Why super-sized beavers went extinct

A side-by-side comparison of a modern beaver, a human male (in this case, Justin Bieber) and a giant bear-sized beaver from 10,000 years ago. Illustration by Scott Woods/Western University.

By Tessa Plint, Western University

Giant beavers the size of black bears once roamed the lakes and wetlands of North America. Fortunately for cottage-goers, these mega-rodents died out at the end of the last ice age.

Now extinct, the giant beaver was once a highly successful species. Scientists have found its fossil remains at sites from Florida to Alaska and the Yukon.

A super-sized version of the modern beaver in appearance, the giant beaver tipped the scales at 100 kilograms [220 pounds]. But it had two crucial differences.

The giant beaver lacked the iconic paddle-shaped tail we see on today’s modern beavers. Instead it had a long skinny tail like a muskrat.

The teeth also looked different. Modern beaver incisors (front teeth) are sharp and chisel-like; giant beaver incisors were bulkier and curved, and lacked a sharp cutting edge.

Giant beaver skull. Image via Florida Museum of Natural History.

The species suddenly became extinct 10,000 years ago. The disappearance of the giant beaver coincides with that of many other large-bodied ice age animals, including the iconic woolly mammoth. But until now scientists didn’t know for certain why the giant rodent had died out.

You are what you eat

We need to understand how the giant beaver lived in order to explain how and why it died out. For example, did it run out of food? Did it get too cold or too hot for it to survive?

Other studies found the giant beaver thrived when the climate was warmer and wetter. They also noticed that giant beaver fossils were most commonly found in sediments that come from ancient wetlands. But no one knew if the giant beaver behaved like the modern beaver. Did it also cut down trees? Or did it eat something completely different?

From a chemical perspective, you are what you eat! The food an animal consumes contains chemical signatures called stable isotopes that are incorporated into body tissues such as bone.

These isotopic signatures remain stable over time, for tens of thousands of years, and provide a window into the past. No other studies have used stable isotopes to figure out the giant beaver’s diet.

The now-extinct giant beaver once lived from Florida to Alaska. It weighed as much as 220 pounds (100 kilograms), roughly the same as a small black bear. Illustration via Luke Dickey/Western University.

We studied fossil bones from giant beavers that lived in the Yukon and Ohio between 50,000 and 10,000 years ago. We looked at the stable isotope signatures of the ancient bone tissues.

The isotopic signatures linked to woody plants are different from those associated with aquatic plants. We discovered that the giant beaver was not cutting down and eating trees. Instead, it was eating aquatic plants.

This strongly suggests that the giant beaver was not an “ecosystem engineer” like the modern beaver. It was not cutting down trees for food or building giant lodges and dams across the ice age landscape.

Instead, this diet of aquatic plants made the giant beaver highly dependent on wetland habitat for both food and shelter from predators. It also made it vulnerable to climate change.

Warm and dry climate

Towards the end of the last ice age 10,000 years ago, the climate became increasingly warm and dry and wetland habitats began to dry up. Although the modern beavers and the giant beaver co-existed on the landscape for tens of thousands of years, only one species survived.

The ability to build dams and lodges may have given the modern beaver a competitive advantage over the giant beaver. With its sharp teeth, the modern beaver could alter the landscape to create suitable wetland habitat where it needed it. The giant beaver couldn’t.

A giant beaver skeleton. Image via Tessa Plint.

This all fits into the puzzle that many research groups have been working on for decades: we all want to know what caused the global megafauna extinction event that occurred at the end of the last ice age and why so many species of large-bodied animals — woolly mammoths, mastodons and giant ground sloths — disappeared at roughly the same time.

Current evidence indicates that a combination of climate change and human impact were the driving causes behind these extinctions.

Studying the ecological vulnerabilities of long-extinct animals certainly poses its own unique challenges, but it is important to understand the impact of climate change on all species, past or present.

Tessa Plint, Ph.D. researcher, Heriot-Watt University, and former graduate student, Western University

This article is republished from The Conversation under a Creative Commons license. Read the original article.

Bottom line: Human-sized beavers in North America suddenly became extinct at the end of the last ice age 10,000 years ago, while small modern beavers survived. By studying fossils, scientists have discovered that giant beavers ate aquatic plants instead of trees, leaving the species vulnerable to climate change.

from EarthSky http://bit.ly/2Ko9uE6

A side-by-side comparison of a modern beaver, a human male (in this case, Justin Bieber) and a giant bear-sized beaver from 10,000 years ago. Illustration by Scott Woods/Western University.

By Tessa Plint, Western University

Giant beavers the size of black bears once roamed the lakes and wetlands of North America. Fortunately for cottage-goers, these mega-rodents died out at the end of the last ice age.

Now extinct, the giant beaver was once a highly successful species. Scientists have found its fossil remains at sites from Florida to Alaska and the Yukon.

A super-sized version of the modern beaver in appearance, the giant beaver tipped the scales at 100 kilograms [220 pounds]. But it had two crucial differences.

The giant beaver lacked the iconic paddle-shaped tail we see on today’s modern beavers. Instead it had a long skinny tail like a muskrat.

