Volcanoes are an impressive force of nature. Physically, they dominate the landscape, and have an active role in shaping our planet’s geography. When they are actively erupting, they are an extremely dangerous and destructive force. But when they are passive, the soil they enrich can become very fertile, leading to settlements and cities being built nearby.
Such is the nature of volcanoes, and is the reason why we distinguish between those that are “active” and those that are “dormant”. But what exactly is the differences between the two, and how do geologists tell? This is actually a complicated question, because there’s no way to know for sure if a volcano is all done erupting, or if it’s going to become active again.
Put simply, the most popular way for classifying volcanoes comes down to the frequency of their eruption. Those that erupt regularly are called active, while those that have erupted in historical times but are now quiet are called dormant (or inactive). But in the end, knowing the difference all comes down to timing!
Sarychev volcano, (located in Russia’s Kuril Islands, northeast of Japan) in an early stage of eruption on June 12, 2009. Credit: NASA
Active Volcano:
Currently, there is no consensus among volcanologists about what constitutes “active”. Volcanoes – like all geological features – can have very long lifespans, varying between months to even millions of years. In the past few thousand years, many of Earth’s volcanoes have erupted many times over, but currently show no signs of impending eruption.
As such, the term “active” can mean only active in terms of human lifespans, which are entirely different from the lifespans of volcanoes. Hence why scientists often consider a volcano to be active only if it is showing signs of unrest (i.e. unusual earthquake activity or significant new gas emissions) that mean it is about to erupt.
Aleutian island #volcano letting off a little steam after the new year on Jan 2, 2016. #YearInSpace. Credit: NASA/Scott Kelly/@StationCDRKelly
By this definition, those volcanoes that have erupted in the course of human history (which includes more than 500 volcanoes) are defined as active. However, this too is problematic, since this varies from region to region – with some areas cataloging volcanoes for thousands of years, while others only have records for the past few centuries.
As such, an “active volcano” can be best described as one that’s currently in a state of regular eruptions. Maybe it’s going off right now, or had an event in the last few decades, or geologists expect it to erupt again very soon. In short, if its spewing fire or likely to again in the near future, then it’s active!
Dormant Volcano:
Meanwhile, a dormant volcano is used to refer to those that are capable of erupting, and will probably erupt again in the future, but hasn’t had an eruption for a very long time. Here too, definitions become complicated since it is difficult to distinguish between a volcano that is simply not active at present, and one that will remain inactive.
Volcanoes are often considered to be extinct if there are no written records of its activity. Nevertheless, volcanoes may remain dormant for a long period of time. For instance, the volcanoes of Yellowstone, Toba, and Vesuvius were all thought to be extinct before their historic and devastating eruptions.
The area around Mount Vesuvius, which erupted in 79 CE, is now densely populated. Credit: Wikipedia Commons/Jeffmatt
The same is true of the Fourpeaked Mountain eruption in Alaska in 2006. Prior to this, the volcano was thought to be extinct since it had not erupted for over 10,000 years. Compare that to Mount Grímsvötn in south-east Iceland, which erupted three times in the past 12 years (in 2011, 2008 and 2004, respectively).
And so a dormant volcano is actually part of the active volcano classification, it’s just that it’s not currently erupting.
Extinct Volcano:
Geologists also employ the category of extinct volcano to refer to volcanoes that have become cut off from their magma supply. There are many examples of extinct volcanoes around the world, many of which are found in the Hawaiian-Emperor Seamount Chain in the Pacific Ocean, or stand individually in some areas.
For example, the Shiprock volcano, which stands in Navajo Nation territory in New Mexico, is an example of a solitary extinct volcano. Edinburgh Castle, located just outside the capitol of Edinburgh, Scotland, is famously located atop an extinct volcano.
Aerial photograph of the Shiprock extinct volcano. Credit: Wikipedia Commons
But of course, determining if a volcano is truly extinct is often difficult, since some volcanoes can have eruptive lifespans that measure into the millions of years. As such, some volcanologists refer to extinct volcanoes as inactive, and some volcanoes once thought to be extinct are now referred to as dormant.
In short, knowing if a volcano is active, dormant, or extinct is complicated and all comes down to timing. And when it comes to geological features, timing is quite difficult for us mere mortals. Individuals and generations have limited life spans, nations rise and fall, and even entire civilization sometimes bite the dust.
But volcanic formations? They can endure for millions of years! Knowing if there still life in them requires hard work, good record-keeping, and (above all) immense patience.
Special Guests:
This week’s guests will be the Universe Sandbox Developers Dan Dixon (Project Lead & Creator) and Jenn Seiler (Astrophysicist & Developer).
We’ve had an abundance of news stories for the past few months, and not enough time to get to them all. So we are now using a tool called Trello to submit and vote on stories we would like to see covered each week, and then Fraser will be selecting the stories from there. Here is the link to the Trello WSH page (http://bit.ly/WSHVote), which you can see without logging in. If you’d like to vote, just create a login and help us decide what to cover!
We record the Weekly Space Hangout every Friday at 12:00 pm Pacific / 3:00 pm Eastern. You can watch us live on Universe Today, or the Universe Today YouTube page.
We usually record Astronomy Cast as a live Google+ Hangout on Air every Friday at 1:30 pm Pacific / 4:30 pm Eastern. You can watch here on Universe Today or from the Astronomy Cast Google+ page.
Mars as seen from Earth on June 13, 2016. Credit and copyright: Damian Peach.
