Posted on by Fraser Cain

Space Questions for the Week Ending April 21st, 2008

Here is a round up of all the space questions answered on Universe Today for the week ending April 21st, 2008. If you have questions for our team, visit this page.

How Big Do Planets Get?
What is the Distance to the Moon?
What is the Far Side of the Moon?
What Kind of Star is Our Sun?
How Big is Apophis?
Why Do Stars Die?
Why are there Black Holes in the Middle of Galaxies?
Why Do Some Scientists Consider Pluto to Not Be a Planet?
Why Haven’t Planets Been Detected Around Alpha Centauri?
Why Can’t We Land on Mars?

Posted on by Fraser Cain

Space Questions Answered

As you can probably imagine, I get an enormous amount of email, both through Universe Today and Astronomy Cast. I read it all, and I try to answer it all – so far, so good; although, I’m a little behind right now.

Instead of just emailing people back answers to their questions, I figured the information would be helpful to many of you. So I’m writing up little mini-articles to answer the questions, and I’m filing them under a special Questions section of the website.

The problem is that I’m going a lot of these, and I’d like to do even more (two birds, one stone). But I don’t want to overwhelm the main page of the site and the RSS feed. I think it would dilute the news focus of Universe Today.

So I’ve got a listing of all the latest questions over on the right-hand side of the page, and they’re in their own Questions section. And I’ll probably provide a summary list of questions once a week in the main feed so you can read any that interest you.

If you’ve got a better idea… I’m all ears. I’ll follow this story with an example of a summary.

If you’ve got a question, here’s where to go.

Posted on by Nancy Atkinson

It’s That Time of the Month for the Moon

Moon in Earths Magnetic tail. Image Credit: Science @ NASA

It happens every month and specifically every time the moon is full. According to scientists, for about three days on both sides of a full moon, the lunar surface could transform from a tranquil, inert landscape to an electrically charged, potentially dangerous environment. During this time, the moon ploughs through Earth’s magnetic “tail” — an extension of Earth’s magnetic field. Out in space, the solar wind stretches out the magnetic bubble that surrounds our planet, creating a long “magnetotail” in the downwind direction. When the moon comes in contact with this field, it could cause lunar dust storms and discharges of static electricity. Future lunar explorers might possibly have to take extra precautions during that time of the month.

“Earth’s magnetotail extends well beyond the orbit of the Moon and, once a month, the Moon orbits through it,” said scientist Tim Stubbs from the Goddard Space Flight Center. “This can have consequences ranging from lunar ‘dust storms’ to electrostatic discharges.”

When the moon crosses this magnetotail, it comes in contact with a gigantic “plasma sheet” of hot charged particles trapped in the tail. The lightest and most mobile of these particles, electrons, pepper the Moon’s surface and give the Moon a negative charge.

Scientists say that on the Moon’s dayside this effect is neutralized somewhat by sunlight. The ultraviolet photons knock electrons back off the surface, keeping the build-up of charge at relatively low levels. But on the nightside of the Moon, where it’s cold and dark, electrons accumulate and voltages can climb to hundreds or thousands of volts.

Stubbs said that astronauts walking across the dusty charged-up lunar terrain may find themselves crackling with electricity like “a sock pulled out of a hot dryer.” Touching another astronaut, a doorknob, a piece of sensitive electronics—any of these simple actions could produce an unwelcome zap. “Proper grounding is strongly recommended,” Stubbs said.

Moon dust could become charged enough to actually lift from the surface. There’s evidence from the Surveyor 7 lunar lander that when sufficiently charged-up, lunar dust particles could actually float above the lunar surface. This dust could cause problems as it clings to spacesuits, clogs machinery, scratches helmet faceplates (moondust is very abrasive) and generally make life difficult for astronauts.

Much of this is pure speculation, however, Stubbs said, as no one has been on the moon during this time. “Apollo astronauts never landed on a full Moon and they never experienced the magnetotail.”

