps the fabric of nearby space-time, and if it did indeed do so.
Imagine space-time as a large piece of fabric. If you imagine a ball placed on that fabric, this can be thought of as the geodetic effect – the fabric bending around the ball.
Now, consider the ball as being slightly-sticky. If you spin that ball, the fabric will be “dragged” along with the ball, this twisting of the space-time can be considered “Frame-Dragging“.
Einstein theorized that because our Sun warps the space-time surrounding it, the objects around it travel in a curved line (a circle). It is this theory that explains why Earth orbits the Sun. This distortion was first measured in 1919 by Sir Arthur Eddington (and his collaborators) during a total solar eclipse as they noted the position of stars passing near the Sun, but no one has ever measured this effect for the Earth.
Enter Gravity Probe B.
GP-B had two goals:
- Demonstrate that Earth has the hypothesized geodetic effect: The warping of Space & Time around a gravitational body; and
- Demonstrate the amount of Frame-Dragging caused by the Earth: The amount a spinning object pulls space and time with it as it rotates
Gravity probe B’s total cost was around US$750 million and was another project that almost never was because of dwindling funding for scientific investigation. Back in 2008, 15 experts commissioned by NASA doubted further analysis of the GP-B results would produce any significant new information, and as such they recommended that Gravity Probe B receive no additional funding after September 2008.
Despite this, GP-B secured alternative funding from King Abdulaziz City of Science and Technology. Thanks to that funding, the Stanford-based analysis group and NASA announced on May 4, 2011 that the data from GP-B confirmed the two predictions of Albert Einstein’s general theory of relativity.
NASA’s Gravity Probe B (GP-B) mission has confirmed two key predictions derived from Albert Einstein’s general theory of relativity, which the spacecraft was designed to test. The experiment, launched in 2004, used four ultra-precise gyroscopes to measure the hypothesized geodetic effect, the warping of space and time around a gravitational body, and frame-dragging, the amount a spinning object pulls space and time with it as it rotates. GP-B determined both effects with unprecedented precision by pointing at a single star, IM Pegasi, while in a polar orbit around Earth.
– NASA’s GP-B Mission Page
It may not seem like much up front, but this concludes one of the longest-running projects operated by NASA, and as a result of decades of research has led to many technological marvels.
GP-B awesome array of groundbreaking technologies were applied to NASA’s Cosmic Background Explorer mission, which accurately determined the universe’s background radiation – The measurement that is the underpinning of the big-bang theory, and led to the Nobel Prize for NASA physicist John Mather.
Additionally, Gravity Probe B has led to advancements in Control Technologies:
- Aerodynamic Drag
- Magnetic Fields
- Thermal Variations
- and GPS Technologies allowing planes to land unaided. | 0.902367 | 3.813342 |
Astronomers have captured one of the most detailed views of a young star taken to date, and revealed an unexpected companion in orbit around it.
While observing the young star, astronomers led by Dr John Ilee from the University of Leeds discovered it was not in fact one star, but two.
The main object, referred to as MM 1a, is a young massive star surrounded by a rotating disc of gas and dust that was the focus of the scientists original investigation.
A faint object, MM 1b, was detected just beyond the disc in orbit around MM 1a. The team believe this is one of the first examples of a fragmented disc to be detected around a massive young star.
Stars form within large clouds of gas and dust in interstellar space, said Dr Ilee, from the School of Physics and Astronomy at Leeds.
When these clouds collapse under gravity, they begin to rotate faster, forming a disc around them. In low mass stars like our Sun, it is in these discs that planets can form.
In this case, the star and disc we have observed is so massive that, rather than witnessing a planet forming in the disc, we are seeing another star being born.
Artists impression of the disc of dust and gas surrounding the massive protostar MM 1a, with its companion MM 1b forming in the outer regions. Credit: J. D. Ilee, University of Leeds
Weighing the stars
By measuring the amount of radiation emitted by the dust, and subtle shifts in the frequency of light emitted by the gas, the researchers were able to calculate the mass of MM 1a and MM 1b.
Their work, published today in the Astrophysical Journal Letters, found MM 1a weighs 40 times the mass of our Sun. The smaller orbiting star MM 1b was calculated to weigh less than half the mass of our Sun.
Observation of the dust emission (green) and the gas around MM1a (red is receding gas, blue is approaching gas). MM1b is seen orbiting in the lower left. Credit: ALMA (ESO/NAOJ/NRAO); JD Ilee, University of Leeds
Many older massive stars are found with nearby companions, added Dr Ilee. But binary stars are often very equal in mass, and so likely formed together as siblings. Finding a young binary system with a mass ratio of 80:1 is very unusual, and suggests an entirely different formation process for both objects.
An unstable beginning
The favoured formation process for MM 1b occurs in the outer regions of cold, massive discs. These gravitationally unstable discs are unable to hold themselves up against the pull of their own gravity, collapsing into one or more fragments.
Dr Duncan Forgan, a co-author from the Centre for Exoplanet Science at the University of St Andrews, added: "I've spent most of my career simulating this process to form giant planets around stars like our Sun. To actually see it forming something as large as a star is really exciting.
The researchers note that newly-discovered young star MM 1b could also be surrounded by its own circumstellar disc, which may have the potential to form planets of its own but it will need to be quick.
Dr Ilee added: Stars as massive as MM 1a only live for around a million years before exploding as powerful supernovae, so while MM 1b may have the potential to form its own planetary system in the future, it wont be around for long.
Imaging objects thousands of light years away
The astronomers made this surprising discovery by using a unique new instrument situated high in the Chilean desert the Atacama Large Millimetre/submillimetre Array (ALMA).
The Atacama Large Millimetre/submillimetre Array (ALMA). Credit: ALMA
Using the 66 individual dishes of ALMA together in a process called interferometry, the astronomers were able to simulate the power of a single telescope nearly 4km across, allowing them to image the material surrounding the young stars for the first time.
The team have been granted additional observing time with ALMA to further characterise these exciting stellar systems in 2019. The upcoming observations will simulate a telescope that is 16km across comparable to the area inside of the ring-road surrounding Leeds.
Top image: The Atacama Large Millimetre/submillimetre Array (ALMA). Credit: ALMA
The paper: G11.92-0.61 MM1: A Fragmented Keplerian Disk Surrounding a Proto-O Star is published in the Astrophysical Journal Letters 14 December 2018.
For any additional information please contact University of Leeds Media Relations Officer Anna Harrison on [email protected] or +44 (0)113 343 4196. | 0.932249 | 4.020642 |
Space observations are poised to reveal more about the centre of one of the Universe’s most enigmatic objects
A new x-ray survey of distant galaxies suggests that the universe is expanding unevenly
The disk of gas and stars resembles our own Milky Way but somehow formed when the universe was only about 10 percent of its current age
Physicist Brian Keating talks about his book Losing the Nobel Prize: A Story of Cosmology, Ambition, and the Perils of Science’s Highest Honor.
Using gravitational waves to approximate pi, physicists see no problem with Einstein’s theory
The discrepancy could be a statistical fluke—or a sign that physicists will need to revise the standard model of cosmology
Unified theory describes formation of huge, mysterious waves
An astrophysicist traces genealogy and art history to discover the origin of the famous motto
The iconoclastic researcher and entrepreneur wants more attention for his big ideas. But so far researchers are less than receptive
Astrophysicist and author Mario Livio talks about his latest book, Galileo: And the Science Deniers, and how the legendary scientist’s battles are still relevant today.
The surprise detection of a radio burst from a neutron star in our galaxy might reveal the origin of a bigger cosmological phenomenon
Mysterious patterns in orbits of small bodies in the outer solar system could arise from the gravity of a massive disk of icy debris rather than an undiscovered giant world
Originally published in August 1863
Researchers used the light reflecting off the wrapper to build an image of its surroundings
Guest host W. Wayt Gibbs talks with Jason Wright, a professor of astronomy and astrophysics at Pennsylvania State University’s Center for Exoplanets and Habitable Worlds, about what’s known as the Fermi paradox: In a universe of trillions of planets, where is everybody?...
Originally published in July 1898
Originally published in March 1951
New evidence from neutrinos points to one of several theories about why the cosmos is made of matter and not antimatter
An unprecedented signal from unevenly sized objects gives astronomers rare insight into how black holes spin | 0.813196 | 3.549641 |
Find your way around the night sky! Below is a free sky map for March 2016 as well as a printable version, courtesy of astronomer Jeff DeTray.
Sky Map for March 2016
Each month, Jeff DeTray’s Sky Maps provides a sky map which highlights beautiful events in the evening sky—stars, constellations, planets, conjunctions with the Moon, meteor showers, and other amazing celestial objects. Follow more of Jeff’s sky adventures at AstronomyBoy.com.
Click-and-Print Sky Map
Just click here or on the image below to open the printable map—then bring outside!
Sky Map Highlights: March 2016
Saturn and Mars, Together at Dawn
Saturn, the Ringed Planet, and Mars, the Red Planet, are together in the early morning sky for the whole month of March. Go outside an hour or so before sunrise and look to the south to catch the show.
The two planets are easy to spot low in the south. As shown on this month’s map, the planets form an upside-down triangle with the bright star Antares. All three objects are about the same apparent brightness, but their colors differ. Antares and Mars both have a slightly orange hue and have been compared to one another for thousands of years. In fact, Antares means “equal to Mars” in ancient Greek. In contrast, Saturn appears to be nearly pure white in color.
The Brightness of a Planet
Although the three objects appear to be approximately the same brightness, things aren’t quite what they seem. There is a difference between apparent brightness and actual brightness. That difference is explained by distance.
- Saturn is much farther from us than Mars—currently more than ten times as far: 913,000,000 miles versus 87,000,000 miles. All things being equal, Saturn would be far dimmer than Mars. However, things are not equal. Though Saturn is more distant, it is also much larger than Mars. Being larger, it reflects more sunlight and therefore appears just as bright as Mars.
What about the star Antares? Like all the stars in the sky (except our Sun), Antares is unimaginably far away! Compared to Antares, Mars and Saturn are in our backyard.
- Antares’ distance is approximately 3,233,000,000,000,000 miles. That’s more than 3 quadrillion miles, or in astronomer-speak 550 light-years. Antares is three-and-a-half million times more distant than Saturn. Despite that extreme distance, Antares appears to be about the same brightness as our close neighbors, Saturn and Mars. The lesson here: Stars are really, really bright!
The relative proximity of Mars and Saturn means both planets are near enough that we have managed to send unmanned space probes to explore them. When you look at Saturn and Mars in the pre-dawn sky this month, consider how amazing it is that spacecraft from Earth are exploring their secrets right now.
MARCH 2016 Sky Map
Click here or on image below to enlarge (PDF)
Sky map produced using Chris Marriott’s Skymap Pro
TAP for Mars missions
Dozens of missions to Mars have been attempted, about half of which successfully reached the Red Planet. The first spacecraft to explore Mars was NASA’s Mariner 4 in 1965. Mariner 4 flew by Mars and transmitted 21 low-resolution photos of the surface. The first spacecraft to land on Mars were NASA’s Viking 1 and Viking 2 in 1976. These early missions put an end to centuries of speculation that Mars might harbor an alien civilization.
At present, there are seven spacecraft on and around Mars. Two rovers, Opportunity and Curiosity, are busily exploring the Martian surface, while five other craft collect data from orbit.
Photo credit: NASA
TAP for Saturn missions
Although it’s in our general neighborhood, Saturn is much farther away from Earth than Mars and is therefore more difficult to reach. So far, only three space missions have explored the Saturn system. The first was Pioneer 11, which flew by Saturn in 1979, sending back medium-resolution photos and information about the rings. Voyagers 1 and 2 passed by Saturn in 1980 and 1981. These fly-by missions provided us with the first high-resolution images of Saturn and its fabulous rings.
Photo credit: NASA
In 2004, the Cassini spacecraft arrived at Saturn and went into orbit around the planet. Cassini has been sending back photos and other data ever since and will continue to explore Saturn for at least another year.
See our Sky Watch page for more highlights of the monthly sky, courtesy of The Old Farmer’s Almanac. | 0.82294 | 3.422015 |
In five years or so, NASA will begin initiating the launch process for its Asteroid Redirect Mission, or ARM. It’s one of those scientific endeavors that has a clear goal, yet an unclear purpose. The goal of the mission is to send a robotic probe off to a near-Earth asteroid, find a small boulder somewhere between one and two dozen feet in diameter sitting on the surface of the asteroid, pick it up, and transfer it to the moon where it can be placed in a stable lunar orbit. In effect, it turns the asteroid into a kind of natural satellite.
Why, exactly, does NASA want to do something like this? No one is completely sure. ARM is meant to be part of a slew of missions to test out the capabilities of the Orion spacecraft and NASA’s new Space Launch System. Together, both systems will help NASA conduct more and more crewed operations into the farther reaches of space, eventually culminating in successfully getting astronauts to Mars before 2040.
As I’ve written before, there’s a good chance the purpose of ARM is to simply prove that it’s possible to use robotic technology to haul a big payload off an asteroid (or other object) and successfully move into another moon or planet’s orbit. This could be critical for several reasons. One is that it helps establish orbits as a form of possible storage space that humans could access above the ground, allowing rocket launches off the ground to be conducted with less fuel and energy costs.
Another reason with bigger ramifications is that asteroids themselves could play an important role as reservoirs of natural resources like certain metals and even water. The SPACE Act of 2015 sets the stage for private companies to begin exploiting those objects and keeping ownership over what they find. Imagine we’re able to improve spaceflight technology to the point where water or other elements commonly found in space can act as a propellent. Suddenly, any celestial rock that can be mined becomes a miniature oil field, usher in a new interstellar gold rush for precious resources every single nook and cranny in the solar system. Having an asteroid
A 2011 proposal for an asteroid capture system discusses how the asteroid Apophis contains significant amends of iron, water, oxygen, and other materials that would be extremely useful in space — enough to power about 150 five-gigawatt solar power satellites. Turning such a rock into a satellite could be a great way to ensure access to these resources when they are needed — not to mention it ensures the asteroid has no chance of hitting the Earth or other objects important to human projects.
Okay, so turning an asteroid into a satellite has plenty of potential upsides. The real question is: Can we realistically accomplish something like this?
Hell no. At least, not right now. ARM is the first step towards helping us get there, but a projected boulder for this mission would only be around 500 tons. By comparison, Apophis from the previously mentioned proposal comes in at a mass of 27 megatons — or roughly 27 million tons. Yikes.
Another problem is that many asteroids appear to actually be big piles of rubble — perhaps encased in a solid rock casing, but with insides as good as coarse sand.
But what if these were no longer obstacles? What if big sizes and masses weren’t impediments, and we found an easy way to differentiate the solid asteroids from the rubbly ones?
We’d have to find a way to apply thrust to the asteroid. We could dock on the surface of the asteroid and push it in a transitional way (with thrusters), but asteroid rotation and microgravity could make things problematic. Something like a gravity tractor could be used to gently nudge an asteroid over to a desired destination, but this would be a much much slower process.
The most efficient method would probably be to wait till the Earth (or another planet) is in a position to help slingshot an asteroid’s orbit in such a way as to bring it close to entering the planet’s gravitational field. Then, humans just have to come in and apply a more minimal type of intervention to make sure the asteroid safety enters the planet’s orbit. This would probably be through some kind of massive spacecraft that acts like a tugboat for outer space objects.
If the asteroid was stable enough, humans could theoretically start placing different kinds of installations on the surface or even building right on it. The kinds of technology that could most take advantage of an asteroid-satellite environment are probably massive communications arrays or defense systems. And let’s not forget the potential for full-scale mining operations to take off.
This is still an incredibly long ways away from what’s even remotely possible. But if humans really are serious about space travel, we’re going to need to start considering how to really take advantage of the resources at our disposal. Nothing should be off limits — least of all if there’s water to collect. | 0.837612 | 3.515106 |
Visitors to the Suffolk County Vanderbilt Museum’s Reichert Planetarium can now view the Sun through a new solar telescope.
The Planetarium has just installed a Lunt Solar Systems hydrogen-alpha solar telescope in the Observatory – for daytime observation of the Sun.
Dave Bush, the Planetarium’s technical and production coordinator, and an astronomy educator, said the solar telescope is mounted “piggy back” onto the 16-inch Meade reflecting telescope in order to track the Sun across the sky.
“The refractor-style telescope with its 80-milimeter optical aperture gives us sharp detail and contrast of features on the surface and the limb, or edge, of the Sun,” he said. “This telescope allows us to see prominences, flares, super granulation, filaments, and active regions.”
Bush explained that hydrogen-alpha light is emitted by the hydrogen atoms that make up the majority of the Sun’s composition. When electrons within the hydrogen atoms absorb energy and rise to a higher energy level then fall back to their original orbits, light is emitted at a particular wavelength that can be seen with the specialized telescope.”
“Typically, telescopic views of objects in outer space rarely change before our eyes in real-time,” Bush said. “However, on a day when the Sun is particularly active we can watch features on the Sun evolve before our eyes while looking through an H-alpha telescope!
“The sun is dynamic and alive. It changes daily, and rotates.”
Bush explained the solar features in the picture at left, shot by photographer Alan Friedman:
- The wisps of white curling off the upper left curve of the Sun are prominences, or arcs of gas that erupt from the surface. Sometimes the loops extend thousands of miles into space.
- The lighter spots and streaks are called plages, the French word for beaches, and are, appropriately hot spots or bright emissions caused by emerging flux regions associated with the magnetic field of the Sun.
- The tiny hair-like lines that extend from the surface are spicules. These are jets of hot gas that can rise up to 6,000 miles high. Most last only 15 minutes before morphing into new spicules.
- The dark spots are sun spots, which are cooler areas of the surface caused by the suppression of convection cells due to the Sun’s strong magnetic field.
The Sun is 93 million miles from Earth, and its size is almost beyond human comprehension – 1.3 million Earths could fit inside the Sun.
The solar telescope is available for viewing on a limited schedule, on clear days. (The Sun is not observable on cloudy or rainy days.) | 0.809986 | 3.705142 |
Unlike most of the planets, which follow almost exactly circular orbits around the Sun only varying in their distance from the Sun by a few percent, Mercury has a significantly elliptical orbit.
Its distance from the Sun varies between 0.307 AU at perihelion (closest approach to the Sun), and 0.467 AU at aphelion (furthest recess from the Sun). This variation, of over 50%, means that its surface receives over twice as much energy from the Sun at perihelion as compared to aphelion.
However, this makes little difference to Mercury's telescopic appearance, since little if any detail on its surface can be resolved by ground-based telescopes. Although its changing seasons have an incredible effect upon its surface temperatures, there is little change that is visible to amateur observers.
The exact position of Mercury at the moment it passes aphelion will be:
|Object||Right Ascension||Declination||Constellation||Angular Size|
The coordinates above are given in J2000.0.
|The sky on 08 December 2014|
16 days old
All times shown in EST.
Never attempt to point a pair of binoculars or a telescope at an object close to the Sun. Doing so may result in immediate and permanent blindness.
The circumstances of this event were computed using the DE405 planetary ephemeris published by the Jet Propulsion Laboratory (JPL).
This event was automatically generated by searching the ephemeris for planetary alignments which are of interest to amateur astronomers, and the text above was generated based on an estimate of your location.
|08 Dec 2014||– Mercury at aphelion|
|14 Jan 2015||– Mercury at greatest elongation east|
|16 Jan 2015||– Mercury at dichotomy|
|16 Jan 2015||– Mercury reaches highest point in evening sky| | 0.914464 | 3.457915 |
The PAMELA experiment represents one of the most important steps of an extensive space program dedicated to antimatter detection in space, research of dark matter signals, study of the nuclear and isotopic components of cosmic rays, monitoring of the solar activity, measurement of the radiation environment around the Earth. Many balloon-borne experiments have been performed by the WiZard collaboration including USA, Italian, German and Swedish researchers, gathered since 1988 around Prof. Robert Golden who first discovered antiprotons in space. The experiments MASS 89, MASS 91, TS93, CAPRICE 94 and CAPRICE 98, utilizing typical detectors of elementary particle physics, have provided important results on the antiparticle-particle ratio and on the energy spectra from 1 GeV to 50 GeV for antiprotons, and from 500 MeV to 20 GeV for positrons. Also relevant have been the measurements of primary proton and helium spectra, and those of positive and negative muon fluxes at different atmospheric depths, important for solving the atmospheric neutrino puzzle. PAMELA is a part of the Russian-Italian Mission (RIM) research program defined in 1993. In the framework of this agreement, two satellite missions, NINA-1 and NINA-2, have been performed to study low energy solar and galactic cosmic rays. The two instruments were constituted of 32 planes of silicon sensor. NINA-1 flew as a “piggy back” of the Resurs-01 n.4 Russian satellite in the years 1998-1999, while NINA-2 was launched in orbit in July 2000 on board of the Italian satellite MITA and in operation during the years 2000-2001. | 0.847951 | 3.040847 |
The Study of Light Variability in a Sample of Proto-Planetary Nebulae
Dr. Bruce Hrivnak
Arts and Sciences
We are studying the light variability of a subclass of evolved stars called proto-planetary nebulae. The proto-planetary nebulae phase is a stage near the end of the life cycle of stars like our sun as they evolve over time. Our goal is to determine the period of pulsation of each star, which can eventually be used to determine the size, mass, and density of the star. Using the 0.4 meter telescope and CCD detector located at the VU observatory, our group took many images of these objects over the course of the summer on every clear night. These images add another season of data to this project which began at VU in 2008. The computer software Period04 assists in finding periods within the full data set spanning from 2008 to 2014. With this program we have found periodicity in 5 of the ten stars assigned to us to analyze. Using these results we have been able to make some comparisons between some of the periods found in a star; for example, in IRAS20056, the first two periods in the R filter have a ratio of 2:1. There are also some stars whose periodicities show potential for a binary companion, these stars being IRAS20056 and IRAS20094. We will present some of the light curves and the initial period findings. This research was funded by the National Science Foundation through the MSEED Program, and grants to Professor Hrivnak from the National Science Foundation and from NASA through the Indiana Space Grant Consortium.
Vance, Abigail, "The Study of Light Variability in a Sample of Proto-Planetary Nebulae" (2015). Symposium on Undergraduate Research and Creative Expression (SOURCE). 459. | 0.857733 | 3.124815 |
The search for life on Mars just got a lot more interesting. The odds are slim that Mars hosts life today. Still, a newly spotted lake near the Red Planet’s south pole ups the chances that scientists could find microbes living on Mars today.
For decades, when scientists looked at the dry and dusty planet, they focused on sites that might have supported life when Mars was warmer and wetter. But on July 25, researchers announced finding signs of a large lake of liquid water. It appears to be hiding beneath thick layers of ice near the Red Planet’s south pole. And it could provide a reservoir for salt-adapted organisms.
The increased possibility of life also changes the strategy of astrobiologists. They want to protect any existing extraterrestrials from being wiped out or overrun by species hitchhiking in on Earthly spacecraft.
Mars landers and rovers are carefully cleaned to avoid any possible contamination. And that was true even before there appeared to be “anything you’d even call a pond,” says Lisa Pratt. She’s an astrobiologist and NASA’s official planetary protection officer. “Now we have a report of a possible subglacial lake!” That, she notes, is “a major change in the kind of environment we’re trying to protect.”
So how does finding the lake change the quest for life on Mars?
First: Could anything really live in this lake?
It would be a tough territory for most Earthly microbes. Life on Earth fills every niche it can find, from cave crystals and arid deserts to sediments on the deep-ocean floor. But the low temperature cutoff for most life on Earth is around –40° Celsius (-40° Fahrenheit). The Martian ice sheet is about –68 °C (–76 °F). “It’s very cold — colder than any environment on Earth where biologists believe life [can live and reproduce],” Pratt says.
The lake does seem to contain plenty of water. But for the water to be liquid at such cold temperatures, it also must be extremely salty. “On Earth, these kinds of briny mixtures present significant challenges to living organisms,” says Jim Bell. He’s a planetary scientist at Arizona State University in Tempe and president of the Planetary Society.
Some bacteria on Earth seem to thrive even in extreme conditions. But even the so-called “extremophiles” (Ex-TREE-moh-fyles) “that can live in highly salty water might not be able to survive” in the cold, Martian lakes, he says.
But could Martians live there?
“Absolutely,” Pratt says.
If life arose on Mars at some point in its more life-friendly past, some of those organisms might have adapted to the Red Planet’s changing climate. These might have ended up finding the cold, salty water quite comfortable, she says. “This to me looks like an ideal refugia — a place where you could just hang out, maybe be dormant and wait for surface conditions to get better.”
What’s different about this lake versus other watery places where we hope to find life, like Saturn’s moon Enceladus?
For planetary explorers, Mars has one big advantage over the icy moons of Saturn and Jupiter: We’ve landed on it before. Getting to Mars would be a relatively quick journey. A spacecraft could reach there in four to 11 months. And the planet’s atmosphere makes landing much simpler than on the tiny, airless moons.
The big question for planetary protection is whether Mars’ lake has any contact with the planet’s surface. On Saturn’s moon Enceladus and possibly on Jupiter’s moon Europa, liquid water from a subsurface ocean sprays into space from cracks in the ice. Those plumes would make sampling the oceans relatively simple: A spacecraft could just catch some spray during a flyby. But the fact that water can get out also means that invading microbes can get in.
Even though no Mars spacecraft has landed near the suspected lake, global dust storms — like one currently raging on Mars — could carry in contamination from anywhere on the planet.
“So if [the lake is] real, let’s hope there’s no passageway into it,” Pratt says.
If there’s no way in or out, how can we see if anything lives there?
That is a problem. But it’s also not impossible to overcome.
To check the lake for signs of life, “you gotta drill,” explains Isaac Smith. He’s a planetary scientist in Lakewood, Colo., working for the Planetary Science Institute. Scientists have already probed similar under-ice lakes on Earth, such as Lake Whillans in Antarctica. In 2014, a U.S. team drilled through some 1.6 kilometers (1 mile) of ice. Each thimbleful of water they brought up contained roughly 130,000 living cells. In all, this water hosted 3,931 microbial species or groups of species.
Drilling on Mars would be even more technically challenging. It also could face opposition from the scientific community. “Like the subglacial lakes in Antarctica, [the Mars lake] would be considered an extraordinarily rare and special place,” Pratt says. “I expect there would be lots of resistance to drilling into it.”
But if we’re lucky, there could be a sign from above. Scientists have detected signs of seasonal variations in the amount of methane in the Martian atmosphere. This has suggested these variations might point to microbial life under the surface. The European Space Agency’s ExoMars Trace Gas Orbiter, which began taking data in April, is looking for more such methane.
“ExoMars could find a ‘smoking gun,’ so to say,” says Roberto Orosei. This planetary scientist works at the National Institute of Astrophysics in Bologna, Italy. He also was part of the team that just discovered the Martian lake. “Association of liquid water and methane in the atmosphere,” he says, “would be very, very exciting evidence of something going on on Mars.” | 0.873576 | 3.670583 |
Hair standing on end during a thunderstorm is a bad sign. It means lightning is on its way. On one faraway planet, though, static hair might be the least of your worries.
The planet is HAT-P-11b. It is an exoplanet — a planet far outside Earth’s solar system — some 124 light-years away. Scientists detected a surge of radio waves from the planet several years ago. Those waves could be caused by a barrage of lightning striking 530 times as often per square kilometer (0.4 square mile) as storms do in the United States.
This is the conclusion of Gabriella Hodosán of the University of St. Andrews in Scotland and her colleagues. They reported their finding April 23 in Monthly Notices of the Royal Astronomical Society.
In 2009, astronomers recorded radio waves coming from the HAT-P-11 system. The radio waves ceased when the planet slipped behind its star. That suggested the planet was the source of the signal. A second look in 2010 found no radio waves.
Scientists have detected lightning on planets closer to home, including Venus and Jupiter. But they have never before found lightning on a planet orbiting a star other than the sun.
HAT-P-11b is too close to its star for astronomers to see visible flashes of light. But an infrared telescope might pick up a stockpile of hydrogen cyanide created by such electrical discharges. | 0.83989 | 3.268328 |
These days we think of Giovanni Cassini in relation to Saturn, for obvious reasons, but the Italian astronomer (1625-1712) did a lot more than discovering the division in the rings of Saturn that would later bear his name. In addition to his studies of the Saturnian moons, Cassini shares credit for the discovery of Jupiter’s Great Red Spot, and in conjunction with Jean Richer, made parallax observations of Mars that allowed its distance to be determined in 1672.
But back to Jupiter, for in 1686 Cassini reported seeing a dark spot on the planet, one that from his description was roughly the size of the largest impact made by the Comet P/Shoemaker-Levy comet fragments in 1994. We’re dealing with crude telescopes and lack of corroborating information with Cassini’s observation, but Shoemaker-Levy left us with Hubble imagery when it struck the giant planet after breaking apart into more than twenty pieces enroute.
I mention Cassini’s early sighting because it’s possible he was also seeing the results of an impact, and that would be significant. Given what we know about asteroid and cometary impacts, the assumption has been that impacts with Jupiter should occur on a timescale of every few hundred to few thousand years. But they’re starting to mount up. Add to Cassini’s possible impact sighting an 1834 observation by the British astronomer George Airy, who reported a dark feature that was four times as large as the shadows cast by the Galilean moons.
And now, just sixteen years after Shoemaker-Levy, we have two more impacts, the first evidently the result of an asteroid rather than a comet. The differences between it and Shoemaker-Levy are instructive. The impact occurred on July 19, 2009, was spotted by Australian amateur Anthony Wesley and quickly followed up by observatories around the world and via the Hubble telescope. The impact site was elongated, indicating an object that descended at a shallower angle than the Shoemaker-Levy fragments, and a different direction of origin.
Image: Hubble image of Jupiter’s full disk taken July 23, 2009, revealing an elongated, dark spot at lower, right (inside the rectangular box). The photograph was taken four days after an amateur astronomer first spotted the scar. The unexpected blemish was created when an unknown object plunged into Jupiter and exploded, scattering debris into the giant planet’s cloud tops. The series of close-up images at right, taken between July 23, 2009 and Nov. 3, 2009, show the impact site rapidly disappearing. Jupiter’s winds also are spreading the debris into intricate swirls. Credit: NASA, ESA, M.H. Wong (University of California, Berkeley), H. B. Hammel (Space Science Institute, Boulder, Colo.), I. de Pater (University of California, Berkeley), and the Jupiter Impact Team.
Also telling is that while the 1994 impact showed a distinct halo around the site, evidently the result of fine dust rising from the cometary material, the 2009 impact showed no halo and left little contrast between the debris and Jupiter’s clouds. Scientists are interpreting this as evidence of a lack of lightweight particles, pointing to a solid impactor like an asteroid rather than a comet.
Wesley and fellow amateur Christopher Go, based in the Philippines, also lay claim to a June 3 impact this year, an event first noted by Wesley and confirmed by Go. Both caught the impact on video. This Ars Technica story has more, and a detailed breakdown of the events is offered in Emily Lakdawalla’s account for the Planetary Society. Follow-up observations may yield more information, but for now this video, with its one-second flash, makes it clear that Jupiter has pulled in another victim.
We can’t with certainty ascribe the 1686 and 1834 observations to impacts, but the fact that we now have three Jupiter strikes within fifteen years does raise the eyebrows. The 2009 impactor is thought to have been about 500 meters wide, probably having its origin in the Hilda family of asteroids that orbit near Jupiter. It’s chastening to hear that its strike created an event that was the equivalent of several thousand nuclear bombs exploding. Not as big as the largest Shoemaker-Levy impacts, but that fact in itself tells us that while Jupiter may do a good job cleaning out our system’s inner debris, one stray asteroid could do unthinkable damage on our planet’s surface.
The paper is Sánchez-Lavega et al., “The Impact of a Large Object on Jupiter in July 2009,” Astrophysical Journal Letters 715 (June, 2010), L155 (abstract). More on the 2010 impact as the investigation proceeds. | 0.872647 | 4.013854 |
While we continue to labor over the question of planets around Alpha Centauri A and B, Proxima Centauri — that tiny red dwarf with an unusually interesting planet in the habitable zone — remains a robust source of new work. It’s surely going to be an early target for whatever interstellar probes we eventually send, and is the presumptive first destination of Breakthrough Starshot. Now we have news of a possible second planet here, though well outside the habitable zone. Nonetheless, Proxima Centauri c, if it is there, commands the attention.
A new paper offers the results of continuing analysis of the radial velocity dataset that led to the discovery of Proxima b, work that reflects the labors of Mario Damasso and Fabio Del Sordo, who re-analyzed these data using an alternative treatment of stellar noise in 2017. Damasso and Del Sordo now present new evidence, working with, among others, Proxima Centauri b discoverer Guillem Anglada-Escudé, and incorporating astrometric data from the Gaia mission’s Data Release 2 (DR2). The result of the new analysis is a possible planet with an orbital period of 5.2 years and a minimum mass of 5.8 ± 1.9 times the mass of the Earth.
Image: This is Figure 5 from the paper. Caption: Outcomes of the combined analysis of the astrometric and RV datasets. Left: True mass of Proxima c versus the sine of the orbital inclination, as obtained from the astrometric simulations. The black line is the simulated exact solution, the blue dots represent the values derived from the Gaia astrometry alone, while the red dots are the values derived by combining the Gaia astrometry with the radial velocities. Right: Fractional deviation of the true mass (defined as the difference between the simulated and retrieved masses for Proxima c divided by the simulated value) versus sine of the orbital inclination. Credit: Damasso et al.
Remember that when dealing with radial velocity results, we can only draw conclusions on the minimum mass in question, as we don’t know how the system is inclined around the star. The researchers find that by analyzing the photometric data and spectroscopic results, they cannot explain the planetary signal through stellar activity, but they also argue that a good deal of follow-up work is needed through a variety of means. The paper notes, for example, that Proxima was observed with the Atacama Large Millimeter/submillimeter Array (ALMA) in 2017, with an unknown source detected at 1.6 AU. Is this evidence for Proxima c?
It’s quite an interesting question, and one that involves more than a new planet:
ALMA imaging could corroborate the existence of Proxima c if the secondary 1.3-mm source is confirmed: In this sense, ALMA follow-up observations will be essential. In (28), the possible existence of a cold dust belt at ∼30 AU, with inclination of 45°, is also mentioned. If Proxima c orbits on the same plane, its real mass would be mc = 8.2 M⊕
Image: Artist’s impression of dust belts around Proxima Centauri. Discovered in data from the Atacama Large Millimeter/submillimeter Array (ALMA) in Chile, the cold dust appears to be in a region between one to four times as far from Proxima Centauri as the Earth is from the Sun. The data also hint at the presence of an even cooler outer dust belt and may indicate the presence of an elaborate planetary system. These structures are similar to the much larger belts in the Solar System and are also expected to be made from particles of rock and ice that failed to form planets. Such belts may also prove useful in helping us investigate the presence of a possible second planet around this star. Credit: ESO / M. Kornmesser.
But Gaia astrometry is also crucial, for there is some evidence of an anomaly in Proxima’s tangential velocity that, if confirmed, would be compatible with the existence of a planet with a mass in the 10 to 20 Earth range, and a distance between 1 and 2 AU. Further work with Gaia data is clearly in the cards:
Given the target brightness and the expected minimum size of the astrometric signature…, Gaia alone should clearly detect the astrometric signal of the candidate planet at the end of the 5-year nominal mission, all the more so in case of a true inclination angle significantly less than 90°. Proxima is one of the very few stars in the Sun’s backyard for which Gaia alone might be sensitive to an intermediate separation planetary companion in the super-Earth mass regime.
A final consideration is that while the flux contrast between the hypothetical Proxima c and the parent star (depending on albedo, among other things) is beyond the capabilities of our current direct imaging technologies, the apparent separation of planet and star should be accessible to future high-contrast imaging instruments, perhaps the European Extremely Large Telescope, which the paper mentions along with other ground- and space-based instruments. So we have what the authors describe as ‘a very challenging target,’ but one with huge interest for astronomers continuing to characterize this closest of all stellar systems.
It seems premature to get too far into a discussion of how Proxima c formed, since we have yet to confirm it. However, the authors make the case that if it is there, this planet would challenge us to explain how it formed so far beyond the snowline, where super-Earths could take advantage of the accumulation of ices. Perhaps the protoplanetary disk here was warmer than we’ve assumed. In any case, the apparent circularity of the orbit and the absence of more massive planets closer in makes migration from the inner system unlikely. And I think we should leave formation issues there while we await new work, especially the authors note, from ALMA.
The Damasso paper reanalyzing the Proxima Centauri radial velocity data in 2017 is “Proxima Centauri reloaded: Unravelling the stellar noise in radial velocities,” Astronomy & Astrophysics 599, A126 (2017) (abstract/ preprint). The new Damasso et al. paper is “A low-mass planet candidate orbiting Proxima Centauri at a distance of 1.5 AU,’ Science Advances Vol. 6, No. 3 (15 January 2020). Full text. | 0.902297 | 4.015385 |
Pulsar vanishes suddenly, believed to be locked in massive tug-of-war with another star
The gravitational effects caused by the interaction between the two stars is so intense, it is warping space-time and causing a wobble that points the pulsar’s radio waves away from Earth.
Massive tug of war? Whatever. While people here on earth are focus on Massive tug of war, chemtrails, bigfoot, weird holes in Siberia, and rocks on Mars, some bright juvenile delinquent is making cosmic things disappear, probably using a homemade invisibility cloak gizmo, like the one above. Got the panties of a whole bunch of astronomers all in a bunch.
Astronomers are witnessing a massive tug-of-war between a rotating neutron star — known as a “pulsar” — and another star that is so intense, it is causing waves that bend space and make the pulsar wobble, causing it to disappear from view altogether.
Known as the spinning “lighthouses” of deep space, this particular pulsar has faded from view after being locked in a tight orbit with another star. Astronomers have been tracking the motion of the pulsar closely for five years, allowing them to determine its weight and how much of an effect it has on gravity, according to a BBC report.
Suddenly, the pulsar vanished, and the beams of radio waves that astronomers used to monitor are now pointed in a different direction. Scientists believe that this is because the dying star is wobbling into the dip in space-time that was created by its own orbit.
A pulsar is a neutron star that is small in size, but it is incredibly dense with a powerful gravitational pull. It is the result of a collapsed supernova, and contains more mass than the sun despite being contained in a sphere that is just 10 miles in diameter.
Neutron stars, when occurring in binaries, should generate space-time ripples known as gravitational waves under Einstein’s theory of general relativity — something that astronomers hope to be able to detect one day.
Known as Pulsar J1906, it showed up unexpectedly while Joeri van Leeuwen of the Netherlands Institute for Radio Astronomy, the study’s author, was conducting a survey at the Arecibo Observatory in Puerto Rico. He called it a “Eureka” moment, saying that he had surveyed the sky numerous times and then something bright showed up out of the blue.
Later, he discovered the pulsar had a companion star it was interacting with, the two bodies circling each other every four hours, the second fastest orbit ever witnessed. The pulsar rotated seven times per second, sweeping two beams of radio waves across the Earth.
His team monitored the waves almost every day for five years using radio telescopes, counting one billion rotations, allowing them to determine the gravitational interaction between the stars.
They are both only about 30 percent larger than the sun, but are only one solar diameter apart, causing extreme gravitational effects, including a time-space warp and a wobble that has pointed the pulsar’s light elsewhere for now. Dr. van Leeuwen said his calculations indicate it should swing back to pointing at the Earth by about 2170.
The findings were published in the Astrophysical Journal, and were also presented to the meeting of the American Astronomical Society. | 0.831353 | 3.777593 |
A Star's Early Chemistry Shapes Life-Friendly Atmospheres
Born in a disc of gas and rubble, planets eventually come together as larger and larger pieces of dust and rock stick together. They may be hundreds of light-years away from us, but astronomers can nevertheless watch these planets as they form.
One major point of interest is the chemistry of the rubble that forms around a star before a planetary system is formed, known as the protoplanetary disc.
The gas molecules that float in the disc could eventually become part of the atmosphere of the planets. If these molecules contain oxygen or nitrogen, the odds increase of a life-friendly planet forming.
"It’s very interesting to think about the molecular composition (of these discs)," said Catherine Walsh, an astronomer at Leiden Observatory in the Netherlands. "The molecules that are in those discs will make up the molecules in planetary atmospheres, and planetesimals such as comets."
Walsh led a new study, "Complex organic molecules in protoplanetary disks," which was published in February 2014 in the journal Astronomy and Astrophysics. In the study, the astronomers modeled how complex molecules form in protoplanetary systems with the hopes of better understanding their observations.
Seeking high definition observations
Molecules in protoplanetary discs emit their light in the millimeter and sub-millimeter frequencies of light, which are between the observation ranges of radio telescopes and infrared telescopes. Until recently, however, there have been few observatories devoted to this particular band of light with the necessary capabilities to see complex molecules.
"There has been a lot of work done to date, mainly with single-dish submillimeter telescopes," Walsh said.
While any observation is helpful, the single dish meant that astronomers could not get the high spatial resolution and sensitivity that they need to see more complex molecules. This changed in 2013, however, when the Atacama Large Millimeter Array (ALMA) in Chile lighted up for the first time.
The observatory — described as the largest astronomical project that exists right now — will eventually include 66 antennas located at 5,000 meters altitude, which puts it above much of the section of the atmosphere that blocks millimeter light from arriving at the surface.
"This is really the next big thing in molecular astrophysics, and ALMA will give us orders of magnitude (of improvement) in sensitivity," Walsh said.
Although her team has submitted a proposal to examine molecules using the giant array, the popularity of the telescope (which brings many competing proposals) means she is not sure if they will succeed.
If they do manage to get a slot of time, the astronomers will have to work quickly to publish their results.
"One great benefit is all of the ALMA data will be publicly available after one year. We will end up having this huge archive. Anyone can access the data and publish science with that data," Walsh said.
Where to look first?
Complex molecules are considered "precursors" of prebiotic chemistry, or the chemistry that gives rise to the conditions needed for life.
A famous example of prebiotic chemistry took place in 1952, when scientists Stanley Miller and Harold C. Urey put the gas forms of methane, hydrogen, ammonia and water vapor into a sealed container, then struck the gas with electricity (an analog of lightning). After doing this for a week, the walls of the container contained an organic sludge that included several of the amino acids that life uses today.
The question, Walsh said, is which complex molecules are present in protoplanetary discs, and would ALMA be able to see them? Complex molecules are not only potential precursors of life, but the ices in which they are thought to form also acts as a coagulant for dust grains to stick together and form planets.
Her team’s paper modeled the environment around T Tauri type stars, the phase that a young star goes through before turning into a star like our own Sun. Unlike stars that are older, the light that is emitted from these objects comes from gravitational contractions as the star draws material in from the surrounding disc.
Walsh’s team used calculations to generate a model of the disc, focusing on the temperature, density, structure and the strength of ultraviolet light. They then used this model to compute the chemistry. With this information in hand, they ran another set of calculations to predict what ALMA would be able to see.
Molecules are visible from afar because their rotation produces distinctive spectra, or line emissions that can be seen from Earth. The model predicted formaldehyde, a molecule with four atoms in it, which was a good thing because the results confirmed what has been detected in previous observations of protoplanetary discs. However, astronomers would like to find a more complex molecule like methanol, a derivative of methane, which on Earth is naturally produced by bacteria. In space, methanol is formed slightly differently: it is a derivative of carbon monoxide.
Methanol hasn’t been seen yet in protoplanetary discs. The more complex a molecule is, the less bright its spectrum appears in telescopes, making it harder to spot. Yet, Walsh said she’s nevertheless sure that the ALMA telescope would be up to the task of spotting methanol, a “first rung on the ladder of complexity,” and that could lead to the discovery of even more complex molecules, containing both oxygen and nitrogen.
If methanol is spotted, a next step would be to see where it occurs and study how it forms. In all likelihood, the molecule would form on the surface of dust grains because complex molecules are thought to have inefficient gas-phase routes to formation because of the low gas densities in space.
The next research step is to find glycine — the simplest amino acid and a building block for proteins — in protoplanetary discs. Walsh characterized glycine as "the holy grail" of research, and noted its "prebiotic significance” as one of the building blocks of life. But could ALMA detect glycine?
"I like to err on the cautious side,” she said. “It’s possibly beyond the capabilities of the telescope."
But then again, it’s hard to predict what sort of technology will be available in the future, she added.
One possibility is the Square Kilometer Array, a set of radio telescopes under construction in both Australia and South Africa, so named because the collecting area would be about a square kilometer (0.4 miles) in size. Construction of the telescope is scheduled to begin in 2018 and be finished by the mid-2020s.
The array will pick up a set of complex molecules with longer wavelengths and lower frequencies than ALMA.
"It’s possible we can see more prebiotic molecules with something like the Square Kilometer Array," she added.
Learning more about these complex molecules will also teach us about the ingredients which are available during the planet formation process, which will help astronomers understand how the molecular composition of the Earth, and the other Solar System planets, came to be, Walsh said.
"We’ve now seen thousands of exoplanets and we know that planet formation is ubiquitous,” she said. “We now know there are many more planets in the universe than stars, and there are a lot of stars (to research). There is so much to be done in (researching) this (protoplanetary) phase." | 0.874136 | 4.0082 |
Orion is one of the most recognizable constellations in the winter sky.
The easiest way to find Orion is to go outside in the evening this winter and look to the south east. You are looking for three bright stars close together in almost a straight line. These three stars represent Orion’s belt. The two bright stars to the north are his shoulders and the two to the south are his feet.
Orion the Hunter could walk on water because he was the son of the sea-god Poseidon. After many adventures Orion walked to the island of Crete where he hunted with the goddess Artemis. During the hunt, he threatened to kill every beast on Earth. But Mother Earth objected and sent a giant scorpion to kill him. After Orion’s death, Zeus placed him among the constellations adding the Scorpion as well, to commemorate the hero’s death.
One of the show pieces of Orion is the Great Nebula. To find it first locate Orion’s Belt, which contains the row of three bright stars. Next, look below his belt for a vertical row of fainter stars marking the Hunter’s Sword. Look for the fuzzy “star” in the middle of the Sword. That’s the Orion Nebula. Binoculars will give you a better view.
The Orion Nebula is a stellar nursery where new stars are being born. Stars form when clumps of hydrogen and other gases contract under their own gravity. As the gas collapses, the central clump grows stronger and the gas heats to extreme temperatures. When the temperature gets high enough, nuclear fusion ignites the gas to form a star. The star is ‘born’ when it begins to emit enough radiative energy to halt it’s gravitational collapse. Detailed observations have revealed approximately 700 stars in various stages of formation within this nebula.
The Pleiades – The Seven Sisters
Start by looking for the three stars in a diagonal row that make up Orion’s belt. Draw an imaginary line between those stars up and to the right. Continue your line, and you should come to a group of stars that looks like the letter “V”. That is the face of Taurus – The Bull. A little to the right of Taurus is a small clump of stars. They are the Pleiades, looking almost like a tiny dipper. Once again binoculars will give you a better view.
The Pleiades were the seven daughters of Atlas and the sea-nymph Pleione. After Atlas was forced to carry the heavens on his shoulders, Orion began to pursue all of the Pleiades. To comfort their father, Zeus transformed them first into doves, and then into stars. The constellation of Orion is said to still pursue The Pleiades across the night sky.
The Pleiades is an open star cluster containing hot middle-aged stars. It is one of the nearest star clusters to Earth. Probably formed from a nebula similar to the Orion Nebula around 100 million years ago, the cluster is dominated by hot blue and extremely luminous stars.
The faint reflection nebulosity around the brightest stars was at first thought to be left over from the formation of the cluster, but is now known to be an unrelated dust cloud in interstellar space, through which the stars are currently passing. Astronomers estimate that the cluster will survive for about another 250 million years, after which it’s stars will disperse.
Getting the best view
Discovering a dark place shouldn’t be too difficult on the Glenlivet Estate. I find my garden is as good a place as any. Switch off any outdoor lights and allow your eyes to acclimatise to the dark. In the dark your sensitive night time black and white vision will allow to you see more in the night sky, but it does take a while to kick in.
Avoid looking directly at any visible lighting. That will destroy your night vision almost instantly and you will have to wait another ten minutes before your dark adapted eyes are beginning to work again.
Because you are using your night vision you will only be seeing in black and white so don’t expect to see the Orion Nebula in full colour. Colour images can only be produced with long photographic exposures. Nevertheless witnessing the wonders of the night sky for yourself is an altogether different level of experience compared to admiring pictures by the Hubble space telescope from the comfort of your armchair.
Get out there and look up at our glorious dark skies! | 0.802551 | 3.113691 |
(CN) – An hourglass-shaped structure stretching hundreds of light-years above and below the center of the Milky Way is one of the largest formations ever observed in our galaxy, an international team of astronomers said in a study released Wednesday.
The structure – composed of twin “bubbles” that are hundreds of light-years tall – towers over other objects in the central region of the galaxy, according to the study published in the journal Nature.
Scientists said the radio-emitting formation was likely produced by a powerful energy explosion that occurred near the galaxy’s super massive black hole millions of years ago.