What did you do during your summer this year? Award-winning astrophotographer Damian Peach spent much of his 2016 summer capturing incredibly clear images of Mars during opposition, when the Red Planet was closest to Earth. Peach has now compiled a wonderful “rotating planet” movie of images taken between June 4th – 18th, 2016, showing amazing detail of the planet.
At its closest point this year, Mars was about 46.8 million miles (75.3 million kilometers) from Earth.
Peach has said this summer held “excellent seeing,” both from his home in the UK and from a photography trip to Barbados. He even captured a fleeting localized dust storm on Mars during mid-June over Mare Erythraeum, one of the prominent dark areas on the planet that were once thought to be seas. In the image below of the dust storm, Peach also pointed out the “linear cloud streak in the southern hemisphere – clearly those Martian flying saucer pilots have been having fun!”
Images of Mars from Earth on Jun 15, 2016. Credit and copyright: Damian Peach.
See more of Peach’s excellent astrophotography work at his website , or on Twitter. See a larger version of the lead image here.
Mars is still visible in the night sky, but if you missed seeing this planet at its brightest in 2016, the next time Mars will be at opposition will be in 2018, with close approach on July 31, 2018.
Comet 332P breakup. Credit: NASA, ESA, and D. Jewitt (UCLA)
This Hubble Space Telescope image reveals the ancient Comet 332P/Ikeya-Murakami disintegrating as it approaches the sun. The comet debris consists of a cluster of building-size chunks near the center of the image. They form a trail larger than the width of the continental U.S. The fragments are drifting away from the comet at a leisurely pace of just a few miles an hour. The main nucleus of Comet 332P is the bright object at lower left. It measures 1,600 feet across, about the length of five football fields. Credit: NASA, ESA, and D. Jewitt (UCLA)
Breaking up isn’t hard to do if you’re a comet. They’re fragile creatures subject to splitting, cracking and vaporizing when heated by the Sun and yanked on by its powerful gravitational pull.
Recently, the Hubble Space Telescope captured one of the sharpest, most detailed observations of a comet breaking apart, which occurred 67 million miles from Earth. In a series of images taken over a three-day span in January 2016, Hubble revealed 25 building-size blocks made of a mixture of ice and dust that are drifting away from the main nucleus of the periodic comet 332P/Ikeya-Murakami at a leisurely pace, about the walking speed of an adult.
This animation shows the movement of individual comet fragments relative to the parent nucleus, the bright object at lower left, on January 26, 27 and 28 UT. The true motions are very slow, on the order of several miles an hour, and show a fan-like divergence from the parent. Look closely and you’ll see that some of the fragments change in brightness and even shape from day to day. Researcher David Jewitt thinks this is due to continuing outgassing, rotation and breakup of the fragments. Credit: NASA, ESA, and D. Jewitt (UCLA)
The observations suggest that the comet may be spinning so fast that material is ejected from its surface. The resulting debris is now scattered along a 3,000-mile-long trail, larger than the width of the continental U.S. Much the same happens with small asteroids, when sunlight absorbed unequally across an asteroid’s surface spins up its rotation rate, either causing it to fall apart or fling hunks of itself into space.
Being made of loosely bound frothy ice, comets may be even more volatile compared to the dense rocky composition of many asteroids. The research team suggests that sunlight heated up the comet, causing jets of gas and dust to erupt from its surface. We see this all the time in comets in dramatic images taken by the Rosetta spacecraft of Comet 67P/Churyumov-Gerasimenko. Because the nucleus is so small, these jets act like rocket engines, spinning up the comet’s rotation. The faster spin rate loosened chunks of material, which are drifting off into space.
Comet 168P/Hergenrother was photographed by the Gemini telescope on Nov. 2, 2012 and shows three fragments that broke away from the nucleus streaming from the coma down the tail. Credit: NASA/JPL-Caltech/Gemini
“We know that comets sometimes disintegrate, but we don’t know much about why or how they come apart,” explained lead researcher David Jewitt of the University of California at Los Angeles. “The trouble is that it happens quickly and without warning, and so we don’t have much chance to get useful data. With Hubble’s fantastic resolution, not only do we see really tiny, faint bits of the comet, but we can watch them change from day to day. And that has allowed us to make the best measurements ever obtained on such an object.”
In the animation you can see the comet splinters brighten and fade as icy patches on their surfaces rotate in and out of sunlight. Their shapes even change! Being made of ice and crumbly as a peanut butter cookie, they continue to break apart to spawn a host of smaller cometary bits. The icy relics comprise about 4% of the parent comet and range in size from roughly 65 feet wide to 200 feet wide (20-60 meters). They are moving away from each other at a few miles per hour.
The European Space Agency’s Rosetta probe photographed this big crack in the neck region of the double-lobed comer 67P. It’s several feet wide and about 700 feet long. Could it be an indicator that the comet will break into two in the future? Credit: ESA/Rosetta
Comet 332P was slightly beyond the orbit of Mars when Hubble spotted the breakup. The surviving bright nucleus completes a rotation every 2-4 hours, about four times as fast as Comet 67P/Churyumov-Gerasimenko (a.k.a. “Rosetta’s Comet”). Standing on its surface you’d see the sun rise and set in about an hour, akin to how frequently astronauts aboard the International Space Station see sunsets and sunrises orbiting at over 17,000 mph.
Don’t jump for joy though. Since the comet’s just 1,600 feet (488 meters) across, its gravitational powers are too meek to allow visitors the freedom of hopping about lest they find themselves hovering helplessly in space above the icy nucleus.
