Earth’s 2nd largest meteorite crater much younger than thought

Image via Hwei Ling Ng/Flickr.

A new study suggests that the enormous Wolfe Creek Crater – situated on the edge of the Great Sandy Desert in northern Western Australia – is much younger than previously thought. Wolfe Creek Crater – known to Aboriginal people as Kandimalal – is the second largest crater on Earth from which meteorite fragments have been recovered (the largest is Meteor Crater in Arizona).

Geologists think Wolfe Creek Crater was formed by the impact from a meteor that was about 50 feet (15 meters) in diameter and weighed around 15,432 U.S. tons (14,000 metric tons). But exactly when the impact happened is poorly understood. Previous estimates have suggested the crater could be 300,000 years old. But a new study, published September 1, 2019, in the journal Meteoritics & Planetary Science says that the impact happened much more recently, only about 120,000 years ago.

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NASA’s Terra satellite captured this image of Wolfe Creek Crater on September 22, 2006. Image via NASA.

The team of researchers, from Australia and the U.S., calculated the new age of Wolfe Creek Crater using two dating techniques. First, the researchers collected samples from around the crater rim and applied what’s called exposure dating, which estimates the length of time that a rock has been exposed at the Earth’s surface to cosmic radiation.

They were also able to determine the age through a dating technique called optically stimulated luminescence, a dating technique used to measure how long ago sediment was last exposed to sunlight, on sand buried after the impact. Read more about how the scientists did the research here.

The researchers calculate that the maximum width of the crater is a little over half a mile (3,104 feet or 946 meters) in a northeast-southwest direction, reflecting the direction of the impact. The average diameter is 2,927 feet (892 meters). They also predict that the crater is 584 feet (178 meters) deep, and is filled by about 394 feet (120 meters) of sediment, mostly sand blown in from the desert.

Image via Wikipedia.

According to the researchers, Wolfe Creek Crater is one of seven sets of impact craters in Australia that date to within the last 120,000 years. Using this information, the researchers calculated how often these crater-producing events occur. University of Portsmouth geologist Tim Barrows led the new study. Barrows said in a statement:

Although the rate is only one large meteor hitting Australia every 17,000 years, it isn’t that simple. The craters are only found in the arid parts of Australia.

Elsewhere, the craters are destroyed by geomorphic activity like river migration or slope processes in the mountains. Since Australia has an excellent preservation record with dated craters within the arid zone, we can estimate a rate for the whole Earth. Taking into account that arid Australia is only about one per cent of the surface, the rate increases to one hitting the Earth every 180 years or so. There have been two big objects hitting the atmosphere in the last century – Tunguska in 1908 and Chelyabinsk in 2013.

This is a minimum estimate because some smaller impacts were probably covered by sand during the last ice age. The number of large objects the atmosphere is probably 20 times this number because stony meteorites are far more common but not as many survive the fiery journey through the atmosphere or effectively make craters. Our results give us a better idea of how frequent these events are.

Using the same geochronological dating techniques, the researchers recalculated the age of Arizona’s Meteor Crater. They say it is likely to be 61,000 years old, more than 10,000 years older than previously thought.

Image via Richard Arculus/Flickr.

Bottom line: A new study suggests that Earth’s second-largest impact crater, Wolfe Creek Crater in Australia, is much younger than thought.

Source: The age of Wolfe Creek meteorite crater (Kandimalal), Western Australia

Via University of Portsmouth

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

Image via Hwei Ling Ng/Flickr.

A new study suggests that the enormous Wolfe Creek Crater – situated on the edge of the Great Sandy Desert in northern Western Australia – is much younger than previously thought. Wolfe Creek Crater – known to Aboriginal people as Kandimalal – is the second largest crater on Earth from which meteorite fragments have been recovered (the largest is Meteor Crater in Arizona).

Geologists think Wolfe Creek Crater was formed by the impact from a meteor that was about 50 feet (15 meters) in diameter and weighed around 15,432 U.S. tons (14,000 metric tons). But exactly when the impact happened is poorly understood. Previous estimates have suggested the crater could be 300,000 years old. But a new study, published September 1, 2019, in the journal Meteoritics & Planetary Science says that the impact happened much more recently, only about 120,000 years ago.

EarthSky 2020 lunar calendars are available! They make great gifts. Order now. Going fast!

NASA’s Terra satellite captured this image of Wolfe Creek Crater on September 22, 2006. Image via NASA.

The team of researchers, from Australia and the U.S., calculated the new age of Wolfe Creek Crater using two dating techniques. First, the researchers collected samples from around the crater rim and applied what’s called exposure dating, which estimates the length of time that a rock has been exposed at the Earth’s surface to cosmic radiation.

They were also able to determine the age through a dating technique called optically stimulated luminescence, a dating technique used to measure how long ago sediment was last exposed to sunlight, on sand buried after the impact. Read more about how the scientists did the research here.

The researchers calculate that the maximum width of the crater is a little over half a mile (3,104 feet or 946 meters) in a northeast-southwest direction, reflecting the direction of the impact. The average diameter is 2,927 feet (892 meters). They also predict that the crater is 584 feet (178 meters) deep, and is filled by about 394 feet (120 meters) of sediment, mostly sand blown in from the desert.

Image via Wikipedia.

According to the researchers, Wolfe Creek Crater is one of seven sets of impact craters in Australia that date to within the last 120,000 years. Using this information, the researchers calculated how often these crater-producing events occur. University of Portsmouth geologist Tim Barrows led the new study. Barrows said in a statement:

Although the rate is only one large meteor hitting Australia every 17,000 years, it isn’t that simple. The craters are only found in the arid parts of Australia.

Elsewhere, the craters are destroyed by geomorphic activity like river migration or slope processes in the mountains. Since Australia has an excellent preservation record with dated craters within the arid zone, we can estimate a rate for the whole Earth. Taking into account that arid Australia is only about one per cent of the surface, the rate increases to one hitting the Earth every 180 years or so. There have been two big objects hitting the atmosphere in the last century – Tunguska in 1908 and Chelyabinsk in 2013.

This is a minimum estimate because some smaller impacts were probably covered by sand during the last ice age. The number of large objects the atmosphere is probably 20 times this number because stony meteorites are far more common but not as many survive the fiery journey through the atmosphere or effectively make craters. Our results give us a better idea of how frequent these events are.

Using the same geochronological dating techniques, the researchers recalculated the age of Arizona’s Meteor Crater. They say it is likely to be 61,000 years old, more than 10,000 years older than previously thought.

Image via Richard Arculus/Flickr.

Bottom line: A new study suggests that Earth’s second-largest impact crater, Wolfe Creek Crater in Australia, is much younger than thought.

Source: The age of Wolfe Creek meteorite crater (Kandimalal), Western Australia

Via University of Portsmouth

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

Pisces? Here’s your constellation

Pisces the Fishes illustration courtesy of Old Book Art Image gallery.

Pisces the Fishes is sometimes called the first constellation of the zodiac because the sun appears in front of this constellation at the time of the March equinox. One tropical year is usually defined as the period of time between successive March equinoxes. So – in this sense – the March equinox marks the beginning of a new year. And that is why Pisces – backdrop to the sun on the March equinox – often appears as marking the starting point of the zodiac.

As seen from mid-northern latitudes, the constellation Pisces appears in the southeast as darkness falls in November. Photo via Till Credner, AlltheSky.com.

