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Posts Tagged ‘Astronomy

Some Hurricane

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Specifically it’s a hurricane on the planet Jupiter.

As space and science writer Robert Zimmerman notes:

I don’t have a scale, but I would guess that this storm is at least a thousand miles across. The depth is harder to measure, but we looking down into a deep whirlpool for sure.

Written by Tom Hunter

April 19, 2022 at 11:07 am

Posted in Science, Space

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Astronomy’s $10 billion Christmas Present

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Although it’s still in the process of unwrapping itself.

A few hours ago, on America’s Christmas Morning, the James Webb Space Telescope was launched by a European Space Agency (ESA) rocket, an Ariane 5, from the ESA site in French Guiana. About half and hour later it detached from the upper stage, as shown in the video below.

Rocket launches are always fairly tense, but at maximum when you’ve got a one-of-a-kind bird like this. The original plan had the telescope being launched by 2007 and costing a billion dollars, but for once I won’t throw shade at NASA about these factors because this telescope simply cannot be allowed to fail as it will be stationed about one million miles from Earth and therefore unfixable if anything goes wrong.

By contrast the Hubble Space Telescope orbits Earth about 300 miles up and was designed to be serviced by the Space Shuttles. A good thing too as when it was first launched in 1990 its images were blurred and NASA was horrified to find that its giant mirror had been improperly polished. A problem that basic in the very heart of the machine seemed like a show-stopper, but they finally fixed it in 1993 by fitting it with the equivalent of reading glasses.

It has since become one of the greatest science machines of all time, but astronomers were already planning its successor, built to see the first stars and galaxies that emerged from dust and gas of the early universe, only a few millions of years after the Big Bang. The Hubble can see back to within a billion years of that event. As a result the Webb telescope is sometimes fondly referred to by astronomers as the ‘First Light machine’.

Knowing that Hubble might not last more than twenty years and guessing that Webb would take a long time (although they never imagined it would be this long, and Hubble is still working – just) work on Webb began even before Hubble was launched – and given how Webb had to work, a repeat of the Hubble problem was not acceptable; the machine “is not allowed to fail”. As a result much of the last decade has been spent simply testing the hell out of it:

[Tests] involved lowering the telescope’s temperature to the minus 390 degrees Fahrenheit (minus 217 degrees Celsius) in which it will operate, and in a vacuum similar to that of space.

“The cryo-vacuum tests for Webb were long and gruelling,” [Project scientist] Kimble said. “It would take weeks just to cool everything down safely and then warm up again safely at the end of the test. And in the middle, when you are cold and stable, that’s when you do your detailed testing.”

And there’s a lot that can still go wrong. It has a lot of moving parts that must work to enable it to unfold in space like a giant origami sculpture:

Perhaps the most nerve-wracking move will be the unfurling of the sunshield, which is scheduled to occur in the first week after launch. The sunshield system has 140 release mechanisms, 70 hinge assemblies, 400 pulleys, 90 cables and eight deployment motors, all of which need to perform correctly to get the five thin membranes extended

The mirror consists of 18 hexagonal segments, each of which is made of beryllium and coated with a thin layer of gold.

That second link covers the engineering challenges and has a video of how it’s all supposed to unfold. The sun shade has five layers, spaced apart for maximum thermal cooling to allow the telescope instruments to be as cold as possible, which they have to be to detect faint infrared light from the oldest objects in the universe. That’s also the reason it has to be stationed so far from Earth. Hubble has IR detectors now, but was never designed for the job and so is too warm itself and too close to our warm planet, to be able to see the faintest (and oldest) objects in the sky:

[Webb] will orbit the sun, while simultaneously making small circles around the so-called Lagrange point 2 (L2)… At L2, the gravitational pulls of the sun and of Earth keep the spacecraft aligned with the two big bodies. 

It will take Webb about a month to fly to that point, unfolding all the way. Since they’re made of metal the mirror’s segments can actually be warped slightly by small electric motors mounted behind each one; all part of the process of turning those 18 mirrors into one mirror 6m wide.

If all goes according to plan, the telescope will detect cosmic objects 10 billion times fainter than the dimmest star you can see in the night sky without a telescope. That’s 10 to 100 times fainter than anything Hubble can pick up, NASA officials said. And Webb’s vision will be so sharp that it can see details the size of a penny from 24 miles (40 km) away, they added.

Fingers crossed but so far it’s all good. Check out those two links, Engineering Webb and Launching Webb for more details and videos about how it works and what it will do.

Written by Tom Hunter

December 26, 2021 at 2:07 pm

Posted in Aerospace, Europe, Science, Space, Technology, USA

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EGS77 and Price-Whelan 1

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Away from the currently dreary, depressing world of our everyday societies, science continues to discover wonderful things.

The following three items are of particular interest to me because it’s astronomy.