The teeth also looked different. Modern beaver incisors (front teeth) are sharp and chisel-like; giant beaver incisors were bulkier and curved, and lacked a sharp cutting edge.

Giant beaver skull. Image via Florida Museum of Natural History.

The species suddenly became extinct 10,000 years ago. The disappearance of the giant beaver coincides with that of many other large-bodied ice age animals, including the iconic woolly mammoth. But until now scientists didn’t know for certain why the giant rodent had died out.

You are what you eat

We need to understand how the giant beaver lived in order to explain how and why it died out. For example, did it run out of food? Did it get too cold or too hot for it to survive?

Other studies found the giant beaver thrived when the climate was warmer and wetter. They also noticed that giant beaver fossils were most commonly found in sediments that come from ancient wetlands. But no one knew if the giant beaver behaved like the modern beaver. Did it also cut down trees? Or did it eat something completely different?

From a chemical perspective, you are what you eat! The food an animal consumes contains chemical signatures called stable isotopes that are incorporated into body tissues such as bone.

These isotopic signatures remain stable over time, for tens of thousands of years, and provide a window into the past. No other studies have used stable isotopes to figure out the giant beaver’s diet.

The now-extinct giant beaver once lived from Florida to Alaska. It weighed as much as 220 pounds (100 kilograms), roughly the same as a small black bear. Illustration via Luke Dickey/Western University.

We studied fossil bones from giant beavers that lived in the Yukon and Ohio between 50,000 and 10,000 years ago. We looked at the stable isotope signatures of the ancient bone tissues.

The isotopic signatures linked to woody plants are different from those associated with aquatic plants. We discovered that the giant beaver was not cutting down and eating trees. Instead, it was eating aquatic plants.

This strongly suggests that the giant beaver was not an “ecosystem engineer” like the modern beaver. It was not cutting down trees for food or building giant lodges and dams across the ice age landscape.

Instead, this diet of aquatic plants made the giant beaver highly dependent on wetland habitat for both food and shelter from predators. It also made it vulnerable to climate change.

Warm and dry climate

Towards the end of the last ice age 10,000 years ago, the climate became increasingly warm and dry and wetland habitats began to dry up. Although the modern beavers and the giant beaver co-existed on the landscape for tens of thousands of years, only one species survived.

The ability to build dams and lodges may have given the modern beaver a competitive advantage over the giant beaver. With its sharp teeth, the modern beaver could alter the landscape to create suitable wetland habitat where it needed it. The giant beaver couldn’t.

A giant beaver skeleton. Image via Tessa Plint.

This all fits into the puzzle that many research groups have been working on for decades: we all want to know what caused the global megafauna extinction event that occurred at the end of the last ice age and why so many species of large-bodied animals — woolly mammoths, mastodons and giant ground sloths — disappeared at roughly the same time.

Current evidence indicates that a combination of climate change and human impact were the driving causes behind these extinctions.

Studying the ecological vulnerabilities of long-extinct animals certainly poses its own unique challenges, but it is important to understand the impact of climate change on all species, past or present.

Tessa Plint, Ph.D. researcher, Heriot-Watt University, and former graduate student, Western University

This article is republished from The Conversation under a Creative Commons license. Read the original article.

Bottom line: Human-sized beavers in North America suddenly became extinct at the end of the last ice age 10,000 years ago, while small modern beavers survived. By studying fossils, scientists have discovered that giant beavers ate aquatic plants instead of trees, leaving the species vulnerable to climate change.

from EarthSky http://bit.ly/2Ko9uE6

Word of the week: Ecliptic

Animated depiction of Earth (the blue ball) orbiting the sun (the yellow ball), showing the projection of Earth-sun plane – the ecliptic – onto the background stars. Image via Tfr000/Wikimedia Commons.

Have you ever noticed that the sun, moon and planets all follow more or less the same path across our sky? Unless you live at or near a high Arctic or Antarctic latitude, you’ll never find the sun or moon due north, or due south, near your horizon. Instead, most of us on Earth see objects in our solar system crossing from the eastern to the western sky, as Earth spins, each day. If you get a chance to look for the bright planets when they’re all in the sky at the same time – as happens every year or so – you’ll see the visible planets trace out an easily observed line from the eastern to western horizon. It’s the same path the sun takes each day across our sky. This imaginary line, the path of the sun, is called the ecliptic.

Technically speaking, the Earth’s orbit defines the ecliptic. As viewed from space, the ecliptic is the Earth-sun plane. As viewed from Earth, the ecliptic is a great circle around our sky, formed by the intersection of Earth’s orbital plane with the imaginary celestial sphere surrounding us.

The sun travels around our sky on the great circle of the ecliptic. The moon and planets do, too, more or less. Why? It’s mainly because, long ago, before there was a solar system as we know it today, there was a vast cloud of gas and dust in space. This cloud was spinning, and, as it spun, it flattened out. Our sun formed in the center of this cloud, and the major planets and most other solar system objects formed in the flat disk surrounding the sun.

The ecliptic is defined by the plane of Earth’s orbit around the sun. The major planets in our solar system, and some asteroids, orbit more or less in this same plane. Image via Pics-about-Space.com.

