Posted on by Nancy Atkinson

Mars Express: Looking Beneath Mars’ Surface

MARSIS
MARSIS fully deployed orbiting Mars. Image credit: ESA

To truly know and understand another world, planetary scientists need to look beneath the surface of that planet. This has been done on a small scale by looking inside impact craters, a la Opportunity and Spirit on Mars. But that only provides information for one area on a big planet. To get the global picture of the subsurface, a radar sounder instrument was developed for ESA’s Mars Express spacecraft. The Mars Advanced Radar for Subsurface and Ionosphere Sounding (MARSIS) experiment has now been successfully used for the first time to look beneath Mars’ south polar ice cap, opening up the third dimension for planetary exploration. “We have demonstrated that the polar caps at Mars are mostly water ice, and produced an inventory so now we know exactly how much water there is,” says Roberto Orosei, MARSIS Deputy Principal Investigator.

The data from MARSIS’ probe of the ice cap is still being analyzed, but scientists say they expect some surprising results to be revealed.

MARSIS is built to map the distribution of liquid and solid water in the upper portions of the Martian crust, and can investigate Mars’ subsurface up to a depth of 5 km. If reservoirs of water are detected, it will help us understand the hydrological, geological, climatic and possibly biological evolution of Mars. “At the south pole of Mars, we are seeing through ice 3.7 km thick. A small calculation shows that we could see through ice down to 20 km or more thick at Mars,” says Ali Safaeinili, MARSIS co-investigator.

No one had ever used a radar sounder from orbit on another planet before. So the team was uncertain it would work as planned. The subsurface of the planet might have been too opaque to the radar waves or the upper levels of Mars’ atmosphere (ionosphere) might have distorted the signal too much to be useful.

But, the instrument worked perfectly.

Every time a radar wave crosses a boundary between different substances, it generates an echo that the orbiter detects.

See ESA’s 3-D simulation of the radar instrument.

While MARSIS is still collecting data, a follow-up instrument is already operating at Mars. The Shallow Subsurface Radar (SHARAD) on NASA’s Mars Reconnaissance Orbiter works at higher frequencies than MARSIS and can see more details in the signals it receives from the underground layers, but it can’t penetrate the surface quite as far.

The technique’s success is prompting scientists to think of all the other places in the Solar System where they would like to use radar sounders. One obvious target is Jupiter’s icy moon, Europa. There, a radar sounder could probe the moon’s icy crust to help understand the puzzling features we see on the surface. It may even see the interface at the bottom of the ice where an ocean is expected to begin.

Asteroids and comets could be thoroughly scanned by a radar sounder, producing three-dimensional maps of their interior– perhaps exactly the data we will need if, one day, we have to nudge one out of Earth’s way. Also, this type of radar instrument could be used on our own planet to look inside Earth’s polar caps and ice sheets to determine their stability.

Mars Express has been orbiting the Red Planet since December 2003. It carries seven scientific experiments, including MARSIS, which was built by the Italian Space Agency with cooperation from JPL and the University of Iowa.

Original News Source: ESA press release

Posted on by Nancy Atkinson

Inflation Theory Takes a Little Kick in the Pants

Inflation theory proposes that the universe underwent a period of exponential expansion right after the Big Bang. One of the key predictions of inflation theory is the presence of a particular spectrum of “gravitational radiation”—ripples in the fabric of space-time that are really hard to detect but thought to exist. But a team of researchers has now found that gravitational radiation can be produced by a mechanism other than inflation. So this type of radiation, if eventually detected, won’t provide the conclusive evidence for inflation theory that was once was thought to be a certainty.

“If we see a primordial gravitational wave background, we can no longer say for sure it is due to inflation,” said noted astronomer Lawrence Krauss, from Case Western Reserve University.

Inflation theory first was proposed by cosmologist Alan Guth in 1981 as a means to explain some features of the universe that had previously baffled astronomers, such as why the universe is so close to being flat and why it is so uniform. Today, inflation remains the best way to theoretically understand many aspects of the early Big Bang universe, but most of the theory’s predictions are somewhat vague enough that even if the predictions were observed, they probably wouldn’t provide a clear-cut confirmation of the theory.