Oxford University researcher and study lead author Ian Heywood said in a statement that the Milky Way is comparatively calmer than other galaxies that have “very active” black holes at their center.
“Even so, the Milky Way’s central black hole can from time to time become uncharacteristically active, flaring up as it periodically devours massive clumps of dust and gas,” Heywood said. “It’s possible that one such feeding frenzy triggered powerful outbursts that inflated this previously unseen feature.”
To observe the structure, which is hidden from view behind a dense cloud of dust in the center of the galaxy, the team utilized the MeerKAT – originally the Karoo Array Telescope – a radio telescope consisting of 64 antennas spread across the Northern Cape of South Africa.
Northwestern University scientist Yusef Zadeh, who has studied volatile activity at our galaxy’s center for decades, said in the statement that the discovery illuminates “highly organized magnetic filaments” in the Milky Way’s center that he discovered in the 1980s.
“The radio bubbles discovered with MeerKAT now shed light on the origin of the filaments,” Zadeh said. “Almost all of the more than 100 filaments are confined by the radio bubbles.”
Researchers believe that the energy eruption that shaped the bubble-like structures – located 25,000 light-years from Earth – are closely related to an acceleration of electrons required for the formation’s radio-emitting qualities.
Scientists used a process known as synchrotron radiation – in which fast-moving electrons are shot into space to penetrate the magnetic fields in the galaxy’s cloudy center – to map out a radio signal of the formation.
The radio light produced by this observation is easily seen by MeerKAT, researchers said.
Fernando Camilo of the South African Radio Astronomy Observatory said in the statement that the twin bubbles were previously hidden from view because of the bright glare from radio light.
“Teasing out the bubbles from the background noise was a technical tour de force, only made possible by MeerKAT’s unique characteristics and ideal location,” Camilo said. “With this unexpected discovery we’re witnessing in the Milky Way a novel manifestation of galaxy-scale outflows of matter and energy, ultimately governed by the central black hole.”
The study was supported by South Africa’s National Research Foundation and the National Science Foundation. | 0.806665 | 3.578094 |
After Solar Orbiter, ESA’s next mission observing the Sun will not be one spacecraft but two: the double satellites making up Proba-3 will fly in formation to cast an artificial solar eclipse, opening up the clearest view yet of the Sun’s faint atmosphere – probing the mysteries of its million degree heat and magnetic eruptions.
Aiming for launch in mid-2022, Proba-3 comprises two small metre-scale satellites to be placed together in Earth orbit. They will line up to cast a precise shadow across space to block out the solar disc for six hours at a time during each 20 hour orbit, giving researchers a sustained view of the Sun’s immediate vicinity.
Precision formation flying
“To achieve this the satellite pair must achieve an unprecedented precision of flight control,” explains Proba-3 system manager Damien Galano. “They must align along an average distance of 144 m apart, maintained to an accuracy of a few millimetres. By achieving such precision formation flying techniques, in future multiple small satellites could perform equivalent tasks to individual giant spacecraft.”
Proba-3’s focus will be the Sun’s faint atmosphere, or corona, which extends millions of kilometres from the solar surface and is the source of the solar wind and coronal mass ejections – huge magnetic eruptions that can affect space weather all the way to Earth itself.
The corona is also the basis of a long-standing scientific mystery: while the Sun’s surface is a comparatively cool 6000 °C, the corona rises to a sizzling million degrees or more – in apparent defiance to the laws of thermodynamics.
But the dazzling face of the Sun usually masks the faint, wispy corona, like a blazing bonfire next to a firefly.
Revealing the solar corona
“Up until now, the best way to see the corona is briefly during a solar eclipse on Earth, or else using a ‘coronagraph’ instrument incorporating one or more blocking – or ‘occulting’ – discs to blot out the Sun’s disc,” says solar scientist Andrei Zhukov of the Royal Observatory of Belgium (ROB).
He is the principal investigator of Proba-3’s main ASPIICS (Association of Spacecraft for Polarimetric and Imaging Investigation of the Corona of the Sun) telescope, while also serving as ROB’s project scientist of Solar Orbiter’s Extreme Ultraviolet Imager (EUI).
“But sunlight still bends around such blocking discs– known as ‘diffraction’ – which can leads to a high level of straylight within an instrument, degrading the resulting image,” adds Andrei.
“The idea behind Proba-3 is to cut that straylight fivefold and in the same time observe very close to the edge of the Sun, by flying the external blocking disc far away from the rest of the telescope, aboard a separate satellite.
“I’m looking forward to the time when Proba-3 is operating along with other Sun-watching missions. While Solar Orbiter’s EUI observes changes on the solar surface in extreme ultraviolet, Proba-3 will clearly show associated features within the inner corona in visible light, revealing interactions between the Sun and its surroundings.”
Mission taking shape
The mission has passed its ‘critical design review’, leading to the manufacturing and testing of satellite hardware.
“The prototype of the 1.4-m diameter external occulting disc has undergone testing,” explains Delphine Jollet, platform system engineer.
“Its rim, made of temperature-resistant carbon fibre reinforced polymer (CFRP), has to meet very stringent requirements to precisely hold its torus shape, designed to minimise the straylight spilling over its edges into ASPIICS. Skilled workmanship is essential to prepare the CFRP layout for moulding.”
“A secondary internal occulting disc is mounted within the instrument, this one just 3.5 mm in diameter, but having similarly stringent dimensional standards,” notes Proba-3 payload engineer Jorg Versluys.
“This internal occulter is part of the qualification model of the ASPIICS instrument that is being tested in simulated space conditions.” | 0.835885 | 3.895333 |
Spacecraft and satellites could in future be launched into space without the need for fuel, thanks to a revolutionary new theory.
Dr Mike McCulloch, from the University of Plymouth, first put forward the idea of quantised inertia (QI) - through which he believes light can be converted into thrust - in 2007.
He has now received $1.3million from the United States Defense Advanced Research Projects Agency (DARPA) for a four-year study which aims to make the concept a reality.
The QI theory predicts that objects can be pushed by differences in the intensity of so-called Unruh radiation in space, similar to the way in which a ship can be pushed towards a dock because there are more waves hitting it from the seaward side.
The theory has already predicted galaxy rotation without dark matter, and the fact that if a system is accelerated enough - such as a spinning disc or light bouncing between mirrors - the Unruh waves it sees can be influenced by a shield. Therefore, if a damper is placed above the object, it should produce a new kind of upwards thrust.
Chemical rockets are very expensive because of the explosive propellant they need, so this new kind of thruster would be much cheaper and safer as it would only need a source of electrical power to accelerate the core of a thruster.
Dr McCulloch, Lecturer in Geomatics at the University, believes the study could benefit all forms of propulsion and transport, with a potentially transformative impact on space launch systems, aircraft and cars.
He said: "I believe QI could be a real game changer for space science. I have always thought it could be used to convert light into thrust, but it also suggests ways to enhance that thrust. It is hugely exciting to now have the opportunity to test it."
The research is being funded through DARPA's Nascent Light-Matter Interactions (NLM) programme, which aims to improve the fundamental understanding of how to control the interaction of light and engineered materials.
It will see Dr McCulloch collaborating with experimental scientists from the Technische Universität Dresden in Germany, and the University of Alcala in Spain.
Over the first 18 months, the Plymouth team will seek to develop a fully predictive theoretical model of how matter interacts with light (Unruh radiation) using the quantised inertia model. This will provide a new predictive tool for light-matter interactions.
A series of experiments will then be conducted in Germany and Spain to test whether the thrust is specifically due to quantised inertia, and whether it can be enhanced significantly.
"Ultimately, what this could mean is you would need no propellant to launch a satellite," Dr McCulloch added. "But it would also mean you only need a source of electrical power, for example solar power, to move any craft once it is in space. It has the potential to make interplanetary travel much easier, and interstellar travel possible." | 0.856097 | 3.36188 |
A new galactic game launches today that lets citizen scientists identify the glowing clouds where future stars will be born.
The online experience, called Clouds, is a new addition to the Milky Way Project, where everyone can help astronomers to sort and measure our galaxy. Clouds features images and data from NASA’s Spitzer Space Telescope and the Herschel Space Observatory, a European Space Agency mission with important participation from NASA.
In the rapid-fire game, players gauge whether a targeted section of a presented image is a cloud, a “hole” – an empty region of space – or something in between. The cataloging of these snapshots of the local cosmos will help astronomers learn more about the architecture and character of our home galaxy, the Milky Way.
The organizers of Clouds encourage astronomy enthusiasts to start playing now because with enough participation, important insights into the Milky Way could come as soon as early next year.
“We’re really excited to launch Clouds and see results back from our giant volunteer team of amateur scientists,” said Robert Simpson, a postdoctoral researcher in astronomy at Oxford University, England and principal investigator of the Milky Way Project. “We think the community can blast through all these data fairly quickly. We may even be done by the spring and that would be an amazing result for citizen science.”
Clouds joins its predecessor Milky Way Project game, Bubbles, as one of the many “crowdsourced” efforts underway at Zooniverse, home to the Internet’s biggest and most popular online citizen science projects.
The crowdsourcing concept involves having a lot of people evaluate the same image or pieces of data. A consensus decision on some aspect of the image is then reached through the collective “wisdom of crowds.” Crowdsourced citizen science becomes especially important when humans can do a better job at analyzing images or objects than a computer can. The Clouds game is an example of just such an exercise in which eyeballs and brains beat out cameras and computer algorithms.
The goal of Clouds is to tag the dense, cold cores of gas and dust known as infrared dark clouds. These clouds collapse under their own gravity and then burst forth as new stars. An empty region of space, however, can look rather like one of these dark clouds and deceive a computer accordingly. “Automated routines have tried to decide which of these objects are holes and which are true infrared dark clouds, but the task is often tricky and it takes a human eye to decide,” said Simpson.
The Latest Streaming News: Citizen science updated minute-by-minute
Bookmark this page and come back often | 0.847517 | 3.364515 |
Everybody knows that the Moon changes its face. Sometimes we have Full Moons, other times it’s a Half-moon, or a crescent, or there’s no Moon at all. And everybody knows that these are called the phases of the Moon. But not everybody knows that these faces follow a regular cycle, or that the common descriptions are misleading at best. A proper understanding of what’s actually happening to make the moon show different faces, and the nature of the “Dark Side of the Moon”, is quite rare.
The motion of the Moon
So here’s the first thing you need to understand. The moon is an unusually large satellite of the Earth (most planet’s satellites are much smaller than their parent), and it orbits very far from the earth (again, compared to most satellites in the Solar System). Depending on your point of view, it takes roughly either 27 days or 29 days to orbit the earth. Against a fixed reference point (say, a distant star), the moon takes 27.3 days to revolve around the earth and this is called the Sidereal Period. However, if we count from Full Moon to Full Moon, we find it takes 29.5 days: the Synodic Period. The reason for this discrepancy is the fact that, in those 27.3 days the earth has shuffled along around the sun — slightly less than one twelfth of the way, in fact, since 27.3 days is a little less than one month. In that time, the Sun appears to move in the sky (relative to the stars – this movement, incidentally, is the basis of astrology’s horoscope birthsigns), so that the phases are a little behind what we expect. What have the phases got to do with the Sun?
The Sun’s influence on the Phases
First, we need to know about the phases. The moon has four basic phases: New, 1st Quarter, Full (or 2nd Quarter), 3rd Quarter, and back to New. A New moon is when the moon is completely blank. People commonly refer to the crescent moon a few days before and after this as a New Moon, but this is only because you can’t really a see the true new moon as it is completely dark and so close to the sun that the glare hides it. 1st Quarter is named because the moon is now a quarter of the way through it’s cycle, and looks like a “Half-moon”. Full moon is when the whole face of the moon is illuminated and Third Quarter is “The other Half-moon”. If the phase is busy changing towards Full, so that the face of the moon is growing bigger, then we say that the moon is “Waxing”, and if it is in the opposite situation then we say that it is “Waning”.
The Phases of the Moon
Now that these definitions are out of the way, we can think about the Sun. Everything in the solar system is (usually) lit up by the sun. The side facing the Sun is bright, and the side facing away from the Sun is dark. We describe these two sides of the Earth as the day side, and the night side. On the moon, I call them the Light Side, and the Dark Side. Most astronomers will explain that there is no dark side, but this is because people confuse the near/far sides with the light/dark sides. Obviously different parts of the moon will be dark at different points in the synodic cycle, since as it moves around the earth, it’s presenting different sides to the sun. It is the movement of the light/dark side that causes the phases. At full moon, we are directly facing the light side. At New moon, we are facing the dark side. At 1st and 3rd Quarter, we are facing exactly between the two sides. It’s all quite simple. But what was that about Near and Far sides?
The Dark side of the Moon versus the Far Side
Interesting fact about the moon: The time it takes to orbit the earth is exactly the same as the time it takes to rotate on its own axis. This means that we only ever see one side of the moon! If you’re having trouble visualising how this works, try “orbiting” a tennis ball around your head and turning it in such a way that you only ever see the one side. It’s a simple concept to demonstrate, but not so easy to explain!. The side of the Moon that always faces us is called the Near Side, and the side that faces away is the Far Side. Light side and Dark side, are always changing, but Near side and Far side are fixed.
One last thing…
At any particular phase, the moon is always at the same place in the sky relative to the sun. This is why you only ever see crescent moons near sunset or sunrise, close to the sun, and why the full moon always rises just as the sun sets, and sets just as the sun rises. Here’s an intellectual exercise for you: Try to visualise the moon, earth and sun in space and work out where all three are relative to each other at each phase. You’ll find the answer on most astronomy textbooks, or this wikipedia page.
Liked it? Take a second to support Allen Versfeld on Patreon! | 0.851224 | 3.833008 |
Not only is Jupiter the largest planet in the solar system, it is also the most massive at more than times the mass of Earth. Its size plays a. Hubble image of the planet Jupiter and its rings with a computer simulation of Jupiter The four biggest moons of Jupiter are famous in the field of astronomy.
There are 79 known moons of Jupiter. This gives Jupiter the largest number of known moons with reasonably stable orbits of any planet in the Solar System. The Galilean moons (or Galilean satellites) are the four largest moons of Jupiter —Io, Europa, Ganymede, and Callisto. They were first seen by Galileo Galilei in.
bright star, crescent moon, another bright star seen in the bare branches of a . NASA's Galileo spacecraft acquired its highest resolution images of Jupiter's. Jupiter has 79 confirmed moons. There are many interesting moons orbiting the planet, but the ones of most scientific interest are the first four moons.
Each of the Jovian planets has several characteristics in common. While Saturn's bright rings are the most visible and well known, fainter and darker rings have. As a group, the Jovian planets (Jupiter, Saturn, Uranus, and Neptune) can best be described as large gasballs - or better yet, spinning drops of liquid.
A terrestrial planet, telluric planet, or rocky planet is a planet that is composed primarily of silicate rocks or metals. Within the Solar System, the terrestrial planets. The four inner planets of the solar system — those closest to the sun — are terrestrial planets having Earth-like features.
The gas giants of our solar system are Jupiter, Saturn, Uranus and Neptune. These four large planets, also called jovian planets after Jupiter. Gas Giants. A gas giant, also known as a jovian planet after the planet Jupiter, gaseous giant, or giant planet, is a large planet which has at least ten times the. | 0.822302 | 3.079825 |
|Common use||Astro · Gregorian · Islamic · ISO · Julian|
|Lunisolar · Solar · Lunar|
|Selected usage||Armenian · Bahá'í · Bengali · Berber · Bikram Samwat · Buddhist · Chinese · Coptic · Ethiopian · Germanic · Hebrew · Hindu · Indian · Iranian · Irish · Japanese · Javanese · Juche · Korean · Malayalam · Maya · Minguo · Nanakshahi · Nepal Sambat · Tamil · Thai (Lunar – Solar) · Tibetan · Turkish · Vietnamese· Yoruba · Zoroastrian|
|Original Julian · Runic|
The Julian calendar was a reform of the Roman calendar which was introduced by Julius Caesar in 46 BC and came into force in 45 BC (709 ab urbe condita). It was chosen after consultation with the astronomer Sosigenes of Alexandria and was probably designed to approximate the tropical year, known at least since Hipparchus. It has a regular year of 365 days divided into 12 months, and a leap day is added to February every four years. Hence the Julian year is on average 365.25 days long.
The Julian calendar remained in use into the 20th century in some countries as a national calendar, but it has generally been replaced by the modern Gregorian calendar. It is still used by the Berber people of North Africa and by many national Orthodox churches. Orthodox Churches no longer using the Julian calendar typically use the Revised Julian calendar rather than the Gregorian calendar.
The notation "Old Style" (OS) is sometimes used to indicate a date in the Julian calendar, as opposed to "New Style" (NS), which either represents the Julian date with the start of the year as 1 January or a full mapping onto the Gregorian calendar.
The ordinary year in the previous Roman calendar consisted of 12 months, for a total of 355 days. In addition, a 27-day intercalary month, the Mensis Intercalaris, was sometimes inserted between February and March. This intercalary month was formed by inserting 22 days after the first 23 or 24 days of February, the last five days of February becoming the last five days of Intercalaris. The net effect was to add 22 or 23 days to the year, forming an intercalary year of 377 or 378 days.
According to the later writers Censorinus and Macrobius, the ideal intercalary cycle consisted of ordinary years of 355 days alternating with intercalary years, alternately 377 and 378 days long. On this system, the average Roman year would have had 366¼ days over four years, giving it an average drift of one day per year relative to any solstice or equinox. Macrobius describes a further refinement wherein, for 8 years out of 24, there were only three intercalary years, each of 377 days. This refinement averages the length of the year to 365¼ days over 24 years. In practice, intercalations did not occur schematically according to these ideal systems, but were determined by the pontifices. So far as can be determined from the historical evidence, they were much less regular than these ideal schemes suggest. They usually occurred every second or third year, but were sometimes omitted for much longer, and occasionally occurred in two consecutive years.
If managed correctly this system allowed the Roman year, on average, to stay roughly aligned to a tropical year. However, if too many intercalations were omitted, as happened after the Second Punic War and during the Civil Wars, the calendar would drift rapidly out of alignment with the tropical year. Moreover, since intercalations were often determined quite late, the average Roman citizen often did not know the date, particularly if he were some distance from the city. For these reasons, the last years of the pre-Julian calendar were later known as years of confusion. The problems became particularly acute during the years of Julius Caesar's pontificate before the reform, 63 BC to 46 BC, when there were only five intercalary months, whereas there should have been eight, and none at all during the five Roman years before 46 BC.
The reform was intended to correct this problem permanently, by creating a calendar that remained aligned to the sun without any human intervention.
Julian reform Edit
The first step of the reform was to realign the start of the calendar year (1 January) to the tropical year by making 46 BC 445 days long, compensating for the intercalations which had been missed during Caesar's pontificate. This year had already been extended from 355 to 378 days by the insertion of a regular intercalary month in February. When Caesar decreed the reform, probably shortly after his return from the African campaign in late Quintilis (July), he added 67 (=22+23+22) more days by inserting two extraordinary intercalary months between November and December. These months are called "Intercalaris Prior" and "Intercalaris Posterior" in letters of Cicero written at the time; there is no basis for the statement sometimes seen that they were called "Unodecember" and "Duodecember". Their individual lengths are unknown, as is the position of the Nones and the Ides within them. Because 46 BC was the last of a series of irregular years, this extra-long year was, and is, referred to as the last year of confusion. The first year of operation of the new calendar was 45 BC.
The Julian months were formed by adding ten days to a regular pre-Julian Roman year of 355 days, creating a regular Julian year of 365 days: Two extra days were added to Ianuarius, Sextilis (Augustus) and December, and one extra day was added to Aprilis, Iunius, September and November, setting the lengths of the months to the values they still hold today:
|Months||Lengths before 45 BC||Lengths after 46 BC|
|Februarius||28 (23/24)||28 (29)|
Macrobius states that the extra days were added immediately before the last day of each month to avoid disturbing the position of the established Roman fasti (days prescribed for certain events) relative to the start of the month. However, since Roman dates after the Ides of the month counted down towards the start of the next month, the extra days had the effect of raising the initial value of the count of the day after the Ides. Romans of the time born after the Ides of a month responded differently to the effect of this change on their birthdays. Mark Antony kept his birthday on the 14th day of Ianuarius, which changed its date from a.d. XVII Kal. Feb. to a.d. XIX Kal. Feb., a date that had previously not existed. Livia kept the date of her birthday unchanged at a.d. III Kal. Feb., which moved it from the 28th to the 30th day of Ianuarius, a day that had previously not existed. Augustus kept his on the 23rd day of September, but both the old date (a.d. VIII Kal. Oct.) and the new (a.d. IX Kal. Oct.) were celebrated in some places.
The old intercalary month was abolished. The new leap day was originally inserted following February 24, a.d. VI Kal. Mar. by Roman reckoning, since this is the point at which intercalary months were inserted in the pre-Julian calendar. It was considered as extending that day to 48 hours, so it was dated as "a.d. VI bis Kal. Mar.", and is called the bissextile day. During the late Middle Ages when days in the month came to be numbered in consecutive day order, the Leap Day was considered to be the last day in February in leap years, i.e. February 29.
Leap year errorEdit
Although the new calendar was much simpler than the pre-Julian calendar, the pontifices apparently misunderstood the algorithm for leap years. They added a leap day every three years, instead of every four years. According to Macrobius, the error was the result of counting inclusively, so that the four year cycle was considered as including both the first and fourth years. This resulted in too many leap days. Augustus remedied this discrepancy after 36 years by restoring the correct frequency. He also skipped several leap days in order to realign the year.
The historic sequence of leap years in this period is not given explicitly by any ancient source, although the existence of the triennial leap year cycle is confirmed by an inscription that dates from 9 or 8 BC. The chronologist Joseph Scaliger established in 1583 that the Augustan reform was instituted in 8 BC, and inferred that the sequence of leap years was 42, 39, 36, 33, 30, 27, 24, 21, 18, 15, 12, 9 BC, AD 8, 12 etc. This proposal is still the most widely accepted solution. It has sometimes been suggested that there was an additional bissextile day in the first year of the Julian reform, i.e. that 45 BC was also a leap year.
Other solutions have been proposed from time to time. Kepler proposed in 1614 that the correct sequence of leap years was 43, 40, 37, 34, 31, 28, 25, 22, 19, 16, 13, 10 BC, AD 8, 12 etc. In 1883 the German chronologist Matzat proposed 44, 41, 38, 35, 32, 29, 26, 23, 20, 17, 14, 11 BC, AD 4, 8, 12 etc., based on a passage in Dio Cassius that mentions a leap day in 41 BC that was said to be contrary to (Caesar's) rule. In the 1960s Radke argued the reform was actually instituted when Augustus became pontifex maximus in 12 BC, suggesting the sequence 45, 42, 39, 36, 33, 30, 27, 24, 21, 18, 15, 12 BC, AD 4, 8, 12 etc. With all these solutions, except that of Radke, the Roman calendar was not finally aligned to the Julian calendar of later times until 26 February (a.d. V Kal. Mar.) AD 4. On Radke's solution, the two calendars were aligned on 26 February 1 BC.
In 1999, an Egyptian papyrus was published that gives an ephemeris table for 24 BC with both Roman and Egyptian dates. From this it can be shown that the most likely sequence was in fact 44, 41, 38, 35, 32, 29, 26, 23, 20, 17, 14, 11, 8 BC, AD 4, 8, 12 etc, very close to that proposed by Matzat. This sequence shows that the standard Julian leap year sequence began in AD 4, the 12th year of the Augustan reform, and that the Roman calendar was finally aligned to the Julian calendar in 1 BC, as in Radke's model. The Roman year also coincided with the proleptic Julian year between 32 and 26 BC. This suggests that one aim of the realignment portion of the Augustan reform was to ensure that key dates of his career, notably the fall of Alexandria on 1 August 30 BC, were unaffected by his correction.
Roman dates before 32 BC were typically a day or two before the day with the same Julian date, so 1 January in the Roman calendar of the first year of the Julian reform was 31 December 46 BC (Julian date). A curious effect of this is that Caesar's assassination on the Ides (15th day) of March fell on 14 March 44 BC in the Julian calendar.
Immediately after the Julian reform, the twelve months of the Roman calendar were named Ianuarius, Februarius, Martius, Aprilis, Maius, Iunius, Quintilis, Sextilis, September, October, November, and December, just as they were before the reform. The old intercalary month, the Mensis Intercalaris, was abolished and replaced with a single intercalary day at the same point (i.e. five days before the end of Februarius). The first month of the year continued to be Ianuarius, as it had been since 153 BC.
The Romans later renamed months after Julius Caesar and Augustus, renaming Quintilis (originally, "the Fifth month", with March = month 1) as Iulius (July) in 44 BC and Sextilis ("Sixth month") as Augustus (August) in 8 BC. Quintilis was renamed to honour Caesar because it was the month of his birth. According to a senatus consultum quoted by Macrobius, Sextilis was renamed to honour Augustus because several of the most significant events in his rise to power, culminating in the fall of Alexandria, fell in that month.
Other months were renamed by other emperors, but apparently none of the later changes survived their deaths. Caligula renamed September ("Seventh month") as Germanicus; Nero renamed Aprilis (April) as Neroneus, Maius (May) as Claudius and Iunius (June) as Germanicus; and Domitian renamed September as Germanicus and October ("Eighth month") as Domitianus. At other times, September was also renamed as Antoninus and Tacitus, and November ("Ninth month") was renamed as Faustina and Romanus. Commodus was unique in renaming all twelve months after his own adopted names (January to December): Amazonius, Invictus, Felix, Pius, Lucius, Aelius, Aurelius, Commodus, Augustus, Herculeus, Romanus, and Exsuperatorius.
Much more lasting than the ephemeral month names of the post-Augustan Roman emperors were the names introduced by Charlemagne. He renamed all of the months agriculturally into Old High German. They were used until the 15th century, and with some modifications until the late 18th century in Germany and in the Netherlands (January-December): Wintarmanoth (winter month), Hornung (the month when the male red deer sheds its antlers), Lentzinmanoth (Lent month), Ostarmanoth (Easter month), Wonnemanoth (love making month), Brachmanoth (plowing month), Heuvimanoth (hay month), Aranmanoth (harvest month), Witumanoth (wood month), Windumemanoth (vintage month), Herbistmanoth (autumn/harvest month), and Heilagmanoth (holy month).
The Julian reform set the lengths of the months to their modern values. However, a 13th century scholar, Sacrobosco, proposed a different explanation for the lengths of Julian months which is still widely repeated but is certainly wrong. According to Sacrobosco, the original scheme for the months in the Julian Calendar was very regular, alternately long and short. From January through December, the month lengths according to Sacrobosco for the Roman Republican calendar were:
30, 29, 30, 29, 30, 29, 30, 29, 30, 29, 30, 29
He then thought that Julius Caesar added one day to every month except February, a total of 11 more days, giving the year 365 days. A leap day could now be added to the extra short February:
31, 29/30, 31, 30, 31, 30, 31, 30, 31, 30, 31, 30
He then said Augustus changed this to:
31, 28/29, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31
so that the length of Augustus would not be shorter than (and therefore inferior to) the length of Iulius, giving us the irregular month lengths which are still in use.
There is abundant evidence disproving this theory. First, a wall painting of a Roman calendar predating the Julian reform has survived, which confirms the literary accounts that the months were already irregular before Julius Caesar reformed them:
29, 28, 31, 29, 31, 29, 31, 29, 29, 31, 29, 29
Also, the Julian reform did not change the dates of the Nones and Ides. In particular, the Ides were late (on the 15th rather than 13th) in March, May, July and October, showing that these months always had 31 days in the Roman calendar, whereas Sacrobosco's theory requires that March, May and July were originally 30 days long and that the length of October was changed from 29 to 30 days by Caesar and to 31 days by Augustus. Further, Sacrobosco's theory is explicitly contradicted by the third and fifth century authors Censorinus and Macrobius, and it is inconsistent with seasonal lengths given by Varro, writing in 37 BC, before the Augustan reform, with the 31-day Sextilis given by the new Egyptian papyrus from 24 BC, and with the 28-day February shown in the Fasti Caeretani, which is dated before 12 BC.
The dominant method that the Romans used to identify a year for dating purposes was to name it after the two consuls who took office in it. Since 153 BC, they had taken office on 1 January, and Julius Caesar did not change the beginning of the year. Thus this consular year was an eponymous or named year. In addition to consular years, the Romans sometimes used the regnal year of the emperor, and by the late fourth century documents were also being dated according to the 15-year cycle of the indiction. In 537, Justinian required that henceforth the date must include the name of the emperor and his regnal year, in addition to the indiction and the consul, while also allowing the use of local eras.
In 309 and 310, and from time to time thereafter, no consuls were appointed. When this happened, the consular date was given a count of years since the last consul (so-called "post-consular" dating). After 541, only the reigning emperor held the consulate, typically for only one year in his reign, and so post-consular dating became the norm. Similar post-consular dates are also known in the West in the early sixth century. The last known post-consular date is year 22 after the consulate of Heraclius. The last emperor to hold the consulate was Constans II. The system of consular dating, long obsolete, was formally abolished in the law code of Leo VI, issued in 888.
Only rarely did the Romans number the year from the founding of the city (of Rome), ab urbe condita (AUC). This method was used by Roman historians to determine the number of years from one event to another, not to date a year. Different historians had several different dates for the founding. The Fasti Capitolini, an inscription containing an official list of the consuls which was published by Augustus, used an epoch of 752 BC. The epoch used by Varro, 753 BC, has been adopted by modern historians. Indeed, Renaissance editors often added it to the manuscripts that they published, giving the false impression that the Romans numbered their years. Most modern historians tacitly assume that it began on the day the consuls took office, and ancient documents such as the Fasti Capitolini which use other AUC systems do so in the same way. However, Censorinus, writing in the third century AD, states that, in his time, the AUC year began with the Parilia, celebrated on 21 April, which was regarded as the actual anniversary of the foundation of Rome. Because the festivities associated with the Parilia conflicted with the solemnity of Lent, which was observed until the Saturday before Easter Sunday, the early Roman church did not celebrate Easter after 21 April.
While the Julian reform applied originally to the Roman calendar, many of the other calendars then used in the Roman Empire were aligned with the reformed calendar under Augustus. This led to the adoption of several local eras for the Julian calendar, such as the Era of Actium and the Spanish Era, some of which were used for a considerable time. Perhaps the best known is the Era of Martyrs, sometimes also called Anno Diocletiani (after Diocletian), which was often used by the Alexandrian Christians to number their Easters during the fourth and fifth centuries and continued to be used by the Coptic and Abyssinian churches.
In the Eastern Mediterranean, the efforts of Christian chronographers such as Annianus of Alexandria to date the Biblical creation of the world led to the introduction of Anno Mundi eras based on this event. The most important of these was the Aetos Kosmou, used throughout the Byzantine world from the 10th century and in Russia till 1700. In the West, Dionysius Exiguus proposed the system of Anno Domini in 525. This era gradually spread through the western Christian world, once the system was adopted by Bede.
New Year's DayEdit
The Roman calendar began the year on 1 January, and this remained the start of the year after the Julian reform. However, even after local calendars were aligned to the Julian calendar, they started the new year on different dates. The Alexandrian calendar in Egypt started on 29 August (30 August after an Alexandrian leap year). Several local provincial calendars were aligned to start on the birthday of Augustus, 23 September. The indiction caused the Byzantine year, which used the Julian calendar, to begin on 1 September; this date is still used in the Eastern Orthodox Church for the beginning of the liturgical year. When the Julian calendar was adopted in Russia in AD 988 by Vladimir I of Kiev, the year was numbered Anno Mundi 6496, beginning on 1 March, six months after the start of the Byzantine Anno Mundi year with the same number. In 1492 (AM 7000), Ivan III, according to church tradition, realigned the start of the year to 1 September, so that AM 7000 only lasted for six months in Russia, from 1 March to 31 August 1492.
During the Middle Ages 1 January retained the name New Year's Day (or an equivalent name) in all Western European countries (affiliated with the Roman Catholic Church), since the medieval calendar continued to display the months from January to December (in twelve columns containing 28 to 31 days each), just as the Romans had. However, most of those countries began their numbered year on 25 December (the Nativity of Jesus), 25 March (the Incarnation of Jesus), or even Easter, as in France (see the Liturgical year article for more details).
In England before 1752, 1 January was celebrated as the New Year festival, but the "year starting 25th March was called the Civil or Legal Year, although the phrase Old Style was more commonly used." To reduce misunderstandings on the date, it was not uncommon in parish registers for a new year heading after 24 March for example 1661 had another heading at the end of the following December indicating "1661/62". This was to explain to the reader that the year was 1661 Old Style and 1662 New Style.
Most Western European countries shifted the first day of their numbered year to 1 January while they were still using the Julian calendar, before they adopted the Gregorian calendar, many during the sixteenth century. The following table shows the years in which various countries adopted 1 January as the start of the year. Eastern European countries, with populations showing allegiance to the Orthodox Church, began the year on 1 September from about 988.
Note that as a consequence of change of New Year, 1 January 1751 to 24 March 1751 were non-existent dates in England.
|Country||Year starting 1st January||Adoption of the Gregorian calendar|
|Republic of Venice||1522||1582|
|Holy Roman Empire||1544||1582|
|Prussia, and Denmark||1559||1700|
|United Provinces of the Netherlands||1583||1582 (Holland and Zeeland), 1700 (other provinces)|
From Julian to GregorianEdit
The Julian calendar was in general use in Europe and Northern Africa from the times of the Roman Empire until 1582, when Pope Gregory XIII promulgated the Gregorian Calendar. Reform was required because too many leap days are added with respect to the astronomical seasons on the Julian scheme. On average, the astronomical solstices and the equinoxes advance by about 11 minutes per year against the Julian year. As a result, the calculated date of Easter gradually moved out of phase with the moon. While Hipparchus and presumably Sosigenes were aware of the discrepancy, although not of its correct value, it was evidently felt to be of little importance at the time of the Julian reform. However, it accumulated significantly over time: the Julian calendar gained a day about every 134 years. By 1582, it was ten days out of alignment.
The Gregorian Calendar was soon adopted by most Catholic countries (e.g. Spain, Portugal, Poland, most of Italy). Protestant countries followed later, and the countries of Eastern Europe even later. In the British Empire (including the American colonies), Wednesday 2 September 1752 was followed by Thursday 14 September 1752. For 12 years from 1700 Sweden used a modified Julian Calendar, and adopted the Gregorian calendar in 1753, but Russia remained on the Julian calendar until 1917, after the Russian Revolution (which is thus called the 'October Revolution' though it occurred in Gregorian November), while Greece continued to use it until 1923. During this time the Julian calendar continued to diverge from the Gregorian. In 1700 the difference became 11 days; in 1800, 12; and in 1900, 13, where it will stay till 2100.
Although all Eastern Orthodox countries (most of them in Eastern or Southeastern Europe) had adopted the Gregorian calendar by 1927, their national churches had not. A revised Julian calendar was proposed during a synod in Constantinople in May 1923, consisting of a solar part which was and will be identical to the Gregorian calendar until the year 2800, and a lunar part which calculated Easter astronomically at Jerusalem. All Orthodox churches refused to accept the lunar part, so almost all Orthodox churches continue to celebrate Easter according to the Julian calendar (the Finnish Orthodox Church uses the Gregorian Easter).
The solar part of the revised Julian calendar was accepted by only some Orthodox churches. Those that did accept it, with hope for improved dialogue and negotiations with the Western denominations, were the Ecumenical Patriarchate of Constantinople, the Patriarchates of Alexandria, Antioch, the Orthodox Churches of Greece, Cyprus, Romania, Poland, Bulgaria (the last in 1963), and the Orthodox Church in America (although some OCA parishes are permitted to use the Julian calendar). Thus these churches celebrate the Nativity on the same day that Western Christians do, 25 December Gregorian until 2800. The Orthodox Churches of Jerusalem, Russia, Macedonia, Serbia, Georgia, Ukraine, and the Greek Old Calendarists continue to use the Julian calendar for their fixed dates, thus they celebrate the Nativity on 25 December Julian (which is 7 January Gregorian until 2100).
In Northern Africa, the Julian calendar (the Berber calendar) is still in use for agricultural purposes, and is called فلاحي fellāhī "peasant" or sاﻋﺠﻤﻲ acjamī "not Arabic". The first of yennayer currently corresponds to January 14 and will do until 2100.
- Gregorian calendar
- Julian day
- Julian year
- Old Style and New Style dates
- Proleptic Julian calendar
- Roman calendar
- ^ Note that the letter J.
- ^ Roscoe Lamont, "The Roman calendar and its reformation by Julius Caesar", Popular Astronomy 27 (1919) 583–595. The reference is the second article in the hyperlink; its last page is here. Sacrobosco's theory is discussed on pages 585–587.
- ^ Roman Republican calendar
- ^ Chronography of AD 354, see
- ^ Charles W. Jones, "Development of the Latin Ecclesiastical calendar", Bedae Opera de Temporibus (1943), 1-122, p.28.
- ^ История календаря в России и в СССР (Calendar history in Russia and in the USSR)
- ^ http://www.pepysdiary.com/archive/1661/12/31/index.php, Pepys Diary "I sat down to end my journell for this year, ..."
- ^ Spathaky, Mike Old Style New Style dates and the change to the Gregorian calendar.
- ^ Spathaky, Mike Old Style New Style dates and the change to the Gregorian calendar. "An oblique stroke is by far the most usual indicator, but sometimes the alternative final figures of the year are written above and below a horizontal line, as in a fraction (a form which cannot easily be reproduced here in ASCII text). Very occasionally a hyphen is used, as 1733-34."
- ^ Mike Spathaky Old Style and New Style Dates and the change to the Gregorian Calendar: A summary for genealogists
- ^ The source has Germany, whose current area during the sixteenth century was a major part of the Holy Roman Empire, a religiously divided confederation. The source is unclear as to whether all or only parts of the country made the change. In general, Roman Catholic countries made the change a few decades before Protestant countries did.
- ^ Sweden's conversion is complicated and took much of the first half of the 18ไทย:
century see Gregorian calendar: Timeline for details
- ^ Per decree of 16 June 1575. Hermann Grotefend, "Osteranfang" (Easter beginning), Zeitrechnung de Deutschen Mittelalters und der Neuzeit (Chronology of the German Middle Ages and modern times) (1891-1898)
- Calendars through the ages on WebExhibits.
- Calendar FAQ
- Roman Dates
- The Roman Calendar
- Synoptical Julian-Gregorian Calendar - compare the Julian and Gregorian calendars for any date between 1582 and 2100 using this side-by-side reference.
- Date Conversion
- Calendar Converter — converts between several calendars, for example Gregorian, Julian, Mayan, Persian, Hebrew
|This page uses content from the English language Wikipedia. The original content was at Julian calendar. The list of authors can be seen in the page history. As with this Familypedia wiki, the content of Wikipedia is available under the Creative Commons License.| | 0.817914 | 3.149864 |
Apollo 13’s designated landing site was near Fra Mauro crater; the Fra Mauro formation was believed to contain much material spattered by the impact that had filled the Imbrium basin early in the Moon’s history. Dating it would provide information not only about the Moon, but about the Earth’s early history. The landing site was near what was dubbed Cone crater, a site where an impact was believed to have drilled deep into the lunar regolith. Due to the roughness of the terrain, the selected landing site was over a mile (two kilometers) from Cone crater, but Lovell, who as commander was to perform the landing, had the option of setting down closer if he believed he could do so safely. NASA initially had few high-quality photographs of that location, but after Apollo 12 took more from orbit in November 1969, Fra Mauro was confirmed as Apollo 13’s landing site.
Titan has three large seas. However, the seas of Titan are not filled with water, but are filled instead with swirling liquid hydrocarbons. All three of Titan's exotic seas are close to its north pole, and they are surrounded by many smaller hydrocarbon-filled lakes in the northern hemisphere.
It is not a very expensive stone and is made into necklaces or bigger pieces for jewelry purposes. I especially like the deep, dark blue version with golden pyrite sprinkles creating very unique patterns mined only in Afghanistan. The lighter blue, grayish variety is found in Chile.
The Solar System forms a tiny part of the Milky Way Galaxy, a vast conglomeration of stars and planets. What makes astronomy so thrilling is that despite its size, the Milky Way is not the only galaxy in the universe. There are hundreds of billions of galaxies out there, probably more. The closest galaxy to our own Milky Way is Andromeda. Now, brace yourself for the distance: it is 2.3 million light years away. One of the most exciting phenomena for astronomers is the black hole. It is an area of the universe where the concentration of mass is so massive (no pun intended) that the gravitational pull it generates sucks in everything around it. Everything includes light. Remember that the escape velocity for any object in the universe is the speed required to escape the objects gravitational pull. The escape velocity for the Earth is slightly over 11 kilometers per hour while for the Moon is 2.5 kilometers per second. Well for a black hole, the escape velocity exceeds the speed of light. That is how strong the pull is. | 0.884468 | 3.803762 |
Exploring an asteroid, comet or a small moon like Mars' Phobos isn’t easy. We can’t send a rover like Curiosity, because there just isn’t enough gravity for it to wheel across the surface. But what if we sent something much lighter and smaller?
That’s what one team of scientists is proposing with a cube-shaped robot they have called Hedgehog. The vehicle wouldn’t use wheels; instead, it would propel itself by spinning disc-shaped flywheels in its interior. Rotating them at high speeds and then suddenly stopping them, the cube-shaped robot can send itself tumbling across the surface. And it can even perform precise maneuvers with the technique.
The research is a joint effort between NASA’s Jet Propulsion Laboratory (JPL), Stanford University in California, and the Massachusetts Institute of Technology (MIT).
"Hedgehog is a different kind of robot that would hop and tumble on the surface instead of rolling on wheels," said Issa Nesnas, leader of the JPL team, in a statement. "It is shaped like a cube and can operate no matter which side it lands on."
Hedgehog would weigh about 9 kilograms (20 pounds). Spikes dotted around the cube would protect its body and also allow it to grip onto the surface. In its casing, it could have a number of cameras and instruments to study the surface of a comet or asteroid, and thanks to its “hopping” technique, it could explore vast regions. Its cube shape also makes it ideal to be carried by a larger spacecraft to a destination.
The robot can even get itself out of a tight situation. As seen on Comet 67P, there are a number of sinkholes that could pose a problem to robotic explorers. But Hedgehog can perform a “tornado” maneuver, where it rapidly spins itself to move up and out of a hole.
Above is a video explanation of Hedgehog. NASA.
The project is being funded through the NASA Innovative Advanced Concepts (NIAC) program. The team envisages that Hedgehog could even be autonomous, hopping its way across a celestial body and relaying information to a spacecraft in orbit.
Various tests were performed with Hedgehog prototypes recently, including in the simulated low-gravity environment on NASA’s C-9 aircraft, which makes looping flights to induce microgravity for a short period of time.
While Hedgehog hasn’t been formally picked for a mission yet, who knows; maybe it’ll be coming to an asteroid or comet near you soon. | 0.845565 | 3.547801 |
By cooking up a faux comet, scientists have produced the first formation of a key sugar required for life as we know it. By creating ices similar to those detected by the European Space Agency's Rosetta mission, which made the first landing on a comet, scientists were able to produce ribose, a sugar that serves as an important ingredient in RNA, an essential ingredient for life.
"There is evidence for an 'RNA world' — an episode of life on Earth during which RNA was the only genetic material," Cornelia Meinert, an associate scientist at the University Nice Sophia Antipolis, told Space.com by email. Meinert led experiments that dosed icy materials produced in a laboratory with radiation similar to what comets would have received in the early life of the solar system, resulting in the creation of ribose.
"At a certain point in prebiotic evolution, the availability of ribose would have been, therefore, necessary for life to have started," Meinert said. [Watch: Comets - The Seeds of Life from Beyond the Solar System]
Cooking a comet
Organisms on Earth are made up of DNA and RNA— the genetic material that controls organisms' physical makeup. Their production has remained a long-standing question since their discovery, as has the origin of the important molecules that they comprise. Many of these molecules would not have survived in the high temperatures of the solar system where Earth formed, so scientists suspect that comets, which formed in cooler regions but travel inward, might have delivered organic material when they crashed into Earth.
To test this theory, Meinert and her colleagues recreated ices detected by Rosetta's Philae lander when it touched down on Comet 67P in 2014. In a lab, they created interstellar ices under what Meinert called "realistic astrophysical conditions" — in other words, within a vacuum, surrounded by low temperatures. Then, they blasted the samples with radiation simulating energy from the young sun, which was far more active than today's star, along with cosmic rays from the rest of the galaxy. Some of the material from the ices evaporated, while the leftover material created an organic residue. Sampling this residue revealed not only sugars but also amino acids, alcohols and other material.
"We were confronted with a very complex sample containing a huge diversity of molecules," Meinert said. "The identification of individual compounds was, therefore, very difficult."
By combining an instrument with higher-resolution power than utilized by previous techniques with an optimized method to selectively detect and extract sugar and sugar-related molecules, the team overcame these challenges to detect ribose and other sugars in larger quantities than previously estimated. The scientists deemed the material "major molecular constituents" of condensed ices found in space.
The research was published on April 7 in the journal Science.
Life's ingredients from comets?
When Philae visited Comet 67P, it carried a Cometary Sampling and Composition Experiment (COSAC) instrument, which employs a gas chromatograph (GC) to analyze material and a mass spectrometer (MS) to measure their masses. COSAC detected 16 organics on the comet, but none were the sugars and amino acids that mission planners had hoped to see.
"After landing on Comet 67P, we tried to employ the full GC-MS mode of COSAC, which would have been sensitive enough for amino acids and sugar molecules," COSAC co-investigator Uwe Meierhenrich told Space.com by email. Meierhenrich, a professor at the University Nice Sophia Antipolis, was a co-author on the study.
But Philae's landing did not go smoothly; instead of anchoring to the comet, the tiny spacecraft bounced across its surface. As a result, COSAC and other instruments couldn't perform all of the experiments they had planned.
"We did not receive enough samples from Philae's drilling and distribution system because of the unpredicted 'vertical landing position' of Philae," Meierhenrich said.
However, the experiments revealed a closer kinship of the evolved ices to meteorites than had been suspected. Organic material has been found in some meteorites, and both meteorites and comets are considered possible sources of Earth's water.
"We assume that the organics found in meteorites form by very similar initial reactions as compared to the organics in comets," Meierhenrich said.
Copyright 2016 SPACE.com, a Purch company. All rights reserved. This material may not be published, broadcast, rewritten or redistributed. | 0.884766 | 3.865717 |
Unless you were living under a very large and heavy rock last week, you probably heard about the discovery of seven planets in the TRAPPIST-1 system by Michaël Gillon and colleagues.
Although this system was already known to host three, roughly Earth-sized transiting planets, the discovery of four more throws the door wide open for habitability – all seven planets receive the right amount of starlight from their diminutive red-dwarf host that liquid water might be stable on their surfaces.
There are so many interesting questions to explore for this system – What are the planets’ atmospheres like? How did this system of tightly-packed planets form and how do their orbits remain stable? And, of course, are they habitable?
Fortunately, concerted follow-up observations and theoretical studies can probably a lot of these questions. The fact that the planets all transit their small host star means their atmospheres are ideal for study by the James Webb Space Telescope. Strong gravitational tugs among the planets caused their orbits to change visibly over the course of the observations, so we have strong constraints on how exactly the planets interact.
The last and probably most important question is going to be a lot more difficult to answer. But since a detailed understanding of this system is likely (and probably inevitable, given the enormous enthusiasm for this system), we’ll soon be very close to answering the question of whether the TRAPPIST-1 system is habitable and maybe even inhabited.
One bit of trivia: the TRAPPIST survey that discovered this system was named in honor of the contemplative Roman Catholic religious order of Trappists, and the astronomers reportedly celebrated their discovery with a round of Trappist beer. Maybe this should be the start of a new tradition of naming new planetary systems after beers. | 0.884711 | 3.573007 |
Dynamical systems such as a system of 3 planetary bodies can exhibit surprisingly complicated behavior. If the initial state of the system is slightly varied, the resulting system behaves in a radically different manner. This "sensitivity to initial conditions" is a key element of what's become (perhaps disproportionately) well-known as chaos. Using the mathematical notion of iterative systems, we can model such systems and understand how chaos arises out of deceptively simple foundations.
The study of dynamical systems, natural or abstract systems that evolve at each instance in time according to a specific rule, is an active and fruitful area of research in mathematics. Its study has yielded insights into the nature of social networks such as Facebook, the spread of diseases such as influenza, and the behavior of the financial markets. In this series of posts, we'll look in depth at dynamical systems, as well as at the related subjects of chaos theory and fractals, all of which are both interesting and useful for understanding our world.
From our "intrinsic" point-of-view on the surface of the Earth, it appears to be flat, but if we examine the Earth from the "extrinsic" point of view, somewhere off the Earth's surface, we can see that it is clearly a curved surface. Amazingly, it is possible to determine that the Earth is spherical simply by taking measurements on its surface, and it is possible to generalize these measurements in order to study the shape of the universe. Mathematicians such as Riemann did just this, and Einstein was able to apply these geometric ideas to his "general theory of relativity", which describes the relation between gravitation, space, and time.