When can I see the constellation Pisces?
In our time, the sun’s annual passage in front of the constellation Pisces is from about March 12 to April 19. Then the sun passes in front of the constellation Aries from about April 19 to May 14.

Of course, March and April are not good for seeing Pisces because this constellation is lost in the sun’s glare at that time of year. Instead, a Northern Hemisphere autumn (or Southern Hemisphere spring) – say, November – presents an opportune time for viewing Pisces in the evening sky.

As seen from across the globe, Pisces reaches its high point for the night at about 10 p.m. local standard time in early November and at about 8 p.m. in early December.

You need a dark country sky to see this fairly dim constellation swimming in what the early stargazers considered to be a watery region of the lore-laden heavens. Pisces is found to the northeast of the constellation Aquarius the Water Bearer and to the northwest of the constellation Cetus the Sea-monster.

Fortunately, Pisces can be found rather handily by referring to the signpost known as the Great Square of Pegasus, as shown on the sky chart below. Look first for the Circlet of Pisces – otherwise known as the head of the Western Fish – to the south of the Square of Pegasus. Once you’ve found the Western Fish, go on from there to catch the Eastern Fish that’s jumping upward to the east of the Square of Pegasus. The entire constellation looks like the letter V, and a very graceful and lovely V at that. The Alpha star of the constellation (though not the brightest star) is Al Risha. By the way, as seen from the northern tropics or the Southern Hemisphere, the Eastern Fish appears to be plunging downward.

First find the signpost known as the Great Square of Pegasus. That’s your jumping off spot for finding Pisces’ place in the great celestial sea. Click here for a larger chart.

Part of Pisces, the Circlet in Pisces, and the Great Square of Pegasus by Susan Jensen in Odessa, Washington. Thank you, Susan.

Pisces’ lone Messier object.
Pisces can only claim one Messier object – that is, a fuzzy object resembling a comet but really a star cluster, nebula or galaxy – within its borders. It’s Messier 74, a face-on spiral galaxy looming at an estimated 35 million light-years distant. In the month of March, when it’s technically possible – yet difficult – to see all the Messier objects in the span of one night, this Messier object in the constellation Pisces is one that is commonly missed.

Messier 74 as seen by the Hubble Space Telescope. Image via NASA

There are two reasons why Messier 74 is so hard to catch during the annual Messier Marathons in March and/or April. At that time of year, Messier 74 lurks rather low in the western sky at nightfall and quickly sinks out of view shortly thereafter. Plus, this distant galaxy has an extremely low surface brightness, so excellent seeing conditions are absolutely critical for catching Messier 74. You don’t need a large telescope as much as you need a dark, transparent sky.

But if you want to nab this faint galaxy that is Messier 74, the months around November are a grand time of year to do so. Try, possibly with averted vision, on a dark, clear moonless night.

Ruins of Palmyra, ancient Syrian city to the northeast of Damascus. Image via Wikimedia Commons

Pisces in mythology and star lore.
Greek and Roman versions of Pisces’ sky lore seemed to have come from Syria, where fish were regarded as divine. There seems to be some confusion as to whether the ancient Syrians abstained from fish altogether or only fish from the Chalos River (presently called the Queiq or Aleppo River).

The Syrian goddess of love and fertility, Atagartis, is often portrayed as half woman and half fish. She is thought to be the origin of the Greek goddess Aphrodite and the Roman goddess Venus.

According to Greek mythology, the fire-breathing monster Typhon was about to devour Aphrodite (the Roman Venus) and her son Eros (the Roman Cupid), except that they turned into fish and jumped into the Euphrates River to make a great escape. Mother and son tied themselves together with a cord to make sure they would not lose one another in the tumbling waters.

1948 night sky star map showing the constellations of the ancient Sea imagined by the ancients in this part of the sky. Look for the Western Fish swimming along the celestial equator, to the northeast of Aquarius and the northwest of Cetus. Image via etsy.com

How long is the Age of Pisces?
By some definitions, we’ll continue to live within the Age of Pisces as long the sun shines in front of this constellation on the March equinox. By the way, although the sun hasn’t appeared in front of the constellation Aries on the equinox for over 2,000 years, we still refer to the March equinox point as the First Point in Aries.

If we accept the constellation boundaries as defined by the International Astronomical Union, the Age of Pisces started in 68 B.C. and the Age of Aquarius will begin in 2597.

But there are many varied views on this, some of which you can read about in this post: When does the Age of Aquarius begin?

Bottom line: How to see the constellation Pisces. Plus sky lore and science.

Taurus? Here’s your constellation
Gemini? Here’s your constellation
Cancer? Here’s your constellation
Leo? Here’s your constellation
Virgo? Here’s your constellation
Libra? Here’s your constellation
Scorpius? Here’s your contellation
Sagittarius? Here’s your constellation
Capricornus? Here’s your constellation
Aquarius? Here’s your constellation
Pisces? Here’s your constellation
Aries? Here’s your constellation
Birthday late November to early December? Here’s your constellation

from EarthSky https://ift.tt/37Tstjn

Pisces the Fishes illustration courtesy of Old Book Art Image gallery.

Pisces the Fishes is sometimes called the first constellation of the zodiac because the sun appears in front of this constellation at the time of the March equinox. One tropical year is usually defined as the period of time between successive March equinoxes. So – in this sense – the March equinox marks the beginning of a new year. And that is why Pisces – backdrop to the sun on the March equinox – often appears as marking the starting point of the zodiac.

As seen from mid-northern latitudes, the constellation Pisces appears in the southeast as darkness falls in November. Photo via Till Credner, AlltheSky.com.

When can I see the constellation Pisces?
In our time, the sun’s annual passage in front of the constellation Pisces is from about March 12 to April 19. Then the sun passes in front of the constellation Aries from about April 19 to May 14.

Of course, March and April are not good for seeing Pisces because this constellation is lost in the sun’s glare at that time of year. Instead, a Northern Hemisphere autumn (or Southern Hemisphere spring) – say, November – presents an opportune time for viewing Pisces in the evening sky.

As seen from across the globe, Pisces reaches its high point for the night at about 10 p.m. local standard time in early November and at about 8 p.m. in early December.

You need a dark country sky to see this fairly dim constellation swimming in what the early stargazers considered to be a watery region of the lore-laden heavens. Pisces is found to the northeast of the constellation Aquarius the Water Bearer and to the northwest of the constellation Cetus the Sea-monster.

Fortunately, Pisces can be found rather handily by referring to the signpost known as the Great Square of Pegasus, as shown on the sky chart below. Look first for the Circlet of Pisces – otherwise known as the head of the Western Fish – to the south of the Square of Pegasus. Once you’ve found the Western Fish, go on from there to catch the Eastern Fish that’s jumping upward to the east of the Square of Pegasus. The entire constellation looks like the letter V, and a very graceful and lovely V at that. The Alpha star of the constellation (though not the brightest star) is Al Risha. By the way, as seen from the northern tropics or the Southern Hemisphere, the Eastern Fish appears to be plunging downward.

First find the signpost known as the Great Square of Pegasus. That’s your jumping off spot for finding Pisces’ place in the great celestial sea. Click here for a larger chart.

Part of Pisces, the Circlet in Pisces, and the Great Square of Pegasus by Susan Jensen in Odessa, Washington. Thank you, Susan.