Maybe you’ve noticed the green line on many of the charts in EarthSky’s Tonight pages. That green line marks the location of the ecliptic in our sky. Read more about the view June 4-6, 2019. Note that the angle of the ecliptic with respect to your horizon varies seasonally, and from place to place on Earth.

Today, we still see the major planets – and many of the minor planets aka asteroids – orbiting the sun approximately in this same plane, the plane of Earth’s orbit around the sun: the ecliptic. If we could watch the solar system from far above the Earth’s north pole, we’d see the planets, moons, asteroids, and some of the comets (but not all of them) rushing around the sun counterclockwise in this plane, like marbles rolling around a dish. Actually, the major planets are more within the dish than on it. They’re within the plane of the ecliptic, more or less. They retain the outline of the original cloud in space from which they were born, and their movement around the sun is an echo of the original spin of the cloud.

Since we’re in that plane, too – within the dish – we look into our sky to see edgewise into the plane of the solar system. And so we see these solar system objects travel along the ecliptic, the sun’s path, more or less.

Moon and planets on October 12, 2016, by Karthik Easvur in Hyderabad, India. The moon and planets trace out a line across our sky because they all orbit the sun, more or less, in a single plane. And – as seen from Earth – we look edgewise into that flat plane of the solar system.

Far beyond the cold edges of our solar system, we see the stars of our Milky Way galaxy. The stars are moving, too, but they’re so far away that they don’t seem to move over the course of a human lifespan. And so we speak of the “fixed” stars. Fixed stars on the ecliptic – or sun’s path – seemed special to the early stargazers. They identified constellations made of these stars, and used the word zodiac for the wider pathway traveled by these constellations. And so we find the sun, moon and our major planets within the constellations of the zodiac.

Now about that phrase we keep using, the phrase more or less …

The other planets don’t orbit exactly in the Earth-sun plane. Each major planet’s orbit is inclined a little bit to this plane. Some of the asteroids have orbits that are more inclined. And comets tend to have the most inclined orbits of all. Click here to see the inclinations of the major planets’ orbits.

Interestingly, Earth’s moon isn’t exactly on the ecliptic, either. Its orbit around Earth is tilted by about 5.15 degrees relative to the ecliptic. This means the moon spends most of its time above or below the ecliptic. It crosses it twice each orbit; once going upward and once downward from our point of view. We usually see the moon close to, but not exactly alongside the other solar system objects. On the other hand, the moon sometimes passes right in front of other solar system objects, in an event called an occultation.

So there are little variations. But – for all practical purposes of skywatching – you can think of the ecliptic as a line across our sky. You can think of the sun, moon and major planets of the solar system as moving along that line. One thing to remember, though. The sun’s path is high in summer and low in winter. So the location of the ecliptic in your sky shifts a bit, seasonally.

The ecliptic on June 21, 2019, and December 21, 2019. Image from Stellarium,

If the word ecliptic sounds familiar, you’re right. It’s from the same root as the word eclipse, from the Latin and Greek meaning to “fail to appear” or “to be hidden;” the moon hides the sun during an eclipse. The ecliptic got its name because the ancients saw that solar eclipses happen when the moon crosses the ecliptic during the new moon phase.

Later, astronomers gave the name node to the places where the moon crosses the ecliptic. If the moon traveled exactly on the ecliptic, and the other planets did, too, the moon would occult, or block out, all the planets and the sun every orbit. We’d have lunar and solar eclipses every month. Ho hum.

If you’re able, keep an eye on the sun, the moon and the planets for a while; a few days, a few weeks, months, years, even. You’ll begin to get a feel for the ecliptic in your sky. You’ll notice the planets, sun and moon are always on or near the ecliptic, and you can use this line across your sky to help you find your way around, making your way between the constellations and stars. You’ll notice the sun’s path – the ecliptic – higher in the sky during the summer months and lower during the winter. Eventually, you’ll be able to imagine the sun’s path in your sky, long after the sun has set.

When that happens, you’ll be able to pick out a planet from a star very quickly and easily, which is a great party trick. Mars is the red one; Saturn the yellow one; Venus the bright white one that never gets too far from the sun; Mercury the seldom-seen one; and Jupiter the very bright one (but never as bright as Venus) that often gets far from the sun.

Welcome to stargazing, friend!

View larger. | The cameras of the Voyager 1 spacecraft acquired the images to create this mosaic on February 14, 1990, as it journeyed out of the solar system. It pointed back toward the sun and took this series of pictures of our sun and several major planets, making the first-ever “portrait” of our solar system as seen from the outside. The mosaic consists of a total of 60 frames. Voyager 1 was at a distance of approximately 4 billion miles and about 32 degrees above the ecliptic plane. Read more about this image via NASA PhotoJournal.

Bottom Line: The ecliptic is the path the sun takes across our sky. It’s the Earth-sun plane, and, more or less, the plane of our solar system. Stargazing tip: Learn the whereabouts of the ecliptic in your sky. You’ll always find the sun, moon and planets on or near it.

from EarthSky http://bit.ly/2Kmtjvn

Animated depiction of Earth (the blue ball) orbiting the sun (the yellow ball), showing the projection of Earth-sun plane – the ecliptic – onto the background stars. Image via Tfr000/Wikimedia Commons.