Geometry literally means "the measurement of the Earth", and more generally means the study of measurements of different kinds of space. Geometry on a flat surface, and geometry on the surface of a sphere, for example, are fundamentally different. A consequence of this disparity is the fact that it is impossible to create a perfectly accurate (flat) map of the Earth's (spherical) surface. Every map of the Earth necessarily has distortions. In this post we look at a few different methods of map-making and evaluate their distortions as well as their respective advantages.
This is the first of a series of three posts. In this post we'll see how the Greeks developed a system of geometry - literally "Earth measure" - to assist with planetary navigation. We then will see why their assumption that the Earth is flat means that Euclidean geometry is insufficient for studying the Earth. The Earth's spherical surface looks flat from our perspective, but is actually qualitatively different from a flat surface. In the ensuing posts, we'll see why this implies that it is impossible to make a perfectly accurate map of the Earth, and build on this idea to get a glimpse into Einstein's revolutionary theories regarding the geometry of the space-time universe.
Recent discoveries in the branch of physics known as quantum mechanics have powerful applications in the field of network security - they have the potential to break forms of internet security based on mathematics such as the RSA algorithm, and also present new ways to safely send information. In this article we’ll see how a physics-based method can be used to secure online information.
Over 300 years ago, a mathematician named Fermat discovered a subtle property about prime numbers. In the 1970's, three mathematicians at MIT showed that his discovery could be used to formulate a remarkably powerful method for encrypting information to be sent online. The RSA algorithm, as it is known, is used to secure ATM transactions, online business, banking, and even electronic voting. Surprisingly, it's not too difficult to understand, so let's see how it works. | 0.804685 | 3.458047 |
An object approximately the same size as Pluto, Eris, was discovered only 8 years ago (in 2005). Are there any Pluto-sized objects remaining to be discovered, and if so, how far away from the Sun would they have to be to not have been detected already?
This is a part answer to your question, as it is difficult to answer without speculating, so here are some facts/observations related to your question.
Asides from Pluto/Charon, Eris, Triton (could be a captured Kuiper Belt object), Makemake and the football shaped Haumea, most of the Kuiper Belt Objects (KBOs) are according to the article "Kuiper Belt Objects: Facts about the Kuiper Belt & KBOs" (Redd, 2012):
thousands of bodies more than 62 miles (100 km) in diameter travel around the sun within this belt, along with trillions of smaller objects, many of which are short-period comets
and is believed to have a total mass of only a tenth of the Earth, according to the article "Forming the Kuiper Belt by the Outward Transport of Objects During Neptune's Migration" (Levison and Morbidelli).
Here is a list Of the many Transneptunian Objects that have been documented, detailing their absolute magnitudes.
In regards to one of your main questions - according to Redd (2012), the challenge in their detection is
Because of their small size and distant location, Kuiper Belt Objects are a challenge to spot from Earth. Infrared measurements from NASA's space-based telescope, Spitzer, have helped to nail down sizes for the largest objects.
I would add, their irregular elliptical orbits* and extreme (compared to the major planets) inclination to ecliptic make it that much more difficult to detect them. Additionally, according to "The Edge of the Solar System" website, further difficulties include low surface reflectivity.
- An example of a possible KBO with an extremely elliptical orbit is Sedna, which is believed to take over 10,000 years to orbit the sun; is smaller than Pluto, but was observed at about 90AU (3 times further than Pluto).
So, there could be many small Pluto-sized 'dark' worlds in highly elliptical irregular orbits in the Kuiper Belt and beyond. However, beyond those listed, we have not seen that many and the total mass theorised does not support the idea of too many in existence, but that does not mean that they are not out there. | 0.855758 | 3.833018 |
An international research team led by Dr. Daisuke Suzuki (ISAS) has reported a statistical analysis showing that sub-Saturn giant exoplanets are common, not rare. This finding could alter the standing theory of planet formation that predicts an alien world with a mass that's between that of Neptune and Saturn, and its location beyond the "snow line" of its host star, is rare.
The study was published in the December 20th issue of The Astrophysical Journal Letters.
"We were just finishing up the analysis when the mass measurements of OGLE-2012- BLG-0950Lb came in," said Dr. Suzuki. "This exoplanet was first detected by the microlensing method, one of the detection methods of exoplanets, and the mass was estimated with high accuracy based on the observations by the Keck II telescope and the Hubble Space Telescope. This planet confirmed our interpretation of the statistical study."
Dr. Suzuki explains, "only the microlensing method is currently sensitive enough to detect planets with less than Saturn's mass in orbits beyond the snow line, or frost line, of the host stars."
Microlensing leverages a consequence of Einstein's theory of general relativity: the bending and magnification of light near a massive object like a star, producing a natural lens on the sky. In the case of OGLE-2012-BLG-0950Lb, the light from a distant background star was magnified by OGLE-2012-BLG-0950L (the exoplanet's host star) over the course of two months as it passed close to perfect alignment in the sky with the background star.
By carefully analyzing the light during the alignment, an unexpected dimming with a duration of about a day was observed, revealing the presence of OGLE-2012-BLG-0950Lb via its own influence on the lensing.
For the statistical study, the properties of 30 sub-Saturn planets found by microlensing were analyzed and compared them to predictions from standard theory of planetary system formation, i.e., the core accretion theory.
The snow line is the distance in a protoplanetary disk at which it is cold enough for water to condense into ice. At and beyond the snow line there is a dramatic increase in the amount of solid material needed for planet formation. According to the core accretion theory, the solids are thought to build up into planetary cores first through chemical and then gravitational processes.
"A key process of the core accretion theory is called "runaway gas accretion," said Dr. Suzuki. "Giant planets are thought to start their formation process by collecting a core mass of about 10 times the Earth mass in rock and ice. Then, the accretion of gas and dust is expected to speed up exponentially in this runaway gas accretion process. This process stops when the supply is exhausted. If the supply of gas is stopped before runaway accretion stops, we get "failed Jupiter" planets with masses of 10-20 Earth-masses (like Neptune)."
The runaway gas accretion scenario of the core accretion theory predicts that planets with masses of 20 - 30 earth's mass are expected to be rare. Suzuki's team compared the distribution of planet-star mass ratios found by microlensing to distributions predicted by the core accretion theory.
They found that the core accretion theory's runaway gas accretion process predicts about 10 times fewer intermediate-mass giant planets than those seen in the microlensing results. This new result suggests that the runaway growth scenario may need revision.
This discrepancy implies that gas giant formation may involve processes that have been overlooked by existing core accretion models, or that the planet-forming environment varies considerably as a function of host star mass or host star's situation such as stellar density.
"We want to observe a larger number of exoplanetary systems and determine the masses of the alian worlds in high accuracy. In this way, we can study the census of exoplanetary systems in statistically significance. " | 0.911273 | 3.928288 |
Hipparchus (Greek Ἳππαρχος) (ca. 190 B.C.E. - ca. 120 B.C.E.) was a Greek, astronomer, geographer, and mathematician of the Hellenistic period. He is known to have been active at least from 147 B.C.E. to 127 B.C.E. Hipparchus is considered the greatest astronomical observer, and by some the greatest astronomer of classical antiquity. He was the first Greek to develop quantitative and accurate models for the motion of the Sun and Moon, making use of the observations and knowledge accumulated over centuries by the Chaldeans from Babylonia. He was also the first to compile a trigonometric table, which allowed him to solve any triangle. Based on his solar and lunar theories and his numerical trigonometry, he was probably the first to develop a reliable method to predict solar eclipses. His other achievements include the discovery of precession, the compilation of the first star catalogue of the Western world, and probably the invention of the astrolabe. Three centuries later, the work of Claudius Ptolemaeus depended heavily on Hipparchus. Ptolemy’s synthesis of astronomy superseded Hipparchus's work; although Hipparchus wrote at least fourteen books, only his commentary on the popular astronomical poem by Aratus has been preserved by later copyists.
- 1 Life
- 2 Thought and Works
- 2.1 Babylonian sources
- 2.2 Geometry and trigonometry
- 2.3 Lunar and solar theory
- 2.4 Astronomical instruments and astrometry
- 2.5 Geography
- 2.6 Star catalogue
- 2.7 Stellar magnitude
- 2.8 Precession of the Equinoxes (146 B.C.E.-130 B.C.E.)
- 2.9 Hipparchus and Astrology
- 3 Notes
- 4 References
- 5 External links
- 6 Credits
Most of what is known about Hipparchus comes from Ptolemy's (second century C.E.) Almagest, with additional references to him by Pappus of Alexandria and Theon of Alexandria (fourth century) in their commentaries on the Almagest; from Strabo's Geographia ("Geography"), and from Pliny the Elder's Natural History (Naturalis historia) (first century).
There is a strong tradition that Hipparchus was born in Nicaea (Greek Νικαία), in the ancient district of Bithynia (modern-day Iznik in province Bursa), in what today is Turkey. The exact dates of his life are not known, but Ptolemy attributes astronomical observations to him from 147 B.C.E. to 127 B.C.E.; earlier observations since 162 B.C.E. might also have been made by him. The date of his birth (ca. 190 B.C.E.) was calculated by Delambre based on clues in his work. Hipparchus must have lived some time after 127 B.C.E. because he analyzed and published his latest observations then. Hipparchus obtained information from Alexandria as well as Babylon, but it is not known if and when he visited these places.
It is not known what Hipparchus' livelihood was and how he supported his scientific activities. There are no contemporary portraits of him, but in the second and third centuries coins were made in his honor in Bithynia that bear his name and show him with a globe; this supports the tradition that he was born there.
Hipparchus is believed to have died on the island of Rhodes, where he spent most of his later life. Ptolemy attributes observations to him from Rhodes in the period from 141 B.C.E. to 127 B.C.E.
Thought and Works
Hipparchus' main original works are lost. His only preserved work is Toon Aratou kai Eudoxou Fainomenoon exegesis ("Commentary on the Phaenomena of Eudoxus and Aratus"), a critical commentary in two books on a popular poem by Aratus based on the work by Eudoxus of Cnidus. Hipparchus also made a list of his major works, which apparently mentioned about fourteen books, but which is only known from references by later authors. His famous star catalogue probably was incorporated into the one by Ptolemy, and cannot be reliably reconstructed. We know he made a celestial globe; a copy of a copy may have been preserved in the oldest surviving celestial globe accurately depicting the constellations: the globe carried by the Farnese Atlas.
Hipparchus is recognized as the originator and father of scientific astronomy. He is believed to be the greatest Greek astronomical observer, and many regard him as the greatest astronomer of ancient times, although Cicero gave preferences to Aristarchus of Samos and some scholars also favor Ptolemy of Alexandria. Hipparchus' writings had been mostly superseded by those of Ptolemy, so later copyists have not preserved them for posterity.
The European Space Agency's Hipparcos Space Astrometry Mission was named after Hipparchus, as were the Hipparchus lunar crater and the asteroid 4000 Hipparchus.
Earlier Greek astronomers and mathematicians were influenced by Babylonian astronomy to a limited extent, for instance the period relations of the Metonic cycle and Saros cycle may have come from Babylonian sources. Hipparchus seems to have been the first to systematically exploit Babylonian astronomical knowledge and techniques. He was the first Greek known to divide the circle in 360 degrees of 60 arc minutes (Eratosthenes before him used a simpler sexagesimal system dividing a circle into 60 parts). He also used the Babylonian unit pechus ("cubit") of about 2° or 2½°.
Hipparchus probably compiled a list of Babylonian astronomical observations; historian of astronomy G. Toomer has suggested that Ptolemy's knowledge of eclipse records and other Babylonian observations in the Almagest came from a list made by Hipparchus. Hipparchus' use of Babylonian sources has always been known in a general way, because of Ptolemy's statements. However, Franz Xaver Kugler demonstrated that the periods that Ptolemy attributes to Hipparchus had already been used in Babylonian ephemerides, specifically the collection of texts nowadays called "System B" (sometimes attributed to Kidinnu).
Geometry and trigonometry
Hipparchus is recognised as the first mathematician to compile a trigonometry table, which he needed when computing the eccentricity of the orbits of the Moon and Sun. He tabulated values for the chord function, which gives the length of the chord for each angle. He did this for a circle with a circumference of 21,600 and a radius of (rounded) 3438 units: this has a unit length of 1 arc minute along its perimeter. He tabulated the chords for angles with increments of 7.5°. In modern terms, the chord of an angle equals twice the sine of half of the angle, i.e.:
- chord(A) = 2 sin(A/2).
He described it in a work (now lost), called Toon en kuklooi eutheioon (Of Lines Inside a Circle) by Theon of Alexandria (fourth century) in his commentary on the Almagest I.10; some claim his table may have survived in astronomical treatises in India, for instance the Surya Siddhanta. This was a significant innovation, because it allowed Greek astronomers to solve any triangle, and made it possible to make quantitative astronomical models and predictions using their preferred geometric techniques.
For his chord table Hipparchus must have used a better approximation for π than the one from Archimedes (between 3 + 1/7 and 3 + 10/71); maybe the one later used by Ptolemy: 3;8:30 (sexagesimal) (Almagest VI.7); but it is not known if he computed an improved value himself.
Hipparchus could construct his chord table using the Pythagorean Theorem and a theorem known to Archimedes. He also might have developed and used the theorem in plane geometry called Ptolemy's theorem, because it was proved by Ptolemy in his Almagest (I.10) (later elaborated on by Lazare Carnot).
Hipparchus was the first to show that the stereographic projection is conformal, and that it transforms circles on the sphere that do not pass through the center of projection to circles on the plane. This was the basis for the astrolabe.
Hipparchus was one of the first Greek mathematicians to used Chaldean arithmetic techniques, and in this way expanded the techniques available to astronomers and geographers.
There is no indication that Hipparchus knew spherical trigonometry, which was first developed by Menelaus of Alexandria in the first century. Ptolemy later used the new technique for computing things like the rising and setting points of the ecliptic, or to take account of the lunar parallax. Hipparchus may have used a globe for this (to read values off the coordinate grids drawn on it), as well as approximations from planar geometry, or arithmetical approximations developed by the Chaldeans.
Lunar and solar theory
Motion of the Moon
Hipparchus studied the motion of the Moon and confirmed the accurate values for some periods of its motion that Chaldean astronomers had obtained before him. The traditional value (from Babylonian System B) for the mean synodic month is 29 days;31,50,8,20 (sexagesimal) = 29.5305941… d. Expressed as 29 days + 12 hours + 793/1080 hours this value has been used later in the Hebrew calendar (possibly from Babylonian sources). The Chaldeans also knew that 251 synodic months = 269 anomalistic months. Hipparchus extended this period by a factor of 17, because after that interval the Moon also would have a similar latitude, and it is close to an integer number of years (345). Therefore, eclipses would reappear under almost identical circumstances. The period is 126007 days 1 hour (rounded). Hipparchus could confirm his computations by comparing eclipses from his own time (presumably January 27, 141 B.C.E. and November 26, 139 B.C.E. according to [Toomer 1980]), with eclipses from Babylonian records 345 years earlier (Almagest IV.2; [Jones 2001]). Al-Biruni (Qanun VII.2.II) and Copernicus (de revolutionibus IV.4) noted that the period of 4,267 lunations is actually about 5 minutes longer than the value for the eclipse period that Ptolemy attributes to Hipparchus. However, the best clocks and timing methods of the age had an accuracy of no better than 8 minutes. Modern scholars agree that Hipparchus rounded the eclipse period to the nearest hour, and used it to confirm the validity of the traditional values, rather than try to derive an improved value from his own observations. From modern ephemerides and taking account of the change in the length of the day we estimate that the error in the assumed length of the synodic month was less than 0.2 s in the fourth century B.C.E. and less than 0.1 s in Hipparchus' time.
Orbit of the Moon
It had been known for a long time that the motion of the Moon is not uniform: its speed varies. This is called its anomaly, and it repeats with its own period; the anomalistic month. The Chaldeans took account of this arithmetically, and used a table giving the daily motion of the Moon according to the date within a long period. The Greeks however preferred to think in geometrical models of the sky. Apollonius of Perga had at the end of the third century B.C.E. proposed two models for lunar and planetary motion:
- In the first, the Moon would move uniformly along a circle, but the Earth would be eccentric, i.e., at some distance of the center of the circle. So the apparent angular speed of the Moon (and its distance) would vary.
- The Moon itself would move uniformly (with some mean motion in anomaly) on a secondary circular orbit, called an epicycle, that itself would move uniformly (with some mean motion in longitude) over the main circular orbit around the Earth, called deferent. Apollonius demonstrated that these two models were in fact mathematically equivalent. However, all this was theory and had not been put to practice. Hipparchus was the first to attempt to determine the relative proportions and actual sizes of these orbits.
Hipparchus devised a geometrical method to find the parameters from three positions of the Moon, at particular phases of its anomaly. In fact, he did this separately for the eccentric and the epicycle model. Ptolemy describes the details in the Almagest IV.11. Hipparchus used two sets of three lunar eclipse observations, which he carefully selected to satisfy the requirements. The eccentric model he fitted to these eclipses from his Babylonian eclipse list: 22/23 December 383 B.C.E., 18/19 June 382 B.C.E., and 12/13 December 382 B.C.E. The epicycle model he fitted to lunar eclipse observations made in Alexandria at 22 September 201 B.C.E., 19 March 200 B.C.E., and 11 September 200 B.C.E.
- For the eccentric model, Hipparchus found for the ratio between the radius of the eccenter and the distance between the center of the eccenter and the center of the ecliptic (i.e., the observer on Earth): 3144 : 327+2/3 ;
- and for the epicycle model, the ratio between the radius of the deferent and the epicycle: 3122+1/2 : 247+1/2 .
The cumbersome unit he used in his chord table resulted in peculiar numbers, and errors in rounding and calculating (for which Ptolemy criticized) him produced inconsistent results; he later used the ratio of the epicycle model (3122+1/2 : 247+1/2), which is too small (60 : 4;45 hexadecimal): Ptolemy established a ratio of 60: 5+1/4 .
Apparent motion of the Sun
Before Hipparchus, Meton, Euctemon, and their pupils at Athens had made a solstice observation (i.e., timed the moment of the summer solstice) on June 27, 432 B.C.E. (proleptic Julian calendar). Aristarchus of Samos is said to have done so in 280 B.C.E., and Hipparchus also had an observation by Archimedes. Hipparchus himself observed the summer solstice in 135 B.C.E., but he found observations of the moment of equinox more accurate, and he made many during his lifetime. Ptolemy gives an extensive discussion of Hipparchus' work on the length of the year in the Almagest III.1, and quotes many observations that Hipparchus made or used, spanning 162 B.C.E. to 128 b.c.e..
Ptolemy quotes an equinox timing by Hipparchus (at March 24, 146 B.C.E. at dawn) that differs from the observation made on that day in Alexandria (at 5h after sunrise): Hipparchus may have visited Alexandria but he did not make his equinox observations there; presumably he was on Rhodes (at the same geographical longitude). He may have used his own armillary sphere or an equatorial ring for these observations. Hipparchus (and Ptolemy) knew that observations with these instruments are sensitive to a precise alignment with the equator. The real problem however is that atmospheric refraction lifts the Sun significantly above the horizon: so its apparent declination is too high, which changes the observed time when the Sun crosses the equator. Worse, the refraction decreases as the Sun rises, so it may appear to move in the wrong direction with respect to the equator in the course of the day. Ptolemy noted this, however, Ptolemy and Hipparchus apparently did not realize that refraction is the cause.
At the end of his career, Hipparchus wrote a book called Peri eniausíou megéthous ("On the Length of the Year") about his results. The established value for the tropical year, introduced by Callippus in or before 330 B.C.E. (possibly from Babylonian sources), was 365 + 1/4 days. Hipparchus' equinox observations gave varying results, but he himself points out (quoted in Almagest III.1(H195)) that the observation errors by himself and his predecessors may have been as large as 1/4 day. So he used the old solstice observations, and determined a difference of about one day in about 300 years. He set the length of the tropical year to 365 + 1/4 - 1/300 days (= 365.24666... days = 365 days 5 hours 55 min, which differs from the actual value (modern estimate) of 365.24219... days = 365 days 5 hours 48 min 45 s by only about 6 min).
Between the solstice observation of Meton and his own, there were 297 years spanning 108,478 days. This implies a tropical year of 365.24579... days = 365 days;14,44,51 (sexagesimal; = 365 days + 14/60 + 44/602 + 51/603), and this value has been found on a Babylonian clay tablet [A. Jones, 2001], indicating that Hipparchus' work was known to Chaldeans.
Another value for the year that is attributed to Hipparchus (by the astrologer Vettius Valens in the first century) is 365 + 1/4 + 1/288 days (= 365.25347... days = 365 days 6 hours 5 min), but this may be a corruption of another value attributed to a Babylonian source: 365 + 1/4 + 1/144 days (= 365.25694... days = 365 days 6 hours 10 min). It is not clear if this would be a value for the sidereal year (actual value at his time (modern estimate) ca. 365.2565 days), but the difference with Hipparchus' value for the tropical year is consistent with his rate of precession.
Orbit of the Sun
Before Hipparchus the Chaldean astronomers knew that the lengths of the seasons are not equal. Hipparchus made equinox and solstice observations, and according to Ptolemy (Almagest III.4) determined that spring (from spring equinox to summer solstice) lasted 94 + 1/2 days, and summer (from summer solstice to autumn equinox) 92 + 1/2 days. This is an unexpected result, given a premise of the Sun moving around the Earth in a circle at uniform speed. Hipparchus' solution was to place the Earth not at the center of the Sun's motion, but at some distance from the center. This model described the apparent motion of the Sun fairly well (of course today we know that the planets, including the Earth, move in ellipses around the Sun, but this was not discovered until Johannes Kepler published his first two laws of planetary motion in 1609). The value for the eccentricity attributed to Hipparchus by Ptolemy is that the offset is 1/24 of the radius of the orbit (which is too large), and the direction of the apogee would be at longitude 65.5° from the vernal equinox. Hipparchus may also have used another set of observations (94 + 1/4 and 92 + 3/4 days), which would lead to different values. The question remains if Hipparchus is really the author of the values provided by Ptolemy, who found no change three centuries later, and added lengths for the autumn and winter seasons.
Distance, parallax, size of the Moon and Sun
Hipparchus also undertook to find the distances and sizes of the Sun and the Moon. He published his results in a work of two books called Peri megethoon kai 'apostèmátoon ("On Sizes and Distances") by Pappus of Alexandria in his commentary on the Almagest V.11; Theon of Smyrna (second century) mentions the work with the addition "of the Sun and Moon."
Hipparchus measured the apparent diameters of the Sun and Moon with his diopter. Like others before and after him, he found that the Moon's size varies as it moves on its (eccentric) orbit, but he found no perceptible variation in the apparent diameter of the Sun. He found that at the mean distance of the Moon, the Sun and Moon had the same apparent diameter; at that distance, the Moon's diameter fits 650 times into the circle, i.e., the mean apparent diameters are 360/650 = 0°33'14."
Like others before and after him, he also noticed that the Moon has a noticeable parallax, i.e., that it appears displaced from its calculated position (compared to the Sun or stars), and the difference is greater when closer to the horizon. He knew that this is because the Moon circles the center of the Earth, but the observer is at the surface - Moon, Earth and observer form a triangle with a sharp angle that changes all the time. From the size of this parallax, the distance of the Moon as measured in Earth radii can be determined. For the Sun however, there was no observable parallax (we now know that it is about 8.8," more than ten times smaller than the resolution of the unaided eye).
In the first book, Hipparchus assumed that the parallax of the Sun was 0, as if it is at infinite distance. He then analyzed a solar eclipse, presumably that of March 14, 190 B.C.E.. It was total in the region of the Hellespont (and, in fact, in his birth place Nicaea); at the time the Romans were preparing for war with Antiochus III in the area, and the eclipse is mentioned by Livy in his Ab Urbe Condita VIII.2. It was also observed in Alexandria, where the Sun was reported to be 4/5 obscured by the Moon. Alexandria and Nicaea are on the same meridian. Alexandria is at about 31° North, and the region of the Hellespont at about 41° North; authors like Strabo and Ptolemy had reasonable values for these geographical positions, and presumably Hipparchus knew them too. Hipparchus was able to draw a triangle formed by the two places and the Moon, and from simple geometry was able to establish a distance of the Moon, expressed in Earth radii. Because the eclipse occurred in the morning, the Moon was not in the meridian, and as a consequence, the distance found by Hipparchus was a lower limit. In any case, according to Pappus, Hipparchus found that the least distance is 71 (from this eclipse), and the greatest 81 Earth radii.
In the second book, Hipparchus started from the opposite extreme assumption: he assigned a (minimum) distance to the Sun of 470 Earth radii. This would correspond to a parallax of 7', which is apparently the greatest parallax that Hipparchus thought would not be noticed (for comparison: the typical resolution of the human eye is about 2'; Tycho Brahe made naked eye observation with an accuracy down to 1'). In this case, the shadow of the Earth is a cone, rather than a cylinder as under the first assumption. Hipparchus observed (at lunar eclipses) that at the mean distance of the Moon, the diameter of the shadow cone is 2+½ lunar diameters. That apparent diameter is, as he had observed, 360/650 degrees. With these values and simple geometry, Hipparchus could determine the mean distance; because it was computed for a minimum distance of the Sun, it was the maximum mean distance possible for the Moon. With his value for the eccentricity of the orbit, he could also compute the least and greatest distances of the Moon. According to Pappus, Hipparchus found a least distance of 62, a mean of 67+1/3, and consequently a greatest distance of 72+2/3 Earth radii. With this method, as the parallax of the Sun decreases (i.e., its distance increases), the minimum limit for the mean distance is 59 Earth radii - exactly the mean distance that Ptolemy later derived.
Hipparchus thus had the problematic result that his minimum distance (from book 1) was greater than his maximum mean distance (from book 2). He was intellectually honest about this discrepancy, and probably realized that especially the first method was very sensitive to the accuracy of the observations and parameters (in fact, modern calculations show that the size of the solar eclipse at Alexandria must have been closer to 9/10 than to the reported 4/5).
Ptolemy later measured the lunar parallax directly (Almagest V.13), and used Hipparchus’ second method with lunar eclipses to compute the distance of the Sun (Almagest V.15). He criticized Hipparchus for making contradictory assumptions, and obtaining conflicting results (Almagest V.11): but apparently he failed to understand Hipparchus' strategy to establish limits consistent with the observations, rather than a single value for the distance. Hipparchus’ results were the best at that time: the actual mean distance of the Moon is 60.3 Earth radii, within his limits from book 2.
Theon of Smyrna wrote that according to Hipparchus, the Sun is 1,880 times the size of the Earth, and the Earth twenty-seven times the size of the Moon; apparently this refers to volumes, not diameters. From the geometry of book 2 it follows that the Sun is at 2,550 Earth radii, and the mean distance of the Moon is 60½ radii. Similarly, Cleomedes quoted Hipparchus’ ratio for the sizes of the Sun and Earth as 1050:1; this leads to a mean lunar distance of 61 radii. Apparently Hipparchus later refined his computations, and derived accurate single values that he could use for predictions of solar eclipses.
See [Toomer 1974] for a more detailed discussion.
Pliny (Naturalis Historia II.X) tells us that Hipparchus demonstrated that lunar eclipses can occur five months apart, and solar eclipses seven months (instead of the usual six months); and the Sun can be hidden twice in thirty days, but as seen by different nations. Ptolemy discussed this a century later at length in Almagest VI.6. The geometry, and the limits of the positions of Sun and Moon when a solar or lunar eclipse is possible, are explained in Almagest VI.5. Hipparchus apparently made similar calculations. The result that two solar eclipses can occur one month apart is important, because this conclusion can not be based on observations: one eclipse is visible on the northern and the other on the southern hemisphere, and the latter was inaccessible to the Greek.
Prediction of exactly when and where a solar eclipse will be visible requires a solid lunar theory and proper treatment of the lunar parallax. Hipparchus was probably the first to make this prediction. In order to do this accurately, spherical trigonometry is required, but Hipparchus may have made do with planar approximations. He may have discussed these things in Peri tes kata platos meniaias tes selenes kineseoos ("On the monthly motion of the Moon in latitude"), a work mentioned in the Suda.
Pliny also remarks that "he also discovered for what exact reason, although the shadow causing the eclipse must from sunrise onward be below the earth, it happened once in the past that the moon was eclipsed in the west while both luminaries were visible above the earth." (translation H. Rackham (1938), Loeb Classical Library 330 p.207). Toomer (1980) argued that this must refer to the large total lunar eclipse of November 26, 139 B.C.E., when over a clean sea horizon as seen from the citadel of Rhodes, the Moon was eclipsed in the northwest just after the Sun rose in the southeast. This would be the second eclipse of the 345-year interval that Hipparchus used to verify the traditional Babylonian periods, and puts a late date to the development of Hipparchus' lunar theory. We do not know what "exact reason" Hipparchus found for seeing the Moon eclipsed while apparently it was not in exact opposition to the Sun. Parallax lowers the altitude of the luminaries; refraction raises them, and from a high point of view the horizon is lowered.
Astronomical instruments and astrometry
Hipparchus and his predecessors used simple instruments, such as the gnomon, the astrolabe, and the armillary sphere for astronomical calculations and observations. Hipparchus is credited with the invention or improvement of several astronomical instruments, which were used for a long time for naked-eye observations. According to Synesius of Ptolemais (fourth century) he made the first astrolabion; this may have been an armillary sphere (which Ptolemy however says he constructed, in Almagest V.1); or the predecessor of the planar instrument called astrolabe (also mentioned by Theon of Alexandria). With an astrolabe Hipparchus was the first to be able to measure the geographical latitude and time by observing stars. Previously this was done during the day by measuring the shadow cast by a gnomon, or with the portable instrument known as scaphion.
Ptolemy mentions (Almagest V.14) that he an instrument similar to Hipparchus’, called a dioptra, to measure the apparent diameter of the Sun and Moon. Pappus of Alexandria described it (in his commentary on the Almagest of that chapter), as did Proclus (Hypotyposis IV). It was a four-foot rod with a scale, a sighting hole at one end, and a wedge that could be moved along the rod to exactly obscure the disk of Sun or Moon.
Hipparchus also observed solar equinoxes, which may be done with an equatorial ring: its shadow falls on itself when the Sun is on the equator (i.e., in one of the equinoctial points on the ecliptic), but the shadow falls above or below the opposite side of the ring when the Sun is south or north of the equator. Ptolemy quotes (in Almagest III.1 (H195)) a description by Hipparchus of an equatorial ring in Alexandria; a little further he describes two such instruments present in Alexandria in his own time.
Hipparchus applied his knowledge of spherical angles to the problem of denoting locations on the Earth's surface. Before him a grid system had been used by Dicaearchus of Messana (Messina, Italy), but Hipparchus was the first to apply mathematical rigor to the determination of the latitude and longitude of places on the Earth. Hipparchus wrote a critique in three books on the work of the geographer Eratosthenes of Cyrene (third century B.C.E.), called Pròs tèn 'Eratosthénous geografían ("Against the Geography of Eratosthenes"). It is known to us from Strabo of Amaseia, who in his turn criticized Hipparchus in his own Geografia. Hipparchus apparently made many detailed corrections to the locations and distances mentioned by Eratosthenes. It seems he did not introduce many improvements in methods, but he did propose a means to determine the geographical longitudes of different cities at lunar eclipses (Strabo Geografia 7). A lunar eclipse is visible simultaneously on half of the Earth, and the difference in longitude between places can be computed from the difference in local time when the eclipse is observed. His approach would give accurate results if it were correctly carried out, but the limitations of timekeeping accuracy in his era made this method impractical.
Late in his career (about 135 B.C.E.) Hipparchus compiled a star catalogue. He also constructed a celestial globe depicting the constellations, based on his observations. His interest in the fixed stars may have been inspired by the observation of a supernova (according to Pliny), or by his discovery of precession (according to Ptolemy, who says that Hipparchus could not reconcile his data with earlier observations made by Timocharis and Aristyllos).
Previously, Eudoxus of Cnidus in the fourth century B.C.E. had described the stars and constellations in two books called Phaenomena and Entropon. Aratus wrote a poem called Phaenomena or Arateia based on Eudoxus' work. Hipparchus wrote a commentary on the Arateia, his only preserved work, which contains many stellar positions and times for rising, culmination, and setting of the constellations, and these are likely to have been based on his own measurements.
Hipparchus made his measurements with an equatorial armillary sphere, and obtained the positions of maybe about 850 stars. It is disputed which coordinate system he used. Ptolemy's catalogue in the Almagest, which is derived from Hipparchus' catalogue, is given in ecliptic coordinates. However Delambre in his Histoire de l'Astronomie Ancienne (1817) concluded that Hipparchus knew and used the equatorial coordinate system, a conclusion challenged by Otto Neugebauer in his A History of Ancient Mathematical Astronomy (1975). Hipparchus seems to have used a mix of ecliptic coordinates and equatorial coordinates: in his commentary on Eudoxus of Cnidus he provides the polar distance (equivalent to the declination in the equatorial system) and the ecliptic longitude.
Hipparchus' original catalogue is no longer in existence. However, an analysis of an ancient statue of Atlas (the “Farnese Atlas”) supporting a globe, published in 2005, shows stars at positions that appear to have been determined using Hipparchus' data. .
As with most of his work, Hipparchus’ star catalogue was adopted and expanded by Ptolemy. It has been strongly disputed how much of the star catalogue in the Almagest is due to Hipparchus, and how much is original work by Ptolemy. Statistical analysis (by Bradly Schaeffer, and others) shows that the classical star catalogue has a complex origin. Ptolemy has even been accused of fraud for stating that he re-measured all stars; many of his positions are wrong and it appears that in most cases he used Hipparchus' data and precessed them to his own epoch three centuries later, but using an erroneously small precession constant.
The work begun by Hipparchus has had a lasting heritage, and was added to much later by Al Sufi (964), and by Ulugh Beg as late as 1437. It was superseded only by more accurate observations after invention of the telescope.
Hipparchus ranked stars in six magnitude classes according to their brightness: he assigned the value of one to the twenty brightest stars, to weaker ones a value of two, and so forth to the stars with a class of six, which can be barely seen with the naked eye. A similar system is still used today.
Precession of the Equinoxes (146 B.C.E.-130 B.C.E.)
Hipparchus is perhaps most famous for having discovered the precession of the equinoxes. His two books on precession, On the Displacement of the Solsticial and Equinoctial Points and On the Length of the Year, are both mentioned in the [Almagest of Claudius Ptolemy. According to Ptolemy, Hipparchus measured the longitude of Spica and other bright stars. Comparing his measurements with data from his predecessors, Timocharis and Aristillus, he realized that Spica had moved 2° relative to the autumnal equinox. He also compared the lengths of the tropical year (the time it takes the Sun to return to an equinox) and the sidereal year (the time it takes the Sun to return to a fixed star), and found a slight discrepancy. Hipparchus concluded that the equinoxes were moving ("precessing") through the zodiac, and that the rate of precession was not less than 1° in a century.
Ptolemy followed up on Hipparchus' work in the second century C.E. He confirmed that precession affected the entire sphere of fixed stars (Hipparchus had speculated that only the stars near the zodiac were affected), and concluded that 1° in 100 years was the correct rate of precession. The modern value is 1° in 72 years.
Hipparchus and Astrology
As far as is known, Hipparchus never wrote about astrology, the application of astronomy to the practice of divination. Nevertheless the work of Hipparchus dealing with the calculation and prediction of celestial positions would have been very useful to those engaged in astrology. Astrology developed in the Greco-Roman world during the Hellenistic period, borrowing many elements from Babylonian astronomy. Remarks made by Pliny the Elder in his Natural History Book 2.24, suggest that some ancient authors regarded Hipparchus as an important figure in the history of astrology. Pliny claimed that Hipparchus "can never be sufficiently praised, no one having done more to prove that man is related to the stars and that our souls are a part of heaven."
- For general information on Hipparchus see the following biographical articles: G. J. Toomer, "Hipparchus" In Dictionary of Scientific Biography.(1978) 15: 207-224
- A. Jones, "Hipparchus." In Encyclopedia of Astronomy and Astrophysics. (Nature Publishing Group, 2001)
- Modern edition: Karl Manitius (In Arati et Eudoxi Phaenomena, Leipzig, 1894).
- B. E. Schaefer, "Epoch of the Constellations on the Farnese Atlas." Journal for the History of Astronomy 36 (2005): 1-29.
- Lucio Russo. The Forgotten Revolution. Springer, 2004; Italian edition, 1996.
- For more information see G. J. Toomer, "Hipparchus and Babylonian astronomy." In A Scientific Humanist: Studies in Memory of Abraham Sachs, ed. Erle Leichty, Maria deJ. Ellis, and Pamel Gerardi. (Philadelphia: Occasional Publications of the Samuel Noah Kramer Fund, 9, 1988.)
- Franz Xaver Kugler, Die Babylonische Mondrechnung ("The Babylonian lunar computation"), Freiburg im Breisgau, 1900.
- G. J. Toomer, "The Chord Table of Hipparchus and the Early History of Greek Trigonometry." Centaurus 18 (1973): 6-28.
- J. Chapront, M. Chapront Touze, and G. Francou, A new determination of lunar orbital parameters, precession constant, and tidal acceleration from LLR measurements. Astron. Astrophys. 387 (2002): 700-709
- G.J. Toomer, "The Size of the Lunar Epicycle According to Hipparchus." Centaurus 12 (1967): 145-150
- Chapront, J.; M. Chapront Touze, and G. Francou, A new determination of lunar orbital parameters, precession constant, and tidal acceleration from LLR measurements. Astron. Astrophys. 387 (2002): 700-709.
- Jones, A. "Hipparchus." In Encyclopedia of Astronomy and Astrophysics. Nature Publishing Group, 2001.
- Moore, Patrick Moore. Atlas of the Universe. Octopus Publishing Group LTD, 1994. (Slovene translation and completion by Tomaž Zwitter and Savina Zwitter (1999): Atlas vesolja), 225.
- Plato, J. Burnet (Editor). Opera: Volume II: Parmenides, Philebus, Symposium, Phaedrus, Alcibiades I and II, Hipparchus, Amatores. Oxford University Press, 1922. ISBN 978-0198145417
- Plato, W. R. M. Lamb (Translator). Plato: Charmides, Alcibiades 1 & 2, Hipparchus, The Lovers, Theages, Minos, Epinomis. Loeb Classical Library, 1927. ISBN 978-0674992214
- Schaefer , B. E. "The Epoch of the Constellations on the Farnese Atlas and their Origin in Hipparchus's Lost Catalogue." Journal for the History of Astronomy 36 (2005): 1-29.
- Swerdlow, N. M.. "Hipparchus on the distance of the sun." Centaurus 14(1969): 287-305
- Toomer, G.J. "The Size of the Lunar Epicycle According to Hipparchus." Centaurus 12 (1967): 145-150.
- Toomer, G.J. "The Chord Table of Hipparchus and the Early History of Greek Trigonometry." Centaurus 18 (1973): 6-28.
- Toomer, G.J. "Hipparchus on the Distances of the Sun and Moon." Archives for the History of the Exact Sciences 14 (1974): 126-142.
- Toomer, G.J. "Hipparchus." In Dictionary of Scientific Biography 15: 207-224, 1978
- Toomer, G.J.: "Hipparchus' Empirical Basis for his Lunar Mean Motions," Centaurus 24 (1980): 97-109.
- Toomer, G.J. "Hipparchus and Babylonian Astronomy." In A Scientific Humanist: Studies in Memory of Abraham Sachs, ed. Erle Leichty, Maria deJ. Ellis, and Pamel Gerardi. Philadelphia: Occasional Publications of the Samuel Noah Kramer Fund, 9, 1988.
- Edition and translation: Karl Manitius: In Arati et Eudoxi Phaenomena. Leipzig, 1894.
All links retrieved January 9, 2018.
- MacTutor Biography
- Biographical page at the University of Cambridge
- University of Cambridge's Page about Hipparchus' sole surviving work
- Biography of Hipparchus on Fermat's Last Theorem Blog
- David Ulansey about Hipparchus's understanding of the precession
- Schaefer's site on the Farnese Atlas
New World Encyclopedia writers and editors rewrote and completed the Wikipedia article in accordance with New World Encyclopedia standards. This article abides by terms of the Creative Commons CC-by-sa 3.0 License (CC-by-sa), which may be used and disseminated with proper attribution. Credit is due under the terms of this license that can reference both the New World Encyclopedia contributors and the selfless volunteer contributors of the Wikimedia Foundation. To cite this article click here for a list of acceptable citing formats.The history of earlier contributions by wikipedians is accessible to researchers here:
The history of this article since it was imported to New World Encyclopedia:
Note: Some restrictions may apply to use of individual images which are separately licensed. | 0.884338 | 3.365765 |
What's the difference between asteroids, meteoroids, meteors, meteorites and comets?
Meteoroids and meteors
||A celestial body bigger than 10 m orbiting the Sun, mainly between Mars and Jupiter
||Similar to an asteroid, but significantly smaller. Mostly debris of comets, sometimes debris of asteroids.
||A bright tail of light caused by a meteoroid during its atmospheric flight, also called a shooting star or falling star.
||A very bright meteor (brighter than the planet Venus).
||A fireball that explodes during its atmospheric flight, often with visible fragmentation.
||The part of a meteoroid or asteroid that survives the passage through our atmosphere and reaches the Earth's surface.
||A smaller celestial body mainly composed of ice and dust. If a comet approaches the Sun it can generate a tail of gas and/or dust.
An asteroid is a celestial body - composed of rock, metal or a mixture of both - that is orbiting the Sun. Most of them are in the asteroid belt between Mars and Jupiter. Even though there are millions of asteroids with sizes up to more than 500 km (like Pallas and Vesta) they are of no danger to the planet Earth. The biggest body in the asteroid belt - Ceres - is officially not called an asteroid anymore but a dwarf planet
. If you try to envision the asteroid belt don't get fooled by some science fiction films: travelling around in the asteroid belt with your spacecraft doesn't require constant steering in order to avoid crashes with asteroids. The scale of the solar system is so immense that even inside the asteroid belt the average distance between two asteroids is above one million km - or three times the distance between Earth and the Moon.
Asteroid Itokawa, an Apollo asteroid with a length of 500 metres. Credit: JAXA
Some asteroids have very elliptical trajectories, crossing the orbits of the inner planets Mars, Earth or Venus. The cause of these elliptical trajectories could be collisions within the asteroid belt or the gravitational influence of the massive planet Jupiter changing the orbits of some asteroids gradually over time (see orbital resonance
). All asteroids with orbits so eccentric that they cross Earth's orbit are called 'Apollo asteroids', 'Amors' approach the Earth but do not cross Earth's orbit. Apollo asteroids are doomed to sooner or later collide with one of the inner planets, usually within a few million years of their orbit becoming so eccentric. The largest Apollo asteroid - 1866 Sisyphus - has a diameter of about 9 km, similar to the asteroid that caused the Chicxulub event
, the giant meteorite impact that caused the extinction of the dinosaurs. Anyhow, Sisyphus and none of the other big Apollo asteroids will collide with Earth in the next millennia; which doesn't mean that smaller bodies can cause local damage. Many of you will remember the Chelyabinsk event
which took place on the 15th of February 2013. Fortunately no people were killed during this event and today you can even buy a Chelyabinsk meteorite
Meteoroids and meteors
Generally speaking, meteoroids are all the smaller objects in orbit around the Sun. Most of them originate from comets that lose gas and dust when they approach the Sun. Other meteoroids are basically small asteroids. There is no exact diameter that distinguishes an asteroid from a meteoroid. Wikipedia states 10 metres; other trustworthy sites call anything smaller than 1 km a meteoroid. Anyhow, the vast majority of all meteoroids are just a few millimetres and less in size. The smallest and by far the most numerous ones have sizes of small dust particles and are called micrometeoroids; they do not leave any visible trace behind when they enter the Earth's atmosphere.
Perseid meteor shower on August 12, 2012. Image taken by David Kingham in Snowy Range (Wyoming).
The ones about the size of a pebble leave behind a flash of light when they completely vaporise. Most people call this flash a "shooting star" or a "falling star", but more accurately spoken this is a meteor. A meteor is the light that you can see when a small meteoroid enters the Earth’s atmosphere. This normally happens with speeds between 11 and 73 km/s and at altitudes of about 75-120 km. Under a clear sky an observer can see 5 to 10 meteors per hour, especially after midnight when the Earth has rotated so far that the observer's part of the sky is positioned in the direction of the Earth's motion around the Sun. During so called meteor showers the rate of observable meteors per hour can increase significantly. Meteor showers are caused when the Earth crosses higher than usual concentrations of particles that are themselves in an eccentric orbit around the Sun. Since the orbit of these particles is fixed, we encounter this stream every year at the same time - just its density cannot be foreseen. This sometimes leads to sparse meteor showers and sometimes very intense meteor showers with more than 1000 meteors per hour, also called meteor outbursts or meteor storms. The meteors we see can be debris from a comet (> 90% of all meteors we see) or an asteroid. The most famous meteor showers are the Perseids in mid-August (caused by Comet 109P/Swift-Tuttle) and the Leonids (mid-November). The meteors during these meteor showers almost all emerge from the same section of the sky; indeed the meteor showers are named for the constellations from which the meteors appear to originate.
Leonid meteor, image taken during the peak of the 2009 Leonid Meteor Shower (17th November). Credit: Wikipedia.org, user: Navicore.
But what causes the light path of the meteor that we can see in the sky? Smaller meteoroids will be heated by adiabatic compression
until the point when they completely disintegrate. However, the light emission we observe is mainly caused by interactions between evaporated and detached components of the fast moving meteoroid and air molecules. Both the meteoroid atoms and the air molecules ionize during this encounter. When the free electrons recombine with the ionized atoms in the tail of the meteoroid they emit the light that we can observe. The light track can have a length of up to several tens of kilometres and an initial diameter of a few metres. The colour of the meteor is an indicator of the material of the meteoroid; e.g., a yellow colour is caused by iron, a blue-green colour by copper and a red colour by silicate material.
A meteor that is larger and brighter than normal is called a fireball; brighter than the brightest planet in our night sky (Venus). If these fireballs also break apart or explode during their atmospheric flight - sometimes accompanied by considerable audible sounds - they are called a bolide.
Finally, every asteroid or meteoroid that survives its passage through Earth's atmosphere (and this is the rare exception) can be advanced to be called a meteorite. Meteorites are made of rock (stony meteorites
), metal (iron meteorites
) or a mixture of these two materials (stony-iron meteorites
or pallasites). Pallasites form beautiful olivine crystals that are embedded into a metal matrix. Scientists are eager to study meteorites since they are the very first material that was formed in our early solar system, almost 4.6 billion years ago. Sun.org offers genuine meteorites for sale in our meteorite shop
The three main types of meteorites. Credit: Sun.org - www.sun.org, released under CC-BY-SA 3.0
Comet Hartley 2 has a length of about 2 km and a short orbital period of just 6.46 years. CreditNASA/JPL-Caltech/UMD.
Comets are asteroid-like objects which are composed of ice, dust and rocky particles; that's why they are also called 'dirty snowballs'. The sizes of their nuclei vary between a few hundred metres to tens of kilometres in diameter; their visible tails can extend to above 150 million km in length. They originate from outside Neptune's orbit and - like many asteroids and meteoroids - are unmodified remnants of the formation of our solar system about 4.568 billion years ago. When comets approach the Sun the solar radiation and solar winds cause particles to sublimate and detach from the comet, forming a tail of particles which often makes them visible in the night sky even to the naked eye. We say 'sublimate' (a direct phase transition from the solid to the gas phase) since with zero pressure in space, water will not exist in the liquid phase. Anyhow, below its surface there can also be reservoirs of liquid water which can vaporise and feed jets of water vapour.
Comets orbit as around the Sun on elliptical orbits until all of their volatile material has evaporated away. The orbital periods vary between a few years (like comet Encke) and tens of millions of years. While we can observe Halley's Comet every 75 years we need to wait 106 000 more years until we see Comet Panstarrs (C/2011 L4), our guest in 2013, the next time.
The Kuiper belt is the region from where most of the short-period comets derive. Credit:NASA.
Short-period comets mainly originate from the Kuiper belt, a region in the solar system with many millions of icy bodies extending from about 30 AU (about the orbit of Neptune) to 50 AU. If some of these icy bodies get too close to Neptune during their orbit they may be deflected and enter a new, eccentric orbit which will make them become short-period comets. Long-period comets normally originate from the Oort cloud, a region between 2000 AU and 50000 AU (or about one light year) away from the Sun. The Oort cloud consists of trillions of icy objects with diameters above 1 km. With these huge numbers we can be sure that there will be no shortage of comets visiting the inner part of the solar system in the future. But what causes these icy objects in the Oort cloud to leave their stable orbit and approach the inner part of the solar system? Without any "push" they would certainly continue orbiting in the Oort cloud forever. But gravitational perturbations of nearby passing stars and the galactic tide can cause these comets to change their trajectory around the Sun and approach the inner parts of the solar system. The star Gliese 710 will approach within a distance of just 1 light year from the Sun in about 1.4 million years, scratching the Oort cloud and causing many objects to change their trajectories around the Sun.