This illustration shows one possible explanation for the disintegration of asteroids and comets. The effects of sunlight can cause an asteroid to slowly increase its rotation rate until the loosely bound fragments drift apart due to centrifugal forces. In the case of comets, jets of vaporizing ice have a rocket-like effect that can spin up a nucleus to speeds fast enough for the comet to eject pieces of itself. Credit: NASA, ESA, D. Jewitt (UCLA), and A. Feild (STScI)
Comet 332P was discovered in November 2010, after it surged in brightness and was spotted by two Japanese amateur astronomers, Kaoru Ikeya and Shigeki Murakami. Based on the Hubble data, the team calculated that the comet probably began shedding material between October and December 2015. From the rapid changes seen in the shards over the three days captured in the animation, they probably won’t be around for long.
Spectacular breakup of Comet 73P in 2006
More changes may be in the works. Hubble’s sharp vision also spied a chunk of material close to the comet, which may be the first salvo of another outburst. The remnant from still another flare-up, which may have occurred in 2012, is also visible. The fragment may be as large as Comet 332P, suggesting the comet split in two.
“In the past, astronomers thought that comets die when they are warmed by sunlight, causing their ices to simply vaporize away,” Jewitt said. “Either nothing would be left over or there would be a dead hulk of material where an active comet used to be. But it’s starting to look like fragmentation may be more important. In Comet 332P we may be seeing a comet fragmenting itself into oblivion.”
During its closest approach to the Sun on November 28, 2013, Comet ISON’s nucleus broke apart and soon vaporized away, leaving little more than a ghostly head and fading tail.
Astronomers using the Hubble and other telescopes have seen breakups before, most notably in April 2006 when 73P/Schwassmann-Wachmann 3, which crumbled into more than 60 pieces. Unlike 332P, the comet wasn’t observed long enough to track the evolution of the fragments, but the images are spectacular!
The researchers estimate that Comet 332P contains enough mass to endure another 25 outbursts. “If the comet has an episode every six years, the equivalent of one orbit around the sun, then it will be gone in 150 years,” Jewitt said. “It’s the blink of an eye, astronomically speaking. The trip to the inner Solar System has doomed it.”
This annotated image shows the fragments measured by Jewitt and team and their direction of movement. Credit: NASA, ESA, and D. Jewitt (UCLA)
332P/Ikeya-Murakami hails from the Kuiper Belt, a vast swarm of icy asteroids and comets beyond Neptune. Leftover building blocks from early Solar System and stuck in a deep freeze in the Kuiper Belt, you’d think they’d be left alone to live their solitary, chilly lives but no. After nearly 4.5 billion years in this icy deep freeze, chaotic gravitational perturbations from Neptune kicked Comet 332P out of the Kuiper Belt.
As the comet traveled across the solar system, it was deflected by the planets, like a ball bouncing around in a pinball machine, until Jupiter’s gravity set its current orbit. Jewitt estimates that a comet from the Kuiper Belt gets tossed into the inner solar system every 40 to 100 years.
I wish I could tell you to grab your scope for a look, but 332P is currently fainter than 15th magnitude and located in Libra low in the southwestern sky at nightfall. Hopefully, we’ll see more images in the coming weeks and months as Jewitt and the team continue to follow the evolution of its icy scraps.
Dramatic hillside view showing sloping buttes and layered outcrops within of the Murray Buttes region on lower Mount Sharp from the Mast Camera (Mastcam) on NASA's Curiosity Mars rover. This photo mosaic is stitched and cropped from Mastcam camera raw images taken on Sol 1454, Sept. 8, 2016, with added artificial sky. Credit: NASA/JPL/MSSS/Ken Kremer/kenkremer.com/Marco Di Lorenzo
Spectacular wide angle mosaic view showing sloping buttes and layered outcrops within the Murray Buttes region on lower Mount Sharp from the Mast Camera (Mastcam) on NASA’s Curiosity Mars rover. This photo mosaic is stitched from Mastcam camera raw images taken on Sol 1454, Sept. 8, 2016 with added artificial sky. Credit: NASA/JPL/MSSS/Ken Kremer/kenkremer.com/Marco Di Lorenzo
The most stunning panoramic vistas likely ever snapped by NASA’s Curiosity rover reveal spectacularly layered Martian rock formations in such exquisite detail that they look and feel just like America’s desert Southwest landscapes. They were just captured a week ago and look like a scene straight out of the hugely popular science fiction movie ‘The Martian’ – only they are real !!
Indeed several magnificent panoramas were taken by Curiosity in just the past week and you can see our newly stitched mosaic versions of several – above and below.
The rock formations lie in the “Murray Buttes” region of lower Mount Sharp where Curiosity has been exploring for roughly the past month. She just finished a campaign of detailed science observations and is set to bore a new sampling hole into the Red Planet, as you read this.
While scouting around the “Murray Buttes,” the SUV sized rover captured thousands of color and black and white raw images to document the geology of this thus far most unrivaled spot on the Red Planet ever visited by an emissary from Earth.
So the image processing team of Ken Kremer and Marco Di Lorenzo has begun stitching together wide angle mosaic views starting with images gathered by the high resolution mast mounted Mastcam right color camera, or M-100, on Sept, 8, 2016, or Sol 1454 of the robots operations on Mars.
Dramatic closeup mosaic view of Martian butte with sandstone layers showing cross-bedding in the Murray Buttes region on lower Mount Sharp from the Mast Camera (Mastcam) on NASA’s Curiosity Mars rover. This photo mosaic is stitched from Mastcam camera raw images taken on Sol 1454, Sept. 8, 2016, with added artificial sky. Credit: NASA/JPL/MSSS/Ken Kremer/kenkremer.com/Marco Di Lorenzo
The mosaics give context and show us exactly what the incredible alien surroundings look like where the six wheeled rover is exploring today.
