Universe Today

March 12, 2009December 24, 2015 by Nancy Atkinson

Hubble Finds Evidence of Dark Matter Around Small Galaxies

Perseus Cluster. Credit: NASA, ESA, and Z. Levay (STScI)

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The Hubble Space Telescope has uncovered a strong new line of evidence that galaxies are embedded in halos of dark matter. By looking at the Perseus galaxy cluster, Hubble discovered a large number of small galaxies that have remained intact while larger galaxies around them are being ripped apart by the gravitational tug of other galaxies. “We were surprised to find so many dwarf galaxies in the core of this cluster that were so smooth and round and had no evidence at all of any kind of disturbance,” said astronomer Christopher Conselice of the University of Nottingham, UK, and leader of the team that made the Hubble observations. “These dwarfs are very old galaxies that have been in the cluster for a long time. So if something was going to disrupt them, it would have happened by now. They must be very, very dark-matter-dominated galaxies.”

Observations by Hubble’s Advanced Camera for Surveys spotted 29 dwarf elliptical galaxies in the Perseus Cluster, located 250 million light-years away and one of the closest galaxy clusters to Earth. Of these galaxies, 17 are new discoveries.

Cosmologists estimate that dark matter comprises 23 percent of all energy in the cosmos. An equally mysterious “dark energy,” which drives galaxies apart, is thought to take up another 73 percent or so. The ordinary matter that we can see is believed to represent only four percent of the total mass of the Universe.

Because dark matter cannot be seen, astronomers detected its presence through indirect evidence. The most common method is by measuring the velocities of individual stars or groups of stars as they move randomly in the galaxy or as they rotate around the galaxy. The Perseus Cluster is too far away for telescopes to resolve individual stars and measure their motions. So Conselice and his team derived a new technique for uncovering dark matter in these dwarf galaxies by determining the minimum additional mass contribution from dark matter that the dwarfs must have to protect them from being disrupted by the strong, tidal pull of gravity from larger galaxies.

Galaxies in the Perseus Cluster. Credit: NASA, ESA, and Z. Levay (STScI)

The dwarf galaxies may have an even higher amount of dark matter than spiral galaxies. “With these results, we cannot say whether the dark matter content of the dwarfs is higher than in the Milky Way Galaxy,” Conselice said. “Although, the fact that spiral galaxies are destroyed in clusters, while the dwarfs are not, suggests that this is indeed the case.”

But these new images provide evidence that the undisturbed galaxies are enshrouded by a “cushion” of dark matter that protects them from being torn apart.

Source: HubbleSite

March 12, 2009December 24, 2015 by Anne Minard

Cassini Switches to Backup Thrusters

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NASA’s Cassini spacecraft successfully switched to a backup set of propulsion thrusters late Wednesday, which will allow the long-lived machine to continue scoping out Saturn and its moons.

The swap was performed because of degradation in the performance of the primary thrusters, which had been in use since Cassini’s launch in 1997. This is only the second time in Cassini’s 11 years of flight that the engineering teams have gone to a backup system.

299665main_pia11141a-516 — This natural color view was created from images collected shortly after Cassini began its extended Equinox Mission in July 2008. Credit: NASA

The Cassini-Huygens mission is a cooperative project of NASA, the European Space Agency and the Italian Space Agency. Since its launch four years ago, the mission sent the Huygens probe to Saturn’s largest moon, Titan, and has yielded copious data about Saturn, its rings and its many moons.

The thrusters are used for making small corrections to the spacecraft’s course, for some attitude control functions, and for making angular momentum adjustments in the reaction wheels, which also are used for attitude control. The redundant set is an identical set of eight thrusters. Almost all Cassini engineering subsystems have redundant backup capability.

Cassini has successfully completed its original four-year planned tour of Saturn and is now in extended mission operations.

Sources: NASA, here and here.

March 12, 2009December 24, 2015 by Nancy Atkinson

Close Call: Astronauts Evacuate But Space Station Avoids Debris Hit

International Space Station. Credit: NASA

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The three crew members on board the International Space Station were told to “evacuate” into the Soyuz spacecraft earlier today, when they were notified of possible debris hit to the station. However, thankfully, the debris passed by harmlessly. NASA and mission control in Moscow received a “RED threshold late notice conjunction threat alert” Thursday morning, confirming the object, cataloged as “25090 PAM-D” – said to be a piece of a spent satellite rocket motor –, would approach near the station at 16:39 GMT. Mission control radioed to the crew the possibility of impact to the station was low, but the piece of debris was large enough that if it hit the ISS, there would only be a 10 minute reserve time. NASA sources said the debris was estimated to be 0.009 meters (0.35 inches) wide, weighing less than 1 kg, (Update: NASA now says the object was about 5 inches (12.7 cm) and was expected to pass about 4.5 kilometers (2.8 miles) from the station. That is close enough for concern in space.