Comet Lovejoy. This image is taken from the International Space Station (ISS) on December 22, 2011. At the bottom of the image you can see Earth's atmosphere. Credit: Dan Burbank (ISS Expedition 30, NASA)
Comets from the Kuiper belt tend to orbit the Sun within the plane of the solar system because the Kuiper belt itself is aligned with the plane of the solar system. Comets from the Oort cloud can arrive from all different directions since the Oort cloud has a spherical shape. A comet's tail is caused by gas and dust particles that are sublimated and/or vaporised by sunlight and then blown away by the solar wind. The tail always streams out in the direction opposite to the Sun, but it doesn’t arise until the comet enters the inner parts of the solar system (somewhere between Mars and Jupiter), so that the sunlight can sufficiently heat up the comet.
All text and articles published by Sun.org are licensed under a Creative Commons Attribution-ShareAlike 4.0 International | 0.89932 | 3.796643 |
Happy Intercalary Day! Say what? That’s actually just a fancy way of saying Happy Leap Day, which is today, February 29. But you already knew that, right?
But, did you know a non-leap year is called a common year and has 365 days while a leap year has 366? Okay, you knew that too. Did you know, though, that a leap year occurs every four years? Okay fine, you’re on top of that too. But, do you know why? Gotcha? Maybe?
Well, a leap year happens in order to help synchronize the calendar year with the solar year, which is the length of time it takes the earth to complete its orbit around the sun. The calendar we use is called the Gregorian calendar and was put into place by Pope Gregory XIII in 1582. On this calendar, every year divisible by four has an extra day and is called a “Leap Year.” Century years are the exception to the four year rule though, as they must be divisible by 400 to be Leap Years. This is why the year 2000 was a Leap Year but 1900 wasn’t and why 2400 will be one but not 2100.
But what’s in the name “leap?”
The name is thought to come from the fact that, while a fixed date in the Gregorian calendar normally advances one day of the week from one year to the next, the day of the week in the 12 months following a Leap Year will advance two days, thus “leaping” over one of the days.
But why always in February?
Some historians credit Julius Caesar way back when he took power and reconfigured the then Roman calendar. He aligned the length of a year with the sun, giving each year 365 days and for reasons unknown he left February at 28 days. Others say the month was selected kinda randomly and it just stuck.
Okay, so what happens if you’re born on a Leap Day?
Codes vary state-by-state as to when a leap baby or “leapling” celebrates his or her birthday, but most consider March 1 as the day. Interestingly, there is a 1 in 1,500 chance of being born on a leap day and babies born on one are thought to have special talents according to astrologers.
Other myths and legends about a Leap Year and Leap Day in particular include the Irish “Bachelor’s Day” legend that St. Brigid opened up the gates for women to propose marriage to men on a Leap Day after she struck a deal with St. Patrick as a way to balance the traditional roles of men and women in society, much like a leap day adds balance to the calendar. Boy was she a woman ahead of her time! This tradition is still occasionally observed in England but in neighboring Scotland February 29 is often considered as unlucky as Friday the 13th.
Coincidentally, Leap Years almost always coincide with U.S. election years, as is the case this year, and often times with Olympic years as well. The next three leap years will be 2024, 2028, and 2032.
If you’re looking for a way to celebrate today’s Leap Day, what better way than with the official Leap Day Cocktail? Invented by bartender Harry Craddock of London’s tony Savoy Hotel in 1928, it is considered a martini-like drink and is said to have been responsible for more proposals than any cocktail ever mixed according to the “Savoy Cocktail Book.” Here is the original recipe:
Craddock’s Leap Day Cocktail
1 dash lemon juice
1/6 Grand Marnier
1/6 sweet vermouth
Shake, serve, garnish with a lemon peel.
Enjoy and Happy Leap Day! | 0.825618 | 3.046232 |
If scientists are looking for E.T. in space, they may want to consider a variable that could be harmful to all of humanity — carbon monoxide.
A new study suggests that the poisonous gas, which prevents blood from carrying oxygen to vital parts of the body, could be a promising “biosignature” for extraterrestrial life and scientists should consider it, despite its potential for harm.
“That means we could expect high carbon monoxide abundances in the atmospheres of inhabited but oxygen-poor exoplanets orbiting stars like our own sun,” said Timothy Lyons, one of the study’s co-authors, in a statement. “This is a perfect example of our team’s mission to use the Earth’s past as a guide in the search for life elsewhere in the universe.”
The study, published in the Astrophysical Journal, looked at two scenarios: the first looked at the history of the Earth, which had a very different chemical composition three billion years ago, with significantly more carbon monoxide in the atmosphere than there is today.
The model revealed that an ancient version of Earth could have supported as much as 100 parts per million of carbon monoxide, or several times greater than the parts-per-billion traces of the gas in the atmosphere today.
The second scenario may be even more favorable for carbon monoxide as a biosignature — red dwarfs, such as Proxima Centauri, the star nearest the Sun, could have exoplanets that are rich in oxygen and also contain an “abundance of carbon monoxide,” ranging from hundreds of parts-per-million to several percent.
“Given the different astrophysical context for these planets, we should not be surprised to find microbial biospheres promoting high levels of carbon monoxide,” the study’s lead author, Edward Schwieterman, said in the statement. “However, these would certainly not be good places for human or animal life as we know it on Earth.”
In January, a similar study suggested exoplanets rich in oxygen may not necessarily contain extraterrestrial life, despite it being a key component for life on Earth.
One near-term area of hope for researchers looking for extraterrestrial life is the upcoming launch of the James Webb Space Telescope.
Scheduled to launch in March 2021, NASA says it will “study every phase in the history of our Universe, ranging from the first luminous glows after the Big Bang, to the formation of solar systems capable of supporting life on planets like Earth, to the evolution of our own Solar System.” | 0.809742 | 3.739288 |
Discover the cosmos! Each day a different image or photograph of our fascinating universe is featured, along with a brief explanation written by a professional astronomer.
2020 January 11
Explanation: Near the outskirts of the Small Magellanic Cloud, a satellite galaxy some 200 thousand light-years distant, lies 5 million year young star cluster NGC 602. Surrounded by natal gas and dust, NGC 602 is featured in this stunning Hubble image of the region, augmented by images in the X-ray by Chandra, and in the infrared by Spitzer. Fantastic ridges and swept back shapes strongly suggest that energetic radiation and shock waves from NGC 602's massive young stars have eroded the dusty material and triggered a progression of star formation moving away from the cluster's center. At the estimated distance of the Small Magellanic Cloud, the Picture spans about 200 light-years, but a tantalizing assortment of background galaxies are also visible in this sharp multi-colored view. The background galaxies are hundreds of millions of light-years or more beyond NGC 602.
Authors & editors:
Jerry Bonnell (UMCP)
NASA Official: Phillip Newman Specific rights apply.
A service of: ASD at NASA / GSFC
& Michigan Tech. U. | 0.843079 | 3.123585 |
(Left) A graph charting the depth of the Hellas depression at different points, and a topographic map of the depression. (Right) A graph charting the depth of the Galaxias Fossae depression at different points, and a topographic map of the depression. Joseph Levy/NASA
A strangely shaped depression on Mars could be a new place to look for signs of life on the Red Planet, according to a University of Texas at Austin-led study. The depression was probably formed by a volcano beneath a glacier and could have been a warm, chemical-rich environment well suited for microbial life.
The findings were published this month in Icarus, the International Journal of Solar System Studies.
“We were drawn to this site because it looked like it could host some of the key ingredients for habitability — water, heat and nutrients,” said lead author Joseph Levy, a research associate at the University of Texas Institute for Geophysics, a research unit of the Jackson School of Geosciences.
The depression is inside a crater perched on the rim of the Hellas basin on Mars and surrounded by ancient glacial deposits. It first caught Levy’s attention in 2009, when he noticed crack-like features on pictures of depressions taken by the Mars Reconnaissance Orbiter that looked similar to “ice cauldrons” on Earth, formations found in Iceland and Greenland made by volcanos erupting under an ice sheet. Another depression in the Galaxias Fossae region of Mars had a similar appearance.
“These landforms caught our eye because they’re weird looking. They’re concentrically fractured so they look like a bulls-eye. That can be a very diagnostic pattern you see in Earth materials,” said Levy, who was a postdoctoral researcher at Portland State University when he first saw the photos of the depressions.
But it wasn’t until this year that he and his research team were able to more thoroughly analyze the depressions using stereoscopic images to investigate whether the depressions were made by underground volcanic activity that melted away surface ice or by an impact from an asteroid. Study collaborator Timothy Goudge, a postdoctoral fellow at the institute, used pairs of high-resolution images to create digital elevation models of the depressions that enabled in-depth analysis of their shape and structure in 3-D. Researchers from Brown University and Mount Holyoke College also participated in the study.
“The big contribution of the study was that we were able to measure not just their shape and appearance, but also how much material was lost to form the depressions. That 3-D view lets us test this idea of volcanic or impact,” Levy said.
The analysis revealed that both depressions shared an unusual funnel shape, with a broad perimeter that gradually narrowed with depth.
“That surprised us and led to a lot of thinking about whether it meant there was melting concentrated in the center that removed ice and allowed stuff to pour in from the sides. Or if you had an impact crater, did you start with a much smaller crater in the past, and by sublimating away ice, you’ve expanded the apparent size of the crater,” Levy said.
After testing formation scenarios for the two depressions, researchers found that they probably formed in different ways. The debris spread around the Galaxias Fossae depression suggests that it was the result of an impact — but the known volcanic history of the area still doesn’t rule out volcanic origins, Levy said. In contrast, the Hellas depression has many signs of volcanic origins. It lacks the surrounding debris of an impact and has a fracture pattern associated with concentrated removal of ice by melting or sublimation.
The interaction of lava and ice to form a depression would be an exciting find, Levy said, because it could create an environment with liquid water and chemical nutrients, both ingredients required for life on Earth. He said that the Hellas depression and, to a lesser extent, the Galaxias Fossae depression, should be kept in mind when looking for habitats on Mars.
Gro Pedersen, a volcanologist at the University of Iceland who was not involved with the study, agrees that the depressions are promising sites for future research.
“These features do really resemble ice cauldrons known from Earth, and just from that perspective they should be of great interest,” Pedersen said. “Both because their existence may provide information on the properties of subsurface material — the potential existence of ice — and because of the potential for revealing ice-volcano interactions.”
Joseph S. Levy, Timothy A. Goudge, James W. Head, Caleb I. Fassett. Candidate volcanic and impact-induced ice depressions on Mars. Icarus, 2016; DOI: 10.1016/j.icarus.2016.10.021 | 0.833939 | 3.863985 |
What would life on Mars look like? Would we be able to live on the surface, or have to hide underground from all the solar radiation Mars gets exposed to? Would we be able to terraform it?
The Mars You Know:
Ever felt like getting off this planet? Well, consider Mars… 4th Rock from the Sun. It can be as close as 56 million km (34.8 million miles) to us. It can also be as far as 401 million km (250 million miles) away. Mars is about fifty three percent of the size of Earth, making it the second smallest planet in our solar system (after Mercury).
Mars is named for the Roman god of war. The city of Cairo, in Egypt, is actually named after Mars, allegedly because the planet was rising on the day that Cairo was founded. The first spacecraft to Mars was in 1965, and was called the Mariner 4.
Mars has two moons, Phobos and Deimos. It’s also home to the largest recorded mountain in the solar system, and the largest recorded dust storms.
Mars and the Earth have about the same amount of land mass. Mars gets its distinctive red color from iron-rich minerals covering its surface. The temperature on Mars can fall to a low of -153 degrees Celsius (–225 degrees Fahrenheit) and rise to a high of 20 degrees Celsius (70 degrees Fahrenheit).
Various discoveries throughout the years suggest that Mars may have had life at some point. In 2014, NASA’s Curiosity Rover discovered pockets of methane, which they believe suggested that Mars may have had some sort of life at some point.
Scientists have also found evidence of water and other necessities for human life present on the planet. However, these ancient oceans would provide around one percent of the water present in Earth’s oceans. There are other features of Earth which also used to be present on Mars. There is evidence that Mars used to have polar ice caps.
So, what would happen if we fled to the red planet?
What If We All Moved To Mars?
Even if you jumped into the fastest spacecraft ever launched from Earth, getting there would take anywhere from 40 days to 9.5 months, depending on the position of the planets. And after all that time in space, you’d finally see dry and lifeless Mars on the horizon. But would you be able to survive there? What would you need to survive on Mars anyway?
First off, you’d have to figure out how to produce oxygen to breathe. The Martian atmosphere is very thin and it’s 95% carbon dioxide. You wouldn’t be able to just bring all the oxygen you’d need to survive, but you could extract it from the CO2 with machines like NASA’s “MOXIE.”
Not only would that provide you and other Martian settlers with breathable air, but also supply you with liquid oxygen propellant. That’s the stuff you’d need to lift a rocket off Mars – in case you decided to return to Earth. There’s no soil on Mars to grow food in. Instead, you’d use hydroponics – cultivating your crops in a mineral and nutrient solution, no soil required.
Of course, without running water on the surface, your colony would only be able to grow about 20% of the food you’d need. The rest of it you’d have shipped in from Earth. But don’t expect fresh meat – all your food would come dried.
Where Would We Live?
Along with the other settlers, you’d probably live in inflatable pressurized buildings. But it’s more likely that you’d go underground. Because Mars has no global geomagnetic field, and since its atmosphere is so thin, radiation levels in the orbit above Mars are 2.5 times higher than at the International Space Station. That is too much solar radiation for humans to bear.
Forget about suntanning. The Sun would appear just half as big as it does from Earth. And if you want to go outside and return alive, you’d need a spacesuit to make up for the near-absent atmospheric pressure and to block radiation.
Your suit would also keep you warm, which is important because temperatures on Mars are very low. The coldest winter on Earth is paradise compared to the average Martian winter. Temperatures would be as low as -55 °C (-67 °F). Even colder at the poles, where the temperatures can drop to a freezing -153 °C (243 °F).
A day on Mars is just 40 minutes longer than a day on Earth. A year on Mars would be almost twice as long, though. If you lived in the northern hemisphere, you’d enjoy seven months of spring and six months of summer. Then there would be a five-months long autumn and another four months of winter.
And not only are the temperatures there low, they also can change dramatically within a week. These variations often result in powerful dust storms. They wouldn’t harm you, but would clog all your electronics. Facetiming with somebody from home would be next to impossible, because whatever you say would take about 15 minutes to get to Earth.
Remember too, that the gravity on Mars is about one third of the Earth’s. You’d need to learn how to walk again. Still want to move to the red planet? Well, your . best bet is to wait until the first human colonies head there to terraform the planet – to make it just like the one they came from.
Ice, Ice, Baby:
They’d import ammonia ice from the atmospheres of other planets to heat Mars up a little. The heat would convert the dry ice at the Martian north pole into gas and give the planet an atmosphere. Still unbreathable for us, but at least it would be enough to create atmospheric pressure so that you could finally take off your spacesuit.
Then they’d extract water from the vast reserves of water-ice locked away beneath the Mars’ surface. Water vapor would make the atmosphere thicker and thicker. Eventually, you’d see it raining and snowing on Mars. And after maybe a thousand years, there’d be enough oxygen for humans to breathe. The planet re-engineering would be complete.
Is living on Mars is something you’d like to try? Or would you rather preserve what we have here on Earth?
- Your kids might live on Mars. Here’s how they’ll survive.
- HOW DO WE COLONIZE MARS?
- Populating a Mars Base Will Be Dangerously Unsexy
- How Long Does It Take to Get to Mars?
- MARS FACTS
- Mars Facts: Life, Water and Robots on the Red Planet
- Fun Facts About Mars
- 10 amazing facts you probably didn’t know about the Red Planet
- 12 Awesome Facts About Mars That Will Make You Love The Red Planet Even More
- Mars Facts
- Featured Image Source:D Mitriy on Wiki Commons | 0.814141 | 3.129534 |
Last month, for my day job, I was writing about helium. Helium is the second most abundant element in the Universe (after hydrogen) and the lightest of the noble gases (which point blank refuse to react with almost everything). Helium is produced by radioactive decay, deep in the Earth, but it’s so light that it filters up to the surface, rises through the atmosphere, and escapes into space. Along the way it can get caught up in some geological features, and most of the helium we use is a by-product of natural gas extraction. It has a surprising number of uses, beyond filling balloons and giving people squeaky voices, and gets used a lot for chilling really cool (-268.9 °C/4.22 K) science experiments.
I was writing about helium in its chilling capacity mostly, but whilst I was doing my research I came across plenty of stories of one of its other abilities – lifting things to the edge of space. Well, not really to the edge of space, just quite high in the stratosphere. A toy balloon will burst at an altitude of about 10 km; weather balloons can get to 30 km. It might not be outer space, but you can get some pretty cool pics from up there, and people do.
What I love about this is that kids have been sending things ‘into space’ on helium balloons (makes for an interesting science project!), and people who are allegedly more grown up have been sending some daft things, too.
My favourite story is of two intrepid bears, called MAT and KMS, who became the world’s first teddynauts in 2008. Whisked from a shelf in Mothercare and kitted out with custom made spacesuits by local school children, the teddynauts were propelled into the space flight annals of fame by a weather balloon made by Cambridge University’s Space Flight science club, enduring temperatures of -35°C and reaching 30,000 metres. After successfully completing their mission to monitor weather conditions above the Earth, the pair parachuted back down and made a soft landing near Ipswich, 50 miles from their launch pad.
In fact, four bears took part in the mission, but it seems as though the other two were never named. History does not record what happened to the bears after their 15 minutes of fame, but I hope they are enjoying a thoroughly cuddly retirement.
In April 2016, another intrepid cuddly toy was launched. Sam the Space Dog reached an altitude of 15.5 miles (25 km) after launching from the Midland Hotel as the climax of a project by Morecambe Bay Primary School. Unfortunately, Sam became detached from the helium balloon during his descent, and although the equipment was recovered, Sam was never found 🙁 But a Sam clone made a more successful second flight the following year.
In April 2012, a group of Californian students sent a rubber chicken to an altitude of 120,000 ft as part of a project to test the levels of radiation exposure during a solar storm. At the time, Camilla Corona was already well known among space enthusiasts as a mascot of NASA’s Solar Dynamics Observatory (SDO), and had more than 20,000 followers on Twitter, Facebook, and Google+. Camilla wore a pair of radiation badges, the same kind medical technicians and nuclear workers wear to assess their exposure, and a space suit knitted by Cynthia Coer Butcher from Blue Springs. She flew twice – once on 3 March before the radiation storm and again on 10 March while the storm was in full swing – to give the students a basis for comparison.
Astrochicken Camilla was attached to the mission’s payload, a modified lunchbox filled with instruments – four cameras, a cryogenic thermometer, and two GPS trackers. Seven insects and two-dozen ‘Sunspot’ sunflower seeds (Helianthus annuus) were also sent up to test their response to near-space travel. The students planted the sunflower seeds to see if they produced flowers that are different than those grown from the seeds that stayed on Earth (but I can’t find a record of the results…). None of the insects survived the mission, so the students pinned their corpses to a black “Foamboard of Death”, a rare collection of bugs that have nearly made it to space.
People seem to love sending edible things into space. In December 2016, ahead of the World Pie Eating Championship, Sheffield-based space enthusiasts attached a camera and tracking equipment a meat and potato pie in Wigan and sent it to the skies on a weather balloon. At the time, it was believed to be the first pie to be launched into the stratosphere, and the alleged aim was to see if its journey up to 30 km changed its molecular structure and made it quicker to eat.
Its flight lasted around two hours, and the pie touched down 38 miles from its launch site, near the Forest of Bowland. It was reported as landing “mostly intact”, but investigations showed its structure was actually different, and it wasn’t eaten due to health and safety concerns.
A Bakewell pudding launched in June 2018 was lost in space. Pupils tracked it to 52,500 ft (16,000 m) over Saxilby, near Lincoln, before contact was lost. They raised about £1,600 for the Guide Dogs for the Blind as part of the experiment, by asking local firms to sponsor them. The Bakewell Pudding is an upper-crust version of the more modern Bakewell Tart, and if you want to make your own (for launch, or lunch), here’s a recipe.
In February 2015, students of Earth to Sky Calculus flew varieties of garden vegetables and flowers (turnips, cherry and beefsteak tomatoes, sweetcorn, green beans, bell peppers, jalapeño peppers, carrots, radishes, pumpkins, broccoli, sunflowers, cosmos, petunias and helichrysum) to the edge of space. The seeds experienced temperatures as low as -63°C and air pressures similar to those on Mars, and received 40 times the dose of cosmic rays they would have on Earth. Identical seeds remained on Earth as control samples, with the intention that the students would grow both sets side-by-side to see whether the trip had affected the viability, colour, size or taste of the plants. (Again, I don’t think they published their results.)
This seedy space mission was partly a fundraising exercise for the students, who flew about 80 packets of seeds and sold them off with control samples for people who wanted to try growing space seeds at home.
Earth to Sky Calculus continues to send exciting things into space, including bananas:
And an orchid:
Speaking of flowers, in 2017 artist azuma makoto sent approximately 100 different kinds up into the stratosphere in three different bouquets, as part of a series of works placing elements of botanical life in naturally impossible situations. They were exposed to temperatures of about -43.9℃, climbing to an average altitude of 95,555 feet during 2 hours of flight. Prior to this, in 2015, the artist had sent a bonsai tree into space.
This is just the tip of the iceberg as far as things that have been sent skywards on helium balloons, and some of them are definitely not safe for work. Far more sensible and informative are NASA’s stratosphere experiments, which are showing that some of Earth’s microbes could potentially hitch a ride on a spacecraft and survive long enough to establish themselves on Mars. | 0.841744 | 3.091659 |
Choice of orbit
The selection of a sun-synchronous orbit was of primary importance and has driven the satellite’s physical configuration. The total altitude range, within a few tens of kilometres of 800 km, was also critical to the design. Apart from this, there was a certain degree of freedom in the choice of parameters. Many of the choices were examined during the ERS-1 mission preparation and the concept of the multidisciplinary orbit, with a 35-day cycle, evolved. Envisat flies this same high-inclination, sun-synchronous, near-circular orbit with the same ground track.
The orbit maintenance requirements are that the deviation of the actual ground track from the nominal one is kept below 1 km and that the mean local nodal crossing time matches the nominal one to within five minutes. The orbit maintenance strategy aims for minimum disturbance of the payload operation. In-plane manoeuvres are used for altitude adjustment to compensate for the effects of air-drag. This altitude decay affects the ground-track repeatability, mainly in the equatorial regions. The frequency of these manoeuvres is determined by the rate of orbital decay, which in turn is determined by the air density, and this is a function of solar activity. The nominal rate for these in-plane manoeuvres is twice a month. They do not interrupt the operations of most sensors. Out-of-plane corrections are used to rectify the steady drift of inclination mainly caused by solar and lunar gravity perturbations. The solar wind also influences inclination, but its contribution is typically an order of magnitude smaller than the one made by solar and lunar gravity. Inclination drift degrades ground-track maintenance at high latitudes. The drift rate does not depend on air density and corrections are required every few months. As they are out-of-plane they require a 90 degree rotation of the spacecraft, to align the thrusters with the required thrust direction, so these manoeuvres are performed in eclipse to avoid the risk of optical sensors viewing the sun.
|Envisat orbit Heavens Above|
|Semi-major axis||7159.5 km|
|Reference altitude (equatorial)||799.8 km|
|Nodal period||100.59 min|
|Repeat cycle||35 days|
|Number of passes per cycle||1002|
|Ground track separation at Equator||80 km|
|Acute angle at Equator crossings|
|Longitude at Equator of pass 1|
|Orbital velocity||7.45 km/s|
|Ground scanning velocity| | 0.836913 | 3.780885 |
Give yourself to the Dark Side. It is the only way you can save your friends. – D. Vader
Lisa Randall, a Harvard Science professor, member of the National Academy of Sciences, named one of the 100 Most Influential People by Time Magazine in 2007, and author of three previous books, likes to think big. She also likes to think small. Her areas of expertise are particle physics and cosmology, which certainly covers a range. The big look she offers here is a cosmological take on not only how it came to pass that a large incoming did in the dinosaurs 66 million years ago, but why such decimations of life on Earth arrive with some (on a cosmological scale) regularity. Her explanation has to do with dark matter. It makes for an interesting tale, and offers an excellent example of how the scientific method (how Daniel Day Louis might play Louis Pasteur?) approaches problem-solving. It is a fascinating read that is at times wondrously accessible and at others like trying to bat away a swarm of meteoroids.
As with most good communicators of science. Randall relies on metaphor, and some of hers are quite good. My favorite compared methods of detecting dark matter to detecting the presence of [insert name of your favorite A-list celebrity here]. You can tell that there is something going on, without actually having to see the celebrity, because you can see swarms, gaggles, pods and packs of paparazzi clumping around the object of their lenses as he/she/it walks/primps/flees down the street. Dark matter affects the things around it too, and it is by measuring those effects that we can tell it is there, even though it remains…you know…dark.She addresses some cosmological questions and offers up the answers that the best current theories provide. One example is that the rotational velocity of stars should be sufficient to make them literally spin out of their galaxies, and yet they don’t. Something must be keeping them in place. Care to guess? There are more like this. They vary in Wow-Cool! levels. Randall takes us from a look at how we know dark matter is out there, and its characteristics, to an overview of our solar system. This is more interesting than a science class slide show of the 8 (or 9 if you are my age) planets circling around our sun. (Well, maybe I should say your sun, but I don’t really want to get into that) There is a lot of other material cruising around out there, and it is significant, as in Please, oh please, do not come crashing into our planet, pretty please.
Path of the New Horizons spacecraft into the Kuiper Belt – from NASA
The Kuiper Belt, a group of clumped asteroids, not an award for the baddest Kuiper, and the Oort Cloud (not where Obchestvo Remeslenogo Truda keeps its data) for example, are parts of our solar system, and move through inter-stellar space along with the sun and planets.
The Oort Cloud – From NASA
You might think of the sundry members of the Solar System as a family all stuffed into one very, very large car of the Wonder Wheel in Coney Island. Once everyone is in, the whole crew moves through space (or circle in this instance) as one. But what if there were another Wonder Wheel, one that was made, not of the dense ordinary matter, but of the much thinner dark sort. Let’s say that it is not vertical but does its spinning thing at an angle. And let’s say it intersected our Wonder Wheel at one point. And every so often, say every thirty some odd million years, the car our solar system is in intersects the material in that other Wonder Wheel. The result could be unpleasant. The big stuff would probably be ok, our sun, the planets, but some of the smaller bits, say rocks in the Oort cloud and Kuiper Belt, might get knocked out of their usual paths. And voila! Fireworks! Big incomings headed our way yet again.
Well, that’s the scoop. I am not giving anything away by laying it out. The value of the book lies in showing how theories are examined, tested and accepted or discarded, the scientific method in action.
But I would not want to make you think the orbit you take while reading Dark Matter and the Dinosaurs is all clear sailing. There are incomings you have to contend with. It is always takes a bit more effort to absorb material when much of it is new to the reader, particularly when there are many new words, acronyms and concepts being thrown at you. I confess that there were points in reading this book when my eyes glazed over. It felt like I was reading a list in a foreign language. My mind went a bit dark in the chapter on how galaxies are born and in a couple of particle physics chapters near the end. On the other hand, enough of the early discussion of dark matter was utterly fascinating. When Randall writes of a second, post-Big-Bang expansion of the universe, it was news to me. I quite enjoyed the tour through our solar system, one that included parts we do not usually think of. And if you ever wondered about how three words are used, the answer is here. Meteors are what we see streaking across the sky. We call them meteoroids if they make it to the ground. (I hereby promise that no meteor will touch the Earth on my watch) In fact any alien object hitting Earth is a meteoroid. (Even Asgardians?) Meteorites are the detritus of meteoroid impact. There is a nifty piece on how we define what is and is not a planet, and some amazing intel on what unexpected materials asteroids and comets might have brought to the Earth over the history of our planet, and another piece on how craters are created. And did you know that there is a multi-national (as in countries not corporations) organization that was set up to watch the skies for the next big thing? These and more such nuggets make the journey with Randall worth the occasional eye-glaze.
And if you are worried about The Big One wiping us out, don’t. We will see to that ourselves long before a big rock does the job for us. The current rate of species extinction is comparable to the one that took place 250 million years ago, the Permian-Triassic extinction. In that one 90% of species were wiped out, including insects. There is always hope that we will, over a period of millions of years, figure out how to keep large floaters from making a mess of our earthly garden. With Dark Matter and the Dinosaurs Lisa Randall, by striving to gain greater understanding of how the universe works, is doing her bit to shine a light in the darkness.
Review posted – 10/30/15
Publication date – 10/27/15
NASA’s Site about the Kuiper Belt
In 2010, the National Academy of Sciences presented their results on asteroids and the threats they pose in a document entitled Defending Planet Earth: Near-Earth Object Surveys and Hazard Mitigation Strategies
A nice article in the June 2013 Smithsonian – Lisa Randall’s Guide to the Galaxy
An interesting set of videos with Randall on BIG thoughts
Although the interview is for a different book, Randall’s Daily Show interviewwith Jon Stewart is fun and informative re things scientific.
Ditto, as Randall is interviewed by Tavis Smiley
A nifty set of videos on the hazards presented by asteroids
The Dark Song from The Lego Movie – It’s Awesome | 0.889978 | 3.449151 |
Cassini is orbiting Saturn with a twelve-day period in a plane inclined 57 degrees from the planet's equatorial plane. The most recent spacecraft tracking and telemetry data were collected on March 26 by the 70-meter Deep Space Network station at Goldstone, California. Except for some science instrument issues described in previous reports, the spacecraft continues to be in an excellent state of health with all of its subsystems operating normally. Information on the present position and speed of the Cassini spacecraft may be found on the "Present Position" page at: http://saturn.jpl.nasa.gov/mission/presentposition/ .
Cassini's Sequence Implementation Process (SIP) teams continued working on the ten-week command sequences S79 and S80, which will go active on the flight system in June and August respectively, and planning continued for the 2016 start of Cassini's F-ring and Proximal Orbits phase. Meanwhile, commands from the on-board S77 sequence finished controlling the spacecraft's activities in flight and commands from S78 started taking effect on Tuesday as planned.
Wednesday, March 20 (DOY 079)
Cassini flew across Saturn's night-side southern auroral oval, carrying out observations for nine hours coordinated among the telescopic optical remote sensing (ORS) instruments and the magnetospheric and plasma science (in-situ) instruments. The latter measured field-aligned currents, auroral plasma populations, and plasma waves across different latitudes, to help scientists understand the energy balance of Saturn's upper atmosphere.
Thursday, March 21 (DOY 080)
The Cosmic Dust Analyzer (CDA) took measurements of the dust impacting the instrument during ring plane crossing. CDA can discern the mass, quantity, impact speed and direction, chemical composition, and electrical charge of grains the size of smoke particles.
Friday, March 22 (DOY 081)
Cassini passed through periapsis going 39,250 kilometers per hour relative to Saturn, at about 425,000 kilometers above the cloud tops.
The Magnetometer executed a calibration while rotating the spacecraft about its X axis for sensor offset determination. The Ultraviolet Imaging Spectrograph (UVIS), in collaboration with the Composite Infrared Spectrometer (CIRS) and the Visible and Infrared Mapping Spectrometer (VIMS) riding along, observed the north pole for 11.5 hours to study auroral morphology at high spatial resolution from low altitude and high inclination.
Saturday, March 23 (DOY 082)
UVIS, with CIRS and VIMS, which were also taking data (riding along), observed the giant gas planet's dayside aurora at low phase angles for 13.5 hours, covering more than one planetary rotation. The objective is to identify rotating features and signatures of solar wind interaction under varying conditions, such as spots related to Kelvin-Helmholtz viscous interaction
(see /resources/11582 for an image)
dor arcs produced by magnetopause reconnection. Spectral analysis of any features, such as differences in atomic hydrogen (H) versus molecular hydrogen (H2) or trihydrogen (H3+) emissions, reveals precipitating electron energy from coupling of the solar wind, the magnetosphere, and the ionosphere.
Sunday, March 24 (DOY 083)
The Realtime Operations team uplinked the first part of the S78 command sequence using the 70 meter Deep Space Network station at Goldstone, California. The team confirmed that all 9000 individual commands were received and properly stored on the spacecraft after a round-trip light time of 2 hours 30 minutes. The team will uplink the second part in mid-May when enough on-board memory will be available.
Monday, March 25 (DOY 084)
An image featured today illustrates the violent history recorded on the surface of Saturn's second largest moon Rhea:
Tuesday, March 26 (DOY 085)
The final S77 commands executed today and the S78 sequence began controlling the spacecraft. Back on Earth, the S78 SIP team assumed responsibility and authority for operations.
The Imaging Science Subsystem (ISS) and UVIS made a 4.5-hour observation of the 8-kilometer irregular moon Hyrrokkin in its retrograde orbit about Saturn. They then began a 19-hour observation of the irregular retrograde moon Narvi, which is about six kilometers in diameter. These tiny objects orbit Saturn more than eighteen million kilometers away with periods on the order of a thousand days. | 0.834739 | 3.172308 |
Powerful superflares from young red dwarf stars, like the one shown in this artist's concept, can strip the atmospheres from fledgling planets, spelling disaster for any potential life. (Credit: NASA/ESA/D. Player (STScI)) Red dwarfs are small, slowly burning stars that can live for trillions of years before they run out of fuel. And thanks to their generous lifespans, the planets around them (at least those close enough to stay warm) are often considered prime locations for the development of life. However, new research set for publication in The Astrophysical Journal found that red dwarfs tend to be pretty abusive hosts, at least when they’re young. According to the study, infant red dwarfs emit some of the most formidable superflares ever observed, often erupting with 100 to 1,000 times more energy than their older counterparts. In fact, the flares from these tiny, young stars are so strong that they (pardon the pun) dwarf the average solar flares of our own, much larger Sun — and that’s a problem for any nascent life trying to take root around baby red dwarfs. With the help of the Hubble Space Telescope, the authors of the new study are currently carrying out a survey called HAbitable Zones and M dwarf Activity across Time, or HAZMAT. “The goal of the HAZMAT program is to help understand the habitability of planets around low-mass stars,” said Evgenya Shkolnik, principal investigator of HAZMAT, in a press release. “These low-mass stars are critically important in understanding planetary atmospheres.” Three out of four stars in the Milky Way (and likely the entire cosmos) are red dwarfs, which are commonly referred to as M dwarfs. Because these stars are so abundant, astronomers think that most “habitable” exoplanets — planets that can support liquid water on their surface — likely orbit red dwarf stars. However, hosting liquid water is not the only requirement for life as we know it. We also have to consider incoming bursts of radiation from flares, which, if they’re strong enough, can wreak havoc on the surface of a planet. This is especially true for the planets around red dwarfs, which must sit very near their host stars in order to receive enough heat to be considered habitable. To investigate the overall flare activity of these stars, the HAZMAT project uses far-ultraviolet light to probe red dwarfs that fall into three general age groups: young, intermediate, and old. Though red dwarfs in their first couple hundred million years have long been known to be powerful emitters of ultraviolet light, the exact processes that cause the boosted ultraviolet signals are not yet well understood. If a large percentage of the ultraviolet light coming from young red dwarfs turns out to be due to powerful flares — which occur when magnetic field lines get tangled up and eventually snap within a star — then the atmospheres of any planets around the red dwarfs may be in danger of getting stripped away. This would spell disaster for alien life trying to survive on the fledgling planet’s surface. Using Hubble, the researchers monitored the surfaces of 12 red dwarfs located between 120 and 165 light-years from Earth. In less than a day’s worth of observing time, the team detected 18 flares bursting from the young stars, which are about 40 million years old. Of the 18 flares the researchers detected, 10 of them had energies of over 1023 joules, which is roughly how much energy strikes the surface of the Earth from the Sun over the course of a week. The most powerful flare they observed, dubbed the “Hazflare,” released about 1025 joules of energy, putting it on par with the most energetic flare from the Sun ever recorded. “With the Sun, we have a hundred years of good observations,” said lead author Parke Loyd of Arizona State University. “And in that time, we’ve seen one, maybe two, flares that have an energy approaching that of the Hazflare. In a little less than a day’s worth of Hubble observations of these young stars, we caught the Hazflare, which means that we’re looking at superflares happening every day or even a few times a day.” Although the new findings indicate that planets around young red dwarfs are not very well suited for the development of life, the HAZMAT team is quick to note that the existence of life around these stars is not out of the question. “Flares like we observed have the capacity to strip away the atmosphere from a planet. But that doesn’t necessary mean doom and gloom for life on the planet,” said Loyd. “It just might be different life than we imagine. Or there might be other processes that could replenish the atmosphere of the planet. It’s certainly a harsh environment, but I would hesitate to say that it is a sterile environment.” Plus, even if flares from young red dwarfs are strong enough to stifle the formation of life early on, older red dwarfs may not have the same problem. So far, the team has only looked at red dwarfs during their proverbial terrible twos, but they still need to see how more mature red dwarfs act as they grow older. To do this, the next stage of the HAZMAT study will investigate the flare activity of middle-aged red dwarfs — those around 650 million years old — before moving on to the oldest age bracket. So stay tuned, because by continuing to study how red dwarfs evolve (and hopefully quiet down) over time, we will ultimately better understand the true habitability of planets orbiting the most common type of star in the entire universe. | 0.878675 | 4.03598 |
Telescope duo discover Sun’s chilly neighbor
NASA’s Wide-field Infrared Survey Explorer (WISE) teamed up with the Spitzer Space Telescope to make a very “cool” discovery – a stellar version of our North Pole. The frigid new star, classified as a brown dwarf, is the fourth closest star system to the Sun at a distance of approximately 7.2 light-years away. Our Sun’s nearest neighboring system is the triple star system of Alpha Centauri, at a distance of only 4 light-years away.
“It’s very exciting to discover a new neighbor of our solar system that is so close,” said Kevin Luhman, an astronomer at Pennsylvania State University’s Center for Exoplanets and Habitable Worlds, University Park. “And given its extreme temperature, it should tell us a lot about the atmospheres of planets, which often have similarly cold temperatures.”
Brown dwarfs are essentially failed stars, lacking the mass to ignite nuclear fusion and radiate starlight. Nuclear fusion, the conversion of Hydrogen to Helium in a star’s core, is what fuels a star and makes it shine. The first brown dwarf star wasn’t discovered until 1995 and currently astronomers hypothesize our universe could contain as many brown dwarfs as traditional stars.
Brown dwarfs are very cool and dim and therefore most go unobserved, that’s where WISE and Spitzer come in. There faint signatures are unable to be seen in visible light but do shine in the infrared portion of the spectrum. The new brown dwarf, dubbed WISE J085510.83-071442.5, has a record-setting frigid temperature of minus 54 and 9 degrees Fahrenheit (minus 48 to minus 13 degrees Celsius). To put that into perspective, previous brown dwarf discoveries were right around room temperature.
WISE surveyed the areas around our Sun two and three times and noticed a rare, fast-moving object in the data. After taking a closer look, astronomers realized exactly what they had discovered. This rapid motion told them two things: the celestial body in question was close and was really something special.
“This object appeared to move really fast in the WISE data,” said Luhman. “That told us it was something special.”
The apparent rapid motion (illustrated here) of WISE J085510.83-071442.5 triggered Luhman to observe it using the Spitzer Space Telescope, and by doing so he was able to determine its temperature. By using the two telescopes in combination, Luhman was also able to measure exactly how far away WISE J085510.83-071442.5 was. The method used is called the parallax effect and is essentially the same effect we see by holding an object in front of our face and seeing it move when you cover your left eye and then your right.
“It is remarkable that even after many decades of studying the sky, we still do not have a complete inventory of the sun’s nearest neighbors,” said Michael Werner, the project scientist for Spitzer at NASA’s Jet Propulsion Laboratory in Pasadena, Calif. JPL manages and operates Spitzer. “This exciting new result demonstrates the power of exploring the universe using new tools, such as the infrared eyes of WISE and Spitzer.”
WISE J085510.83-071442.5 is estimated to have a mass of three to ten times the mass of Jupiter. Since brown dwarfs are so common, Luhman and his team believe this to in fact be a brown dwarf and not a gas giant who was ejected from its star system. If this is confirmed to be a brown dwarf, it will be one of the least massive ever observed.
WISE was constructed by the Ball Aerospace & Technologies Corp of Boulder, CO. and is managed by NASA’s Jet Propulsion Laboratory in Pasadena, CA.
The Spitzer Space Telescope is also managed by NASA’s Jet Propulsion Laboratory in Pasadena, CA and was named for American theoretical physicist Lyman Spitzer who first conceived the idea of telescopes operating in space.
SpaceFlight Insider is a space journal working to break the pattern of bias prevalent among other media outlets. Working off a budget acquired through sponsors and advertisers, SpaceFlight Insider has rapidly become one of the premier space news outlets currently in operation. SFI works almost exclusively with the assistance of volunteers. | 0.876509 | 3.82435 |
Eyes to the sky
August 1, 2019
Posted by Lake Erie Nature and Science Center
Look up! The Perseid Meteor Shower, one of the most spectacular meteor showers of the year, will peak the evening of Monday, August 12, 2019.
In preparation for this cosmic event, the Center’s planetarium staff explains what a meteor shower is and provides tips for seeing shooting stars this August.
What is a meteor shower?
Comets are large, icy Solar System bodies. As a comet passes closer to the Sun, its ice warms and begins to release particles of dust and rock into the atmosphere, which can result in a glowing trail of vapor.
Meteor showers occur when meteoroids, the rocks, and debris left behind by a comet, enter the Earth’s atmosphere. Meteoroids are almost always small enough to quickly burn up in our atmosphere, so there is little chance they will strike Earth’s surface. A meteorite is any part of the meteoroid that survives and lands on Earth.
Meteors, also known as “shooting stars,” are the streaks of light produced in the night sky when a meteoroid burns up in the Earth’s atmosphere.
How can I view the meteor shower?
Each year, Earth passes through the dust trail of Comet Swift-Tuttle, resulting in visible meteor showers. The Perseid Meteor Shower will peak the evening of August 12, 2019, and is one of the best opportunities to view shooting stars this year.
Meteor showers are named after the constellation where the meteors appear from. Look toward the constellation Perseus in the Northeastern sky between 9:30 p.m. and 5 a.m. to view shooting stars. During the peak, observers can expect to see 60-70 meteors per hour.
The key to seeing the Perseid Meteor Shower? Head to a dark area in the suburbs or countryside, lay down a blanket, bring some snacks and enjoy the celestial show. It takes 30 minutes for your eyes to adjust to the dark, so the longer you wait, the more you will see! | 0.804924 | 3.171316 |
You can buy one of our star maps which capture a special moment in your life and it’s easy not to even question: what are these things I’m choosing to attach such a precious memory? Humankind has an ancient affinity and reverence for the stars. They are symbolic of romance itself. That’s why, if I may say so myself, a personalized star map makes the ideal gift. What are stars though? What are these little dots that make us feel all sorts of wonderous emotions?
We all know roughly where they are: in the night sky. We also know what they look like: little white dots (or something more poetic!). You might want to know a bit more about them. What are they made of? How far (or close) are they? How many types of stars are there? How did they form? So many questions! In fact, if you’re feeling confident about your star knowledge, you can take our Ultimate Star Quiz. A gold star to anyone who gets more than half right!
How do stars become stars?
Stars begin their life as nebulae: clouds of dust and gas. These are cold and relatively lifeless entities but it just takes one catalyst, in the form of a comet or the shockwaves from an exploding star, to give it the energy it needs to take the next step.
Cloud particles start moving, colliding with one another and merging together. This creates a higher density of mass which creates more gravity (more mass equals a stronger gravitational pull). Over millions of years, the nebulae clumps together to form a protostar.
All these binding particles create a huge amount of heat and when the protostar reaches 7 million kelvins, the hydrogen atoms start fusing together to create helium (and even more energy is unlocked). This reaction is known as nuclear fusion. The outward energy being created is less than the gravitational energy keeping them together so the star keeps its form, drawing new material into it.
After millions of years, when enough of the star has collapsed, the outward energy exerted by nuclear fusion outweighs the energy of gravity’s pull. This is then a main sequence star, just like our sun (which is specifically called a yellow dwarf star). It can take millions more years before the star then starts to expand, reach a sort of elastic limit and implode in on itself.
How long do stars live?
That depends on its mass. The higher the mass, the quicker the star burns out. This could be useful for our Ultimate Star Quiz (hint hint)! A star with 20 times the mass of our sun would burn out 4.5 times as fast, for example. A “massive star” will end up as a red giant, then a supernova and finally a neutron star or a black hole. An “average star” will become a red giant, followed by a planetary nebula and finally a white dwarf.
How many stars are there?
We don’t know exactly, but according to David Kornreich’s calculations there are roughly 1,000,000,000,000,000,000,000,000 stars. That’s 1 septillion in the American numbering system and 1 quadrillion in the European system. He even felt this was an underestimation.
Again, we don’t know exactly but, in our Milky Way, one calculation puts the number of stars at approximately 100 billion. We can only see 9,096 of these with the naked eye (4,548 from each hemisphere).
Which is our closest star?
The sun! But after that it comes Proxima Centauri (4.24 lightyears away), Centauri A & B (both about 4.36 lightyears away). These are all in a system (like our solar system) called Alpha Centauri.
Do the stars move?
Stars appear to rise in the east and set in the west but this is due to the earth’s rotation. The stars do have their own movement through space. Because they are so far away, however, this movement appears to us as relatively small.
Are we made from star dust?
Essentially, yes. Stars which have gone supernova are responsible for creating many of the elements which make up our bodies including oxygen, carbon, hydrogen, nitrogen, calcium, phosphorous and more.
You may have many more questions about the stars and our Ultimate Star Quiz just might have some of those questions too (it’s quite a big quiz!) so if you’re feeling particularly stellar then click the link to find out more.
Know enough? Then you’re certainly ready to order yourself a beautiful map of the stars to commemorate that time when the stars aligned for you. Some Under Lucky Stars customers have even felt inspired to give astronomy a go. Have a look at our Learning The Stars series, if that sounds like it could be you too. You can also check out our #SaveOurStars campaign to help preserve our view of the night sky.
You’re a superstar, thanks for reading! | 0.920116 | 3.270882 |
Astronomers have found thousands of exoplanets lurking within the distant cosmos, but they know very little about their origins. Now, a dramatic new image could be offering a rare glimpse into one of the most mysterious processes in the universe: the birth of a new planet.
Using the European Southern Observatory's Very Large Telescope (ESO's VLT), researchers spotted a glowing orange spiral with a "twist" marking the spot where they believe a planet may be forming. According to a study published Wednesday in the journal Astronomy & Astrophysics, it would be the first direct evidence of a planet coming into existence.
"Thousands of exoplanets have been identified so far, but little is known about how they form," lead author Anthony Boccaletti, of the Observatoire de Paris at PSL University in France, said in a press release.
"We need to observe very young systems to really capture the moment when planets form," he said.
Astronomers observed the possible baby planet forming a spiral of dust and gas around a young star known as AB Aurigae, located 520 light years away from Earth in the constellation Auriga. Scientists know planets form as cold gas and dust collide with one another around stars over billions of years, but these new observations provide crucial data to paint a clearer picture of the process.
Researchers have been studying the star system for years using the Atacama Large Millimeter/submillimeter Array (ALMA) in Chile. But until now, they have have been unable to capture clear images of this process in order to find the all-important "twist" that identifies the birth of a planet.
The deepest images of the system to date, taken using the SPHERE instrument on the VLT, show a stunning swirl around AB Aurigae, signaling the presence of a baby planet "twisting, swirling and "kicking" to create "disturbances in the disc in the form of a wave, somewhat like the wake of a boat on a lake," said co-author Emmanuel Di Folco of the Astrophysics Laboratory of Bordeaux (LAB) in France. The spiral is created as the planet rotates around the central star.
Based on predicted models, the team believes the planet is forming in the very bright yellow "twist" region close to the center of the image, which is located at about the same distance from its star as Neptune is from the sun.
"The twist is expected from some theoretical models of planet formation," said co-author Anne Dutrey, also at LAB. "It corresponds to the connection of two spirals — one winding inwards of the planet's orbit, the other expanding outwards — which join at the planet location. They allow gas and dust from the disc to accrete onto the forming planet and make it grow."
Astronomers hope to get an even clearer picture of the growing planet after the completion of ESO's Extremely Large Telescope, which will become "the world's biggest eye on the sky," in 2025. | 0.872398 | 3.821709 |
Huge Martian landforms that look like ancient lava flows were actually caused by mud, scientists have discovered.
There are tens of thousands of these landforms on the Red Planet’s surface, reaching hundreds of kilometres in length. They occur where ancient liquids have flowed downhill, scouring out massive channels.