The imagery of the Murray Buttes and mesas show them to be eroded remnants of ancient sandstone that originated when winds deposited sand after lower Mount Sharp had formed.
Wide angle mosaic shows lower region of Mount Sharp at center in between spectacular sloping hillsides and layered rock outcrops of the Murray Buttes region in Gale Crater as imaged by the Mast Camera (Mastcam) on NASA’s Curiosity Mars rover. This photo mosaic is stitched from Mastcam camera raw images taken on Sol 1451, Sept. 5, 2016 with added artificial sky. Credit: NASA/JPL/MSSS/Ken Kremer/kenkremer.com/Marco Di Lorenzo
Scanning around the Murray Buttes mosaics one sees finely layered rocks, sloping hillsides, the distant rim of Gale Crater barely visible through the dusty haze, dramatic hillside outcrops with sandstone layers exhibiting cross-bedding. The presence of “cross-bedding” indicates that the sandstone was deposited by wind as migrating sand dunes, says the team.
Wide angle mosaic view shows spectacular buttes and layered sandstone in the Murray Buttes region on lower Mount Sharp from the Mastcam cameras on NASA’s Curiosity Mars rover. This photo mosaic was assembled from Mastcam color camera raw images taken on Sol 1455, Sept. 9, 2016 and stitched by Marco Di Lorenzo and Ken Kremer, with added artificial sky. Credit: NASA/JPL/MSSS/Ken Kremer/kenkremer.com/Marco Di Lorenzo
But there is no time to rest as she was commanded to head further south to the last of these Murray Buttes. And right now the team is implementing a plan for Curiosity to drill a new hole in Mars today – at a target named “Quela” at the base of the last of the buttes. The rover approached the butte from the south side a few days ago to get in place and plan for the drilling, take imagery to document stratigraphy and make compositional observations with the ChemCam laser instrument.
“It’s always an exciting day on Mars when you prepare to drill another sample – an engineering feat that we’ve become so accustomed to that I sometimes forget how impressive this really is!” wrote Lauren Edgar, in a mission update today. Edgar is a Research Geologist at the USGS Astrogeology Science Center and a member of the MSL science team.
Curiosity will then continue further south to begin exploring higher and higher sedimentary layers up Mount Sharp. The “Murray Buttes” are the entry way along Curiosity’s planned route up lower Mount Sharp.
Dramatic closeup view of hillside outcrop with sandstone layers showing cross-bedding in the Murray Buttes region on lower Mount Sharp from the Mast Camera (Mastcam) on NASA’s Curiosity Mars rover. This photo mosaic is stitched and cropped from Mastcam camera raw images taken on Sol 1454, Sept. 8, 2016, with added artificial sky. Credit: NASA/JPL/MSSS/Ken Kremer/kenkremer.com/Marco Di Lorenzo
Meanwhile Curiosity is still conducting science observations of the last drill sample gathered from the “Marimba” target in August focusing on MAHLI and APXS examination of the dump pile leftovers from the sieved sample. She just completed chemical analysis of the sieved sample using the miniaturized SAM and CheMin internal chemistry laboratories.
It’s interesting to note that although the buttes are striking, their height also presents communications issues by blocking radio signals with NASA’s orbiting relay satellites. NASA’s Opportunity rover faced the same issues earlier this year while exploring inside the high walled Marathon Valley along Ecdeavour Crater.
“While the buttes are beautiful, they pose a challenge to communications, because they are partially occluding communications between the rover and the satellites we use to relay data (MRO and ODY), so sometimes the data volume that we can relay is pretty low” wrote Edgar.
“But it’s a small price to pay for the great stratigraphic exposures and gorgeous view!”
Dramatic hillside view showing sloping buttes and layered outcrops within of the Murray Buttes region on lower Mount Sharp from the Mast Camera (Mastcam) on NASA’s Curiosity Mars rover. This photo mosaic is stitched and cropped from Mastcam camera raw images taken on Sol 1454, Sept. 8, 2016, with added artificial sky. Credit: NASA/JPL/MSSS/Ken Kremer/kenkremer.com/Marco Di Lorenzo
Ascending and diligently exploring the sedimentary lower layers of Mount Sharp, which towers 3.4 miles (5.5 kilometers) into the Martian sky, is the primary destination and goal of the rovers long term scientific expedition on the Red Planet.
Three years ago, the team informally named the Murray Buttes site to honor Caltech planetary scientist Bruce Murray (1931-2013), a former director of NASA’s Jet Propulsion Laboratory, Pasadena, California. JPL manages the Curiosity mission for NASA.
As of today, Sol 1461, September 15, 2016, Curiosity has driven over 7.9 miles (12.7 kilometers) since its August 2012 landing inside Gale Crater, and taken over 353,000 amazing images.
Stay tuned here for Ken’s continuing Earth and planetary science and human spaceflight news.
Curiosity rover panorama of Mount Sharp captured on June 6, 2014 (Sol 651) during traverse inside Gale Crater. Note rover wheel tracks at left. She will eventually ascend the mountain at the ‘Murray Buttes’ at right later this year. Assembled from Mastcam color camera raw images and stitched by Marco Di Lorenzo and Ken Kremer. Credit: NASA/JPL/MSSS/Marco Di Lorenzo/Ken Kremer-kenkremer.com
This artist's drawing shows a stellar black hole as it pulls matter from a blue star beside it. Could the stellar black hole's cousin, the primordial black hole, account for the dark matter in our Universe?