But gravitational radiation was considered one of the key predictions of inflation theory, and detection of this spectrum was regarded among physicists as “smoking gun” evidence that inflation did in fact occur, billions of years ago.

Gravitational radiation is a prediction of Einstein’s Theory of General Relativity. According to the theory, whenever large amounts of mass or energy are shifting around, it disrupts the surrounding space-time and ripples emanate from the region where the shift occurs. These ripples aren’t easily detected, but there is one experiment designed to look directly for this radiation, the Laser Interferometer Gravitational Wave Observatory (LIGO) in Livingston, Louisiana. The upcoming Planck Mission, set to launch in 2009 will look for it indirectly by looking at the cosmic microwave background.

Until now it was widely believed that detecting gravitational radiation in the form of polarized light from the CMB would confirm inflation theory, since it was thought inflation would be the only way this radiation could be produced. But Krauss and his team have raised the issue of whether this radiation can be unmistakably tied to inflation.

Krauss’s team proposes that a phenomenon called “symmetry breaking,” can also produce gravitational radiation. Symmetry breaking is a central part of fundamental particle physics, where a system goes from being symmetrical to a low energy state that is not symmetrical. Krauss’s explanation is that a “scalar field” (similar to an electric or magnetic field) becomes aligned as the universe expands. But as the universe expands, each region over which the field is aligned comes into contact with other regions where the field has a different alignment. When that happens the field relaxes into a state where it is aligned over the entire region and in the process of relaxing it emits gravitational radiation.

This is all fairly confusing, but the sweetened condensed version is that if gravitational radiation is ever detected, that event won’t necessarily verify inflation theory. Therefore, whether inflation theory can ever be confirmed remains to be seen.

Krauss’s paper “Nearly Scale Invariant Spectrum of Gravitational Radiation from Global Phase Transitions” is published in the Aprill 2008 Physical Review Letters.

Original News Source: Case Western Reserve University press release

Posted on by Ian O'Neill

Galactic Ghosts Haunt Their Killers

Image of the stellar tidal stream surrounding the spiral galaxy NGC 5907 obtained with an amateur robotic telescope in the mountains of New Mexico. (R. Jay Gabany)

The title may sound dramatic, but it is very descriptive. New observations of two galaxies have shown huge streams of stars, not belonging inside those galaxies, reaching out into space. These streams are all that are left of galaxies that are now dead, eaten by their cannibal neighbour, now sitting in their place. The streams form an eerie halo around their killers, looking like ghosts of their former selves…

So what happened to these ill-fated galaxies? Galactic cannibalism is what happened. In both examples, large spiral galaxies have overrun smaller dwarf galaxies, devouring most of their stars. All that is left are the huge fossilized remains in the form of a tenuous distribution of dim, old, metal-poor stars. Judging by the lack of galactic structure in these “ghosts”, the cannibalizing spiral galaxies have been very efficient at eating their smaller dwarf cousins.

a gigantic, tenuous loop-like structure extending more than 80 000 light-years from the centre of the galaxy (towards the top left). (R. Jay Gabany)

The debris surrounding NGC 5907 (approximately 40 million light-years from Earth) extends 150,000 light-years across (pictured top). NGC 5907 destroyed one of its dwarf satellite galaxies at least 4,000 million years ago, consuming the stars, star clusters and dark matter, leaving only a small number of old stars behind to form a complicated criss-cross pattern of galactic fossils.

“Our results provide a fresh insight into this spectacular phenomenon surrounding spiral galaxies and show that haloes contain fossil dwarf galaxies, thus providing us with a unique opportunity to study the final stages in the assembly of galaxies like ours.” – David Martínez, from the Instituto de Astrofísica de Canarias (IAC) leading the team that carried out these observations.