First up: peering into the past has discovered galaxies forming from near the beginning of time:

Using data obtained by the Kitt Peak National Observatory, a team of astronomers with the Cosmic Deep And Wide Narrowband (Cosmic DAWN) Survey were able to observe the farthest galaxy group to date. Known as EGS77, this galaxy existed when the Universe was just 680 million years old (less than 5% of the age of the Universe). Analysis of this galaxy is already revealing things about the period that followed shortly after the Big Bang.

The young universe was filled with hydrogen atoms, which so attenuate ultraviolet light that they block our view of early galaxies. EGS77 is the first galaxy group caught in the act of clearing out this cosmic fog.”

Second, next time you look up at the Large and Small Magellanic Clouds circling the Southern Celestial Pole, you should know that they’re going to crash into us, and sooner than was thought:

The outskirts of the Milky Way are home to the galaxy’s oldest stars. But astronomers have spotted something unexpected in this celestial retirement community: a flock of young stars.

More surprising still, spectral analysis suggests that the infant stars have an extragalactic origin. The stars seemingly formed not from material from the Milky Way, but from two nearby dwarf galaxies known as the Magellanic Clouds. Those galaxies are on a collision course with our own.

The researchers propose that the cluster formed as gas from the Magellanic Stream passed through the gases surrounding the Milky Way. This pass-through created a drag force that compressed the Magellanic Stream gas. This drag, along with tidal forces from the Milky Way’s gravitational tug, condensed the gas enough to trigger star formation. Over time, the stars zoomed ahead of the surrounding gas and joined the Milky Way.

Looks like the Magellanic Stream is only about half as far away from our galaxy as was thought. 90,000 light years, which is nothing in galactic terms. The collision has effectively already begun, although it may have happened before. Galaxies colliding with each other are not like two solid bodies hitting each other, as the following simulation shows:

Speaking of things getting too close, the third item is about taking another look at a famous event, Tunguska asteroid merely ‘grazed’ the Earth:

On the morning of June 30, 1908, the sky above Siberia flared so bright and hot that a witness standing dozens of kilometers from the site thought that his shirt had caught fire, said Vladimir Pariev, co-author of the new Tunguska study and a researcher with the P. N. Lebedev Physical Institute of the Russian Academy of Sciences in Moscow. 

Following the bright light, which lasted for about 1 minute, was an explosion that smashed windows and knocked people off their feet in a town more than 35 miles (60 km) away.

Forest in Siberia smashed by the Tunguska asteroid, 1908

The problem is that there was no crater, and the long accepted explanation for this was that an asteroid had disintegrated between 5 and 10km above the ground, the resulting explosive airburst causing all the damage. But after another much smaller meteor exploded over Chelyabinsk, Russia, in February 2013, fragments of it were discovered within a week, while no such fragments from Tunguska have ever been found, and there should have been a lot of them. Now a bunch of Russian scientists have a new theory, that it was an iron meteor between 100m and 200m in size:

… the iron-rich space object could have entered Earth’s atmosphere at a very shallow angle — about 9 to 12 degrees tangential to the surface. It then would have grazed through the atmosphere, creating a shock wave at an altitude of around 6 to 10 miles (10 to 15 km) above the ground, capable of flattening trees for hundreds of kilometers and scorching the surface. But because of the meteor’s mass and momentum, it didn’t break up; it then exited the atmosphere and returned to space.

Other scientists doubt that such a shock wave would be powerful enough to do the damage seen and the footprint of the damage on the ground looks like it was an explosion from a point source. More fun with computer simulations, but it’s an intriguing theory.

Written by Tom Hunter

September 7, 2020 at 11:20 pm

Posted in Science, Space

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A hairy and fiery star

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    Halley’s Comet 1066, Bayeux Tapestry

My PhotoI’ve been lucky enough to see several comets in my life, starting with the spectacular Comet Bennet which hovered low above the Southern horizon in the Autumn skies in 1970.

In 1996 there was also Comet_Hyakutake and Comet Hale-Bopp, both of which were very bright in the night sky, but which I never got the best view of because of where I lived at the time.

The less said about Halley’s Comet in 1986 the better and even with increased lifespans I doubt I’ll get to see it in 2062. The ’86 appearance was the worst in 2000 years. I was rather surprised by this bit of information about its 1066 appearence:

Eilmer of Malmesbury may have seen Halley previously in 989, as he wrote of it in 1066: “You’ve come, have you? … You’ve come, you source of tears to many mothers, you evil. I hate you! It is long since I saw you; but as I see you now you are much more terrible, for I see you brandishing the downfall of my country. I hate you!”

And now we have Comet NEOWISE. It’s named after the space telescope and team that discovered it.

It’s a wonderful comet but unfortunately we’re not going to see it here in the Southern Hemisphere.

                                               Suchy Vrch, Czech Republic

 

You can check out previous pictures at the Archive. But also take a look at the links they have to amateur photos of the comet with: Notable Images of Comet NEOWISE Submitted to APOD, for July 15, July 14, and earlier.

A lot of beauty, which is needed in these times. Unlike the English in 1066, I’ll take this as a good sign.