Credits: NASA/CXC/M.Weiss
For almost half a century, scientists have subscribed to the theory that when a star comes to the end of its life-cycle, it will undergo a gravitational collapse. At this point, assuming enough mass is present, this collapse will trigger the formation of a black hole. Knowing when and how a black hole will form has long been something astronomers have sought out.
And why not? Being able to witness the formation of black hole would not only be an amazing event, it would also lead to a treasure trove of scientific discoveries. And according to a recent study by a team of researchers from Ohio State University in Columbus, we may have finally done just that.
The research team was led by Christopher Kochanek, a Professor of Astronomy and an Eminent Scholar at Ohio State. Using images taken by the Large Binocular Telescope (LBT) and Hubble Space Telescope (HST), he and his colleagues conducted a series of observations of a red supergiant star named N6946-BH1.
Artist’s impression of the star in its multi-million year long and previously unobservable phase as a large, red supergiant. Credit: CAASTRO / Mats Björklund (Magipics)
To break the formation process of black holes down, according to our current understanding of the life cycles of stars, a black hole forms after a very high-mass star experiences a supernova. This begins when the star has exhausted its supply of fuel and then undergoes a sudden loss of mass, where the outer shell of the star is shed, leaving behind a remnant neutron star.
This is then followed by electrons reattaching themselves to hydrogen ions that have been cast off, which causes a bright flareup to occur. When the hydrogen fusing stops, the stellar remnant begins to cool and fade; and eventually the rest of the material condenses to form a black hole.
However, in recent years, several astronomers have speculated that in some cases, stars will experience a failed supernova. In this scenario, a very high-mass star ends its life cycle by turning into a black hole without the usual massive burst of energy happening beforehand.
Artistic representation of the material around the supernova 1987A. Credit: ESO/L.
Using information obtained with the LBT, the team noted that N6946-BH1 showed some interesting changes in its luminosity between 2009 and 2015 – when two separates observations were made. In the 2009 images, N6946-BH1 appears as a bright, isolated star. This was consistent with archival data taken by the HST back in 2007.
However, data obtained by the LBT in 2015 showed that the star was no longer apparent in the visible wavelength, which was also confirmed by Hubble data from the same year. LBT data also showed that for several months during 2009, the star experienced a brief but intense flare-up, where it became a million times brighter than our Sun, and then steadily faded away.
They also consulted data from the Palomar Transit Factory (PTF) survey for comparison, as well as observations made by Ron Arbour (a British amateur astronomer and supernova-hunter). In both cases, the observations showed evidence of a flare during a brief period in 2009 followed by a steady fade.
In the end, this information was all consistent with the failed supernovae-black hole model. As Prof. Kochanek, the lead author of the group’s paper – – told Universe Today via email:
“In the failed supernova/black hole formation picture of this event, the transient is driven by the failed supernova. The star we see before the event is a red supergiant — so you have a compact core (size of ~earth) out the hydrogen burning shell, and then a huge, puffy extended envelope of mostly hydrogen that might extend out to the scale of Jupiter’s orbit. This envelope is very weakly bound to the star. When the core of the star collapses, the gravitational mass drops by a few tenths of the mass of the sun because of the energy carried away by neutrinos. This drop in the gravity of the star is enough to send a weak shock wave through the puffy envelope that sends it drifting away. This produces a cool, low-luminosity (compared to a supernova, about a million times the luminosity of the sun) transient that lasts about a year and is powered by the energy of recombination. All the atoms in the puffy envelope were ionized — electrons not bound to atoms — as the ejected envelope expands and cools, the electrons all become bound to the atoms again, which releases the energy to power the transient. What we see in the data is consistent with this picture.”
The Large Binocular Telescope, showing the two imaging mirrors. Credit: NASA
Naturally, the team considered all available possibilities to explain the sudden “disappearance” of the star. This included the possibility that the star was shrouded in so much dust that its optical/UV light was being absorbed and re-emitted. But as they found, this did not accord with their observations.
“The gist is that no models using dust to hide the star really work, so it would seem that whatever is there now has to be much less luminous then that pre-existing star.” Kochanek explained. “Within the context of the failed supernova model, the residual light is consistent with the late time decay of emission from material accreting onto the newly formed black hole.”
Naturally, further observations will be needed before we can know whether or not this was the case. This would most likely involve IR and X-ray missions, such as the Spitzer Space Telescope and the Chandra X-ray Observatory, or one of he many next-generation space telescopes to be deployed in the coming years.
In addition, Kochanek and his colleagues hope to continue monitoring the possible black hole using the LBT, and by re-visiting the object with the HST in about a year from now. “If it is true, we should continue to see the object fade away with time,” he said.
Future missions, like the James Webb Space Telescope, will be able to observe possible failed supernovae/blackholes to confirm their existence. Credit: NASA/JPL
Needless to say, if true, this discovery would be an unprecedented event in the history of astronomy. And the news has certainly garnered its share of excitement from the scientific community. As Avi Loeb – a professor of astronomy at Harvard University – expressed to Universe Today via email:
“The announcement on the potential discovery of a star that collapsed to make a black hole is very interesting. If true, it will be the first direct view of the delivery room of a black hole. The picture is somewhat messy (like any delivery room), with uncertainties about the properties of the baby that was delivered. The way to confirm that a black hole was born is to detect X-rays.
“We know that stellar-mass black holes exist, most recently thanks to the discovery of gravitational waves from their coalescence by the LIGO team. Almost eighty years ago Robert Oppenheimer and collaborators predicted that massive stars may collapse to black holes. Now we might have the first direct evidence that the process actually happens in nature.
But of course, we must remind ourselves that given its distance, what we could be witnessing with N6946-BH1 happened 20 million years ago. So from the perspective of this potential black hole, its formation is old news. But to us, it could be one of the most groundbreaking observations in the history of astronomy.
