How We Know Gravity is Not (Just) a Force

This artist’s impression shows the exotic double object that consists of a tiny, but very heavy neutron star that spins 25 times each second, orbited every two and a half hours by a white dwarf star. The neutron star is a pulsar named PSR J0348+0432 that is giving off radio waves that can be picked up on Earth by radio telescopes. Although this unusual pair is very interesting in its own right it is also a unique laboratory for testing the limits of physical theories. This system is radiating gravitational radiation, ripples in spacetime. Although these waves cannot be yet detected directly by astronomers on Earth they can be detected indirectly by measuring the change in the orbit of the system as it loses energy. As the pulsar is so small the relative sizes of the two objects are not drawn to scale.

When  we think of gravity, we typically think of it as a force between masses.  When you step on a scale, for example, the number on the scale represents the pull of the Earth’s gravity on your mass, giving you weight.  It is easy to imagine the gravitational force of the Sun holding the planets in their orbits, or the gravitational pull of a black hole.  Forces are easy to understand as pushes and pulls.

But we now understand that gravity as a force is only part of a more complex phenomenon described the theory of general relativity.  While general relativity is an elegant theory, it’s a radical departure from the idea of gravity as a force.  As Carl Sagan once said, “Extraordinary claims require extraordinary evidence,” and Einstein’s theory is a very extraordinary claim.  But it turns out there are several extraordinary experiments that confirm the curvature of space and time.

The key to general relativity lies in the fact that everything in a gravitational field falls at the same rate.  Stand on the Moon and drop a hammer and a feather, and they will hit the surface at the same time.  The same is true for any object regardless of its mass or physical makeup, and this is known as the equivalence principle.

Since everything falls in the same way regardless of its mass, it means that without some external point of reference, a free-floating observer far from gravitational sources and a free-falling observer in the gravitational field of a massive body each have the same experience. For example, astronauts in the space station look as if they are floating without gravity.  Actually, the gravitational pull of the Earth on the space station is nearly as strong as it is at the surface.  The difference is that the space station (and everything in it) is falling.  The space station is in orbit, which means it is literally falling around the Earth.

The International Space Station orbiting Earth. Credit: NASA
The International Space Station orbiting Earth. Credit: NASA

This equivalence between floating and falling is what Einstein used to develop his theory.  In general relativity, gravity is not a force between masses.  Instead gravity is an effect of the warping of space and time in the presence of mass.  Without a force acting upon it, an object will move in a straight line.  If you draw a line on a sheet of paper, and then twist or bend the paper, the line will no longer appear straight.  In the same way, the straight path of an object is bent when space and time is bent.  This explains why all objects fall at the same rate.  The gravity warps spacetime in a particular way, so the straight paths of all objects are bent in the same way near the Earth.

So what kind of experiment could possibly prove that gravity is warped spacetime?  One stems from the fact that light can be deflected by a nearby mass.  It is often argued that since light has no mass, it shouldn’t be deflected by the gravitational force of a body.  This isn’t quite correct. Since light has energy, and by special relativity mass and energy are equivalent, Newton’s gravitational theory predicts that light would be deflected slightly by a nearby mass.  The difference is that general relativity predicts it will be deflected twice as much.

Description of Eddington's experiment from the Illustrated London News (1919).
Description of Eddington’s experiment from the Illustrated London News (1919).

The effect was first observed by Arthur Eddington in 1919.  Eddington traveled to the island of Principe off the coast of West Africa to photograph a total eclipse. He had taken photos of the same region of the sky sometime earlier. By comparing the eclipse photos and the earlier photos of the same sky, Eddington was able to show the apparent position of stars shifted when the Sun was near.  The amount of deflection agreed with Einstein, and not Newton.  Since then we’ve seen a similar effect where the light of distant quasars and galaxies are deflected by closer masses.  It is often referred to as gravitational lensing, and it has been used to measure the masses of galaxies, and even see the effects of dark matter.

Another piece of evidence is known as the time-delay experiment.  The mass of the Sun warps space near it, therefore light passing near the Sun is doesn’t travel in a perfectly straight line.  Instead it travels along a slightly curved path that is a bit longer.  This means light from a planet on the other side of the solar system from Earth reaches us a tiny bit later than we would otherwise expect.  The first measurement of this time delay was in the late 1960s by Irwin Shapiro.  Radio signals were bounced off Venus from Earth when the two planets were almost on opposite sides of the sun. The measured delay of the signals’ round trip was about 200 microseconds, just as predicted by general relativity.  This effect is now known as the Shapiro time delay, and it means the average speed of light (as determined by the travel time) is slightly slower than the (always constant) instantaneous speed of light.

A third effect is gravitational waves.  If stars warp space around them, then the motion of stars in a binary system should create ripples in spacetime, similar to the way swirling your finger in water can create ripples on the water’s surface.  As the gravity waves radiate away from the stars, they take away some of the energy from the binary system. This means that the two stars gradually move closer together, an effect known as inspiralling. As the two stars inspiral, their orbital period gets shorter because their orbits are getting smaller.

Decay of pulsar period compared to prediction (dashed curve).  Data from Hulse and Taylor, Plotted by the author.
Decay of pulsar period compared to prediction (dashed curve). Data from Hulse and Taylor, Plotted by the author.