The crew responded quickly and professionally throughout the close-out procedures. ISS Commander Mike Fincke, US crew member Sandy Magnus and Russian Flight engineer Yury Lonchakov followed pre-prescribed procedures in closing hatches and window shutters before climbing into the Soyuz. The Soyuz hatch, however was left open. If the debris had hit the station, the crew could have quickly shut the Soyuz hatch and flew to Earth.

The three crewmembers currently on board the ISS. Credit: NASA

The object was initially classified as a low threat of collision with the ISS. However, tracking Thursday morning suggested a greater threat. Usually, when debris is seen as on a possible collision course with the ISS, the station is able to fire thrusters and maneuver out of danger. However, because of the late notice, there wasn’t time to perform the thruster maneuvers.

Afterward, Fincke radioed to mission control that they had kept an eye out for debris passing by while they were in the Soyuz, but they didn’t see anything. The crew quickly returned to the station, opening up hatches and other systems they had shut down, resuming their schedule. Magnus calmly said she was going to go running, part of the daily exercise routine astronauts must perform in space to maintain muscle mass and bone density. Events that were previously scheduled during the time of the evacuation procedures are being rescheduled.

See more info on the debris and evacuation procedures at NASASpaceflight.com.

March 12, 2009December 24, 2015 by Mark Mortimer

Book Review: Solar Sails – A Novel Approach to Interplanetary Travel

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Great pleasure can be had in sailing across a gentle, blue sea with a fair wind at the back. With little more effort than a slight nudge upon the tiller, you and your craft can travel great distances at a leisurely, enjoyable, relaxing pace. Now, replace wind and water by sail and photon as a trio of authors write in their book “Solar Sails – A Novel Approach to Interplanetary Travel“. In it, Giovanni Vulpetti, Les Johnson and Gregory L. Matloff show a very capable and promising method of local and interstellar travel.

Solar sailing uses the push of sunlight against a collector or sail to move a craft. With the absorption and/or reflection of photons, the craft continues to accelerate so that, after making a sun dive, it could travel out of our solar system at velocities in excess of 500 kilometres per second. This idea is so promising that most major national space agencies are looking into sail material and optimal flight paths.

To get you on your way, this book serves as an introduction to the idea of solar sailing. It starts with a review of rocket physics. Then there’s a section that discusses the pro’s and con’s of chemical and nuclear propulsion, as well as some more exotic ones, like Bussard’s proton-fusing interstellar ramjet. However, much of the writing serves to inform the reader of the impractical nature of such forms of propulsion. Hence, by contrast, this section capably serves to show the practical nature of solar sails.

Having provided this belief that solar sails are practical and feasible with current technology, the book continues by describing solar sails in more detail. It discusses sail manufacturing, sail craft construction and delivery, and, methods of sailing or tacking. By using common nomenclature, the book easily conveys the necessary scientific elements to both a generalist and a space enthusiast. Some times it gets a bit technical, such as when describing the use of the Jovian magnetic field as an energy source. But, these tend to make the book more valuable than overly complicated.

The book concludes with technical aspects. Here, it provides details aimed to attract the interest of graduate and post-graduate students. And, there’s lots to attract, especially as so little space validation has occurred for this technology. Whether unfurling space sails, dealing with desorption, or controlling nanobots, this book provides many challenges and lots of promise for the future but also recognizes a need for a lot of effort to reach maturity. Yet, the book shows, through references to individuals’ work and the work of national space agencies, that the concept is real, practicable and potentially very rewarding.

The next time you’re floating along on your yacht or dreaming along in your armchair, take your sailing dreams to another level. Giovanni Vulpetti, Les Johnson and Gregory L. Matloff’s book “Solar Sails – A Novel Approach to Interplanetary Travel” let you see how a well known and practised human skill can be used well away from the water’s surface. From it, we can see how Earth’s water can slip far astern while the horizons of different planets fill the view over the bow.

March 12, 2009December 24, 2015 by Nancy Atkinson

ISS Crew May Need to Evacuate: Possible Debris Hit

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According to NASASpaceflight.com, the three crew members on board the International Space Station are being prepared for the contingency of evacuation into the Soyuz spacecraft attached to the station following a “RED threshold late notice conjunction threat” alert. The object’s closest approach would occur at 11:39 CDT, slightly more than an hour from the time of this posting. The object, cataloged as “25090 PAM-D” is orbital debris, and was initially classed as a low threat of collision with the ISS. However, latest tracking suggests the threat is now greater. As a contingency, NASA’s Expedition 18 Commander Mike Fincke, Russian Flight Engineer Yury Lonchakov, and NASA’s Sandra Magnus may be asked to evacuate into the Russian Soyuz, which would serve as their means of departing from the Station – should it be required.
UPDATE: (10:45 am CDT) Communications with ISS crew from mission control confirms the crew will be going into the Soyuz in case of impact. There is a low probability of impact, but the object is large, and if it does hit, they are talking about only a 10 minute reserve time. Fincke will be closing out the hatches on the US segment.
2nd UPDATE (11:15 am CDT) ISS is closing hatches on all the modules in preparation for evacuation into Soyuz. Crew will stay in the Soyuz from 16:30 to 16:45 GMT, possible debris hit would be at 16:39.
Final update: Debris passed harmlessly. See post-event article.

