Universe Today

December 19, 2011December 24, 2015 by Tammy Plotner

New NASA Probe – The Comet Harpoon

This is an artist's concept of a comet harpoon embedded in a comet. The harpoon tip has been rendered semi-transparent so the sample collection chamber inside can be seen. Credit: NASA/Chris Meaney/Walt Feimer

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It’s not easy to sample a comet. These outer solar system travelers speed around the inner solar system at 241,000 km/h (150,000 mph) – twisting and turning while spewing chunks of ice, dust and debris. To consider landing on one becomes a logistical nightmare, but how about shooting at it? Why not send a mission to rendezvous with these frozen, inhospitable rocks and insert a probe? A method like this could even mean a sample could be taken where a landing would be impossible!

Thanks to the work of scientists at NASA’s Goddard Space Flight Center in Greenbelt, Maryland, a new comet “harpoon” is being designed to make comet sample returns not only more efficient, but more detailed.

Roughly the size of a clothes closet, this syringe-like probe stands roughly two meters tall and will be inserted with a cross-bow like arrangement that will contact the surface of the comet. Positioned to fire vertically downward, this bow arrangement consists of a pair of truck leaf springs and 1/2 inch steel cable.. an arrangement which could fire up to a mile if pointed in the wrong direction! When it impacts, an electric winch will draw the bow back into position and eject the harpoon with 1,000 pounds of force at 100 feet per second.

So what would it be like to witness the harpooning of the cosmic whale? An explosive adventure, to be sure. Donald Wegel of NASA Goddard, lead engineer on the project, has been experimenting with the ballista and the core sample box in various impact environments. According to the press release, the resultant impact is something of a combination of rifle report and cannon blast.

CometHarpoon2 — This is a photo of the ballista testbed preparing to fire a prototype harpoon into a bucket of material that simulates a comet. Credit: NASA/Rob Andreoli

“We had to bolt it to the floor, because the recoil made the whole testbed jump after every shot,” said Wegel. “We’re not sure what we’ll encounter on the comet – the surface could be soft and fluffy, mostly made up of dust, or it could be ice mixed with pebbles, or even solid rock. Most likely, there will be areas with different compositions, so we need to design a harpoon that’s capable of penetrating a reasonable range of materials. The immediate goal though, is to correlate how much energy is required to penetrate different depths in different materials. What harpoon tip geometries penetrate specific materials best? How does the harpoon mass and cross section affect penetration? The ballista allows us to safely collect this data and use it to size the cannon that will be used on the actual mission.”

Studying comet core samples will provide researchers with important information on the original solar nebula and help us to further understand how life may have originated. “One of the most inspiring reasons to go through the trouble and expense of collecting a comet sample is to get a look at the ‘primordial ooze’ – biomolecules in comets that may have assisted the origin of life,” says Wegel. Comet sample return missions – such as the one from Wild 2 – have shown us that that amino acids exist in these inhospitable places, yet may have helped stimulate life here on Earth.

However, there’s more to the story than just searching out reasons for life… the biggest being the preservation of life itself. As we know, there’s always a possibility that a comet could impact Earth and create an extinction level event. By understanding comet composition, we can get a better grip on what we might need to do should a cataclysmic scenario rear its ugly head. For example, we’d know if a certain type of comet might tend to fragment – or another explode. “So the second major reason to sample comets is to characterize the impact threat,” according to Wegel. “We need to understand how they’re made so we can come up with the best way to deflect them should any have their sights on us.”

“Bringing back a comet sample will also let us analyze it with advanced instruments that won’t fit on a spacecraft or haven’t been invented yet,” adds Dr. Joseph Nuth, a comet expert at NASA Goddard and lead scientist on the project.

If we were to be in a movie, perhaps we might consider getting a comet sample through a method like drilling – but lack of gravity on these small, moving worlds isn’t going to allow that to happen. “A spacecraft wouldn’t actually land on a comet; it would have to attach itself somehow, probably with some kind of harpoon. So we figured if you have to use a harpoon anyway, you might as well get it to collect your sample,” says Nuth.

CometHarpoon3 — This is a demonstration of the sample collection chamber. Credit: NASA/Rob Andreoli

At the present, the design team is currently hard at work studying the harpoon’s reactions to different mediums – and what needs to be done to sample and collect what they might encounter. This isn’t easy considering they are working with a basic unknown.

“You can’t do this by crunching numbers in a computer, because nobody has done it before — the data doesn’t exist yet,” says Nuth. “We need to get data from experiments like this before we can build a computer model. We’re working on answers to the most basic questions, like how much powder charge do you need so your harpoon doesn’t bounce off or go all the way through the comet. We want to prove the harpoon can penetrate deep enough, collect a sample, decouple from the tip, and retract the sample collection device.”