The best direct evidence of this event comes from NASA’s Lunar Prospector spacecraft, which orbited the Moon in 1998-99 and monitored many magnetotail crossings. During some crossings, the spacecraft sensed big changes in the lunar nightside voltage, jumping from -200 V to -1000 V, according to Jasper Halekas of UC Berkeley who has been studying the data.

Scientists also say this phenomenon would be worse during a solar storm.

More research will have to be done regarding this monthly cycle and how it might affect those living on the moon in the future.

Original News Source: Science @ NASA

Posted on by Fraser Cain

How Big Do Planets Get?

Artist's impression of Gliese 436 c

Question: How Big Can Planets Get?

Answer: Here in the Solar System, we have three kinds of planets: the inner terrestrial planets, the gas giants, and the ice planets. Sadly, Pluto is no longer a planet, so we won’t deal with that here. We know how big our planets are, but how big can planets actually get in other Solar Systems. What are the biggest possible planets?

Let’s start with terrestrial planets, like our Earth. We’ll set the size of the Earth and 1 Earth radius, and the mass as 1 Earth mass. We’ve seen that terrestrial planets can get smaller, with Mars and Mercury, and astronomers have detected larger terrestrial planets orbiting other stars.

The largest known rocky planet is thought to be Gliese 436 c. This is probably a rocky world with about 5 Earth masses and 1.5 times our planet’s radius. Amazingly, this planet is thought to be within its star’s habitable zone.

What’s the largest possible rocky planet? For this I put in an email to Dr. Sean Raymond, a post doctoral researcher at the Center for Astrophysics and Space Astronomy (CASA) at the University of Colorado. Here’s what he had to say:

“The largest “terrestrial” planet is generally considered the one before you get too thick of an atmosphere, which happens at about 5-10 Earth masses (something like 2 Earth radii). Those planets are more Earth-like than Neptune-like.”

Gas giants, of course, can come much larger. Jupiter is 317 times more massive than Earth, and 11 times larger. You could fit 1,400 Earths inside Jupiter.

Thebiggest planet in the Universe (at the time of this writing) is TrES-4, which is located 1,400 light years away in the constellation Hercules. The planet has been measured to be 1.4 times the size of Jupiter, but it only has 0.84 times Jupiter’s mass. With such a low density, the media was calling TrES-4 the puffy planet.

And once again, how large can they get? Again, here’s Dr. Raymond:

“In terms of gaseous planets, once they reach 15 Jupiter masses or so there is enough pressure in the core to ignite deuterium fusion, so those are considered “brown dwarfs” rather than planets.”

What is the biggest planet in the Solar System?

Posted on by Ian O'Neill

X-Ray Flare Echo Reveals Supermassive Black Hole Torus

The echo of X-ray emissions from a black hole swallowing a star can be observed as light echos (MPE/ESA)

The light echo of an X-ray flare from the nucleus of a galaxy has been observed. The flare almost certainly originates from a single star being gravitationally ripped apart by a supermassive black hole in the galactic core. As the star was being pulled into the black hole, its material was injected into the black hole accretion disk, causing a sudden burst of radiation. The resulting X-ray flare emission was observed as it hit local stellar gases, producing the light echo. This event gives us a better insight to how stars are eaten by supermassive black holes and provides a method to map the structure of galactic nuclei. Scientists now believe they have observational evidence for the elusive molecular torus that is thought to surround active supermassive black holes.

Light echoes from distant galaxies have been observed before. The echoes from a supernova that occurred 400 years ago (that is now observed as the supernova remnant SNR 0509-67.5) were only just observed here on Earth, after the supernova emissions bounced off galactic matter. This is the first time however that the energetic emissions from a sudden influx of matter into a supermassive black hole accretion disk has been observed echoing off gases within galactic nuclei. This is a major step toward understanding how stars are consumed by supermassive black holes. Additionally, the echo acts like a searchlight, highlighting the dark stellar matter between the stars, revealing a structure we have never seen before.