Pisces’ lone Messier object.
Pisces can only claim one Messier object – that is, a fuzzy object resembling a comet but really a star cluster, nebula or galaxy – within its borders. It’s Messier 74, a face-on spiral galaxy looming at an estimated 35 million light-years distant. In the month of March, when it’s technically possible – yet difficult – to see all the Messier objects in the span of one night, this Messier object in the constellation Pisces is one that is commonly missed.

Messier 74 as seen by the Hubble Space Telescope. Image via NASA

There are two reasons why Messier 74 is so hard to catch during the annual Messier Marathons in March and/or April. At that time of year, Messier 74 lurks rather low in the western sky at nightfall and quickly sinks out of view shortly thereafter. Plus, this distant galaxy has an extremely low surface brightness, so excellent seeing conditions are absolutely critical for catching Messier 74. You don’t need a large telescope as much as you need a dark, transparent sky.

But if you want to nab this faint galaxy that is Messier 74, the months around November are a grand time of year to do so. Try, possibly with averted vision, on a dark, clear moonless night.

Ruins of Palmyra, ancient Syrian city to the northeast of Damascus. Image via Wikimedia Commons

Pisces in mythology and star lore.
Greek and Roman versions of Pisces’ sky lore seemed to have come from Syria, where fish were regarded as divine. There seems to be some confusion as to whether the ancient Syrians abstained from fish altogether or only fish from the Chalos River (presently called the Queiq or Aleppo River).

The Syrian goddess of love and fertility, Atagartis, is often portrayed as half woman and half fish. She is thought to be the origin of the Greek goddess Aphrodite and the Roman goddess Venus.

According to Greek mythology, the fire-breathing monster Typhon was about to devour Aphrodite (the Roman Venus) and her son Eros (the Roman Cupid), except that they turned into fish and jumped into the Euphrates River to make a great escape. Mother and son tied themselves together with a cord to make sure they would not lose one another in the tumbling waters.

1948 night sky star map showing the constellations of the ancient Sea imagined by the ancients in this part of the sky. Look for the Western Fish swimming along the celestial equator, to the northeast of Aquarius and the northwest of Cetus. Image via etsy.com

How long is the Age of Pisces?
By some definitions, we’ll continue to live within the Age of Pisces as long the sun shines in front of this constellation on the March equinox. By the way, although the sun hasn’t appeared in front of the constellation Aries on the equinox for over 2,000 years, we still refer to the March equinox point as the First Point in Aries.

If we accept the constellation boundaries as defined by the International Astronomical Union, the Age of Pisces started in 68 B.C. and the Age of Aquarius will begin in 2597.

But there are many varied views on this, some of which you can read about in this post: When does the Age of Aquarius begin?

Bottom line: How to see the constellation Pisces. Plus sky lore and science.

Taurus? Here’s your constellation
Gemini? Here’s your constellation
Cancer? Here’s your constellation
Leo? Here’s your constellation
Virgo? Here’s your constellation
Libra? Here’s your constellation
Scorpius? Here’s your contellation
Sagittarius? Here’s your constellation
Capricornus? Here’s your constellation
Aquarius? Here’s your constellation
Pisces? Here’s your constellation
Aries? Here’s your constellation
Birthday late November to early December? Here’s your constellation

from EarthSky https://ift.tt/37Tstjn

Thousands of exoplanets may orbit supermassive black holes

Artist’s concept of a black hole with its bright surrounding disk of gas and dust – and jets extending from its poles – plus many orbiting planets. Image via Kagoshima University /NAOJ.

Exoplanets – worlds orbiting other stars – are common, with billions estimated to exist in our galaxy alone. They’ve been found around all sorts of stars, including sunlike stars, red dwarfs and even pulsars. There also seem to be rogue planets, which don’t orbit any stars, but instead just wander lonely though interstellar space. And now a new study suggests there might be yet another entirely new class of planets, orbiting supermassive black holes.

The intriguing findings were announced by researchers at Kagoshima University and the National Astronomical Observatory of Japan on November 25, 2019. The new peer-reviewed study was published in The Astrophysical Journal on November 26, 2019.

It sounds like something out of science fiction, but according to the researchers, black holes that have massive disks of dust and gas surrounding them (called circumnuclear disks), just like protoplanetary disks around young stars, could produce planets – a lot of them –  just like the disks around stars. Supermassive black holes (SMBHs) could have thousands of planets orbiting them, the researchers say. Although orbiting the black hole, the planets would likely be a long way from the black hole itself, around 10 light-years. From the paper:

As a natural consequence of the elementary processes of dust growth, we discovered that a new class of planets can be formed around supermassive black holes (SMBHs). We investigated a growth path from submicron sized icy dust monomers to Earth-sized bodies outside the “snow line,” located several parsecs from SMBHs in low luminosity active galactic nuclei (AGNs).

Simulation of a supermassive black hole. The intense gravity distorts the starry background and captures light, producing a black hole silhouette. Image via NASA/Goddard Space Flight Center; background, ESA/Gaia/DPAC.

As Keiichi Wada, a professor at Kagoshima University, said in a statement:

With the right conditions, planets could be formed even in harsh environments, such as around a black hole.

Eiichiro Kokubo, a professor at the National Astronomical Observatory of Japan, said:

Our calculations show that tens of thousands of planets with 10 times the mass of the Earth could be formed around 10 light-years from a black hole. Around black holes there might exist planetary systems of astonishing scale.

The first-ever photo of a black hole, in the center of galaxy M87, taken by the Event Horizon Telescope. The black hole is a staggering 6.5 billion times more massive than the sun. The bright ring is light bent by the black hole’s gravity. Image via Event Horizon Telescope Collaboration/NASA.

The amount of dust surrounding a supermassive black hole can be enormous, as much as a hundred thousand times the mass of our sun, or about a billion times more than in a typical protoplanetary disk.

How would planets form in such an environment?

In a disk around a black hole, the dust is so dense that it blocks radiation from the black hole itself. This allows temperatures cool enough for icy dust grains to stick together and aggregate, just like they do in protoplanetary disks around stars. The researchers calculated that planets could form in several hundred million years in this manner around black holes.

Such black hole planets can’t yet be directly detected with current telescopes, but the findings open up a tentative and fascinating new field of study. From the paper:

Observing planets around SMBHs should be challenging. The standard techniques to detect exoplanets around stars, i.e., Doppler spectroscopy, transit photometry, gravitational microlensing, or direct imaging are hopeless. Photometry by a hard X-ray interferometer in space might be a possible solution, but the occultation of the accretion disk by the “planets” would be hard to distinguish from the intrinsic time variability of AGNs. The other, indirect way is detecting spectral changes in the millimeter-wavelength due to opacity variation associated with the dust growth as used in the protoplanetary disk.

It’s already known that stars can also orbit black holes, such as the ones orbiting the supermassive black hole – called Sagittarius A* – at the center of our galaxy.

X-ray image of the center of our galaxy, where the supermassive black hole Sagittarius A* resides. Image via X-ray: NASA/UMass/D.Wang et al., IR: NASA/STScI.

Black holes aren’t really holes, but objects that have gravitational pulls so strong that nothing, not even light, can escape. The “surface” of a black hole, called the event horizon, is the boundary where the velocity needed to escape exceeds the speed of light. Matter and radiation fall in, but they can’t get out.

There are two main classes of black holes. Stellar-mass black holes are three to dozens of times the sun’s mass. The supermassive black holes already discussed are 100,000 to billions of solar masses, and are located in the centers of most large galaxies, including ours. There may also be intermediate-mass black holes, about 100 to more than 10,000 solar masses. There are candidates, but they have not yet been confirmed to exist.

