Asteroids (1) : Earth (2) – Welcome to the Interplanetary Shooting Gallery

Rocks are being thrown at us, but we haven’t noticed

Artist impression of an asteroid impact - don't worry, this doesn't happen very often... (Getty Images)
Artist impression of an asteroid impact - don't worry, this doesn't happen very often... (Getty Images)

On October 7th, a small asteroid called 2008 TC3 exploded in the skies above Sudan. On October 9th, a metre-wide asteroid named 2008 TS26 buzzed Earth’s atmosphere by only 7000 km. Then on the 21st (Tuesday) a slightly bigger piece of rock called 2008 US missed us by 25,000 km. It sounds like it’s getting dangerous out there, especially when considering the last recorded object (2004 FU162) to come screaming past the Earth (at 6500 km) happened in 2004.

But don’t be concerned. Small asteroids are being thrown at us all the time; asteroid hunters are just getting better at spotting them…
Continue reading “Asteroids (1) : Earth (2) – Welcome to the Interplanetary Shooting Gallery”

First Image of Asteroid TC3 Impact Fireball… From Space

2008 TC3 generates a huge fireball according to weather satellite Meteosat 8 (Zdenek Charvat, Czech Hydrometeorological Institute)
2008 TC3 generates a huge fireball according to weather satellite Meteosat 8 (Zdenek Charvat, Czech Hydrometeorological Institute)

There may not be any ground-based imagery of the 1.1-2.1 kT fireball after asteroid 2008 TC3 hit the Earth’s upper atmosphere above Sudan, but we now have the first satellite observation of the impact. 2008 TC3 (a.k.a. “Brian” as I lovingly named it in my previous post) hit at 02:43am (UTC) yesterday morning, three minutes before the predicted re-entry. This is a huge moment for asteroid hunters: 2008 TC3 is the first ever asteroid to be discovered and accurately forecast to hit our planet.

The above image was taken by the weather satellite Meteosat 8, as Jiri Borovicka of the Czech Academy of Sciences explains: “The explosion was visible in all 12 of the satellite’s spectral channels, covering wavelengths from 0.5 to 14 microns,” he said. “The satellite takes pictures every five minutes; the fireball appeared at 0245 UTC and had faded away by 0250 UTC.”

It’s great to finally see the explosion of the first ever predicted asteroid impact. I think we all feel a little safer now

Source: Space Weather

Historic Asteroid 2008 TC3 Hits Earth as Predicted

Predicted region of atmospheric impact according to infrasound observations (Peter Brown, University of Western Ontario)
Predicted region of atmospheric impact according to infrasound observations (Peter Brown, University of Western Ontario)

2008 TC3 wasn’t a particularly interesting asteroid. It wasn’t very big (only 1-5 metres wide) and it didn’t really stand out as being special (if it was special, we didn’t have any time to realise it anyway). If 2008 TC3 was in a crowd of other asteroids you wouldn’t have picked it out. In fact, it was that “normal” that it wasn’t named, it just kept its original asteroid designation number. 2008 TC3 was an ordinary piece of space rock in an extraordinary situation.

This was the first ever asteroid that astronomers were able to track and predict (with high precision) where and when it was going to hit Earth. Sure enough, astronomers using the Mt. Lemmon telescope in Arizona as part of the NASA-funded Catalina Sky Survey for near-Earth objects discovered 2008 TC3 before it hit Earth, enabling us to be forewarned a whole six hours before impact. If the object was any larger, astronomers will have (for the first time) been able to warn people on the surface, thus saving lives.

In fact, asteroid 2008 TC3 is so special that I’m going to give it an unofficial name: Asteroid Brian*.
Continue reading “Historic Asteroid 2008 TC3 Hits Earth as Predicted”

Small Asteroid 2008 TC3 Will Hit Earth Tonight

Artist impression of a meteorite entering the Earth's atmosphere (©Leonard Wikberg III)
Artist impression of a meteorite entering the Earth's atmosphere (©Leonard Wikberg III)

A newly discovered asteroid called 2008 TC3 will (with a 99.8-100% probability) hit the atmosphere over northern Sudan at 2:46 UTC (Oct 7th). The piece of rock will not threaten people or structures on the surface, it is likely to burn up during re-entry as a magnificent “air burst.” Estimates suggest that as 2008 TC3 burns up, it will detonate with an energy of a kiloton of TNT.

2008 TC3 is between 1-5 meters in diameter, so it’s not a threat by any means, but it should create a spectacular display. Usually the bright meteors we observe are generated by debris no bigger than a grain of sand, so this will be a huge astronomical event in comparison. The giant meteor will be visible from eastern Africa travelling very quickly from north-east to south-west and it is expected to create a very long trail as it will enter the atmosphere at a very shallow angle.
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Nancy Writes for Wired: “Giants of Earth and Space”

Gran Telescopio Canarias located on La Palma, Spain - one of the giant observatories looking at the stars (GTC)
Gran Telescopio Canarias located on La Palma, Spain - one of the giant observatories looking at the stars (GTC)

My Universe Today colleague and superb science writer Nancy Atkinson has written her first article for Wired.com! This is obviously a huge step as her writing has instantly accessed potentially millions of readers. So, CONGRATULATIONS NANCY!