Much like space and time, significance is relative to the observer!
Look up at the night sky, and what do you see? Space, glittering and gleaming in all its glory. Astronomically speaking, space is really quite close, lingering just on the other side of that thin layer we call an atmosphere. And if you think about it, Earth is little more than a tiny island in a sea of space. So it is quite literally all around us.
By definition, space is defined as being the point at which the Earth’s atmosphere ends, and the vacuum of space begins. But exactly how far away is that? How high do you need to travel before you can actually touch space? As you can probably imagine, with such a subjective definition, people tend to disagree on exactly where space begins.
Definition:
The first official definition of space came from the National Advisory Committee for Aeronautics (the predecessor to NASA), who decided on the point where atmospheric pressure was less than one pound per square foot. This was the altitude that airplane control surfaces could no longer be used, and corresponded to roughly 81 kilometers (50 miles) above the Earth’s surface.
The Bell X-1, in which Chuck Yeager “broke” the sound barrier in 1947. Credit: NASA
Any NASA test pilot or astronaut who crosses this altitude is awarded their astronaut wings. Shortly after that definition was passed, the aerospace engineer Theodore von Kármán calculated that above an altitude of 100 km, the atmosphere would be so thin that an aircraft would need to be traveling at orbital velocity to derive any lift.
This altitude was later adopted as the Karman Line by the World Air Sports Federation (Fédération Aéronautique Internationale, FAI). And in 2012, when Felix Baumgartner broke the record for the highest freefall, he jumped from an altitude of 39 kilometers (24.23 mi), less than halfway to space (according to NASA’s definition).
By the same token, space is often defined as beginning at the lowest altitude at which satellites can maintain orbits for a reasonable time – which is approximately 160 kilometers (100 miles) above the surface. These varying definitions are complicated when one takes the definition of the word “atmosphere” into account.
Earth’s Atmosphere:
When we talk about Earth’s atmosphere, we tend to think of the region where air pressure is still high enough to cause air resistance, or where the air is simply thick enough to breath. But in truth, Earth’s atmosphere is made up of five main layers – the Troposphere, the Stratosphere, the Mesosphere, the Thermosphere, and the Exosphere – the latter of which extend pretty far out into space.
Space Shuttle Endeavor silhouetted against Earth’s atmosphere. The orange layer is the troposphere, the white layer is the stratosphere and the blue layer the mesosphere. Credit: NASAThe Thermosphere, the second highest layer of the atmosphere, extends from an altitude of about 80 km (50 mi) up to the thermopause, which is at an altitude of 500–1000 km (310–620 mi). The lower part of the thermosphere, – from 80 to 550 kilometers (50 to 342 mi) – contains the ionosphere, which is so named because it is here in the atmosphere that particles are ionized by solar radiation.
Hence, this is where the phenomena known as Aurora Borealis and Aurara Australis are known to take place. The International Space Station also orbits in this layer, between 320 and 380 km (200 and 240 mi), and needs to be constantly boosted because friction with the atmosphere still occurs.
The outermost layer, known as the exosphere, extends out to an altitude of 10,000 km (6214 mi) above the planet. This layer is mainly composed of extremely low densities of hydrogen, helium and several heavier molecules (nitrogen, oxygen, CO²). The atoms and molecules are so far apart that the exosphere no longer behaves like a gas and the particles constantly escape into space.
It is here that Earth’s atmosphere truly merges with the emptiness of outer space, where there is no atmosphere. Hence why the majority of Earth’s satellites orbit within this region. Sometimes, the Aurora Borealis and Aurora Australis occur in the lower part of the exosphere, where they overlap into the thermosphere. But beyond that, there is no meteorological phenomena in this region.
Interplanetary vs. Interstellar:
Another important distinction when discussing space is the difference between that which lies between planets (interplanetary space) and that which lies between star systems (interstellar space) in our galaxy. But of course, that’s just the tip of the iceberg when it comes to space.
If one were to cast the net wider, there is also the space which lies between galaxies in the Universe (intergalactic space). In all cases, the definition involves regions where the concentration of matter is significantly lower than in other places – i.e. a region occupied centrally by a planet, star or galaxy.
In addition, in all three definitions, the measurements involved are beyond anything that we humans are accustomed to dealing with on a regular basis. Some scientists believe that space extends infinitely in all directions, while others believe that space is finite, but is unbounded and continuous (i.e. has no beginning and end).
In other words, there’s a reason they call it space – there’s just so much of it!
Exploration:
The exploration of space (that is to say, that which lies immediately beyond Earth’s atmosphere) began in earnest with what is known as the “Space Age“, This newfound age of exploration began with the United States and Soviet Union setting their sights on placing satellites and crewed modules into orbit.
The first major event of the Space Age took place on October 4th, 1957, with the launch ofSputnik 1 by the Soviet Union – the first artificial satellite to be launched into orbit. In response, then-President Dwight D. Eisenhower signed the National Aeronautics and Space Act on July 29th, 1958, officially establishing NASA.
Photograph of a Russian technician putting the finishing touches on Sputnik 1, humanity’s first artificial satellite. Credit: NASA/Asif A.
Immediately, NASA and the Soviet space program began taking the necessary steps towards creating manned spacecraft. By 1959, this competition resulted in the creation of the Soviet Vostok program and NASA’s Project Mercury. In the case of Vostok, this consisted of developing a space capsule that could be launched aboard an expendable carrier rocket.
