Closest-Ever Look At Betelgeuse Reveals its Fiery Secret

Artist’s impression of the supergiant star Betelgeuse as it was revealed with ESO’s Very Large Telescope. Credit: ESO/L.Calçada

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The giant star Betelgeuse churns out gas bubbles that match its own size — and that’s how it can shed an entire solar mass in 10,000 years.

That according to the sharpest-ever images of Orion’s second-brightest star, released this week by the European Organisation for Astronomical Research in the Southern Hemisphere (ESO). At left is an artist’s impression of the supergiant star Betelgeuse as it was revealed in the new images (courtesy of ESO and L.Calçada). The actual images follow …

This collage shows the Orion constellation in the sky (Betelgeuse is identified by the marker), a zoom towards Betelgeuse, and the sharpest ever image of this supergiant star, which was obtained with NACO on ESO’s Very Large Telescope. Credit: ESO, P.Kervella, Digitized Sky Survey 2 and A. Fujii
This collage shows the Orion constellation in the sky (Betelgeuse is identified by the marker), a zoom towards Betelgeuse, and the sharpest ever image of this supergiant star, which was obtained with NACO on ESO’s Very Large Telescope. Credit: ESO, P.Kervella, Digitized Sky Survey 2 and A. Fujii

Betelgeuse, the second brightest star in the constellation of Orion (the Hunter), is a red supergiant, one of the biggest stars known, and almost 1,000 times larger than our Sun. It is also one of the most luminous stars known, emitting more light than 100,000 Suns.

Red supergiants still hold several unsolved mysteries. One of them is just how these behemoths shed such tremendous quantities of material — about the mass of the Sun — in only 10,000 years.

With an age of only a few million years, the Betelgeuse star is already nearing the end of its life and is soon doomed to explode as a supernova. When it does, the supernova should be seen easily from Earth, even in broad daylight.

Using ESO’s Very Large Telescope, two independent teams of astronomers have obtained the sharpest ever views of the supergiant star.

The first team used the adaptive optics instrument, NACO, combined with a so-called “lucky imaging” technique, to obtain the sharpest ever image of Betelgeuse, even with Earth’s turbulent, image-distorting atmosphere in the way. With lucky imaging, only the very sharpest exposures are chosen and then combined to form an image much sharper than a single, longer exposure would be.

The resulting NACO images almost reach the theoretical limit of sharpness attainable for an 8-metre telescope. The resolution is as fine as 37 milliarcseconds, which is roughly the size of a tennis ball on the International Space Station (ISS), as seen from the ground.

“Thanks to these outstanding images, we have detected a large plume of gas extending into space from the surface of Betelgeuse,” said Pierre Kervella from the Paris Observatory, who led the team. The plume extends to at least six times the diameter of the star, corresponding to the distance between the Sun and Neptune. “This is a clear indication that the whole outer shell of the star is not shedding matter evenly in all directions.”

Two mechanisms could explain this asymmetry. One assumes that the mass loss occurs above the polar caps of the giant star, possibly because of its rotation. The other possibility is that such a plume is generated above large-scale gas motions inside the star, known as convection — similar to the circulation of water heated in a pot.

To arrive at a solution, Keiichi Ohnaka from the Max Planck Institute for Radio Astronomy in Bonn, Germany, and his colleagues used ESO’s Very Large Telescope Interferometer. The astronomers were able to detect details four times finer still than the NACO images had allowed — in other words, the size of a marble on the ISS, as seen from the ground.

“Our AMBER observations are the sharpest observations of any kind ever made of Betelgeuse. Moreover, we detected how the gas is moving in different areas of Betelgeuse’s surface — the first time this has been done for a star other than the Sun,” Ohnaka said.

The AMBER observations revealed that the gas in Betelgeuse’s atmosphere is moving vigorously up and down, and that these bubbles are as large as the supergiant star itself. The astronomers are proposing that these large-scale gas motions roiling under Betelgeuse’s red surface are behind the ejection of the massive plume into space.

Source: European Organisation for Astronomical Research in the Southern Hemisphere (ESO). Two related papers are here and here.