Nothing will be left to chance, however. By creating multiple tips, collection devices and planning for different firing techniques and needs, the team is sure to make the most of their research dollars and the spacecraft that will be available to them. To further assist in their planning, they will also be able to use data from the current Rosetta mission and its lander, Philae, which will hook up with “67P/Churyumov-Gerasimenko” in 2014.

“The Rosetta harpoon is an ingenious design, but it does not collect a sample,” says Wegel. “We will piggyback on their work and take it a step further to include a sample-collecting cartridge. It’s important to understand the complex internal friction encountered by a hollow, core-sampling harpoon.” Even more information will be added from recent NASA mission, OSIRIS-REx (Origins, Spectral Interpretation, Resource Identification, Security — Regolith Explorer), which is an asteroid sample return mission. It will all add up to some very unique findings and one thing we do know is…

“Admiral? Thar’ be whales here…”

December 19, 2011December 24, 2015 by Bruce Dorminey

NASA Considers Sending a Telescope to Outer Solar System

ZEBRA (Zodiacal dust, Extragalactic Background and Reionization Apparatus) is a small, passively cooled optical to near-infrared instrument package that could be added to an outer solar system probe. Credit: NASA/JPL/Caltech

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Editors note — Science journalist and author Bruce Dorminey spoke to two NASA scientists about the possibility of mounting a telescope on a spacecraft for an outer planets mission.

Light pollution in our inner solar system, from both the nearby glow of the Sun and the hazy zodiacal glow from dust ground up in the asteroid belt, has long stymied cosmologists looking for a clearer take on the early Universe.

But a team at NASA, JPL and Caltech has been looking into the possibility of hitching an optical telescope to a survey spacecraft on a mission to the outer solar system.

Escaping our Inner Solar System’s Polluted Purple Haze

The idea is to use the optical telescope in cruise phase to get a better handle on extragalactic background light; that is, the combined optical background light from all sources in the Universe. They envision the telescope’s usefulness to kick in around 5 Astronomical Units (AU), about the distance of Jupiter’s orbit. The team then wants to correlate their data with ground-based observations.

One goal is to shed light on the early universe’s epoch of reionization. Reionization refers to the time when ultraviolet (UV) radiation from the universe’s first stars ionized the intergalactic medium (IGM) by stripping electrons from the IGM’s gaseous atoms or molecules. This period of reionization is thought to have taken place no later than 450 million years after the Big Bang.

ZEBRA, the Zodiacal dust, Extragalactic Background and Reionization Apparatus, is a NASA JPL concept that calls for a $40 million dollar telescope comprised of three optical/near-infrared instruments; consisting of a 3 cm wide-field mapper and a 15 cm high-resolution imager. However, NASA has yet to select the ZEBRA proposal for one of its missions.

But to learn more, we spoke with the ZEBRA Concept lead and instrument cosmologist Jamie Bock and astronomer Charles Beichman, both of NASA JPL and Caltech.

Dorminey: What is zodiacal light?

Beichman: It’s a bright source of diffuse light in our own solar system from dust grains that emit because they have been heated by the sun and are radiating by themselves
or reflect sunlight. If you go out on a very clear dark moonless light, you can see the band of this light from this dust. It follows the plane of the ecliptic. That dust mostly originates from material in the asteroid belt that gets ground up into little particles after some big collision.

Dorminey: What would getting past this zodiacal dust mean for observations?

Beichman: Imagine sitting in the Los Angeles basin and you’ve got all this smog and haze and you want to measure how clear the air is out at Palm Springs. You have to be able to subtract off all the haze between here and there and there’s just no way to do it with any accuracy. You have to drive out of the basin to get out of the smog.

Dorminey: How would this help in studying this extragalactic background?

Bock: The Extragalactic Background Light (EBL) measures the total energy density of light coming from outside our galaxy. This light gives the sum of the energy produced by stars and galaxies, and any other sources, over the history of cosmic time. The total background can be used to check if we correctly understand the formation history of galaxies. We expect a component of the background light from the first stars to have a distinct spectrum that peaks in the near-infrared; this can tell us how bright and how long the epoch was when the first stars were forming. Unfortunately, zodiacal light is much brighter than this background. But by going to the orbit of Jupiter, the zodiacal light is 30 times fainter than at Earth, and at the orbit of Saturn it is 100 times fainter.

Dorminey: Would you have to hitchhike on a NASA mission or could it be a partnership with another space agency, like ESA for instance?

