Use Big Dipper to find North Star

People are always asking how to find Polaris, the North Star. It’s easy! Drawing a line through the two outer stars of the bowl of the Big Dipper faithfully points to Polaris.

At one time, sailors’ livelihoods and survival depended on their lucky stars – most especially, the pointer stars of the Big Dipper. Scouts also learn to use the Big Dipper and Polaris to find the direction north.

Polaris is not the brightest star in the sky, as is commonly believed. It is a moderately bright second-magnitude star, radiant enough to be fairly easily seen in a dark sky. Unlike the other stars – which either rise in the east and set in the west, or else wheel in a circle around Polaris – the North Star appears fixed in the northern sky.

Ken Christison captured these glorious star trails around Polaris, the North Star.

If you stand facing Polaris, then, you’re facing the direction north. If you place Polaris to your back, you’re facing south. You can use Polaris to find directions only in the Northern Hemisphere, however. South of the equator, Polaris drops below the northern horizon.

At this time of year, at nightfall and early evening, the seven stars of the Big Dipper will light up your northeastern sky. The Big Dipper is not a constellation, by the way. It’s an asterism, or noticeable pattern of stars. Unlike many constellations, this famous asterism looks like its namesake. It is one of several dipper patterns on the sky’s dome.

The two outer stars in the bowl of the Big Dipper always point to Polaris, the North Star. Image by EarthSky Facebook friend Abhijit Juvekar.

The Big Dipper is part of Ursa Major or the Big Bear constellation. Some sources say the Dipper makes up the Bear’s tail and hindquarters. Many people say they can’t see the Bear, but I’ve imagined I’ve seen a bear in these stars, on very dark nights around this time of year. To me, the Big Dipper looks like it’s part of the stomach of the Bear. Still, what I’ve pictured in my mind – and what the early stargazers believed they saw – can be different. The sky is, after all, a huge Rorschach test, with its starry patterns open to a multitude of interpretations. What do you see in and around the Dipper’s stars?

Bottom line: One thing is certain. If you find the Big Dipper in the northeast on a March evening – and locate the two outermost stars in its bowl – those stars will point to Polaris! Give it a try.

EarthSky astronomy kits are perfect for beginners. Order today from the EarthSky store

Donate: Your support means the world to us

from EarthSky https://ift.tt/2HbdTZo

People are always asking how to find Polaris, the North Star. It’s easy! Drawing a line through the two outer stars of the bowl of the Big Dipper faithfully points to Polaris.

At one time, sailors’ livelihoods and survival depended on their lucky stars – most especially, the pointer stars of the Big Dipper. Scouts also learn to use the Big Dipper and Polaris to find the direction north.

Polaris is not the brightest star in the sky, as is commonly believed. It is a moderately bright second-magnitude star, radiant enough to be fairly easily seen in a dark sky. Unlike the other stars – which either rise in the east and set in the west, or else wheel in a circle around Polaris – the North Star appears fixed in the northern sky.

Ken Christison captured these glorious star trails around Polaris, the North Star.

If you stand facing Polaris, then, you’re facing the direction north. If you place Polaris to your back, you’re facing south. You can use Polaris to find directions only in the Northern Hemisphere, however. South of the equator, Polaris drops below the northern horizon.

At this time of year, at nightfall and early evening, the seven stars of the Big Dipper will light up your northeastern sky. The Big Dipper is not a constellation, by the way. It’s an asterism, or noticeable pattern of stars. Unlike many constellations, this famous asterism looks like its namesake. It is one of several dipper patterns on the sky’s dome.

The two outer stars in the bowl of the Big Dipper always point to Polaris, the North Star. Image by EarthSky Facebook friend Abhijit Juvekar.

The Big Dipper is part of Ursa Major or the Big Bear constellation. Some sources say the Dipper makes up the Bear’s tail and hindquarters. Many people say they can’t see the Bear, but I’ve imagined I’ve seen a bear in these stars, on very dark nights around this time of year. To me, the Big Dipper looks like it’s part of the stomach of the Bear. Still, what I’ve pictured in my mind – and what the early stargazers believed they saw – can be different. The sky is, after all, a huge Rorschach test, with its starry patterns open to a multitude of interpretations. What do you see in and around the Dipper’s stars?

Bottom line: One thing is certain. If you find the Big Dipper in the northeast on a March evening – and locate the two outermost stars in its bowl – those stars will point to Polaris! Give it a try.

EarthSky astronomy kits are perfect for beginners. Order today from the EarthSky store

Donate: Your support means the world to us

from EarthSky https://ift.tt/2HbdTZo

Hubble solves puzzle of Neptune mystery moon

Artist’s illustration of Neptune and its smallest known moon, Hippocamp. Image via ESA/Hubble/NASA/L. Calçada.