For regular binary stars this effect is so small that we can’t observe it. However in 1974 two astronomers (Hulse and Taylor) discovered an interesting pulsar. Pulsars are rapidly rotating neutron stars that happen to radiate radio pulses in our direction. The pulse rate of pulsars are typically very, very regular. Hulse and Taylor noticed that this particular pulsar’s rate would speed up slightly then slow down slightly at a regular rate. They showed that this variation was due to the motion of the pulsar as it orbited a star. They were able to determine the orbital motion of the pulsar very precisely, calculating its orbital period to within a fraction of a second. As they observed their pulsar over the years, they noticed its orbital period was gradually getting shorter. The pulsar is inspiralling due to the radiation of gravity waves, just as predicted.

Illustration of Gravity Probe B.  Credit: Gravity Probe B Team, Stanford, NASA
Illustration of Gravity Probe B. Credit: Gravity Probe B Team, Stanford, NASA

Finally there is an effect known as frame dragging.  We have seen this effect near Earth itself.  Because the Earth is rotating, it not only curves spacetime by its mass, it twists spacetime around it due to its rotation.  This twisting of spacetime is known as frame dragging.  The effect is not very big near the Earth, but it can be measured through the Lense-Thirring effect.  Basically you put a spherical gyroscope in orbit, and see if its axis of rotation changes.  If there is no frame dragging, then the orientation of the gyroscope shouldn’t change.  If there is frame dragging, then the spiral twist of space and time will cause the gyroscope to precess, and its orientation will slowly change over time.

results_graph-lg
Gravity Probe B results. Credit: Gravity Probe B team, NASA.

We’ve actually done this experiment with a satellite known as Gravity Probe B, and you can see the results in the figure here.  As you can see, they agree very well.

Each of these experiments show that gravity is not simply a force between masses.  Gravity is instead an effect of space and time.  Gravity is built into the very shape of the universe.

Think on that the next time you step onto a scale.

China’s Chang’e-3 Lander and Yutu Moon Rover – from Above and Below

Chang’e-3 lander and Yutu rover – from Above And Below Composite view shows China’s Chang’e-3 lander and Yutu rover from Above And Below (orbit and surface) – lander color panorama (top) and orbital view from NASA’s LRO orbiter (bottom). Chang’e-3 lander color panorama shows Yutu rover after it drove down the ramp to the moon’s surface and began driving around the landers right side to the south. Yellow lines connect craters seen in the lander panorama and the LROC image from LRO (taken at a later date after the rover had moved), red lines indicate approximate field of view of the lander panorama. Credit: CNSA/NASA/Ken Kremer/Marco Di Lorenzo/Mark Robinson

Chang’e-3 lander and Yutu rover – from Above And Below
Composite view shows China’s Chang’e-3 lander and Yutu rover from Above And Below (orbit and surface) – lander color panorama (top) and orbital view from NASA’s LRO orbiter (bottom). Chang’e-3 lander color panorama shows Yutu rover after it drove down the ramp to the moon’s surface and began driving around the landers right side to the south. Yellow lines connect craters seen in the lander panorama and the LROC image from LRO (taken at a later date after the rover had moved), red lines indicate approximate field of view of the lander panorama. Credit: CNSA/NASA/Ken Kremer/Marco Di Lorenzo/Mark Robinson
See further composite and panorama views below
Story updated
See our Yutu timelapse pano at NASA APOD Feb. 3, 2014: http://apod.nasa.gov/apod/ap140203.html[/caption]

China’s Chang’e-3 lander and Yutu moon rover have been imaged from above and below – in one of those rare, astounding circumstances when space probes from Earth are exploring an extraterrestrial body both from orbit and the surface. And it’s even more amazing when these otherworldly endeavors just happen to overlap and involve actual work in progress to expand human knowledge of the unknown.

And it’s even rarer, when those images stem from active space probes built by two different countries on Earth.

Well by combining imagery from America’s space agency, NASA, and China’s space agency, CNSA, we are pleased to present some breathtaking views of ‘Chang’e-3 and the Yutu rover from Above and Below.’

Check out our composite mosaic (above) combining the view from the Moon’s orbit snapped by the hi res camera aboard NASA’s Lunar Reconnaissance Orbiter (LRO) with our new color panoramas from the Moon’s surface, compiling imagery from the landing site of China’s Chang’e-3 lander – with Yutu in transit in mid-Dec. 2013 soon after the successful touchdown.

See below an earlier composite mosaic using the first black and white panorama from the Chang’e-3 Moon lander.

Chang’e-3 lander and Yutu rover – from Above And Below  Composite view shows China’s Chang'e-3 lander and Yutu rover from Above And Below (orbit and surface) - lander panorama (top) and orbital view from NASA’s LRO orbiter (bottom).  Chang'e-3 lander B/W panorama from camera shows Yutu rover after it drove down the ramp to the moon’s surface and began driving around the landers right side to the south. Yellow lines connect craters seen in the lander panorama and the LROC image from LRO (taken at a later date after the rover had moved), red lines indicate approximate field of view of the lander panorama.    Credit: CNSA/NASA/Mark Robinson/Marco Di Lorenzo/Ken Kremer
Chang’e-3 lander and Yutu rover – from Above And Below
Composite view shows China’s Chang’e-3 lander and Yutu rover from Above And Below (orbit and surface) – lander panorama (top) and orbital view from NASA’s LRO orbiter (bottom). Chang’e-3 lander B/W panorama from camera shows Yutu rover after it drove down the ramp to the moon’s surface and began driving around the landers right side to the south. Yellow lines connect craters seen in the lander panorama and the LROC image from LRO (taken at a later date after the rover had moved), red lines indicate approximate field of view of the lander panorama. Credit: CNSA/NASA/Mark Robinson/Marco Di Lorenzo/Ken Kremer – kenkremer.com

The composite mosaic combines the efforts of Mark Robinson, Principal Investigator for the LRO camera, and the imaging team of Ken Kremer and Marco Di Lorenzo.