Have you ever noticed that the sun, moon and planets all follow more or less the same path across our sky? Unless you live at or near a high Arctic or Antarctic latitude, you’ll never find the sun or moon due north, or due south, near your horizon. Instead, most of us on Earth see objects in our solar system crossing from the eastern to the western sky, as Earth spins, each day. If you get a chance to look for the bright planets when they’re all in the sky at the same time – as happens every year or so – you’ll see the visible planets trace out an easily observed line from the eastern to western horizon. It’s the same path the sun takes each day across our sky. This imaginary line, the path of the sun, is called the ecliptic.

Technically speaking, the Earth’s orbit defines the ecliptic. As viewed from space, the ecliptic is the Earth-sun plane. As viewed from Earth, the ecliptic is a great circle around our sky, formed by the intersection of Earth’s orbital plane with the imaginary celestial sphere surrounding us.

The sun travels around our sky on the great circle of the ecliptic. The moon and planets do, too, more or less. Why? It’s mainly because, long ago, before there was a solar system as we know it today, there was a vast cloud of gas and dust in space. This cloud was spinning, and, as it spun, it flattened out. Our sun formed in the center of this cloud, and the major planets and most other solar system objects formed in the flat disk surrounding the sun.

The ecliptic is defined by the plane of Earth’s orbit around the sun. The major planets in our solar system, and some asteroids, orbit more or less in this same plane. Image via Pics-about-Space.com.

Maybe you’ve noticed the green line on many of the charts in EarthSky’s Tonight pages. That green line marks the location of the ecliptic in our sky. Read more about the view June 4-6, 2019. Note that the angle of the ecliptic with respect to your horizon varies seasonally, and from place to place on Earth.

Today, we still see the major planets – and many of the minor planets aka asteroids – orbiting the sun approximately in this same plane, the plane of Earth’s orbit around the sun: the ecliptic. If we could watch the solar system from far above the Earth’s north pole, we’d see the planets, moons, asteroids, and some of the comets (but not all of them) rushing around the sun counterclockwise in this plane, like marbles rolling around a dish. Actually, the major planets are more within the dish than on it. They’re within the plane of the ecliptic, more or less. They retain the outline of the original cloud in space from which they were born, and their movement around the sun is an echo of the original spin of the cloud.

Since we’re in that plane, too – within the dish – we look into our sky to see edgewise into the plane of the solar system. And so we see these solar system objects travel along the ecliptic, the sun’s path, more or less.

Moon and planets on October 12, 2016, by Karthik Easvur in Hyderabad, India. The moon and planets trace out a line across our sky because they all orbit the sun, more or less, in a single plane. And – as seen from Earth – we look edgewise into that flat plane of the solar system.

Far beyond the cold edges of our solar system, we see the stars of our Milky Way galaxy. The stars are moving, too, but they’re so far away that they don’t seem to move over the course of a human lifespan. And so we speak of the “fixed” stars. Fixed stars on the ecliptic – or sun’s path – seemed special to the early stargazers. They identified constellations made of these stars, and used the word zodiac for the wider pathway traveled by these constellations. And so we find the sun, moon and our major planets within the constellations of the zodiac.

Now about that phrase we keep using, the phrase more or less …

The other planets don’t orbit exactly in the Earth-sun plane. Each major planet’s orbit is inclined a little bit to this plane. Some of the asteroids have orbits that are more inclined. And comets tend to have the most inclined orbits of all. Click here to see the inclinations of the major planets’ orbits.

Interestingly, Earth’s moon isn’t exactly on the ecliptic, either. Its orbit around Earth is tilted by about 5.15 degrees relative to the ecliptic. This means the moon spends most of its time above or below the ecliptic. It crosses it twice each orbit; once going upward and once downward from our point of view. We usually see the moon close to, but not exactly alongside the other solar system objects. On the other hand, the moon sometimes passes right in front of other solar system objects, in an event called an occultation.

So there are little variations. But – for all practical purposes of skywatching – you can think of the ecliptic as a line across our sky. You can think of the sun, moon and major planets of the solar system as moving along that line. One thing to remember, though. The sun’s path is high in summer and low in winter. So the location of the ecliptic in your sky shifts a bit, seasonally.

The ecliptic on June 21, 2019, and December 21, 2019. Image from Stellarium,

If the word ecliptic sounds familiar, you’re right. It’s from the same root as the word eclipse, from the Latin and Greek meaning to “fail to appear” or “to be hidden;” the moon hides the sun during an eclipse. The ecliptic got its name because the ancients saw that solar eclipses happen when the moon crosses the ecliptic during the new moon phase.

Later, astronomers gave the name node to the places where the moon crosses the ecliptic. If the moon traveled exactly on the ecliptic, and the other planets did, too, the moon would occult, or block out, all the planets and the sun every orbit. We’d have lunar and solar eclipses every month. Ho hum.

If you’re able, keep an eye on the sun, the moon and the planets for a while; a few days, a few weeks, months, years, even. You’ll begin to get a feel for the ecliptic in your sky. You’ll notice the planets, sun and moon are always on or near the ecliptic, and you can use this line across your sky to help you find your way around, making your way between the constellations and stars. You’ll notice the sun’s path – the ecliptic – higher in the sky during the summer months and lower during the winter. Eventually, you’ll be able to imagine the sun’s path in your sky, long after the sun has set.

