History – astroengine.com

Is Betelgeuse About to Blow? Maybe… Maybe Not

The famous supergiant on Orion’s shoulder has rapidly dimmed, stoking excitement that a supernova may be in the offing.

Artist’s impression of the tortured, bubbling photosphere of a dying Betelgeuse. [ESO/L. Calçada]

Do you hear that ticking? Doesn’t it sound like a stellar timer is counting down to the inevitable demise of a massive star? While the excitement may be the amplified construct of social media predictions of the death of Betelgeuse, our stellar neighbor really is close to going supernova.

“Close”, however, is relative. It could be as “human close” as blowing up any minute now… to “galactic close” as blowing up in a hundred thousand years, maybe more.

So, what’s all the fuss about? In a nutshell, the brightest star in the famous constellation of Orion is bright no more. In the past few weeks, Betelgeuse has dimmed noticeably, stoking predictions that it could be about to spectacularly erupt at any time, becoming as bright as a full Moon and casting its own shadows at night.

While this may sound ominous, a Betelgeuse supernova poses no threat to life on Earth. It’s located a safe 600 light-years away, so if it did explode, we’d be treated to a historic cosmic firework display and not doomsday. Any energetic particles spewing from the explosion may reach the solar system in 100,000 years, but would have a minimal impact; the heliosphere (our Sun’s extended magnetic “bubble” that encompasses all the planets) would be more than powerful enough to deflect the tenuous gases.

The constellation of Orion, with the ruddy Betelgeuse in the upper left-hand corner on Orion’s “shoulder.” [Photo by **Frank Cone** from **Pexels**]

There has always been excitement over Betelgeuse and its explosive potential. It’s a massive star, with a mass 12-times that of our Sun, which has reached the end of its life. But with a lifespan of only eight million years or so, it may sound odd that it’s dying of old age. As a comparison, our Sun—an “average” yellow dwarf star—sounds geriatric in comparison; it’s approximately five billion years old. But the strange physics of stellar evolution dictates that the more massive the star, the shorter its lifespan. Betelgeuse is on borrowed time, whereas our Sun is only middle-aged. In other words, Betelgeuse has lived fast and it will die young.

As a star that’s about to die, Betelgeuse is experiencing the final throes of violent processes that signify the conclusion of stellar evolution—a phase that sees a massive star puff up into a red supergiant. In the case of Betelgeuse, while it is 12-times more massive than our Sun, it has expanded into a grotesque, bubbling mess of superheated plasma, puffed up to nearly 1,000-times wider than our Sun. If Betelgeuse were transplanted into the middle of our solar system, it would swallow all the planets out to Saturn. Yes, even Jupiter would be ingested.

A precision observation of Betelgeuse’s asymmetric photosphere, highlighting bright spots and a non-spherical shape, as captured by the Atacama Large Millimeter/submillimeter Array (ALMA).

After guzzling all of its hydrogen fuel long ago, it’s now fusing heavier elements inside its tortured interior to the point where iron is being created. For any massive star, the fusion of iron is the death knell; energy is being absorbed, and soon, its immense gravity will cause the whole mess to collapse, generating an almighty shockwave that will, ultimately, rip Betelgeuse apart as a supernova.

As reported by astronomers before Christmas, the observed dimming could be interpreted as a precursor to the anticipated supernova, and for good reason. But Betelgeuse is known to regularly vary in brightness, so astronomers suspect that, while this is an unprecedented dimming event, the famous star will soon return to its “regular” brightness once more, reclaiming its rank as ninth brightest star in the sky.

In short, don’t place any serious money on Betelgeuse exploding soon. While there is a tiny chance that it might have already exploded, the light from the supernova currently galloping across the 600 light-year interstellar divide between us and Betelgeuse, it’s way more likely that it’s just Betelgeuse being Betelgeuse and keeping variable star astronomers on their toes.

That’s not to say the dimming event isn’t exciting, on the contrary. Seeing a prominent star in the night sky fade with your own eyes is something to behold, so when you get clear skies, look for Orion and ponder The Hunter’s missing shoulder.

Oldest Earth Rock Found In Lunar Exile

When our young planet was taking a beating by massive impacts, bits were ejected into space—and some ended up on the moon.

An artist’s impression of what our planet probably looked like over 4 billion years ago, during the violent Hadean epoch [Simone Marchi (SwRI), SSERVI, NASA]

This is an interesting thought: When Apollo astronauts were busy exploring the lunar surface, it wasn’t just moon rocks that were crunching beneath their moon boots—bits of Earth were there too. But how did Earth stuff get mixed-in with moon stuff?

According to a new study published in the journal Earth and Planetary Science Letters, this question may be a controversial one, but it’s not without some compelling evidence.