On Christmas eve, Dec. 24, 2013, NASA’s LRO captured it’s first images of China’s Chang’e-3 lander and Yutu moon rover – barely 10 days after the history making touchdown on Mare Imbrium (Sea of Rains) and just 60 meters east of the rim of a 450 meter diameter impact crater.

LRO was orbiting about 150 kilometers above Chang’e-3 and Yutu when the highest resolution orbital image was taken on 24 December 22:52:49 EST (25 December 03:52:49 UT).

Image of Chang'e-3 (top arrow) and Yutu rover captured by NASA's Lunar Reconnaissance Orbiter on Dec. 25 UTC
Image of Chang’e-3 (top arrow) and Yutu rover captured by NASA’s Lunar Reconnaissance Orbiter on Dec. 24, 2013

The orbital imagery was taken by the LRO orbiters high resolution Lunar Reconnaissance Orbiter Camera (LROC) – specifically the narrow angle camera (NAC).

See below my pre-launch cleanroom photo of LRO and the LROC cameras and other science instruments.

The Chang’e-3 lander color panorama shows the Yutu rover after it drove down the ramp to the moon’s surface and began driving a significant distance around the landers right side on its journey heading southwards.

1st 360 Degree Color Panorama from China’s Chang’e-3 Lunar Lander. This 1st color panorama from Chang’e-3 lander shows the view all around the landing site after the ‘Yutu’ lunar rover left impressive tracks behind when it initially rolled all six wheels onto the pockmarked and gray lunar terrain on Dec. 15, 2013. Mosaic Credit: CNSA/Chinanews/Ken Kremer/Marco Di Lorenzo – kenkremer.com
1st 360 Degree Color Panorama from China’s Chang’e-3 Lunar Lander
This 1st color panorama from Chang’e-3 lander shows the view all around the landing site after the ‘Yutu’ lunar rover left impressive tracks behind when it initially rolled all six wheels onto the pockmarked and gray lunar terrain on Dec. 15, 2013. Mosaic Credit: CNSA/Chinanews/Ken Kremer/Marco Di Lorenzo – kenkremer.com

Yellow lines connect craters seen in the lander panorama to those seen in the LROC hi res NAC image from LRO, in the composite view.

Robinson identified the lunar craters and determined the field of view on the LROC image.

The LRO image was taken at a later date (on Christmas eve) after the rover had already moved. Red lines on the orbital image indicate the approximate field of view of what is seen in the Chang’e-3 lander panorama.

Although Yutu is only about 150 cm wide – which is the same as the pixel size – it shows up in the NAC images for two reasons.

“The solar panels are very effective at reflecting light so the rover shows up as two bright pixels, and the Sun is setting thus the rover casts a distinct shadow (as does the lander),” says NASA in a statement.

In a historic first for China, the Chang’e-3 spacecraft safely touched down on the Moon at Mare Imbrium near the Bay of Rainbows nearly seven weeks ago on Dec. 14, 2013.

Seven hours later, the piggybacked 140 kg Yutu robot drove off a pair of ramps, onto the Moon and into the history books.

Yutu was about 10 meters away from the 1200 kg stationary lander when the lander panoramic images were taken.

The lander and Yutu were just completing their 1st Lunar Day of explorations when the LROC images were taken, and entered their first period of hibernation soon thereafter on Dec. 25 (Christmas Day) and Dec 26 respectively coinciding with the start of their 1st Lunar Night.

Both spacecraft awoke and functioned well during their 2nd Lunar Day, which just ended.

However, Yutu’s future mission is now in jeopardy following a serious mechanical anomaly this past weekend as both vehicles entered their 2nd hibernation period.

Apparently one of the solar panels did not fold back properly – perhaps due to dust accumulation – and its instruments may not survive.

Read my full story for complete details – here.

Yutu’s fate will remain unknown until the 3rd Lunar Day starts around Feb. 8 or 9.

So, What’s the terrain like at the Mare Imbrium landing site?

Chang’e-3 landed on a thick deposit of volcanic material.

“A large scale wrinkle ridge (~100 km long, 10 km wide) cuts across the area and was formed as tectonic stress caused the volcanic layers to buckle and break along faults. Wrinkle ridges are common on the Moon, Mercury and Mars,” says Robinson.

“The landing site is on a blue mare (higher titanium) thought to be about 3.0 billion years old.”

Older red mare about from 3.5 billion years is only 10 km to the north, he notes.

See our Chang’e-3 color panoramas now featured at NBC News and Space.com

China is only the 3rd country in the world to successfully soft land a spacecraft on Earth’s nearest neighbor after the United States and the Soviet Union.

Stay tuned here for Ken’s continuing Chang’e-3, Orion, Orbital Sciences, SpaceX, commercial space, LADEE, Mars and more news.