This new research was carried out by an international team led by Stefanie Komossa from the Max Planck Institute for extraterrestrial Physics in Garching, Germany, using data from the Sloan Digital Sky Survey. Komossa likens this observation to illuminating a dark city with a firework burst:

“To study the core of a normal galaxy is like looking at the New York skyline at night during a power failure: You can’t learn much about the buildings, roads and parks. The situation changes, for example, during a fireworks display. It’s exactly the same when a sudden burst of high-energy radiation illuminates a galaxy.” – Stefanie Komossa

A strong X-ray burst such as this can be very hard to observe as they are short-lived emissions, but a huge amount of information can be gained by seeing such an event if astronomers are quick enough. By analysing the degree of ionization and velocity data in the spectroscopic emission lines of the echoed light, the Max Planck physicists were able to deduce the flare location. Held within the emission lines are the cosmic “fingerprints” of the atoms at the source of the emission, leading them to the galactic core where a supermassive black hole is believed to live.

A molecular torus surrounding a supermassive black hole (NASA/ESA)

The standard model for galactic nuclei (a.k.a. unified model of active galaxies) predict a “molecular torus” surrounding the black hole accretion disk. These new observations of the galaxy named SDSSJ0952+2143 appear to show the X-ray flare was reflected by the galactic molecular torus (with strong iron emission lines). This is the first time the presence of a possible torus has been seen, and if confirmed, astrophysicists will have their observational evidence of this theoretical possibility, strengthening the standard model. What’s more, using accretion disk flares may aid scientists when attempting to map the structure of other molecular toruses.

Strengthening the observation of echoed X-ray emission from the torus is the possibility of seeing variable infrared emissions. This emission signifies a “last call for help” by the dusty cloud being rapidly heated by the incident X-rays. The dust will have been vaporized soon after.

But how do they know it was a star that fell into the accretion disk? In addition to the strong iron lines, there are strange hydrogen emission lines which have never been seen before. This is a strong piece of evidence that it is the debris from a star that came too close to the black hole, stripping away its hydrogen fuel.

Although the X-ray flare has subsided, the galaxy continues to be observed by the X-ray satellite Chandra. Faint but measurable X-ray emissions are being observed perhaps signifying that the star is still being fed to the accretion disk. It seems possible that measuring this faint emission may also be of use, allowing researchers to continue to map the molecular torus long after the initial strong X-ray emission has ended.

Sources: arXiv, Max Planck Institute for Extraterrestrial Physics

Posted on by Tammy Plotner

Astrophotography: NGC 3718 by Dietmar Hager

If southern skies stargazers thought there was nothing to the north to be interested in, then think again. There’s a surprising number of galaxies both close to home and towards the farthest reaches of our Universe in the constellation of Ursa Major. It you think the larger of this 42 million light year distant galactic pair is a little warped, you’d be right. But there’s more than two cosmic cannibals in this astronomy picture.

Originally discovered by Sir William Herschel during this very same month 211 years ago, NGC 3718 became the future study of an astronomer named Halton Arp. For 28 years Dr. Arp was staff astronomer at the Mt. Palomar and Mt. Wilson observatories and while there, he produced his well known catalog of Peculiar Galaxies that are disturbed or irregular in appearance. Needless to say, NGC 3718 became Arp 214: “”Barred spiral, (with a) sharp nucleus, narrow absorption lanes through center”.

But it’s not quiet and it’s alone in the field. Joining warped NGC 3718 around 150,000 light years away is NGC 3729 – another massive galaxy which may be causing its neighbor’s peculiarities. While the warping of galactic discs is common, the process is not quite yet understood. It’s highly possible that tidal forces exerted by neighboring galaxies could be at work and in the case of this pair, it seems to carry through.

NGC 3718 contains an active galactic nucleus (AGN) and is known as a Seyfert Galaxy type 1.9 – one which may contain a massive black hole and is known for violent stars. Through HI mapping, NGC 3718 displays a tidal “tail” which begins on its eastern frontier and extends north towards its companion, NGC 3729. Is this just a case gravitational relationship? One galaxy consuming another? Let’s find out…

It is commonly accepted that when galaxies pass each other that tidal forces draw out the companion galaxy’s stars, gas, and dust in the formation of a spectacular tail. Just as it is commonly accepted that a merger of two spiral galaxies results in a remnant with an elliptical-like surface-brightness profile. In the case of NGC 3718, it would appear (according to interferometer data), the disk warp is evolving into a polar ring. No doubt, its molecular gas content is consistent with elliptical galaxy structure, but the distribution is warping the inner disk. At the same time, 2MASS data shows Arp 214’s main support against gravitational collapse comes from pressure due to random motion of stars as seen in an elliptical galaxy rather than from rotation. The origin of the unusual combination of properties makes the whole scene not only beautiful to look at, but most unique.

