Posts Tagged ‘asteroids’

Phaethon Cometh

Posted: 7 December 2007 in Uncategorized
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One of the dark horses of the inner solar system makes its closest approach to Earth since it was discovered in 1983 soon.  Phaethon is an asteroid (perhaps the burnt out core of a comet).  We pass through its debris trail every December, resulting in the Geminid meteor shower.  This year, the Geminids will peak on December 13-14th.  Bonus:  the Geminids are likely to be even better than the Perseids this year.  Unfortunately, it’s cold out.  Plus I have an exam on the 14th.  This meteor shower didn’t get the memo I sent out that it had to fall on a weekend.

So what’s special about the Geminids?  Phaethon is a source of denser meteors than are found in most other meteor showers.  This results in meteor paths that can be jagged and more meteors that break apart and split.  According to Space.com, the Geminids have a history of slow, bright meteors and faint meteors, but few medium-brightness ones.  The moon will be a faint crescent and peak times will see 60-120 meteors per hour.

For more on the discussion of whether Phaethon is a burnt out comet or an asteroid, check out Astroprof’s page on the topic.  If you happened to download Celestia when I talked about it before, you can also download an add-on that includes a few thousand near-Earth objects.  Phaethon is included in that pack (it doesn’t come with Celestia by default, or at least I couldn’t find it).  That site (the Celestia Motherlode) has a number of very awesome additions to Celestia, so I recommend checking it out.

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Rosetta

Posted: 14 November 2007 in Uncategorized
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The second fantastic photo of Earth from space I’ve come across in as many days was taken by the Rosetta comet probe sent up by the European Space Agency (ESA). The Rosetta craft made big news recently when it was mistaken for an asteroid that was going to make a near-Earth pass. The Minor Planet Center failed to cross check the object against known probes and so sent out an alarm before realizing their mistake. Rosetta is using the Earth as a slingshot to propel it into the outer solar system (4.4 billion miles) to the Comet 67/P Churyumov-Gerasimenko. After that it will return to Earth for another gravitational slingshot.

Earth as seen by the Rosetta probe.

Mars, Phobos, or Deimos?

Posted: 8 November 2007 in Uncategorized
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Which will be the newest extraterrestrial body humans will set foot on? (Aside from the moon, of course.) According to Pascal Lee of the Mars Institute, “[Phobos and Deimos] are the most accessible planetary bodies in our solar system.” New Scientist has a report on the conference at Ames Research Center on Wednesday where ideas were thrown around for the human exploration of Mars. Astronauts could set foot on one of them within a decade. So cool.

Phobos and Deimos are similar in nature to C-type asteroids. Phobos is porous and has an extremely low orbit, subjecting it to tidal forces. These forces will eventually cause it to either break up or crash into Mars (in about 30-80 million years). In the meantime, it would make an excellent base of operations for a manned mission to Mars. Escaping the gravity of Phobos or Deimos would be much less difficult than escaping that of Mars.

One of the biggest problems with such a venture according to the New Scientist article is dust. With such a weak gravitational field, Phobos could have as much as 5 meters of dust accumulated on its surface. Also, a long journey like this would expose astronauts to too much radiation, giving them a 5% chance of dying of radiation poisoning (above the 3% NASA allows). But wouldn’t it be cool, to stand there on that dusty rock, a mere 6000 miles above Mars, looking at that giant red orb in the sky?

Add one more killer asteroid

Posted: 5 October 2007 in Uncategorized
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Another potential killer asteroid was rediscovered after being lost since the 60’s.  Revolving around the sun once every 4.7 years, this asteroid isn’t a threat for the foreseeable future, but if the orbit shifts, that could change.  It’s just one more to keep an eye on, joining a family of 886 objects larger than 500 feet across that pass within 4.6 million miles of Earth, according to Space.com.  Good times.

Sulu gets an asteroid

Posted: 3 October 2007 in Uncategorized
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George Takei, better known as Sulu to the world of non-hardcore Trek fans, now has an asteroid named after him. I say non-hardcore Trek fans because hardcore Trek fans know his real name. Or maybe it’s semi-hardcore. Super hardcore probably have lost all touch with reality and believe he really is Sulu. In any case, asteroid 7307 is now 7307 Takei, joining the mighty ranks of 4659 Roddenberry and 68410 Nichols (Lt. Uhura’s real name). In an unfortunate bit of news, the asteroid was knocked off a balcony roof in New York and fell to its death.

Dawn liftoff

Posted: 28 September 2007 in Uncategorized
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NASA’s image of the day is the Dawn spacecraft launching via a Delta II rocket. It’s heading to two asteroids: Ceres (actually a dwarf planet) and Vesta. The journey will take several years. In March 2009, Dawn will slingshot around Mars to arrive at Vesta in September of 2011, where it will stay for about seven months. After that it will head to the dwarf planet Ceres, a journey of three more years, arriving in February of 2015. Five months later, the primary mission will end.

The Dawn spacecraft will be using an ion propulsion system. This allows the spacecraft to travel with much less weight. An electrical charge is used to accelerate Xenon atoms at rates 10 times faster than chemical fuels. Because the force it takes to accelerate something depends on its mass (F = ma), the lighter (less massive) a spacecraft is, the less it takes to move it. Petroleum is heavy, so using it for a spacecraft really doesn’t work very well, but it is used for launch vehicles like the Delta II rocket. The petroleum used is known as RP-1 (Refined Petroleum) and is mixed with liquid oxygen. The ion propulsion drive is fuel efficient but not exactly speedy. No one is going to brag about 0 to 60 mph in 4 days. The bonus is, the spacecraft only uses 10 ounces of fuel per day at full burn. At that rate, Dawn can go about 1500 days, but it won’t need to be at full burn every day.

 

Dawn launch - courtesy NASA.

Dawn

Posted: 12 September 2007 in Uncategorized
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Dawn on the launchpad awaiting the September 26th launch.The Dawn spacecraft is currently sitting on the launchpad at Cape Canaveral, where it will wait until September 26th for launch. NASA always chooses these vague, optimistic names for spacecraft. The Mars rovers have names like Spirit and Opportunity or old probes with names like Voyager and Pioneer. Of course there are the dreadfully functional names like Mars Polar Lander. And of course, the odd barbarian always finds his way into the crowd: Viking. But I think that Dawn is named well. Here we have a spacecraft that is actually going to the asteroid belt and examine the asteroid Vesta and the dwarf planet (ala Pluto) Ceres. Of course, Ceres is a smidge smaller than Pluto having a radius of 475 km versus Pluto’s 1153 km. The great thing about asteroids, though, is that their escape velocity is relatively minor. Ceres is only 1.2 km/s, or about 4320 km/h (2685 mph). This is nothing when you consider the escape velocity of Mars is 18,097 km/s (11,247 mph). The bonus here is that spacecraft going to Ceres expend less fuel in their approach (slowing down) and less fuel on take-off.

Dawn will only be orbiting these bodies, not landing on them. Dawn’s mission is to study the formation of these two objects, but I think the longterm effects are much more important. For one, it will give us experience in working with the asteroid belt. Many sci-fi writers have speculated that the asteroid belt will be a great place for space stations and mining operations. If Dawn finds the right things, it could spur further exploration of the asteroid belt. Maybe one day my great grandchildren will visit the space mining museum on 243 Ida (below) and spend the night at the bed and breakfast on its moon Dactyl (the speck on the right).

The asteroid 243 Ida and its moon Dactyl.  NASA image: public domain.