 

Written by Tom Hunter

July 17, 2020 at 8:41 am

Posted in Science, Space

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Beetlejuice, Beetlejuice, Betelgeuse,…. BOOM?

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It’s … Showtime!

No, not that one!

The one whose name had to be said three times for him to arrive and wreak havoc on your enemies while also making you piss yourself either through laughing or being terrified.

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While also having designs on Winona Ryder because, …. well …. yummmm!

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This one, the Red Super Giant star, Betelgeuse.

 Betelgeuse

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Even most people who don’t watch the night sky will likely have seen it, usually because they mistake it for the planet Mars, being a big, fat, red blob in the sky, even though it’s only the tenth brightest star.

Mars moves of course, and it doesn’t twinkle, so it’s easy to distinguish the two. But it still may take a moment. Of course if you know your constellations you may not even make that initial mistake, since Betelgeuse is part of the distinctive and famous constellation of Orion.

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But don’t bother looking right now, because as the photos above show, Betelgeuse has undergone an extraordinary dimming in recent months, from a magnitude of +0.5 to +1.614. As an example, the brightest man-made object in the sky is the International Space Station (ISS), which can be as bright as -3.8.

Now Betelgeuse is a so-called variable star, with magnitude swings like this in the past, but they’ve usually been on a cycle driven by as-yet unknown processes. This dimming seems out of synch and since Red Supergiants end their short lives in a Supernova there is speculation that it might be about to happen here.

The reason for that speculation has to do with where it sits on the famous Hertzsprung-Russell Diagram, shown below. In fact Betelgeuse even gets its name on this particular one. The diagram is basically a statistical plot of two numbers – brightness and surface temperature – calculated for thousands of stars since the 19th century. If you want to know how they’re calculated read the link.

Hertzsprung-Russell Diagram

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The key thing the diagram shows is how stars evolve from birth to death. The so-called “main sequence” describes the most common stars, including our sun, with the other main groups being the Giants, Supergiants and White Dwarves.

The basic rule is that the bigger the star, the shorter its life, and the more catastrophic its end. They all start by fusing Hydrogen into Helium, as does our star, Sol, or “The Sun”. The life of stars the size of ours is around 10 billion years and Sol will become a Red Giant some 5-6 billion years from now as it starts fusing Helium: hence that blob labeled “Giants” extending off the middle of the Main Sequence where you can see our “Sun” listed. But that will be as far as it goes: it will then slowly collapse and cool over billions more years to become a White Dwarf. It’s just not big enough for its gravity to crush and fuse elements heavier than Helium.

But bigger stars with stronger gravity can do that, swelling in size as they push their fusion up the elementary table: H -> He -> Li -> Be -> …. all the way to Iron (FE).

As a result big stars that start on the main sequence in the top left gradually move to the right as they evolve into Blue, Yellow, and finally Red Supergiants. The conventional gravity fusion process stops at Iron, at which point the core of the star collapses in on itself. The end of this process is a so-called Type II Supernova event, which pours out more light and energy than their surounding galaxies in a matter of weeks. So energetic is the collapse and so wild the nuclear reactions that all elements beyond Iron are produced, all the way up to Uranium, the heaviest naturally occurring element.

What’s’ left behind depends on the mass and composition of the star, with ones less than 10 times the mass of Sol ending up as White Dwarves and ones larger than that ending as Neutron stars and Black Holes.

As Joni Mitchell observed, given we see all such elements here on Earth, “We are star dust“, our sun and solar system having condensed billions of years ago from the debri of Supernova.

 

Betelgeuse is about 700 light years from Earth, between 1400 to 2000 times the diameter of our sun, and anywhere between 15-20 times as massive. It’s estimated to be between 8 and 8.5 million years old and the maximum life for such huge stars is about 10 million years. The estimates for when it might explode are the next 100,000 years, based on the fact that, being a “closer” star, it can be studied in a little more detail, including when it blows off material, which may be what’s happening now, causing the dimming.

Whenever it does go, it’s going to be bright and easily seen with the naked eye.

Supernova 1987A is the bright star at the centre of the image
 

The most recent naked-eye supernova was SN 1987A, the explosion of a blue supergiant star in the Large Magellanic Cloud – which can only be seen from the Southern Hemisphere – on February 23, 1987.

It was co-discovered by a New Zealand astronomer, Albert Jones, adding to his already somewhat famous record in amateur astronomy.

I arrived back in New Zealand from an OE in time to see it – I thought – but although its apparent magnitude rose to about +3 by May I just never caught it with my eye, even with binoculars.

Bugger!

The previous naked-eye supernova was in 1604 so they’re rare beasts.

Hence my hopes for Betelgeuse exploding which, if it does, will make it as bright as the Moon for weeks on end, as shown in the following simulated view of it as a Supernova near the other stars of Orion.

Written by Tom Hunter

February 25, 2020 at 7:05 pm

Posted in New Zealand

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