Bottom line: Supermassive black holes could have thousands of exoplanets orbiting them, according to a new study from Japan.

Source: Planet Formation around Supermassive Black Holes in the Active Galactic Nuclei

Via NAOJ

from EarthSky https://ift.tt/2P1p2OH

Artist’s concept of a black hole with its bright surrounding disk of gas and dust – and jets extending from its poles – plus many orbiting planets. Image via Kagoshima University /NAOJ.

Exoplanets – worlds orbiting other stars – are common, with billions estimated to exist in our galaxy alone. They’ve been found around all sorts of stars, including sunlike stars, red dwarfs and even pulsars. There also seem to be rogue planets, which don’t orbit any stars, but instead just wander lonely though interstellar space. And now a new study suggests there might be yet another entirely new class of planets, orbiting supermassive black holes.

The intriguing findings were announced by researchers at Kagoshima University and the National Astronomical Observatory of Japan on November 25, 2019. The new peer-reviewed study was published in The Astrophysical Journal on November 26, 2019.

It sounds like something out of science fiction, but according to the researchers, black holes that have massive disks of dust and gas surrounding them (called circumnuclear disks), just like protoplanetary disks around young stars, could produce planets – a lot of them –  just like the disks around stars. Supermassive black holes (SMBHs) could have thousands of planets orbiting them, the researchers say. Although orbiting the black hole, the planets would likely be a long way from the black hole itself, around 10 light-years. From the paper:

As a natural consequence of the elementary processes of dust growth, we discovered that a new class of planets can be formed around supermassive black holes (SMBHs). We investigated a growth path from submicron sized icy dust monomers to Earth-sized bodies outside the “snow line,” located several parsecs from SMBHs in low luminosity active galactic nuclei (AGNs).

Simulation of a supermassive black hole. The intense gravity distorts the starry background and captures light, producing a black hole silhouette. Image via NASA/Goddard Space Flight Center; background, ESA/Gaia/DPAC.

As Keiichi Wada, a professor at Kagoshima University, said in a statement:

With the right conditions, planets could be formed even in harsh environments, such as around a black hole.

Eiichiro Kokubo, a professor at the National Astronomical Observatory of Japan, said:

Our calculations show that tens of thousands of planets with 10 times the mass of the Earth could be formed around 10 light-years from a black hole. Around black holes there might exist planetary systems of astonishing scale.

The first-ever photo of a black hole, in the center of galaxy M87, taken by the Event Horizon Telescope. The black hole is a staggering 6.5 billion times more massive than the sun. The bright ring is light bent by the black hole’s gravity. Image via Event Horizon Telescope Collaboration/NASA.

The amount of dust surrounding a supermassive black hole can be enormous, as much as a hundred thousand times the mass of our sun, or about a billion times more than in a typical protoplanetary disk.

How would planets form in such an environment?

In a disk around a black hole, the dust is so dense that it blocks radiation from the black hole itself. This allows temperatures cool enough for icy dust grains to stick together and aggregate, just like they do in protoplanetary disks around stars. The researchers calculated that planets could form in several hundred million years in this manner around black holes.

Such black hole planets can’t yet be directly detected with current telescopes, but the findings open up a tentative and fascinating new field of study. From the paper:

Observing planets around SMBHs should be challenging. The standard techniques to detect exoplanets around stars, i.e., Doppler spectroscopy, transit photometry, gravitational microlensing, or direct imaging are hopeless. Photometry by a hard X-ray interferometer in space might be a possible solution, but the occultation of the accretion disk by the “planets” would be hard to distinguish from the intrinsic time variability of AGNs. The other, indirect way is detecting spectral changes in the millimeter-wavelength due to opacity variation associated with the dust growth as used in the protoplanetary disk.

It’s already known that stars can also orbit black holes, such as the ones orbiting the supermassive black hole – called Sagittarius A* – at the center of our galaxy.

X-ray image of the center of our galaxy, where the supermassive black hole Sagittarius A* resides. Image via X-ray: NASA/UMass/D.Wang et al., IR: NASA/STScI.

Black holes aren’t really holes, but objects that have gravitational pulls so strong that nothing, not even light, can escape. The “surface” of a black hole, called the event horizon, is the boundary where the velocity needed to escape exceeds the speed of light. Matter and radiation fall in, but they can’t get out.

There are two main classes of black holes. Stellar-mass black holes are three to dozens of times the sun’s mass. The supermassive black holes already discussed are 100,000 to billions of solar masses, and are located in the centers of most large galaxies, including ours. There may also be intermediate-mass black holes, about 100 to more than 10,000 solar masses. There are candidates, but they have not yet been confirmed to exist.

Bottom line: Supermassive black holes could have thousands of exoplanets orbiting them, according to a new study from Japan.

Source: Planet Formation around Supermassive Black Holes in the Active Galactic Nuclei

Via NAOJ

from EarthSky https://ift.tt/2P1p2OH

A better way to convert dog years to human years

On the left, a young dog (Jack), and on the right, an old dog (Snoop). Photo by Deborah Byrd.

What does it mean for us humans to age, and what does it mean for your dog to age? Turns out these two processes can be compared, some scientists are now saying, and we don’t mean in the sense of the old adage that one dog year equals seven human years. That old saying has been recognized for some time as being, quite clearly, imprecise. If it were true, then – like dogs – humans should be able to reproduce at age seven. Many of us should live to be 150. Now, however, the tools of science have been applied to the question of true length of dog years. Biologist Tina Wang led new research at Ideker Lab at the UC San Diego School of Medicine. The work has resulted in a better formula for calculating your dog’s age in human years. It stems from data on the effects of aging on dogs’ DNA. It takes breed size into account. The new formula suggests that a one-year-old dog is closer to age 30 than age seven.

We humans and our dogs (and all other living things) have DNA within our cells, coded with the genetic information, inherited from generations of those who came before us. But aging isn’t just about genetics. It’s also about a healthy or unhealthy lifestyle, for example, and about whether you contract a disease. Scientists who study aging are now speaking of the effects of these environmental factors in terms of chemical markers on our DNA. These markers – specifically methyl groups – tag our DNA. According to a emerging theory of aging, it’s the changing pattern of these tags throughout our lives that determines whether you look and seem “young for your age” or instead age prematurely. This process – the chemical modification of a person’s DNA over a lifetime – creates what aging researchers call an epigenetic clock

The researchers looked at DNA samples from 104 Labrador retrievers spanning a 16-year age range. They compared changes in their DNA samples against DNA previously collected from 320 humans between the ages of 1 and 103. They specifically looked for similarities in the methylation process between the two sets. Writing in the Washington Post on November 28, 2019, Christopher Ingraham explained that the researchers:

… found that the DNA profiles evolved in similar ways across the life span of both [dogs and humans].

UCSD’s Trey Ideker, leader of the lab that ran the study, told The Post:

If you look at the methylomes of 2-year-old Labs and you ask what are the closest human methylomes? The answer is that the best matches are in humans about 40 years old. That is just what the data show, no more, no less.

An example of the new dog aging chart – using, for the sake of comparison, movie star Tom Hanks – is below.