When that happens, you’ll be able to pick out a planet from a star very quickly and easily, which is a great party trick. Mars is the red one; Saturn the yellow one; Venus the bright white one that never gets too far from the sun; Mercury the seldom-seen one; and Jupiter the very bright one (but never as bright as Venus) that often gets far from the sun.

Welcome to stargazing, friend!

View larger. | The cameras of the Voyager 1 spacecraft acquired the images to create this mosaic on February 14, 1990, as it journeyed out of the solar system. It pointed back toward the sun and took this series of pictures of our sun and several major planets, making the first-ever “portrait” of our solar system as seen from the outside. The mosaic consists of a total of 60 frames. Voyager 1 was at a distance of approximately 4 billion miles and about 32 degrees above the ecliptic plane. Read more about this image via NASA PhotoJournal.

Bottom Line: The ecliptic is the path the sun takes across our sky. It’s the Earth-sun plane, and, more or less, the plane of our solar system. Stargazing tip: Learn the whereabouts of the ecliptic in your sky. You’ll always find the sun, moon and planets on or near it.

from EarthSky http://bit.ly/2Kmtjvn

Find the Crow, Cup and Water Snake

At nightfall tonight, or any June evening, look in a general southward direction for Spica, the brightest star in the constellation Virgo the Maiden. If you live in the Southern Hemisphere, Spica appears overhead or high in your northern sky around 9 p.m. in early June. Spica is your jumping off point to three faint constellations: Corvus the Crow, Crater the Cup and Hydra the Snake.

If you’re familiar with the Big Dipper, use this signpost star formation to star-hop to Spica, as shown in the sky chart below:

Use the Big Dipper to arc to Arcturus and spike Spica. Read more.

You can use Spica to find the constellation Corvus – and alternately, use Corvus to confirm that you’ve found Spica:

Here’s another way to verify that you’re looking at Spica, the brightest star in the constellation Virgo.

Okay … got Spica? Now, as nightfall deepens into later evening, watch for a number of fainter stars to become visible. That’s when the Crow, the Cup and the Water Snake will come into view.

Sky chart of the constellation Hydra, including Corvus and the Crater via IAU.

In Greek mythology, Apollo sent the crow to fetch a cup of water. The crow, Corvus, got distracted eating figs. It was only after much delay that he finally remembered his mission. Rightly figuring that Apollo would be angry, the crow plucked a snake from the water and concocted a story about how it had attacked and delayed him.

Hydra the Water Snake with the orange star Alphard at its heart. Illustration via Deanspace.

Apollo was not fooled and angrily flung the Crow, Cup and Snake into the sky, placing the Crow and Cup on the Snake’s back.

Then the god ordered Hydra to never let the Crow drink from the Cup. As a further punishment, he ordered that the Crow could never sing again, only screech and caw.

None of these constellations has any bright stars, but Hydra holds the distinction of being the longest constellation in the heavens.

Bottom line: Use the bright star Spica to help you find the constellations Corvus the Crow, Crater the Cup, and Hydra the Water Snake.

Enjoying EarthSky so far? Sign up for our free daily newsletter today!

from EarthSky http://bit.ly/2QEOhXH

At nightfall tonight, or any June evening, look in a general southward direction for Spica, the brightest star in the constellation Virgo the Maiden. If you live in the Southern Hemisphere, Spica appears overhead or high in your northern sky around 9 p.m. in early June. Spica is your jumping off point to three faint constellations: Corvus the Crow, Crater the Cup and Hydra the Snake.

If you’re familiar with the Big Dipper, use this signpost star formation to star-hop to Spica, as shown in the sky chart below:

Use the Big Dipper to arc to Arcturus and spike Spica. Read more.

You can use Spica to find the constellation Corvus – and alternately, use Corvus to confirm that you’ve found Spica:

Here’s another way to verify that you’re looking at Spica, the brightest star in the constellation Virgo.

Okay … got Spica? Now, as nightfall deepens into later evening, watch for a number of fainter stars to become visible. That’s when the Crow, the Cup and the Water Snake will come into view.

Sky chart of the constellation Hydra, including Corvus and the Crater via IAU.

In Greek mythology, Apollo sent the crow to fetch a cup of water. The crow, Corvus, got distracted eating figs. It was only after much delay that he finally remembered his mission. Rightly figuring that Apollo would be angry, the crow plucked a snake from the water and concocted a story about how it had attacked and delayed him.

Hydra the Water Snake with the orange star Alphard at its heart. Illustration via Deanspace.

Apollo was not fooled and angrily flung the Crow, Cup and Snake into the sky, placing the Crow and Cup on the Snake’s back.

Then the god ordered Hydra to never let the Crow drink from the Cup. As a further punishment, he ordered that the Crow could never sing again, only screech and caw.

None of these constellations has any bright stars, but Hydra holds the distinction of being the longest constellation in the heavens.

Bottom line: Use the bright star Spica to help you find the constellations Corvus the Crow, Crater the Cup, and Hydra the Water Snake.