They look similar to lava flows on Hawaii, but their true nature has evaded scientists – until now.
A team of European researchers used the ‘Mars Chamber’ at the Open University, UK, to simulate the movement of mud on Mars and Earth. Inside this vacuum chamber, it’s possible to recreate the low atmospheric pressures and cold temperatures of -20°C found on the Martian surface.
The mud on Mars is thought to have come from catastrophic flooding, comparable to the largest floods ever known to have occurred on Earth. As the floodwater seeped beneath the surface, it took sediments with it, which could erupt to the surface again as mud.
This process, called ‘sedimentary volcanism’ may also occur on the dwarf planet Ceres, which could harbour a muddy water ocean beneath its icy crust.
“We suggest that mud volcanism can explain the formation of some lava-like flow morphologies on Mars,” said Dr Petr Brož, lead author of the study at the Czech Academy of Sciences.
“That similar processes may apply to eruptions of mud on icy bodies in the outer Solar System, like on Ceres.”
Reader Q&A: Do all planets have magnetic fields?
Asked by: Daniel J Buhs, US
No, not all planets have magnetic fields. The four gas giants have extremely strong magnetic fields, Earth has a moderately strong magnetic field, Mercury has an extremely weak field, but Venus and Mars have almost no measurable fields.
Planetary magnetic fields are formed by the interaction between the convection of interior conducting material (molten rock and metal) and the planet’s own rotation. Mercury’s field is weak because it rotates so slowly. Venus doesn’t have an appreciable field because there appears to be little convection in its molten interior. Mars doesn’t have an appreciable field – although it did in the past – because its interior has solidified. | 0.830061 | 3.655415 |
Difference between Galaxy and Milky Way
Key Difference: A group of numerous stars, dust, planets and other interstellar matter, tied together by a gravitational force is known as a Galaxy. Milky Way is a Galaxy that comprises of our solar system.
Stars, planets, universe, all these words generate a lot of curiosity and research areas related to them are always evolving and expanding as this whole Universe. Galaxy and Milky Way are two such words that always make us feel that our world is just like a tiny particle in context to the whole Universe. Milky Way is the name that is given to the Galaxy that consists of our solar system. Let us understand these both terms.
An astronomical ecosystem comprising of stars, dust, planets, and other interstellar matter is known as a Galaxy. It is held together by its own gravitational force. Galaxies are considered to be the basic units of cosmic systems. Two basic Galaxy types are:-
Spirals: These types of galaxies are little flattened and the ellipsoidal systems are supported by the random motions exhibited by the stars. In these kinds of galaxies, the disk contains stars, planets, dust and gas. They all rotate around their galactic centres and in a regular manner.
Ellipticals: They have comparatively more flattened disks and are also supported by the rotation. These are also known as disk galaxies. Giant elliptical galaxies are considered to be about two million light years long.
In addition to these main galaxies, other galaxies are referred to as irregular galaxies. The shape of this type of Galaxy is very different from elliptical and spiral and lack any regular form or structure.
The total luminosity of a Galaxy can be directly related with the total number of stars that are present in the Galaxy. Galaxies radiate a continuous spectrum of energy and thus, these spectrums are highly useful in understanding the galaxies. There are uncountable galaxies that exists in the Universe that is known to us. Galaxies that contain less than a billion stars are termed as “Small Galaxies.”Galaxies may occur alone or in pairs. The galaxies that are near to each, also influences each other. Galaxies within groups tend to interact with each other and can even merge under the influence of interactive gravity.
Many astronomers believe that galaxies were formed after the cosmic phenomenon known as ‘big bang’. This phenomenon is held responsible for the creation of Universe, that took place some 10 billion to 20 billion years ago. It is believed that a bubble that was extremely hot and dense exploded and then exploded particles formed the various astronomical objects. Galaxies were also formed as a result of this explosion. Name of some of the galaxies are Milky Way, Andromeda, Cigar Galaxy and Comet Galaxy.
Milky Way is a type of spiral Galaxy and it contains our solar system. It is supposed to be consisted of about 100-400 billion stars. It has been given the name 'Milky Way', as it appears as a dim glowing band. The term "Milky Way" is a translation of the Classical Latin via lactea, from the Greek word galaxías meaning “milky circle".
A renowned astronomer, Edwin Powell Hubble in the year 1923, determined that there are other galaxies that are also present in the Universe, apart from our Milky Way. Earlier, the assumption was that Milky Way is the only Galaxy present in the Universe. Milky Way measures about 100,000 light years across. Our solar system is placed about 25000 light years to the galactic center. A glimpse of the galaxy could be seen in a dark night with the help of binoculars or a small telescope. The band primarily contains stars and thus the combined light is obtained in the form of a dim glow.
Milky Way has various stars, enough gas and dust, and thus has the potential of making more stars even in billions. Some of the specifications are listed below:-
- Type : Spiral Galaxy
- Diameter: some 100,000-120,000 light years
- Number of stars: 100-400 billion stars
- Rotational period: Around 200 million years at the position of the Sun
- Age of oldest known star: At least 13.6 billion years
A Galaxy is a group of stars, dust and other astronomical matter that are held together by the force of gravity. On the other hand, Milky Way is a spiral Galaxy that includes our solar system.
Image Courtesy: fahsscience9.wikispaces.com, datehookup.com | 0.843293 | 3.28168 |
NASA mission, with help from UMD physicists, is first to observe how magnetic reconnection takes place, a critical step in understanding space weather
College Park, MD-(ENEWSPF)- Most people do not give much thought to the Earth’s magnetic field, yet it is every bit as essential to life as air, water and sunlight. The magnetic field provides an invisible, but crucial, barrier that protects Earth from the sun’s magnetic field, which drives a stream of charged particles known as the solar wind outward from the sun’s outer layers. The interaction between these two magnetic fields can cause explosive storms in the space near Earth, which can knock out satellites and cause problems here on Earth’s surface, despite the protection offered by Earth’s magnetic field.
A new study co-authored by University of Maryland physicists provides the first major results of NASA’s Magnetospheric Multiscale (MMS) mission, including an unprecedented look at the interaction between the magnetic fields of Earth and the sun. The paper describes the first direct and detailed observation of a phenomenon known as magnetic reconnection, which occurs when two opposing magnetic field lines break and reconnect with each other, releasing massive amounts of energy.
The discovery is a major milestone in understanding magnetism and space weather. The research paper appears in the May 13, 2016, issue of the journal Science.
“Imagine two trains traveling toward each other on separate tracks, but the trains are switched to the same track at the last minute,” said James Drake, a professor ofphysics at UMD and a co-author on the Science study. “Each track represents a magnetic field line from one of the two interacting magnetic fields, while the track switch represents a reconnection event. The resulting crash sends energy out from the reconnection point like a slingshot.”
Evidence suggests that reconnection is a major driving force behind events such as solar flares, coronal mass ejections, magnetic storms, and the auroras observed at both the North and South poles of Earth. Although researchers have tried to study reconnection in the lab and in space for nearly half a century, the MMS mission is the first to directly observe how reconnection happens.
The MMS mission provided more precise observations than ever before. Flying in a pyramid formation at the edge of Earth’s magnetic field with as little as 10 kilometers’ distance between four identical spacecraft, MMS images electrons within the pyramid once every 30 milliseconds. In contrast, MMS’ predecessor, the European Space Agency and NASA’s Cluster II mission, takes measurements once every three seconds—enough time for MMS to make 100 measurements.
“Just looking at the data from MMS is extraordinary. The level of detail allows us to see things that were previously a blur,” explained Drake, who served on the MMS science team and also advised the engineering team on the requirements for MMS instrumentation. “With a time interval of three seconds, seeing reconnection with Cluster II was impossible. But the quality of the MMS data is absolutely inspiring. It’s not clear that there will ever be another mission quite like this one.”
Simply observing reconnection in detail is an important milestone. But a major goal of the MMS mission is to determine how magnetic field lines briefly break, enabling reconnection and energy release to happen. Measuring the behavior of electrons in a reconnection event will enable a more accurate description of how reconnection works; in particular, whether it occurs in a neat and orderly process, or in a turbulent, stormlike swirl of energy and particles.
A clearer picture of the physics of reconnection will also bring us one step closer to understanding space weather—including whether solar flares and magnetic storms follow any sort of predictable pattern like weather here on Earth. Reconnection can also help scientists understand other, more energetic astrophysical phenomena such as magnetars, which are neutron stars with an unusually strong magnetic field.
“Understanding reconnection is relevant to a whole range of scientific questions in solar physics and astrophysics,” said Marc Swisdak, an associate research scientist in UMD’s Institute for Research in Electronics and Applied Physics. Swisdak is not a co-author on the Science paper, but he is actively collaborating with Drake and others on subsequent analyses of the MMS data.
“Reconnection in Earth’s magnetic field is relatively low energy, but we can get a good sense of what is happening if we extrapolate to more energetic systems,” Swisdak added. “The edge of Earth’s magnetic field is an excellent test lab, as it’s just about the only place where we can fly a spacecraft directly through a region where reconnection occurs.”
To date, MMS has focused only on the sun-facing side of Earth’s magnetic field. In the future, the mission is slated to fly to the opposite side to investigate the teardrop-shaped tail of the magnetic field that faces away from the sun.
The research paper, “Electron-Scale Measurements of Magnetic Reconnection in Space,” James Burch et al., is published in the journal Science on May 13, 2016.
You have used up your free articles for this month. To continue reading click here to login or subscribe. | 0.828753 | 3.86302 |
Figuring for Yourself
The text says a star does not change its mass very much during the course of its main-sequence lifetime. While it is on the main sequence, a star converts about 10% of the hydrogen initially present into helium (remember it’s only the core of the star that is hot enough for fusion). Look in earlier chapters to find out what percentage of the hydrogen mass involved in fusion is lost because it is converted to energy. By how much does the mass of the whole star change as a result of fusion? Were we correct to say that the mass of a star does not change significantly while it is on the main sequence?
The text explains that massive stars have shorter lifetimes than low-mass stars. Even though massive stars have more fuel to burn, they use it up faster than low-mass stars. You can check and see whether this statement is true. The lifetime of a star is directly proportional to the amount of mass (fuel) it contains and inversely proportional to the rate at which it uses up that fuel (i.e., to its luminosity). Since the lifetime of the Sun is about 1010 y, we have the following relationship:
where T is the lifetime of a main-sequence star, M is its mass measured in terms of the mass of the Sun, and L is its luminosity measured in terms of the Sun’s luminosity.
You can use the equation in Exercise 22.34 to estimate the approximate ages of the clusters in Figure 22.10, Figure 22.12, and Figure 22.13. Use the information in the figures to determine the luminosity of the most massive star still on the main sequence. Now use the data in Table 18.3 to estimate the mass of this star. Then calculate the age of the cluster. This method is similar to the procedure used by astronomers to obtain the ages of clusters, except that they use actual data and model calculations rather than simply making estimates from a drawing. How do your ages compare with the ages in the text?
You can estimate the age of the planetary nebula in image (c) in Figure 22.18. The diameter of the nebula is 600 times the diameter of our own solar system, or about 0.8 light-year. The gas is expanding away from the star at a rate of about 25 mi/s. Considering that distance = velocity time, calculate how long ago the gas left the star if its speed has been constant the whole time. Make sure you use consistent units for time, speed, and distance.
If star A has a core temperature T, and star B has a core temperature 3T, how does the rate of fusion of star A compare to the rate of fusion of star B? | 0.804856 | 3.834968 |
What Is The Wolf Moon? What You Need To Know About Its Origins & Its Meaning
I don't know about the rest of 2018, but January is getting off to a great start — as long as you like stargazing. Next year will kick off with two full moons in the first month, beginning on the night of Jan. 1. So what is the Full Wolf Moon, exactly, and what does it mean for the lives of us Earthlings? If you're the type to put stock in astrology, it's bound to influence your decisions in the coming weeks. Otherwise, it's an excuse to marvel at nature and humanity's place in the universe before getting back to all the "new year, new you" business.
According to the Old Farmer's Almanac, several Native American cultures kept track of the seasons by naming each moon phase throughout the year. These names roughly correspond to the 12 months: the Pink Moon takes place in April, the Strawberry Moon in June, and so on. Colonial Americans most commonly adopted the names used by the Algonquin culture, which extended from New England to Lake Superior at the time.
Depending on the culture, the first full moon of the year was sometimes known as the Old Moon or Snow Moon. The most common name associated with January's full moon, however, was the Wolf Moon, named for the days when wolves howled and scrabbled for food just outside town. Given that breeding season begins in January, wolves may have howled especially often during this time.
In 2018, the Wolf Moon will also be a supermoon, meaning the moon is at its fullest when it's also closest to Earth. This doesn't actually make much of a difference to the naked eye, although it may look a little brighter and bigger when viewed with a telescope. According to Space.com, the Wolf Moon will rise in North America at 9:24 p.m. on Jan. 1, and it will be found in the Gemini constellation. (Due to time differences, it won't rise until Jan. 2 in Europe and Asia.)
Traditionally, full moons are seen as a chance to start anew — time to reflect on your choices and forge a new path. It's especially poignant, then, that the Full Wolf Moon will rise on the first day of 2018. Take the night of Jan. 1 to figure out where you want the year to go, and formulate a plan to make those goals a reality. Forever Conscious also notes that full moons are associated with illumination, so prepare for some hard truths to come to light.
That's the lowdown on the Wolf Moon. The second full moon of the month, known as a blue moon, is an entirely different story. According to Space.com, it will rise on Jan. 30 and reach peak fullness on Jan. 31. Get this: The blue moon is also a supermoon, and it will feature a total lunar eclipse. This phenomenon occurs when Earth blocks the sun's light from reaching the moon, which has the eerie effect of turning the moon blood-red. According to Space.com, January's lunar eclipse will be visible from Asia, Australia, the Pacific Ocean, and the western United States.
Obviously, people wouldn't let something like a rust-colored moon pass without comment. A total lunar eclipse is called a Blood Moon, so the full moon on Jan. 31 has three different names: Supermoon, Blue Moon, and Blood Moon. I'm not saying the Wolf Moon should go home with its tail between its legs, but it's definitely going to be overshadowed.
If you're an avid stargazer, you won't want to miss out on January's lunar events — especially because February won't have a full moon at all. Don't forget to practice your howl for showtime on Jan. 1. | 0.802657 | 3.115026 |
Astronomers have discovered a peculiar solar system some 500 light-years away from Earth that may force them to rethink how planets form. The star in question is only two million years old — a mere ‘toddler’ by astronomical standards — but despite its very young age, it’s orbited by four Jupiter and Saturn-sized planets.
A crowded baby star
Since the first confirmation of an exoplanet orbiting a sun-like star in 1995, and with only a few narrow slices of our Milky Way galaxy surveyed so far, astronomers have confirmed 2,327 exoplanets, with a further 2,244 awaiting confirmation.
A recent statistical estimate places, on average, at least one planet around every star in the galaxy. However, only 1% of the stars astronomers have surveyed so far host a hot Jupiter — a class of gas giant exoplanets that are inferred to be physically similar to Jupiter but that have a very short orbital period.
Most of the hot Jupiters currently identified orbit stars that are at least hundreds of millions of years old. This is why CI Tau, the young star recently studied by researchers at the University of Cambridge, is so interesting. What’s more, it has not one but four gas giants orbiting it.
The astronomers used Atacama Large Millimeter/submillimeter Array (ALMA) to identify the exoplanets. CI Tau is surrounded by a huge disc of dust and ice, known as a protoplanetary disc, which will seed planets, moons, asteroids, and other objects in its system. ALMA’s instruments were able to find distinct gaps in the disc which theoretical modeling showed would correspond to gas giant planets orbiting the star.
According to the new study published the Astrophysical Journal Letters, the four planets differ greatly in their orbit. The closest planet to CI Tau, a juvenile hot Jupiter, is within the equivalent orbit of Mercury.
The farthest orbits are at a distance three times greater than that of Neptune from the Sun. The two outer planets are about the mass of Saturn, while the two inner planets are around one and 10 times the mass of Jupiter respectively. Given that the outermost planet is more than a thousand times further from the star than the innermost one, the system has also set a new record for the most extreme range of orbits observed so far.
Scientists are not sure what to make of this anomalous system. Hot Jupiters have always puzzled astronomers because they are often thought to orbit too close to their parent stars to have formed in situ — instead, they might be captured rogue planets. But considering the age of CI Tau, the findings suggest that hot Jupiters could form within close proximity of a star.
“It is currently impossible to say whether the extreme planetary architecture seen in CI Tau is common in hot Jupiter systems because the way that these sibling planets were detected—through their effect on the protoplanetary disc – would not work in older systems which no longer have a protoplanetary disc,” said Professor Cathie Clarke from Cambridge’s Institute of Astronomy, the study’s first author.
In the future, the team of researchers plans on studying CI Tau at multiple wavelengths to learn more about the disc and its planets. For instance, they would like to see whether the outer planets played a role in driving their innermost sibling into such an ultra-close orbit. How the two outer planets formed in the first place is also a mystery.
“Planet formation models tend to focus on being able to make the types of planets that have been observed already, so new discoveries don’t necessarily fit the models,” said Clarke. “Saturn mass planets are supposed to form by first accumulating a solid core and then pulling in a layer of gas on top, but these processes are supposed to be very slow at large distances from the star. Most models will struggle to make planets of this mass at this distance.” | 0.893809 | 3.929135 |
Gibbous ♏ Scorpio
Moon phase on 25 March 2016 Friday is Waning Gibbous, 16 days old Moon is in Libra.Share this page: twitter facebook linkedin
Previous main lunar phase is the Full Moon before 1 day on 23 March 2016 at 12:01.
Moon rises in the evening and sets in the morning. It is visible to the southwest and it is high in the sky after midnight.
Lunar disc appears visually 8.4% narrower than solar disc. Moon and Sun apparent angular diameters are ∠1768" and ∠1923".
Next Full Moon is the Pink Moon of April 2016 after 27 days on 22 April 2016 at 05:24.
There is medium ocean tide on this date. Sun and Moon gravitational forces are not aligned, but meet at very acute angle, so their combined tidal force is moderate.
The Moon is 16 days old. Earth's natural satellite is moving from the middle to the last part of current synodic month. This is lunation 200 of Meeus index or 1153 from Brown series.
Length of current 200 lunation is 29 days, 9 hours and 29 minutes. It is 1 hour and 23 minutes longer than next lunation 201 length.
Length of current synodic month is 3 hours and 15 minutes shorter than the mean length of synodic month, but it is still 2 hours and 54 minutes longer, compared to 21st century shortest.
This lunation true anomaly is ∠339.5°. At the beginning of next synodic month true anomaly will be ∠355.6°. The length of upcoming synodic months will keep decreasing since the true anomaly gets closer to the value of New Moon at point of perigee (∠0° or ∠360°).
Moon is reaching point of apogee on this date at 14:16, this is 15 days after last perigee on 10 March 2016 at 07:02 in ♈ Aries. Lunar orbit is starting to get closer, while the Moon is moving inward the Earth for 13 days ahead, until it will get to the point of next perigee on 7 April 2016 at 17:36 in ♈ Aries.
This apogee Moon is 406 125 km (252 354 mi) away from Earth. It is 717 km farther than the mean apogee distance, but it is still 584 km closer than the farthest apogee of 21st century.
2 days after its ascending node on 22 March 2016 at 12:59 in ♍ Virgo, the Moon is following the northern part of its orbit for the next 11 days, until it will cross the ecliptic from North to South in descending node on 5 April 2016 at 17:27 in ♓ Pisces.
2 days after beginning of current draconic month in ♍ Virgo, the Moon is moving from the beginning to the first part of it.
9 days after previous North standstill on 16 March 2016 at 05:01 in ♋ Cancer, when Moon has reached northern declination of ∠18.206°. Next 5 days the lunar orbit moves southward to face South declination of ∠-18.239° in the next southern standstill on 30 March 2016 at 22:12 in ♐ Sagittarius.
After 12 days on 7 April 2016 at 11:24 in ♈ Aries, the Moon will be in New Moon geocentric conjunction with the Sun and this alignment forms next Sun-Moon-Earth syzygy. | 0.83659 | 3.277323 |
Neptune is the eighth planet from the Sun making it the maximum distant within the solar machine. This gas massive planet may additionally have fashioned a lot toward the Sun in early solar gadget records before migrating to its present function.
Neptune Planet Profile
Equatorial Diameter: 49,528 km
Polar Diameter: 48,682 km
Mass: 1.02 × 10^26 kg (17 Earths)
Moons: 14 (Triton)
Rings: 5 Orbit
Distance: four,498,396,441 km (30.10 AU)
Orbit Period: 60,a hundred ninety days (164.Eight years)
Effective Temperature: -214 °C
Discovery Date: September twenty third 1846
Facts About Neptune
- Neptune turned into not recognised to the ancients.
It isn’t always seen to the bare eye and changed into first located in 1846. Its function was decided the use of mathematical predictions. It turned into named after the Roman god of the ocean.
- Neptune spins on its axis very rapidly
Its equatorial clouds take 18 hours to make one rotation. This is due to the fact Neptune is not solid body.
- Neptune is the smallest of the ice giants
Despite being smaller than Uranus, Neptune has a extra mass. Below its heavy atmosphere, Uranus is product of layers of hydrogen, helium, and methane gases. They enclose a layer of water, ammonia and methane ice. The internal middle of the planet is product of rock.The atmosphere of Neptune is made from hydrogen and helium, with some methane.The methane absorbs purple mild, which makes the planet seem a cute blue. High, skinny clouds go with the flow inside the top atmosphere.
- Neptune has a totally active climate
Large storms whirl through its upper atmosphere, and high-pace winds track across the planet at up 600 meters in step with second. One of the largest storms ever visible became recorded in 1989. It turned into referred to as the Great Dark Spot. It lasted approximately five years.
- Neptune has a very skinny series of earrings
They are likely made from ice debris mixed with dirt grains and likely coated with a carbon-based substance.
- Neptune has 14 moons
The maximum thrilling moon is Triton, a frozen world that is spewing nitrogen ice and dirt particles out from beneath its surface. It become likely captured through the gravitational pull of Neptune. It is probably the coldest international in the sun system.Only one spacecraft has flown with the aid of Neptune.In 1989, the Voyager 2 spacecraft swept beyond the planet. It lower back the primary near-up photographs of the Neptune device. The NASA/ESA Hubble Space Telescope has also studied this planet, as have a number of floor-primarily based telescopes.
- Neptune has an exceedingly thick atmosphere constructed from 74% hydrogen, 25% helium and approximately 1% methane. Its atmosphere additionally carries icy clouds and the quickest winds recorded within the sun device. Particles of icy methane and minor gases inside the extremities of the environment give Neptune its deep blue shade. The placing blue and white features of Neptune also assist to distinguish it from Uranus.
- Neptune’s environment is subdivided into the decrease troposphere and the stratosphere with the tropopause being the boundary among the two. In the lower troposphere temperatures lower with altitude however they boom with altitude within the stratosphere. Hydrocarbons form hazes of smog that appear inside the complete upper ecosystem of Neptune and hydrocarbon snowflakes that form in Neptune’s environment soften earlier than they attain its surface due to the high pressure. | 0.897195 | 3.459297 |
Starspots and Transits
There was a great question about transits in response to my post about “What Factors Impact Transit Shape” so I thought I’d answer in a blog post.
Jean Tate asked:
Question: In the image of Venus transiting the Sun, there are sunspots. How common are sunspots on the Sun-like stars in the Kepler field? How do sunspots change the transit light curve? How are sunspots modeled?
Starspots are dark blotches on the surface of the star and are regions of intense magnetic activity. Their temperature are lower than the rest of the photosphere which gives them their dark appearance. These blemishes are transitory and last anywhere from hours to months. They are an indication of the magnetic activity of the star, and the Sun goes through an 11-year cycle where the number of starspots (or sunspots as we call them on the Sun) changes. The more active the Sun, the more sunspots visible on its surface.
If you viewed the transit of Venus last July, there were several sunspots on the surface of the Sun which you can see in the image below.
On the Sun we can actually spatially resolve the sunspots, but on other stars we can’t. So for Kepler that is monitoring stars thousands of light years away, we detect starspots through the light curve. As the star rotates, starspots will come in and out view causing changes in the star’s brightness. The pattern in the star’s light curve will repeat once per rotation period of the star. At the equator, the Sun rotates every 24.47 days much longer than the short few-tens of hours that a planet transit lasts.
If the transiting planet doesn’t cross over a starspot we get a fairly rounded U-shaped symmetric bottom to the transit as you can see below for a set of simulated planet transits.
Because planet transits last a few to tens of hours and stars rotate over a period of days, you can think of the starspot as effectively stationary with the planet moving across it during the transit. The starspot is not as bright as the surrounding areas of the photosphere, so when the planet transits across that starspot the lightcurve gets a bit brighter than average and you don’t see a symmetric bottom to your transit. So you see a small positive bump in the transit lightcurve. In the observed transit shown below, the planet crosses a starspot during the second half of the transit.
Planets transiting starspots can be extremely useful. Those transits have been recently used to measure the alignment of the planet’s orbit to the rotation axis of the star. In our Solar System, the planets are about 8 degrees off from being aligned with the Sun’s rotation axis, but other planetary systems are severely misaligned.
If the planetary system is aligned with the star’s rotation axis, then the planet transit path is a chord that always crosses over the starspot when it is in view, so you will see many of the planet transits having the signature of a starspot crossing. Because the star is also rotating between transits, the starspot will be likely be in a different place on the star’s disk the next time the planet comes around so you will see the timing of the bump change from transit to transit. If the orbit is misaligned, then only when the starspot is in a position crossing the planet’s transit chord across the star’s surface will there be a positive bump in the transit lightcurve. So the next several transits the planet has extremely low chances of being timed such that the starspot is in the same position on the star’s disk for the event to repeat. So you should see no starspot signal in subsequent transits. You can see this effect below in the figure from Sanchis-Ojeda et al 2012. | 0.891583 | 3.86921 |
Astronomers Open Window to Europa's Ocean
With data collected from the mighty W. M. Keck Observatory, California Institute of Technology (Caltech) astronomer Mike Brown — known as the Pluto killer for discovering a Kuiper-belt object that led to the demotion of Pluto from planetary status — and Kevin Hand from the Jet Propulsion Laboratory (JPL) have found the strongest evidence yet that salty water from the vast liquid ocean beneath Europa’s frozen exterior actually makes its way to the surface.
The data suggests there is a chemical exchange between the ocean and surface, making the ocean a richer chemical environment, and implies that learning more about the ocean could be as simple as analyzing the moon’s surface. The work is described in a paper that has been accepted for publication in the Astronomical Journal.
The findings were derived from spectroscopy delivered from the Keck Observatory, which operates the largest and most scientifically productive telescopes on Earth.
“We now have the best spectrum of this thing in the world,” Brown says. “Nobody knew there was this little dip in the spectrum because no one had the resolution to zoom in on it before.”
Ten-meter Keck II, fitted with Adaptive Optics (AO) to adjust for the blurring effect of Earth’s atmosphere, and its OH-Suppressing Infrared Integral Field Spectrograph (OSIRIS) produced details not capable of collection when NASA’s Galileo mission (1989-2003) was sent to study Jupiter and its moons.
“We now have evidence that Europa’s ocean is not isolated — that the ocean and the surface talk to each other and exchange chemicals,” says Brown, the Richard and Barbara Rosenberg Professor and professor of planetary astronomy at Caltech. “That means that energy might be going into the ocean, which is important in terms of the possibilities for life there. It also means that if you’d like to know what’s in the ocean, you can just go to the surface and scrape some off.”
“The surface ice is providing us a window into that potentially habitable ocean below,” says Hand, deputy chief scientist for solar system exploration at JPL.
Since the days of the Galileo mission, when the spacecraft showed that Europa was covered with an icy shell, scientists have debated the composition of Europa’s surface. The infrared spectrometer aboard Galileo was not capable of providing the detail needed to definitively identify some of the materials present on the surface. Now, using current technology on ground-based telescopes, Brown and Hand have definitively identified a spectroscopic feature on Europa’s surface that indicates the presence of a magnesium sulfate salt, a mineral called epsomite, that could only originate from the ocean below.
“Magnesium should not be on the surface of Europa unless it’s coming from the ocean,” Brown says. “So that means ocean water gets onto the surface, and stuff on the surface presumably gets into the ocean water.”
Europa’s ocean is thought to be 100 kilometers deep and covers the entire globe. The moon remains locked in relation to Jupiter, with the same hemisphere always leading and the other trailing in its orbit. The leading hemisphere has a yellowish appearance, while the trailing hemisphere seems to be splattered and streaked with a red material.
The spectroscopic data from that red side has been a cause of scientific debate for 15 years. It is thought that one of Jupiter’s largest moons, Io, spews volcanic sulfur from its atmosphere, and Jupiter’s strong magnetic field sends some of that sulfur hurtling toward the trailing hemisphere of Europa, where it sticks. It was also clear from Galileo’s data that there is something other than pure water ice on the trailing hemisphere’s surface. The debate has focused on what that other something is — i.e., what has caused the spectroscopic data to deviate from the signature of pure water ice.
“From Galileo’s spectra, people knew something was there besides water. They argued for years over what it might be — sodium sulfate, hydrogen sulfate, sodium hydrogen carbonate, all these things that look more or less similar in this range of the spectrum,” says Brown. “But the really difficult thing was that the spectrometer on the Galileo spacecraft was just too coarse.”
Brown and Hand decided that the latest spectrometers on ground-based telescopes could improve the data pertaining to Europa, even from a distance of about 400 million miles. Using the Keck II telescope on Mauna Kea, they first mapped the distribution of pure water ice versus anything else on the moon. The spectra showed that even Europa’s leading hemisphere contains significant amounts of nonwater ice. Then, at low latitudes on the trailing hemisphere — the area with the greatest concentration of the nonwater ice material — they found a tiny dip in the spectrum that had never been detected before.
The two researchers racked their brains to come up with materials that might explain the new spectroscopic feature, and then tested everything from sodium chloride to Drano in Hand’s lab at JPL, where he tries to simulate the environments found on various icy worlds. “We tried to think outside the box to consider all sorts of other possibilities, but at the end of the day, the magnesium sulfate persisted,” Hand says.
Some scientists had long suspected that magnesium sulfate was on the surface of Europa. But, Brown says, “the interesting twist is that it doesn’t look like the magnesium sulfate is coming from the ocean.” Since the mineral he and Hand found is only on the trailing side, where the moon is being bombarded with sulfur from Io’s, they believe that there is a magnesium-bearing mineral everywhere on Europa that produces magnesium sulfate in combination with sulfur. The pervasive magnesium-bearing mineral might also be what makes up the nonwater ice detected on the leading hemisphere’s surface.
Brown and Hand believe that this mystery magnesium-bearing mineral is magnesium chloride. But magnesium is not the only unexpected element on the surface of Europa. Fifteen years ago, Brown showed that Europa is surrounded by an atmosphere of atomic sodium and potassium, presumably originating from the surface. The researchers reason that the sodium and potassium chlorides are actually the dominant salts on the surface of Europa, but that they are not detectable because they have no clear spectral features.
The scientists combined this information with the fact that Europa’s ocean can only be one of two types — either sulfate-rich or chlorine-rich. Having ruled out the sulfate-rich version since magnesium sulfate was found only on the trailing side, Brown and Hand hypothesize that the ocean is chlorine-rich and that the sodium and potassium must be present as chlorides.
Therefore, Brown says, they believe the composition of Europa’s sea closely resembles the salty ocean of Earth. “If you could go swim down in the ocean of Europa and taste it, it would just taste like normal old salt,” he says.
Hand emphasizes that, from an astrobiology standpoint, Europa is considered a premier target in the search for life beyond Earth; a NASA-funded study team led by JPL and the Johns Hopkins University Applied Physics Laboratory have been working with the scientific community to identify options to explore Europa further. “If we’ve learned anything about life on Earth, it’s that where there’s liquid water, there’s generally life,” Hand says. “And of course our ocean is a nice salty ocean. Perhaps Europa’s salty ocean is also a wonderful place for life.” | 0.879093 | 4.00838 |
In the past 20 years, thousands of planets have been discovered orbiting other stars. Far from resembling families of planets like Earth and its companions, most of these discoveries have made our solar system look like the odd one out.
But now astronomers have announced a new exoplanet that looks surprisingly familiar. The exoplanet, 51 Eridani b, looks a lot like Jupiter – or at least the way we think Jupiter looked when it was much younger. Studying this juvenile version of our familiar neighbour will help us to unlock Jupiter’s past and find out more about the circumstances of its birth.
Bright Young Thing
The newly discovered exoplanet is a gas giant in orbit around a star 96 light years away. The star and its planetary system are estimated to be just 20m years old, less than a hundredth of the age of our solar system. This means that while Jupiter is a fully-grown planet, 51 Eridani b is still a teenager.
The youthfulness of 51 Eridani b was the key to its discovery. The planet has barely had time to cool down from its formation, which means that it is still bright enough to be directly imaged. Using the Gemini Planet Imager, a new instrument on the 8-meter Gemini South Telescope in Chile, an international team of astronomers was able to carefully block out the light from the parent star and spot the planet. The results have been published in the current issue of the journal Science.
Discovery image of the planet 51 Eridani b, taken in the near-infrared with the Gemini Planet Imager on December 18 2014. The bright central star has been mostly removed to enable the detection of the exoplanet. J. Rameau (UdeM) and C. Marois (NRC Herzberg)
The authors of the study estimate that 51 Eridani b is 2.5 times further from its star than Jupiter is from the Sun, meaning that if it was located in our solar system, it would sit between Saturn and Uranus. The planet is roughly the same size as Jupiter but being much denser has at least twice the mass.
Show Us What You’re Made Of
By studying how the amount of light emitted by the planet varies with colour (or wavelength), scientists are starting to learn about the planet’s composition. “We already know that the atmosphere is rich in methane,” said Mark Marley, a co-author on the paper and an astronomer at NASA Ames Research Centre. “This planet has an atmospheric composition that is the most similar to our own Jupiter of any directly imaged planet.”
The biggest difference between the two planets is the temperature: 51 Eridani b is a sweltering 450°C, while Jupiter is much more frosty, at -150°C. But as time passes and 51 Eridani b gradually cools down, it will start to look more and more like our gas giant neighbour.
The exoplanet provides a glimpse back in time to how Jupiter might have looked when it was just a few million years old. Studying planets like this could be the key to unlocking the secrets of our own solar system.
“In the solar system we have been trying to understand the formation and evolution of giant planets just by studying them as they are today,” said Marley. “By studying young Jupiters, we are catching them closer to their birth and thus we hope to be able to see more clues about the details of their formation.”
How Do Planets Form?
We know that planets are formed in the circular cloud of dust and gas that surrounds a newborn star, but the precise way in which this happens isn’t well understood. There are two main theories for the formation of gas giant planets: core-accretion, where material gradually clumps together into bigger and bigger pieces, and disc-instability, where there is rapid fragmentation into planet-size chunks as the circular cloud cools.
Artist’s impression of a planet forming within a gap in the dusty disc surrounding a young star. NASA/JPL-Caltech
Astronomers think that Jupiter formed through core-accretion, but until now, it had seemed like the odd one out. All of the young Jupiter-like exoplanets that had previously been discovered were too hot and bright for the core-accretion model to fit, suggesting that they formed via disc instability instead – 51 Eridani b is the first one that seems like it could have formed in the same way as Jupiter.
The First Of Many?
This is just the start, according to Marley. “Once we have more data we can begin to piece together the formation scenario for this planet and hopefully more planets that are yet to be discovered. Once we have a systematic view of many young giant planets we hope to understand planet formation much better than we do now.”
This is just the beginning for the GPI instrument, too, which is expected to make many more discoveries during its operational life. The young planets we hope it will find may hold the key to the history of our solar system. It may be only a teenager, but 51 Eridani b certainly has a lot to tell us. | 0.847934 | 3.827759 |
To make a planet, you need stuff.
Protoplanetary disks — cosmic frisbees of gas and dust orbiting young stars across the galaxy — spin out new planets. But the size of those planets depends on just how much material these disks have to give.
A team of scientists led by the University of Arizona has imaged a cluster of protoplanetary disks in the Orion Nebula and discovered that they are smaller than those previously studied in closer, less-dense regions. The smallness of these newly imaged disks suggests that making giant planets such as Jupiter (which is 2.5 times more massive than all the other planets in our solar system combined) could be especially difficult.
What’s more, the Orion Nebula looks a lot like other planet-forming regions in the Milky Way, meaning our own solar system likely formed in an Orion-like environment. The team’s findings have been published in the Astrophysical Journal.
The scientists used the largest telescope in the world, an interferometric array of radio telescopes in Chile called ALMA, to observe about 110 protoplanetary disks in the Orion Nebula in the deepest survey of the region yet.
“The general motivation for the whole field is that we want to understand more about how planets are formed,” says Josh Eisner, a UA professor of astronomy who led the study.
In their pursuit of that understanding, scientists have spent decades looking to star-forming regions such as Taurus, a mere 500 light-years away (as compared to Orion’s 1,344). While its nearby location makes a slice of the universe such as Taurus easier to observe with less-powerful telescopes, it’s not what one might call a “typical” planet-forming region.
Orion, on the other hand, with its many stars (and orbiting disks) clustered together in relatively small area, is typical. It requires a more powerful telescope to take sharp observations, but in terms of regions where planets — or entire solar systems — form, it’s a better model.
“Orion is not at all an oddball region. The disks there look a lot like what we think our solar system looked like when it was a protoplanetary disk,” Eisner says. “And now with the advent of ALMA, we can study regions like Orion well.”
Based on the images, the team — which also included astronomy and astrophysics graduate student Ryan Boyden, Steward Observatory postdoctoral researchers Nicholas Ballering and Min Fang, Steward Observatory associate astronomer Jinyoung Kim, and Lunar and Planetary Laboratory associate professor Ilaria Pascucci — was able to calculate the mass of protoplanetary disks in the Orion Nebula.
“Disk mass tells you how much stuff there is in the disk and that gives you a budget for what you can build out of it,” Eisner says. “And what we found was, in this region, mass is actually quite constraining.”
Unlike those studied in nearby regions such as Taurus, planet-forming disks in the Orion Nebula don’t have enough stuff to build large planets such as Jupiter, for which you would need tens of Earth masses. According to Eisner, this may mean that much of the stuff already has been used to make young planets. Disks in Orion also appear smaller in size than those in Taurus-like regions.
“It’s pretty tantalizing that Orion looks so different from all these lower-density, closer regions but it’s just one. We want to fill in the data with more of these high-density regions to see if they all look like Orion,” says Eisner, who is already seeking grant funding and telescope observing time to do so.
The discovery also will be tantalizing for those interested in what our solar system looked like as it was cooking some 5 billion years ago.
“The initial conditions for planet formation can tell us a lot about the constraints and how the process really unfolds,” Eisner says.
One theory about our solar system’s formation, called the Nice Model, argues that, early on, the configuration of the planets within a disk was small and compact until resonance finally flung Neptune and Uranus onto longer orbits.
The fact that the small, compact systems Eisner’s team observed in the Orion’s disks match up so nicely with the initial planetary configuration in the Nice Model, Eisner says, is a compelling hint at the origins of our solar system.
“The solar system probably formed in an Orion-like environment,” he says. “Now we’ve actually got an idea of what systems there look like.” | 0.902273 | 3.982449 |
The interstellar medium begins where the interplanetary medium of the Solar System ends. The solar wind slows to subsonic velocities at the termination shock, 90 – 100 astronomical units from the Sun. In the region beyond the termination shock, called the heliosheath, interstellar matter interacts with the solar wind.
Voyager 1, the farthest human-made object from the Earth (after 1998), crossed the termination shock December 16, 2004 and may soon enter interstellar space, providing the first direct probe of conditions in the ISM (Stone et al. 2005).
The Voyager 1 spacecraft is a 722 kg (1,590 lb) space probe launched by NASA on September 5, 1977 to study the outer Solar System and interstellar medium. Operating for 35 years, 6 months, and 20 days as of 25 March 2013, the spacecraft receives routine commands and transmits data back to the Deep Space Network. At a distance of about 123.48 AU (1.847×1010 km) as of March 2013, it is the farthest man-made object from Earth and is currently travelling in a previously unknown region of space. It is still unclear whether this region is part of interstellar space or an area within the Solar System. | 0.85001 | 3.334595 |
Korolev crater on Mars boasts an ice rink measuring over 80km wide—and it’s one of the most spectacular surface features on the Red Planet, as the latest image from the Mars Express spacecraft reveals.
Named after Russian rocket scientist Sergey Korolev, this incredible crater is located in the northern lowlands of Mars and just south of Olympia Undae—a large patch of dune-filled terrain that encircles the planet’s northern polar cap. It may look as if Korolev crater is filled with snow, but it’s actually ice. The impressive impact crater measures 82km across (82 kilometers), and at the center of the circle—it’s deepest point—the ice extends down for 1.1 miles (1.8 kilometers).
This stunning new photo of the crater was captured by the High Resolution Stereo Camera (HRSC) instrument on the European Space Agency’s Mars Express satellite, which has been in orbit around Mars for the past 15 years.
The image was stitched together from five distinct strips, each of which was captured during a different orbit this past April. The image was processed to show how Korolev crater appears when viewed from an angle, and colour corrected to show how it would appear to a human observer. An overhead view (below) and topographical view of the crater were also released by the ESA.
The ice within Korolev crater is a permanent feature, despite the six-month-long northern summer on Mars. It’s an example of a cold trap; the floor of the crater is quite deep, lying about 1.2 miles (1.9 kilometers) vertically beneath the rim. The ESA explains further:
The very deepest parts of Korolev crater, those containing ice, act as a natural cold trap: the air moving over the deposit of ice cools down and sinks, creating a layer of cold air that sits directly above the ice itself.
Behaving as a shield, this layer helps the ice remain stable and stops it from heating up and disappearing. Air is a poor conductor of heat, exacerbating this effect and keeping Korolev crater permanently icy.
Should humans ever settle on Mars, this region might make for a sweet spot. Water is scarce on the Red Planet, so this polar region, with its extensive ice caps, could provide an ample supply of the precious liquid. Just as importantly, Korolev crater would provide a venue for the most epic game of hockey in the history of the Solar System. | 0.819221 | 3.692892 |
A gassy insulating layer beneath the icy surfaces of distant celestial objects could mean there are more oceans in the universe than previously thought.
Computer simulations provide compelling evidence that an insulating layer of gas hydrates could keep a subsurface ocean from freezing beneath Pluto’s icy exterior, according to a study published in the journal Nature Geoscience.
In July 2015, NASA’s New Horizons spacecraft flew through Pluto’s system, providing the first-ever close-up images of this distant dwarf planet and its moons. The images showed Pluto’s unexpected topography, including a white-colored ellipsoidal basin named Sputnik Planitia, located near the equator and roughly the size of Texas.
Because of its location and topography, scientists believe a subsurface ocean exists beneath the ice shell which is thinned at Sputnik Planitia. However, these observations are contradictory to the age of the dwarf planet because the ocean should have frozen a long time ago and the inner surface of the ice shell facing the ocean should have also been flattened.
Researchers at Japan’s Hokkaido University, the Tokyo Institute of Technology, Tokushima University, Osaka University, Kobe University, and at the University of California, Santa Cruz, considered what could keep the subsurface ocean warm while keeping the ice shell’s inner surface frozen and uneven on Pluto. The team hypothesized that an “insulating layer” of gas hydrates exists beneath the icy surface of Sputnik Planitia. Gas hydrates are crystalline ice-like solids formed of gas trapped within molecular water cages. They are highly viscous, have low thermal conductivity, and could therefore provide insulating properties.
The researchers conducted computer simulations covering a timescale of 4.6 billion years, when the solar system began to form. The simulations showed the thermal and structural evolution of Pluto’s interior and the time required for a subsurface ocean to freeze and for the icy shell covering it to become uniformly thick. They simulated two scenarios: one where an insulating layer of gas hydrates existed between the ocean and the icy shell, and one where it did not.
The simulations showed that, without a gas hydrate insulating layer, the subsurface sea would have frozen completely hundreds of millions of years ago; but with one, it hardly freezes at all. Also, it takes about one million years for a uniformly thick ice crust to completely form over the ocean, but with a gas hydrate insulating layer, it takes more than one billion years.
The simulation’s results support the possibility of a long-lived liquid ocean existing beneath the icy crust of Sputnik Planitia.
The team believes that the most likely gas within the hypothesized insulating layer is methane originating from Pluto’s rocky core. This theory, in which methane is trapped as a gas hydrate, is consistent with the unusual composition of Pluto’s atmosphere — methane-poor and nitrogen-rich.
Similar gas hydrate insulating layers could be maintaining long-lived subsurface oceans in other relatively large but minimally heated icy moons and distant celestial objects, the researchers conclude. “This could mean there are more oceans in the universe than previously thought, making the existence of extraterrestrial life more plausible,” says Shunichi Kamata of Hokkaido University who led the team.
Provided by: Hokkaido University
More information: Shunichi Kamata, Francis Nimmo, Yasuhito Sekine, Kiyoshi Kuramoto, Naoki Noguchi, Jun Kimura, Atsushi Tani. Pluto’s ocean is capped and insulated by gas hydrates. Nature Geoscience (2019). DOI: 10.1038/s41561-019-0369-8
Credit: © mode_list / Adobe Stock | 0.844954 | 3.99946 |
In 2016 when the Mekong river’s water was at its lowest level in 90 years, help for those dealing with the drought on the ground in South East Asia came from an unlikely place: low-Earth orbit.
While the ISS is high above us, at least some instruments on board are looking down at Earth. High-definition images taken from the space station’s unique vantage point have been used to aid the response efforts to natural disasters here on Earth. In 2013 scientists began testing an automated camera system designed to help researchers and officials respond to wildfires, floods, landslides, and other natural disasters.
Every 24 hours, the space station orbits our planet 16 times, giving it ample opportunity to snap photos and take data that can prove incredibly valuable. The camera on board can take three pictures each second, which are used to help humanitarian relief efforts, monitor environmental changes and track adaptation to climate change, as well as monitor natural disasters.
It’s part of a programme called SERVIR, which is a joint effort from NASA and the US Agency for International Development. From monitoring a tornado in Louisville, Missouri, to the eruption of the Langila volcano in Papau New Guinea, SERVIR has taken thousands of photographs during it’s time on the space station, and helped countless people on Earth.
You’d be forgiven for thinking the bones inside your body are rigid and unchanging, but the reality is they’re constantly responding to the stresses you put them under. So what happens when you remove that pressure?
Losing bone mass is one of the biggest threats to an astronaut’s health while they’re in space. In fact, it’s not dissimilar to the sort of bone loss people go through if they’re put on bed rest on Earth.
Research from the ISS’s predecessor, the Mir space station, showed that people lose on average 1-2 per cent of their bone mass every month they spend in microgravity. Astronauts on the ISS do two hours of exercise every day in an effort to counteract this and other effects of weightlessness.
Diet also plays a part, and experiments on the ISS have found vital new clues about how we can preserve bones in space, and in vulnerable people on Earth.
In an ESA experiment, astronauts on board the ISS followed both a normal diet with 11.5g salt each day and a low-salt diet with just 2.9g, for five days each. Results showed that on the higher salt diet more calcium is lost from the body – bad news for bones.
In another experiment bisphosphonate, a class of drugs that are used to treat osteoporosis, was tested by ISS crew members. Results so far show that the drug, combined with a serious amount of exercise, does appear to slow the loss of bone in astronauts, so may prove useful for long-duration space missions in the future.
As well as hosting research that will help astronauts and those of us stuck on Earth, sometimes the ISS plays a part in a discovery that is just plain spectacular.
Earlier this year, an experiment on the space station called Neutron star Interior Composition Explorer (NICER) found two stars that revolve around each other once every 38 minutes. One is a super dense spinning pulsar known as IGR J17062–6143. The other is a lighter white dwarf that spins around it as the larger star slowly hoovers it up.
Pulsars are incredibly dense and fast spinning stars, usually neutron stars, that emit beams of X-rays as they rotate. Both neutron stars and white dwarfs are the endpoints of a star’s life, formed when a star explodes in a supernova after burning up its fuel.
We can only detect a pulsar’s beam from Earth (or, in this case, low-Earth orbit) if it points towards us – think the light from a lighthouse as its lamp spins – so we’re lucky to have spotted this super speedy pair. The stars are closer to each other than the Moon is to Earth, and their 38-minute orbit makes them the fastest pulsar binary around.
NICER arrived on the ISS last year, and is tasked with making lots of detailed measurements of neutron stars, so these two record-breaking stars might not hang on to their title for long.
A single red romaine lettuce leaf might not be everyone’s idea of a tasty snack, but for someone who’s gone several months without any fresh food at all, it’s probably pretty appealing.
This particular red romaine lettuce leaf was grown in a Veggie Growth chamber designed especially for the ISS, and suited to the needs of growing food in weightlessness. The Veg-01 to 03 experiments are all about figuring out how to grow food without gravity, and in 2016 astronauts ate the first space-grown salad aboard the ISS.