Inside of Venus

From our perspective here on Earth, Venus is completely covered in clouds. So what’s inside Venus? For most of history, scientists had no idea what’s inside of Venus. The earliest telescopes showed hazy cloud tops, and even the largest telescopes didn’t improve the view. Some astronomers thought they might have caught a glimpse of the surface through the clouds, or maybe the peak of a tall mountain poking up through the clouds. But we now know those were just observation errors.

It wasn’t until the first spacecraft from Earth arrived at Venus, and started gathering scientific data about the inside of Venus. NASA’s Mariner 2 helped scientists calculate that the density of Venus is very similar to the density of Earth. Although there were no direct observations of Venus’ interior, scientists assume that it must be similar to Earth. The inside of Venus is thought to contain a solid/liquid core of metal 3,000 km across. This is surrounded by a mantle of rock 3,000 km thick. And then there’s a thin crust of rock about 50 km thick.

When NASA’s Magellan spacecraft was launched to Venus in 1989, it was carrying a suite of powerful radar mapping instruments. These tools could pierce through the thick clouds surrounding Venus and reveal the surface of the planet in great detail. Magellan found that the surface of Venus is actually quite young, and was probably resurfaced 300-500 million years ago, based on the number of impact craters found on its surface.

Magellan also found evidence of a large number of volcanoes; they number in the thousands and maybe even in the millions. The shield volcanoes found across the surface of Venus indicate that the inside of Venus is still active, with magma pushing to the surface around the planet.

It’s believed that the event that resurfaced Venus 300-500 million years ago might have also shut down plate tectonics on Venus. Without the movement of plates to release trapped heat, the inside of Venus remained much hotter than it would be. It’s thought that this increase in heat also shut down the convection of metal around the core of Venus. It’s this convection in the Earth’s core that’s thought to run our planet’s magnetic field.

We have written many articles about Venus for Universe Today. Here’s an article about Venus’ wet, volcanic past, and here’s an article about how Venus might have had continents and oceans in the ancient past.

Want more information on Venus? Here’s a link to Hubblesite’s News Releases about Venus, and here’s NASA’s Solar System Exploration Guide to Venus.

We have recorded a whole episode of Astronomy Cast that’s only about planet Venus. Listen to it here, Episode 50: Venus.

References:
NASA Solar System Exploration: Terrestrial Planets
Venus Interior

Core of Venus

Venus is a tricky place to study because it’s shrouded in a thick atmosphere that hides its surface. And if you can’t even see its surface, imagine how difficult it must be to study the interior of Venus. But scientists have been making steady progress towards understanding the interior of the planet, and learn about the core of Venus.

Here on Earth, scientists study the core of the planet by measuring how seismic waves move through the planet after earthquakes. As they pass through the different layers of the Earth’s interior; the core, the mantle, and the crust, the waves reflect or bend depending on the change of density that they’re passing through. Well, the surface of Venus is hot enough to melt lead, and spacecraft are destroyed within a few hours of reaching the surface of Venus, so no readings have been gathered about Venus’ core directly.

Instead, scientists assume that the core of Venus exists based on calculations of its density. The density of Venus is only a little less than the density of Earth. This means that Venus probably has a core of metal about 3,000 km across, surrounded by a 3,000 km thick mantle and a 50 km thick crust.

Scientists aren’t sure if the core of Venus is solid or liquid, but they have a few hints. That’s because Venus doesn’t have a planet wide magnetic field like the Earth. It’s believed that the Earth’s magnetic field is generated by the convection of liquid in the Earth’s core. Since Venus doesn’t have a planetary magnetic field, it’s possible that Venus’ core is made of solid metal, or maybe there isn’t enough of a temperature gradient between the inner and outer core to made this convection happen.

It’s believed that a global resurfacing event that occurred about 300-500 million years ago might have something to do with this. The entire surface of Venus was resurfaced, shutting down plate tectonics. This might have led to a reduced heat flux through the crust, trapping the heat inside the planet. Without the big heat difference, there’s little heat convection, and so no magnetic field coming from the core of Venus.