In the second spiral galaxy, NGC 4013 (50 million light-years from Earth in the constellation of Ursa Major), the ghost of another dead dwarf galaxy stretches 80,000 light-years across and is made up of old stars. Its 3D geometry is unknown, but it has similar characteristics to the Monoceros tidal stream which surrounds the Milky Way. The Monoceros tidal stream is a ring of stars, originating from a local dwarf galaxy that was eaten by our galaxy over 3,000 million years ago.

These images have a huge amount of science to offer researchers. Primarily, the detection of these galactic fossils confirms the predictions of the cold dark matter model of cosmology, which describes how the large spiral galaxies were formed from merging stellar systems.

“…fitting theoretical models to these star streams enables us to reconstruct their history and describe one of the most mysterious and controversial components of galaxies: dark matter.” – Jorge Peñarrubia, theoretical astrophysicist at the University of Victoria (Canada) who is working on this project.

Source: IAC

Posted on by Ian O'Neill

The Pioneer Anomaly: A Deviation from Einstein Gravity?

Artist impression of the Pioneer 10 probe (NASA)

Both Pioneer probes are approximately 240,000 miles (386,000 km) closer to the Sun than predicted by calculation. Scientists have been arguing over the cause of this mysterious force for a decade and reasons for the Pioneer anomaly range from the bizarre to the sublime. Is it a simple fuel leak, pushing the probes of course? Is it phantom dark matter dragging them down? Or do the gravity textbooks need to be re-written? Unfortunately there’s still no one answer, but some researchers believe there might be a small deviation in the large-scale space-time Einstein described in his famous theory of general relativity. See, I knew there would be a simple explanation…

The Pioneer 10 and 11 deep space probes were launched in 1972 and 1973, visiting Jupiter and Saturn before pushing on toward interplanetary space, into the unknown. The Pioneer program really lived up to its name, pioneering deep space exploration. But a few years on, as the probes passed the through the 20-70 AU mark, something strange happened… not suddenly, but gradually. Ten years ago Pioneer scientists noticed that something was wrong; the probes were slightly off course. Not by much, but both were experiencing a slight but constant sunward acceleration. The Pioneer probes had been measured some 240,000 miles (386,000 km) closer to the Sun than predicted. This might sound like a long way, but in astronomical terms it’s miniscule. 240,000 miles is a tiny deviation after 6.5 billion miles (10.5 billion km) of travel (it would take light 10 hours to cover this distance), but it’s a deviation all the same and physicists are having a very hard time trying to work out what the problem is.

That is until NASA physicist Slava Turyshev, co-discoverer of the anomaly, rescued a number of Pioneer magnetic data storage disks from being thrown out in 2006. These disks contain telemetric data, temperature and power readings that both Pioneer probes had transmitted back to mission control up to 2003 (when Pioneer 10 lost contact with Earth). From this, Turyshev and his colleagues teamed up with Viktor Toth, a computer programmer in Ottawa, Ontario, to design a new code designed to extract the vast quantity of raw binary code (1s and 0s), revealing the temperature and power readings from the crafts instruments. It sounds as if the search for the culprit of the Pioneer anomaly required a bit of forensic science.

Now the researchers have a valuable tool at their disposal. Turyshev and 50 other scientists are trying to match this raw data with modelled data in an effort to reconstruct the heat and electricity flow around the craft’s instrumentation. Electricity was supplied by the on-board plutonium generator, but this is only a small portion of the energy generated; the rest was converted to heat, lost to space and warmed up the probe’s bodywork. Heat lost to space and warming of the probe’s instruments are both thought to have a part to play in altering spacecraft momentum. So could this be the answer?

Tests are ongoing, and only a select few simulations have been run. However, early results indicate that around 30% of the Pioneer anomaly is down to the on-board heat distribution. The rest, it seems, still cannot be explained by probe dynamics alone. The team are currently processing a total of 50 years of telemetry data (from both Pioneer 10 and 11), so more simulations on the rich supply of transmissions from the probes may still uncover some surprises.

But on the back of everyone’s mind, and it keeps cropping up in every Pioneer anomaly article I find, that the fundamental physics of our universe may need to be brought into question. Sending long-distance deep space probes gives us a huge opportunity to see if what we observe locally is the same for other parts of the Solar System. Could Einstein’s general theory of relativity need to be “tweaked” when considering interplanetary (or interstellar) travel?