There’s no real up or down in space, so roots grow all over the place. Normal water and soil would float away, so instead plants are grown in bags of substrate that NASA calls ‘plant pillows’, which deliver fertiliser and water to the plants as they need it. The seeds would float away too, so instead of being embedded in soil, they’re glued in place, with their shoot side facing ‘up’ and root side facing ‘down’. There’s no natural day and night cycle inside the space station, so LEDs are used instead, and encourage shoots to grow in the right direction.
As well as providing some much needed dietary variety for those aboard the ISS, growing food will be vital for any long-duration space missions – and has the added benefit of providing a bit of gardening therapy for any green-fingered astronauts.
Working in microgravity is not all downsides. In fact, scientists have used the unique environment on the space station to figure out better ways to create cancer drugs on Earth.
Microencapsulation is a technique that involves putting drugs or other agents inside a tiny biodegradable balloon-like capsule, which are then delivered directly to a tumour or site of infection using a specialised needle. These microcapsules can also contain contrast agents to help doctors see inside a patient’s body to better track a disease, and help treat it more effectively, or even genetically engineered DNA for use in gene therapy.
In an experiment on the space station called MEPS-II, scientists took advantage of microgravity to find better ways to make these microcapsules. Using altered fluid dynamics and surface interactions between the liquids, they made capsules containing different anti-cancer drugs, magnetic particles designed to be released on demand inside the body, and genetically engineered DNA.
Scientists on Earth have now been able to recreate these methods first used in space, resulting in better ways to make microcapsules that target tumours and resistant infections. NASA holds several patents for the techniques that should speed the development of cancer treatments, so more patients can avoid the side effects of chemotherapy and be treated with a targeted drug.
This article first appeared in issue 329 of BBC Focus magazine – subscribe and get the magazine delivered to your door, or download the BBC Focus app to read it on your smartphone or tablet. Find out more | 0.828911 | 3.257582 |
This article is mirrored from the ESA Web Portal.
Rosetta is set to complete its mission in a controlled descent to the surface of its comet on 30 September.
The mission is coming to an end as a result of the spacecraft’s ever-increasing distance from the Sun and Earth. It is heading out towards the orbit of Jupiter, resulting in significantly reduced solar power to operate the craft and its instruments, and a reduction in bandwidth available to downlink scientific data.
Combined with an ageing spacecraft and payload that have endured the harsh environment of space for over 12 years – not least two years close to a dusty comet – this means that Rosetta is reaching the end of its natural life.
Unlike in 2011, when Rosetta was put into a 31-month hibernation for the most distant part of its journey, this time it is riding alongside the comet. Comet 67P/Churyumov-Gerasimenko’s maximum distance from the Sun (over 850 million km) is more than Rosetta has ever journeyed before. The result is that there is not enough power at its most distant point to guarantee that Rosetta’s heaters would be able to keep it warm enough to survive.
Instead of risking a much longer hibernation that is unlikely to be survivable, and after consultation with Rosetta’s science team in 2014, it was decided that Rosetta would follow its lander Philae down onto the comet.
The final hours of descent will enable Rosetta to make many once-in-a-lifetime measurements, including very-high-resolution imaging, boosting Rosetta’s science return with precious close-up data achievable only through such a unique conclusion.
Communications will cease, however, once the orbiter reaches the surface, and its operations will then end.
“We’re trying to squeeze as many observations in as possible before we run out of solar power,” says Matt Taylor, ESA Rosetta project scientist. “30 September will mark the end of spacecraft operations, but the beginning of the phase where the full focus of the teams will be on science. That is what the Rosetta mission was launched for and we have years of work ahead of us, thoroughly analysing its data.”
Rosetta’s operators will begin changing the trajectory in August ahead of the grand finale such that a series of elliptical orbits will take it progressively nearer to the comet at its closest point.
“Planning this phase is in fact far more complex than it was for Philae’s landing,” says Sylvain Lodiot, ESA Rosetta spacecraft operations manager. “The last six weeks will be particularly challenging as we fly eccentric orbits around the comet – in many ways this will be even riskier than the final descent itself.
“The closer we get to the comet, the more influence its non-uniform gravity will have, requiring us to have more control on the trajectory, and therefore more manoeuvres – our planning cycles will have to be executed on much shorter timescales.”
A number of dedicated manoeuvres in the closing days of the mission will conclude with one final trajectory change at a distance of around 20 km about 12 hours before impact, to put the spacecraft on its final descent.
The region to be targeted for Rosetta’s impact is still under discussion, as spacecraft operators and scientists examine the various trade-offs involved, with several different trajectories being examined.
Broadly speaking, however, it is expected that impact will take place at about 50 cm/s, roughly half the landing speed of Philae in November 2014.
Commands uploaded in the days before will automatically ensure that the transmitter as well as all attitude and orbit control units and instruments are switched off upon impact, to fulfill spacecraft disposal requirements.
In any case, Rosetta’s high-gain antenna will very likely no longer be pointing towards Earth following impact, making any potential communications virtually impossible.
In the meantime, science will continue as normal, although there are still many risks ahead. Last month, the spacecraft experienced a ‘safe mode’ while only 5 km from the comet as a result of dust confusing the navigation system. Rosetta recovered, but the mission team cannot rule out this happening again before the planned end of the mission.
“Although we’ll do the best job possible to keep Rosetta safe until then, we know from our experience of nearly two years at the comet that things may not go quite as we plan and, as always, we have to be prepared for the unexpected,” cautions Patrick Martin, ESA Rosetta’s mission manager.
“This is the ultimate challenge for our teams and for our spacecraft, and it will be a very fitting way to end the incredible and successful Rosetta mission.”
Details regarding the end of mission scenario are subject to change. Further information will be announced once available.
Background information on ending Rosetta’s mission on the comet was published on the blog last year. | 0.844089 | 3.571676 |
High above the surface, Earth's magnetic field constantly deflects incoming supersonic particles from the sun. These particles are disturbed in regions just outside of Earth's magnetic field - and some are reflected into a turbulent region called the foreshock. New observations from NASA's THEMIS mission show that this turbulent region can accelerate electrons up to speeds approaching the speed of light. Such extremely fast particles have been observed in near-Earth space and many other places in the universe, but the mechanisms that accelerate them have not yet been concretely understood.
The new results provide the first steps towards an answer, while opening up more questions. The research finds electrons can be accelerated to extremely high speeds in a region farther from Earth than previously thought possible - leading to new inquiries about what causes the acceleration. These findings may change the accepted theories on how electrons can be accelerated not only in shocks near Earth, but also throughout the universe. Having a better understanding of how particles are energized will help scientists and engineers better equip spacecraft and astronauts to deal with these particles, which can cause equipment to malfunction and affect space travelers.
"This affects pretty much every field that deals with high-energy particles, from studies of cosmic rays to solar flares and coronal mass ejections, which have the potential to damage satellites and affect astronauts on expeditions to Mars," said Lynn Wilson, lead author of the paper on these results at NASA's Goddard Space Flight Center in Greenbelt, Maryland.
The results, published in Physical Review Letters on Nov. 14, 2016, describe how such particles may get accelerated in specific regions just beyond Earth's magnetic field. Typically, a particle streaming toward Earth first encounters a boundary region known as the bow shock, which forms a protective barrier between the sun and Earth. The magnetic field in the bow shock slows the particles, causing most to be deflected away from Earth, though some are reflected back towards the sun. These reflected particles form a region of electrons and ions called the foreshock region.
Some of those particles in the foreshock region are highly energetic, fast moving electrons and ions. Historically, scientists have thought one way these particles get to such high energies is by bouncing back and forth across the bow shock, gaining a little extra energy from each collision. However, the new observations suggest the particles can also gain energy through electromagnetic activity in the foreshock region itself.
The observations that led to this discovery were taken from one of the THEMIS - short for Time History of Events and Macroscale Interactions during Substorms - mission satellites. The five THEMIS satellites circled Earth to study how the planet's magnetosphere captured and released solar wind energy, in order to understand what initiates the geomagnetic substorms that cause aurora. The THEMIS orbits took the spacecraft across the foreshock boundary regions. The primary THEMIS mission concluded successfully in 2010 and now two of the satellites collect data in orbit around the moon.
Operating between the sun and Earth, the spacecraft found electrons accelerated to extremely high energies. The accelerated observations lasted less than a minute, but were much higher than the average energy of particles in the region, and much higher than can be explained by collisions alone. Simultaneous observations from the Wind and STEREO spacecraft showed no solar radio bursts or interplanetary shocks, so the high-energy electrons did not originate from solar activity.
"This is a puzzling case because we're seeing energetic electrons where we don't think they should be, and no model fits them," said David Sibeck, co-author and THEMIS project scientist at NASA Goddard. "There is a gap in our knowledge, something basic is missing."
The electrons also could not have originated from the bow shock, as had been previously thought. If the electrons were accelerated in the bow shock, they would have a preferred movement direction and location - in line with the magnetic field and moving away from the bow shock in a small, specific region. However, the observed electrons were moving in all directions, not just along magnetic field lines. Additionally, the bow shock can only produce energies at roughly one tenth of the observed electrons' energies. Instead, the cause of the electrons' acceleration was found to be within the foreshock region itself.
"It seems to suggest that incredibly small scale things are doing this because the large scale stuff can't explain it," Wilson said.
High-energy particles have been observed in the foreshock region for more than 50 years, but until now, no one had seen the high-energy electrons originate from within the foreshock region. This is partially due to the short timescale on which the electrons are accelerated, as previous observations had averaged over several minutes, which may have hidden any event. THEMIS gathers observations much more quickly, making it uniquely able to see the particles.
Next, the researchers intend to gather more observations from THEMIS to determine the specific mechanism behind the electrons' acceleration. | 0.869765 | 4.097372 |
Hot, young stars and cosmic pillars of gas and dust seem to crowd into NGC 7822. At the edge of a giant molecular cloud toward the northern constellation Cepheus, the glowing star forming region lies about 3,000 light-years away. Within the nebula, bright edges and dark shapes are highlighted in this colorful skyscape. The image includes data from narrowband filters, mapping emission from atomic oxygen, hydrogen, and sulfur into blue, green, and red hues. The atomic emission is powered by energetic radiation from the hot stars, whose powerful winds and radiation also sculpt and erode the denser pillar shapes. Stars could still be forming inside the pillars by gravitational collapse, but as the pillars are eroded away, any forming stars will ultimately be cutoff from their reservoir of star stuff. This field spans around 40 light-years at the estimated distance of NGC 7822.
The Rosetta spacecraft captured this remarkable series of 9 frames between March 27 and May 4, as it closed from 5 million to 2 million kilometers of its target comet. Cruising along a 6.5 year orbit toward closest approach to the Sun next year, periodic comet 67P/Churyumov-Gerasimenko is seen moving past a distant background of stars in Ophiuchus and globular star cluster M107. The comet's developing coma is actually visible by the end of the sequence, extending for some 1300 km into space. Rosetta is scheduled for an early August rendezvous with the comet's nucleus. Now clearly active, the nucleus is about 4 kilometers in diameter, releasing the dusty coma as its dirty ices begin to sublimate in the sunlight. The Rosetta lander's contact with the surface of the nucleus is anticipated in November.
Beautiful barred spiral galaxy M109, 109th entry in Charles Messier's famous catalog of bright Nebulae and Star Clusters, is found just below the Big Dipper's bowl in the northern constellation Ursa Major. In telescopic views, its striking central bar gives the galaxy the appearance of the Greek letter "theta", θ, a common mathematical symbol representing an angle. Of course M109 spans a very small angle in planet Earth's sky, about 7 arcminutes or 0.12 degrees. But that small angle corresponds to an enormous 120,000 light-year diameter at the galaxy's estimated 60 million light-year distance. The brightest member of the now recognized Ursa Major galaxy cluster, M109 (aka NGC 3992) is joined by three spiky foreground stars strung out across this frame. The three small, fuzzy bluish galaxies also on the scene, identified left to right as UGC 6969, UGC 6940 and UGC 6923, are possibly satellite galaxies of the larger M109.
This fire-breathing Dragon can fly. Pictured above yesterday, SpaceX Corporation's Falcon 9 rocket capped with a Dragon spacecraft lifted off from Cape Canaveral, Florida, USA. The successful launch was significant not only because it demonstrated that a private company has the ability to re-supply the International Space Station (ISS), but also that spaceflight has taken a significant step away from being an endeavor that only big governments can do with public money. If all continues as planned, the robotic Dragon will dock with the ISS this weekend. Over the next two weeks, the ISS Expedition 31 crew will then unload Dragon and refill it with used scientific equipment. In about three weeks, the ISS's robotic arm will then undock Dragon and move it to where it can fire its rockets. Soon thereafter the Dragon capsule is expected to reenter the Earth's atmosphere, deploy its parachutes, splash down in the Pacific Ocean off the coast of California, and be recovered.
Why does the Crab Nebula flare? No one is sure. The unusual behavior, discovered over the past few years, seems only to occur in very high energy light -- gamma rays. As recently as one month ago, gamma-ray observations of the Crab Nebula by the Fermi Gamma Ray Space Telescope showed an unexpected increase in gamma-ray brightness, becoming about five times the nebula's usual gamma-ray brightness, and fading again in only a few days. Now usually the faster the variability, the smaller the region involved. This might indicate that the powerful pulsar at the center of the Crab, a compact neutron star rotating 30 times a second, is somehow involved. Specifically, speculation is centered on the changing magnetic field that surely surrounds the powerful pulsar. Rapid changes in this field might lead to waves of rapidly accelerated electrons which emit the flares, possibly in ways similar to our Sun. The above image shows how the Crab Nebula normally appears in gamma rays, as compared to the Geminga pulsar, and how it then appeared during the recent brightening.
That's no sunspot. On the upper right of the above image of the Sun, the dark patches are actually the International Space Station (ISS) and the Space Shuttle Atlantis on mission STS-132. In the past, many skygazers have spotted the space station and space shuttles as bright stars gliding through twilight skies, still glinting in the sunlight while orbiting about 350 kilometers above the Earth's surface. But here, astrophotographer Thierry Lagault accurately computed the occurrence of a rarer opportunity to record the spacefaring combination moving quickly in silhouette across the solar disk. He snapped the above picture on last Sunday on May 16, about 50 minutes before the shuttle docked with the space station. Atlantis was recently launched to the ISS for its last mission before being retired.
Put on your red/blue glasses and gaze into this dramatic stereo view from the surface of the Moon. The 3D scene features Apollo 12 astronaut Pete Conrad visiting the Surveyor 3 spacecraft in November of 1969. The image was carefully created from two separate pictures (AS12-48-7133, AS12-48-7134) taken on the lunar surface. They depict the scene from only slightly different viewpoints, approximating the separation between human eyes. Combining images, one tinted red and the other blue-green, with the correct offset, produces the stereo effect when viewed using red/blue glasses, the red filter covering the left eye. The color filters guide each eye to see only the picture with the correct corresponding viewpoint. The particular pair of images chosen also required a slight tilt to optimize the stereo effect. While you've got those glasses on, web sources of astronomy and space science stereo images include the Mars Path Finder archive, a 3D Tour of the Solar System, and stereo experimenter Patrick Vantyune's own set of stereo images from the Apollo missions to the Moon.
For about 300 years Jupiter's banded atmosphere has shown a remarkable feature to telescopic viewers, a large swirling storm system known as The Great Red Spot. In 2006, another red storm system appeared, actually seen to form as smaller whitish oval-shaped storms merged and then developed the curious reddish hue. Now, Jupiter has a third red spot, again produced from a smaller whitish storm. All three are seen in this image made from data recorded on May 9 and 10 with the Hubble Space Telescope's Wide Field and Planetary Camera 2. The spots extend above the surrounding clouds and their red color may be due to deeper material dredged up by the storms and exposed to ultraviolet light, but the exact chemical process is still unknown. For scale, the Great Red Spot has almost twice the diameter of planet Earth, making both new spots less than one Earth-diameter across. The newest red spot is on the far left (west), along the same band of clouds as the Great Red Spot and is drifting toward it. If the motion continues, the new spot will encounter the much larger storm system in August. Jupiter's recent outbreak of red spots is likely related to large scale climate change as the gas giant planet is getting warmer near the equator.
The two brightest objects in the night sky appeared to go right past each other last week. On the night of May 19, Earth's Moon and the planet Venus were visible in the same part of the sky, and at closest approach were less than one degree apart. The conjunction was captured in the above image taken from near Quebec City, Quebec, Canada. Venus appears on the lower left of the above photo. The spires that appear to emanate from Venus are diffraction spikes caused by the camera itself. The image is so clear that craters on the Moon are resolved. Of course, the real physical distance between the two heavenly bodies was not unusually small -- the apparent conjunction was really just an illusion of perspective. Although Earth's Moon passes Venus once each month, such a close passing visible in the evening sky is more rare.
Rarely does a comet pass this close to Earth. Last week, dedicated astrofilmographers were able to take advantage of the close approach of crumbling 73P / Comet Schwassmann-Wachmann 3 to make time-lapse movies of the fast-moving comet. Large comet fragments passed about 25 times the Moon's distance from the Earth. The above time lapse movie of Fragment B of Comet Schwassmann-Wachmann 3 over Colorado, USA was taken during a single night, May 16, with 83 consecutive 49-second exposures. Some observers report being able to perceive the slight motion of the comet with respect to the background stars using only their binoculars and without resorting to the creation of fancy digital time-lapse movies. Fragment B of Comet Schwassmann-Wachmann 3 became just barely visible to the unaided eye two weeks ago but now is appearing to fade as the comet has moved past the Earth and nears the Sun. Many sky enthusiasts will be on the watch for a particularly active meteor shower tonight as the Earth made its closest approach to orbit of Comet Schwassmann-Wachmann 3 late yesterday.
What causes small waves in Saturn's rings? Observations of rings bordering the Keeler gap in Saturn's rings showed unusual waves. Such waves were first noticed last July and are shown above in clear detail. The picture is a digitally foreshortened image mosaic taken earlier this month by the robot Cassini spacecraft now orbiting Saturn. The rings, made of many small particles, were somehow not orbiting Saturn in their usual manner. Close inspection of the image shows the reason - a small moon is orbiting in the Keeler gap. The previously unknown moon is estimated to span about seven kilometers and appears to have the same brightness as nearby ring particles. The gravity of the small moon likely perturbs the orbits of ring particles that come near it, causing them to shimmy back and forth after the moon passes. Since inner particles orbit more quickly than outer particles, only the leading particles of the inner rings and the trailing particles of the outer rings show the wave effect.
High above planet Earth, a human helps an ailing machine. The machine, in this potentially touching story, is the Hubble Space Telescope, which is not in the picture. The human is Astronaut Steven L. Smith, and he is seen above retrieving a power tool from the handrail of the Remote Manipulator System before resuming work on HST in 1999 December. For most astronauts, space is not a place for relaxation and vacation, but rather a place for hard work. Since many space missions involve costly equipment and complicated experiments, astronauts are usually people of considerable knowledge and training. Although the hours may be long and work may be taxing, one frequently reported perk of working in space is the spectacular view.
Half-shadowed by the Earth, the Moon takes on a remarkable appearance against a field of stars in this intriguing telephoto picture recorded during a partial phase of last week's lunar eclipse. The picture is not a composite, but it has been digitally enhanced to bring out features covering a large range in brightness. On the Moon itself, surface details are visible in both the bright uneclipsed portion in direct sunlight, and the very much dimmer copper-colored, eclipsed region. Also much fainter than the Moon's sunlit surface, the background star field, along with the unusual lighting, seems to contribute to an eerie "3D" perception of the lunar orb. Canadian astrophotographer Jay Ouellet took the picture from l'Observatoire de la Decouverte in Val Belair, a suburb of Quebec City, where about 200 skygazers gathered to enjoy the celestial exposition.
Supernova remnant N132D shows off complex structures in this sharp, color x-ray image. Still, overall this cosmic debris from a massive star's explosive death has a strikingly simple horseshoe shape. While N132D lies 180,000 light-years distant in the Large Magellanic Cloud, the expanding remnant appears here about 80 light-years across. Light from the supernova blast which created it would have reached planet Earth about 3,000 years ago. Observed by the orbiting Chandra Observatory, N132D still glows in x-rays, its shocked gas heated to millions of degrees Celsius. Since x-rays are invisible, the Chandra x-ray image data are represented in this picture by assigning visible colors to x-rays with different energies. Low energy x-rays are shown as red, medium energy as green, and high energy as blue colors. These color choices make a pleasing picture and they also show the x-rays in the same energy order as visible light photons, which range from low to high energies as red, green, and blue.
How did orange soil appear on the Moon? This mystery began when astronaut Harrison Schmidt noticed the off-color patch near Apollo 17's Taurus-Littrow landing site in 1972. Schmidt and fellow astronaut Eugene Cernan scooped up some of the unusual orange soil for detailed inspection back on Earth. Pictured above is a return sample shown greatly magnified, with its discovery location shown in the inset. The orange soil contains particles less than 0.1 millimeter across, some of the smallest particles yet found on the Moon. Lunar geologists now think that the orange soil was created during an ancient fire-fountain. Detailed chemical and dating analyses indicate that during an explosive volcanic eruption 3.64 billion years ago, small drops of molten rock cooled rapidly into the nearly spherical colored grains. The origin of some of the unusual elements found in the soil, however, remains unknown.
M4 is a globular cluster visible in dark skies about one degree west of the bright star Antares in the constellation Scorpius. M4 is perhaps the closest globular cluster at 7000 light years, meaning that we see M4 only as it was 7000 years ago, near the dawn of recorded human history. Although containing hundreds of thousands of stars and spanning over 50 light-years, M4 is one of the smallest and sparsest globular clusters known. A particularly unusual aspect for a globular cluster is M4's central bar of stars. M4, pictured above, is one of the oldest objects for which astronomers can estimate age directly. Cluster white dwarfs appear to be at least nine billion years old - so ancient they limit the youth of our entire universe.
The dark dusty Keyhole Nebula gets its name from its unusual shape. Officially designated NGC 3324, the Keyhole Nebula is a smaller region superposed on the larger Eta Carina Nebula. These nebulae were created by the dying star Eta Carina, which is prone to violent outbursts during its final centuries. Noted and discussed as early as 1840 when a spectacular explosion became visible, the Eta Carina system now appears to be undergoing an unusual period of change. An emission nebula that contains much dust, the Keyhole Nebula is roughly 9,000 light years distant. This photogenic nebula can be seen in the south with even a small telescope. The Keyhole Nebula was recently discovered to contain highly structured clouds of molecular gas.
This panorama view of the sky is really a drawing. It was made in the 1950s under the supervision of astronomer Knut Lundmark at the Lund Observatory in Sweden. To create the picture, draftsmen used a mathematical distortion to map the entire sky onto an oval shaped image with the plane of our Milky Way Galaxy along the center and the north galactic pole at the top. 7,000 individual stars are shown as white dots, size indicating brightness. The "Milky Way" clouds, actually the combined light of dim, unresolved stars in the densely populated galactic plane, are accurately painted on, interrupted by dramatic dark dust lanes. The overall effect is photographic in quality and represents the visible sky. Can you identify any familiar landmarks or constellations? For starters, Orion is at the right edge of the picture, just below the galactic plane and the Large and Small Magellanic Clouds are visible as fuzzy patches in the lower right quadrant.
Newborn stars lie at the heart of the Orion Nebula, hidden from view by the dust and gas of the giant Orion Molecular Cloud number 1 (OMC-1). Sensitive to invisible infrared wavelengths, Hubble's recently installed NICMOS camera can explore the interior of OMC-1 detecting the infrared radiation from infant star clusters and the interstellar dust and atoms energized by their intense starlight. In this false color picture, stars and the glowing dust clouds which also scatter the starlight appear yellowish orange while emission from hydrogen gas is blue. The dramatic image reveals a wealth of details, including many filaments and arcs of gas and dust -- evidence of violent motions stirred-up by the emerging stars. The bright object near the center is the massive young star "BN" (named for its discoverers Becklin and Neugebauer). The pattern of speckles and ripples surrounding BN and other bright stars are image artifacts.
The largest, most violent star forming region known in the whole Local Group of galaxies lies in our neighboring galaxy the LMC. Were 30 Doradus at the distance of the Orion Nebula -- a local star forming region -- it would take up fully half the sky. Also called the Tarantula Nebula, the red gas indicates a massive emission nebula, although supernova remnants and dark nebula also exist in 30 Doradus. The bright knot of stars just below center is called R136 and contains many of the most massive, hottest, and brightest stars known. | 0.941949 | 3.99552 |
Recently, NASA’s Fermi Gamma-ray Space Telescope discovered no more, no less than 12 pulsars, and it also detected gamma ray pulse from 18 others. These findings are forcing scientists to rethink what we know about dying stars, as they totally underestimated the power of these stellar cilinders.
“We know of 1,800 pulsars, but until Fermi we saw only little wisps of energy from all but a handful of them,” says Roger Romani of Stanford University, Calif. “Now, for dozens of pulsars, we’re seeing the actual power of these machines.”
Pulsars are rotating neutron stars, highly magnetized, that emit a beam of electromagnetic radiation with a period of the pulse variating from 8.5 seconds to just 1.5 miliseconds. They are what remains when a massive star explodes. They’re also incredible cosmic dynamos and despite the fact that scientists don’t fully understand this process, they can say for sure that very intense electric and magnetic fields spin and accelerate particles to speeds very close to that of light.
Most pulsars were found because they emitted pulses at radio wavelength which are emitted from the pulsar’s poles. If these poles and the star’s spin axis are not alligned exactly, then the beams would be swept across the sky, meaning that we can detect them only if such a beam meats a radio telescope. But data is often inaccurate or biased because these telescopes are situated on Earth
“That has colored our understanding of neutron stars for 40 years,” Romani says. The radio beams are easy to detect, but they represent only a few parts per million of a pulsar’s total power. Its gamma rays, on the other hand, account for 10 percent or more. “For the first time, Fermi is giving us an independent look at what heavy stars do. “
“We used to think the gamma rays emerged near the neutron star’s surface from the polar cap, where the radio beams form,” addsAlice Harding of NASA’s Goddard Space Flight Center in Greenbelt, Md. “The new gamma-ray-only pulsars put that idea to rest.”
Now, scientists have their hands full with this new class of gamma-ray pulsars, which they believe arise far above the neutron star. Due to the fact that rotation powers their emissions they tend to slow down a bit as they “age”; however, Fermi picked up emissions from gamma rays from seven millisecond pulsars (which are called this way because they spin somewhere between 100 and 1000 times a second!!!). They tend to sometimes “break the rules”, and “cohabitate” with a normal star, residing in binary systems.
Here are some animations to give you a better and more visual understanding of this.
Quick Time animation
Credit: NASA/Fermi/Cruz deWilde
These gamma-ray pulsars show that gamma rays must form in a broader region than believed previously. Here, you can see the radio beams (green) never intersect Earth, but the pulsed gamma rays (magenta) do.
Credit: NASA/Goddard Space Flight Center Conceptual Image Lab
But gamma ray pulsars are no longer lighthouses, as pointed out here.
Credit: NASA/Dana Berry
Isolated pulsars slowly slow down their spin, but if a pulsar “lives” in a binary system with a normal star, it actually goes faster and faster. As a result, you could have a pulsar that spins in just a few miliseconds. How fast can they go?? It’s still uncertain. | 0.839027 | 4.095994 |
By Adam Hadhazy|May 2020
The U.S. Global Positioning System has changed how we operate spacecraft in low-Earth orbit. Now GPS is starting to do the equivalent for spacecraft flying beyond the GPS constellation, and someday possibly all the way to the moon, where positioning contributions from other nations could add up to stunning accuracy. Adam Hadhazy tells the story.
Before GPS receivers became standard issue on low-Earth orbit satellites, the spacecraft had limited information on where they were and where they were going. Control stations on the ground needed minutes or even hours to process radar signals bounced off of these LEO satellites to calculate position and velocity and then send that info back up to orbit. The advent of GPS changed the game, making precision navigation and timing information on board the satellites available in real time. The system provides key time-tagging for communications, Earth observations and other satellite services, while keeping those services available nearly 24/7 and slashing fuel use because satellites no longer have to be taken offline for large, station-keeping thruster burns.
For LEO spacecraft whizzing underneath the GPS constellation’s altitude of 20,200 kilometers, tuning into GPS was a straightforward affair of turning their receivers upward to collect the readily available rain of GPS signals pouring down toward Earth. Twenty years ago, researchers proved that this signal collection could actually be done above the GPS constellation. The trick was to feed on GPS scraps, as it were, by capturing the weak “spillover” signals from GPS satellites on the far side of Earth that beam right past the planet, missing their terrestrial target. The breakthrough of snagging this spillover led to the adoption of GPS aboard satellites in geostationary orbit, some 36,000 kilometers above the equator, and to demonstrating the capability as far out as halfway to the moon.
Now, for their next feat, researchers want to equip new spacecraft to benefit from GPS all the way at the moon and even down to its cratered surface. If successful, this capability would go a long way toward enhancing operations in what could one day be a very busy lunar environment.
“It’s really only been since late 2018, early 2019 where we could show that lunar was feasible,” says engineer Frank Bauer, a 30-year NASA veteran and now president of FBauer Aerospace Consulting Services in Maryland.
“What GPS has done for spacecraft in LEO has been phenomenal,” says Bauer. Likewise, “GPS could be transformative for lunar missions.”
Future endeavors could harness GPS to help build out a durable human presence in cislunar space between Earth and the moon. Envisioned enhancements include boosting autonomous spacecraft operation with real-time navigation and precise timing for formation flying, rendezvous and docking, station keeping, and more.
Extending the reach of GPS
For Bauer and others, getting to this point has been a two-decade personal quest.
Developed in the 1970s and then made available for civilian use in the 1980s, the U.S. Air Force-operated GPS constellation service was first demonstrated out to low-Earth orbit in 1982 by the Landsat-4 Earth-imaging satellite.
Bauer and colleagues at NASA’s Goddard Space Flight Center in Maryland realized that it might be possible to install GPS equipment on new satellites destined for duty out past the GPS constellation. These beyond-the-constellation GPS receivers would have to capture those spillover signals that spread from each GPS satellite along multiple radio beam pathways, called lobes. The main lobe of a GPS radio signal beam’s width forms a V-shape. While most of the main lobe hits Earth as intended, some of that “V” extends beyond the limb, or curve of the planet, and into empty space. Residual signal coming out of the transmitting antenna forms side lobes that pass well clear of Earth. Normally, engineers disregard side lobes as wasted energy. The side lobes are quite weak — only about 3% of the total signal strength, whereas the main lobe constitutes 97%. But so long as there is line of sight to these side lobes, and better yet a bit of spillover from the main lobe, a sufficiently sensitive receiver aboard a spacecraft on the opposite side of Earth from the GPS-transmitting satellite can detect the signal.
The initial big step for proving out this capability came when Bauer and colleagues piggybacked a GPS receiver on a satellite called OSCAR-40, short for the Orbiting Satellite Carrying Amateur Radio. The satellite was launched in 2000 for the Radio Amateur Satellite Corp., or AMSAT, where Bauer continues to serve as the vice president of human spaceflight programs. OSCAR-40 ultimately reached a maximum altitude of about 60,000 km and detected GPS signals at this rarefied height, marking the first-ever demonstration of GPS in this new regime.
The proof of principle was now in place. Next, creating reliable GPS beyond the constellation required the engineers to deal next with weak signals and situations in which few satellites are available. On Earth, receiving signals from three GPS satellites produces a rough position, and a fourth delivers accuracy to within meters. Getting out past the GPS constellation, though, satellite availability (through signal line of sight) can be poor because Earth tends to get in the way. So for those times when only a single GPS satellite is in view, the Goddard team developed a software package, dubbed GEONS (GPS-Enhanced On-board Navigation System). GEONS accepts a single GPS signal, combining that information with other onboard sensors, such as the accelerometers and gyroscopes in an inertial navigation system, to arrive at precise time and position solutions.
As for dealing with signal weakness, a terrestrial analog is the all-too-familiar problem of straying too far from a cell tower to maintain a strong connection. “The farther out you go, the poorer reception you have, so you’re going to have to augment what the receivers are capable of,” says Joel Parker, the positioning navigation and timing policy lead at Goddard, who joined NASA shortly before Bauer’s retirement from the agency in 2011 and whom Bauer later mentored for the role. “The real magic of this is to pick up signals that are really weak because of the losses that are inherent to that big of a distance.”
A mission selected for development by NASA five years after the OSCAR-40 breakthrough provided the vehicle to test out the GEONS software and the sensitive receivers and at far greater altitudes. The Magnetospheric Multiscale, or MMS, mission called for sending four octagonal satellites into space to measure the transfer of energy between the sun’s magnetic field and Earth’s for space weather forecasters. The MMS satellites would need to fly in a tight tetrahedral formation to measure the structure of these magnetic fields in three dimensions. GPS or a technology with its capabilities was mission-critical. “You can’t do formation flying unless you really know where you are continuously,” says Bauer, who had a long-standing interest in formation flying because of the exquisite navigation precision it requires. He and his colleagues quickly became involved in discussions with MMS engineers on the project.
Development work culminated in the Navigator GPS Receiver, which they loaded with the GEONS software and flew on each 3.5-meter-wide MMS satellite when they were launched together in 2015. The receivers proved highly capable, even at apogee on an elliptical orbit extending to 190,000 km, or about halfway to the moon. Today, the MMS spacecraft continue to fly synchronously with just 7.2 km separating them — the closest formation flying for spacecraft ever demonstrated, NASA says. “We’ve broken world records now with MMS,” says Bauer.
Precision through stability
As MMS was going through its early paces in orbit, the GOES-R weather satellite, the first of NOAA’s four next-generation Geostationary Operational Environmental Satellites, was launched in November 2016. The satellite (rechristened GOES-16 once aloft) became NOAA’s first geosynchronous satellite to be equipped with GPS. The satellite, now in the GOES-East slot for an optimal view of the Atlantic Ocean and Caribbean and Eastern side of the Americas, was built by Lockheed Martin under NASA’s management at Goddard.
The GOES program had originally provided funding for the OSCAR-40 experiment, recognizing the potential that GPS could have for precision weather forecasting. Bauer had been involved here as well, serving as an architect for the control system of the predecessors to the newest satellites.
In February 2019, the similarly equipped GOES-17 was declared operational in the GOES-West slot for a view of the Americas and the Eastern Pacific Ocean. Prior GOES generations had to perform station- keeping maneuvers every few weeks, taking the satellites offline for several hours at a time. Now, both GOES-16 and GOES-17 keep on obtaining multispectral images while performing minuscule thruster burns for station keeping with very minimal downtime.
“GPS navigation helps keep the spacecraft rock steady in terms of where it thinks it is,” says Parker.
GOES-16 and 17 keep a constant watch on tropical cyclones and other weather systems as they evolve, ultimately gathering four times the spatial resolution of prior GOES generations. “It’s like going from a standard-definition screenshot” with the other satellites “to a full-motion, high-definition movie” with the newest satellites, says Parker.
Bauer says the onboard GPS delivered even better stability than expected. “I would have been happy to get 100-meter performance at GEO,” says Bauer, “but what we have is like what you’ve got on the ground.” On Earth’s surface, GPS is typically accurate to within 5 meters, indeed matching the low end of one type range error with of the newest satellites.
Surprisingly to those who pioneered the technology, despite the success on GOES-16, GPS utilization remains scant among the several hundred satellites at GEO, says Parker. That said, companies such as Virginia-based General Dynamics (which built GOES-16’s receiver) are now offering commercial receivers for this orbital region, having licensed the NASA technology originally developed for Navigator.
James “JJ” Miller, deputy director of policy and strategic communications within the Space Communications and Navigation Program at NASA headquarters, hopes more companies and government program offices choose to adopt GPS beyond the GPS constellation, because better positioning could multiply the number of spacecraft able to safely operate in the increasingly congested GEO — just like how GPS has enabled commercial aircraft to fly closer together.
“If you had every GEO bird in the future equipped with GPS,” says Miller, “you could in essence create real estate in the space domain because you could reduce the separation distance between spacecraft.”
Realizing lunar GPS
The next step would be to extend GPS where humans haven’t trodden in nearly half a century.
In simulations run in 2018, based in large part on MMS and GOES-16 data, Bauer, Parker and colleagues worked out the number of GPS satellites that would be visible in the near-moon environment and what sort of signal strengths could be expected. The upshot: With relatively modest upgrades to existing post-constellation GPS equipment, lunar GPS appears eminently possible.
A more powerful receiving antenna will be required, perhaps with about 14 decibels of gain, a measure of the amount of power transmitted in a particular direction compared to an antenna radiating equally in all directions. Another element: including actuators to keep the antenna pointed at Earth to maximize line of sight, because the Earth-orbiting GPS constellation spans less than 10 degrees on the lunar sky. (For comparison, when viewed from Earth’s surface, the moon is half a degree in diameter.)
So far, so simple, and based on components already routinely incorporated into spacecraft. “It’s not cost-intensive,” adds Parker. The one pricey bit of equipment would be including atomic clocks, as are found in GPS satellites, aboard a lunar-bound, GPS-signal-receiving spacecraft. That second clock or clocks would be good for extremely precise timekeeping on the spacecraft’s end, which further cuts down on overall error. But the ultraprecise ticks from a single such clock — for instance, if installed on NASA’S proposed lunar Gateway station under NASA’s Artemis program — could be disseminated and received by any space vehicles in radio vicinity, Parker says.
Toward these ends is the currently deployed state-of-the-art, deep-space GPS unit, called NavCube, developed by colleagues of Parker’s at Goddard. NavCube is a 25-by-20-by-15 centimeter unit that weighs about 5 kilograms and is attached to the exterior of the International Space Station on the P3 truss segment. The device is part of a broader experiment to test out the feasibility of ultra-high-data X-ray communications, which would require precise timing, and is also expanding GPS capabilities in space. Unlike its predecessor, Navigator, flown on MMS, and which only received a single GPS frequency, NavCube receives both L1 and L2 signals, with L2 being a more accurate civil signal now available from 19 of the GPS constellation’s satellites.
(L3 is reserved for transmitting data on detected nuclear explosions, and L4 is not yet in service.) Continuing work on the ground at Goddard is looking into use of L5 signals, which would be twice as powerful and have wider beam width than L1 and L2 signals, and thus would provide increased visibility out at the moon.
Even more help could be on the way. Bauer, Parker, Miller and others are all working through the United Nations International Committee on Global Navigation Satellite Systems to foster interoperability among all six major GNSS, short for Global Navigation Satellite Systems. Besides GPS, the five other constellations are the European Union’s Galileo, Russia’s GLONASS, China’s BeiDou Navigation Satellite System, India’s NavIC and Japan’s Quasi-Zenith Satellite System. Adding in those constellations would triple the number of available satellites from the U.S. fleet of 27 (plus four on-orbit spares) to circa 100.
If it were possible to collect everyone’s GNSS signals, Bauer says accuracy at the moon would be on the order of 1 km — certainly useful. But if atomic-clock precision were incorporated into the lunar-bound spacecraft, or fed to it by the Gateway, for instance, the accuracy could improve to more like 100 meters. That accuracy should be sufficient to enable efficient, autonomous navigation through cislunar space toward the Gateway — the driver, the iron and the chip shot. The short putt or docking would then be handled by conventional means of radar, lidar and cameras. Excursions to the lunar surface could likewise count on GPS for most of the descent. “You probably switch from using GPS almost exclusively to lidar and then visual sensors to make sure you don’t hit any boulders or whatever as you come in for landing,” says Bauer.
Getting your bearings, at terra and luna
The first full demonstration of lunar GPS could come as soon as mid- to late 2021, when a Space Launch System rocket lifts off from Florida carrying an uncrewed Orion crew capsule on the Artemis-1 mission. Orion will orbit the moon for several days, capping a three-week deep-space jaunt. Orion will keep its GPS receivers on during both the outbound and inbound legs in order to characterize how much useful GPS signal is available.
For researchers who have long wanted precision positioning in deep space, being able to take the existing system with us, so to speak, versus having to construct a new system, would be welcome news. “Ten years ago, people talked about building another GPS constellation around the moon,” says Parker, the policy lead at Goddard. “Now we know we can use what already exists.”
Still, that build-out possibility has not been abandoned, given the expected limited precision of relying on GPS spillover from Earth, and in light of the advent of small satellites. One NASA concept, dubbed LunaNet, would consist of small sats that would augment terrestrial position and timing, while also routing communications among astronauts, explorers, astrophysicists or prospectors.
The more data brought to bear for position, velocity and time, the better, says Bauer. “Even ancient navigators fused navigation sensor data,” he says, “using a compass, chronometer and a sextant or the stars and sun to navigate the oceans.”
If the most ambitious plans for lunar activity next decade come to fruition, cislunar space could become just the latest ocean for our species to traverse. “We want to establish a sustainable human presence at the moon,” says NASA’s Miller. “There’s a lot of things we could do there in our lifetimes.” | 0.817874 | 3.460973 |
As you'll learn in this month's astronomy podcast, Jupiter and Saturn will compete with brilliant Venus for your attention in the late-evening sky.
For summer-lovers in the Northern Hemisphere, June is a great month. The solstice, when daylight is longest, comes on the 21st at 6:07 a.m. Eastern Daylight Time. But if you love to savor the night sky, this is a minimalist month because the nights are so short. For most of us evening twilight doesn’t end until 9 p.m. or later.
Of course, there's always plenty to see in the night sky after the Sun goes down, no matter what the time of year. S&T's astronomy podcast let's you know "what's up" this month.
Venus still reigns supreme in the west as darkness falls. It sets more than 2 hours after the Sun. You'll see two medium-bright stars nearby. They're quite a pair — as you'll learn during this month's podcast — and they'll slide toward the western horizon and deeper into the evening twilight as the weeks go by.
Once twilight fades, turn around and look on the opposite side of the sky to spot Jupiter. It's quite bright and easy to spot. Right now the King of Planets is situated in Libra, which is well known as a constellation in the zodiac but rather small in area with only modestly bright stars. Our astronomy podcast tells you how to use Jupiter to identify Libra's two brightest stars, gives you their fun, lyrical names, and explains why they once were part of a different constellation.
Late in June, a third bright planet — Saturn — rises into the evening sky. It reaches opposition this month, so you'll be able to enjoy three brights planets at once.
For all the celestial highlights in the weeks ahead, play or download this month's 8-minute-long astronomy podcast (linked below). | 0.808714 | 3.016317 |
Words and photos by Cory and Tanja Schmitz
The full galactic center of our home Milky Way galaxy is visible to southern hemisphere observers. While part of it is also visible in the lower-northern latitudes, grazing the southern horizon, the whole thing stretches high overhead in all its glory for those in the southern hemisphere. The galactic core rises early in the morning in the east/southeast in mid-late March and appears overhead earlier in the night as the season progresses. As it is the gravitational center of our galaxy, it has the largest concentration of stars, dust, and cosmic gasses, all orbiting a supermassive black hole…so it is a sight to see. The Milky Way appears brightest near the constellations of Sagittarius, Scorpius and Ophuichus.
Best times for viewing: April – October
The most prominent dark nebula in the southern sky, silhouetted against the rich star fields near the Southern Cross, is easily visible to the naked eye in dark locations. Lying in the constellation Crux, the Coalsack Nebula is an apparently huge dark nebula approximately 600 light-years away from earth. The Coalsack is not all black. It has a dim glow that comes from the reflection of the stars it obscures that can be seen in photographs. It is an impressive astrophotography target with standard camera lenses and a tracking mount.
Best times for viewing: February – August
The Carina Nebula is one of the largest diffuse nebulae in the sky, estimated between 6,500 and 10,000 light-years away from earth. This complex mixture of gas, also known as the Great Nebula in Carina, contains several open clusters and various other bright and luminous stars, such as the famous Eta Carinae system. This nebula is roughly 4 times the size and brightness of the more famous Orion nebula.
Best times for viewing: February – July
The largest known globular cluster in our Milky Way galaxy appears in the constellation Centaurus. This naked-eye visible southern-sky spectacle is estimated to contain approximately 10 million stars, while the largest globular cluster visible in northern latitudes, the Great Globular Cluster in Hercules (M13), is estimated to contain 300,000 stars.
Best times for viewing: March – August
This duo of irregular dwarf galaxies are magnificent and prominent features in the southern sky and often mistaken as terrestrial clouds to the naked eye. Both are members of the Local Group of galaxies, and are thought to orbit our own Milky Way galaxy.
The true distance between these two galaxies is 75,000 light years, while in the sky they only appear 21° apart. The LMC is estimated to lie 160,000 light-years from Earth, and the SMC around 200,000 light years distant.
The LMC contains a popular southern gem known as the Tarantula Nebula (30 Doradus). While another notable target viewed near the SMC is 47 Tucanae, a large globular cluster that is 16,700 light-years away from earth and can be seen with the naked eye. This cluster is noted for having a very bright and dense core, and is the 2nd brightest globular cluster in the night sky after Omega Centauri.
Best times for viewing: October – March | 0.826911 | 3.708787 |
X-rays Reveal Temperament of Possible Planet-Hosting Stars
A new X-ray study has revealed that stars like the Sun and their less massive cousins calm down surprisingly quickly after a turbulent youth. This result has positive implications for the long-term habitability of planets orbiting such stars.
A team of researchers used data from NASA’s Chandra X-ray Observatory and ESA’s XMM-Newton to see how the X-ray brightness of stars similar to the Sun behaves over time. The X-ray emission from a star comes from a thin, hot, outer layer, called the corona. From studies of solar X-ray emission, astronomers have determined that the corona is heated by processes related to the interplay of turbulent motions and magnetic fields in the outer layers of a star.
High levels of magnetic activity can produce bright X-rays and ultraviolet light from stellar flares. Strong magnetic activity can also generate powerful eruptions of material from the star’s surface. Such energetic radiation and eruptions can impact planets and could damage or destroy their atmospheres, as pointed out in previous studies, including Chandra work reported in 2011 and 2013.
Since stellar X-rays mirror magnetic activity, X-ray observations can tell astronomers about the high-energy environment around the star. The new study uses X-ray data from Chandra and XMM-Newton to show that stars like the Sun and their less massive cousins decrease in X-ray brightness surprisingly quickly.
Specifically, the researchers examined 24 stars that have masses similar to the Sun or less, and ages of a billion years or older. (For context, the Sun is 4.5 billion years old.) The rapid observed decline in X-ray brightness implies a rapid decline in energetic activity, which may provide a hospitable environment for the formation and evolution of life on any orbiting planets.
“This is good news for the future habitability of planets orbiting Sun-like stars, because the amount of harmful X-rays and ultraviolet radiation striking these worlds from stellar flares would be less than we used to think,” said Rachel Booth, a graduate student at Queen’s University in Belfast, UK, who led the study.
This result is different from other recent work on Sun-like and lower mass stars with ages less than a billion years. The new work shows that older stars drop in activity far more quickly than their younger counterparts.
“We’ve heard a lot about the volatility of stars less massive than the Sun, like TRAPPIST-1 and Proxima Centauri, and how that’s bad for life-supporting atmospheres on their planets,” said Katja Poppenhaeger, a co-author from Queen’s University and the Harvard-Smithsonian Center for Astrophysics (CfA) in Cambridge, Mass. “It’s refreshing to have some good news to share about potential habitability.”
To understand how quickly stellar magnetic activity level changes over time, astronomers need accurate ages for many different stars. This is a difficult task, but new precise age estimates have recently become available from studies of the way that a star pulsates using NASA’s Kepler and ESA’s CoRoT missions. These new age estimates were used for most of the 24 stars studied here.
Astronomers have observed that most stars are very magnetically active when they are young, since the stars are rapidly rotating. As the rotating star loses energy over time, the star spins more slowly and the magnetic activity level, along with the associated X-ray emission, drops.
“We’re not exactly sure why older stars settle down relatively quickly,” said co-author Chris Watson of Queen’s University. “However, we know it’s led to the successful formation of life in at least one case – around our own Sun.”
One possibility is that the decrease in rate of spin of the older stars occurs more quickly than it does for the younger stars. Another possibility is that the X-ray brightness declines more quickly with time for older, more slowly rotating stars than it does for younger stars.
A paper describing these results has been accepted for publication in the Monthly Notices of the Royal Astronomical Society, and is available online. The other co-authors are Victor Silva Aguirre from Aarhus University in Denmark and Scott Wolk from CfA. | 0.857377 | 3.997202 |
The world’s largest and most sensitive cosmic ray monitor, located in India, has recorded a burst of galactic cosmic rays which produced a crack in the Earth’s magnetic shield, according to scientists.
This is to say, a large fast moving coronal mass ejection (CME) from our Sun acting as an offensive front line making an opening in Earth’s magnetic field which then allowed an unusual large flow of galactic cosmic rays (GCR) to enter our atmosphere.
This event is unusual due to the fact that during times of high solar activity, the larger solar particles push aside the smaller but more harmful and damaging cosmic rays particles which produce high levels of radiation. Galactic cosmic rays come from outside our solar system generated from various celestial events such as exploding stars or supernovas occurring throughout our galaxy Milky Way.