Enjoying EarthSky so far? Sign up for our free daily newsletter today!

from EarthSky http://bit.ly/2QEOhXH

Did supernovae blasts prompt humans to walk upright?

Image via Inquisitr.

A new study suggests that ancient supernovae might have induced proto-humans to walk on two legs.

According to the paper, published May 28, 2019 in the Journal of Geology, supernovae bombarded Earth with cosmic energy starting as many as 8 million years ago, with a peak some 2.6 million years ago that initiated an avalanche of electrons in our planet’s lower atmosphere.

The authors believe atmospheric ionization triggered an enormous upsurge in cloud-to-ground lightning strikes that ignited forest fires around the globe. These infernos could be one reason, the researchers say, that ancestors of homo sapiens developed bipedalism — that is, walking on two legs – to adapt in savannas that replaced torched forests in northeast Africa.

A composite image of a supernova. Image via Chandra.

Adrian Melott, professor emeritus of physics and astronomy at the University of Kansas, is lead author of the study. Melott said in a statement:

It is thought there was already some tendency for hominins to walk on two legs, even before this event. But they were mainly adapted for climbing around in trees. After this conversion to savanna, they would much more often have to walk from one tree to another across the grassland, and so they become better at walking upright. They could see over the tops of grass and watch for predators. It’s thought this conversion to savanna contributed to bipedalism as it became more and more dominant in human ancestors.

Based on a telltale layer of iron-60 deposits lining the world’s sea beds, astronomers have high confidence supernovae exploded in Earth’s immediate cosmic neighborhood — between 100 and only 50 parsecs (163 light-years) away — during the transition from the Pliocene Epoch to the Ice Age. Melott said:

We calculated the ionization of the atmosphere from cosmic rays which would come from a supernova about as far away as the iron-60 deposits indicate. It appears that this was the closest one in a much longer series. We contend it would increase the ionization of the lower atmosphere by 50-fold. Usually, you don’t get lower-atmosphere ionization because cosmic rays don’t penetrate that far, but the more energetic ones from supernovae come right down to the surface — so there would be a lot of electrons being knocked out of the atmosphere.

According to the study authors, ionization in the lower atmosphere meant an abundance of electrons would form more pathways for lightning strikes. Melott said:

The bottom mile or so of atmosphere gets affected in ways it normally never does. When high-energy cosmic rays hit atoms and molecules in the atmosphere, they knock electrons out of them — so these electrons are running around loose instead of bound to atoms. Ordinarily, in the lightning process, there’s a buildup of voltage between clouds or the clouds and the ground — but current can’t flow because not enough electrons are around to carry it. So, it has to build up high voltage before electrons start moving. Once they’re moving, electrons knock more electrons out of more atoms, and it builds to a lightning bolt. But with this ionization, that process can get started a lot more easily, so there would be a lot more lightning bolts.

Melott said the probability that this lightning spike touched off a worldwide upsurge in wildfires is supported by the discovery of carbon deposits found in soils that correspond with the timing of the cosmic-ray bombardment. He said:

The observation is that there’s a lot more charcoal and soot in the world starting a few million years ago. It’s all over the place, and nobody has any explanation for why it would have happened all over the world in different climate zones. This could be an explanation. That increase in fires is thought to have stimulated the transition from woodland to savanna in a lot of places — where you had forests, now you had mostly open grassland with shrubby things here and there. That’s thought to be related to human evolution in northeast Africa. Specifically, in the Great Rift Valley where you get all these hominin fossils.

Source: From Cosmic Explosions to Terrestrial Fires?

Bottom line: A scientist explains how a series of supernovae – peaking 2.6 million years ago – might have triggered earthly events that promoted proto-humans’ upright walking.

Via University of Kansas

from EarthSky http://bit.ly/30YCFmZ

Image via Inquisitr.

A new study suggests that ancient supernovae might have induced proto-humans to walk on two legs.

According to the paper, published May 28, 2019 in the Journal of Geology, supernovae bombarded Earth with cosmic energy starting as many as 8 million years ago, with a peak some 2.6 million years ago that initiated an avalanche of electrons in our planet’s lower atmosphere.

The authors believe atmospheric ionization triggered an enormous upsurge in cloud-to-ground lightning strikes that ignited forest fires around the globe. These infernos could be one reason, the researchers say, that ancestors of homo sapiens developed bipedalism — that is, walking on two legs – to adapt in savannas that replaced torched forests in northeast Africa.

A composite image of a supernova. Image via Chandra.

Adrian Melott, professor emeritus of physics and astronomy at the University of Kansas, is lead author of the study. Melott said in a statement:

It is thought there was already some tendency for hominins to walk on two legs, even before this event. But they were mainly adapted for climbing around in trees. After this conversion to savanna, they would much more often have to walk from one tree to another across the grassland, and so they become better at walking upright. They could see over the tops of grass and watch for predators. It’s thought this conversion to savanna contributed to bipedalism as it became more and more dominant in human ancestors.