The researchers are excited if a mundane solution does not present itself (i.e. probe heat distribution effects), therefore indicating some other cosmic reason is behind this anomaly:

“If we actually had a means in the solar system here to measure deviations from Einstein’s gravity, that would be phenomenal.” – Viktor Toth

In the mean time, Pioneer 10 is drifting silently toward the red star of Aldebarran and (barring any more anomalous behaviour) will arrive there in 2 million years time…

Sources: Scientific American, Symmetry Breaking News

Posted on by Ian O'Neill

Radiation Sickness, Cellular Damage and Increased Cancer Risk for Long-term Missions to Mars

A mission to Mars will benefit from a mini-magnetosphere (NASA)

There is a nagging problem under the surface of the excitement surrounding the future of long-term missions into space. Human exposure to the high amounts of solar radiation and other sources of cosmic rays is likely to be the main factor that could curtail mankind’s dreams for future manned settlements on other planets. The effects of radiation exposure to astronauts is not fully understood, but could range from acute radiation sickness (perhaps after being caught in an intense solar storm during interplanetary transit) to gradual cellular damage, greatly increasing the risk of cancer in long-term missions. So what can we do about it? Mankind is highly adaptive and some countermeasures are gradually being realized. (And yes, the Russian Space Monkeys might be able to help…)

The problem comes when humans leave the protective blanket of the Earth’s magnetic field. Acting like a huge, invisible force field, the magnetosphere deflects most of the harmful high energy particles being fired from the Sun. Anything that penetrates this barrier is quickly absorbed by our thick atmosphere. Even at high altitudes, in low Earth orbit, some protection to astronauts can be provided (although the ambient radiation is far higher up there than down here). So when we talk about colonizing other planets and sending astronauts further and further into deep space, radiation exposure becomes a bigger risk.

Solar flares will be a problem for future colonists (SOHO/EIT)

An immediate concern is that astronauts may get caught in a solar storm, where the Sun (usually around solar maximum) ejects huge clouds of highly energetic protons. If the storm is intense enough, huge doses of radiation could be inflicted on the men and women in space. Roughly, a dose of 500 rads or more will kill a human in two to three hours, and a smaller dose could cause acute radiation sickness. Radiation sickness could be fatal in weeks should the astronaut not receive urgent medical care. How about the long-term, gradual impact of prolonged exposure to higher-than-normal doses of radiation? This is an area of space medicine that we do not completely understand as yet.

In new research by the Lombardi Comprehensive Cancer Center at Georgetown University Medical Center, the high-energy nature of radiation in space may lead to premature aging and prolonged oxidative stress in cells. This also suggests that astronauts risk a higher than normal risk of cancers, such as colon cancer, through exposure to “high linear energy transfer” (LET) radiation. LET radiation consists of the high energy protons emitted by the Sun and cause a huge amount of damage to small areas of tissue.

“Radiation exposure, either intentional or accidental, is inevitable during our lifetimes, but with plans for a mission to Mars, we need to understand more about the nature of radiation in space. There is currently no conclusive information for estimating the risk that astronauts may experience.” – Kamal Datta, M.D., assistant professor at Lombardi and lead author.

With NASA’s Project Constellation on the horizon, there has been a focus on the long-term effects of interplanetary radiation. Ultimately, this project aims to send humans to the Moon and Mars, but there are strong indicators that astronauts will face in increased cancer risk and lifespan reduction, a massive hindrance to a mission spanning several months or a thriving proto-settlement.

This is where the lab mice help us out. The amount of “free radicals” (highly reactive molecules often linked with cancer and cell aging) were measured and found that the mice developed highly oxidative (i.e. full of free radical molecules) gastrointestinal tracts when exposed to space-like high-LET radiation. The Lombardi group concluded that the mice had developed a high risk to various cancers, particularly gastrointestinal cancers. They also noticed that after exposure (even after two months), the mice prematurely aged, signifying that the effect of radiation damage can persist long after exposure to a high-LET environment.