The origin of Neptune’s smallest known moon – Hippocamp – has been a mystery since this moon was first discovered in 2013. It orbits close to a larger Neptune moon, whose presence should have knocked Hippocamp out of orbit. That’s why astronomers have referred to it as “the moon that shouldn’t be there.” Now a new study – published February 20, 2019 in the peer-reviewed journal Nature – describes a possible solution to the mystery.

The study discusses scientists’ most recent ideas about where the moon came from, and why we still see it where we see it. Data for the study came from both the Hubble Space Telescope and the Voyager 2 spacecraft, which sped past Neptune in 1989.

Mark Showalter of the SETI Institute led the research team.

Illustration of the location of Hippocamp, along with some of the other inner moons and rings of Neptune. Image via NASA/ESA/M. Showalter (SETI Institute).

Hippocamp is very tiny, only about 20 miles (34 km) in diameter. Its orbit is very close to that of Proteus, Neptune’s second-largest moon and the outermost of the planet’s inner moons. Proteus is 260 miles (418 kilometers) in diameter.

The orbits of Hippocamp and Proteus are only 7,456 miles (12,000 km) apart, which didn’t make sense, since normally it would be expected that the much larger moon would knock the much smaller one out of orbit, or the smaller one would collide with the larger one. But, apparently, that didn’t happen with Hippocamp. As noted by Showalter:

The first thing we realised was that you wouldn’t expect to find such a tiny moon right next to Neptune’s biggest inner moon. In the distant past, given the slow migration outward of the larger moon, Proteus was once where Hippocamp is now.

Diagram of the inner moons of Neptune, including Hippocamp. Image via Nature.

So what is the explanation? The research team concluded that rather than being two moons that formed separately, Hippocamp is instead a “chip” knocked off of Proteus by an asteroid or comet billions of years ago. When Voyager 2 looked at Proteus with its cameras in 1989, it saw a large impact crater, which earthly astronomers call Pharos. If this scenario is correct, the rocky object that hit Proteus almost destroyed it, but instead, a smaller piece was broken off that became Hippocamp. According to Showalter:

In 1989, we thought the crater was the end of the story. With Hubble, now we know that a little piece of Proteus got left behind and we see it today as Hippocamp.

The orbital positions of Neptune’s inner moons, along with Triton, the planet’s largest moon. Image via NASA/ESA/A. Feild (STScI).

The entire moon system of Neptune has had a violent history – Proteus is thought to have formed from the debris left over after Neptune’s largest moon Triton was captured from the Kuiper Belt billions of years ago. If that happened, it also shattered Neptune’s other smaller moons at the time.

The other Neptune moons we see today are thought to be “second-generation” moons, which all formed from the debris of that early catastrophe. But since Hippocamp formed even later than those moons, it’s now considered to be a “third-generation” moon. As explained by Jack Lissauer of NASA’s Ames Research Center, a coauthor of the new research:

Based on estimates of comet populations, we know that other moons in the outer solar system have been hit by comets, smashed apart, and re-accreted multiple times. This pair of satellites provides a dramatic illustration that moons are sometimes broken apart by comets.

The name Hippocamp originates from a half-horse, half-fish creature from Greek mythology; all the moons of Neptune are named after Greek and Roman mythological figures of the undersea world.

Thanks to the Hubble Space Telescope and Voyager 2, the mystery of the moon Hippocamp’s origin seems to have been solved. The data also provide more insight into how chaotic the history of Neptune’s moon system has been over the course of billions of years. While some moons may be obliterated – or nearly so – others can be created.

Neptune’s moon Proteus, seen by Voyager 2 in 1989. Hippocamp is thought to be a tiny piece of Proteus that was broken off during an impact from an asteroid or comet. Image via NASA.

Bottom line: The origin of Neptune’s smallest known moon – Hippocamp – has long been a mystery, but now thanks to the Hubble Space Telescope, astronomers think it was a piece broken off a larger, nearby moon called Proteus by an asteroid or comet impact.

Source: The seventh inner moon of Neptune

Via Nature, SpaceTelescope.org and HubbleSite

from EarthSky https://ift.tt/2UcnOkZ

Artist’s illustration of Neptune and its smallest known moon, Hippocamp. Image via ESA/Hubble/NASA/L. Calçada.

The origin of Neptune’s smallest known moon – Hippocamp – has been a mystery since this moon was first discovered in 2013. It orbits close to a larger Neptune moon, whose presence should have knocked Hippocamp out of orbit. That’s why astronomers have referred to it as “the moon that shouldn’t be there.” Now a new study – published February 20, 2019 in the peer-reviewed journal Nature – describes a possible solution to the mystery.

The study discusses scientists’ most recent ideas about where the moon came from, and why we still see it where we see it. Data for the study came from both the Hubble Space Telescope and the Voyager 2 spacecraft, which sped past Neptune in 1989.

Mark Showalter of the SETI Institute led the research team.