But don’t stop there… A closer examination of this picture will also show another another compact set of interacting galaxies as well – Hickson 56. Instead of two, there are five which share similarities with the closer cousins. Located some 400 million light years distant, this Hickson compact group has several catalogue designations including UGC 6527, VV 150, Markarian 176 and Arp 322 and were originally observed by Lord Rosse. According to Halton Arp, “Much print has been dedicated to explaining discordant redshifts in compact groups as unrelated background galaxies. But no one has analyzed the accordant galaxies. It is shown here that when there is a brightest galaxy in the group, the remainder with differences of less than 1000 km s−1 are systematically redshifted. This is the same result as obtained in all other well-defined groups and demonstrates again an increasing intrinsic redshift with fainter luminosity.”

So what’s Paul Hickson take? “Group 56 consists of five galaxies, three of which appear to be in contract and interacting. Two of these three galaxies (B and D) are <a href=”http://www.universetoday.com/11970/galaxy-caught-stealing-gas/”radio source galaxies. Infrared emission is also detected from this interacting system.” Much like it’s closer counterpart, Hickson 56 displays a notable stream of “galaxy stuff” linking its B and C components. An examination of the C galaxy reveals an asymmetric halo but D has a less complex outer luminosity profile. Last, but not least, both the A and D galaxies are Seyfert. More galaxies that have – or are – interacting in the past, present and future.

What’s the chances of seeing some these galaxies yourself? Not bad at all. For the average-to-large telescope, NGC 3718 (RA 11 32 56 Dec +53 01 55) is roughly magnitude 10 to 11 (depending on whose scale you’re looking at) and is noted as a soft, even haze with a dark dustlane seen upon aversion. NGC 3729 (RA 11 34 Dec +53 08), despite its magnitude billing is low surface brightness and requires a large telescope and aversion to detect. As for Hickson 56 (RA 11 32 46 Dec +52 56 28), you’re going to need major aperture and excellent skies to even see a hint of this quintuplet.

Thanks to the photographic magic of Dietmar Hager of Austria, we’re able to enjoy this cosmic portrait. Using a 9″ TMB refractor, the image was captured with a SXV H16 CCD camera and processed with AstroArt Software, Maxim DL and Registax. When Dietmar isn’t busy being a trauma surgeon, he certainly takes outstanding astrophotos and is a member of the MRO imaging team. We thank him for sharing!

Posted on by Ian O'Neill

Branson to be the First to Marry Couples in Space

Artist impression of SpaceShipTwo (Virgin Galactic)

He’s married a couple on board a Virgin America jet, he’s also officiated the marriage of Google’s co-founder Larry Page on his private island in the Caribbean, now Richard Branson wants to marry couples as they reach the apex of their Virgin Galactic flights into space. The British billionaire already has two wedding-related bookings, one marriage and one honeymoon, and it is hoped he will obtain a licence to conduct the ceremonies for more. Certainly unique, but I wonder how popular getting hitched in zero gravity will be…

Richard Branson has broken many records. Not only has he developed one of the largest corporations in the world, he has many personal records under his belt. In 1986, he broke the record for crossing the Atlantic in a powerboat; in 1991 he crossed the Pacific in a balloon, again, breaking all records. He also has experience with weddings. He was ordained for a day last year to marry Virgin America marketing director Dimitrios Papadognonas and Coco Jones on a flight from San Francisco to Las Vegas. So now he wants to combine these two accolades: Break the record for the highest-altitude wedding, officiating the ceremony himself. What’s more, he already has his first booking.