Along with numerous unmanned tests, and a few using dogs, six Soviet pilots were selected by 1960 to be the first men to go into space. On April 12th, 1961, Soviet cosmonaut Yuri Gagarin was launched aboard the Vostok 1spacecraft from the Baikonur Cosmodrome, and thus became the fist man to go into space (beating American Alan Shepard by just a few weeks).
On June 16th, 1963, Valentina Tereshkova was sent into orbit aboard the Vostok 6 craft (which was the final Vostok mission), and thus became the first woman to go into space. Meanwhile, NASA took over Project Mercury from the US Air Force and began developing their own crewed mission concept.
Yury Gagarin before a space flight aboard the Vostok spacecraft. April 12, 1961 Credit: RIA Novosti
Designed to send a man into space using existing rockets, the program quickly adopted the concept of launching ballistic capsules into orbit. The first seven astronauts, nicknamed the “Mercury Seven“, were selected from from the Navy, Air Force and Marine test pilot programs.
On May 5th, 1961, astronaut Alan Shepard became the first American in space aboard the Freedom 7 mission. Then, on February 20th, 1962, astronaut John Glenn became the first American to be launched into orbit by an Atlas launch vehicle as part of Friendship 7. Glenn completed three orbits of planet Earth, and three more orbital flights were made, culminating in L. Gordon Cooper’s 22-orbit flight aboard Faith 7, which flew on May 15th and 16th, 1963.
In the ensuing decades, both NASA and Soviets began to develop more complex, long-range crewed spacecraft. Once the “Race to the Moon” ended with the successful landing of Apollo 11 (followed by several more Apollo missions), the focus began to shift to establishing a permanent presence in space.
For the Russians, this led to the continued development of space station technology as part of the Salyut program. Between 1972 and 1991, they attempted to orbit seven separate stations. However, technical failures and a failure in one rocket’s second stage boosters caused the first three attempts after Salyut 1 to fail or result in the station’s orbits decaying after a short period.
Skylab, America’s First manned Space Station. Photo taken by departing Skylab 4 crew in Feb. 1974. Credit: NASA
However, by 1974, the Russians managed to successfully deploy Salyut 4, followed by three more stations that would remain in orbit for periods of between one and nine years. While all of the Salyuts were presented to the public as non-military scientific laboratories, some of them were actually covers for the military Almaz reconnaissance stations.
NASA also pursued the development of space station technology, which culminated in May of 1973 with the launch of Skylab, which would remain America’s first and only independently-built space station. During deployment, Skylab suffered severe damage, losing its thermal protection and one of its solar panels.
This required the first crew to rendezvous with the station and conduct repairs. Two more crews followed, and the station was occupied for a total of 171 days during its history of service. This ended in 1979 with the downing of the station over the Indian Ocean and parts of southern Australia.
By 1986, the Soviets once again took the lead in the creation of space stations with the deployment of Mir. Authorized in February 1976 by a government decree, the station was originally intended to be an improved model of the Salyut space stations. In time, it evolved into a station consisting of multiple modules and several ports for crewed Soyuz spacecraft and Progress cargo spaceships.
The Mir Space Station and Earth limb observed from the Orbiter Endeavour during NASA’s STS-89 mission in 1998. Credit: NASA
The core module was launched into orbit on February 19th, 1986; and between 1987 and 1996, all of the other modules would be deployed and attached. During its 15-years of service, Mir was visited by a total of 28 long-duration crews. Through a series of collaborative programs with other nations, the station would also be visited by crews from other Eastern Bloc nations, the European Space Agency (ESA), and NASA.
After a series of technical and structural problems caught up with the station, the Russian government announced in 2000 that it would decommission the space station. This began on Jan. 24th, 2001, when a Russian Progress cargo ship docked with the station and pushed it out of orbit. The station then entered the atmosphere and crashed into the South Pacific.
By 1993, NASA began collaborating with the Russians, the ESA and the Japan Aerospace Exploration Agency (JAXA) to create the International Space Station (ISS). Combining NASA’s Space Station Freedom project with the Soviet/Russian Mir-2 station, the European Columbus station, and the Japanese Kibo laboratory module, the project also built on the Russian-American Shuttle-Mir missions (1995-1998).
With the retirement of the Space Shuttle Program in 2011, crew members have been delivered exclusively by Soyuz spacecraft in recent years. Since 2014, cooperation between NASA and Roscosmos has been suspended for most non-ISS activities due to tensions caused by the situation in the Ukraine.
However, in the past few years, indigenous launch capability has been restored to the US thanks to companies like SpaceX, United Launch Alliance, and Blue Origin stepping in to fill the void with their private fleet of rockets.
The ISS has been continuously occupied for the past 15 years, having exceeded the previous record held by Mir; and has been visited by astronauts and cosmonauts from 15 different nations. The ISS program is expected to continue until at least 2020, but may be extended until 2028 or possibly longer, depending on the budget environment.
As you can clearly see, where our atmosphere ends and space begins is the subject of some debate. But thanks to decades of space exploration and launches, we have managed to come up with a working definition. But whatever the exact definition is, if you can get above 100 kilometers, you have definitely earned your astronaut wings!
The Full Moon of August 18, 2016 rises amid cloud over a wheat field. Friday night will see the rising of the annual Harvest Moon. Credit: Alan Dyer
It’s that wonderful time of year again when the Harvest Moon teeters on the horizon at sunset. You can watch the big orange globe rise on Friday (Sept. 16) from your home or favorite open vista just as soon as the Sun goes down. Despite being one of the most common sky events, a Full Moon rise still touches our hearts and minds every time. No matter how long I live, there will never be enough of them.