Illustration of the location of Hippocamp, along with some of the other inner moons and rings of Neptune. Image via NASA/ESA/M. Showalter (SETI Institute).

Hippocamp is very tiny, only about 20 miles (34 km) in diameter. Its orbit is very close to that of Proteus, Neptune’s second-largest moon and the outermost of the planet’s inner moons. Proteus is 260 miles (418 kilometers) in diameter.

The orbits of Hippocamp and Proteus are only 7,456 miles (12,000 km) apart, which didn’t make sense, since normally it would be expected that the much larger moon would knock the much smaller one out of orbit, or the smaller one would collide with the larger one. But, apparently, that didn’t happen with Hippocamp. As noted by Showalter:

The first thing we realised was that you wouldn’t expect to find such a tiny moon right next to Neptune’s biggest inner moon. In the distant past, given the slow migration outward of the larger moon, Proteus was once where Hippocamp is now.

Diagram of the inner moons of Neptune, including Hippocamp. Image via Nature.

So what is the explanation? The research team concluded that rather than being two moons that formed separately, Hippocamp is instead a “chip” knocked off of Proteus by an asteroid or comet billions of years ago. When Voyager 2 looked at Proteus with its cameras in 1989, it saw a large impact crater, which earthly astronomers call Pharos. If this scenario is correct, the rocky object that hit Proteus almost destroyed it, but instead, a smaller piece was broken off that became Hippocamp. According to Showalter:

In 1989, we thought the crater was the end of the story. With Hubble, now we know that a little piece of Proteus got left behind and we see it today as Hippocamp.

The orbital positions of Neptune’s inner moons, along with Triton, the planet’s largest moon. Image via NASA/ESA/A. Feild (STScI).

The entire moon system of Neptune has had a violent history – Proteus is thought to have formed from the debris left over after Neptune’s largest moon Triton was captured from the Kuiper Belt billions of years ago. If that happened, it also shattered Neptune’s other smaller moons at the time.

The other Neptune moons we see today are thought to be “second-generation” moons, which all formed from the debris of that early catastrophe. But since Hippocamp formed even later than those moons, it’s now considered to be a “third-generation” moon. As explained by Jack Lissauer of NASA’s Ames Research Center, a coauthor of the new research:

Based on estimates of comet populations, we know that other moons in the outer solar system have been hit by comets, smashed apart, and re-accreted multiple times. This pair of satellites provides a dramatic illustration that moons are sometimes broken apart by comets.

The name Hippocamp originates from a half-horse, half-fish creature from Greek mythology; all the moons of Neptune are named after Greek and Roman mythological figures of the undersea world.

Thanks to the Hubble Space Telescope and Voyager 2, the mystery of the moon Hippocamp’s origin seems to have been solved. The data also provide more insight into how chaotic the history of Neptune’s moon system has been over the course of billions of years. While some moons may be obliterated – or nearly so – others can be created.

Neptune’s moon Proteus, seen by Voyager 2 in 1989. Hippocamp is thought to be a tiny piece of Proteus that was broken off during an impact from an asteroid or comet. Image via NASA.

Bottom line: The origin of Neptune’s smallest known moon – Hippocamp – has long been a mystery, but now thanks to the Hubble Space Telescope, astronomers think it was a piece broken off a larger, nearby moon called Proteus by an asteroid or comet impact.

Source: The seventh inner moon of Neptune

Via Nature, SpaceTelescope.org and HubbleSite

from EarthSky https://ift.tt/2UcnOkZ

See it! Photos of moon and morning planets

View at EarthSky Community Photos. | Dr Ski in Valencia, Philippines caught the moon below Saturn on March 2, 2019. “I waited for clouds to temper the moon’s glare,” he wrote.

View at EarthSky Community Photos. | A wider view of the planets on March 2, 2019, from Dr Ski in Valencia, Philippines. Thanks, Dr. Ski!

Steven A. Sweet of the Facebook page Lunar 101 Moon Book caught this image of the moon, Saturn and Venus on March 1, 2019. He’s in Mississauga, Ontario, Canada.

“Jupiter, moon, Saturn, Venus and me at -18 C,” wrote Steven A. Sweet of the Facebook page Lunar 101 Moon Book. He captured this image on the morning of February 28, 2019. Thanks, Steven!

Beautiful shot of the planets and moon on the morning of February 28 from Claire L. Shickora in Casa Grande, Arizona.

View at EarthSky Community Photos.| Moon and morning planets on March 1, 2019 from Kaliannan Shanmugasundaram in Soeng Sang Town, Thailand. See the photo above!

View at EarthSky Community Photos. | Moon and morning planets on February 27, 2019 from Kaliannan Shanmugasundaram in Soeng Sang Town, Thailand. See the photo below to see how the moon moved over the course of a few days. Thank you, Kaliannan.