So what can we do? There are several plans in motion to further test the effects of radiation on humans and to predict when astronauts will be at risk. This week, Russia announced (controversial) plans to send monkeys back into space, possibly as far as Mars. Once the shock of this “outdated” proposal wore off (the previous Russian space monkey program ran out of funding in the 1990’s), it became very clear as to what the Russian space agency is hoping to achieve: to have a better understanding of the long-term exposure to a high-LET environment on the human physiology. Many will argue that this practice is cruel and unnecessary, but others will say monkeys are used in experiments every day, why shouldn’t they help us in the ultra-modern world of space travel? The jury is still out on this debate, but there are many ways to investigate and counteract the radiation effect on humans.

Energetic particle tracks in a bubble chamber (NASA)

There are also many systems in place to protect mankind from the onslaught of solar storms. Using the Solar and Heliospheric Observatory (SOHO) and other craft located between the Earth and Sun, an early warning system has been set up to provide astronauts on orbit with some time to take cover should a solar flare be launched Earth-bound. This system is fully operational and has already proven itself. Recently, I toyed with the idea of a similar Mars-based early warning system, providing future Mars colonies with about 40 minutes advanced notice of an incoming solar storm.

Shielding is another obvious protective measure. Lunar and Mars colonies are most likely going to use large amounts of regolith to block the incoming particles. Only a few meters of locally dug-up regolith will provide excellent protection. But what about the journey to Mars? How will the astronauts of projects such as Constellation be protected? Perhaps an advanced “Ion Shield” might work?

Whatever the effect of radiation on humans in space, it seems obvious that we are in the infancy of space flight and we are already addressing some of the most difficult problems. Over the next few years, much effort will be focused on the health of astronauts, hopefully finding some answers to the space radiation problem.

Original source: Georgetown University Medical Center

Posted on by Nancy Atkinson

Latest News on Apophis: 13 -year-old Boy Corrects NASA’s Estimates of Earth Impact — Not! (Update)

Annimation of Apophis. Image Credit: Osservatorio Astronomico Sormano
Update: It turns out this story is a fabrication and AFP didn’t check the facts with NASA as I suspected. According to the blog Cosmos4u, they talked with Don Yeomans at NASA’s NEO office and this is what Yeoman’s said about the news story of a 13-year old boy correcting NASA’s estimates of Apohpis impacting earth: “We have not corresponded with this young man and this story is absurd, a hoax or both. During its 2029 Earth close approach, Apophis will approach the Earth to about 38,900 km, well inside the geosynchronous distance at 42,240 km. However, the asteroid will cross the equatorial belt at a distance of 51,000 km – well outside the geosynchronous distance. Since the uncertainty on Apophis’ position during the Earth close approach is about 1500 km, Apophis cannot approach an Earth satellite. Apophis will not cross the moon’s orbital plane at the Moon’s orbital distance so it cannot approach the moon either.”

Also, the scientist mentioned in AFP’s story said he wasn’t conferred with either by the news agency. So don’t give any heed to this story that has been running amok around the internet.

But here’s our story on this as it originally ran: Here’s a story that supports the value of science fairs. And it also makes one wonder where else NASA’s decimal points might be off by a couple of places. One caveat on this news piece, however: as far as I know there hasn’t been an official NASA press release on this.

Reportedly, a 13-year-old German schoolboy doing research for a science competition found errors in NASA’s estimates on the chances of the asteroid Apophis colliding with Earth. The boy, Nico Marquardt used data from the Institute of Astrophysics in Potsdam to calculate that there was a 1 in 450 chance that the Apophis asteroid will collide with Earth. NASA had previously estimated the chances at only 1 in 45,000, but according to an AFP news release, NASA now acknowledges the kid is right. (Actually, no they don’t.)
Continue reading “Latest News on Apophis: 13 -year-old Boy Corrects NASA’s Estimates of Earth Impact — Not! (Update)”

Posted on by Nancy Atkinson

Where In The World (and What World) Is This?