We have written many articles about Venus for Universe Today. Here’s an article about Venus’ wet, volcanic past, and here’s an article about how Venus might have had continents and oceans in the ancient past.

Want more information on Venus? Here’s a link to Hubblesite’s News Releases about Venus, and here’s NASA’s Solar System Exploration Guide to Venus.

We have recorded a whole episode of Astronomy Cast that’s only about planet Venus. Listen to it here, Episode 50: Venus.

References:
NASA Solar System Exploration: Terrestrial Planets
Venus Interior

Geology of Venus

Artist's impression of the surface of Venus, showing its lightning storms and a volcano in the distance. Credit and ©: European Space Agency/J. Whatmore

Take a look at Venus in even the most powerful telescope, and all you’ll see is clouds. There are no surface features visible at all. It wasn’t until the last few decades, when radar equipped spacecraft arrived at Venus, that scientists finally had a chance to study the geology of Venus in great detail.

Spacecraft like NASA’s Magellan mission are equipped with radar instruments that let it penetrate down through the clouds on Venus and reveal the surface below. Magellan found that the surface of Venus does have many impact craters and evidence of past volcanism. But the total number of craters showed that the surface of Venus is actually pretty young. It’s likely that some catastrophic event resurfaced Venus about 300-500 million years ago, wiping out old craters and volcanoes.

Unlike Earth, Venus doesn’t have plate tectonics. It’s possible that the planet had them in the ancient past, but rising temperatures shut them down and helped the planet go into a runaway greenhouse cycle. Carbon on Earth is trapped by plants, and is then recycled into the Earth through plate tectonics. But on Venus, the tectonic system shut down, so carbon was able to build up to tremendous levels. This cycle thickened the atmosphere, raised temperatures with its greenhouse effect, releasing more carbon, raising temperatures even higher… etc.

There are volcanoes on Venus; scientists have identified more than 100 isolated shield volcanoes. And there are thousands and maybe even millions of smaller volcanoes less than 20 km across. Many of these have a strange dome-shaped structure, believed to have formed when plumes of magma thrust the crust upward and then collapsed.

Scientists can’t be exactly sure what the internal structure of Venus is like, but based on its density, Venus is probably similar to Earth in composition. It’s believed to have a solid or liquid core of metal 3,000 km across. This is surrounded by a mantle of rock 3,000 km thick, and then a thin crust of solid rock about 50 km thick.

One big difference between Earth and Venus is the lack of a planetary magnetic field at Venus. It’s believed that the Earth’s magnetic field is driven by the convection of liquid metal at the Earth’s core. If true, it means that Venus probably doesn’t have the same kind of temperature differences at its core, and lacks the convection to sustain a planetary magnetic field.

We have written many articles about Venus for Universe Today. Here’s an article about Venus’ wet, volcanic past, and here’s an article about how Venus might have had continents and oceans in the ancient past.

Want more information on Venus? Here’s a link to Hubblesite’s News Releases about Venus, and here’s NASA’s Solar System Exploration Guide to Venus.

We have recorded a whole episode of Astronomy Cast that’s only about planet Venus. Listen to it here, Episode 50: Venus.

Reference:
NASA Solar System Exploration: Geologic Landforms of Venus
NASA Science: Blazing Venus
NASA Solar System Exploration: Venus

Composition of Venus

Venus is often referred to as Earth’s twin planet (evil twin planet is more like it, when you consider the scorching temperatures). It’s almost the same size, mass, gravity and overall composition. The composition of Venus is pretty similar to Earth, with a core of metal, a mantle of liquid rock, and an outer crust of solid rock.

Unfortunately, scientists have no direct knowledge about Venus composition. Here on Earth, scientists use seismometers to study how seismic waves from earthquakes propagate through the planet. How these waves bounce and turn inside the Earth tell scientists about its composition. Since the surface of Venus is hot enough to melt lead, and no spacecraft have survived on the surface for longer than a few hours, there just isn’t the information about Venus’ internal composition.