View at EarthSky Community Photos. | Dennis Chabot of in Rehoboth Massachusetts – and of POSNE NightSky Astrophotography – caught the February 27, 2019 moon and Jupiter, ascending in the east before sunup, with the constellation Scorpius the Scorpion rising nearby. Thank you, Dennis!

View at EarthSky Community Photos.| Moon and Jupiter on February 27, 2019 from April Singer in New Mexico.

View at EarthSky Community Photos. | Waning moon and Jupiter on the morning of February 27, 2019, from Chuck Reinhart in Vincennes, Indiana. Thank you, Chuck.

Bottom line: Photos of the moon’s sweep past the morning planets – Venus, Saturn, Jupiter – in late February and early March 2019.

from EarthSky https://ift.tt/2NDXiP3

View at EarthSky Community Photos. | Dr Ski in Valencia, Philippines caught the moon below Saturn on March 2, 2019. “I waited for clouds to temper the moon’s glare,” he wrote.

View at EarthSky Community Photos. | A wider view of the planets on March 2, 2019, from Dr Ski in Valencia, Philippines. Thanks, Dr. Ski!

Steven A. Sweet of the Facebook page Lunar 101 Moon Book caught this image of the moon, Saturn and Venus on March 1, 2019. He’s in Mississauga, Ontario, Canada.

“Jupiter, moon, Saturn, Venus and me at -18 C,” wrote Steven A. Sweet of the Facebook page Lunar 101 Moon Book. He captured this image on the morning of February 28, 2019. Thanks, Steven!

Beautiful shot of the planets and moon on the morning of February 28 from Claire L. Shickora in Casa Grande, Arizona.

View at EarthSky Community Photos.| Moon and morning planets on March 1, 2019 from Kaliannan Shanmugasundaram in Soeng Sang Town, Thailand. See the photo above!

View at EarthSky Community Photos. | Moon and morning planets on February 27, 2019 from Kaliannan Shanmugasundaram in Soeng Sang Town, Thailand. See the photo below to see how the moon moved over the course of a few days. Thank you, Kaliannan.

View at EarthSky Community Photos. | Dennis Chabot of in Rehoboth Massachusetts – and of POSNE NightSky Astrophotography – caught the February 27, 2019 moon and Jupiter, ascending in the east before sunup, with the constellation Scorpius the Scorpion rising nearby. Thank you, Dennis!

View at EarthSky Community Photos.| Moon and Jupiter on February 27, 2019 from April Singer in New Mexico.

View at EarthSky Community Photos. | Waning moon and Jupiter on the morning of February 27, 2019, from Chuck Reinhart in Vincennes, Indiana. Thank you, Chuck.

Bottom line: Photos of the moon’s sweep past the morning planets – Venus, Saturn, Jupiter – in late February and early March 2019.

from EarthSky https://ift.tt/2NDXiP3

News digest – cancer stem cells, breast screening, liquid biopsies and vaping in teens

Breast cancer screening rate hits 10-year low

Breast cancer screening rates have sunk to the lowest in 10 years, according to the Telegraph. New figures released by the NHS show that only around 70 in 100 people invited to breast screening decided to take part.

Single round of chemo for testicular cancer may not affect fertility

A single round of chemotherapy after surgery for people with testicular cancer doesn’t affect their fertility long-term. The Sun reports the findings of this small study.

1 in 5 think cervical screening is a test for ovarian cancer

1 in 5 women mistakenly think cervical screening tests can detect ovarian cancer, according to a survey reported by ITV News.

Diet may impact response to immunotherapy

Forbes looks at new research suggesting a link between what a patient eats and their response to immunotherapy treatments. The early unpublished results, to be presented at a conference held by the American Association for Cancer Research in Atlanta in April, suggest certain people with an aggressive type of skin cancer who ate a diet high in fibre responded better to immune-boosting drugs.

Liquid biopsy research advances

TIME covers more unpublished research to be presented at the same conference in Atlanta that puts a blood test for advanced lung cancer to the test. Researchers say their test is at least as effective as a tissue sample at identifying important genetic changes in non-small cell lung cancers. It now needs to go through further testing to see if it can help doctors decide on treatment for their patients. The Observer also took a broader look at where research into cancer blood tests is heading.

Colon cancer in young more likely to be diagnosed late

Another research preview from Atlanta: the Mail Online reports an American survey looking at bowel cancer diagnosis in people under the age of 50. It found many of these patients were initially misdiagnosed, which led to finding out they had cancer later, when the disease was more advanced.

Half of children with cancer worldwide aren’t treated

Children living with cancer in parts of Asia and Africa are not receiving treatment. According to the Guardian, this means that nearly half of all children with cancer go underdiagnosed and die at home from the disease.