Richard Branson (dailymail.co.uk)

The world’s first space-honeymoon belongs to Virgin Galactic advisor George Whitesides and his fiancée Loretta Hidalgo. They have reserved tickets for the Virgin Galactic maiden flight, costing $100,000 each. As for the wedding, the couple who have reserved their tickets remain unknown. It is hoped however that Branson will be there to talk them through their vows:

“We have had two bookings involving marriage, one to get married in space and the other for the couple to have their honeymoon in space. It is possible that Richard could obtain a licence to conduct the marriage.” – Virgin Galactic spokesman

Virgin Galactic already has 200 people booked to fly into space proving there is a market for space tourism out there. Construction of SpaceShipTwo has already begun and the first test flights are expected to commence in 2009.

If you have the cash and want the wedding you’ll never forget, this might be the answer to the millionaires out there. For me, the risk of feeling a bit queasy after the stag party the night before might be enough to ground me from taking any risks in zero-G…

Source: Daily Mail (UK)

Posted on by Ian O'Neill

Soyuz Crew Safe After a Violent Re-entry and Landing 400km Off-target

The highly successful Russian Soyuz spacecraft (NASA)

The Russian Soyuz re-entry capsule, carrying the first South Korean astronaut back to Earth, suffered a “ballistic re-entry” on Saturday, putting the capsule 400 km (250 miles) off-target. This is the second time in a row that the return vessel has landed off course; even officials were shocked about this inaccuracy. The astronauts endured forces of up to 10-G as the capsule took a very steep trajectory as it dropped through the atmosphere for three and half hours. Fortunately the three crew members are safe and well. What’s the explanation for the mishap? An unauthorized change to the flight plan and an old naval superstition…

South Koreas Yi So-yeon spent 11 days at the International Space Station (AFP/BBC)
At least the whole crew returned to Earth safely after their violent re-entry, but questions are being asked as to why the capsule landed so far off course and 20 minutes behind schedule.

The Russian TMA-11 craft touched down on the Kazakh steppe at 4:51am Saturday morning after making the long trip through the atmosphere. On board was South Korea’s first astronaut, Yi So-yeon, Russian cosmonaut Yuri Malenchenko and American Peggy Whitson, who broke NASA’s record for time in space. Whitson spent a total of 377 days orbiting the Earth whilst carrying out experiments on the International Space Station. Yi So-yeon spent 11 days on the station after a flawless Soyuz launch (April 8th) and stay in space. However things seemed to go wrong as the trio undocked from the station and headed home.

The Soyuz descent module (highlighted) (NASA)

According to the BBC report, Russian officials blamed the crew for making changes to the flight plan just before re-entry. This change was not communicated to mission control who assumed the original plan was going ahead. The result from this change was a steeper than normal angle on entering the atmosphere (a.k.a. a ballistic re-entry), putting the capsule hundreds of kilometres off course. Rescue helicopters took 25 minutes to arrive to the landing site where the crew waited in temperatures of 6°C (43°F). Other than the off-target location, apparently the touch-down went according to plan.

See the BBC video coverage of this event »

However, not all sources indicate the sole blame falling on a lack of communication between capsule and mission control. In a controversial statement to reporters, Federal Space Agency chief Anatoly Perminov placed some of the blame on an old naval superstition that the female-dominated crew were bad luck and the first female commander (Peggy Whitson) was responsible for the change of plan.

“You know in Russia, there are certain bad omens about this sort of thing, but thank God that everything worked out successfully. Of course in the future, we will work somehow to ensure that the number of women will not surpass [the number of men].” – Anatoly Perminov

Naturally, this kind of statement will have caused a bit of a stir. A reporter pushed for elaboration and Perminov continued, “This isn’t discrimination. I’m just saying that when a majority is female, sometimes certain kinds of unsanctioned behaviour or something else occurs, that’s what I’m talking about.”

It looks like some space agency officials still believe in old naval superstitions, let’s hope it doesn’t influence future female involvement in the Russian space program. If anything, as the whole crew is safe and well, the South Korean and American should be considered the mission’s “lucky charms”.