Anyone care to guess what orbiting spacecraft is responsible for taking this image, or even what world this is a picture of? At first glance, with all those craters, it could be Mars. However, the coloring isn’t quite right for the Red Planet. Is it a photograph of Mercury or an image of the moon?

OK, yes, this is an image of Earth, but you were wondering there for awhile, weren’t you! Interestingly enough, the white area is not snow, and the craters are not impact craters, but volcanic. And what spacecraft gets credit for the image? The International Space Station. This is one of the most recent images taken by the astronauts on board the ISS as part of the Earth Observatory program. A wonderful website, NASA’s Gateway to Astronaut Photography of Earth, hosts an incredible collection of photographs that astronauts have taken of our home planet.

Beginning with the Mercury missions in the early 1960s, astronauts have taken photographs of the Earth. As of April 7, 2008, this website has 759,527 views of the Earth, which includes 315,923 from the ISS. The site processes images coming down from the International Space Station on a daily basis, so the database is continually growing. The U.S. Destiny Laboratory module has a science window with high optical quality, which usually faces the Earth, and most of the ISS’s images are taken from that window on the world. On board the ISS is a nice selection of professional digital cameras, and a variety of lenses. One could spend hours (or days or a lifetime!) browsing through the striking photographs of Earth the astronauts have taken. The website also includes lots of information about each of the images, and a fun Where In the World quiz to test your geographical knowledge.

The image above is of the Harrat Khaybar volcanic field, a 14,000-square-kilometer area located in the western Arabian peninsula. The volcanic field was formed by eruptions along a 100-kilometer, north-south vent system over the past 5 million years. The most recent recorded eruption took place between 600-700 AD.

Harrat Khaybar contains a wide range of volcanic rock types and spectacular landforms, several of which are represented in this astronaut photograph. There are dark, fluid basalt lava flows, and the white deposits are sand and silt that accumulate in the depressions. There are lava domes and cones from the past volcanic activity.

The ISS astronauts take images daily of our planet. The image of Harrat Khaybar was taken on March 31, 2008, with a Kodak 760C digital camera fitted with a 400 mm lens, and is provided as part of the the ISS Crew Earth Observations experiment.

Original News Source: Earth Observatory website

Posted on by Fraser Cain

Astrosphere for April 15, 2008

Don’t just look inward, look outward. There’s a whole astrosphere out there. Your picture for the day is Saturn (of course), captured by Stargazer 7000.

Astronomy Picture of the Day has a beautiful shot of the night sky over Sweden.

PZ Myers has spoken and I must obey. Here’s all you need to know about expelled.

And here’s a review for another movie, Dark Matter.

Speaking of dark matter, Ethan Siegel explains the practical uses for his research.

Astroprof recalls famed astronomer John Archibald Wheeler; the man who coined the term “black hole” passed away this week.

Bad Astronomer Phil Plait celebrated Yuri’s night, in style.

Posted on by Ian O'Neill

Coolest, Darkest Brown Dwarf Discovered

An artist impression of a brown dwarf (Hallinan et al., NRAO/AUI/NSF)

The coolest brown dwarf has been discovered, with a surface temperature of 623 Kelvin (that’s only 350 Celsius or 660 degrees Fahrenheit). Compare with the surface temperature of our Sun, a modest 6,000 Kelvin, you can see that this featherweight dwarf “star” is a little odd. As far as stars go, this one is pretty unspectacular, but it does hold a vast amount of interest. It may not be as sexy as a supernova or as exotic as a neutron star, the humble brown dwarf may provide the essential link between planets (specifically gas giants) and stars. They are effectively failed stars, and this new discovery demonstrates just how cold they can be…

Brown dwarfs are the link between massive planets and small stars. They have an upper limit of about 80 Jupiter masses, but are not massive enough to sustain nuclear fusion in their core. They do however experience convection from the interior to the surface. The confusion arises when trying to find the lower limit of brown dwarf size, at what mass does the gas giant planet start being a brown dwarf star? This grey area is thought to be characterized by an entirely new stellar type: Y-class dwarfs. Until now Y-class dwarfs have been very elusive and have only existed in theory.