Major supermarkets stock high fat foods in ‘healthier choices’ section

Stores are marketing foods high in fat and sugar as ‘healthy’, reports the BBC. Visits to the top five UK supermarkets found these foods in Sainsbury’s and Morrison’s were put in the ‘healthier choices’ section on the shelves.

England’s top doctor champions junk food ad ban on London transport

The chief medical officer for England, Professor Dame Sally Davies, says the junk food advertising band on London transport is a step in the right direction. In the Independent she calls obesity a “public health crisis” and says the initiative is a chance to “save lives”.

Cancer treatment should target cancer stem cells, says scientist

Also in the Independent, a scientist talks about his work looking into cancer stem cells. He believes these specialised cancer cells are the ones that can break off from an initial tumour and make a new tumour in another part of the body. He says targeting these cells could stop tumours growing and spreading.

And finally

E-cigarettes hit headlines after new vaping figures were released by Public Health England. Reports said the number of 11-18-year-olds who vape had doubled in the last 5 years. But even though the number of teens vaping has increased, regular vaping among young people remains very low. We took to Twitter to explain the report’s findings and to provide some context behind the numbers.

Gabi

from Cancer Research UK – Science blog https://ift.tt/2tUkeRn

Breast cancer screening rate hits 10-year low

Breast cancer screening rates have sunk to the lowest in 10 years, according to the Telegraph. New figures released by the NHS show that only around 70 in 100 people invited to breast screening decided to take part.

Single round of chemo for testicular cancer may not affect fertility

A single round of chemotherapy after surgery for people with testicular cancer doesn’t affect their fertility long-term. The Sun reports the findings of this small study.

1 in 5 think cervical screening is a test for ovarian cancer

1 in 5 women mistakenly think cervical screening tests can detect ovarian cancer, according to a survey reported by ITV News.

Diet may impact response to immunotherapy

Forbes looks at new research suggesting a link between what a patient eats and their response to immunotherapy treatments. The early unpublished results, to be presented at a conference held by the American Association for Cancer Research in Atlanta in April, suggest certain people with an aggressive type of skin cancer who ate a diet high in fibre responded better to immune-boosting drugs.

Liquid biopsy research advances

TIME covers more unpublished research to be presented at the same conference in Atlanta that puts a blood test for advanced lung cancer to the test. Researchers say their test is at least as effective as a tissue sample at identifying important genetic changes in non-small cell lung cancers. It now needs to go through further testing to see if it can help doctors decide on treatment for their patients. The Observer also took a broader look at where research into cancer blood tests is heading.

Colon cancer in young more likely to be diagnosed late

Another research preview from Atlanta: the Mail Online reports an American survey looking at bowel cancer diagnosis in people under the age of 50. It found many of these patients were initially misdiagnosed, which led to finding out they had cancer later, when the disease was more advanced.

Half of children with cancer worldwide aren’t treated

Children living with cancer in parts of Asia and Africa are not receiving treatment. According to the Guardian, this means that nearly half of all children with cancer go underdiagnosed and die at home from the disease.

Major supermarkets stock high fat foods in ‘healthier choices’ section

Stores are marketing foods high in fat and sugar as ‘healthy’, reports the BBC. Visits to the top five UK supermarkets found these foods in Sainsbury’s and Morrison’s were put in the ‘healthier choices’ section on the shelves.

England’s top doctor champions junk food ad ban on London transport

The chief medical officer for England, Professor Dame Sally Davies, says the junk food advertising band on London transport is a step in the right direction. In the Independent she calls obesity a “public health crisis” and says the initiative is a chance to “save lives”.

Cancer treatment should target cancer stem cells, says scientist

Also in the Independent, a scientist talks about his work looking into cancer stem cells. He believes these specialised cancer cells are the ones that can break off from an initial tumour and make a new tumour in another part of the body. He says targeting these cells could stop tumours growing and spreading.

And finally

E-cigarettes hit headlines after new vaping figures were released by Public Health England. Reports said the number of 11-18-year-olds who vape had doubled in the last 5 years. But even though the number of teens vaping has increased, regular vaping among young people remains very low. We took to Twitter to explain the report’s findings and to provide some context behind the numbers.

Gabi

from Cancer Research UK – Science blog https://ift.tt/2tUkeRn

When and where did Earth get its oxygen?

Stromatolite in Shark Bay, Western Australia. These fossilized stromatolites are thought to be some of the most ancient forms of life on Earth and are comprised of organisms that probably contributed to the O2 scientists are inferring existed on ancient Earth (i.e., cyanobacteria). Image via Ariel Anbar, Arizona State University.

Oxygen in the form of the oxygen molecule (O2), produced by plants and vital for animals, is abundant in Earth’s atmosphere and oceans. But that hasn’t always been the case. When, and in what environments, did O2 begin to build up on Earth? A new study that looked at ancient rocks in Western Australia suggests it started happening earlier than we thought.