Read more via the Washington Post

Wang, Ideker and colleagues illustrated their findings using 2 beloved icons: a Labrador and Tom Hanks. Here’s the Washington Post’s explanation of this chart: “According to the DNA analysis, a 1-year-old Lab is equivalent to a ‘Big‘-era Hanks, while a 4-year-old mirrors the actor’s star turn in ‘The Da Vinci Code.’ By age 9, a Lab has obtained the approximate gravitas of Hanks starring as Ben Bradlee in ‘The Post.'” Chart via Wang et al. and the Washington Post.

Want the actual formula for adjusting dogs’ ages to human years? You have to multiply the natural logarithm of the dog’s age by 16 and add 31. Thus the formula is:

(human_age = 16ln(dog_age) + 31)

That looks like a complicated formula for most of us. It’s the natural logarithm of the dog’s real age, multiplied by 16, with 31 added to the total. This natural logarithm calculator might help.

Plus, you’ll find an easy-to-use dog age calculator in this article by Virginia Morell in Science on November 15, 2019.

Why study dog aging at all? As Morell points out in her article, it’s not just dogs and humans that undergo DNA methylation as they age. Mice, chimps and wolves have also been shown to have epigenetic clocks. Using dogs to study aging makes sense because dogs live in our homes, and many – like their human owners – receive once-a-year medical checkups and sometimes hospital treatments. Thus studying aging in dogs is another way of understanding how humans age.

Morell also spoke to Matt Kaeberlein, a biogerontologist at the University of Washington in Seattle, who was not involved with this research but whose lab is conducting a Dog Aging Project (open to all breeds) that include epigenetic profiles of its canine subjects. He hopes to find out why some dogs develop disease at younger ages or die earlier than normal, whereas others live long, disease-free lives. Kaeberlein told Morell:

We already knew that dogs get the same diseases and functional declines of aging that humans do, and this work provides evidence that similar molecular changes are also occurring during aging.

It’s a beautiful demonstration of the conserved features of the epigenetic age clocks shared by dogs and humans.

Read more via Science

Here’s Jack again when he was 6 or 7 months old. He grew fast! According to the new formula devised by UC San Diego aging researchers, he would have been in his late teens or early 20s when this photo was taken.

Bottom line: A team of aging researchers at the University of California San Diego performed a genetic analysis of dogs and humans and discovered that – compared with humans – dogs age faster at first. They reach the equivalent of human middle age after only a few years.

Source: Quantitative translation of dog-to-human aging by conserved remodeling of epigenetic networks

Via the Washington Post

from EarthSky https://ift.tt/34EcymS

On the left, a young dog (Jack), and on the right, an old dog (Snoop). Photo by Deborah Byrd.

What does it mean for us humans to age, and what does it mean for your dog to age? Turns out these two processes can be compared, some scientists are now saying, and we don’t mean in the sense of the old adage that one dog year equals seven human years. That old saying has been recognized for some time as being, quite clearly, imprecise. If it were true, then – like dogs – humans should be able to reproduce at age seven. Many of us should live to be 150. Now, however, the tools of science have been applied to the question of true length of dog years. Biologist Tina Wang led new research at Ideker Lab at the UC San Diego School of Medicine. The work has resulted in a better formula for calculating your dog’s age in human years. It stems from data on the effects of aging on dogs’ DNA. It takes breed size into account. The new formula suggests that a one-year-old dog is closer to age 30 than age seven.

We humans and our dogs (and all other living things) have DNA within our cells, coded with the genetic information, inherited from generations of those who came before us. But aging isn’t just about genetics. It’s also about a healthy or unhealthy lifestyle, for example, and about whether you contract a disease. Scientists who study aging are now speaking of the effects of these environmental factors in terms of chemical markers on our DNA. These markers – specifically methyl groups – tag our DNA. According to a emerging theory of aging, it’s the changing pattern of these tags throughout our lives that determines whether you look and seem “young for your age” or instead age prematurely. This process – the chemical modification of a person’s DNA over a lifetime – creates what aging researchers call an epigenetic clock

The researchers looked at DNA samples from 104 Labrador retrievers spanning a 16-year age range. They compared changes in their DNA samples against DNA previously collected from 320 humans between the ages of 1 and 103. They specifically looked for similarities in the methylation process between the two sets. Writing in the Washington Post on November 28, 2019, Christopher Ingraham explained that the researchers:

… found that the DNA profiles evolved in similar ways across the life span of both [dogs and humans].

UCSD’s Trey Ideker, leader of the lab that ran the study, told The Post:

If you look at the methylomes of 2-year-old Labs and you ask what are the closest human methylomes? The answer is that the best matches are in humans about 40 years old. That is just what the data show, no more, no less.

An example of the new dog aging chart – using, for the sake of comparison, movie star Tom Hanks – is below.

Read more via the Washington Post

Wang, Ideker and colleagues illustrated their findings using 2 beloved icons: a Labrador and Tom Hanks. Here’s the Washington Post’s explanation of this chart: “According to the DNA analysis, a 1-year-old Lab is equivalent to a ‘Big‘-era Hanks, while a 4-year-old mirrors the actor’s star turn in ‘The Da Vinci Code.’ By age 9, a Lab has obtained the approximate gravitas of Hanks starring as Ben Bradlee in ‘The Post.'” Chart via Wang et al. and the Washington Post.

Want the actual formula for adjusting dogs’ ages to human years? You have to multiply the natural logarithm of the dog’s age by 16 and add 31. Thus the formula is:

(human_age = 16ln(dog_age) + 31)

That looks like a complicated formula for most of us. It’s the natural logarithm of the dog’s real age, multiplied by 16, with 31 added to the total. This natural logarithm calculator might help.

Plus, you’ll find an easy-to-use dog age calculator in this article by Virginia Morell in Science on November 15, 2019.

Why study dog aging at all? As Morell points out in her article, it’s not just dogs and humans that undergo DNA methylation as they age. Mice, chimps and wolves have also been shown to have epigenetic clocks. Using dogs to study aging makes sense because dogs live in our homes, and many – like their human owners – receive once-a-year medical checkups and sometimes hospital treatments. Thus studying aging in dogs is another way of understanding how humans age.

Morell also spoke to Matt Kaeberlein, a biogerontologist at the University of Washington in Seattle, who was not involved with this research but whose lab is conducting a Dog Aging Project (open to all breeds) that include epigenetic profiles of its canine subjects. He hopes to find out why some dogs develop disease at younger ages or die earlier than normal, whereas others live long, disease-free lives. Kaeberlein told Morell:

We already knew that dogs get the same diseases and functional declines of aging that humans do, and this work provides evidence that similar molecular changes are also occurring during aging.

It’s a beautiful demonstration of the conserved features of the epigenetic age clocks shared by dogs and humans.

Read more via Science

Here’s Jack again when he was 6 or 7 months old. He grew fast! According to the new formula devised by UC San Diego aging researchers, he would have been in his late teens or early 20s when this photo was taken.

Bottom line: A team of aging researchers at the University of California San Diego performed a genetic analysis of dogs and humans and discovered that – compared with humans – dogs age faster at first. They reach the equivalent of human middle age after only a few years.

Source: Quantitative translation of dog-to-human aging by conserved remodeling of epigenetic networks

Via the Washington Post

from EarthSky https://ift.tt/34EcymS

Sun enters Ophiuchus on November 30

November 30, 2019. If you could see the stars in the daytime, you’d see the sun shining near the border of the constellations Ophiuchus and Scorpius on this date. The sun crosses a constellation boundary, into Ophiuchus.