Scientists can calculate the density of Venus, though. Since it’s similar to Earth, and the other terrestrial planets, scientists guess that the internal structure of Venus is similar to Earth. One of the big differences between our two planets, however, is the lack of plate tectonics on Venus. For some reason, plate tectonics on Venus shut down billions of years ago. This has prevented the interior of Venus from losing as much heat as the Earth does, and could be the reason Venus doesn’t have an internally generated magnetic field.

Before spacecraft missions were sent to Venus, scientists had no idea what the composition of Venus was. They could calculate the planet’s density, but the surface of Venus was obscured by dense clouds. Spacecraft equipped with radar were able to penetrate the thick clouds and map out features on the planet’s surface, showing that it has impact craters and ancient volcanoes. It’s believed that Venus went through some kind of global resurfacing event about 300-500 million years ago, which is the age of the planet’s surface (calculated by the number of impact craters).

The crust of Venus is thought to be about 50 km thick, and composed of silicious rocks. Beneath that is the mantle, which is thought to be about 3,000 km thick. The composition of the mantle is unknown. And then at the center of Venus is a solid or liquid core of iron or nickel. Since Venus doesn’t have a global magnetic field, scientists think that the planet doesn’t have convection in its core. The planet doesn’t have a large difference in temperature between the inner and outer core, and so the metal doesn’t flow around and generate a magnetic field.

We have written many articles about Venus for Universe Today. Here’s an article about Venus’ wet, volcanic past, and here’s an article about how Venus might have had continents and oceans in the ancient past.

Want more information on Venus? Here’s a link to Hubblesite’s News Releases about Venus, and here’s NASA’s Solar System Exploration Guide to Venus.

We have recorded a whole episode of Astronomy Cast that’s only about planet Venus. Listen to it here, Episode 50: Venus.

References:
Geophysical Models of Western Aphrodite-Niobe
NASA Solar System Exploration: Terrestrial Planet Interiors

Triple Spaceship Sighting Alert!

ISS as seen from departing space shuttle Endeavour. Credit: NASA TV

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A great opportunity tonight (July 28) to see three spaceships cross the sky at once! Endeavour just undocked from the ISS today, so they will be close to each other, plus there’s another spaceship lurking nearby: a Progress re-supply ship ready to dock with the ISS. How can you find out when and where to look for the three spacecraft? There are a couple of different websites that provide real-time tracking data and information about the ISS sighting opportunities. See below for more info.

The image above is a screenshot from NASA TV of the ISS as Endeavour undocked. Notice the shadow of the shuttle on the ISS solar arrays!

NASA has a Quick and Easy Sightings by City site, where you just search for your country and city which provides local times and the location in the sky where the station will be visible.

The European Space Agency also provides their ISS: Where Is It Now site that also allows you to select your country and city to find the station’s location.

The Heaven’s Above website (which also powers ESA’s site) is also an excellent site to find out when the ISS, as well as all sorts of other satellites and other heavenly sights will be visible. At Heaven’s Above, you can plug in your exact latitude and longitude, so if you live in a remote area, you’ll be able to have exact times and locations to look for satellites instead of relying on information for the nearest city.

There’s also this very cool Google Satellite tracker.

Additionally, you can get a notification on Twitter when the space station will be zooming over your skies. Follow Twisst. (Thanks to big ian for the reminder of this new Twitter addition!)

Here’s wishing everyone clear skies and great views!

STS-127: A Mission in Pictures

Astronaut Tim Kopra during an EVA. Credit: NASA

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As space shuttle Endeavour undocks from the International Space Station today (Tuesday), now is a good time to look back at the very successful STS-127 mission. Here’s some great images which tell the story of the mission. Above, astronaut Tim Kopra is pictured in the forward port side area of Endeavour’s cargo bay during the first of five planned spacewalks performed by the STS-127 crew. Kopra is now part of the ISS crew, and is staying onboard the space station to serve as flight engineer.

