Dwarf planets' fifth birthday, 08.25.11

Five years ago yesterday, the International Astronomical Union demoted Pluto to its “dwarf planet” classification. Here at the Wetherbee Planetarium, that is the single most-heard question we are asked: why? Was something discovered about Pluto that made astronomers second-guess it? Did something happen to it? Not at all. It is the other things around Pluto that made the IAU change their minds about what they classify as a planet, though.

As of August 24, 2006, the definition of a planet by the IAU is: “A body that circles the sun without being some other object’s satellite, is large enough to be rounded by its own gravity (but not so big that it begins to undergo nuclear fusion, like a star) and has “cleared its neighborhood” of most other orbiting bodies.” On the first point, Pluto does orbit the sun. On the second point, as far as we can tell it is relatively round in shape. When NASA’s New Horizons probe cruises by in 2015 we will have close up images of the cold planet for the first time in history and we will know for sure what it is like. On the last point, however, Pluto is not exactly a space hog. It rubs elbows –figuratively speaking—with several other objects in our solar system in a region designated as the Kuiper (pronounced ky-per) Belt, some of which are about the same size as Pluto. 

Pluto is only about 1,455 miles in diameter and only 0.2% as massive as Earth. It is tiny, that much is certain. But, it does have at least four known moons: Charon, Nix, Hydra, and the recently discovered P4 (a dismally boring name, we know—NASA presumes will probably be renamed Cerberus in the near future). In orbit around the sun with Pluto are several other objects about the same size as or smaller. Eris is one such object, and was the turning point discovery that led the IAU to re-think their definition of a planet. Another is Haumea, the rapidly spinning dwarf planet that astronomers guess may have radioactive elements in its core. Another is Makemake (pronounced mah-kay mah-kay), a dwarf planet about ¾ the size of Pluto.

Dwarf planets are not just limited to the Kuiper Belt, though. Ceres, another such object, is actually orbiting in our asteroid belt, between the planets Mars and Jupiter.

Each of these objects misses the criteria for a planet in some way, usually in clearing its neighborhood of other objects. They are massive enough to form into relatively spherical shapes and they do orbit the sun, they just usually are not really big enough to push their way through the crowd and clear their own path.

Credit: NASA.

De blob, it glows! 08.19.11

Lyman-alpha blob 1 (LAB-1) is a blob. Not only that, but it is a giant, intergalactic green blob—a giant, intergalactic, green blob that can only be studied with extremely large telescopes, like the (aptly named) Very Large Telescope (VLT) in the mountains of Chile. This is what LAB-1 looks like through the VLT:

Very green, isn’t it? Believe it or not, but it is actually glowing green. That is no filter, no infrared exposure, no x-ray…nothing special done to the photograph. The thing is a glowing, green blob. That is only part of what makes it so fascinating, though.

According to the astronomers who have been studying it with the VLT, the LAB-1 is polarized in a very odd way. That polarization indicates something about what is inside of the blob: “We have shown for the first time that the glow of this enigmatic object is scattered light from brilliant galaxies hidden within, rather than the gas throughout the cloud itself shining,” said lead author Matthew Hayes at the University of Toulouse.

So, LAB-1 is full of galaxies. In case you don’t realize just how huge this blob is, astronomers calculate it is at least 300,000 light years across. That is more than 11 times the distance of our solar system from the center of just our own Milky Way galaxy. This blob is a monster… a creepy, glowing, green monster.

Astronomers are also very interested in LAB-1 because it may literally shed some light on how galaxies are formed. “For a long time now, astronomers have watched stars being born in places like the Great Orion Nebula. Now, it looks like we’ll be able to see where galaxies are born, an exciting prospect,” says Jim Friese of Thronateeska Heritage Center.

 Credit and image credit: NASA.

Liquid water on Mars? 08.08.11

New observations by NASA’s Mars Reconnaissance Orbiter have produced promising evidence that during certain seasons, Mars may actually have liquid water flowing across its surface.

NASA is all a-twitter due to some new images gathered that show “dark, finger-like features” that “appear and extend down some Martian slopes during late spring through summer, fade in winter, and return during the next spring.” That the features recur every cycle-through of the seasons indicate that they are not merely anomalies, but rather something like the swelling of streamlets and rivers here on Earth from thawed snow and ice.

Any liquid water to be found on Mars would most likely be very salty or “briny,” though, according to NASA. Based on what is known at this point of the surface chemistry of Mars, any water to be found on the surface would have a sodium concentration comparable to our own oceans. This lowers the freezing point of the water, making it possible for it to exist in a liquid form in Mars’ sometimes lower surface temperatures.

There are also markings in the soil and rock that are indicative of flowing water.

NASA astronomers are not 100% certain about the find as of this point, however. Spectroscopy scans made by the Compact Reconnaissance Imaging Spectrometer for Mars (CRISM) do not reveal any liquid water.  According to Alfred McEwen of the University of Arizona, Tucson, “the flows are not dark because of being wet…they are dark for some other reason.” The flows he was referring to were the lines in the soil and rock, and the dark lines seen by the Reconnaissance Orbiter. If the ground is completely dry and does not have little streams of brine in it, then it becomes a new mystery that it would lighten just in those areas during the winter.

According to NASA, this is the closest they have ever come to finding liquid water on Mars, and makes it an even more ideal place to visit by astronauts for study.