Several memos acquired by NASASpaceflight.com relay the probability level of the impact, with the latest noting “It’s now in the red threshold and if it doesn’t improve between now and TCA (Time of Closest Approach) at 11:39am CDT today they will put the crew in the Soyuz per the rules.”

“The plan that has been coordinated with MCC-M (Moscow) is that if required the crew will enter the Soyuz and be in place by 16:35 staying there until at least 5 minutes post TCA,” added another memo.

“We will not be closing any additional hatches to enable us to immediately run the nominal depress procedures should they be needed.

“If the PC remains red the course of action will be to place the crew in the Soyuz from 5 minutes before TCA until 5 minutes after TCA. This is ~2 hours after crew post sleep activities (crew will be awake). ”

We’ll keep you posted.

March 12, 2009May 4, 2017 by Nancy Atkinson

Why is Science Important?

Science is everywhere in today’s world. It is part of our daily lives, from cooking and gardening, to recycling and comprehending the daily weather report, to reading a map and using a computer. Advances in technology and science are transforming our world at an incredible pace, and our children’s future will surely be filled with leaps in technology we can only imagine. Being “science literate” will no longer be just an advantage but an absolute necessity. We can’t escape from the significance of science in our world.

But not everyone understands that, or has been taught to think critically, or been provided with the tools to analyze and test a problem or situation.

Alom Shaha is a school teacher in the UK, and he has put together a website and a video, asking people to share why science is important. There are scientists, educators, psychologists, artists and many others from different walks of life who participated in this project. The video is of exceptional quality, and I urge everyone to watch and share it. Help people learn about the importance of science.

Why is Science Important? from Alom Shaha on Vimeo.

Continue reading “Why is Science Important?”

March 11, 2009December 24, 2015 by Nancy Atkinson

‘Sexy’ GOCE Spacecraft Will Try Again For Launch

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I got some grief for calling the GOCE spacecraft ‘sexy’ last year, but I’m sticking with that description. What a gorgeous spacecraft! And the GOCE team has stuck with their spacecraft while it had to stand down from launch in September of 2008 when problems were discovered with the guidance and navigation subsystems on the Russian Breeze KM rocket. GOCE had to be de-mated from the rocket and brought back into the clean room last year, but now is back on the launch pad, and is scheduled to liftoff on Monday, March 16 at 14:21 GMT from the Plesetsk Cosmodrome in northern Russia.

GOCE, which stands for Gravity field and steady-state Ocean Circulation Explorer will investigate and map Earth’s gravitational field. It will also provide a high-resolution map of Earth’s geoid, which is the surface of equal gravitational potential defined by the gravity field. This will greatly improve our knowledge and understanding of the Earth’s internal structure, and will be used as a much-improved reference for ocean and climate studies, including sea-level changes, oceanic circulation and ice caps dynamics survey. Numerous applications are expected in climatology, oceanography and geophysics.

GOCE at the launchpad in Russia. Credit: ESA

The 1 ton, 5 meter-long spacecraft will be in an extra low orbit (260 km, or 161 miles) and will experience drag from Earth’s upper atmosphere, so its smooth and lean (and sexy) surface helps reduce the friction. Adding to the sleek design is that the solar panels are attached to the long body of the satellite instead of sticking out and adding to the drag. However, the spacecraft will need a boost to its orbit occasionally, and has state of the art ion engines.

ESA has a great animation of GOCE in flight.

Source: ESA

March 11, 2009December 24, 2015 by Nancy Atkinson

Mars Odyssey Survives Risky Reboot

Artists image of Odyssey in orbit around Mars. Credit: NASA/JPL

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NASA’s Mars Odyssey orbiter was successfully rebooted today, to thwart any potential future problems with memory corruption of its main systems, and with hopes of restoring use of back-up systems. Odyssey has been functioning normally, but its memory cache hadn’t been cleared for five years. The spacecraft followed commands to shut down and then restart, a strategy that engineers hoped would clear any memory flaws. The procedure also restored Odyssey’s onboard set of backup systems, called the spacecraft’s “B side,” allowing its use in the future when necessary. “For nearly two years, we have not known for certain whether the backup systems would be usable, so this successful reboot has allowed us to ascertain their health and availability for future use,” said Odyssey Project Manager Philip Varghese of NASA’s Jet Propulsion Laboratory, Pasadena, Calif.