Nancy was approached by Wired to put together an article about some of the biggest and boldest observatories on Earth. Her writing is accompanied by some stunning photography of these giant structures that include the Hobby-Eberly Telescope (HET) on Mount Fowlkes, Texas (sporting 91 separate one-meter hexagonal mirrors); the W. M. Keck Observatory on Hawaii’s Mauna Kea volcano (with two 10-meter mirrors composed of 36 hexagonal segments); and my personal favourite, the Very Large Telescope Interferometer on the Andes mountaintop of Cerro Paranal, Chile (four 8.2-meter diameter telescopes working in tandem). There is a huge amount of information in Nancy’s excellent article, making it more than worthy of being included in this hugely popular science & technology magazine website.

Be sure to check out “Giants of Earth and Space,” by Nancy Atkinson over at Wired.com.

Enigmatic Magnetar Blasts to Life Inside Our Galaxy

An artist impression of one of the most intensely magnetic phenomena in our known Universe, the magnetar (ESO/L. Calcada)
An artist impression of one of the most intensely magnetic phenomena in our known Universe, the magnetar (ESO/L. Calcada)

It was identified as a gamma-ray burst, resulting from a massive explosion in a distant, young galaxy. Then astronomers realised that this flaring object was much closer to home, in fact it was a gamma-ray source within the Milky Way. Astronomers detected 40 visible-light flashes, only for the source to vanish as quickly as it mysteriously appeared. So what generated this huge firework display for astronomers to originally mistaken it for a gamma-ray burst?

It seems we have an answer, and it has surprised many.

One of the rarest objects ever observed may have sprung to life in our galaxy after a long period of calm. This object is a young neutron star with a magnetic field a billion billion times stronger than the Earth’s, otherwise known as a magnetar
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Why Can’t we see the Oort Cloud?

Hubble Space Telescope observation of Polaris – looking through the Oort Cloud, but not resolving any comets (Hubble)

The Oort Cloud is a mysterious entity. Located on the outskirts of the Solar System, this hypothetical region is probably the source of the long-period comets that occasionally pass through the inner planets’ orbits. The strange thing about these comets is that they have orbits inclined at pretty much any angle from the ecliptic which suggests their source isn’t a belt confined to the ecliptic plane (like the asteroid belt or Kuiper belt). Therefore, their proposed source is a cloud, acting like a shell, surrounding the Solar System.

OK, so we think the Oort Cloud is out there, and there is a lot of evidence supporting this, but why can’t we see the Oort Cloud objects? After all, the Hubble Space Telescope routinely images deep space objects like stars, galaxies and clusters, why can’t we use it to see embryonic comets within our own stellar neighbourhood?
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No, An Alien Radio Signal Has Not Been Detected

Schematic showing Sagittarius A crossing the beam of Indlebe on 28 July 2008 (Stuart MacPherson)
Schematic showing Sagittarius A crossing the beam of Indlebe on 28 July 2008 (Stuart MacPherson)

Some great news from Durban University of Technology in South Africa, their newly built Indlebe Radio Telescope detected its first signal late last month. “On the evening of 28th July 2008, at 21h14 local time the Indlebe Radio Telescope, situated on the Steve Biko campus of the Durban University of Technology (DUT), successfully detected its first radio source from beyond the solar system. A strong source was detected from Sagittarius A, the centre of the Milky Way Galaxy, approximately 30 thousand light years away,” says the statement by Stuart MacPherson. This will be an invaluable resource for students and research projects; a great achievement.

Although this should be the focus of attention, it looks like social bookmarking may have struck again. The DUT announcement was picked up by Digg and the Internet population drew their own conclusions. Interestingly, the Russian mainstream media was listening and interpreted the Internet buzz as proof that an alien radio signal had been detected in the centre of our galaxy…
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Meteor Alert: Perseid Shower Now Active (Update)

The 2004 Perseid meteor shower (© Fred Bruenjes)
The 2004 Perseid meteor shower (© Fred Bruenjes)

Update (1:30am PST): Spotted three very bright and several dim meteors in a 10 minute observation period (not bad for LA skies!). The bright meteors left strong, and long-lasting ionization trails that were visible for a couple of seconds. It can only get more active, so I’ll be back outside soon…

OK, so for my second attempt at seeing the Perseid meteor shower, I’m donning the shorts and T-shirt (not your usual astronomy garb, but this is California!) and getting out into the back yard. I’ll be looking North-East, through a clearing in the palm trees and keeping an eye open for the Perseus constellation. As you can probably tell, I’m no practical astronomer, but my wonderful colleague Tammy Plotner’s enthusiastic writing is infectious and I want to catch some shooting stars with my own eyes!

Wish me luck…
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Observing Red Dwarf Stars May Reveal Habitable “Super-Earths” Sooner

A planet orbiting a red dwarf (NASA)

OK, so if you’re an exoplanet hunter, which stars would you focus your attention on? Would you look at bright blue young stars? Or would you look at dim, long-lived red stars? If you think about it, trying to see a small exoplanet eclipse (or transit) a very bright star would be very hard, the luminosity would overwhelm any attempt at seeing a tiny planet pass in front of the star. On the other hand, observing a planet transiting a dimmer stellar object, like a red dwarf star, any transit of even the smallest planet will create a substantial decrease in luminosity. What’s more, ground-based observatories can do the work rather than depending on expensive space-based telescopes…
Continue reading “Observing Red Dwarf Stars May Reveal Habitable “Super-Earths” Sooner”