The O2 on Earth was relatively scarce for much of our planet’s 4.6 billion-year existence. But at some point, Earth underwent what scientists call the Great Oxidation Event or GOE for short, as ocean microbes evolved to produce O2 via photosynthesis. O2 first accumulated in Earth’s atmosphere at this time and has been present ever since. It’s been thought that this happened sometime between 2.5 and 2.3 billion years ago.

Through numerous studies in this field of research, however, evidence has emerged that there were minor amounts of O2 in small areas of Earth’s ancient shallow oceans before the GOE. The new study published February 25, 2019 in the peer-reviewed journal Nature Geoscience, has provided evidence for significant ocean oxygenation before the GOE, on a larger scale and to greater depths than previously recognized.

Stromatolite in Shark Bay, Western Australia. Image via Ariel Anbar, ASU.

For this study, the team targeted a set of 2.5 billion-year-old marine rocks called stromatolites from Western Australia known as the Mt. McRae Shale. Stromatolites are sedimentary rocks formed by the growth of layer upon layer of cyanobacteria, a single-celled microbe that gets energy through photosynthesis, releasing oxygen as a by-product. Chadlin Ostrander, of Arizona State University’s School of Earth and Space Exploration is the study lead author. He said in a statement:

These rocks were perfect for our study because they were shown previously to have been deposited during an anomalous oxygenation episode before the Great Oxidation Event.

For this research, the team dissolved samples and separated elements of interest in a the lab, then measured isotopic compositions on a mass spectrometer. Their analysis determined that the rocks could only have their chemical signatures of the rock meant that O2 needed to have been present all the way down to the sea floor 2.5 billion years ago. Read more about how the scientists did the study here.

The 2.5 billion-year-old Mt. McRae Shale from Western Australia was analyzed for thallium and molybdenum isotope compositions, revealing a pattern that indicates manganese oxide minerals were being buried over large regions of the ancient sea floor. For this burial to occur, O2 needed to have been present all the way down to the sea floor 2.5 billion-years-ago. Image via Chad Ostrander/Arizona State University

The researchers suggest that accumulation of O2 was probably not restricted to small portions of the planet’s surface ocean prior to the GOE. More likely, they say, is that O2 accumulation extended over large regions of the ocean and far into the ocean’s depths – in some of areas, even all the way down to the sea floor.

Ostrander said:

Our discovery forces us to rethink the initial oxygenation of Earth. Many lines of evidence suggest that O2 started to accumulate in Earth’s atmosphere after about 2.5 billion years ago during the GOE. However, it is now apparent that Earth’s initial oxygenation is a story rooted in the ocean. O2 probably accumulated in Earth’s oceans — to significant levels, according to our data — well before doing so in the atmosphere.

Researcher Chad Ostrander with a 2.7 billion-year-old fossilized stromatolite in Western Australia. Image via Chad Ostrander/Arizona State University

Source: Fully oxygenated water columns over continental shelves before the Great Oxidation Event

Bottom line: A new study that looked at ancient rocks in Western Australia suggests the O2 in Earth’s atmosphere started building up earlier than thought.

Via Arizona State University

from EarthSky https://ift.tt/2EEfyFk

Stromatolite in Shark Bay, Western Australia. These fossilized stromatolites are thought to be some of the most ancient forms of life on Earth and are comprised of organisms that probably contributed to the O2 scientists are inferring existed on ancient Earth (i.e., cyanobacteria). Image via Ariel Anbar, Arizona State University.

Oxygen in the form of the oxygen molecule (O2), produced by plants and vital for animals, is abundant in Earth’s atmosphere and oceans. But that hasn’t always been the case. When, and in what environments, did O2 begin to build up on Earth? A new study that looked at ancient rocks in Western Australia suggests it started happening earlier than we thought.

The O2 on Earth was relatively scarce for much of our planet’s 4.6 billion-year existence. But at some point, Earth underwent what scientists call the Great Oxidation Event or GOE for short, as ocean microbes evolved to produce O2 via photosynthesis. O2 first accumulated in Earth’s atmosphere at this time and has been present ever since. It’s been thought that this happened sometime between 2.5 and 2.3 billion years ago.

Through numerous studies in this field of research, however, evidence has emerged that there were minor amounts of O2 in small areas of Earth’s ancient shallow oceans before the GOE. The new study published February 25, 2019 in the peer-reviewed journal Nature Geoscience, has provided evidence for significant ocean oxygenation before the GOE, on a larger scale and to greater depths than previously recognized.

Stromatolite in Shark Bay, Western Australia. Image via Ariel Anbar, ASU.

For this study, the team targeted a set of 2.5 billion-year-old marine rocks called stromatolites from Western Australia known as the Mt. McRae Shale. Stromatolites are sedimentary rocks formed by the growth of layer upon layer of cyanobacteria, a single-celled microbe that gets energy through photosynthesis, releasing oxygen as a by-product. Chadlin Ostrander, of Arizona State University’s School of Earth and Space Exploration is the study lead author. He said in a statement:

These rocks were perfect for our study because they were shown previously to have been deposited during an anomalous oxygenation episode before the Great Oxidation Event.