The GRAPES-3 muon telescope located at the Tata Institute of Fundamental Research’s Cosmic Ray Laboratory in Ooty recorded a burst of galactic cosmic rays last year lasting for two hours.
The burst occurred when a giant cloud of plasma ejected from the solar corona, and moving with a speed of about 1.56 million per hour (2.5 million km) struck our planet, causing a severe compression of Earth’s magnetosphere from 11 to 4 times the radius of Earth. It triggered a severe geomagnetic storm that generated aurora borealis and radio signal blackouts in many high latitude countries, according to the study published in the journal Physical Review Letters this week.
Earth’s magnetosphere extends over a radius of 620,000 miles (1,000,000,000 kilometers), which acts as the first line of defense, shielding us from the continuous flow of solar and galactic cosmic rays, thus protecting life on our planet from these high intensity energetic radiations. | 0.876189 | 3.501458 |
A spacecraft taking the scenic route to Mercury successfully completed a crucial maneuver on its journey: a precisely choreographed swing past Earth.
The spacecraft, BepiColombo, represents a partnership between the European Space Agency (ESA) and the Japan Aerospace Exploration Agency (JAXA). The mission launched in October 2018, but its destination, Mercury, is very challenging to reach: Achieving orbit around the innermost planet requires a seven-year trajectory including complex planetary acrobatics in the form of a total of nine flybys.
BepiColombo executed the first of those nine flybys — the only one of its planet of origin — today (April 10) at 12:25 a.m. EST (425 GMT). The spacecraft came 7,887 miles (12,693 km) away from Earth, approaching at an angle designed to slightly reduce its speed with respect to the sun. That adjustment will allow BepiColombo to head deeper into the solar system.
BepiColombo is now out of Earth's shadow, and basking once again in sunlight!#FLYBYSUCCESS#EclipseEnds#BepiColomboEarthFlyby pic.twitter.com/szH2fwLuGWApril 10, 2020
The spacecraft's next dance will be with Venus, which BepiColombo will approach in October. The probe will loop around Earth's evil twin twice, this year and next, in order to further reduce its speed and put itself on track to meet its target, Mercury.
But even with three planetary adjustments, the trajectory to a successful Mercury stay is tricky. BepiColombo will conduct a series of six Mercury flybys between 2021 and 2025 before the small planet's gravity finally traps the probe in December 2025.
Once BepiColombo arrives at Mercury, it will split into two constituent spacecraft: JAXA's Mercury Magnetospheric Orbiter and ESA's Mercury Planetary Orbiter. The first probe will orbit relatively high above Mercury's surface and focus on studying the magnetosphere, the region of space governed by the planet's magnetic field. Scientists are excited for this research because, before spacecraft visited Mercury, experts didn't think the planet should be able to create a magnetic field. And the phenomenon remains confusing today.
The second BepiColombo probe will approach closer to Mercury's surface, and although it will contribute some magnetosphere measurements, it will focus on analyzing the planet's composition. Scientists hope this work will help them understand how Mercury — and, in turn, the entire solar system — formed.
Once BepiColombo arrives at its target, it will be just the third mission to study Mercury up close, which given its proximity to the sun is both a difficult target and a scorchingly hot one. NASA's Mariner 10 spacecraft flew past the tiny world three times in the 1970s; NASA's Messenger spacecraft orbited Mercury from 2011 to 2015. Each BepiColombo spacecraft's primary mission will last for one year.
- Photos of Mercury from NASA's Messenger spacecraft
- BepiColombo in pictures: A Mercury mission by Europe and Japan
- See amazing photos of Mercury by a doomed NASA spacecraft (video) | 0.835487 | 3.588375 |
The ninth edition of Ian Ridpath and Wil Tirion's famous guide to the night sky is updated with planet positions and forthcoming eclipses to the end of the year 2017. It contains twelve chapters describing the main sights visible in each month of the year, providing an easy-to-use companion for anyone wanting to identify prominent stars, constellations, star clusters, nebulae and galaxies; to watch out for meteor showers ('shooting stars'); or to follow the movements of the four brightest planets, Venus, Mars, Jupiter and Saturn. Most of the sights described are visible to the naked eye and all are within reach of binoculars or a small telescope. This revised and updated edition includes sections on observing the Moon and the planets, with a comprehensive Moon map. The Monthly Sky Guide offers a clear and simple introduction to the skies of the northern hemisphere for beginners of all ages.
Finding your way
Observing the planets
Observing the moon
Ian Ridpath is an astronomy writer and broadcaster, who is also editor of Norton's Star Atlas and the Oxford Dictionary of Astronomy. Wil Tirion is a celestial carographer, widely regarded as the leading exponent of his art in the world.
Reviews from previous editions:
"Wil Tirion's charts are justly famous. With Ian Ridpath's words, the combination is hard to beat."
- Popular Astronomy
"'For those who want to learn about the constellations and bright stars, this book is all that they'll need."
- Astronomy Now
"[...] charts big and detailed enough to be used easily [...]"
- Sky Publishing Corporation
"'What adds greatly to the value of the Guide is the obvious enthusiasm of the authors and their ability to convey it."
- Journal of the British Astronomical Association
"'I have not seen a better first guide to amateur astronomy."
- Malcolm Gough, The Observatory
"'It is an excellent practical introduction to finding one's way around the sky; [...] I can recommend this book very strongly."
- Robert Connon Smith, The Observatory
"'This popular guide, the product of collaboration between a writer and a cartographer, is now so well known that just a short review of the latest (7th) edition will suffice. Now updated through to 2011, the monthly sky maps (as well as focussing upon selected seasonal constellations) have been improved by the addition of star colours, while the outline of the Milky Way has been represented more realistically than before. The stellar magnitude steps are now more refined, with increments of 0.5 mag. [...] The planetary and eclipse notes, again arranged month by month, will help even the deskbound astronomer to avoid missing any important event. [...] The Monthly Sky Guide is highly recommended, and remains good value for money."
- The Observatory | 0.825572 | 3.306832 |
What impact does the detection of gravitational waves have on biblical creation?
Published: 16 February 2016 (GMT+10)
- Gravitational waves as predicted by Einstein were observed by the LIGO observatories for the first time on September 14, 2015.
- The detection strongly supports Einstein’s general theory of relativity published in 1916 where Einstein predicted such a phenomenon. No evidence for violation of general relativity was observed.
- A binary pair of black holes were observed to coalesce—the first time their existence confirmed.
- Their distance, determined from luminosity, is about 1.3 billion light-years.
- The black holes had masses of 36 M⊙ (mass of Sun) and 29 M⊙ before coalescence and 62 M⊙ after they combined. An equivalent of 3 M⊙ was radiated away as gravitational waves.
- There is very high confidence that the event seen at two widely separated sites must be real. The quality of the detected signals are high and were the same at each site.
- This is, in principle, repeatable (with other binary sources) and therefore is operational science. No fudge factors were invoked.
- The laws of physics used are the created laws of our God.
- The detection provides strong confirmation that the current value of the speed of light has not changed since creation. Therefore the idea of c-decay is ruled out.
- There are other more plausible solutions to the biblical creationist starlight-travel-time problem.
- Big bang cosmology is not operational science. This observation in no way strengthens claims that the alleged big bang happened. The big bang necessarily still needs many unverifiable fudge factors. It is still unreasonable.
The discovery of gravitational waves
On 14 September 2015 at 09:50:45 UTC the two gravitational wave detectors of the Laser Interferometer Gravitational-Wave Observatory (LIGO)—one at Hanford, Washington and the other at Livingston, Louisiana—simultaneously observed a transient gravitational-wave signal. The signal exhibited the classic waveform predicted by Einstein’s general relativity theory for a binary black hole merger, sweeping up in frequency from 35 to 250 Hz, and exhibited a peak gravitational-wave strain of 1.0 × 10−21 at the detectors.1
The two detectors recorded the same signal, which matched the predicted waveform for the inspiral and merger of a pair of black holes and the ringdown of the resulting single black hole. The signal was observed with a matched-filter signal-to-noise ratio of 24 and a false alarm rate estimated to be less than 1 event per 203,000 years, equivalent to a statistical significance greater than 5.1σ (where 1σ represents 1 standard deviation).2 In other words, the detection is highly likely to be real.
The source lies at a luminosity distance of about 1.3 billion light-years corresponding to a redshift z ≈ 0.09.3 The two initial black hole masses were 36 M⊙ and 29 M⊙,4,5 and the final black hole mass is 62 M⊙, with the equivalent of 3 M⊙ radiated as gravitational waves. The observations demonstrate for the first time the existence of a binary stellar-mass black hole system but, more importantly, the first direct detection of gravitational waves and the first observation of a binary black hole merger.
The results were published6 in Physical Review Letters (PRL) on 11 February 2016 with a fanfare of public announcements. Interestingly some of my colleagues at the university where I work, which has researchers involved in this discovery, asked why not publish in one of the more prestigious journals Science or Nature? Possibly PRL was a faster option to publish knowing that over one thousand people had to keep silent prior to publication, and Science and Nature have a much longer lead time to publication. Nevertheless it didn’t work, as atheopath Lawrence Krauss tweeted more than a month ago that a detection was confirmed and from that time rumours spread.
The observations are shown in Fig. 1. There is illustrated the waveforms detected by both LIGO detectors, which are located on opposite sides of continental USA, and separated by a distance that takes light about 10 ms to traverse.7 The gravitational-wave event, labelled GW150914,8 was first observed at the Livingston site (L1) and about 7 ms later observed at the Hanford site (H1). The waveforms were extracted by applying a template matched-filter, derived from a general relativistic calculation. The results from the two sites overlap extremely well and have a very high signal-to-noise ratio.
Unlike the BICEP2 South Pole Telescope fiasco in 2014,9 with a claimed detection of primordial gravitational waves from the supposed big bang inflation epoch, which was subsequently retracted in 2015,10 this detection seems to be very robust. And though the laser interferometers do have a very small likelihood of a false positive, produced by random noise with the same type of waveform, getting that result in two locations, separated by approximately the light travel time between the two sites, is extremely improbable.
Figure 2 illustrates the scenario of a black hole binary inspiral merger. The unfiltered waveform is shown in the frame below the pictures. This unfiltered waveform shows the expected disturbance to spacetime as a function of time as the black holes spiral together. The bottom frame plots the separation between the two black holes as a function of time as well as their relative velocity as a fraction of the speed of light.
One significant feature of this inspiral, as expected from modelling with general relativity, is the final phase of ringing during the ringdown. This shows a classic loss (dissipation) of energy from the system that is well understood in laboratory physics. This feature was predicted a few decades ago and is the expected classic signature of such a merger. So when I saw this, with such a high signal-to-noise ratio, I was immediately convinced that this was indeed a real detection.
On a personal note, the detection of gravitational waves means that a prediction I made in 2006 was wrong. Hulse and Taylor received the physics Nobel Prize in 1993 for their discovery, in 1974, that the neutron star binary PSR B1913+16—where one is also a pulsar emitting a radio signal—showed a loss of energy as gravitational radiation, as the two stars slowly moved towards each while spiraling around their common centre. This was recorded for several decades, exquisitely confirming what Einstein predicted. But no gravity waves were detected from that source, and that led to my prediction, based on the cosmology of Carmeli, where I reasoned that gravitational waves did not travel as waves through vacuum, though gravitational energy from the binary PSR B1913+16 was indeed lost to space as heat.11 But, alas, I now admit I was wrong.
This discovery is consistent with Einstein’s idea that spacetime can be thought of as a fabric that ‘waves’. In this case metrical distortions of spacetime can propagate through it, travelling at the speed of light (c). This is further support to Einstein’s general theory of relativity, which already has been very successfully tested in the local lab and in our solar system. Time keeping with GPS clocks is one very important example. The clocks on the GPS satellites at an altitude of about 20,200 km need corrections for both special and general relativistic effects, which amount to about 38 millionths of a second per day. It’s not much, yet it is a real measurable effect that would result in huge errors in GPS results if not corrected for. As a result we would classify this as operational science. And so is gravitational wave detection from coalescing binary black holes, or any other very dense objects that might be detected in the future.
Even though this type of measurement cannot be observed within our solar system, where humans may be able to directly go, these observations are, in principle, repeatable—not with that particular binary pair, but others like it. Such repeatable observations are one aspect of what we call operational science, even though we cannot directly interact with the black holes under investigation.12 This is similar to the observed energy loss from the neutron star binary pair for which Hulse and Taylor received their Nobel Prize. It is repeatable and consistent with robust physics testable on earth, though in a different area of application.
Creation or big bang science?
Big bang cosmology is not operational science. The assumed big bang origin of the universe from a universal singularity13 (not a black hole), which is a fancy term for nothing,14 is not repeatable science. Nor are there other universes that we can observe to test how a typical universe began in a big bang or otherwise.
The failed BICEP2 claim of detection of primordial gravitational waves and the ‘smoking gun’ evidence of the inflation epoch,9,10 illustrates the problem. The claim at the time was that it was ‘smoking gun’ evidence. That is an explicit admission that the event itself was not observed, but unobserved forensic or potentially circumstantial evidence after the fact.
Then there is the problem of degeneracy.15 In astrophysics and cosmology this means that there are a plethora of possible theories to explain the same cosmological observations. Just detecting Cosmic Microwave Background (CMB) radiation, which was a big bang prediction of George Gamow in 1948, is not sufficient reason (evidence) to conclude that the big bang happened (at some moment in the unobserved past). You would have to show that all other possible causes for the CMB radiation are ruled out. Besides there is contradictory evidence that supports the idea that the CMB radiation is not even from the background16 and thus it can’t be leftover radiation from the big bang fireball, as is believed.
If contrary evidence was found that ruled out this gravitational wave detection then that should be seriously considered. But I think that that is unlikely. Ruling out the very unlikely possibility of gross fraud, by a lot of scientists involved in the discovery, it is hard to see that this could be anything else other than a genuine detection, since it has all the hallmarks of the laws of physics that we do understand. No unknown unknowns were invoked to get the observations to fit the theory. No evidence for violation of general relativity was observed.
Now, these laws of physics, are exquisitely designed laws from the hand of the Creator of this universe. The fact that the black hole system is so far away (admittedly there are some assumptions to derive that fact) and the same laws we have discovered on earth apply out there tells us of the consistency of those laws. They are the creation of an Intelligence, a Creator, and we are just discovering how wonderfully He made this universe.
I suspect that there will be a host of claims on the internet and in other news media that this discovery somehow validates the big bang origin of the universe. But, it doesn’t!
The standard big bang cosmology is based on the solution of Einstein’s field equations found by Friedmann and Lemaître, in the 1920s. Those same field equations were linearized in what is called the post-Newtonian approximation, and from that Einstein developed the theory for gravity waves propagating through spacetime. But there are many possible mathematical solutions of Einstein’s field equations for the whole universe, many of which have already been discarded, as not fitting what we observe. The existence of a solution does not mean it has any physical significance. Einstein himself obtained the Einstein static universe solution, which he later discarded. Because he had included the cosmological constant (Λ) to maintain a static universe, when he heard of Hubble’s 1929 discovery of an expanding universe he exclaimed that its inclusion was the biggest mistake of his career.
Every solution requires a set of assumptions, which are called boundary conditions. These are assumptions about the initial conditions, and in the case of the Friedmann-Lemaître solution it requires the cosmological principle, which is an assumption that states that the universe is isotropic and homogeneous, or uniform. That means that the matter density in the universe, on the large scale, is the same everywhere, and that there is no unique centre nor any boundary or edge to the universe. It also assumes the laws of physics are the same everywhere and at every epoch.
Biblical creationists would agree that the laws are the same at every place in the universe, but not necessarily at every epoch, because there was a very special Creation epoch—Creation week. Big bang cosmology also has an exception, at the big bang itself, which is effectively a miracle without any sufficient cause (or explanation).
Besides the issue of the topology of the universe—whether it has a unique centre and an edge—the cosmological principle has a few big problems. One of them is the ‘Axis of Evil’.17,18 This is the determination of a peculiar alignment of the temperature fluctuations found in the CMB radiation, from both the WMAP and the Planck satellites. Those data independently determined the same anomalous axis in the universe, aligned with the plane of our solar system, in the particular direction determined by the two points where the sun’s path crosses the earth’s equator each year.19 But such an extraordinary axis in space should not exist. The local physics of our solar system and that of the big bang fireball should have no connection. This refutes the homogeneity and isotropy requirement of the cosmological principle, and because it does so much damage to their theory, the big bang cosmologists have called it the ‘Axis of Evil’.
Another big problem that has developed as a consequence of acceptance of the standard ΛCDM big bang cosmology20 for the universe is the belief in dark energy and dark matter. Because the observations on the large-scale measurements in the universe21 do not fit the modern form of the Friedmann-Lemaître model, dark energy and dark matter22 were invoked to get agreement. Dark energy, a sort of anti-gravity, was put in via the cosmological constant (Λ) but dark matter was necessary to bolster the total amount of matter since the small amount of normal observed matter was insufficient to get the theory to agree with the observations. Dark energy and dark matter are unknowns to science and hence I call them fudge factors,23 unknown unknowns, or ‘gods of the gaps’24 for modern cosmology.
Interestingly, the calculation used to determine the masses of the merging black holes in the analysis of this week’s discovery employed the standard canonical speed of light, c.25 That is, it used the same constant value that we measure today. Does that tell us something? I think it does.
Some biblical creationists favour a much higher value for the speed of light in the past, from a time soon after creation of the universe, after which it decreased or decayed down to its current value (the concept is known as cdk, from c-decay). They use this supposed much higher value of c in the past as a solution of the biblical creationist light-travel time problem.26,27 But now this new discovery shows that, at a time in the past representative of a distance in the cosmos of 1.3 billion light-years, the value of the speed of light (c) was identical to today’s current value. Regardless of which creationist cosmology you like, the gravity waves observed in September 2015 must have left their source very soon after Creation week. Thus the cdk idea is thoroughly rejected.
What do we conclude? Einstein’s general relativity is further strengthened as good operational science with no fudge factors. Any change in the speed of light is rejected. Nevertheless there exist other much more plausible solutions to the biblical creationist starlight-travel-time problem.26,27,28,29 With a constant speed of light, general relativity theory gives us the needed clue that time is not an absolute in the universe, which means that much more time could have been available for light to travel to earth from the most distant sources, even within the 6,000 years since creation. There are no other implications that impact on biblical creationist explanations for the origin of the universe.
Update added 4 March 2016
In regards to some claims that the detection was faked, Science News reported this:30
For 5 months, LIGO physicists struggled to keep a lid on their pupating discovery. Ordinarily, most team members would not have known whether the signal was real. LIGO regularly salts its data readings with secret false signals called “blind injections” to test the equipment and keep researchers on their toes. But on 14 September 2015, that blind injection system was not running. Physicists had only recently completed a 5-year, $205 million upgrade of the machines, and several systems—including the injection system—were still offline as the team wound up a preliminary “engineering run.” As a result, the whole collaboration knew that the observation was likely real. “I was convinced that day,” González says.
Still, LIGO physicists had to rule out every alternative, including the possibility that the reading was a malicious hoax. “We spent about a month looking at the ways that somebody could spoof a signal,” Reitze says, before deciding it was impossible. For González, making the checks “was a heavy responsibility,” she says. “This was the first detection of gravitational waves, so there was no room for a mistake.” (emphasis added)
One of the researchers who works on the LIGO instruments is a personal friend of mine. Today he told me that the simulated false signals that they do inject for calibration purposes are not powerful enough to create the detected signal. He said that they just could not do it.
References and notes
- The laser interferometers used to detect these signals are about 4 km long. The strain sensitivity refers to the detection sensitivity in terms of the fractional change in length of the arms (ΔL1-ΔL2)/L. So any putative signal can be detected that results in an absolute change in the arm length of as little as a few parts in 10-19 m. That is about a ten thousandth of the diameter of a hydrogen nucleus, i.e. of a proton. Return to text
- Any detection with a statistical significance greater than 5 standard deviations is considered real. In this case the result is shown to be far above the background noise in the detection histogram. See Fig. 4 in Ref. 6. Return to text
- The luminosity of the source and its redshift were determined from the brightness of the source signal where standard big bang cosmology was applied. Nevertheless that choice of cosmology has little impact on the veracity of the detection. Return to text
- These are their masses in their own rest frames. Return to text
- M⊙ represents the mass of our sun, a solar mass unit. Return to text
- Abbott, B. P., et al., Observation of Gravitational Waves from a Binary Black Hole Merger, Phys. Rev. Lett. 116(6), 2016 | doi:http://dx.doi.org/10.1103/PhysRevLett.116.061102. Return to text
- 1 ms = 1 millisecond. Return to text
- GW means gravity wave and the date of the detection is included in the nomenclature. Return to text
- Hartnett, J.G., Has the ‘smoking gun’ of the ‘big bang’ been found?, March 2014; creation.com/bbgun. Return to text
- Hartnett, J.G., New study confirms BICEP2 detection of cosmic inflation wrong, February 2015; creation.com/inflation-wrong. Return to text
- Hartnett, J.G., and Tobar, M.E., Properties of gravitational waves in Cosmological General Relativity, Int. J. Theor. Phys. 45 (11):2213–2222, 2006. Return to text
- Even though I am calling this operational science, such science done in the cosmos, where the researchers have no local laboratory wherein they can interact with their experiments, is a weaker form of the science. Therefore a higher standard of evidence should be required before conclusions may be drawn. And even then the tentative nature of the science needs to be properly understood. Return to text
- Hartnett, J.G., The singularity—a ‘Dark’ beginning, July 2014, creation.com. Return to text
- Hartnett, J.G., An eternal quantum potential or an eternal Creator God, January 2016, biblescienceforum.com. Return to text
- Degeneracy in this context means there are multiple solutions that cannot be distinguished from observation. Return to text
- Hartnett, J.G., ‘Light from the big bang’ casts no shadows, Creation 37(1):50–51, 2015; see also biblescienceforum.com. Return to text
- Hartnett, J.G., CMB Conundrums, J. Creation 20(2):10–11, August 2006. Return to text
- Hartnett, J.G., Development of an ‘old’ universe in science, July 2015, biblescienceforum.com. Return to text
- This is when the sun is seen exactly overhead at the equator. It occurs only twice a year due to the tilt of the earth’s axis. As the earth travels around the sun, the sun is seen overhead at lower or higher latitudes. Twice a year at the summer and winter equinox, Earth’s equatorial plane passes through the centre of the sun. Those two points on the opposite sides of Earth’s orbit, in the plane of the orbits of the planets, describes a unique direction in space. Return to text
- CDM refers to cold dark matter. Return to text
- Type Ia supernova measurements, for example. Return to text
- Dark matter historically was invoked before this. It was found that is needed in spiral galaxies to get the dynamics of the rotation of the galaxies to fit standard theory. This then spread to galaxy clusters and super-clusters also. Return to text
- Hartnett, J.G., Big bang fudge factors, December 2014, biblescienceforum.com. Return to text
- Hartnett, J.G., Is dark matter the unknown god?, Creation 37(2):22–24, 2015, biblescienceforum.com. Return to text
- Canonical speed of light is defined as c = 299,792,458 m/s. Return to text
- Hartnett, J.G., Starlight and time: Is it a brick wall for biblical creation?, July 2015, biblescienceforum.com. Return to text
- Hartnett, J.G., The Lecture: Starlight and time—Is it a brick wall for biblical creation?, July 2015, biblescienceforum.com. Return to text
- Hartnett, J.G., Solutions to the biblical creationist starlight-travel-time problem, November 2014, biblescienceforum.com. Return to text
- Batten, D., (Ed.), et al., How can we see distant stars in a young universe?, The Creation Answers book, ch. 5, Creation Book Publishers, Queensland, Australia, 2006. Return to text
- Cho, A., Gravitational waves, Einstein’s ripples in spacetime, spotted for first time, Science, sciencemag.com, accessed February 2016. Return to text | 0.834561 | 3.023817 |
Every year, astronomers discover many new exoplanets. Some of these distant worlds are covered in ice, while others are in the habitable zone. It is possible that some of the Earth-like planets have lives. However, there are other "hellish" worlds – on such exoplanets the temperature can reach the highest possible level. Recently, researchers discovered a planet that should not exist at a distance of 1060 light years from Earth – the gas giant NGTS-10b. This is the "hot Jupiter" that turns so close to the star that it makes a complete revolution around it in 18.4 hours. Not surprisingly, this exoplanet is of great interest to scientists. The researchers shared their findings in an article published in the Royal Astronomical Society's Monthly Notices.
Why are hot Jupiters interested in scientists?
Hot Jupiters are amazing exoplanets. The same gas giants as the worlds in our solar system, these objects move very close to their suns. The rotation time of hot Jupiter around the host stars is usually less than 10 days. According to modern models of planet formation, such Jupiter should not exist. The fact is that the gas giant cannot form as close to its star because gravity, radiation, and intense stellar wind must prevent the gas from sticking together. Even so, out of the more than 4,000 confirmed exoplanets discovered to date, up to 337 can be hot Jupiters.
Researchers believe that these gas giants form in their planetary systems and then move closer to the star. Today we may not know much about how they are born, but hot Jupiter, who are particularly close to their stars, can tell a lot about the interplay of stars and planets. Therefore, these objects are among the least studied exoplanets in the galaxy. In the past, only six hot gas giants with less than a day's orbit were discovered.
Between September 21, 2015 and May 14, 2016, the researchers observed the NGTS-10 star for 237 nights. A detailed examination of the images then showed that the star fades slightly every 18.4 hours. The problem was that the light from neighboring stars made it difficult to calculate the exact distance to NGTS-10. Therefore, the distance of 1060 light years was calculated based on Gaia, the most accurate three-dimensional map of today's Milky Way. However, the error persists. If the distance is not determined correctly, this may indicate that some size and weight data are also incorrect. This problem can be solved by examining the following publication of Gaia data.
Search our Yandex.Zen channel for even more fascinating articles about distant worlds in our galaxy
Why is hot Jupiter doomed to fail?
Ongoing observations of the unusual solar system can reveal the decay of the orbit of the exoplanet. Researchers believe the orbit will decrease by 7 seconds in the next 10 years. If astronomers can get sufficiently accurate measurements of the system, they can see exactly how this happens. | 0.915312 | 3.830456 |
An international team of scientists has found a way to restore the birthplaces of stars in the Milky Way. This is one of the main goals in the field of galactic archeology, which studies the history of the formation of our galaxy.
It is known that stars in galactic disks wander from the original places of birth due to the phenomenon of “radial migration”. This movement through the galaxy greatly complicates conclusions regarding the history of the formation of the Milky Way. Radial migration depends on a number of parameters, such as the size and speed of the galactic bar, the number and shape of the spiral arms, and the frequency of smaller galaxies, merging with ours over the last 10 billion years.
Left: a sample with 600 stars located extremely close to the Sun. Right: the use of accurate values of the stellar age and iron content help to accurately restore the places of star birth. It turned out that the older stars come mainly from the inner parts of the disk (bright spots), and the young (dark) appear closer to the current position from the galactic center
To circumvent these obstacles, the researchers came up with a way to restore the history of galactic migration, using the age and chemical composition of stars as “archaeological artifacts”. They applied the generally accepted fact that star formation in the galactic disk gradually progresses outward, following the fact that the stars born in this location are endowed with a distinct picture of chemical abundance at a certain point in time. So, if age and chemical composition can be measured accurately, then it will be possible to directly derive the original location in the galactic disk without additional modeling. The team used a sample of 600 stars in the solar surroundings observed by the HARPS spectrograph on the 3.6-meter telescope at La Silla Observatory (Chile). Thanks to accurate measurements of abundance and iron, it was possible to establish that these stars appear throughout the galactic disk, and the more ancient ones are more from the central parts.
Scientists can now use this method to calculate their birthplaces, even for stars outside the original sample. For example, knowing the age of the Sun (4.6 billion years) and the iron content can be assumed that it appeared in 2000 light years closer to the galactic center than it is now. | 0.832356 | 3.617229 |
The Met Office, the UK’s weather forecasting service, will begin to provide space weather forecasts for Earth, and weather forecasts for exoplanets. Presumably this is to ensure that when we set out on an interstellar journey to a planet orbiting Proxima Centauri, we want to make sure that it isn’t raining when we land. Just kidding.
The “space weather” forecasts are basically an upwards extension to the thermosphere, a region of atmosphere about 90-600 kilometers (55-370 miles) above Earth, immediately above the mesosphere (which weather forecasts already take into account), and below the exosphere. The International Space Station, with a low earth orbit of around 350km, resides in the thermosphere. The general idea is to measure space weather in the thermosphere so that we have a better idea of the electromagnetic interference that will eventually hit the Earth. As you might’ve read recently, the Sun is currently producing a huge solar flare that threatens to disrupt computers and communications satellites — by extending its weather model to the thermosphere, the Met Office hopes to predict and mitigate the damage from similar occurrences in the future.
The forecasting of exoplanet weather is another thing entirely. Basically, a planet’s weather heavily depends on the star that it orbits — and so unsurprisingly the weather on planets in other solar systems can be very different from our own. “Most of the hundreds of extra-solar planets discovered to date are gas giants orbiting very close to their host star. These planets are strongly irradiated by the parent star, with one side experiencing permanent day and the other in permanent night,” says David Acreman, one of the astrophysicists working on the project. “The day side of the planet is much hotter than the night side and this temperature difference causes high speed winds to flow. These winds can be as fast as a few kilometers per second.”
As for why we’re attempting to forecast exoplanet weather, it’s all about science. These planets might have kilometer-per-second winds, but they’re still governed by the same physical laws on Earth. By analyzing the winds and temperature shifts, we can derive a better model of what the planets are actually like beneath the atmosphere. When it comes to studying Earth-like exoplanets that we might eventually visit, studying their weather might tell us if the planet is habitable, or indeed if there’s already signs of alien life. There’s a video of Acreman explaining exoplanet forecasting embedded below.
Both of these forecasting types will be built into the Unified Model, a weather and climate model developed by the Met Office, and used by forecasting agencies around the world. The Met Office, which was founded in 1854, is somewhat famous for being one of the first weather agencies, and one of the lynchpins of the British Empire. The development of a worldwide network of submarine cables and the electric telegraph meant that weather signals and warnings could be easily collated from and distributed to most of the world. The Met Office was also one of the first users of digital computers, and then later supercomputers. | 0.840605 | 3.900182 |
In the past 20 years, gamma-ray astronomy has opened a new window to the most violent processes in the Universe. At energies more than 10 orders of magnitude larger than visible light, the sky appears completely different from what we see with naked eye. The gamma-rays at these energies are produced in the interactions of cosmic rays, particles that are known to exist since the beginning of the 20th century. Yet, we still don't know where they come from and how they reach Earth, and we are just at the beginning of understanding the role that cosmic rays play in various astrophysical processes.
We participate in two experiments that measure gamma-rays at very high energies, namely the High Energy Stereoscopic System (H.E.S.S.), which is taking data since 2002, and the next generation observatory Cherenkov Telescope Array (CTA), which is currently in the construction phase. | 0.863796 | 3.637729 |
The mysterious yellow skies of WASP-79b
Earth is beautiful, and we might sometimes take it for granted that we can look up and see a deep blue sky. But what about other planets? A planet’s particular sky depends, of course, on its unique atmosphere. For example, we here on Earth have a blue sky because the blue component of our sun’s light is scattered in all directions by air molecules in Earth’s atmosphere. Mars, on the other hand, has a more pinkish sky due to ever-present dust lofted from Mars surface by winds. Now, scientists have announced results of a study of a distant exoplanet, orbiting a star hotter and brighter than our sun. This planet – called WASP-79b – doesn’t have a blue or pink sky, but instead a yellow one!
The finding was made by researchers combining data from the Hubble Space Telescope, the Transiting Exoplanet Survey Satellite (TESS) and the ground-based Magellan telescopes at the Las Campanas Observatory in Chile.
WASP-79b is a large gas giant planet of the type known as a hot Jupiter, which orbits very close to its star and completes an orbit in only 3 1/2 days. Its star, WASP-79, is about 780 light-years away in the constellation Eridanus the River.
Scientists had expected that the planet would experience Rayleigh scattering, where certain colors of light are dispersed by very fine dust particles in the upper atmosphere. This is what makes Earth’s skies blue, since shorter (bluer) wavelengths of sunlight are dispersed.
But that is not what the researchers found. The lack of Rayleigh scattering is unexpected and “weird” according to the scientists involved. It may be evidence for currently unknown atmospheric process on the planet. As a result, the planet’s skies are probably yellow in color. The researchers also found that the planet’s atmosphere is a humid and sizzling 3,000 degrees Fahrenheit (1,648 degrees Celsius). Hot! There might be molten iron rain coming down from its scattered manganese sulfide or silicate clouds.
WASP-79b is definitely a world very unlike Earth and not a place you would want to go to for a vacation. As lead study author Kristin Showalter Sotzen of the Johns Hopkins University Applied Physics Laboratory (JHUAPL) said in a statement:
This is a strong indication of an unknown atmospheric process that we’re just not accounting for in our physical models. I’ve shown the WASP-79b spectrum to a number of colleagues, and their consensus is ‘that’s weird.’
Because this is the first time we’ve see this, we’re really not sure what the cause is. We need to keep an eye out for other planets like this because it could be indicative of unknown atmospheric processes that we don’t currently understand. Because we only have one planet as an example we don’t know if it’s an atmospheric phenomenon linked to the evolution of the planet.
So how did the researchers determine the color of WASP-79b’s sky?
They did it by using a spectrograph on the Magellan telescopes. Spectrographs analyze the different wavelengths of light, and by doing so, in this case, can find clues as to the chemical composition of the exoplanet’s atmosphere. It was anticipated that the atmosphere of WASP-79b would have Rayleigh scattering like in Earth’s atmosphere, resulting in a blue sky. But – surprise – they found the opposite instead. There was less absorption and scattering in the atmosphere, meaning that the planet probably has a yellow sky instead of blue. The findings by the Magellan telescopes were also confirmed by TESS.
WASP-79 is now one of the largest stars known to have a planet, which makes this study even more interesting. So far, most exoplanets have been discovered orbiting red dwarfs, the most common stars in the galaxy, or around stars similar to our sun.
WASP-79b is huge, about 1.7 times the radius of Jupiter. Its deep, extended atmosphere, due to it being so hot, makes it an ideal exoplanet for study by the telescopes used in this study. It’s also interesting in other ways as well.
Previous studies of the planet by Hubble showed that it has water vapor in its atmosphere. This isn’t really too surprising in itself, despite the heat, but the finding may also help scientists better understand just what is going on in WASP-79b’s exotic atmosphere.
The newest unusual results will keep scientists busy, and should help shed light on how hot Jupiters and other giant planets form and evolve. In another press release from JHUAPL, Sotzen said:
We’re really not sure what’s going on here. But if similar features are found on other such worlds, it’s going to provoke questions about current theories on atmospheric processes and evolution. We’re trying to look at a lot of different hot Jupiters because they’re easier to analyze. What we learn from them will help us make predictions about the atmospheres of other exoplanets, like whether they have clouds or not.
Kathleen Mandt, a planetary scientist at JHUAPL, also said:
In our own solar system, we don’t know how much solid material contributed to the formation of the giant planets, how quickly they formed and by what processes, and even more importantly how they migrated after forming. As we obtain new results about exoplanets like WASP-79b, we’re collecting critical information about the formation of giant planets around other stars to better understand fundamental processes of planet formation and evolution.
The upcoming James Webb Space Telescope – tentatively scheduled to launch in 2021 – will be able to take an even better look at WASP-79b and analyze its chemical composition in more detail. This might help solve the mysteries of this intriguing, yellow-hued world.
Bottom line: Using three different telescopes, scientists have found that a huge, hot exoplanet has yellow skies instead of blue. | 0.889291 | 3.831158 |
A coronal mass ejection, or CME, is a burst of solar winds, plasma and magnetic fields released into space. CMEs are sometimes associated with solar flares and other activity. If a CME reaches Earth, it's referred to as an interplanetary CME. On Earth, such activity can interrupt radio communications and damage satellites and electrical transmission lines.
CMEs reaching Earth can also produce strong auroras around Earth's magnetic poles, known as the Northern and Southern Lights.
Read more on coronal mass ejections.
The largest type of black hole in a galaxy, believed to exist at the center of most if not all galaxies, including the Milky Way.
When a spacecraft as complex as the space shuttle lifts off, it takes an immense amount of precise coordination between those in launch control in Florida, mission control in Houston, and of course the astronauts in the space shuttle. All of this communication happens via radio traffic, and for those watching, can sound like a well-rehearsed jargon-filled diatribe.
Astronaut Douglas Wheelock took to twitter this morning to share a little insight on what some of it means to those who will be watching and listening to NASA's final space shuttle launch. FULL POST
NASA stands for the National Aeronautics and Space Administration, and is the American governmental agency responsible for civilian spaceflight, as well as aeronautics and aerospace research.
The agency was established on July 29, 1958 by the National Aeronautics and Space Act and has since established and supported such programs as Mercury, Gemini, Apollo and the Space Shuttle.
The ET, or external tank, is the large orange tank mounted on the belly of the space shuttle's orbiter. It is filled with liquid hydrogen fuel and liquid oxygen oxidizer ahead of launch, and feeds both substances to the space shuttle's main engines during launch.
The process of raising the orbit of a satellite or spacecraft. Because certain craft are in low-Earth orbit, they experience some atmospheric drag which decays the orbit. The International Space Station, for example, is periodically reboosted to prevent it from falling to Earth.
A vertical strip of metal, 108 of which surround the Shuttle's external tank and provide structural support.
A lightyear, as defined by the International Astronomical Union, is the distance that light travels in a vacuum in one Julian year. It is equal to roughly 10 trillion kilometers (about 6 trillion miles). A lightyear is one unit used to measure distances on a galactic scale.
MECO is main-engine cutoff, the point at which a space craft's main engines stop firing. For the space shuttle, MECO occurs about 8 minutes after liftoff and indicates that the shuttle has reached orbit. | 0.868436 | 3.234303 |
The solar system no longer has nine planets
February 8, 2006 Since 1930 when American Clyde Tombaugh discovered Pluto, schoolchildren have been taught that Planet Earth is one of nine planets which orbit the sun, and that Pluto is the outermost planet in the solar system. Then last July 30, an American team found a more distant and quite large object circling the sun some 15 billion kilometers beyond earth. Dubbed UB313, an enormous debate has erupted over whether it should be classified as the tenth planet. More fuel was added to the debate last week when a group lead by Bonn astrophysicists determined that this putative planet is bigger than Pluto. By measuring its thermal emission, the scientists were able to determine a diameter of about 3000 km, which makes it 700 km larger than Pluto and thereby marks it as the largest solar system object found since the discovery of Neptune in 1846. For the last six months, many astronomers have argued that UB313 should be classified as a Kuiper belt object (KBO) but Pluto is also in the Kuiper belt, and the revelations about its size will weigh heavily when the special 19-member panel set up by the International Astronomical Union (IAU) determines exactly what constitutes a planet. Either way, the official planetary count will no longer be nine.
Like Pluto, 2003 UB313 is one of the icy bodies in the so-called Kuiper belt that swarms beyond Neptune. It is the most distant object ever seen in the Solar System. Its very elongated orbit takes it up to 97 times farther from the Sun than is the Earth - almost twice as far as the most distant point of Pluto's orbit – so that it takes twice as long as Pluto to go around the Sun.
When it was first seen, UB313 appeared to be at least as big as Pluto, but an accurate estimate of its size was not possible without knowing how reflective it was. A team lead by Prof. Frank Bertoldi from the University of Bonn and the Max-Planck-Institute for Radioastronomy (MPIfR) and the MPIfR's Dr. Wilhelm Altenhoff has now resolved this problem by using measurements of the amount of heat UB313 radiates to determine its size, which when combined with the optical observations also allows them to determine its reflectivity. "Since UB313 is decidedly larger than Pluto," Frank Bertoldi remarks, "it is now increasingly hard to justify calling Pluto a planet if UB313 is not also given this status."
UB313 was discovered in January 2005 by Prof. Mike Brown and his colleagues from the Californian Institute of Technology in a sky survey using a wide field digital camera that searches for distant minor planets at visible wavelengths. They discovered a slowly moving, spatially unresolved source, the apparent speed of which allowed them to determine its distance and orbital shape. However, they were not able to determine the size of the object, although from its optical brightness it was believed to be larger than Pluto.
Astronomers have found small planetary object beyond the orbits of Neptune and Pluto since 1992, confirming a then 40-year old prediction by astronomers Kenneth Edgeworth (1880-1972) and Gerard P. Kuiper (1905-1973) for the existence of a belt of smaller planetary objects beyond Neptune. The so-called Kuiper Belt contains objects left from the formation of our planetary system some 4.5 billion years ago. In their distant orbits they were able to survive the gravitational clean-up of similar objects by the large planets in the inner solar system. Some Kuiper Belt objects are still occasionally deflected to then enter the inner solar system and may appear as short period comets.
In optically visible light, the solar system objects are visible through the light they reflect from the Sun. Thereby the apparent brightness depends on their size as well as on the surface reflectivity. Latter is known to vary between 4% for most comets to over 50% for Pluto, which makes any accurate size determination from the optical light alone impossible.
The Bonn group therefore used the IRAM 30-meter telescope in Spain, equipped with the sensitive Max-Planck Millimeter Bolometer (MAMBO) detector developed and built at the MPIfR, to measure the heat radiation of UB313 at a wavelength of 1.2 mm, where reflected sunlight is negligible and the object brightness only depends on the surface temperature and the object size. The temperature can be well estimated from the distance to the sun, and thus the observed 1.2 mm brightness allows a good size measurement. One can further conclude that the UB313 surface is such that it reflects about 60% of the incident solar light, which is very similar to the reflectivity of Pluto.
"The discovery of a solar system object larger than Pluto is very exciting," Dr. Altenhoff exclaims, who has researched minor planets and comets for decades. "It tells us that Pluto, who should properly also be counted to the Kuiper Belt, is not such an unusual object. Maybe we can find even other small planets out there, which could teach us more about how the solar system formed and evolved. The Kuiper Belt objects are the debris from its formation, an archeological site containing pristine remnants of the solar nebula, from which the sun and the planets formed." Dr. Altenhoff made the pioneering discovery of heat radiation from Pluto in 1988 with a predecessor of the current detector at the IRAM 30-meter telescope.
The size measurement of 2003 UB313 is published in the 2 February 2006 issue of Nature. The research team includes Prof. Dr. Frank Bertoldi (Bonn University and MPIfR), Dr. Wilhelm Altenhoff (MPIfR), Dr. Axel Weiss (MPIfR), Prof. Dr. Karl M. Menten (MPIfR), and Dr. Clemens Thum (IRAM). | 0.873097 | 3.645717 |
“I don’t think I’m alone when I say I’d like to see more and more planets fall under the ruthless domination of our solar system.” — Deep Thoughts by Jack Handey
This series is about how planets die — it is introduced here.
Getting old sucks. Not only am I (mostly) bald but I’m becoming grumpier, dumber and more injury-prone by the day….
Just like people, stars age. Their planets go along for the ride and are often killed or maimed in the process.
Small stars and big stars age at different speeds. It’s like rock stars and farmers. Rock stars live like crazy people then die within a few years die a drug-fueled blaze of glory. Farmers just keep farming for decades and decades until they’re all farmed out. (Apologies for the generalization if you’re a farmer or rock star).
Massive stars — born with at least 8 times as much mass as the Sun — are the rock stars. They burn super bright, then quickly explode. We obsess over their remains (black holes, neutron stars). And, like rock stars, massive stars are very rare.
“Normal” stars are the farmers. They burn at an appropriate level and evolve slowly. After using up all their fuel, which typically takes a few billion years or more, they burn out. They pass on some of their experience to the next generation as they shed their outer layers, then they end up as run-of-the-mill white dwarfs.
The most common type of star are red dwarf stars. They don’t have a good analog among humans because they burn so slowly that they basically live forever. To be annoyingly precise, they don’t actually live forever, it’s just that their lifetimes are much longer than the current age of the Universe (about 14 billion years).
What happens to planets in the habitable zones of different types of stars?
I’ll chop it into three parts. Part 1 is about puny red dwarf stars. Part 2 is about stars similar to the Sun (farmers). We’ll end — with a bang! — with the massive (rock) stars in Part 3.
Part 1. Planets orbiting red dwarf stars: dehydrated and toasted
Red dwarf stars basically live forever. And they don’t change much. So, you might think that any planets orbiting them are safe…
It takes a while for red dwarfs to really become “stars”. The process of collapsing into a star and triggering nuclear fusion is slowed down by their low gravity. While stars like the Sun take perhaps ten million years to settle onto the main sequence, red dwarfs — and especially the puniest among them — can take upwards of 100 million years.
Why do we care? Because, before settling down stars are brighter. This means that the habitable zone — where a planet might have liquid water if it has the right conditions — is farther away.
Imagine an Earth-sized planet around a red dwarf star. Once the star has settled down, the planet will be in the habitable zone. But for 100 million years or more the planet is on the wrong side of the habitable zone. It is too hot.
During this too-hot phase the planet could lose all its water!
First, the planet’s atmosphere would undergo strong greenhouse heating. This would transport water up into the stratosphere, where could be broken apart (into hydrogen and oxygen) by high-energy radiation from the young star, and slowly lost to space (see planet death by climate catastrophe for more on this).
If the planet loses all of its water then, as the star settles down the planet will enter the habitable zone completely dried out. It will be in the right place for liquid water but all of its water is gone!
We don’t know whether this process dries out planets completely or just strips off a few outer layers of ocean. If a planet has enough water trapped in its interior (Earth is thought to have a few times its surface water in the mantle) then it could withstand losing its oceans by later out-gassing new ones. It’s a complex interplay between geology and astronomy and the outcome is….unknown (for now).
Part 2. Planets around Sun-like stars: roasted in a slowly-heating oven then deep-fried
Stars like the Sun evolve faster than red dwarfs. They reach the main sequence too quickly to worry about water loss early on.
But while they are on the main sequence they don’t remain perfectly constant. The Sun is slowly brightening over billions of years.
As the Sun converts hydrogen to helium in its core (via the proton-proton chain), the average density in the core increases, because atoms with just one proton are being converted into atoms with two protons. This causes a very slight increase in the local temperature, which increases the strength of fusion.
That means that life on Earth lives under a constantly-brightening Sun. Sure, the brightening is extremely slow (only about 0.00000000003% from one day to the next). But over billions of years it adds up.
Rewind the clock and we have the Faint Young Sun paradox (first pointed out by Carl Sagan and George Mullen in 1969). There is evidence for life on Earth 3-4 billion years ago (the earliest evidence is always debated, but it’s at least 3.5 billion years ago). However, most climate models calculate that the Earth should have been frozen solid under a Sun that was only 70% as bright as it is today. This paradox remains heavily debated; solutions may involve the greenhouse effect or a number of other effects.
Project forward and the future looks bleak. Earth is already close to the inner edge of the habitable zone. In a billion years the Sun will be 10% brighter and the Earth will cross over and no longer be in the habitable zone.
When that happens, Earth will become hot enough to trigger a runaway greenhouse. That means that there is a strong positive feedback that keeps making the planet hotter and hotter (this includes vaporizing the oceans). Heating increases the amount of water vapor in the atmosphere, which increases the rate of heating, and so on.
This will turn Earth into a Steamball planet, and water will eventually be lost from the stratosphere. In time Earth will likely end up a dry desert wasteland of a planet, like Venus. Frowny face…
This gradual brightening happens for all main sequence stars. If Earth were on Mars’ orbit, it would remain in the habitable zone for longer. But if Earth orbited a more massive star than the Sun then its lifetime in the habitable zone would have been shorter.
Things only get worse from there.
Stars like the Sun last about ten billion years. At 4.5 billion years old the Sun is firmly in its middle age, slowly brightening and not doing much else. But about seven billion years from now, watch out!
The Sun’s core will run out of hydrogen, its source of fuel. Fusion of hydrogen will continue in a shell and this will puff the Sun up into a red giant. Red giants are cooler than Sun-like stars (hence their redness) but are very bright because of their very large sizes. Betelgeuse, Orion’s bright right shoulder, is a good example.
The red giant Sun will grow to 100-200 times larger than its current size, about as big in size as Earth’s orbit. Venus and Mercury will be swallowed whole, and Mars and the giant planets will be pushed outward. Earth is on the cusp; it is uncertain whether it will be swallowed or pushed away.
A ray of hope is that, for a few hundred million years, Saturn will be in the habitable zone. Saturn has several large moons and its largest, Titan, is the only world apart from Earth to have liquid on its surface (although in Titan’s case it is liquid ethane and methane). Still, Titan might be a good place for life during the Sun’s red giant phase.
The Sun’s evolution (at least the interesting part) will finish with a series of explosions and the removal of its outer layers to make a pretty planetary nebula (no relation to planets, just a badly-chosen name). The core — a white dwarf — will stick around and just passively cool off for eons.