Ken Kremer

LRO LROC Wide angle camera (WAC) color (689 nm, 415 nm, 321 nm) overlain on WAC sunset BW image. Note the proximity of the landing site to a contact between red and blue maria.  Credit: NASA/GSFC/Arizona State University
NASA’s Lunar Reconnaissance Orbiter (LRO) LROC Wide angle camera (WAC) color (689 nm, 415 nm, 321 nm) overlain on WAC sunset BW image. Note the proximity of the landing site to a contact between red and blue maria. Credit: NASA/GSFC/Arizona State University
LRO spacecraft (top) protected by gray colored blankets is equipped with 7 science instruments located at upper right side of spacecraft. Payload fairing in background protects the spacecraft during launch and ascent. Credit: Ken Kremer
NASA’s LRO spacecraft (top) protected by gray colored blankets is equipped with 7 science instruments located at upper right side of spacecraft. LRO is piggybacked atop NASA’s LCROSS spacecraft. Payload fairing in background protects the spacecraft during launch and ascent on Atlas V rocket. Credit: Ken Kremer

Some Ideas on Where the ‘Jelly Donut’ Rock on Mars Came from — and no, it’s not a mushroom

This before-and-after pair of images of the same patch of ground in front of NASA's Mars Exploration Rover Opportunity 13 days apart documents the arrival of a bright rock onto the scene. Credit: NASA/JPL-Caltech/Cornell Univ./Arizona State Univ.

Hoo boy. Just mention the word “mystery” in conjunction with the planet Mars and all sorts of folks come out of the woodwork. Some start talking about silicon-based alien life forms or Mars-based reptiles or projectiles being tossed by little green men. The latest is that there’s an exotic mushroom on Mars, and this idea has sparked a lawsuit against NASA.

This all started when a strange rock suddenly appeared in photos from the Opportunity rover in a spot where photos taken just 12 sols (Mars days) earlier showed no rock. Mission principal investigator Steve Squyres talked about it during the recent 10-year anniversary celebration for the rover.

“It appeared,” Squyres said during the event. “It just plain appeared and we haven’t driven over that spot.”

They’ve named the rock “Pinnacle Island,” and Squyres and the Mars Exploration Rover team think the most likely scenario is that the rover actually dislodged the rock with its wheels and flicked it to a new spot as the rover was turning. “We had driven a meter or two away from here and somehow maybe one of the wheels managed spit it out of the ground,” Squyres said. “That’s the more likely theory.”

A colorized version of the rock called Pinnacle Island. Credit: NASA/JPL, color by Stuart Atkinson.
A colorized version of the rock called Pinnacle Island. Credit: NASA/JPL, color by Stuart Atkinson.

Another idea is that the rock is a piece of ejecta – a piece of rock which plunked down near the rover after being blasted out of the ground by a nearby meteoroid impact.

An idea favored by our readers here on Universe Today is that it possibly was a meteorite, dropping in from space and landing near the rover. Another thought is that since Opportunity is currently at Solander Point, a mountain of sorts, the rock may have rolled down to its new spot from a higher outcrop.

We checked in with Steve Squyres to see if there any new possibilities and he said the team thoughts on the rock’s appearance are the same as they were last week.

“We think the most likely hypothesis is that it was dislodged by the rover wheels from a location that may currently be obscured by the solar arrays,” he said via email.

Squyres described the rock as “white around the outside, in the middle there’s low spot that is dark red. It looks like a jelly donut,” and said it’s like nothing they’ve ever seen before on Mars.

Then things got weird. We received an email this week from neurologist and self-proclaimed astrobiologist Dr. Rhawn Joseph, of the Journal of Cosmology fame who we’ve previously written about.

He has filed a lawsuit in the US District Court Northern District of California claiming the white rock is biological in nature and is seeking an order forcing NASA, Administrator Charles Bolden, and others including Squyres to “examine a biological specimen on Mars” and that NASA is failing to investigate the rock thoroughly enough.

Joseph is petitioning the Federal Court for a writ of mandamus to “compel and order” NASA to “perform a public, scientific, and statutory duty which is to closely photograph and thoroughly scientifically examine and investigate a putative biological organism which was identified (and thus discovered) by Petitioner.”

From the lawsuit:

“Petitioner immediately recognized that bowl-shaped structure, hereafter referred to as Sol 3540,resembling a mushroom-like fungus, a composite organism consisting of colonies of lichen and cyanobacteria, and which on Earth is known as Apothecium.”

“When examined by Petitioner the same structure in miniature was clearly visible upon magnification and appears to have just germinated from spores.”

(Yeah, we’ve discussed previously the problems with zooming in on rocks on Mars – people start seeing crazy things).

For one thing, this is a rock. A rock. Squyres has said Pinnacle Island is very high in sulfur and magnesium, with twice as much manganese as anything else they’ve seen on Mars.

Second, the rover team is already throwing everything they’ve got at this rock.

“We are as we speak situated with the rover, with its instruments, making measurements on this rock. We’ve taken pictures of both the donut part and the jelly part,” Squyres said during the 10-year anniversary event.

Third, Joseph is not the “discoverer” of this rock. The MER team is and they’ve given full disclosure, talking frequently about the rock and posting all the images they’ve taken of the rock available for anyone to peruse.

So, where did this rock come from?

Of course, the folks from UnmannedSpaceflight.com have been discussing this rock before anyone else, since December when the images were first downloaded from the rover and put on NASA’s rover raw images website.

They’ve offered a few ideas, but this image from sol 3544 pointed out by “marsophile” on the forum might be the most compelling:

A disturbed area near the Opportunity rover that could be the spot where 'Pinnacle Island' came from. Credit: NASA/JPL.
A disturbed area near the Opportunity rover that could be the spot where ‘Pinnacle Island’ came from. Credit: NASA/JPL.

There appears to hole in the ground where a rock may have previously been.