For this research, the team dissolved samples and separated elements of interest in a the lab, then measured isotopic compositions on a mass spectrometer. Their analysis determined that the rocks could only have their chemical signatures of the rock meant that O2 needed to have been present all the way down to the sea floor 2.5 billion years ago. Read more about how the scientists did the study here.

The 2.5 billion-year-old Mt. McRae Shale from Western Australia was analyzed for thallium and molybdenum isotope compositions, revealing a pattern that indicates manganese oxide minerals were being buried over large regions of the ancient sea floor. For this burial to occur, O2 needed to have been present all the way down to the sea floor 2.5 billion-years-ago. Image via Chad Ostrander/Arizona State University

The researchers suggest that accumulation of O2 was probably not restricted to small portions of the planet’s surface ocean prior to the GOE. More likely, they say, is that O2 accumulation extended over large regions of the ocean and far into the ocean’s depths – in some of areas, even all the way down to the sea floor.

Ostrander said:

Our discovery forces us to rethink the initial oxygenation of Earth. Many lines of evidence suggest that O2 started to accumulate in Earth’s atmosphere after about 2.5 billion years ago during the GOE. However, it is now apparent that Earth’s initial oxygenation is a story rooted in the ocean. O2 probably accumulated in Earth’s oceans — to significant levels, according to our data — well before doing so in the atmosphere.

Researcher Chad Ostrander with a 2.7 billion-year-old fossilized stromatolite in Western Australia. Image via Chad Ostrander/Arizona State University

Source: Fully oxygenated water columns over continental shelves before the Great Oxidation Event

Bottom line: A new study that looked at ancient rocks in Western Australia suggests the O2 in Earth’s atmosphere started building up earlier than thought.

Via Arizona State University

from EarthSky https://ift.tt/2EEfyFk

Lunar halo over Mobius Arch

View larger. | Image via Photography of the Eternal Nomad.

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The Mobius Arch is one of the dozens of natural arches in California’s Alabama Hills, a range of hills and rock formations near the eastern slope of the Sierra Nevada.

Photography of the Eternal Nomad captured this lunar halo during the February 18-19, 2019, full moon.

Image via Wikipedia.

Bottom line: Photo of lunar halo over Mobius Arch.

from EarthSky https://ift.tt/2XxVNGD

View larger. | Image via Photography of the Eternal Nomad.

Help EarthSky keep going! Please donate what you can to our once-yearly crowd-funding campaign.

The Mobius Arch is one of the dozens of natural arches in California’s Alabama Hills, a range of hills and rock formations near the eastern slope of the Sierra Nevada.

Photography of the Eternal Nomad captured this lunar halo during the February 18-19, 2019, full moon.

Image via Wikipedia.

Bottom line: Photo of lunar halo over Mobius Arch.

from EarthSky https://ift.tt/2XxVNGD

Don’t miss moon and Venus before sunup

Before sunrise on March 2, 2019, look east before sunup to see the beautiful pairing of the moon and dazzling planet Venus. Good news. You don’t have to get up much before the sun to view these brilliant worlds. The moon and Venus are bright, the second-brightest and third-brightest sky objects, respectively, after the sun. In fact, people with exceptional eyesight might be able to pick up Venus near the moon after sunrise.

Help EarthSky keep going! Please donate what you can to our annual crowd-funding campaign.

If you arise before the dawn light becomes too overwhelming, two other planets can also be seen in the morning sky. Jupiter, the 4th-brightest celestial object, after the sun, moon and Venus, has risen much earlier and shines in your southern sky (or northern sky if you’re in the Southern Hemisphere). Saturn, the dimmest of the worlds now up before the sun, shines in between Jupiter and Venus. See the sky chart below.

It’ll even be harder to spot the thinner, paler moon lower down in the sky before sunrise March 3, 2019.

Note on the sky chart above, which is for middle latitudes in the Northern Hemisphere, that the lunar crescent is C-shaped. The lit side of the moon points in the direction of sunrise, and the moon and planets line-up pretty much in a sideways direction. That’s because the ecliptic – the pathway of the sun, moon and planets – crosses the sky at a very shallow angle on late winter and early spring mornings.

Contrast the sky chart above to the one below for Valdivia, Chile (40 degrees south latitude). The lunar crescent is closer to U-shaped, and the planets are aligned almost vertically (Jupiter is so high up that it’s actually outside the chart). That’s because the ecliptic hits the horizon almost perpendicularly on late summer and early autumn mornings. It’s now late summer for the Southern Hemisphere.