White dwarfs are almost as massive as the Sun but only about the size of Earth. This means that they have extremely strong surface gravities, and anything heavier than hydrogen or helium settles out of their atmospheres and into the stars themselves in days to months, an astronomical blink of the eye.
But many white dwarfs are found to be “polluted”. Instead of looking like pure balls of hydrogen and helium, their spectra show signatures of rocks and other elements, sometimes including water. These are signs of material that has very recently fallen onto their surfaces, probably asteroids and comets whose orbits were destabilized by the planets moving around as the Sun evolved.
What is amazing is that, because the outer layers of white dwarfs are just hydrogen and helium, we can measured the properties of these asteroids and comets with very good precision. Remember, these objects are leftovers from the formation of the planets. Being able to measure their compositions around white dwarfs whose habitable planets were destroyed is akin to analyzing the blood spatter at a crime scene.
Part 3. Planets orbiting high-mass stars: blown apart by a rock star!
Like rock stars, massive stars live fast and die young. On the main sequence they are big and hot and bright. Since they are so hot they appear blue.
But they don’t last long. Within a few million years, very massive stars evolve into supergiants. The most massive become blue supergiants and less massive ones because red supergiants. Not long afterward, they go supernova!
Massive stars are born with ten to a hundred times more mass than the Sun. Their huge luminosities are powered by vigorous nuclear fusion. This creates a whole slew of elements — everything from carbon up to iron — in a series of onion-like rings, each of which is creating something different.
Supernovae blow their stars to pieces (note: one supernova, two supernovae). They are splattered all over the place. Since stars form in clusters and massive stars die young, a large fraction of a massive star’s guts are immediately donated to the next generation of stars.
What is different about massive stars is that they are so energetic that they not only affect their own planets, but planets orbiting other stars too.
Can planets form around massive stars? None has been found (yet), but that is probably because there are so few massive stars to search and planets are hard to find. Massive stars form with massive disks around them, and there is reason to think that planets should form readily. In fact, their disks are so massive that they may often form gas giants rather than rocky planets.
Planets may form around super high-mass stars but they wouldn’t last long. Supernovae are so energetic that they would likely vaporize their planets entirely. Planets have been detected around a handful of a special type of neutron stars called pulsars (and these include the first confirmed exoplanets!).
The pulsar planets are probably not the original planets that formed around their host stars before they went supernova. Rather, pulsar planets are likely to either be a) second generation planets that formed from leftover debris, b) the remnants of original companion star, or c) planets captured from another star.
Given that massive stars have such short lifetimes, a planet orbiting one is not a great candidate for life.
Supernovae have a huge effect on their surroundings. The shock waves generated by supernovae can trigger other stars to form. Stars that are too close to a supernova can have their gaseous planet-forming disks completely evaporated. This would stunt the growth of gaseous planets like Jupiter but might not preclude the formation of rocky worlds.
Supernovae also barf their guts all over the place. There is evidence from meteorites that our Sun’s planet-forming disk was contaminated with highly radioactive material from a nearby supernova.
That radioactive material — specifically an isotope of Aluminum and one of Iron — provided a huge amount of heat in the baby Solar System. It played a central role in determining the water contents of the planets. Indeed, without any of this radioactive Aluminum and Iron, it is quite possible that Earth’s oceans would be so deep that there would be no land!
Most stars are likely to get a Sun-like dose as long as there are enough stars in their birth clusters for there to be a supernova (statistically, at least ~1000 stars). The ones that form in puny groups may have much wetter planets.
So the proximity of a growing planetary system to a supernova can affect the growth of planets. Too close and a star’s planet-forming disk is history. Too far and your system forms with much less heating than the Solar System (although we don’t know how strongly this really affects planet formation). The Solar System fell somewhere in between.
Supernovae may also harm fully-grown planets. The blast of energetic particles from supernovae can destroy an Earth-like planet’s ozone layer if it is within about 20 light years. Without an ozone layer the planet would be vulnerable to a lethal dose of ultraviolet light from its host star.
How many planets are killed by their aging stars?
Let’s break it down for each type of star. First, remember that most stars are red dwarfs (spectral type M).
How many stars dry out their planets before they even become full-fledged stars?
A lot! This could in principle affect red dwarfs less than about half the Sun’s mass. Sure, those stars live forever. But they take a long time (100 million years or more) to settle down and become real stars, and during that time any planet in the habitable zone is vulnerable.
There are a few hundred billion stars in the Galaxy — let’s say 400 billion to make the numbers simple. About three quarters are red dwarfs — that makes 300 billion. At least one third of those have an Earth-sized planet in the habitable zone. That makes 100 billion planets that may be affected by this type of water loss.
How many Sun-like stars fry their planets as they age, or kill them when they become red giants?
About ten percent of stars are Sun-like in that their main sequence lifetimes are less than the age of the Universe but they are too low-mass to go supernova. We don’t know exactly what fraction of these stars have rocky planets in their habitable zones. Let’s say ten percent.
That makes 4 billion potentially rocky worlds. Each one of those planets will slowly heat up as its Sun slowly gets brighter. And each one is doomed when its Sun turns into a red giant, perhaps to be swallowed but at least to be thoroughly roasted.
How many planets are killed or sterilized by massive stars?
Only stars more massive than about 8 solar masses will become supernovae. That is about one in every thousand stars. Even though high-mass stars don’t last long, we can use our Milky Way’s 400 billion stars as tracers. That means that about 400 million supernovae have gone off in our galaxy’s history. And it is consistent with the current rate of a couple of supernovae per century.
If any of those massive stars formed their own rocky planets they were vaporized. But since those stars go boom so fast, planets around massive stars are unlikely to host life when they are fried.
Each supernova affects nearby star systems: planets within about 20 light years are vulnerable to losing their ozone layers. However, many nearby star systems are still in the process of formation and so may not yet have developed an ozone layer. But some
The final tally: 100 billion planets are at risk of losing their water (red dwarf stars), 4 billion planets are doomed (Sun-like stars),
Let’s put these processes on our planetary death scale.
We’ll break it down by star type: blue for the rock stars, yellow for Sun-like stars, and red for red dwarfs.
Red dwarfs can dry out their planets, but it takes a while for a planet to lose water. Plus, many planets are likely to have extra oceans that remain stored in their mantles until their stars settle down. So, this process is somewhere between sterilization and extinction.
Sun-like stars sterilize their planets as they get brighter with age and often destroy them when they turn into red giants.
Finally, any planets orbiting a massive star are likely vaporized by the supernova blast. Planets around nearby stars would survive but might lose their ozone layers. This would be bad for life and may cause extinctions or, in extreme cases, sterilization. However, only a small fraction of stars are likely to suffer such a harsh fate.
Let’s use all this for a sci-fi story called A cosmic charity case…
Imagine a highly advanced civilization. Maybe advanced enough to engineer their own Solar Systems. They are master astronomers with extensive knowledge of the heavens. They have mapped out all of the planetary systems in their galactic neighborhood. They know which stars host habitable planets. They have sent messages to thousands of planets in the hopes of getting an answer from another civilization. But no luck. They’ve found signs of life in the spectra of other worlds but no one has answered their calls.
Their government has a cosmic Search and Rescue division. It is dedicated to identifying planets that are about to be destroyed or sterilized, then rescuing any creatures that live on such planets. They frequently pat themselves on the back for being so noble. The Search and Rescue division has their own Noah’s Ark, a giant spacecraft that is filled up with specimens. When it returns home, the creatures are moved to their own planet in a cosmic zoo, a planetary system with hundreds to thousands of planets teeming with life from across the galaxy. (This may remind some of you of the Rama series by Arthur C. Clarke…).
But what happens when the animals in the zoo evolve, and revolt?
- Introduction to the how planets die series
- Blog post (in poem form) about Proxima b and the effect of water loss
- Scientific article on water loss of planets orbiting red dwarfs (like Trappist-1, Proxima Cen): Bolmont et al (2017)
- Nautilus article: Reading Earth’s destiny in the blood spatter around other stars
- A nice animation of the discovery of supernova 1987A.
- Rendezvous with Rama by Arthur C. Clarke: my all-time favorite sci-fi book. | 0.928657 | 3.233274 |
Your daily selection of the latest science news!
According to Universe Today
The core of the Milky Way Galaxy has always been a source of mystery and fascination to astronomers. This is due in part to the fact that our Solar System is embedded within the disk of the Milky Way – the flattened region that extends outwards from the core. This has made seeing into the bulge at the center of our galaxy rather difficult. Nevertheless, what we’ve been able to learn over the years has proven to be immensely interesting.
For instance, in the 1970s, astronomers became aware of the Supermassive Black Hole (SMBH) at the center of our galaxy, known as Sagittarius A* (Sgr A*). In 2016, astronomers also noticed a curved filament that appeared to be extending from Sgr A*. Using a pioneering technique, a team of astronomers from the Harvard-Smithsonian Center for Astrophysics (CfA) recently produced the highest-quality images of this structure to date.
The study which details their findings, titled “A Nonthermal Radio Filament Connected to the Galactic Black Hole?“, recently appeared in The Astrophysical Journal Letters. In it, the team describes how they used the National Radio Astronomy Observatory’s (NRAO) Very Large Array to investigate the non-thermal radio filament (NTF) near Sagittarius A* – now known as the Sgr A West Filament (SgrAWF).
As Mark Morris – a professor of astronomy at the UCLA and the lead authority the study – explained in a CfA press release:
“With our improved image, we can now follow this filament much closer to the Galaxy’s central black hole, and it is now close enough to indicate to us that it must originate there. However, we still have more work to do to find out what the true nature of this filament is.”
After examining the filament, the research team came up with three possible explanations for its existence. The first is that the filament is the result of inflowing gas, which would produce a rotating, vertical tower of magnetic field as it approaches and threads Sgr A*’s event horizon. Within this tower, particles would produce radio emissions as they are accelerated and spiral in around magnetic field lines extending from the black hole.
The second possibility is that the filament is a theoretical object known as a cosmic string. These are basically long, extremely thin cosmic structures that carry mass and electric currents that are hypothesized to migrate from the centers of galaxies. In this case, the string could have been captured by Sgr A* once it came too close and a portion crossed its event horizon.
The third and final possibility is that there is no real association between the filament and Sgr A* and the positioning and direction it has shown is merely coincidental. This would imply that there are many such filaments in the Universe and this one just happened to be found near the center of our galaxy. However, the team is confident that such a coincidence is highly unlikely.
As Jun-Hui Zhao of the Harvard-Smithsonian Center for Astrophysics in Cambridge, and a co-author on the paper, said:
“Part of the thrill of science is stumbling across a mystery that is not easy to solve. While we don’t have the answer yet, the path to finding it is fascinating. This result is motivating astronomers to build next generation radio telescopes with cutting edge technology.”
All of these scenarios are currently being investigated, and each poses its own share of implications. If the first possibility is true – in which the filament is caused by particles being ejected by Sgr A* – then astronomers would be able to gleam vital information about how magnetic fields operate in such an environment. In short, it could show that near an SMBH, magnetic fields are orderly rather than chaotic.
This could be proven by examining particles farther away from Sgr A* to see if they are less energetic than those that are closer to it. The second possibility, the cosmic string theory, could be tested by conducting follow-up observations with the VLA to determine if the position of the filament is shifting and its particles are moving at a fraction of the speed of light.
If the latter should prove to be the case, it would constitute the first evidence that theoretical cosmic strings actually exists. It would also allow astronomers to conduct further tests of General Relativity, examining how gravity works under such conditions and how space-time is affected. The team also noted that, even if the filament is not physically connected to Sgr A*, the bend in the filament is still rather telling.
In short, the bend appears to be coincide with a shock wave, the kind that would be caused by an exploding star. This could mean that one of the massive stars which surrounds Sgr A* exploded in proximity to the filament in the past, producing the necessary shock wave that altered the course of the inflowing gas and its magnetic field. All of these mysteries will be the subject of follow-up surveys conducted with the VLA.
As co-author Miller Goss from the National Radio Astronomy Observatory in New Mexico (and a co-author on the study) said, “We will keep hunting until we have a solid explanation for this object. And we are aiming to next produce even better, more revealing images.”
- Got any news, tips or want to contact us directly? Email [email protected] | 0.887047 | 3.58315 |
As the bright planets Venus and Jupiter go their own separate ways after their spectacular tryst in mid-March, Venus continues to grow ever-brighter as the northern spring evenings warm up. The planet seems to gleam almost like a sequined showgirl, hovering in the west-northwest sky high above the setting sun.
Next week, Venus is will continue its celestial display when it shines near the well-known Pleiades star cluster in the western sky on Tuesday (April 3). But first, some basic facts about Venus:
Many astronomy books refer to Venus as Earth's "twin sister," since both planets have very nearly the same size and mass. In terms of diameter, Venus is about 300 miles (483 kilometers) smaller than Earth and the gravity at its surface is 85 percent that of the Earth's surface.
Of course, that's where the similarities end.
The atmosphere of Venus is very thick and far greater in density than ours. Most of Venus' atmosphere is carbon dioxide, along with surface temperatures that are extremely hot; on the order of 860 degrees Fahrenheit (460 degrees Celsius). This high temperature is caused by the trapping of radiation by the lower atmosphere of the planet — a sort of runaway greenhouse effect.
Earth's sister meets the seven sisters
While our "sister world" Venus has attracted a lot of attention from its recent displays with Jupiter and a lovely crescent moon, come Tuesday night it will have a rendezvous with another noteworthy celestial landmark, popularly known in their own right as the "Seven Sisters" or the Pleiades.
The sky map of Venus and the Pleiades with this story shows how they will appear on Tuesday.
There is nothing else like the Pleiades star cluster in the sky. Few observers can look very long at the night sky at this time of year without noticing the Pleiades stars and wondering what they really are.
The traditional Greek legend for the Seven Sisters — as this cluster has long been known — is that they are the daughters of Atlas and Pleione. Their father, Atlas, rebelled against Zeus, the king of the gods, who retaliated by sentencing him to forever holding up the heavens on his shoulders. This so grieved the sisters that Zeus placed them in the heavens so that they could be close to their father.
Peering at the Pleiades
Interestingly, widely separated and totally different cultures have always described the Pleiades as the "Seven Sisters," "Seven Maidens," or "Seven Little Girls." Yet, only six stars are readily visible to most observers.
Those with more acute eyesight may glimpse up to 12 under good conditions. But why this cluster has been cited by more than one early people as having seven members remains a mystery.
It will, however, be a bit more difficult to see them on Tuesday night, since brilliant Venus with its great brilliance will nearly overpower the star cluster.
On that night, our sister planet will pass just a half-degree (the apparent width of the moon) to the south of the Seven Sisters. The planet is 160 times brighter than the star cluster. The very best views will be with binoculars or a small telescope, with Venus glowing like a steady white diamond below and to the left of cluster; a very beautiful sight indeed!
In a telescope, Venus currently appears as a dazzling silver-white almost "half moon" phase, but in the nights to come it will gradually become a thick crescent while growing larger as it swings around its orbit closer to Earth. Watch as Venus changes it shape and size from week to week.
If you snap an amazing photo of Venus and the Pleiades, or any other skywatching target, and would like to share it for a possible story or image gallery, please contact SPACE.com managing editor Tariq Malik at [email protected].
Joe Rao serves as an instructor and guest lecturer at New York's Hayden Planetarium. He writes about astronomy for The New York Times and other publications, and he is also an on-camera meteorologist for News 12 Westchester, New York. | 0.877235 | 3.661645 |
The Sun – Unique Star
Our Sun is truly a unique star, only because its luminosity has allowed to create conditions suitable for life on our planet Earth, which is at an ideal distance from the Sun Since ancient times, the Sun was under the attention of a man. If in ancient time, priests, shamans, druids worshiped the Sun as a god (there were solar gods in all pagan cults), now the Sun is actively studied by scientists: astronomers, physicists, astrophysicists. What kind of star is the Sun? What are characteristics of the Sun? How old is the Sun? We’ll answer these questions in our article.
Where is the Sun in the Galaxy?
Despite its huge size relative to our planet (and other planets) on a galactic scale, the Sun is far from being the biggest star. The Sun is a very small star; because there are stars that are much bigger than the Sun. Therefore, astronomers attribute the Sun to the class of yellow dwarfs.
The Sun located in the Milky Way galaxy, closer to the edge of Orion’s arm. Remoteness from the center of the galaxy is 7.5-8.5 thousand parsecs. In simple terms, we are not in the center of the Galaxy, but not in its border as well.
Here is the location of the Sun on the galactic map.
Physical Characteristics of the Sun
According to the astronomical classification of celestial objects, the Sun belongs to the G-class star. The Sun is brighter than 85% of other stars in the galaxy, many of which are red dwarfs. The diameter of the Sun is 696342 km, weight – 1.988 x 1030 kg. If we compare the Sun with the Earth, then it is 109 times bigger than our planet and 333000 times more massive.
The comparative size of the Sun and other planets.
Although the Sun seems yellow to us, its true color is white. The visibility of the yellow color is created by the atmosphere.
What is the temperature of the Sun? The Sun surface temperature is 5778 degrees Kelvin (9940,73 °F), but as it gets closer to the core, it increases even more – the Sun core temperature is 15.7 million degrees Kelvin (27 million degrees Fahrenheit).
Besides this, the Sun has a strong magnetism; there are north and south magnetic poles and magnetic lines on its surface, which are reconfigured at intervals of 11 years. Intense solar emissions occur during these processes. The solar magnetic field affects the Earth’s magnetic field.
Composition of the Sun
Our Sun mainly consists of two elements: hydrogen (74.9%) and helium (23.8%). Besides them, there is: oxygen (1%), carbon (0.3%), neon (0.2%) and iron (0.2%). The Sun is divided into layers inside:
- radiation and convection zones,
- the photosphere,
- the atmosphere.
The core of the Sun has the highest density and occupies approximately 25% of the total solar volume.
The composition of the Sun.
In the solar core, nuclear energy is generated by nuclear fusion that transforms hydrogen into helium. In fact, the core is a solar motor of its own kind; thanks to it, our Sun emits heat and warms us all.
There are spots on the Sun. Sunspots are darker areas on the solar surface, and they are darker because their temperature is lower than the temperature of the surrounding photosphere of the Sun. The sunspots themselves are formed under the influence of magnetic lines and their reconfiguration.
The solar wind is a continuous stream of plasma coming from the solar atmosphere and filling the entire solar system. The solar wind is formed due to the high temperature in the solar corona, the pressure of the overlying layers cannot be balanced with the pressure in the corona itself. Therefore, there is a periodic release of solar plasma into the surrounding space.
The solar eclipse is a rare astronomical phenomenon, in which the Moon covers the Sun, completely or partially.
Schematically, a solar eclipse looks like this.
The Sun Evolution
Scientists believe that the age of the Sun is 4.57 billion years. At that time, it was created from a part of the molecular cloud represented by helium and hydrogen.
How was the Sun formed? According to one hypothesis, the helium-hydrogen molecular cloud (due to the angular momentum) started rotation and simultaneously began to heat up rapidly as the internal pressure increased. At the same time, most of the mass was concentrated in the center and turned into the Sun itself. Strong gravity and pressure led to an increase in heat and nuclear fusion, thanks to which both the Sun and other stars work.
This is the evolution of a star, including the Sun. According to this scheme, our Sun is in the phase of a small star, and the current solar age is in the middle of this phase. After 4 billion years, the Sun will turn into a red giant, further expand and destroy Mercury, Venus, and possibly our Earth. If, however, the Earth as a planet survives, then life on it will no longer be possible by that time. After 2 billion years the Sun’s glow will increase to such an extent that all terrestrial oceans simply boil away, the Earth will be burned and turned into the desert. The temperature on the Earth’s surface will be 70 °C (158 °F). Therefore, we still have about a billion years to find a new refuge for humanity in a very distant future.
But back to the Sun, becoming a red giant, it will stay in this state for about 120 million years, then the process of reducing its size and temperature will begin. When the remnants of helium in its core will be burned the Sun will lose its stability and explode, becoming a planetary nebula. The Earth at this stage (as well as the neighboring Mars) will most likely be destroyed by a solar explosion.
After another 500 million years, a white dwarf will form from the solar nebula.
Interesting Facts About the Sun
- Inside the Sun, you can put a million planets like the Earth.
- The shape of the Sun forms a nearly perfect sphere.
- 8 minutes and 20 seconds – during this time the sunbeam gets to us from its source, despite the fact that the Earth is 150 million kilometers away from the Sun.
- The word “Sun” originates from the Old English word, meaning – “South”.
- We have bad news for you; the Sun will destroy the Earth in the future. However, this will happen not earlier than in 2 billion years.
References and Further Reading
- Pitjeva, E. V.; Standish, E. M. (2009). “Proposals for the masses of the three largest asteroids, the Moon-Earth mass ratio and the Astronomical Unit”. Celestial Mechanics and Dynamical Astronomy. 103 (4): 365–372. doi:10.1007/s10569-009-9203-8. ISSN 1572-9478.
- Jump up to: a b c d e f g h i j k l m n o p q r Williams, D.R. (1 July 2013). “Sun Fact Sheet”. NASA Goddard Space Flight Center. Archived from the original on 15 July 2010. Retrieved 12 August 2013.
- Zombeck, Martin V. (1990). Handbook of Space Astronomy and Astrophysics 2nd edition. Cambridge University Press.
- Asplund, M.; Grevesse, N.; Sauval, A.J. (2006). “The new solar abundances – Part I: the observations”. Communications in Asteroseismology. 147: 76–79. Bibcode:2006CoAst.147…76A. doi:10.1553/cia147s76.
- “Eclipse 99: Frequently Asked Questions”. NASA. Archived from the original on 27 May 2010. Retrieved 24 October 2010.
Author: Pavlo Chaika, Editor-in-Chief of the journal Poznavayka
When writing this article, I tried to make it as interesting and useful as possible. I would be grateful for any feedback and constructive criticism in the form of comments to the article. You can also write your wish/question/suggestion to my mail [email protected] or to Facebook. | 0.854561 | 3.429055 |
Rush to Mars: Comet impact could make Red Planet inhabitable
The make-or-break window for this possible game-changer is October 2014. At that time, an Oort cloud comet called C/2013 A1, first discovered last month, will approach Mars, missing it by about 35,000 km, which is quite close.
However the comet’s trajectory is still uncertain, which leaves a small chance it could impact the planet, said Russian astronomer Leonid Elenin, who worked on calculating the course of the celestial body. The comet will be travelling at a speed of 56 kilometers per second relative to Mars when it passes; if they do collide, the resulting explosion would be equal to a 20,000-gigaton bomb blast – powerful enough to leave a 50-kilometer crater on the planetary surface
The event would trigger a major change of the Martian climate, Australian space scientist Robert Matson explained. The impact would evaporate large amounts of water and carbon dioxide ice from the comet, spread across a planetary scale, making the climate on Mars much warmer due to the greenhouse effect.
On the other hand, the blast would also raise huge clouds of dust and could trigger volcanic activity in the mostly-inert planet. Both would make more sunlight bounce off the Martian atmosphere, which would make the planet colder. A heating effect is likely to prevail, however.
But such dramatic change is far from certain, with more observation needed to narrow down the comet’s trajectory. Even if it is a simple close flyby, it will still be a rare chance to take high-resolution pictures of the object with the Mars Reconnaissance Orbiter mission.
The rush to Mars
Private space companies are now challenging nations not only for Low Earth Orbit deliveries but also for reaching outer space. Last week, billionaire and private space explorer Dennis Tito launched the non-commercial Inspiration Mars Foundation, which hopes to send a manned mission to flyby Mars in 2018.
The crew of the capsule could be a married couple yet to be selected, Tito announced on Wednesday, who would have to not only cope with the difficulties of a Spartan and low-gravity ship environment, but also with spending just over 500 days confined together in an enclosed space.
The mission plans to use a modified SpaceX Dragon capsule with an inflatable living module attached. It will be mostly carried by gravity on its way to Mars and back home, with little help from the rocket engines, a maneuver known as a ‘free return’ trajectory. The same approach was used for NASA’s Apollo missions to the Moon.
The Tito-funded spacecraft would pass Mars at the distance of around 160 kilometers at its closest point. The return landing on Earth would be at a record-high speed of 14.2 kilometers per second, which would require a special and highly resilient heat shield.
More traditional players in the space arena are also eyeing Mars as the next frontier. NASA and ESA have a well-established presence around and on Mars. And this week, India confirmed that it is within the timeframe to launch its Mangalyaan mission to Mars in November 2013.
Russia plans to land a rover on Mars in 2018, hopefully rehabilitating its space program after the embarrassing failure of its Phobos-Grunt survey mission. There is also collaboration between Finnish, Russian and Spanish participants on a plan to deliver several dozen landers to Mars to form a meteorological observation network on its surface. | 0.866176 | 3.256192 |
(BIVN) – Astronomers have observed the historic flyby of Comet 46P/Wirtanen using an upgraded instrument from a Mauna Kea-based telescope.
Scientists, awarded NASA telescope time at W. M. Keck Observatory, caught “sharper-than-ever data images” of this icy, rocky “Christmas comet”.
The comet hunters were led by Boncho Bonev, Physics Research Assistant Professor at American University. They completed their two-night observation of the comet as it made its long-anticipated closest approach to Earth. “It is very exciting because the comet is so close and sufficiently bright for detailed astronomical studies,” said Bonev. “Comet Wirtanen is only 30 lunar distances from our planet, meaning that it is about 30 times the distance to the moon. That is nothing compared to the vast distances astronomers typically work with.”
The researchers used the observatory’s recently upgraded Near-Infrared Spectrograph, or NIRSPEC, for the first time on a comet. The improvements were specifically completed in time for the comet’s historic flyby, the W/ M/ Keck Observatory says. Spectra of Comet Wirtanen was captured within just the first scan, marking first science for the new NIRSPEC. Video footage captured the busy scene at the Keck headquarters in Waimea during the December 16-17 observing run.
“In the two decades since we delivered NIRSPEC to Keck Observatory in 1999, the technology for digital infrared cameras has greatly improved,” said UCLA Physics and Astronomy Distinguished Professor Ian McLean, the original principal investigator who was instrumental in commissioning NIRSPEC at Keck Observatory in 1999. “So we installed more sensitive detectors, replacing the digital imaging devices, along with other mechanisms and optics, with brand new ones to give the instrument a new lease of life.”
“It’s very sensitive. The new detector will allow us to see about an order of magnitude fainter objects in the sky,” said NIRSPEC Instrument Master Greg Doppmann, an astronomer at Keck Observatory. “It has the new Hawaii 2RG Teledyne chip so it has more pixels – the pixels are smaller and they’re much more sensitive – which means much more improvement in the results we get when we operate NIRSPEC on the telescope.”
“We’re excited about the NIRSPEC upgrade,” said Keck Observatory Chief Scientist John O’Meara. “It’s going to produce amazing gains in efficiency. You can look at many more objects or get better data for the same amount of time on the sky. It’s like doubling the gas mileage on your car.”
Bonev’s team is looking for prebiotic molecules, such as water, ammonia, hydrocarbons, and other organic compounds that are said to be the “precursor ingredients to forming life.” | 0.832474 | 3.471578 |
Astronomers discover precise location of cosmic radio waves
In the 12 years since the radio bursts were first discovered, a global hunt has netted 85 of these bursts
- Published 30.06.19, 3:45 PM
- Updated 30.06.19, 4:26 PM
- a min read
In a first, Australian scientists have determined the precise location of a powerful one-off burst of cosmic radio waves.
The discovery was made with Australian Square Kilometre Array Pathfinder (ASKAP) radio telescope of the Commonwealth Scientific and Industrial Research Organisation.
A team of researchers made a high-resolution map showing that the burst originated in the outskirts of a Milky Way-sized galaxy about 3.6 billion light-years away.
"This is the big breakthrough that the field has been waiting for since astronomers discovered fast radio bursts in 2007,” said Dr Keith Bannister, lead author of the study, which was published in the journal Science.
In the 12 years since the radio bursts were first discovered, a global hunt has netted 85 of these bursts. Most have been 'one-offs' but a small fraction are 'repeaters' that recur in the same location.
In 2017, the researchers found a repeater's home galaxy but localising a one-off burst was much more challenging.
Bannister's team developed new technology to freeze and save ASKAP data less than a second after a burst arrives at the telescope.
"From these tiny time differences - just a fraction of a billionth of a second - we identified the burst's home galaxy and even its exact starting point, 13,000 light-years out from the galaxy's centre in the galactic suburbs,” said team member Dr Adam Deller of Swinburne University of Technology in Australia.
"The burst we localised and its host galaxy look nothing like the 'repeater' and its host. It comes from a massive galaxy that is forming relatively few stars. This suggests that fast radio bursts can be produced in a variety of environments, or that the seemingly one-off bursts detected so far by ASKAP are generated by a different mechanism to the repeater,” he added. | 0.83263 | 3.502393 |
So, did last night’s Full Wolf Moon seem a bit tinier than usual? It was no illusion, as avid readers of Universe Today know. As we wrote earlier this week, last night’s Full Moon was the most distant for 2014, occurring just a little under three hours after apogee.
Sure, the Moon reaches apogee every lunation, at a distance nearly as far. In fact, the Moon at apogee can be as far as 406,700 kilometres distant, and last night’s apogee, at 406,536 kilometres, is only the second farthest for 2014. The most distant apogee for 2014 falls on July 28th at 3:28 Universal Time (UT) at just 32 kilometres farther away from our fair planet at 406,568 kilometres distant.
What made last night’s MiniMoon special was its close proximity in time to the instant of Full phase. The July 2014 apogee, for example, will occur just a day and four hours from New phase.
Of course, it isn’t the Moon that’s doing the shrinking, though you’d be surprised the stuff we’ve seen around ye ole Web even on reputable news sites over the past week. The variation of the apparent size of the Full Moon does make for an interesting study in perception. The Moon varies in size from apogee to perigee from about 29.3’ across to 34.1’. This is variation amounts to 14% in apparent diameter.
Here’s an interesting challenge that you can do for a one year period, requiring just a working set of eyes: observe the Full Moon for 12 successive lunations. Can you judge which one was the “SuperMoon” and which one was the “MiniMoon” without prior knowledge?
And as you can see, we also got plenty of pictures here at Universe Today from readers of the Mini-Moon from worldwide.
The rare occurrence of an “Extreme-MiniMoon” — or do you say “Ultra?” — also sparked a lively discussion about the motion of the Moon, how rare this event is, and when it was last and will next be surpassed. A fun online tool to play with is Fourmilab’s Lunar Apogee and Perigee Calculator. Keep in mind, the motion of the Moon is complex, and accuracy for most planetarium programs tends to subside a bit as you look back or forward in time. The distances used in Fourmilab’s calculations are also geocentric, accounting for the center-to-center distance of the Earth-Moon system.
Suffice to say, this year’s Full MiniMoon was the most distant for several decades before 2014 or after.
Anthony Cook of the Griffith Observatory notes that JPL’s Horizons web interface gives a max distance for the Moon of 406,533 kilometres at 1:35 UT earlier today, 3 hours and 19 minutes prior to Full.
The next closest spread of apogee versus perigee occurs on November 18th, 1994 at 1 hour and 51 minutes apart, and 2014’s Mini-Moon won’t be surpassed in this regard until May 13th, 2052. Looking at the distances for the Moon on these dates using Starry Night, however, we get an slightly closer occurrence of 406,345 kilometres for 1994 and 406,246 kilometres for 2052.
And to top it off, the 1994 Mini-Moon was during a partial penumbral eclipse as well… we’ll leave that as a homework assignment for the astute readers of Universe Today to calculate how often THAT occurs. It should be fairly frequent over the span of a century, as the Moon has to be at Full phase for a total lunar eclipse to occur.
Looking over a larger span of time, @blobrana notes on Twitter that closer occurrences of apogee versus Full Moon with the same approximate circumstances as 2014 also occurred on October 29th 817 AD (with a 1 hour and 38 minute difference) and won’t occur again until December 20th, 2154. If research can prove or disprove that these events were even more distant, then the 2014 Extreme MiniMoon was a millennial rarity indeed…
Perhaps this won’t be the last we’ve heard on the subject! | 0.815541 | 3.447766 |
Zeroing in on Hubble's constant
(PhysOrg.com) -- In the early part of the 20th Century, Carnegie astronomer Edwin Hubble discovered that the universe is expanding. The rate of expansion is known as the Hubble constant. Its precise value has been hotly debated for all of the 80 intervening years. The value of the Hubble constant is a key ingredient in determining the age and size of the universe.
In 2001, as part of the Hubble Space Telescope Key Project, a team of astronomers led by Carnegie's Wendy Freedman determined precision distances to individual far-off galaxies and used them to determine that the universe is expanding at the rate of 72 kilometers per second per megaparsec. While the debate had previously raged over a factor-of-two uncertainty in the Hubble constant, Freedman and her team cut that uncertainty down to just 10%. And now that number is about to be decreased to 3% with the new Carnegie Hubble Program (CHP) using NASA's space-based Spitzer telescope. Freedman, who is director of the Observatories of the Carnegie Institution, will lead the effort, which includes Carnegie staff members Barry Madore and Eric Persson, and Carnegie Spitzer Fellow, Jane Rigby.
The Carnegie Hubble proposal was just selected by the Spitzer Science Center on behalf of NASA as a Cycle-6 Exploration Science Program using Spitzer. This space telescope currently takes images and spectra—chemical fingerprints—of objects by detecting their heat, or infrared (IR) energy, between wavelengths of 3 and 180 microns (a micron equals one-millionth of a meter). Most infrared radiation is blocked by the Earth's atmosphere and thus it has to be detected from space.
The Hubble Key Project observed distant objects primarily at optical wavelengths. In its post-cryogenic phase beginning in April 2009 Spitzer will have exhausted its liquid helium coolant but it will still be able to operate two of its imaging detectors that are sensitive to the near-infrared. This portion of the electromagnetic spectrum has numerous advantages, especially when observing Cepheid variable stars, the so-called "standard candles" that are used to determine distances to distant galaxies.
"The power of Spitzer," explained Freedman, "is that it will allow us to virtually eliminate the dimming and obscuring effects of dust. It offers us the ability to make the most precise measurements of Cepheid distances that have ever been made, and to bring the uncertainty in the Hubble constant down to the few percent level."
Cepheids are extremely bright, pulsating stars. Their pulsation periods are directly related to their intrinsic luminosities. So, by measuring their periods and apparent brightnesses their individual distances and therefore the distance to their parent galaxies can be determined. By considering the rate at which more distant galaxies are measured to be moving faster away from us in the universe we can calculate the Hubble constant and from that determine the size and the age of the universe.
One of the largest uncertainties plaguing past measurements of the Hubble constant involved the distance to the Large Magellanic Cloud (LMC), a relatively nearby galaxy, orbiting the Milky Way. Freedman and colleagues will begin their 700 hours of observations refining the distance to the LMC using Cepheids newly calibrated based on new Spitzer observations of similar stars in our own Milky Way. They will then measure Cepheid distances to all of the nearest galaxies previously observed from the ground over the past century and by the Key Project, acquiring distances to galaxies in our Local Group and beyond. The Local Group, our galactic neighborhood, is comprised of some 40 galaxies. The team will be able to correct for lingering uncertainties again by observing in the near-IR. Systematic errors such as whether chemical composition differences among Cepheids might affect the period-luminosity relation, will be examined using the infrared data. Spitzer will begin to execute the Carnegie Hubble Program in June 2009 and continue for at least the next two years.
"In the age of precision cosmology one of the key factors in securing the fundamental numbers that describe the time evolution and make-up of our universe is the Hubble constant. Ten percent is simply not good enough. Cosmologists need to know the expansion rate of the universe to as high a precision and as great an accuracy as we can deliver," remarked Carnegie co-investigator, Barry Madore.
Provided by Carnegie Institution | 0.812017 | 3.817655 |
The new findings are an independent line of evidence that hydrothermal activity is taking place in the subsurface ocean of Enceladus. Earlier results, published in March 2015, indicated hot water is interacting with rock beneath the sea of this distant moon. The new discoveries support that conclusion and add that the rock appears to be reacting chemically to produce the hydrogen.
The discovery of Makemake's little moon increases the parallels between Pluto and Makemake. This is because both of the small icy worlds are already known to be well-coated in a frozen shell of methane. Furthermore, additional observations of the little moon will readily reveal the density of Makemake--an important result that will indicate if the bulk compositions of Pluto and Makemake are similar. "This new discovery opens a new chapter in comparative planetology in the outer Solar System," Dr. Marc Buie commented in the April 26, 2016 Hubble Press Release. Dr. Buie, the team leader, is also of the Southwest Research Institute.
Therefore, the results of the new study support the idea that primitive life could potentially have evolved on Ganymede. This is because places where water and rock interact are important for the development of life. For example, some theories suggest that life arose on our planet within hot, bubbling seafloor vents. Before the new study, Ganymede's rocky seafloor was believed to be coated with ice--not liquid. This would have presented a problem for the evolution of living tidbits. The "Dagwood sandwich" findings, however, indicate something else entirely--the first layer on top of Ganymede's rocky core might be made up of precious, life-sustaining salty water. | 0.800997 | 3.36097 |
The Pluto – Charon system is, as I’ve reported through various Space Sunday reports, turning out to be far more remarkable a place than scientists ever imagined. While NASA’s New Horizons space vehicle, which zapped past both Pluto and Charon during its closest approach to both on July 14th, 2015.
On February 18th, NASA revealed the most recent surprise to be revealed by New Horizons: Charon may have once had a subsurface ocean that has long since frozen and expanded, pushing outward and causing the moon’s surface to stretch and fracture on a massive scale.
The side of Charon imaged by NASA’s probe is characterised by a system of “pull apart” tectonic faults, which are expressed as ridges, scarps and valleys—the latter sometimes reaching more than 6.5 kilometres (4 miles) deep. Charon’s tectonic landscape shows that, somehow, the moon expanded in its past, fracturing as it stretched.
The outer layer of Charon is primarily water ice. This layer was kept warm when the tiny world / moon was young by heat provided through the decay of radioactive elements, as well as Charon’s own internal heat of formation. Scientists say Charon could have been warm enough to cause the water ice to melt deep down, creating a subsurface ocean. However, as it cooled over time, this ocean would have frozen and expanded (as happens when water freezes), lifting the outermost layers of the moon and producing the massive chasms we see today.
In an image gathered by the Long-Range Reconnaissance Imager (LORRI) in July 2015 and release by NASA on February 18th, reveals a vast equatorial belt of chasms on Charon. This network is around 1,800 km (1,100 mi) long and in places is 7.5 km (4.5 mi) deep. By comparison, the Grand Canyon is 446 km (277 mi) long and around 1.6 km (1 mile) deep.
The inset images on the picture show one section of the network of chasms, informally named “Serenity Chasma”, with a matching colour-coded topography map. Measurements of “Serenity Chasma” strongly suggest Charon’s water ice layer may have been at least partially liquid in its early history, and has since refrozen.
Virgin Galactic, Sir Richard Branson’s private venture company which is aiming to become the world’s first commercial space line, offering fare-paying passengers sub-orbital flights into space. rolled out it new SpaceshipTwo vehicle on Friday February 19th.
The event came more than a year after the loss of the first SpaceShipTwo craft, the VSS Enterprise, in a tragic accident in which the craft broke up in mid-air on October 31st, 2014, killing co-pilot Michael Alsbury, and seriously injuring pilot Peter Siebold. At the time of the accident, several other figures involved in private sector space efforts were quick to point to Virgin Galactic’s use of nitrous-oxide as a vehicle propellant and to suggest corner-cutting by the company as causes of the accident.
However, after investigating the incident, the US National Safety Transportation Board (NTSB) drew the conclusion that the incident was largely the result of pilot error: the “feathering” mechanism designed to be used at the edge of space to allow the vehicle to gently re-enter the denser layers of Earth’s atmosphere was inadvertently deployed by co-pilot Alsbury, resulting in the immediate aerodynamic destabilisation and break-up of the vehicle. As a result of these findings, and as a part of a series of improvements made to the vehicle, the new SpaceShipTwo includes a locking mechanism designed to prevent the feathering system being deployed in error.
The new vehicle, christened VSS Unity by Professional Stephen Hawking (assisted by Branson’s year-old granddaughter), was rolled-out at a special media event held at Virgin Galactic’s operations and flight facilities in the Mojave Desert, California. It marks the start of a long programme to get the vehicle to a point where it is ready to undertake its first powered flight.
This programme will include a series of ground tests of various vehicle systems, followed by taxi tests on the runway at the Mojave Air and Space Port. after these will come “captive carry” flights, where SpaceShipTwo remains attached to its WhiteKnightTwo carrier aircraft, then unpowered glide flights before the first in a series of powered test flights. While this test programme is not expected to be as protracted as the flight evaluation programme undertaken by VSS Enterprise prior to its crash, iy does mean that the company is not ready to provide any suggested dates by which fare-paying flights might commence.
Hubble Telescope Directly Measures Rotation of ‘Super-Jupiter’
Astronomers using the Hubble Space Telescope have measured the rotation rate of an extreme exoplanet, called 2M1207b, by observing the varied brightness in its atmosphere. The calculations mark the first time the rotation of an exoplanet has been made by means of direct imaging.
2M1207b lies 170 light years from Earth and orbits a brown dwarf , designated 2M1207, at a distance of approximately 8 billion km (5 billion mi). To put this in context, this is almost half as far again as Pluto’s average distance from the Sun. Both the planet and the star it orbits are curiosities, holding considerable interest for scientists and astronomers.
As a brown dwarf star, 2M1207 falls into a category of stellar bodies which sits between the heaviest gas giant planets and the “lightest” (by mass) of what might be called “true” stars. Their mass is such that they are too small to sustain hydrogen-1 fusion reactions in their cores (like the Sun), and are thought to fuse deuterium and lithium instead.
Hubble’s imaging measurements reveal 2M1207b, which is only slightly larger than Jupiter but has 4 times its mass, is rotating about its axis once every 10 hours – more-or-less the same as Jupiter’s own spin. However, this isn’t the thing which has caught the attention of scientists.
2M1207b is a very young planet, only around 10 million years old (compare that to Earth’s 4.5 billion years!), and is still contracting under its own gravity, generating heat (like Jupiter and Saturn, 2M1207b radiates far more heat than it absorbs from its parent star). Scientists believe this heat is sufficient to form “rain” clouds in the planet’s upper atmosphere made of glass-like particles, and that lower down in the atmosphere the heat and pressure combine to form iron droplets which also fall as “rain” prior to being evaporated as the heat and pressure build.
The other point of interest with 2M1207b is its size relative to the star it is orbiting. Within the solar system, all of the planets are made up of matter from the accretion disk – the stuff left over after the Sun was born. As such, their combined mass is just a tiny fraction of the Sun’s. However, 2M1207b is just 6 times less massive than the start it is orbiting, leading scientists to believe planet and star formed independently of one another, from separate clouds of dust.
All of this makes 2M1207 and its giant planet prime targets for study by the James Web telescope, due to be launched in 2018.
Have Your Art Sent to an Asteroid
NASA is calling all space enthusiasts to send their artistic endeavours on a mission to a near-Earth asteroid.
Slated for a September 2015 launch, the Spectral Interpretation, Resource Identification, Security-Regolith Explorer (OSIRIS-REx) is designed to rendezvous with the asteroid, gather between 60 grams and 2 kg (2.1 ounces and 4.4 lbs) of materials and return it to Earth for study.
As a part of the mission, the #WeTheExplorers campaign invites the public to take part in this mission by expressing, through art, how the mission’s spirit of exploration is reflected in their own lives. Submitted works of art will be saved on a chip on the spacecraft, which already carries a chip with more than 442,000 names submitted through the 2014 “Messages to Bennu” campaign.
A submission may take the form of a sketch, photograph, graphic, poem, song, short video or other creative or artistic expression that reflects what it means to be an explorer. Submissions will be accepted via Twitter (tagged @OSIRISREx) and Instagram (tagged @OSIRIS_Rex) until March 20th.
Note that all submission must include the hashtag #WeTheExplorers. Videos may be submitted by direct upload to Twitter or Instagram or by including a link to your YouTube or Vimeo video in a correctly tagged tweet. Videos must be no longer than 2 minutes and 30 seconds in length.
Bennu, which is approximately 492 m (1,614 ft) in diameter, has been chosen due to it being a carbonaceous asteroid passing relatively close to Earth in its orbit around the Sun. Carbonaceous material is of significant interest to scientists as it is a key element in organic molecules necessary for life as well as representative of matter from before the formation of Earth. Organic molecules, such as amino acids, have previously been found in meteorite and comet samples, indicating that some ingredients necessary for life can be naturally synthesized in outer space.
The mission will take 7 years to complete: a two-year flight to Bennu following launch, then 505 days spent in orbit mapping the asteroid at a distance of approximately 5 km (3.1 mi). Data from this work will be used to select a sample site. OSIRIS-REx will then commence a very slow descent toward the asteroid, stopping short of actually touching down. Instead, and at an altitude of 5 metres (16ft) above the surface, it will employ a robotic arm system called TAGSAM (Touch-And-Go Sample Acquisition Mechanism), in three sample gathering attempts designed to collect a minimum of 60 grams of material from the asteroid.
The sample gathering should take place around September 2019, before the vehicle makes a return to Earth. On its return, the sample container will be ejected, enter the Earth’s atmosphere and make a parachute landing in Utah in September 2023.
As well as gathering the sample, the Bennu mission will serve to increase our understanding of the asteroid’s physical properties – but not just for reasons of scientific discovery. Recent calculations suggest that the asteroid, which orbits the Sun every 1.2 years, and passes close to Earth every 6 years, could impact our world some time between 2169 and 2199, with the greatest risk of impact potentially occurring on September 24th, 2182. A deeper understand of the asteroid’s composition and physical properties will therefore assist in developing an asteroid impact avoidance mission. | 0.885579 | 3.642497 |
Astronomers discover third planet in the Kepler-47 circumbinary system
Credit: NASA/JPLCaltech/T. Pyle
Astronomers have discovered a third planet in the Kepler-47 system, securing the system’s title as the most interesting of the binary-star worlds. Using data from NASA’s Kepler space telescope, a team of researchers, led by astronomers at San Diego State University, detected the new Neptune-to-Saturn-size planet orbiting between two previously known planets.
With its three planets orbiting two suns, Kepler-47 is the only known multi-planet circumbinary system. Circumbinary planets are those that orbit two stars.
The planets in the Kepler-47 system were detected via the “transit method.” If the orbital plane of the planet is aligned edge-on as seen from Earth, the planet can pass in front of the host stars, leading to a measurable decrease in the observed brightness. The new planet, dubbed Kepler-47d, was not detected earlier due to weak transit signals.
As is common with circumbinary planets, the alignment of the orbital planes of the planets change with time. In this case, the middle planet’s orbit has become more aligned, leading to a stronger transit signal. The transit depth went from undetectable at the beginning of the Kepler Mission to the deepest of the three planets over the span of just four years.
The SDSU researchers were surprised by both the size and location of the new planet. Kepler-47d is the largest of the three planets in the Kepler-47 system.
“We saw a hint of a third planet back in 2012, but with only one transit we needed more data to be sure,” said SDSU astronomer Jerome Orosz, the paper’s lead author. “With an additional transit, the planet’s orbital period could be determined, and we were then able to uncover more transits that were hidden in the noise in the earlier data.”
William Welsh, SDSU astronomer and the study’s co-author, said he and Orosz expected any additional planets in the Kepler-47 system to be orbiting exterior to the previously known planets. “We certainly didn’t expect it to be the largest planet in the system. This was almost shocking,” said Welsh. Their research was recently published in the Astronomical Journal.
With the discovery of the new planet, a much better understanding of the system is possible. For example, researchers now know the planets in this circumbinary system are very low density – less than that of Saturn, the Solar System planet with the lowest density.
While a low density is not that unusual for the sizzling hot-Jupiter type exoplanets, it is rare for mild-temperature planets. Kepler-47d’s equilibrium temperature is roughly 50 o F (10 o C), while Kepler-47c is 26 o F (32 o C). The innermost planet, which is the smallest circumbinary planet known, is a much hotter 336 o F (169 o C).
The inner, middle, and outer planets are 3.1, 7.0, and 4.7 times the size of the Earth, and take 49, 87, and 303 days, respectively, to orbit around their suns. The stars themselves orbit each other in only 7.45 days; one star is similar to the Sun, while the other has a third of the mass of the Sun. The entire system is compact and would fit inside the orbit of the Earth. It is approximately 3340 light-years away in the direction of the constellation Cygnus.
“This work builds on one of the Kepler’s most interesting discoveries: that systems of closely-packed, low-density planets are extremely common in our galaxy,” said University of California, Santa Cruz astronomer Jonathan Fortney, who was not part of the study. “Kepler47 shows that whatever process forms these planets – an outcome that did not happen in our solar system -is common to single-star and circumbinary planetary systems.”
This work was supported in part by grants from NASA and the National Science Foundation. | 0.829653 | 3.736601 |
Subsets and Splits
No community queries yet
The top public SQL queries from the community will appear here once available.