Another set of images submitted by Universe Today reader Yuksel Kenaroglu highlights a possible location where the rock may have come from, but changes in lighting might just be making things look different in the two images:

Two images from the Opportunity rover from Sol 3528 (right) and Sol 3540 showing possible location of where the 'Jelly Donut' rock came from. Image credit: Credit: NASA/JPL-Caltech/Cornell Univ./Arizona State Univ., notation via Yuksel Kenaroglu.
Two images from the Opportunity rover from Sol 3528 (right) and Sol 3540 showing possible location of where the ‘Jelly Donut’ rock came from. Image credit: Credit: NASA/JPL-Caltech/Cornell Univ./Arizona State Univ., notation via Yuksel Kenaroglu.

Joseph said he wants “A) 100 high resolution close-up infocus photos of the specimen identified in Sol 3540, at various angles, from all sides, and from above down into the “bowl” of the specimen, and under appropriate lighting conditions which minimize glare. B) Take a minimum of 24 microscopic in-focus images of the exterior, lip, walls, and interior of the specimen under appropriate lighting conditions. C) NASA, and the rover team must make public and supply Petitioner with all high resolution photos and images of that specimen as demanded in A and B.”

By the way, You can see all the images anytime here,
from the microscopic imager and all other eight cameras on the rover

Surely, Squyres and the MER team would like nothing better than to solve the mystery of how this rock appeared and just like the Mars flower, and the piece of plastic there’s very little likelihood that biology plays any role in this rock an how it suddenly appeared.

If you want to see Joseph’s lawsuit, PopSci has it online.

What Is The Future Of Our Sun?

What Is The Future Of Our Sun?

Who knows what the future holds for our Sun? Dr. Mark Morris, a professor of astronomy at UCLA sure knows. Professor Morris sat down with us to let us know what we’re in for over the next few billions years.

“Hi, I’m Professor Mark Morris. I’m teaching at UCLA where I also carry out my research. I work on the center of the galaxy and what’s going on there – in this fabulous arena there, and on dying stars – stars that have reached the end of their lifetime and are putting on a display for us as they do so.”

What is the future of our sun?

“Well, there’s every expectation that in about 5 billion more years, that our sun will swell up to become a red giant. And then, as it gets larger and larger, it will eventually become what’s called an asymptotic giant branch star – a star whose radius is just under the distance between the sun and the Earth – one astronomical unit in size. So the Earth will be literally skimming the surface of the red giant sun when it’s an asymptotic giant branch star.”

“A star that big is also cool because they’re cold – red hot versus blue hot or yellow hot like our sun. Because it’s cold, a red giant star at its surface layers can keep all of its elements in the gas phase. So some of the heavier elements – the metals and the silicates – condense out as small dust grains, and when these elements condense out as solids, then radiation pressure from this very luminous giant star pushes the dust grains out. That may seem like a minor issue, but in fact these dust grains carry the gas with them. And so the star literally expels its atmosphere, and goes from a red giant star to a white dwarf, when finally the core of the star is exposed. Now, as it’s doing this, that hot core of the star is still very luminous and lights up through a fluorescent process, this out-flowing envelope, this atmosphere that was once a star, and that’s what produces these beautiful displays that are called planetary nebulae.”

“Now, planetary nebulae can be these beautiful round, spherical objects, or they can be bipolar, which is one of the mysteries that we’re working here is trying to understand why, at some stage, a star suddenly becomes axisymmetric – in other words, is sending out is’s atmosphere in two diametrically opposed directions predominantly, rather than continuing to lose mass spherically.”

Planetary Nebula
Planetary Nebula M2-9 (Credit: Bruce Balick (University of Washington), Vincent Icke (Leiden University, The Netherlands), Garrelt Mellema (Stockholm University), and NASA)

“We can’t invoke rotation of the star – that would be one way to get a preferred axis, but stars don’t rotate fast enough. If you take the sun and let it expand to become a red giant, then by the conservation of angular momentum, it literally won’t be spinning at all. It’ll be spinning so slowly that it’ll literally have no effect. So we can’t invoke spin, so there must be something going on deep down inside the star, that when you finally expose some rapidly spinning core, it can have an effect.”

“Or, all of the stars that we see as planetary nebula can have binary companions, that could be massive planets or relatively low mass stars that themselves can impose an angular momentum orientation on the system. This is in fact an idea that I’ve been championing for decades now, and it has some traction. There’s a lot of planetary nebula nuclei, the white dwarves, that seem to have companions near them that are suspect for having been responsible for helping strip the atmosphere of the mass-losing red giant star but also providing a preferred axis along which the ejected matter can flow.”

Simply Breathtaking Night Sky Timelapse: “Huelux” by Randy Halverson

An aurora behind a building storm. From the timelapse 'Huelux.' Credit and copyright: Randy Halverson.

Regular readers of Universe Today will be well-acquainted with the photography and timelapse work of Randy Halverson. He’s just released his latest timelapse and in a word, it is breathtaking. Aurora, thunderstorms — sometimes both at once — and, of course, stunning views of the night sky.

Randy shot the footage during April-November 2013 in South Dakota, Wyoming and Utah. “The weather in 2013 made it difficult for me to get some of the shots I wanted,” Randy said on Vimeo. “There were many times I planned to shoot the Milky Way or Aurora, and the clouds would roll in. But that also allowed me to get more night storm timelapse than I have any other year.”