As viewed from the Southern Hemisphere, the waning crescent moon and the morning planets are found higher in the sky. Jupiter is way higher up, outside the view of the chart.

About a week from now – around March 7 or 8, 2019 – the young waxing crescent moon will make its first appearance in the evening sky. But, this time around, mid-northern latitudes will see a U-shaped evening crescent whereas the folk at Valdivia, Chile, and temperate latitudes in the Southern Hemisphere, will see a C-shaped evening crescent. That’s because the ecliptic hits the evening horizon at a steep angle in late winter and early spring, yet a shallow angle in late summer and early autumn. The charts below show the same sky from differing vantage points.

A Northern Hemisphere view of the young evening crescent with the planets Mercury and Mars from March 7-10, 2019. Read more.

The view of the young March moon from Valdivia, Chile, South America (40 degrees south latitude). Read more.

A slender waning crescent moon that appears in the east a short while before sunrise is known as an old moon. These next few mornings you might notice the dark side of the moon softly illuminated in earthshine – twice-reflected sunlight bouncing from the Earth to the moon, and then from the moon back to Earth.

This earthshine – an ashen glow on the nighttime side of the waning crescent – is sometimes poetically described as the new moon in the old moon’s arms.

View at EarthSky Community Photos. | This is earthshine, the faint illumination on the darkened portion of a crescent moon – captured on a waxing moon, on February 7, 2019 – by Radu Anghel in Bacau, Romania. Thank you, Radu.

Bottom line: On the morning of March 2, 2019, watch for the old moon and dazzling planet Venus in the east before sunup.

from EarthSky https://ift.tt/2ILHyLb

Before sunrise on March 2, 2019, look east before sunup to see the beautiful pairing of the moon and dazzling planet Venus. Good news. You don’t have to get up much before the sun to view these brilliant worlds. The moon and Venus are bright, the second-brightest and third-brightest sky objects, respectively, after the sun. In fact, people with exceptional eyesight might be able to pick up Venus near the moon after sunrise.

Help EarthSky keep going! Please donate what you can to our annual crowd-funding campaign.

If you arise before the dawn light becomes too overwhelming, two other planets can also be seen in the morning sky. Jupiter, the 4th-brightest celestial object, after the sun, moon and Venus, has risen much earlier and shines in your southern sky (or northern sky if you’re in the Southern Hemisphere). Saturn, the dimmest of the worlds now up before the sun, shines in between Jupiter and Venus. See the sky chart below.

It’ll even be harder to spot the thinner, paler moon lower down in the sky before sunrise March 3, 2019.

Note on the sky chart above, which is for middle latitudes in the Northern Hemisphere, that the lunar crescent is C-shaped. The lit side of the moon points in the direction of sunrise, and the moon and planets line-up pretty much in a sideways direction. That’s because the ecliptic – the pathway of the sun, moon and planets – crosses the sky at a very shallow angle on late winter and early spring mornings.

Contrast the sky chart above to the one below for Valdivia, Chile (40 degrees south latitude). The lunar crescent is closer to U-shaped, and the planets are aligned almost vertically (Jupiter is so high up that it’s actually outside the chart). That’s because the ecliptic hits the horizon almost perpendicularly on late summer and early autumn mornings. It’s now late summer for the Southern Hemisphere.

As viewed from the Southern Hemisphere, the waning crescent moon and the morning planets are found higher in the sky. Jupiter is way higher up, outside the view of the chart.

About a week from now – around March 7 or 8, 2019 – the young waxing crescent moon will make its first appearance in the evening sky. But, this time around, mid-northern latitudes will see a U-shaped evening crescent whereas the folk at Valdivia, Chile, and temperate latitudes in the Southern Hemisphere, will see a C-shaped evening crescent. That’s because the ecliptic hits the evening horizon at a steep angle in late winter and early spring, yet a shallow angle in late summer and early autumn. The charts below show the same sky from differing vantage points.

A Northern Hemisphere view of the young evening crescent with the planets Mercury and Mars from March 7-10, 2019. Read more.

The view of the young March moon from Valdivia, Chile, South America (40 degrees south latitude). Read more.

A slender waning crescent moon that appears in the east a short while before sunrise is known as an old moon. These next few mornings you might notice the dark side of the moon softly illuminated in earthshine – twice-reflected sunlight bouncing from the Earth to the moon, and then from the moon back to Earth.

This earthshine – an ashen glow on the nighttime side of the waning crescent – is sometimes poetically described as the new moon in the old moon’s arms.

View at EarthSky Community Photos. | This is earthshine, the faint illumination on the darkened portion of a crescent moon – captured on a waxing moon, on February 7, 2019 – by Radu Anghel in Bacau, Romania. Thank you, Radu.

Bottom line: On the morning of March 2, 2019, watch for the old moon and dazzling planet Venus in the east before sunup.

from EarthSky https://ift.tt/2ILHyLb