Bock: We have been exploring the cheapest incremental cost approach, partnering with a NASA planetary mission. But we could partner with another space agency. The European Jupiter Icy Moons Explorer (formerly JGO) is now competing for the next L-class mission launch in the early 2020’s and is an attractive possibility for a contributed cruise-phase science instrument. Each approach comes with a different cost and partnership environment.

Dorminey: Is the prime driver for the EBL telescope to get beyond the zodiacal dust or does 5 AU also offer an observational advantage in terms of achieving faintness of magnitude?

Bock: There is an observing advantage due to the [darker solar system] background. With such a small telescope, we are not trying to exploit this benefit but future observatories could. We will measure the zodiacal brightness to Jupiter and beyond, and this may motivate astronomical observations with telescopes in the outer solar system in the future.

Dorminey: What sort of data downlink challenges would you encounter?

Bock: The data requirements are perhaps smaller than one might first expect, because our images are obtained with long [observational] integrations at moderate spatial resolution. For the planetary proposal we studied in detail, the total data volume was 230 gigabytes, with about 65 percent of this data being returned from Jupiter and out to Saturn. The telescope pointings operate autonomously.

Dorminey: What about radiation from Jupiter interfering with the optics and CCD cameras on the telescope?

Beichman: What you’d do is stop making the EBL observations while close to Jupiter. The radiation problems are significant, so you would only do observations before and after passing Jupiter.

background light — Panoramic view of the entire near-infrared sky reveals the distribution of galaxies beyond the Milky Way. The image is derived from the 2MASS Extended Source Catalog (XSC)--more than 1.5 million galaxies, and the Point Source Catalog (PSC)--nearly 0.5 billion Milky Way stars. Credit: Thomas Jarrett, et al/Caltech. Click image for more information.

Dorminey: What would your instruments do that NASA’s planned James Webb Space Telescope (JWST) wouldn’t?

Bock: JWST will likely detect the brightest first galaxies, and depending exactly how galaxies formed, will miss most of the total radiation due to the contribution of many faint galaxies. Measuring the extragalactic background gives the total radiation from all the galaxies and provides the total energy. Furthermore, we don’t need a large telescope; 15 cm is sufficient.

Dorminey: What about planetary science with the telescope?

Bock: Our instrument specializes in making low surface-brightness measurements. We made specific design choices to map the zodiacal dust cloud from the inner to the outer solar system. A 3-Dimensional view will let us trace the origins of interstellar dust to comets and asteroid collisions. We know there are Kuiper-belt objects beyond the orbit of Neptune, and it is likely there is dust associated with them as well.

Dorminey: How long would this telescope function?

Bock: After the prime observations complete, it would certainly be possible that the original team or an outside party could propose to operate the telescope. One exciting science case is parallax micro-lensing observations; observations that use the parallax between Earth and Saturn to study the influence of exo-planets orbiting the stars producing a micro-lensing event. Other science opportunities include maps of the Kuiper Belt in the near-infrared; stellar occultations by Kuiper Belt Objects; and mapping more EBL fields for comparison with other surveys.

Dorminey: How would the telescope’s initial observations potentially shake up theoretical cosmology?

Beichman: Whenever you do a measurement that’s a factor of a hundred times better than before, you always get a surprise.

December 19, 2011December 24, 2015 by Tammy Plotner

Incoming! Meteorite Shockwaves Could Set Off Martian Dust Avalanches

Artist's conception of an asteroid impact on Mars. (Image painted by William K. Hartmann, co-founder of the Planetary Science Institute, Tucson, Ariz.)

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They are headed toward the surface like a speeding freight train… and running ahead of them is a shockwave. Just like a loud sound can trigger a snow avalanche here on Earth, the shockwave of a meteorite crashing through the Martian atmosphere could trigger dust avalanches on the surface before an actual impact.

According to a study led by University of Arizona undergraduate student, Kaylan Burleigh, there is sufficient photographic evidence to prove that incoming meteorites are producing enough energy to impact the surface environment just as much as the strike. Mars’ thin atmosphere also contributes, since the lesser density means most meteorites survive the trip to the surface. “We expected that some of the streaks of dust that we see on slopes are caused by seismic shaking during impact,” said Burleigh. “We were surprised to find that it rather looks like shockwaves in the air trigger the avalanches even before the impact.”