He added that the aurora sometimes appeared without warning. In the video, be on the lookout for slow and fast moving satellites, quick meteors and slower moving airplanes. “The meteors are hard to see in timelapse, but you may see a quick flash because they only last one frame,” he said. “If you see a light moving across the sky, it is either an airplane or satellite, not a meteor.”

Sit back, put this on full screen and full sound and take a well-deserved break from your day!

Thanks once more to Randy Halverson for continuing to share his handiwork! Find out more about this timelapse at Randy’s website, Dakotalapse.

Huelux from Randy Halverson on Vimeo.

Video: These Children from Greece (and Poland) Helped Wake Up the Rosetta Spacecraft

An artist concept of the Philae lander on comet 67P/Churyumov-Gerasimenko. Credit: Astrium - E. Viktor/ESA

The European Space Agency asked for help in waking up the Rosetta spacecraft from 31 months of deep-space hibernation, and sponsored a fun video contest. The votes are in and the winning video comes from the 1,002 children of the Ellinogermaniki Agogi Primary School in Greece. Not only is the video heartwarming, but original music was composed using a “3/2 time signature symbolizing the five gravity assists that Rosetta got from the Earth and Mars. Theme ends with a perfect 5th (interval ratio 3:2) symbolizing Jupiter (5th planet), Rosetta’s ultimate orbit point.”

Wow.

There were 218 entries and 75,000 people voted. Entries came in from notables like Chris Hadfield, Bill Nye, and singer Tasmin Archer.

“We were truly impressed by the effort that all of you put into your videos, from getting your pets, friends and families involved and constructing fantastic model Rosetta spacecraft,”ESA said, “to storyboarding brilliant stop-motion animations with Lego, and writing entire songs and choreographing dance routines for dozens or even hundreds of passionate Rosetta fans.”

The top ten vote-getting videos were transmitted out to Rosetta via one of ESA’s deep-space tracking stations, and the top two video creators are invited to the control center in Darmstadt, Germany for when the Philae lander attempts landing on comet 67P/Churyumov–Gerasimenko in November 2014 after latching on with a harpoon. The second, equal award was given to Józef Dobrowolski, aged 17 student from Ostroleka, Poland, who is from the III Secondary School. He worked on his video himself, and he’s passionate about astronomy and started his hobby with observing the Perseid meteor shower:

You can see all ten winning videos here, or see a mashup of submitted videos, below.

Greedy Galaxies Gobbled Gas, Stalling Star Formation Billions Of Years Ago

Arp 147 contains a spiral galaxy (right) that collided with an elliptical galaxy (left), triggering a wave of star formation. Credit: X-ray: NASA/CXC/MIT/S.Rappaport et al, Optical: NASA/STScI

Like millionaires that burn through their cash too quickly, astronomers have found one factor behind why compact elliptical galaxies stopped growing stars about 11 billion years ago: they ate through their gas reserves.

The revelation comes as researchers released a new evolutionary track for compact elliptical galaxies that stopped their star formation when the universe was just three billion years old. When these galaxies ran out of gas, some of them cannibalized smaller galaxies to create giant elliptical galaxies. The “burned-out”galaxies have stars crowding 10 to 100 times more densely than elliptical galaxies formed more recently through a different evolutionary track.

“We at last show how these compact galaxies can form, how it happened, and when it happened. This basically is the missing piece in the understanding of how the most massive galaxies formed, and how they evolved into the giant ellipticals of today,” stated Sune Toft, who led the study and is a researcher at the Dark Cosmology Center at the Niels Bohr Institute in Copenhagen.

“This had been a great mystery for many years, because just three billion years after the Big Bang we see that half of the most massive galaxies have already completed their star formation.”

How massive elliptical galaxies evolved in about 13 billion years. Credit: NASA, ESA, S. Toft (Niels Bohr Institute), and A. Feild (STScI)
How massive elliptical galaxies evolved in about 13 billion years. Credit: NASA, ESA, S. Toft (Niels Bohr Institute), and A. Feild (STScI)

The team got a snapshot of these galaxies’ evolution by looking at a representative sample with the Hubble Space Telescope, specifically through the Cosmic Assembly Near-Infrared Deep Extragalactic Legacy Survey (CANDELS) and a spectroscopic survey called 3D-HST. To find out how old the stars were, they combined the Hubble work with data gathered from the  Spitzer Space Telescope and the Subaru Telescope in Hawaii.

Next, they examined ancient, fast-star-forming submillimeter galaxies with data gathered from a range of space and ground-based telescopes.

The Hubble Space Telescope. image credit: NASA, tweaked by D. Majaess.
The Hubble Space Telescope. image credit: NASA, tweaked by D. Majaess.

“This multi-spectral information, stretching from optical light through submillimeter wavelengths, yielded a full suite of information about the sizes, stellar masses, star-formation rates, dust content, and precise distances of the dust-enshrouded galaxies that were present early in the universe,” Hubble’s news center stated.

The group found that that the submillimeter galaxies were likely “progenitors” of compact elliptical galaxies, as they share predicted characteristics of the ancestors. Further, researchers calculated that starbursts in submillimeter galaxies only went on for about 40 million years before the galaxies ran out of gas.

You can read the results in the Feb. 20 edition of the Astrophysical Journal or in prepublished version in Arxiv.

Source: Hubble News Center

NEOWISE Spots Mars-Crossing Comet

NASA's NEOWISE Mission takes aim at Comet A1 Siding Spring on January 16th, 2014 when the comet was 571 million kilometres distant. Credit: NASA/JPL-Caltech

One of the big ticket astronomical events of 2014 will be the close passage of Comet C/2013 A1 Siding Spring past the planet Mars in October 2014. Discovered just over a year ago from the Australian-based Siding Spring Observatory, this comet generated a surge of excitement in the astronomical community when it was discovered that it was going to pass very close to the planet Mars in late 2014.