Based on a telltale layer of iron-60 deposits lining the world’s sea beds, astronomers have high confidence supernovae exploded in Earth’s immediate cosmic neighborhood — between 100 and only 50 parsecs (163 light-years) away — during the transition from the Pliocene Epoch to the Ice Age. Melott said:

We calculated the ionization of the atmosphere from cosmic rays which would come from a supernova about as far away as the iron-60 deposits indicate. It appears that this was the closest one in a much longer series. We contend it would increase the ionization of the lower atmosphere by 50-fold. Usually, you don’t get lower-atmosphere ionization because cosmic rays don’t penetrate that far, but the more energetic ones from supernovae come right down to the surface — so there would be a lot of electrons being knocked out of the atmosphere.

According to the study authors, ionization in the lower atmosphere meant an abundance of electrons would form more pathways for lightning strikes. Melott said:

The bottom mile or so of atmosphere gets affected in ways it normally never does. When high-energy cosmic rays hit atoms and molecules in the atmosphere, they knock electrons out of them — so these electrons are running around loose instead of bound to atoms. Ordinarily, in the lightning process, there’s a buildup of voltage between clouds or the clouds and the ground — but current can’t flow because not enough electrons are around to carry it. So, it has to build up high voltage before electrons start moving. Once they’re moving, electrons knock more electrons out of more atoms, and it builds to a lightning bolt. But with this ionization, that process can get started a lot more easily, so there would be a lot more lightning bolts.

Melott said the probability that this lightning spike touched off a worldwide upsurge in wildfires is supported by the discovery of carbon deposits found in soils that correspond with the timing of the cosmic-ray bombardment. He said:

The observation is that there’s a lot more charcoal and soot in the world starting a few million years ago. It’s all over the place, and nobody has any explanation for why it would have happened all over the world in different climate zones. This could be an explanation. That increase in fires is thought to have stimulated the transition from woodland to savanna in a lot of places — where you had forests, now you had mostly open grassland with shrubby things here and there. That’s thought to be related to human evolution in northeast Africa. Specifically, in the Great Rift Valley where you get all these hominin fossils.

Source: From Cosmic Explosions to Terrestrial Fires?

Bottom line: A scientist explains how a series of supernovae – peaking 2.6 million years ago – might have triggered earthly events that promoted proto-humans’ upright walking.

Via University of Kansas

from EarthSky http://bit.ly/30YCFmZ

New moon is June 3

Youngest possible lunar crescent, with the moon’s age being exactly zero when this photo was taken — at the instant of new moon – 07:14 UTC on July 8, 2013. Image by Thierry Legault.

The next new moon falls on June 3, 2019, at 10:02 UTC; translate UTC to your time. New moons can’t be seen, or at least they can’t without special equipment and a lot of moon-watching experience. The photo at the top of this post shows the moon at the instant it became new in July 2013. When the moon is new, it’s most nearly between the Earth and sun for any particular month. There’s a new moon about once a month, because the moon takes about a month to orbit Earth. The moon is nearly between the Earth and sun. In most months, there’s no eclipse because, most of the time, the new moon passes not in front of the sun, but simply near it in our sky.

Either way – in front of the sun or just near it – on the day of new moon, the moon travels across the sky with the sun during the day, hidden in the sun’s glare.

A day or two after each month’s new moon, a slim crescent moon always becomes visible in the west after sunset. In the language of astronomy, this slim crescent is called a young moon by astronomers. When you can you expect to see the moon in the evening again? Probably around June 4, 5 or 6, when it’ll appear in the sunset direction for a brief time after sunset.

New moons, and young moons, are fascinating to many. The Farmer’s Almanac, for example, still offers information on gardening by the moon. And many cultures have holidays based on moon phases.

You might be able to see the young moon and the planet Mercury with the eye alone on June 4. But just in case, you might want to bring binoculars! Read more.

Bottom line: New moon is June 3, 2019, at 10:02 UTC; translate UTC to your time.

Read more: Young moon, Mercury, Mars on June 4 to 6

Read more: 4 keys to understanding moon phases

Read more: EarthSky’s guide to the bright planets

Help EarthSky keep going! Please donate.

from EarthSky http://bit.ly/2WkA18l

Youngest possible lunar crescent, with the moon’s age being exactly zero when this photo was taken — at the instant of new moon – 07:14 UTC on July 8, 2013. Image by Thierry Legault.

The next new moon falls on June 3, 2019, at 10:02 UTC; translate UTC to your time. New moons can’t be seen, or at least they can’t without special equipment and a lot of moon-watching experience. The photo at the top of this post shows the moon at the instant it became new in July 2013. When the moon is new, it’s most nearly between the Earth and sun for any particular month. There’s a new moon about once a month, because the moon takes about a month to orbit Earth. The moon is nearly between the Earth and sun. In most months, there’s no eclipse because, most of the time, the new moon passes not in front of the sun, but simply near it in our sky.

Either way – in front of the sun or just near it – on the day of new moon, the moon travels across the sky with the sun during the day, hidden in the sun’s glare.

A day or two after each month’s new moon, a slim crescent moon always becomes visible in the west after sunset. In the language of astronomy, this slim crescent is called a young moon by astronomers. When you can you expect to see the moon in the evening again? Probably around June 4, 5 or 6, when it’ll appear in the sunset direction for a brief time after sunset.

New moons, and young moons, are fascinating to many. The Farmer’s Almanac, for example, still offers information on gardening by the moon. And many cultures have holidays based on moon phases.