MarsAvalanche1 — HiRISE image of the study area showing the central crater with two dagger-like features extending at an angle (red and blue arrows). Called scimitars, these features most likely resulted from shockwave interference just before impact. (Image: NASA/JPL-Caltech/The University of Arizona)

Spotting new craters happens frequently. Thanks to the HiRISE camera on board NASA’s Mars Reconnaissance Orbiter, researchers find up to twenty newly formed craters that measure between 1 and 50 meters (3 to 165 feet) each year. To perform their study, the team focused their attention on a grouping of five craters which formed at the same time. This quintuplet is located near the Martian equator, about 825 kilometers (512 miles) south of the boundary scarp of Olympus Mons. Earlier investigations of the area had revealed dark streaks which were surmised at the time to be landslides, but no one thought to credit them to an impact theory. The largest crater in the cluster measures 22 meters, or 72 feet across and the multiple formation is thought to have occurred due to a shattering of the meteor just ahead of final impact.

“The dark streaks represent the material exposed by the avalanches, as induced by the airblast from the impact,” Burleigh said. “I counted more than 100,000 avalanches and, after repeated counts and deleting duplicates, arrived at 64,948.”

As Burleigh took a closer look at the distribution of avalanches around the impact site, he noticed a lot of relative things, but the most important was a curved formation described as scimitars. This was a major clue as to how they were formed. “Those scimitars tipped us off that something other than seismic shaking must be causing the dust avalanches,” Burleigh said.

Just as a freight train sends a rumble before it arrives, so does the incoming meteor. By using computer modeling, the team was able to simulate how a shockwave could form and match the scimatar patterns to the HiRISE images. “We think the interference among different pressure waves lifts up the dust and sets avalanches in motion. These interference regions, and the avalanches, occur in a reproducible pattern,” Burleigh said. “We checked other impact sites and realized that when we see avalanches, we usually see two scimitars, not just one, and they both tend to be at a certain angle to each other. This pattern would be difficult to explain by seismic shaking.”

Because there are no plate tectonics, nor water erosion issues, these types of findings are very important to understanding how many Martian surface features are formed. “This is one part of a larger story about current surface activity on Mars, which we are realizing is very different than previously believed,” said Alfred McEwen, principal investigator of the HiRISE project and one of the co-authors of the study. “We must understand how Mars works today before we can correctly interpret what may have happened when the climate was different, and before we can draw comparisons to Earth.”

Original Story Source: University of Arizona News.

December 17, 2011December 24, 2015 by Ken Kremer

NASA Terminates Power, Locks Cargo Doors on Retiring Shuttle Discovery

In Orbiter Processing Facility-1 at NASA's Kennedy Space Center in Florida, space shuttle Discovery’s payload bay is moments away from being concealed from view as its doors swing shut with the aid of yellow-painted strongbacks, hardware used to support and operate the doors when the shuttle is not in space. Discovery was powered down and the doors were closed for the final time during Space Shuttle Program transition and retirement activities. Discovery is being prepared for public display at the Smithsonian’s National Air and Space Museum Steven F. Udvar-Hazy Center in Chantilly, Va., in 2012. Credit: NASA/Kim Shiflett

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Space Shuttle Discovery was powered down forever and the payload bay doors were locked tight for the final time on Friday, Dec. 16, by technicians at NASA’s Kennedy Space Center (KSC) in Florida.

Take a good last glimpse inside the retiring Discovery’s payload bay as the clamshell like doors seal off all indigenous US human spaceflight capability for several years at a minimum.

The historic “Power Down” came after both of the 60 foot long cargo bay doors were swung shut this morning for the last time inside the shuttle hanger known as Orbiter Processing Facility-1 (OPF-1) – in the shadow of the cavernous Vehicle Assembly Building (VAB).

Workers at KSC are in the final stages of the transition and retirement activities that will soon lead to Discovery departing her Florida launch pad forever on her final voyage. They are converting the orbiter from active duty flight status to display as a nonfunctional and stationary museum piece.

Kennedy Space Center Director Robert Cabana, a former space shuttle commander, formally marked the final power down and sealing of Discovery’s payload bay doors at a ceremony in OPF-1 with the skeleton force of remaining shuttle personnel engaged in the decommissioning efforts.

Discovery’s payload bay is glimpsed for the final time as its doors swing shut with the aid of yellow-painted strongbacks, hardware used to support and operate the doors when the shuttle is not in space. Discovery's doors were closed and the vehicle was powered down for the final time. Discovery is being prepared for public display at the Smithsonian’s National Air and Space Museum Steven F. Udvar-Hazy Center in Chantilly, Va., in 2012. Credit: NASA/Kim Shiflett

Discovery was the Fleet leader and NASA’s oldest orbiter having flown the most missions. All told Discovery soared 39 times to space from her maiden flight in 1984 to her last touchdown on the STS-133 mission in March 2011.