Now, a fleet of spacecraft are poised to study the comet in unprecedented detail. Some of the first space-based observations of the comet have been conducted by NASA’s Hubble Space Telescope and the recently reactivated NEOWISE mission. And although the comet may not look like much yet in the infrared eyes of NEOWISE, its estimated 4 kilometre in diameter nucleus is already active and shedding about 100 kilograms of dust per second.

And although an impact has been since ruled out, it’s that dust that may present a hazard for Mars orbiting spacecraft, as well as a unique scientific observing opportunity.

“Our plans for using spacecraft at Mars to observe Comet A1 Siding Spring will be coordinated with plans for how the orbiters will duck and cover, if we need to do so that,” said NASA/JPL Mars Exploration Program chief scientist Rich Zurek.

The 2014 passage of Comet A1 Siding Spring through the inner solar system. Credit: NASA/JPL-Caltech
The 2014 passage of Comet A1 Siding Spring through the inner solar system. Credit: NASA/JPL-Caltech

Comet A1 Siding Spring is projected to pass within just 138,000 kilometres of Mars on October 19th, 2014. This is one-third the Earth-Moon distance, and 10 times closer than the closest recorded passage of a comet by the Earth, which was Comet D/1770 Lexell in the late 18th century. The comet will also miss the Martian moons of Phobos and Deimos, which have the closest orbits of any moons in the solar system at just 5,989 and 20,063 kilometres above the surface of Mars, respectively.

Assets in orbit around the Red Planet are also slated to observe the close approach and passage of Comet A1 Siding Spring, as well as any extraterrestrial meteor shower that its dust may generate.

“We could learn about the nucleus – its shape, its rotation, whether some areas on its surface are darker than others,” Zurek said in a recent NASA/JPL press release.

The rovers Curiosity and Opportunity are currently active on the surface of Mars. Above in orbit, we’ve got the European Space Agency’s Mars Express, and NASA’s Mars Odyssey and the Mars Reconnaissance Orbiter (MRO).  These will be joined by India’s Mars Orbiter Mission and NASA’s Mars Atmosphere and Volatile Evolution (MAVEN) spacecraft just weeks prior to the comet’s passage.

“A third aspect for investigation could be what effect the infalling particles have on the upper atmosphere of Mars,” Zurek said. “They might heat it and expand it, not unlike the effect of a global dust storm.”

Just last year, Mars based spacecraft caught sight of the ill-fated sungrazer Comet C/2012 S1 ISON as it passed Mars. But that dim passage yielded a scant pixel-sized view in the eyes of MRO’s HiRISE camera; Comet A1 Siding Spring will pass 80 times closer than Comet ISON and could yield a view of its nucleus dozens of pixels across.

Though the tenuous Martian atmosphere will shield to surface rovers from any micro-meteoroid impacts, they may also be witness to a surreptitious meteor shower from the debris shed by the comet, a first seen from the surface of another world.

But engineers will also be assessing the potential hazards that said particles may posed to spacecraft orbiting Mars as well.

“It’s way too early for us to know how much of a threat Siding Spring will be to our orbiters,” said JPL’s Mars Exploration Program chief engineer Soren Madsen recently. “It could go either way. It could be a huge deal or it could be nothing – or anything in between.”

In a worst case scenario, Mars orbiting spacecraft would be shuttered and oriented to “shelter in place” as the dust from the comet passes. There’s precedent for this in Earth orbit, as precious assets such as the Hubble Space Telescope were closed for business during the Leonid meteor storm of 1998.

“How active will Siding Spring be in April and May? We’ll be watching that,” Madsen continued. “But if the red alarm starts sounding in May, it would be too late to start planning how to respond. That’s why we’re doing what we’re doing right now.”

Comet A1 Siding Spring was the first comet discovered in 2013 at 7.2 Astronomical Units (AUs) distant. From our Earth based perspective, the comet will reach opposition on August 25th at 0.96 AU from the Earth, and approach 7’ from Mars on October 19th in the constellation Ophiuchus in evening skies. The comet reaches perihelion just 4 days later, and is slated to be a binocular comet around that time shining at magnitude +8.

The comet nucleus itself is moving in a retrograde orbit relative to Mars. Particles from A1 Siding Spring will slam into the atmosphere of Mars — and any spacecraft that happens to be in their way — at a velocity of 56 kilometres per second. For context, the recent January Quadrantids have a more sedate atmospheric impact velocity of 41 kilometres a second.

The unfolding 2014 drama of “Mars versus the Comet” will definitely be worth keeping an eye on… more to come!

Rosetta Is Happily Awake, But Comet Lander Will Slumber Until March

Artist's impression (not to scale) of the Rosetta orbiter deploying the Philae lander to comet 67P/Churyumov–Gerasimenko. Credit: ESA–C. Carreau/ATG medialab.

Now that Rosetta has (leisurely) arose from a 31-month slumber in space, the next step is to figure out how prepared the spacecraft is for its close encounter with a comet. Early indications show that the orbiting spacecraft is ready to go. Its lander, Philae, is still asleep and the plan isn’t to wake it up until March, ESA added.