Update: April 22nd – Read the developments on this story…

Sources: BBC, Yahoo!, Space.com

Posted on by Nancy Atkinson

The Debate Continues: Water or Land Landings for Orion

The development of Constellation is continuing, the U.S. program that will replace the shuttle and send astronauts back to the moon. Two unresolved issues have stood out specifically for the Orion crew vehicle: Orion is currently too heavy for the Ares vehicle to launch it from Earth, and the decision on whether Orion will land in water or on land has yet to be determined. Originally, land landings were the preferred choice, but last December, it appeared program managers were leaning towards returning to the water landings seen during the Apollo era. But recently NASASpaceflight.com reported on a possible solution for the weight problem that could potentially provide an improved capacity for landing on land as well.

Needing to save mass on Orion to make it lighter prompted engineers to re-design the airbags that would be part of the vehicle to as a “contingency Land Landing requirement,” according to the article on NASASpaceflight.com. The new airbag system uses a smaller number of airbags than the original concept. As a result, the new airbag system is lighter. Engineers believe the new “back-up” system could possibly work well enough to be the primary system and allow land landings to be what NASA calls “nominal,” or the primary, preferred means of landing.

The upside of landing on land is that there’s a better chance of being able to reuse the command module, as opposed to landing in the ocean. Additionally, there’s some who believe returning to water landings is a step backwards for human spaceflight.

The airbags in the proposed new design are deployed out of the lower conical backshell on the Orion vehicle. Just before landing , the airbags would inflate and wrap around the low hanging corner of the heat shield. Upon landing, the airbags are vented at a specific pressure so that they collapse at a controlled rate to ease off the energy load of the spacecraft.

Although this new system has yet to undergo detailed analysis, initial results are viewed as promising on the ability to reduce crew loads to an acceptable level.

NASASpaceflight.com reported that another notable challenge for the Orion vehicle relates to maintaining the spacecraft’s orientation to minimize chance of tumbling during descent. A Reaction Control System (RCS) is being developed, which supposedly is preferred by engineers over retro rockets.

NASA did report last week the successful first full-scale rocket motor test for Orion’s launch abort system. This system would separate the crew module from Ares if an emergency occurred during launch.

Original News Source: NASASpaceflight.com

Posted on by Fraser Cain

How Big is Apophis?

Radar image of asteroid Apophis.

Question: How Big is Apophis?

Answer: In case you haven’t heard, Asteroid 99942 Apophis is a near Earth asteroid that astronomers think will make a close flyby to the Earth in 2029. When its trajectory was first calculated back in 2004, it had one of the closest visits to Earth astronomers had seen, and had a 2.7% chance of hitting the Earth.

But follow-up observations brought that risk down to 1 in 45,000. Right now, astronomers think that Apophis is essentially no risk to the Earth. In April, 2008 media reported that a 13-year old German student had caught a math mistake made by NASA, and the risk of an Earth strike was actually 1-45. This later turned out to be a hoax.

Because of its close approach to Earth, space advocacy societies, including the Planetary Society think that the Apophis asteroid would make an ideal target for a human mission, and allow engineers to test out strategies for moving asteroids away from dangerous Earth-crossing orbits.

So back to the original question, how big is Apophis? The best estimate puts it at 270 meters (885 feet across), and it has a mass of 2.1 x 1010 kg. To give you a sense of scale, the Eiffel Tower in Paris is 324 meters tall.

But now you know its mass and size, you’re probably wondering: what would happen to the Earth if it struck? NASA estimated that a strike by Apophis would release the equivalent of 880 megatons of energy. Just as a comparison, the object that carved out Meteor Crater in Arizona probably released 3-10 megatons of energy.

If Apophis struck land, it would flatten thousands of square km of land, killing millions of people if it hit a densely populated area. But it wouldn’t cause the kinds of long term climate destruction that 1 km and larger asteroids can do. If it hit an ocean, it would create devastating tsunamis in all directions.

Here’s an article explaining techniques that might be used to move an asteroid. And here’s NASA’s official page on Apophis.