In between, Discovery deployed the iconic Hubble Space Telescope, launched the Ulysses solar probe and numerous other science satellites and Department of Defense surveillance platforms, conducted the first shuttle rendezvous with Russia’s Mir Space Station and delivered key components to the International Space Station including the last habitable module.

Discovery payload bay and doors sealed for History inside Orbiter Processing Facility-1 at KSC. Credit: NASA/Kim Shiflett

Discovery flew both ‘return to flight’ missions following the Challenger and Columbia tragedies as well as the second flight of Astronaut and Senator John Glenn, first American to orbit the Earth.

Discovery has been thoroughly cleansed and cleared of all hazardous materials in preparation for making the vehicle safe for public display at her new and final resting place, the Smithsonian’s National Air and Space Museum Steven F. Udvar-Hazy Center in Chantilly, Va..

Technicians re-installed the three power generating fuel cells after draining and purging all the toxic materials and fuels from the fuel lines and assemblies. Three replica space shuttle main engines were also installed last week.

The "vehicle powered" sign is momentarily lit as KSC technicians prepare to power down space shuttle Discovery for the last time. Credit: NASA/Kim Shiflett

The "vehicle powered" sign is turned off following the final power down of space shuttle Discovery. Credit: NASA/Kim Shiflett

In 2012, the 100 ton orbiter will be hoisted piggyback atop NASA’s specially modified 747 carrier aircraft. Discovery will take flight for the last time in April and become the center piece at her new home inside the Smithsonian’s spaceflight exhibition in Virginia.

To make way for Discovery, the prototype shuttle Enterprise currently housed at the Smithsonian will be hauled out and flown to New York City for display at the Intrepid, Sea, Air and Space Museum.

Altogether, Discovery spent 365 days in space during the 39 missions, orbited Earth 5,830 times and traveled 148,221,675 miles during a career spanning 27 years.

There is nothing on the horizon comparable to NASA’s Space Shuttles. Their capabilities will be unmatched for several decades to come.

America is now totally dependent on the Russians for launching US astronauts to space until privately built ‘space taxis’ from firms like SpaceX, Boeing and Sierra Nevada are ready in perhaps 4 to 6 years.

Liftoff of Space Shuttle Discovery on the STS-133 mission from the Kennedy Space Center on 39th and historic final flight to space. Credit: Ken Kremer

Space Shuttle Discovery rolling to the Vehicle Assembly Building during summer 2011 as it's being processed for retirement before transport to permanent home at the Smithsonian Air & Space Museum in Virginia. Thrusters, OMS pods and main engines were removed for cleaning of toxic components and fuels. Credit: Ken Kremer

December 17, 2011December 24, 2015 by Steve Nerlich

Astronomy Without A Telescope – Special Relativity From First Principles

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Einstein’s explanation of special relativity, delivered in his 1905 paper On the Electrodynamics of Moving Bodies focuses on demolishing the idea of ‘absolute rest’, exemplified by the theoretical luminiferous aether. He achieved this very successfully, but many hearing that argument today are left puzzled as to why everything seems to depend upon the speed of light in a vacuum.

Since few people in the 21st century need convincing that the luminiferous aether does not exist, it is possible to come at the concept of special relativity in a different way and just through an exercise of logic deduce that the universe must have an absolute speed – and from there deduce special relativity as a logical consequence.

The argument goes like this:

1) There must be an absolute speed in any universe since speed is a measure of distance moved over time. Increasing your speed means you reduce your travel time between a distance A to B. A kilometre walk to the shops might take 25 minutes, but if you run it might take only 15 minutes – and if you take the car, only 2 minutes. At least theoretically you should be able to increase your speed up to the point where that travel time reaches zero – and whatever speed you are at when that happens will represent the universe’s absolute speed.

2) Now consider the principle of relativity. Einstein talked about trains and platforms to describe different inertial frame of references. So for example, you can measure someone throwing a ball forward at 10 km/hr on the platform. But put that someone on the train which is travelling at 60 km/hr and then the ball measurably moves forward at nearly 70 km/hr (relative to the platform).

3) Point 2 is a big problem for a universe that has an absolute speed (see Point 1). For example, if you had an instrument that projected something forward at the absolute speed of the universe and then put that instrument on the train – you would expect to be able to measure something moving at the absolute speed + 60 km/hr.

4) Einstein deduced that when you observe something moving in a different frame of reference to your own, the components of speed (i.e. distance and time), must change in that other frame of reference to ensure that anything that moves can never be measured moving at a speed greater than the absolute speed.

Thus on the train, distances should contract and time should dilate (since time is the denominator of distance over time).