Moon rock on board the ISS. Credit: NASA
Moon rock on board the ISS. Credit: NASA

Of course, during this mission we celebrated the 40th anniversary of the Apollo 11 Moon landing. Fittingly, there was a Moon rock on board the ISS. The 3.6 billion year-old lunar sample was flown to the station aboard Space Shuttle mission STS-119 in April 2009. NASA says the rock, lunar sample 10072 serves as a symbol of the nation’s resolve to continue the exploration of space. It will be returned on shuttle mission STS-128 to be publicly displayed.
The new Kibo platform, or "front porch." Credit: NASA
Here’s a view of the newly installed “front porch” of the Kibo lab, which is actually the Japanese Experiment Module – Exposed Facility (JEF). This platform will hold experiments designed to work outside the protective confines of the station, exposing them to the space environment. The JEF was installed by the astronauts during this mission.
Dave Wolf during an EVA. Credit: NASA
Dave Wolf during an EVA. Credit: NASA

During the second STS-127 spacewalk, astronaut Dave Wolf worked outside bringing the Linear Drive Unit (LDU) and two other parts to the station’s External Stowage Platform 3 for long-term storage. Wolf is near the end of Canadarm2, which is anchored on the ISS.
Arms in space. Credit: NASA
Arms in space. Credit: NASA

Speaking of the robotic arms, here’s a view of both the space station and space shuttle robotic arms as seen from inside the Kibo laboratory. A portion of the Japanese Experiment Module – Exposed Facility is also visible. The blackness of space and Earth’s horizon provide the backdrop for the scene.
Tom Marshburn during an EVA. Credit: NASA
Tom Marshburn during an EVA. Credit: NASA

Astronaut Tom Marshburn makes his second spacewalk on July 24, along with Christopher Cassidy, out of frame. Eleven other astronauts and cosmonauts remained inside the International Space Station and the shuttle while the two astronauts worked outside.
Astronauts share a lunch on the ISS. Credit: NASA
Astronauts share a lunch on the ISS. Credit: NASA

In total, there were 13 astronauts on board the ISS, a record for the amount of astronauts in one vehicle. Pictured, clockwise from bottom right, are astronauts Christopher Cassidy and Mike Barratt, with Russian Federal Space Agency cosmonaut Roman Romanenko, an unidentified crew member, Japanese Aerospace Exploration Agency astronaut Koichi Wakata (floating above), Canadian Space Agency astronauts Robert Thirsk and Julie Payette, European Space Agency astronaut Frank De Winne, and astronaut Christopher Cassidy. Either out of frame or not clearly seen are astronauts Mark Polansky, Doug Hurley, Dave Wolf, Tim Kopra and Tom Marshburn, plus Russian Federal Space Agency cosmonaut Gennady Padalka.
ISS as seen from departing space shuttle Endeavour. Credit: NASA TV
ISS as seen from departing space shuttle Endeavour. Credit: NASA TV

This screen shot shows the ISS as seen as Endeavour departed from the station on July 28. The views of both the ISS and shuttle were stunning. We’ll post the high-resolution versions when they become available. Notice the shadow of the space shuttle on the space station solar arrays! Amazing!
Endeavour's launch. Credit: NASA
Endeavour's launch. Credit: NASA


And now we’re back to the beginning of the mission. Liftoff for the STS-was at 6:03 p.m. (EDT) on July 15, 2009 from launch pad 39A at NASA’s Kennedy Space Center. The storm clouds stayed far enough away so that Endeavour and her STS-127 crew finally on its sixth attempt. Watch a replay of the launch here.

Circumference of Venus

Earth and Venus. Image credit: NASA

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The average circumference of Venus is 38,025 km.

Need some comparison? The average circumference of Earth is 40,041 km. And then if you compare the two numbers, you find that the circumference of Venus is about 95% the circumference of Earth.

If you’ll notice at the top of the article, I specified that we’re talking about the “average circumference”. That’s the number if you average out all the circumference measurements around the planet. This is normally very important when you measure the circumference of planets since they’re often spinning quite rapidly. This rotation causes them to flatten out and bulge around the equator. This means that the equatorial circumference is larger than the circumference if you measure it from pole to pole.