Engineers were going to perform the reboot on March 10, but an unexpected rise in temperature of the star camera in Odyssey’s navigation system prompted a postponement of the procedure. Engineers identified the cause as a heater circuit that was temporarily stuck “on.” The circuit was turned off before today’s reboot.

Memory corruption is caused by cosmic ray hits and other effects of the space radiation environment. This reboot was not a risk-free event, but the Odyssey team and NASA carefully weighed the risks of performing a cold reboot compared with the risk of doing nothing, and determined that the best thing was to reboot now instead of waiting for potential problems to crop up.

Odyssey, which also serves as a relay for communications for the Mars Exploration Rovers, has been orbiting Mars since 2001. Odyssey has never switched from its primary set of components, the “A side,” to the backup set, which includes an identical computer processor, navigation sensors, relay radio and other components. In March 2006, the B-side spare of a component for managing the distribution of power became inoperable. Analysis by engineers identified a possibility that rebooting Odyssey might restore that component, but it had not been done until today. And now the B-side seems to be working.

The Odyssey team began a series of steps after the reboot to carefully return the spacecraft to full functioning over the next few days. Odyssey and all the science instruments should be back to studying Mars by next week.

March 11, 2009December 24, 2015 by Nancy Atkinson

Where In The Universe #46

It’s time once again for another Where In The Universe Challenge. Test your visual knowledge of the cosmos by naming where in the Universe this image was taken and give yourself extra points if you can name the spacecraft responsible for this picture. Post your guesses in the comments section, and check back on Thursday at this same post to find the answer. To make this challenge fun for everyone, please don’t include links to the answer in your comments. Good luck!

UPDATE (3/12) The answer has now been posted below. Don’t peek before you make your guess!

Unfortunately these are not multiple Pacmen or fortune cookies, but sand dunes. These dunes, are called “barchan” which means arc-shaped, and they are on Mars. The image was taken by the Mars Global Surveyor (MGS) Mars Orbiter Camera. This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows north polar sand dunes in the summertime. During winter and early spring, north polar dunes are covered with bright frost. When the frost sublimes away, the dunes appear darker than their surroundings. To a geologist, sand has a very specific meaning. A sand grain is defined independently of its composition; it is a particle with a size between 62.5 and 2000 microns. Two thousand microns equals 2 millimeters. The dunes are dark because they are composed of sand grains made of dark minerals and/or rock fragments. Usually, dark grains indicate the presence of unoxidized iron, for example, the dark volcanic rocks of Hawaii, Iceland, and elsewhere. This dune field is located near 71.7°N, 51.3°W. Dune slip faces indicate winds that blow from the upper left toward lower right. This picture covers an area approximately 3 km (1.9 mi) across and is illuminated by sunlight from the lower left.

How did you do this week? Check back again next week for another WITU Challenge!

March 11, 2009December 24, 2015 by Fraser Cain

Who Discovered the Earth?

Earth as seen from the ISS. Credit: NASA

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When I was first asked this question, “who discovered the Earth”, I thought it was ridiculous. If you use your eyes and look down beneath your feet, you’d be able to discover the Earth. This was how the first humans would have done it hundreds of thousands of years ago. But maybe a better question is: who discovered that the Earth is a planet?

In ancient times, people thought the Earth was the center of the Universe, and that the Sun, Moon, planets and stars rotated around us. Although some thought the Earth was flat, the ancient Greeks, like Plato, were convinced that the Earth was a sphere. They thought that each of the worlds and stars were in crystal spheres surrounding us.

This idea is natural and intuitive. Anyone who stands outside and looks up can clearly see that the stars and the planets are turning around the Earth. But ancients astronomers who studied the heavens found a few problems. Instead of following a straight path in the sky, some of the planets would appear to stop, move backwards, stop again, and then move forwards. To explain this, the Greek astronomer Ptolemy said that the planets were in tiny spheres and made little circles as they orbited around the Earth.

It wasn’t until the 16th century that the Polish mathematician and astronomer Nicolaus Copernicus presented the heliocentric model of the Solar System, where the Earth and the other planets orbited around the Sun. His model of the Solar System was backed up by observations by Galileo, who saw that Jupiter had moons of its own, and that Venus went through phases like the Moon.

It took a few years for the ideas to catch on, and for the scientific establishment to agree that yes, the Earth is just another planet, orbiting the Sun, and it’s not the center of the Universe.

We have written many articles about the Earth for Universe Today. Here’s an article about a new telescope that will let you see what Galileo saw.

Want more resources on the Earth? Here’s a link to NASA’s Human Spaceflight page, and here’s NASA’s Visible Earth.

We have also recorded an episode of Astronomy Cast about Earth, as part of our tour through the Solar System – Episode 51: Earth.

Reference:
NASA Earth Observatory: Planetary Motion