The effect of relative motion. Measurable time dilation is negligible on a train moving past a platform at 60 km/hr, but increases dramatically if that train acquires the capacity to approach the speed of light. Time (and distance) will change to ensure that light speed is always light speed, not light speed + the speed of the train.

And that’s it really. From there one can just look to the universe for examples of something that always moves at the same speed regardless of frame of reference. When you find that something, you will know that it must be moving at the absolute speed.

Einstein offers two examples in the opening paragraphs of On the Electrodynamics of Moving Bodies:

the electromagnetic output produced by the relative motion of a magnet and an induction coil is the same whether the magnet is moved or whether the coil is moved (a finding of James Clerk Maxwell‘s electromagnetic theory) and;
the failure to demonstrate that the motion of the Earth adds any additional speed to a light beam moving ahead of the Earth’s orbital trajectory (presumably an oblique reference to the 1887 Michelson-Morley experiment).

In other words, electromagnetic radiation (i.e. light) demonstrated the very property that would be expected of something which moved at the absolute speed that it is possible to move in our universe.

The fact that light happens to move at the absolute speed of the universe is useful to know – since we can measure the speed of light and hence we can then assign a numerical value to the universe’s absolute speed (i.e. 300,000 km/sec), rather than just calling it c.

Further reading:
None! That was AWAT #100 – more than enough for anyone. Thanks for reading, even if it was just today. SN.

December 17, 2011April 26, 2016 by Jon Voisey

How Can Growing Galaxies Stay Silent?

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Beginning around 2005, astronomers began discovering the presence of very large galaxies at a distance of around 10 billion lightyears. But while these galaxies were large, they didn’t appear to have a similarly large number of formed stars. Given that astronomers expect galaxies to grow through mergers and mergers tend to trigger star formation, the presence of such large, undeveloped galaxies seemed odd. How could galaxies grow so much, yet have so few stars?

One of the leading propositions is that the galaxies have undergone frequent mergers, but each one was very small and didn’t encourage large scale star formation. In other words, instead of mergers between galaxies of similar size, large galaxies developed quickly and early in the universe, and then tended to accumulate through the integration of minor, dwarf galaxies. While this solution is straightforward, testing it is difficult since the galaxies in question are at vast distances and detecting the minor galaxies as they are devoured would require exceptional observations.

Seeking to test this hypothesis, a team of astronomers led by Andrew Newman from the California Institute of Technology combined observations from Hubble and the United Kingdom Infra-Red Telescope (UKIRT), to search for these diminutive companions. The team examined over 400 galaxies that didn’t display signs of active star formation (called “quiet” galaxies) in search of possible companion galaxies from distances of 10 billion light years to a relatively close 2 billion lightyears in order to determine how this minor merger rate has evolved over time.

From their study, they determined that around 15% of quiet galaxies had a nearby counterpart that had at least 10% the mass of the larger galaxy. This took into account the possibility that some galaxies may have been more distant but along the line of sight by ensuring that both galaxies had similar redshifts. Over time, the partner galaxies became rarer suggesting that they were becoming rarer as more were consumed by the larger brethren. Using this as a rate at which mergers must occur, the team was able to answer the question of whether or not these minor mergers could account for the galaxy growth discovered six years earlier.

For galaxies closer than a distance of roughly 8 billion light years, the rate of minor mergers was able to completely explain the overall growth of galaxies. However, for the growth rate of galaxies at times earlier than this, such minor mergers could only account for around half of the apparent growth.

The team proposes several reasons this may be the case. Firstly, many of the basic assumptions could be flawed. Teams may have overestimated the sizes of the massive galaxies, or underestimated the rate of star formation. These key properties were often derived from photometric surveys which are not as reliable as spectroscopic observations. In the future, if better observations can be made, these values may be revised and the problem may resolve itself. The other option is that there are simply additional processes at work that astronomers have yet to understand. Either way, the question of how growing galaxies avoid advertising their growth is unanswered.

December 16, 2011January 12, 2016 by Nancy Atkinson

Best Look Yet of Comet Lovejoy’s Slingshot Around the Sun

There have been some great images and video of Comet Lovejoy’s close encounter with the Sun, but this video put together by Scott Wiessinger from Goddard Spaceflight Center combines and zooms in on the best views from the Solar Dynamics Observatory (SDO), which adjusted its cameras in order to watch the trajectory.

The first part of the video from SDO, (taken in 171 Angstrom wavelength, which is typically shown in yellow) was filmed on Dec 15, 2011 showing Comet Lovejoy moving in toward the Sun, with its tail “wiggling” from its interaction with the solar wind. The second part of the clip shows the comet exiting from behind the right side of the Sun, after an hour of travel through its closest approach.