The average (or mean) circumference on Earth is 40,041 km. The equatorial circumference is 40,075 km, and the polar circumference is 40,008 km. So you can see, that’s a pretty big difference, and the average is very important. But here’s the thing. Venus rotates so slowly that it doesn’t bulge at the equator. While the Earth turns once on its axis every 24 hours, Venus takes 243 days to complete a day – that’s even longer than a year on Venus!

Need your numbers in miles? No problem. The circumference of Venus in miles is 23,628 miles.

We have written many articles about Venus for Universe Today. Here’s an article about Venus’ wet, volcanic past, and here’s an article about how Venus might have had continents and oceans in the ancient past.

Want more information on Venus? Here’s a link to Hubblesite’s News Releases about Venus, and here’s NASA’s Solar System Exploration Guide to Venus.

We have recorded a whole episode of Astronomy Cast that’s only about planet Venus. Listen to it here, Episode 50: Venus.

Density of Venus

The density of Venus is 5.204 grams per cubic centimeter.

Need some kind of comparison? The density of Earth is 5.515 g/cm3. So Venus is definitely less dense than Earth. And it’s even less dense than Mercury. Of course, it’s much more dense than any of the outer planets, like Jupiter or Saturn.

Scientists think that Venus has an interior structure similar to Earth, with a metal core, rocky mantle, and an outer crust. But these assumptions come purely from the density calculations. Here on Earth, scientists study the interior structure of the planet by using seismographs, and studying how seismic waves from earthquakes travel through the Earth. Since the surface of Venus is hot enough to melt lead, there’s no way to leave scientific equipment on the surface for any period of time to study the interior of the planet.

With its lower density, Venus has a lower mass than Earth. In fact, the mass of Venus is only about 81% the mass of Earth. And it’s also a little smaller than Earth. This means that the surface gravity of Venus is only 90% of what you would experience on Earth.

We have written many articles about Venus for Universe Today. Here’s an article about Venus’ wet, volcanic past, and here’s an article about how Venus might have had continents and oceans in the ancient past.

Want more information on Venus? Here’s a link to Hubblesite’s News Releases about Venus, and here’s NASA’s Solar System Exploration Guide to Venus.

We have recorded a whole episode of Astronomy Cast that’s only about planet Venus. Listen to it here, Episode 50: Venus.

Axis of Venus

Earth and Venus. Image credit: NASA

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The axial tilt of Venus is 177.3°. That’s a bit of a confusing number, so let’s figure out what’s going on here. Compare this number to the Earth’s axial tilt of 23.5°. Our tilt gives us such different seasons between summer and winter, so you’d expect that Venus’ much larger tilt would cause more extreme seasons.

Nope. But if you remember your high school geometry, you’ll realize what’s going on. A full circle is 360°. Half a circle is 180°. So if you subtract 177.3° from 180°, you get 2.7°. In other words, Venus is actually only tilted away from the plane of the ecliptic by only 2.7°. Venus is actually completely upside down – almost perfectly upside down.

In fact, Venus is the only planet in the Solar System that rotates backwards compared to the other planets. Seen from above, all the planets are turning in a counter clockwise direction. That’s why Asia sees the Sun first, then Europe, and then the Americas. Mars is the same, and so is Mercury, but Venus is rotating clockwise.

It’s possible that Venus was knocked upside down by a massive impact early in its history. it’s also possible that Venus just slowed down through tidal locking with the Sun, and was somehow spun slowly backwards through its interactions with the other planets.

Here on Earth, the axial tilt is responsible for the seasons. When it’s winter in the northern hemisphere, the north pole is tilted away from the Sun, and less of the Sun’s radiation falls on every square meter of ground. The opposite is true in the summer. Without a significant axial tilt, Venus doesn’t experience seasons like this. The temperature of Venus is a nice even 462°C everywhere on the whole planet.

We have written many articles about Venus for Universe Today. Here’s an article about Venus’ wet, volcanic past, and here’s an article about how Venus might have had continents and oceans in the ancient past.

Want more information on Venus? Here’s a link to Hubblesite’s News Releases about Venus, and here’s NASA’s Solar System Exploration Guide to Venus.

We have recorded a whole episode of Astronomy Cast that’s only about planet Venus. Listen to it here, Episode 50: Venus.