During the Apollo 14 moon landing in February 1971, when NASA astronauts Alan Shepard and Ed Mitchell were exploring the Fra Mauro Highlands, they scooped up some moon rocks and returned them to Earth for study. Fast-forward 48 years and an international group of researchers think that a 2 gram shard of rock in one of their scoops has terrestrial origins. That is a cool find in itself, but this particular sample is ancient, and possibly the oldest sample of Earth rock ever found, heralding from a time when the Earth was a very different place.

Between 4 and 4.6 billion years ago, our planet was a mess. Still in the process of forming, it was getting pummeled by an incessant barrage of asteroids and comets. Many parts of the Earth’s surface would have been molten, all of it would have been cratered, and none of the continents or oceans that we are familiar with today would have been present (see the image at the top of this page for an imagining of what it may have looked like). This was the Hadean epoch — named after the Greek god of the underworld, Hades — and it would have been a hellish time.

Apollo 14’s Ed Mitchell using a map during an EVA [NASA]

With all these impacts, large and small, it seems logical to think that a few of these impacts would have been large enough to launch a sizable quantity of debris into space. Back then, the moon orbited Earth much closer than it does now — four times closer in fact (which is a cool thought; the moon would have loomed four times larger in Hadean skies than it does now). As the moon was closer, there would have been higher odds of the terrestrial collision debris to come crashing down on the lunar surface. And this was the beginning of the epic journey of the 2 gram shard of rock that was returned to Earth and now lives in a lab.

The international team of researchers are associated with the Center for Lunar Science and Exploration, a part of NASA’s Solar System Exploration Research Virtual Institute, and they carried out a new analysis technique to search for Earth rocks in the Apollo moon samples. In one of the samples was a piece that is composed of quartz, feldspar, and zircon. These minerals are all common on Earth, but not on the lunar surface. Their interest was piqued. Further chemical analysis of the sample revealed how the rock formed: it crystallized in an oxidized atmosphere at temperatures more akin to Earth’s at the time. Moon rock typically crystallized at much higher temperatures devoid of an oxygen-rich atmosphere. The implication is clear: this particular sample didn’t form on the moon, it formed on Hadean Earth. But its journey from the Earth to the moon and into an Apollo astronaut’s sample scoop is quite the epic story.

A sample of moon rock collected by Apollo 14 astronauts [NASA]

Through the chemical analysis on the sample, a surprising amount of detail about the hows and whens could be deduced. First, after considering the mineral components of the sample, the rock must have formed around 20 kilometers under the surface, in young Earth’s crust, approximately 4.1 billion years ago. At the time, it wasn’t uncommon for massive impacts to excavate craters thousands of kilometers wide. These impact events would have easily have reached 20 kilometers deep, blasting some Earth stuff into space. The 2-gram sample was likely part of a bigger chunk that eventually collided with the moon, creating its own lunar crater, where it remained, in relative peace for a couple of hundred million years. Then, around 3.9 billion years ago, another lunar impact pummeled the sample, partially melting it, burying it deeper under the moon’s surface.

This sample holds this incredible record of geological history of a time when massive impacts were very common, when planets were accreting mass and life was just beginning to emerge on an embryonic Earth. After that lunar impact, the sample remained buried in moon rock for a few billion years.

Then, 26 million years ago, a comparatively small meteoroid slammed into the moon to create the 340-meter wide Cone Crater. The 2-gram sample was once again kicked onto the moon’s surface where it was randomly scooped by Shepard or Mitchell in 1971. The photograph below shows the boulders at the rim of Cone Crater where the sample was collected:

A photo taken on the Apollo 14 mission in the Fra Mauro highlands of the moon showing a cluster of boulders on the rim of Cone Crater during EVA-2 [NASA]

Although it may be logical to assume that ancient rocky debris from Earth likely ended up on the moon’s surface, it’s phenomenal that a tiny piece of Hadean Earth was discovered in an Apollo 14 sample. This could be an indicator as to how common it is; Earth rock preserved for billions of years on a world with no weather or tectonic processes continually erasing signs of the geological past, helping us better understand how our planet evolved.

Spinning Comet Slams its Brakes as It Makes Earth Flyby

comet-spin — Images of Comet 41P/Tuttle-Giacobini-Kresak’s jets as observed by the Discovery Channel Telescope on March 19, 2017 (Schleicher/Lowell Observatory)

Although comets are static lumps of ancient ice for most of their lives, their personalities can rapidly change with a little heat from the sun. Now, astronomers have witnessed just how dynamic comets can be, seeing one dramatically slow its rate of rotation to the point where it may even reverse its spin.

Comets are the leftover detritus of planetary formation that were sprinkled around our sun 4.6 billion years ago. These primordial icy remains collected in the outermost reaches of the solar system and that’s where they stay until they get knocked off their gravitational perches to begin an interplanetary roller coaster ride. Some are unlucky and end up diving straight to a fiery, solar death. But others set up in stable orbits, making regular passes through the inner solar system, dazzling observers with their beautiful tails formed through heating by the sun.