No time travel with this slingshot around the Sun, but it is amazing to be able to follow this comet’s journey so closely!

December 16, 2011December 24, 2015 by Tammy Plotner

Aliens Hanging Out in the Kuiper Belt? We Could See the Light from their Cities

Astronaut photograph ISS025-E-9858 was acquired on October 28, 2010, with a Nikon D3S digital camera using a 16 mm lens, and is provided by the ISS Crew Earth Observations experiment and Image Science & Analysis Laboratory, Johnson Space Center. The image was taken by the Expedition 25 crew.

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When it comes to searching for ET, current efforts have been almost exclusively placed in picking up a radio signal – just a small portion of the electromagnetic spectrum. Consider for a moment just how much lighting we here on Earth produce and how our “night side” might appear as viewed from a telescope on another planet. If we can assume that alternate civilizations would evolve enjoying their natural lighting, wouldn’t it be plausible to also assume they might develop artificial lighting sources as well?

Is it possible for us to peer into space and spot artificially illuminated objects “out there?” According to a new study done by Abraham Loeb (Harvard), Edwin L. Turner (Princeton), the answer is yes.

For gathering light, the array of Earthly telescopes now at science’s disposal are able to confidently observe a light source comparable in overall brightness to a large city — up to a certain distance. Right now astronomers are able to measure the orbital parameters of Kuiper belt objects (KBOs) with the greatest of precision by their observed flux and computing their changing orbital distances.

However, is it possible to see light if it were to occur on the dark side? Loeb and Turner say that current optical telescopes and surveys would have the ability to see this amount of light at the edge of our Solar System and observations with large telescopes can measure a KBOs spectra to determine if they are illuminated by artificial lighting using a logarithmic slope (sunlit object would exhibit alpha=(dlogF/dlogD) = -4, whereas artificially-illuminated objects should exhibit alpha = -2.)

“Our civilization uses two basic classes of illumination: thermal (incandescent light bulbs) and quantum (light emitting diodes [LEDs] and fluorescent lamps)” Loeb and Turn write in their paper. “Such artificial light sources have different spectral properties than sunlight. The spectra of artificial lights on distant objects would likely distinguish them from natural illumination sources, since such emission would be exceptionally rare in the natural thermodynamic conditions present on the surface of relatively cold objects. Therefore, artificial illumination may serve as a lamppost which signals the existence of extraterrestrial technologies and thus civilizations.”

Spotting this illumination difference in the optical band would be tricky but by calculating the observed flux from solar illumination on Kuiper Belt Objects with a typical albedo, the team is confident that existing telescopes and surveys could detect the artificial light from a reasonably brightly illuminated region, roughly the size of a terrestrial city, located on a KBO. Even though the light signature would be weaker, it would still carry the dead give-away – the spectral signature.

However, we currently don’t expect there to be any civilizations thriving at the edge of our solar system, as it is dark and cold out there.

But Loeb has posed that possibly planets ejected from other parent stars in our galaxy may have traveled to the edge of our Solar System and ended up residing there. Whether a civilization would survive an ejection event from their parent system, and then put up lamposts is up for debate, however.

The team isn’t suggesting that any random light source detected where there should be darkness might be considered a sign of life, though. There are many factors which could contribute to illumination, such as viewing angle, backscattering, surface shadowing, outgassing, rotation, surface albedo variations and more. this is just a new suggestion and a new way of looking at things, as well as suggested exercises for future telescopes and studying exoplanets.

“City lights would be easier to detect on a planet which was left in the dark of a formerly-habitable zone after its host star turned into a faint white dwarf,” Loeb and Turner say. “The related civilization will need to survive the intermediate red giant phase of its star. If it does, separating its artificial light from the natural light of a white dwarf, would be much easier than for the original star, both spectroscopically and in total brightness.”

The next generation of optical and space-based telescopes could help to refine the search process when observing extra-solar planets and preliminary broad-band photometric detection could be improved through the use of narrow-band filters which are tuned to the spectral features of artificial light sources such as light emitting diodes. While such a scenario on a distant world would need to involve far more “light pollution” than even we produce – why rule it out?

“This method opens a new window in the search for extraterrestrial civilizations,” Loeb and Turner write. “The search can be extended beyond the Solar System with next generation telescopes on the ground and in space, which would be capable of detecting phase modulation due to very strong artificial illumination on the night-side of planets as they orbit their parent stars.”

Read Loeb and Turner’s paper: Detection Technique for Artificially-Illuminated Objects in the Outer Solar System and Beyond.