EarthSky lunar calendars are cool! They make great gifts. Order now. Going fast!

You can’t see the constellation Ophiuchus when the sun lies in front of it. But, each Northern Hemisphere summer, you’ll find this constellation to the north of the bright star Antares in the constellation Scorpius.

At about this time each year, the sun passes out of Scorpius to enter Ophiuchus. Like Scorpius, Ophiuchus is a constellation of the zodiac … but unlike Scorpius, Ophiuchus is not one of the traditional twelve zodiacal constellations.

The sun will remain in front of Ophiuchus until December 18.

The ecliptic – which translates on our sky’s dome as the sun’s annual path in front of the background stars – actually passes through 13 constellations, as defined by the International Astronomical Union (IAU), although this is not commonly known. After all, when you read the horoscope in the daily newspaper or a monthly magazine, you see only 12 constellations, or signs, mentioned.

There are the 12 traditional zodiacal constellations that have been with us since ancient times. The relatively recent addition of Ophiuchus as a member of the zodiac has increased the number to 13.

Click here to find out which constellation presently backdrops the sun.

Today’s constellation boundaries were drawn out by the International Astronomical Union in the 1930s.

View larger. | Ophiuchus the Serpent Bearer.

Look at the chart carefully, and you’ll see that the border between Ophiuchus and the constellation Scorpius for the most part lies just south of, or below, the ecliptic. In ancient times, the Ophuichus-Scorpius border was likely placed to the north of, or above, the ecliptic. Had the International Astronomical Union placed its constellation boundary where the ancients might have, the sun’s annual passing in front of Scorpius would be from about November 23 till December 18, not November 23 to November 30.

Sun in zodiacal constellations 2019

Sun in zodiacal signs 2019

Bottom line: As seen from Earth, the sun passes in front of the constellation Ophiuchus each year from about November 30 to December 18.

Birthday late November to middle December? Here’s your constellation

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

from EarthSky https://ift.tt/35SrqOP

November 30, 2019. If you could see the stars in the daytime, you’d see the sun shining near the border of the constellations Ophiuchus and Scorpius on this date. The sun crosses a constellation boundary, into Ophiuchus.

EarthSky lunar calendars are cool! They make great gifts. Order now. Going fast!

You can’t see the constellation Ophiuchus when the sun lies in front of it. But, each Northern Hemisphere summer, you’ll find this constellation to the north of the bright star Antares in the constellation Scorpius.

At about this time each year, the sun passes out of Scorpius to enter Ophiuchus. Like Scorpius, Ophiuchus is a constellation of the zodiac … but unlike Scorpius, Ophiuchus is not one of the traditional twelve zodiacal constellations.

The sun will remain in front of Ophiuchus until December 18.

The ecliptic – which translates on our sky’s dome as the sun’s annual path in front of the background stars – actually passes through 13 constellations, as defined by the International Astronomical Union (IAU), although this is not commonly known. After all, when you read the horoscope in the daily newspaper or a monthly magazine, you see only 12 constellations, or signs, mentioned.

There are the 12 traditional zodiacal constellations that have been with us since ancient times. The relatively recent addition of Ophiuchus as a member of the zodiac has increased the number to 13.

Click here to find out which constellation presently backdrops the sun.

Today’s constellation boundaries were drawn out by the International Astronomical Union in the 1930s.

View larger. | Ophiuchus the Serpent Bearer.

Look at the chart carefully, and you’ll see that the border between Ophiuchus and the constellation Scorpius for the most part lies just south of, or below, the ecliptic. In ancient times, the Ophuichus-Scorpius border was likely placed to the north of, or above, the ecliptic. Had the International Astronomical Union placed its constellation boundary where the ancients might have, the sun’s annual passing in front of Scorpius would be from about November 23 till December 18, not November 23 to November 30.

Sun in zodiacal constellations 2019

Sun in zodiacal signs 2019

Bottom line: As seen from Earth, the sun passes in front of the constellation Ophiuchus each year from about November 30 to December 18.

Birthday late November to middle December? Here’s your constellation

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

from EarthSky https://ift.tt/35SrqOP

Exoplanet-tilt study boosts hope of complex life elsewhere

Artist’s illustration of an exoEarth modeled into the Alpha Centauri star system. The planet is hypothetically in the habitable zone of Alpha Centauri B, but is icy and not very hospitable for complex life. Image via Georgia Tech/Billy Quarles using Universe Sandbox.

Are we alone, or are there other intelligent civilizations in our Milky Way galaxy? In recent years, astronomers have discovered thousands of exoplanets, or worlds orbiting distant suns. Some of which are potentially habitable, and the growing consensus seems to be that we probably aren’t all by ourselves. Now a new study – announced by astronomers at the Georgia Institute of Technology (aka Georgia Tech) on November 20, 2019 – focuses on the axial tilt of Earthlike exoplanets in binary or double star system. It also boosts hope for complex life elsewhere … although not, these astronomers say, within the star system closest to our sun.

The new peer-reviewed study was published in The Astrophysical Journal on November 19.

The researchers found that if a theoretical twin of Earth were placed into a binary star system – where two stars orbit each other – up to 87% of them should tilt on their axes in a way similar to Earth’s. What’s more, the tilt should be as stable as Earth’s: not perfectly stable, but not wildly unstable, either. This result is significant, since Earth’s relatively steady tilt on its axis helps our world maintain a stable climate, needed for complex life to evolve.

Astronomer Gongjie Li at Georgia Tech said in a statement:

Multiple-star systems are common, and about 50% of stars have binary companion stars. So, this study can be applied to a large number of solar systems.

Do the results mean that all exoEarths in double star systems have steady and stable axial tilts, along with a greater potential for complex life? Unfortunately, no. We need only look as far as the next-nearest star system to find a counter-example.

Alpha Centauri A and Alpha Centauri B, the two binary stars in the Alpha Centauri system that orbit each other. An an additional faint red dwarf star, Alpha Centauri C, or Proxima Centauri, is also nearby. Image via NASA/ESA Hubble Space Telescope/Georgia Tech.

That is, the researchers modeled an example of an Earthlike world within the habitable zones of the two primary stars in the Alpha Centauri system, only 4.2 light-years away. Their statement explained:

Alpha Centauri A actually didn’t look bad, but the outlook for mild axis dynamics on an exo-Earth modeled around star B was wretched. This may douse some hopes because Alpha Centauri AB is 4 lightyears away, and a mission named Starshot with big-name backers plans to launch a space probe to examine the system, including for signs of advanced life.

So far, no actual exoplanets have yet been detected around either Alpha Centauri A or B. On the other hand, a planet is thought to orbit Proxima Centauri, a red dwarf star and technically our sun’s nearest neighbor (although no one knows for sure if Proxima is gravitationally bound to the A-B stars). This planet – called Proxima b – isn’t thought to be habitable, though. According to the new study’s principal investigator Billy Quarles, also of Georgia Tech:

We simulated what it would be like around other binaries with multiple variations of the stars’ masses, orbital qualities, and so on. The overall message was positive, but not for our nearest neighbor.

Earth’s axial tilt varies between 22.1 and 24.5 degrees every 41,000 years. This is mild enough for the planet to maintain a stable enough climate for complex life to evolve. Image via timeanddate.com.

A world’s axial tilt is important to the question of whether it can produce and sustain complex life. That’s because, for example, Earth’s axial tilt has a huge effect on our planet’s climate.