A comparison of the size of Jupiter, a brown dwarf, a small star and the Sun (Gemini Observatory/Artwork by Jon Lomberg)

Astronomers using near-infrared and infrared instruments at the Canada France Hawaii and Gemini North telescopes and the European Southern Observatory in Chile have discovered a Y-class dwarf, bringing this strange failed star from theory and into reality. What’s more, it’s in our cosmic neighbourhood, only 40 light-years from Earth. This brown dwarf has been unglamorously named “CFBDS0059”, but I would have called it something like “The Dark Star” or “The Death Star”, as it is so dim and its surface temperature is approximately the same as the surface temperature of the planet Mercury (but much cooler than the surface temperature of Venus). As it is so cool, it isn’t very luminescent and only radiates in the near-infrared wavelengths (it’s not even as hot as a standard electric stove element), requiring specialist equipment to detect it. As it turns out, CFBDS0059 is small, only 15-30 times the mass of Jupiter, fulfilling the lower mass limit of brown dwarf stars and will be known as the first Y-class dwarf to be observed.

But what is the indicator that a Y-class brown dwarf has been observed? Using spectrometers, astronomers have been able to see the constituent compounds making up the brown dwarf’s atmosphere. Should ammonia be discovered, it’s a pretty sure sign that a Y-class dwarf has been found.

“We are starting to see a little hint of ammonia absorption.” Loic Albert (stellar researcher) of the Canada France Hawaii Telescope in Hawaii, commenting on CFBDS0059.

There are two other verified classes of dwarfs, L and T-class dwarfs. L-class dwarfs are hotter, with temperatures from 2200 to 3600°F and T-class dwarfs are cooler than 2190°F and methane-rich. CFBDS0059 is obviously much, much cooler, but researchers believe there may be still cooler dwarfs out there, possibly condensing any water vapour in their atmospheres to form clouds, setting Y-class dwarfs far from the characteristics of its L and T-class cousins. Should they get any colder, water will freeze into ice crystals, giving them more planetary than stellar characteristics.

Source: Discovery.com

Posted on by Fraser Cain

Milky Way’s Black Hole Gave Off a Burst 300 Years Ago

Sagittarius A*. Image credit: Chandra

Our Milky Way’s black hole is quiet – too quiet – some astronomers might say. But according to a team of Japanese astronomers, the supermassive black hole at the heart of our galaxy might be just as active as those in other galaxies, it’s just taking a little break. Their evidence? The echoes from a massive outburst that occurred 300 years ago.

The astronomers found evidence of the outburst using ESA’s XMM-Newton space telescope, as well as NASA and Japanese X-ray satellites. And it helps solve the mystery about why the Milky Way’s black hole is so quiet. Even though it contains 4 million times the mass of our Sun, it emits a fraction of the radiation coming from other galactic black holes.

“We have wondered why the Milky Way’s black hole appears to be a slumbering giant,” says team leader Tatsuya Inui of Kyoto University in Japan. “But now we realize that the black hole was far more active in the past. Perhaps it’s just resting after a major outburst.”

The team gathered their observations from 1994 to 2005. They watched how clouds of gas near the central black hole brightened and dimmed in X-ray light as pulses of radiation swept past. These are echoes, visible long after the black hole has gone quiet again.

One large gas cloud is known as Sagittarius B2, and it’s located 300 light-years away from the central black hole. In other words, radiation reflecting off of Sagittarius B2 must have come from the black hole 300 years previously.

By watching the region for more than 10 years, the astronomers were able to watch an event wash across the cloud. Approximately 300 years ago, the black hole unleashed a flare that made it a million times brighter than it is today.

It’s hard to explain how the black hole could vary in its radiation output so greatly. It’s possible that a supernova in the region plowed gas and dust into the vicinity of the black hole. This led to a temporary feeding frenzy that awoke the black hole and produced the great flare.

Original Source: ESA News Release