Credit: NASA.

Playing tag with a "trojan," 08.05.11

Astronomers have recently discovered that Earth is not alone. It seems our planet is being followed, or our Earth is following something else, depending on how you look at it. Earth’s orbit is being shared by an object that astronomers refer to as a “trojan” asteroid.

Thanks to data gathered from the NEOWISE project, astronomers have discovered that there is an asteroid roughly 1,000 feet in diameter that shares almost the exact same orbit as Earth as it travels around the sun. While the asteroid, dubbed 2010 TK7, does at times travel above, below, or slightly to the side of Earth’s orbit, for the most part it seems as if Earth and the asteroid are following in each other’s tracks. 2010 TK7 does travel a little farther away from the sun than Earth does at times, as well.

So, why have astronomers not noticed it until now? It seems that 2010 TK7 is usually difficult to spot because from our vantage point on Earth, it would always appear to be close to the sun. For obvious reasons, this makes it very difficult to observe. The NEOWISE project changed the game though. NEOWISE is an aspect of the WISE (Wide-field Infrared Survey Explorer) mission, a telescope in space far removed from Earth’s atmosphere and the glare of our daylight. The “NEO” part of the name is a side-mission of the probe that searches for Near Earth Objects, bodies that pass within 28 million miles of the sun. By observing 2010 TK7 from outside of our atmosphere, astronomers were able to get a pin point on it and then track it down much easier using other observatories here on Earth, namely the Canada-France-Hawaii telescope on mount Mauna Kea in Hawaii.

Is Earth in danger from its stony stalker? No. According to NASA, trojans are fairly common in our solar system. Neptune, Mars, Jupiter, and even two of Saturn’s moons all have trojans. 2010 TK7 also seems to have a stable orbit, as well, so it is not likely to interfere with Earth.

“It’s as though Earth is playing follow the leader,” said Amy Mainzer, the principal NEOWISE investigator.

Let us hope there are no sore losers in space.

Credit: NASA.

Pluto's family grows, 07.29.11

The Hubble Telescope has added another great discovery to its repertoire; a fourth moon for Pluto. Temporarily assigned the name P4, it was discovered just this month orbiting around the dwarf planet with Charon, Nix, and Hydra, Pluto’s other moons.

Estimated to only be 8-21 miles wide, the tiny little rock is the smallest one to have been found orbiting Pluto. All the other moons orbiting Pluto are at least twice as large. Charon, the largest, is 648 miles across.

Astronomers anxiously wait for the day when the New Horizons spacecraft reaches the Pluto system in 2015. Launched in 2006, New Horizons is outfitted with a visible and infrared imager/spectrometer, an ultraviolet imaging spectrometer, a radio science experiment to measure atmospheric temperature and composition, a telescopic camera, a solar wind and plasma spectrometer, an energetic particle spectrometer, and a dust counter to measure how much dust New Horizons on its way to Pluto.

Credit: NASA. Image credit: NASA, ESA, and M. Showalter.

Pin the tail on the pulsar, 07.18.11

The Chandra X-Ray Observatory has seen something very interesting in recent months. In a paper published in the Astrophysical Journal, several astronomers note how they have witnessed a tail of sorts that appears to be spreading out from a pulsar. The pulsar is a rapidly spinning neutron star, lovingly dubbed PSR J0357+3205.

The blue in this composite image is the Chandra x-ray data, and the yellow is a digitized sky survey. The pulsar is actually at the upper right-hand edge of the “tail,” which is part of the reason why astronomers are left scratching their heads over the situation. If the tail were really originating from the pulsar, the brightest portion should most likely be nearest the star, yet in this case the brightest portion is at the opposite end. This is even more shocking when you do a little math and realize that the tail is somewhere in the neighborhood of 4.2 light years long. This would be a record-setting tail for a rotation-powered pulsar.

There are more reasons than one why this tail should not be originating from the star. We have to keep in mind, too, that astronomers are not 100% certain that this really is PSR J0357’s tail. More observations will need to be made to know for certain if this really is the pulsar’s tail and why it is providing such odd data readings.

Image and story credit: NASA.

Gamma ray flares in binary star are a mystery, 07.07.11

Image credit: NASA.

Something very odd has happened 8,000 light years away in the southern constellation Crux. A binary star system has emitted strange gamma ray flares as the small pulsar star of the pair approached and passed through its closest point in orbit around the large Be-class star.

The Be-class star, designated LS 2883, is surrounded by a disc of gas. As the small neutron star, the pulsar B1259-63, approaches, it emits some gamma rays as it grazes through either side of the disc every 3.4 years.

On January 20 and February 21 of this year, however, when the pulsar approached the larger star, a strange series of powerful gamma ray flares occurred, which was highly out of character. A thorough barrage of scans and studies revealed no anomalies in the stars; no foreign objects, no strange chemical reactions, nothing that would elicit flares like those.

Since the two stars pass by each other that closely only every 3.4 years, it is going to be a while before scientists get another chance to study it again. it is believed that as the pulsar passes thru the disk of gas and dust, that the pulsars powerful magnetic field is accelerating captured electrons to very high energies causing these weird month-long gamma ray displays. It is truly a case where astronomers are finding more and more strange objects or events that can cause a gamma ray burst.

 Credit: NASA.