Earth’s tilt doesn’t vary much – only between 22.1 and 24.5 degrees every 41,000 years – and that fact has helped the planet maintain a stable climate over hundreds of millions of years, these astronomers say. In turn, the stable climate has allowed evolution to proceed and produce more complex lifeforms.

Earth’s moon also helps to keep variation in Earth’s axial tilt to a minimum.

Plus Earth has a stable orbit around the sun, another factor in how well our planet can maintain a climate stable enough for complex life.

If a planet has large variations in its axial tilt – as our neighboring planet Mars does for example – it’s harder for the planet’s climate to stay stable. Mars’ axis is much more variable than Earth’s, precessing between 10 degrees and 60 degrees every 2 million years. According to Quarles:

If we didn’t have the moon, Earth’s tilt could vary by about 60 degrees. We’d look maybe like Mars, and the precession of its axis appears to have contributed to a loss of atmosphere.

On Mars, this has significant effects; at 10 degrees tilt, the atmosphere condenses at the poles, creating caps that lock up a lot of the carbon dioxide atmosphere in ice. At 60 degrees, the planet could actually develop an ice belt around its equator. There is a lot of ice underground on Mars today, even near the equator, but not on the surface of the planet except at the poles.

The researchers also found that – in a double star system – for example, for Alpha Centauri B, an Earth-like planet would actually have a more stable climate without a moon. According to Quarles:

Around Alpha Centauri B, if you don’t have a moon, you have a more stable axis than if you do have a moon. If you have a moon, it’s pretty much bad news.

But even without a moon, a planet orbiting Alpha Centauri B would have a difficult time maintaining a stable climate. Quarles said:

The biggest effect you would see is differences in the climate cycles related to how elongated the orbit is. Instead of having ice ages every 100,000 years like on Earth, they may come every 1 million years, be worse, and last much longer.

Astrophysicist Billy Quarles at the telescope on Georgia Tech’s observatory. Image via Georgia Tech.

But, Quarles noted, there’s also a sweet spot in their model, albeit a small one:

Planetary orbit and spin need to precess just right relative to the binary orbit. There is this tiny sweet spot.

The potential for habitable climates on Earth-like worlds in the galaxy and universe in general however, seems quite positive, according to Li:

In general, the separation between the stars is larger in binary systems, and then the second star has less of an effect on the model of Earth. The planet’s own motion dynamics dominate other influences, and obliquity usually has a smaller variation. So, this is quite optimistic.

This is great news for the search for life elsewhere. About half the stars in our galaxy exist in double star systems, and the new results suggest that many exoEarths in those systems should have stable climate systems, suitable for complex life to evolve.

Even if not right next door.

Bottom line: A new study of exoplanet axial tilts from Georgia Tech shows that many Earth-sized worlds, even in binary star systems, could have stable enough climates for complex life to evolve.

Source: Obliquity Evolution of Circumstellar Planets in Sun-like Stellar Binaries

Via Georgia Institute of Technology

from EarthSky https://ift.tt/2DC20Zn

Artist’s illustration of an exoEarth modeled into the Alpha Centauri star system. The planet is hypothetically in the habitable zone of Alpha Centauri B, but is icy and not very hospitable for complex life. Image via Georgia Tech/Billy Quarles using Universe Sandbox.

Are we alone, or are there other intelligent civilizations in our Milky Way galaxy? In recent years, astronomers have discovered thousands of exoplanets, or worlds orbiting distant suns. Some of which are potentially habitable, and the growing consensus seems to be that we probably aren’t all by ourselves. Now a new study – announced by astronomers at the Georgia Institute of Technology (aka Georgia Tech) on November 20, 2019 – focuses on the axial tilt of Earthlike exoplanets in binary or double star system. It also boosts hope for complex life elsewhere … although not, these astronomers say, within the star system closest to our sun.

The new peer-reviewed study was published in The Astrophysical Journal on November 19.

The researchers found that if a theoretical twin of Earth were placed into a binary star system – where two stars orbit each other – up to 87% of them should tilt on their axes in a way similar to Earth’s. What’s more, the tilt should be as stable as Earth’s: not perfectly stable, but not wildly unstable, either. This result is significant, since Earth’s relatively steady tilt on its axis helps our world maintain a stable climate, needed for complex life to evolve.

Astronomer Gongjie Li at Georgia Tech said in a statement:

Multiple-star systems are common, and about 50% of stars have binary companion stars. So, this study can be applied to a large number of solar systems.

Do the results mean that all exoEarths in double star systems have steady and stable axial tilts, along with a greater potential for complex life? Unfortunately, no. We need only look as far as the next-nearest star system to find a counter-example.

Alpha Centauri A and Alpha Centauri B, the two binary stars in the Alpha Centauri system that orbit each other. An an additional faint red dwarf star, Alpha Centauri C, or Proxima Centauri, is also nearby. Image via NASA/ESA Hubble Space Telescope/Georgia Tech.

That is, the researchers modeled an example of an Earthlike world within the habitable zones of the two primary stars in the Alpha Centauri system, only 4.2 light-years away. Their statement explained:

Alpha Centauri A actually didn’t look bad, but the outlook for mild axis dynamics on an exo-Earth modeled around star B was wretched. This may douse some hopes because Alpha Centauri AB is 4 lightyears away, and a mission named Starshot with big-name backers plans to launch a space probe to examine the system, including for signs of advanced life.

So far, no actual exoplanets have yet been detected around either Alpha Centauri A or B. On the other hand, a planet is thought to orbit Proxima Centauri, a red dwarf star and technically our sun’s nearest neighbor (although no one knows for sure if Proxima is gravitationally bound to the A-B stars). This planet – called Proxima b – isn’t thought to be habitable, though. According to the new study’s principal investigator Billy Quarles, also of Georgia Tech:

We simulated what it would be like around other binaries with multiple variations of the stars’ masses, orbital qualities, and so on. The overall message was positive, but not for our nearest neighbor.

Earth’s axial tilt varies between 22.1 and 24.5 degrees every 41,000 years. This is mild enough for the planet to maintain a stable enough climate for complex life to evolve. Image via timeanddate.com.

A world’s axial tilt is important to the question of whether it can produce and sustain complex life. That’s because, for example, Earth’s axial tilt has a huge effect on our planet’s climate.

Earth’s tilt doesn’t vary much – only between 22.1 and 24.5 degrees every 41,000 years – and that fact has helped the planet maintain a stable climate over hundreds of millions of years, these astronomers say. In turn, the stable climate has allowed evolution to proceed and produce more complex lifeforms.

Earth’s moon also helps to keep variation in Earth’s axial tilt to a minimum.

Plus Earth has a stable orbit around the sun, another factor in how well our planet can maintain a climate stable enough for complex life.

If a planet has large variations in its axial tilt – as our neighboring planet Mars does for example – it’s harder for the planet’s climate to stay stable. Mars’ axis is much more variable than Earth’s, precessing between 10 degrees and 60 degrees every 2 million years. According to Quarles:

If we didn’t have the moon, Earth’s tilt could vary by about 60 degrees. We’d look maybe like Mars, and the precession of its axis appears to have contributed to a loss of atmosphere.

On Mars, this has significant effects; at 10 degrees tilt, the atmosphere condenses at the poles, creating caps that lock up a lot of the carbon dioxide atmosphere in ice. At 60 degrees, the planet could actually develop an ice belt around its equator. There is a lot of ice underground on Mars today, even near the equator, but not on the surface of the planet except at the poles.