You might be able to see the young moon and the planet Mercury with the eye alone on June 4. But just in case, you might want to bring binoculars! Read more.

Bottom line: New moon is June 3, 2019, at 10:02 UTC; translate UTC to your time.

Read more: Young moon, Mercury, Mars on June 4 to 6

Read more: 4 keys to understanding moon phases

Read more: EarthSky’s guide to the bright planets

Help EarthSky keep going! Please donate.

from EarthSky http://bit.ly/2WkA18l

Alberta sky

Image via Sheryl R Garrison.

Photographer Sheryl Garrison described her image, taken Thursday afternoon (May 30, 2019) in southern Alberta, Canada as:

Crepuscular rays fueled by early season forest fires.

Alberta, Canada has been experiencing a very difficult fire season already. The satellite image, below, is from a day earlier (May 29). The entire province looks as though it is completely engulfed in smoke.

View larger. | There are 5 large areas of satellite “hot spots” that are visible in this natural-color satellite image collected by the Terra satellite on May 29, 2019. Read more. Image via NASA.

Bottom line: Photo of cloud over Alberta, Canada in fire season 2019.

from EarthSky http://bit.ly/2XldIA7

Image via Sheryl R Garrison.

Photographer Sheryl Garrison described her image, taken Thursday afternoon (May 30, 2019) in southern Alberta, Canada as:

Crepuscular rays fueled by early season forest fires.

Alberta, Canada has been experiencing a very difficult fire season already. The satellite image, below, is from a day earlier (May 29). The entire province looks as though it is completely engulfed in smoke.

View larger. | There are 5 large areas of satellite “hot spots” that are visible in this natural-color satellite image collected by the Terra satellite on May 29, 2019. Read more. Image via NASA.

Bottom line: Photo of cloud over Alberta, Canada in fire season 2019.

from EarthSky http://bit.ly/2XldIA7

Amazing captures of the moon and Venus

View larger. | Gilbert Vancell Nature Photography – an EarthSky friend on Facebook – captured this image on June 1, 2019. He caught it over the fortified city of Mdina on the island of Malta. He wrote: “Oh this was tight! I overslept my alarm after a night at the festival … I was expecting Venus to be closer, so the super zoom turned out to be too tight for this, and 35mm to wide, so I had to work with what I had and stitched 4 images at 150mm to cover the area I wanted.” Thanks, Gilbert!

View at EarthSky Community Photos. | The June 1, 2019 dawn sky – with a waning crescent moon and (to the moon’s left) the planet Venus – and with virga extending down from the clouds. Photo taken by Mike Lewinski. Those are the Sangre de Cristo mountains near Taos, New Mexico. Thanks, Mike!

View at EarthSky Community Photos. | Waning crescent moon and Venus at sunrise on June 1, as captured by Joan Mulcare in Apple Valley, California.

View at EarthSky Community Photos. | Jenney Disimon caught the moon and Venus on June 1, 2019 from Kota Kinabalu, Sabah N. Borneo. Thanks, Jenney!

View at EarthSky Community Photos. | Another beautiful shot of the moon and Venus before sunrise May 31, 2019, by Stephanie Longo. See Venus on the left, just above the darkened foothill? Stephanie caught them as viewed from Eleven Mile Reservoir, Lake George, Colorado, USA. Also notice that the lit side of the moon points right at Venus. Thank you Stephanie!

Bottom line: Photos of the waning crescent moon and Venus – late May and early June, 2019 – from members of the EarthSky community. Submit your photos to EarthSky here.

from EarthSky http://bit.ly/2EMwQj4

View larger. | Gilbert Vancell Nature Photography – an EarthSky friend on Facebook – captured this image on June 1, 2019. He caught it over the fortified city of Mdina on the island of Malta. He wrote: “Oh this was tight! I overslept my alarm after a night at the festival … I was expecting Venus to be closer, so the super zoom turned out to be too tight for this, and 35mm to wide, so I had to work with what I had and stitched 4 images at 150mm to cover the area I wanted.” Thanks, Gilbert!

View at EarthSky Community Photos. | The June 1, 2019 dawn sky – with a waning crescent moon and (to the moon’s left) the planet Venus – and with virga extending down from the clouds. Photo taken by Mike Lewinski. Those are the Sangre de Cristo mountains near Taos, New Mexico. Thanks, Mike!

View at EarthSky Community Photos. | Waning crescent moon and Venus at sunrise on June 1, as captured by Joan Mulcare in Apple Valley, California.

View at EarthSky Community Photos. | Jenney Disimon caught the moon and Venus on June 1, 2019 from Kota Kinabalu, Sabah N. Borneo. Thanks, Jenney!

View at EarthSky Community Photos. | Another beautiful shot of the moon and Venus before sunrise May 31, 2019, by Stephanie Longo. See Venus on the left, just above the darkened foothill? Stephanie caught them as viewed from Eleven Mile Reservoir, Lake George, Colorado, USA. Also notice that the lit side of the moon points right at Venus. Thank you Stephanie!

Bottom line: Photos of the waning crescent moon and Venus – late May and early June, 2019 – from members of the EarthSky community. Submit your photos to EarthSky here.

from EarthSky http://bit.ly/2EMwQj4