In the initial wake-up stage for Rosetta, “We were most concerned about power, and seeing if the solar arrays were generating sufficient electricity to support the planned recommissioning activities,” stated Andrea Accomazzo, spacecraft operations manager. “But even though we were still 673 million km [418 million miles] from the Sun , we were getting enough power and the arrays appear to have come through hibernation with no degradation.”

An artist concept of the Philae lander on comet 67P/Churyumov-Gerasimenko.  Credit: Astrium - E. Viktor/ESA
An artist concept of the Philae lander on comet 67P/Churyumov-Gerasimenko. Credit: Astrium – E. Viktor/ESA

Other systems are happily coming online as planned. Three of the four reaction wheels, which control Rosetta’s position in space, are working perfectly (with the fourth expected to be reactivated in a few weeks.) Next up is making sure Rosetta’s memory storage is working well enough to shelve science and operations information, and pinning down the spacecraft’s orbit.

So Rosetta is doing well after 31 months. With that hurdle leapt, technicians will begin to think about waking up Philae and making sure that its 10 instruments are working. By February, you can follow updates regularly on the Rosetta blog (as well as on Universe Today, of course!)

Rosetta should reach Comet 67P/Churyumov-Gerasimenko in August, and will start snapping pictures of the comet in May if all goes to plan. Astronomers are eager to see what the comet will teach us about the early years of the solar system, since comets are considered leftovers of when our neighborhood formed.

Source: ESA

How Do You Stop A Spacecraft Microbe From Attacking Mars?

An artist's conception of the European Space Agency's ExoMars rover, scheduled to launch in 2018. Credit: ESA

When you have a Mars mission that is designed to search for life or life-friendly environments, it would be several shades of awkward if something biological was discovered — and it ended up being an Earth microbe that clung on for the ride. Beyond that, there’s the worry that an Earth microbe could contaminate the planet’s environment, altering or perhaps wiping out anything that was living there.

A recent European Space Agency post highlighted that agency’s efforts to keep Mars safe from its forthcoming ExoMars missions in 2016 or 2018. (And it also should be noted that NASA has its own planetary protection protocols, as well as other agencies.)

“We have a long-term programme at ESA – and also NASA – to regularly monitor and evaluate biological contamination in cleanrooms and on certain type of spacecraft,” stated Gerhard Kminek, ESA’s planetary protection officer. “The aim,” he added, “is to quantify the amount of biological contamination, to determine its diversity – finding out what is there using gene sequence analysis, and to provide long-term cold storage of selected samples.”

The process isn’t perfect, ESA admits, but the biological contamination that these scrutinized missions have is extraordinarily low compared to other Earthly manufacturing processes. There is, in fact, an obligation on the part of space-faring nations to keep planets safe if they signed on to the United Nations Outer Space Treaty. (That said, enforcement is a tricky legal issue as there is no international court for this sort of thing and that would make it hard to levy penalties.)

The NASA Curiosity rover in this undated photo inside the Jet Propulsion Laboratory's spacecraft assembly facility. The team did around 4,500 samplings during assembly for contamination.  Credit: NASA
The NASA Curiosity rover in this undated photo inside the Jet Propulsion Laboratory’s spacecraft assembly facility. The team did around 4,500 samplings during assembly for contamination. Credit: NASA

Spacefaring nations have international standards for biological contamination limits, and they also must monitor the “impact probability” of an orbital spacecraft smacking into the planet or moon below when they do maneuvers. Sometimes this means that spacecraft are deliberately crashed in one spot to prevent contamination elsewhere. A famous example is the Galileo mission to Jupiter, which was thrown into the giant planet in 2003 so it wouldn’t accidentally hit the ice-covered Europa moon.

Moving forward to ExoMars — the Mars orbiting and landing missions of 2016 and 2018 — ESA plans to perform about 4,500 samplings of each spacecraft to monitor biological contamination. This estimate came from the number performed at NASA on the Curiosity rover, which is trundling around Mars right now. Changes in processing, though, mean the ESA checks will take less time (presumably making it less expensive.)

For the curious, yes, planetary protection protocols would also apply during a “sample return” mission where soil or other samples are sent back to Earth. While that’s a little ways off, ESA also elaborated on the procedures it takes to keep spacecraft it creates safe from contamination.

A technician does a check for contamination on the ExoMars 2016 descent camera in December 2013. The test took place at the European Space Agency's European Space Research and Technology Centre in the Netherlands. Credit: ESA
A technician does a check for contamination on the ExoMars 2016 descent camera in December 2013. The test took place at the European Space Agency’s European Space Research and Technology Centre in the Netherlands. Credit: ESA

“Samples are acquired in various ways: air samplers collect a certain amount of air on a filter, while wipes dampened with ultra-pure water are run across space hardware or cleanroom surfaces. Swabs are used to sample smaller items such as payloads or electronics,” ESA stated.

“To quantify the biological contamination, the samples are then filtered onto culture plates and incubated for between seven hours and three days depending on the specific method used, to see how much turns up. Statistical analysis is used to assess the overall cleanroom or flight hardware ‘bioburden’, and check whether it falls within the required standard or if further measures are needed to reduce it.”

Sometimes a hardy survivor is found, which is scientifically interesting because investigators want to know how it made it. ESA has a database of these microbes, and NASA has records as well. In November, the agencies announced a new bacterium, Tersicoccus phoenicis, that so far has only been found in “cleanrooms” for NASA’s Mars Phoenix lander (near Orlando, Florida) and ESA’s Herschel and Planck observatories (in Kourou, French Guiana).

Source: ESA