One mile-wide short-period comet is called 41P/Tuttle-Giacobini-Kresak and it’s a slippery celestial object. First discovered in 1858 by U.S. astronomer Horace Parnell Tuttle, it disappeared soon after. But in 1907, French astronomer Michael Giacobini “rediscovered” the comet, only for it to disappear once again. Then, in 1951, Slovak astronomer Ľubor Kresák made the final “discovery” and now astronomers know exactly where to find it and when it will turn up in our night skies.

Its name, Tuttle-Giacobini-Kresak, reflects the wonderful 100-year discovery and rediscovery history of astronomy’s quest to keep tabs on the comet’s whereabouts.

comet-spin-2 — Comet 41P/Tuttle-Giacobini-Kresak as observed on March 22, 2017 (Kees Scherer/Knight Observatory, Tomar)

Now, 41P is the focus of an interesting cometary discovery. Taking 5.4 years to complete an orbit around the sun, 41P came within 13-million miles to Earth earlier this year, the closest it has come to our planet since it was first discovered by Tuttle. So, astronomers at Lowell Observatory, near Flagstaff, Ariz., used the 4.3-meter Discovery Channel Telescope near Happy Jack, the 1.1-meter Hall telescope and the 0.9-meter Robotic telescope on Anderson Mesa, to zoom-in on the interplanetary vagabond to measure its rotational speed.

Comets can be unpredictable beasts. Composed of rock and icy volatiles, when they are slowly heated by the sun as they approach perihelion (the closest point in their orbit to the sun), these ices sublimate (i.e. turn from ice to vapor without melting into a liquid), blasting gas and dust into space.

Over time, these jets are known to have a gradual effect the comet’s trajectory and rotation, but, over an astonishing observation run, Lowell astronomers saw a dramatic change in this comet’s spin. Over a short six-week period, the comet’s rate of rotation slowed from one rotation every 24 hours to once every 48 hours — its rate of rotation had halved. This is the most dramatic change in comet rotation speed ever recorded — and erupting jets from the comet’s surface are what slammed on the brakes.

This was confirmed by observing cyanogen gas, a common molecule found on comets that is composed of one carbon atom and one nitrogen atom, being ejected into space as the comet was being heated by sunlight.

“While we expected to observe cyanogen jets and be able to determine the rotation period, we did not anticipate detecting a change in the rotation period in such a short time interval,” said Lowell astronomer David Schleicher, who led the project, in a statement. “It turned out to be the largest change in the rotational period ever measured, more than a factor of ten greater than found in any other comet.”

For this rapid slowdown to occur, the researchers think that 41P must have a very elongated shape and be of very low density. In this scenario, if the jets are located near the end of its length, enough torque could be applied to cause the slowdown. If this continues, the researchers predict that the direction of rotation may even reverse.

“If future observations can accurately measure the dimensions of the nucleus, then the observed rotation period change would set limits on the comet’s density and internal strength,” added collaborator Matthew Knight. “Such detailed knowledge of a comet is usually only obtained by a dedicated spacecraft mission like the recently completed Rosetta mission to comet 67P/Churyumov-Gerasimenko.”

In 1839, The Moon Looked Like This

The first photograph of the Moon (John W. Draper)

This is the first ever photograph taken of the Moon. The first. 170 years ago!

I was directed to the image by Twitter friend LouisS and I felt compelled to post it on Astroengine.com. Much like the 1911 Martian canal post last month, this serves as a reminder about the heritage of modern astronomy that dates back not decades, but centuries.

The 1839 photograph was taken by British ex-pat John William, a chemistry professor in the New York University, using a silver platinum plate.

For more, check out “One Photo, One Story” »

In 1911, Martians Were Building Canals

Martians Build Two Immense Canals In Two Years

On August 27th, 1911 the New York Times Sunday magazine ran an article entitled “Martians Build Two Immense Canals In Two Years”. Astronomer Percival Lowell had been studying the Red Planet and sketched what he saw, in this case, a growing complex of apparent canals on the Martian surface. There was even a nice little story that went along with this canal-building alien civilization theory. Lowell said, “The whole thing is wonderfully clear-cut,” that the Martian civilization was dying and they were building canals to reach the water ice in the Martian poles.

It turns out he was right about the water ice, but there’s no trace of this canal-building race on Mars… in fact there’s little trace of anything biological on the Red Planet. So apart from a few historic anecdotes, there’s still no life on Mars. The search continues.

Canals a thousand miles long and twenty miles wide are simply beyond our comprehension. Even though we are aware of the fact that … a rock which here weighs one hundred pounds would there only weigh thirty-eight pounds, engineering operations being in consequence less arduous than here, yet we can scarcely imagine the inhabitants of Mars capable of accomplishing this Herculean task within the short interval of two years. — Excerpt from the 1911 New York Times article.

Source: The Futility Closet (an awesome site)