Friday night’s Harvest Moon rises around sunset in the faint constellation Pisces the fish. Watch for it to come up almost due east around the time of sunset. Once the sky gets dark, look two fists above and left of the Moon for the four stars that outline the spacious asterism of Pegasus the flying horse. Stellarium
To see a moonrise, the most important information you need is the time the moon pops up for your city, which you’ll find by using this Moonrise and Moonset calculator. Once you know when our neighborly night light rises, pre-arrange a spot you can walk or drive to 10-15 minutes beforehand. The waiting is fun. Who will see it first? I’ll often expect to see the Moon at a certain point along the horizon then be surprised it’s over there.
A photographer finds just the right spot in Duluth along Lake Superior to photograph a rising Full Moon. The flattened shape of the Moon is caused by the layer of denser air closer to the horizon refracting or bending the bottom half of the Moon more strongly than the thinner air along the top limb. In effect, refraction “lifts” the bottom half of the Moon upward into the top to give it a squashed appearance. Once the Moon rises high enough so we see it through much thinner (less dense) air, refraction becomes negligible and the Moon assumes its more familiar circular shape. Credit: Bob King
Depending on how low to the horizon you can see, it’s possible, especially over water, to catch the first glimpse of lunar limb breaching the horizon. This still can be a tricky feat because the Moon is pale, and when it rises, shows little contrast against the still-bright sky. Since the Moon moves about one outstretched fist to the east (left in the northern hemisphere) each night, if you wait until one night after full phase, the Moon will rise in a much darker sky and appear in more dramatic contrast against the sky background.
This photo sequence showing an extraordinary moonset taken from the shores of Garrison Lake in Port Orford, Oregon. “The distortion that occurred as it descended was quite remarkable — the Moon’s shape was changing as fast as I could snap a picture,” said photographer Randy Scholten. As the Moon rises, we peer through hundreds of miles of the lower atmosphere, where the air is densest and dustiest. Aerosols scatter much of the blues and greens in moonlight away, leaving orange and red. Turbulence and varying air densities along the line of sight can create all manner of distortions of the lunar disk. Credit: Randy Scholten
Look closely at the rising Moon with both naked eye and binoculars and you might just see a bit of atmospheric sorcery at work. Refraction, illustrated the icy moonrise image above, is the big one. It creates the squashed Moon shape. But more subtle things are happening that depend on how turbulent or calm the air is along your line of sight to our satellite.
Clouds add their own beauty and mystery to the rising Moon. Credit: Bob King
Rippling waves “sizzling” around the lunar circumference can be striking in binoculars though the effect is quite subtle with the naked eye. Much easier to see without any optical aid are the weird shapes the Moon can assume depending upon the state of the atmosphere. It can looked stretched out like a hot air balloon, choppy with a step-like outline around its bottom or top, square, split into two moons or even resemble a “mushroom cloud”.
If you make a point to watch moonrises regularly, you’ll become acquainted as much with Earth’s atmosphere as with the alien beauty of our sole satellite.
This Full Moon is special in at least two ways. First, it will undergo a penumbral eclipse for skywatchers across eastern Europe, Africa, Asia and Australia. Observers there should watch a dusky gray shading over the upper or northern half of the Moon around the time of maximum eclipse. The link will take you to Dave Dickinson’s excellent article that appeared earlier here at Universe Today.
The angle of the moon’s path to the horizon makes all the difference in moonrise times. At full phase in spring, the path tilts steeply southward, delaying successive moonrises by over an hour. In September, the moon’s path is nearly parallel to the horizon with successive moonrises just 20+ minutes apart. Times shown are for illustration only — so you can see the dramatic different in rise times — and don’t refer necessarily to Friday night’s moonrise. Illustration: Bob King
In the northern hemisphere, September’s Full Moon is named the Harvest Moon, defined as the Full Moon closest to the autumnal equinox, which occurs at 9:21 a.m. CDT (14:21 UT) on the 22nd. Normally, the Moon rises on average about 50 minutes later each night as it moves eastward along its orbit. But at Harvest Moon, successive moonrises are separated by a half-hour or less as viewed from mid-northern latitudes. The short gap of time between between bright risings gave farmers in the days before electricity extra light to harvest their crops, hence the name.
Use your imagination and you can see any of several figures in the Full Moon composed of contrasting maria and highlands.
Why the faster-than-usual moonrises? Every September, the Full Moon’s nightly travels occur at a shallow angle to the horizon; as the moon scoots eastward, it’s also moving northward this time of year as shown in the illustration above. The northern and eastward motions combine to make the Moon’s path nearly level to the horizon. For several nights in a row, it only takes a half-hour for the Earth’s rotation to carry the Moon up from below the horizon. In spring, the angle is steep because the Moon is then moving quickly southward along or near the ecliptic, the path it takes around the sky. Rising times can exceed an hour.
As you gaze at the Moon over the next several nights, take in the contrast between its ancient crust, called the lunar highlands, and the darker seas (also known as maria, pronounced MAH-ree-uh). The crust appears white because it’s rich in calcium and aluminum, while the maria are slightly more recent basaltic lava flows rich in iron, which lends them a darker tone. Thanks to these two different types of terrain it’s easy to picture a male or female face or rabbit or anything your imagination desires.
![Space Shuttle Endeavour sillouetted against the atmosphere. The orange layer is the troposphere, the white layer is the stratosphere and the blue layer the mesosphere.[1] (The shuttle is actually orbiting at an altitude of more than 320 km (200 mi), far above all three layers.) Credit: NASA](https://www.universetoday.com/wp-content/uploads/2012/03/Endeavour_silhouette_STS-130.jpg)