The researchers also found that – in a double star system – for example, for Alpha Centauri B, an Earth-like planet would actually have a more stable climate without a moon. According to Quarles:

Around Alpha Centauri B, if you don’t have a moon, you have a more stable axis than if you do have a moon. If you have a moon, it’s pretty much bad news.

But even without a moon, a planet orbiting Alpha Centauri B would have a difficult time maintaining a stable climate. Quarles said:

The biggest effect you would see is differences in the climate cycles related to how elongated the orbit is. Instead of having ice ages every 100,000 years like on Earth, they may come every 1 million years, be worse, and last much longer.

Astrophysicist Billy Quarles at the telescope on Georgia Tech’s observatory. Image via Georgia Tech.

But, Quarles noted, there’s also a sweet spot in their model, albeit a small one:

Planetary orbit and spin need to precess just right relative to the binary orbit. There is this tiny sweet spot.

The potential for habitable climates on Earth-like worlds in the galaxy and universe in general however, seems quite positive, according to Li:

In general, the separation between the stars is larger in binary systems, and then the second star has less of an effect on the model of Earth. The planet’s own motion dynamics dominate other influences, and obliquity usually has a smaller variation. So, this is quite optimistic.

This is great news for the search for life elsewhere. About half the stars in our galaxy exist in double star systems, and the new results suggest that many exoEarths in those systems should have stable climate systems, suitable for complex life to evolve.

Even if not right next door.

Bottom line: A new study of exoplanet axial tilts from Georgia Tech shows that many Earth-sized worlds, even in binary star systems, could have stable enough climates for complex life to evolve.

Source: Obliquity Evolution of Circumstellar Planets in Sun-like Stellar Binaries

Via Georgia Institute of Technology

from EarthSky https://ift.tt/2DC20Zn

News digest – Heart health risks, immunotherapy trials, prostate cancer urine test and living with cancer

Immunotherapy could benefit some people with advanced prostate cancer

BBC News covers the results of a trial testing an immunotherapy drug for some men with prostate cancer that’s spread to other parts of the body and become resistant to treatment. The study involved 258 men and found that around 1 in 20 responded to pembrolizumab, with some seeing their tumours shrink or disappear completely. Experts say the next step is to identify who could benefit the most from the treatment in a larger clinical trial.

Immunotherapy drug shows promise in head and neck cancer

The same immunotherapy drug has also had promising results in trial for head and neck cancer. Around 1 in 4 patients responded positively to pembrolizumab, with their cancer either not growing or shrinking for an average of 23 months. More on this at BBC News.

Urine test to monitor prostate cancer in development

Researchers are developing a new prostate cancer test that could use urine samples collected at home to monitor some men with prostate cancer. The test aims to pick up on how aggressive the disease is, helping doctors to determine if and when treatment will be needed. But despite some bold headlines, experts were quick to point out the test was fairly early on in it’s development –  so far researchers have only studied 14 people.

Living near heavy traffic may increase risk of lung cancer

Scientists from Kings College London have linked a number of health conditions, including lung cancer, to living in areas with high levels of air pollution. According to the study, living within 50 metres of a busy road may increase the risk of lung cancer by 10%. The Guardian has the full story.

Cancer survivors at higher risk of heart problems

A new study found that 1 in 10 cancer patients die from heart related problems, rather than their original illness. Heart complications can be related to treatments such as radiotherapy to the chest and some chemotherapy drugs. But experts also pointed out that some of the cancers studied shared risk factors like obesity and smoking, which could also help explain the increased risk. BBC News reports the research in full.

NHS under pressure as hospital beds in England at record low

The number of hospital beds has fallen to its lowest ever level, reports The Guardian. A total of 17,230 beds have been cut since the last UK elections in April 2010. NHS England has said that bed cuts are leaving hospitals unable to cope.

Number of people living with cancer has increased

New estimates by the cancer charity Macmillan suggest the number of people living with cancer has climbed by 20% in the last 5 years. According to the stats, featured in the Mail Online, there are now nearly 3 million people living with cancer in the UK.

And finally

The Telegraph reports on a suggested link between brain damage and obesity in teenagers. The small study was carried out by scientists at Sao Paulo University in Brazil and looked at MRI scans of 12 to 16 year-olds. Presenting their findings at a conference, they showed that children who were obese had changes in the areas of the brain related to emotional control and feelings of reward. But it wasn’t clear if the changes caused people to become obese or were a result of being obese. More research is needed with larger groups of people to establish if there really is a link.

Scarlett Sangster is a writer for PA Media Group 

from Cancer Research UK – Science blog https://ift.tt/37S0QqT

Immunotherapy could benefit some people with advanced prostate cancer

BBC News covers the results of a trial testing an immunotherapy drug for some men with prostate cancer that’s spread to other parts of the body and become resistant to treatment. The study involved 258 men and found that around 1 in 20 responded to pembrolizumab, with some seeing their tumours shrink or disappear completely. Experts say the next step is to identify who could benefit the most from the treatment in a larger clinical trial.

Immunotherapy drug shows promise in head and neck cancer

The same immunotherapy drug has also had promising results in trial for head and neck cancer. Around 1 in 4 patients responded positively to pembrolizumab, with their cancer either not growing or shrinking for an average of 23 months. More on this at BBC News.

Urine test to monitor prostate cancer in development

Researchers are developing a new prostate cancer test that could use urine samples collected at home to monitor some men with prostate cancer. The test aims to pick up on how aggressive the disease is, helping doctors to determine if and when treatment will be needed. But despite some bold headlines, experts were quick to point out the test was fairly early on in it’s development –  so far researchers have only studied 14 people.

Living near heavy traffic may increase risk of lung cancer

Scientists from Kings College London have linked a number of health conditions, including lung cancer, to living in areas with high levels of air pollution. According to the study, living within 50 metres of a busy road may increase the risk of lung cancer by 10%. The Guardian has the full story.

Cancer survivors at higher risk of heart problems

A new study found that 1 in 10 cancer patients die from heart related problems, rather than their original illness. Heart complications can be related to treatments such as radiotherapy to the chest and some chemotherapy drugs. But experts also pointed out that some of the cancers studied shared risk factors like obesity and smoking, which could also help explain the increased risk. BBC News reports the research in full.

NHS under pressure as hospital beds in England at record low

The number of hospital beds has fallen to its lowest ever level, reports The Guardian. A total of 17,230 beds have been cut since the last UK elections in April 2010. NHS England has said that bed cuts are leaving hospitals unable to cope.

Number of people living with cancer has increased

New estimates by the cancer charity Macmillan suggest the number of people living with cancer has climbed by 20% in the last 5 years. According to the stats, featured in the Mail Online, there are now nearly 3 million people living with cancer in the UK.

And finally

The Telegraph reports on a suggested link between brain damage and obesity in teenagers. The small study was carried out by scientists at Sao Paulo University in Brazil and looked at MRI scans of 12 to 16 year-olds. Presenting their findings at a conference, they showed that children who were obese had changes in the areas of the brain related to emotional control and feelings of reward. But it wasn’t clear if the changes caused people to become obese or were a result of being obese. More research is needed with larger groups of people to establish if there really is a link.

Scarlett Sangster is a writer for PA Media Group 

from Cancer Research UK – Science blog https://ift.tt/37S0QqT