This article was inspired by a discussion on Google+.

Nancy Atkinson also contributed to this article.

December 16, 2011December 24, 2015 by Ray Sanders

Ask Dr. Alan Stern

Dr. Alan Stern, Associate Vice President, Space Science and Engineering Division, Southwest Research Institute. Photo Credit: Southwest Research Institute

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We’re testing a new “Ask” article format here at Universe Today and we know you’ve got a question you’d like to ask Alan Stern!

Here’s how it works: Readers can submit questions they would like Universe Today to ask the guest responder. Simply post your question in the comments section of this article. We’ll take the top five (or so) questions, as ranked by “likes” on the discussion posts. If you see a question you think is good, click the “like” button to give it a vote.

Keep in mind that final question acceptance is based on the discretion of Universe Today and in some cases, the responder and/or their employer.

Our inaugural launch (pun intended) will feature Dr. Alan Stern, principal investigator for NASA’s “New Horizons” mission to Pluto.

Stern is a planetary scientist and an author who has published more than 175 technical papers and 40 popular articles. His research has focused on studies of our solar system’s Kuiper belt and Oort cloud, comets, satellites of the outer planets, Pluto and the search for evidence of solar systems around other stars. He has worked on spacecraft rendezvous theory, terrestrial polar mesospheric clouds, galactic astrophysics and studies of tenuous satellite atmospheres, including the atmosphere of the Moon.

Stern has a long association with NASA, serving the agency’s Associate Administrator for the Science Mission Directorate from 2007-2008; he was on the NASA Advisory Council and was the principal investigator on a number of planetary and lunar missions, including his current stint with the New Horizons Pluto-Kuiper Belt mission. He was the principal investigator of the Southwest Ultraviolet Imaging System, which flew on two space shuttle missions, STS-85 in 1997 and STS-93 in 1999.

He has been a guest observer on numerous NASA satellite observatories, including the International Ultraviolet Explorer, the Hubble Space Telescope, the International Infrared Observer and the Extreme Ultraviolet Observer.

Stern holds bachelor’s degrees in physics and astronomy and master’s degrees in aerospace engineering and planetary atmospheres from the University of Texas, Austin. In 1989, Stern earned a doctorate in astrophysics and planetary science from the University of Colorado at Boulder.

Aside from being the Principal Investigator for NASA’s “New Horizons” mission to Pluto, Currently Stern is the Associate Vice President of R&D – Space Science and Engineering Division at the Southwest Research Institute and recently was appointed director of the Florida Space Institute at Kennedy Space Center.

For those of you who are fans of Pluto, Dr. Stern went on the record against the IAU’s decision in 2006, stating “It’s an awful definition; it’s sloppy science and it would never pass peer review..”

Before submitting your question, take a minute and read a bit more about Dr. Stern at: Dr. Alan Stern

We’ll take questions until 4:00PM (MST) Tuesday December 20th and provide a follow up article with Dr. Stern’s responses to your questions.

December 16, 2011December 24, 2015 by Nancy Atkinson

Feisty Comet Lovejoy Survives Close Encounter with the Sun

An image received on Dec. 16th from the Solar and Heliospheric Observatory confirm that Comet Lovejoy survived perihelion and is now receding from the Sun. Credit: NASA, notations by Karl Battams.

It’s the morning after for the sungrazing Comet Lovejoy, and this feisty comet has scientists shaking their heads in disbelief. “I don’t know where to begin,” wrote Karl Battams, from the Naval Research Laboratory, who curates the Sun-grazing comets webpage. “What an extraordinary 24hrs! I suppose the first thing to say is this: I was wrong. Wrong, wrong, wrong. And I have never been so happy to be wrong!”

Many experts were predicting Comet Lovejoy would not survive perihelion, where it came within about 120,000 km from the Sun. But some extraordinary videos by NASA’s Solar Dynamics Observatory showed the comet entering and then surprisingly exiting the Sun’s atmosphere. Battams said he envisioned that if the comet survived at all, what would be left would be just a very diffuse component that would endure maybe a few hours after its close encounter with the Sun. But somehow it survived, even after enduring the several million-degree solar corona for nearly an hour. However, Comet Lovejoy appears to have lost its tail, as you can see in the image below.

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The comet is now in the view of other spacecraft, which will continue monitoring the object. It will likely grow a “new” tail as outgassing of dust, gas and debris will continue. It is not known yet how much of Comet Lovejoy’s core remains — which was 200 meters in diameter earlier this week — or how long it will continue to stay together after its close brush with the Sun.

But we’ll keep you posted!

See more videos of Lovejoy’s survival below: