It has been a long time since I’ve updated the Transient Sky blog. I’ll update everyone with more details later. In the meantime, all is well with me. I just ran out of time this summer to keep the blog up to date. A new (or newish) job and 1 year old twin boys will do that.
Has it really been 2 years since I started this blog? I almost forgot that the TransientSky’s birthday is today, September 10.
The idea to do a blog had been in the back of my mind for quite awhile. It finally took the surprise activity of the September Perseids on the night of September 8/9, 2008 to push me to set it up.
Some fun facts about the past two years:
- the Transient Sky was viewed over 336,000 times (162,000 times in the past year)
- 446 posts were made (192 in the past year)
- over 2147 comments were written (1004 in the past year)
- the first post on 2008 Sept 10 was about the unexpected outburst of the September Perseids
- the busiest day was 2010 August 12 when 4,663 people visited to read about this year’s Perseids meteor shower
Updates to this blog have been far and few between. There are lots of reasons for this but a major culprit is the recent stretch of inclement weather here in southern Arizona. I usually blog about objects I can observe but there has been no observing here for close to a month.
The months of July and August are usually the height of the Arizona summer rainy season, or monsoon. This year is no different. Though the ramp-up to actually rain in Tucson was slow, the nights have been consistently cloudy for weeks. As a result I have not made any new comet or meteor observations and even my automated cameras have only been able to catch the rare meteor between the clouds.
Don’t get me wrong, I’m not complaining. My Bachelor’s is in Atmospheric Science and I love the weather. It’s just I spend less time thinking about observational astronomy this time of the year. As a result, I haven’t had much to write on the blog.
Still I am looking forward to at least a clear evening or two to set-up my latest meteor camera. For the past 2 years I’ve been using PC164C and PC164CEX-2 cameras with 4mm f/1.2 lenses. These cameras are relatively cheap but do not have the sensitivity of cameras used by other video meteor observers. Last week I purchased a Watec 902H2 Ultimate which I plan to use with a 6mm f/1.4 lens. The increased sensitivity and larger aperture lens should allow the detection of more meteors, perhaps even twice as many. So here to a clear evening or 2 and some clear nights during the upcoming Perseids.
[Editor’s note: I notice that lots of people are still finding this now a few years old post. If you are trying to find out what those bright stars in the eastern morning sky are (Sep/Oct 2015), go to the front page of this blog at transientsky.wordpress.com for the latest posts.]
When it is dark enough to see a few stars in the sky during evening twilight, look to the East and Southeast. About a third of the way from the horizon to the zenith (straight up), 3 bright “stars” can be seen spread out from due East to the South-South-East (see the chart below).
The 3 “stars” are, in fact, 2 stars and a planet: Sirius, Procyon, and Mars. Let’s start with the Sirius, the southernmost and brightest of the three. Not only is Sirius the brightest of the three (at magnitude -1.5), it is the brightest star in the entire night sky. Only the Moon, Venus, Jupiter, and occasionally Mars are brighter.
Relative to the Sun, Sirius is twice as massive, has a radius 70% larger, and is 25 times more luminous. Still there are many stars in the sky that are even larger and more luminous than Sirius. The reason for its status as the brightest star in the sky is due more to its relatively close distance than its luminosity. At a distance of 8.6 light years, it is the 5th closest stellar system.
Sirius is an A-type star which causes it to shine with a white-blue color. Many times, though, the star will appear to rapidly change color. The reason for this is due to the Earth‘s atmosphere. Turbulence in the atmosphere causes the star’s light to be “bounced” all over the place. The light of the star is made up of many different colors which all “bounce” around differently. As a result, normally blue Sirius can appear to rapidly switch between many different colors when it is close to the horizon (meaning its light is passing through more atmosphere than usual). All stars experience this effect, it is just that Sirius‘ brightness makes it more evident. Watching Sirius when low in the sky with a telescope or just your eyes can be one of the best sights in the night sky.
Next in line is white Procyon, the seventh brightest star in the sky at magnitude 0.3. Procyon appears fainter than Sirius because it is intrinsically fainter (7.7 times brighter than the Sun versus 25 times brighter for Sirius) and farther away (11.4 light years vs. 8.6 light years). It is also less massive (1.5 times solar mass) but a bit larger (2 times solar radius) than Sirius.
The name Procyon comes from Greek and means “before the Dog”. In this case, the “Dog” is Sirius which has long been associated with a dog. Procyon‘s name derives from its slightly more northerly declination which causes it to rise a few minutes before Sirius (at least for northern observers).
The final “star” in the line is the red planet Mars. Last month Mars was at its closest and brightest for the year. At the time its brightness almost matched that of Sirius. Unlike Sirius Mars does not appear to twinkle and is a constant red beacon in the East.
Why does Sirius twinkle and change colors while Mars does not? Check out Phil Plait’s explanation on his Bad Astronomy site.
Today marks one year since the start of this blog. Some fun facts about the past year:
- the Transient Sky was viewed over 174,000 times
- 254 posts were made
- over 1143 comments were written
- the first post on 2008 Sept 10 was about the unexpected outburst of the September Perseids
- the busiest day was 2008 October 7 when 3107 people visited to read about the impact of 2008 TC3 in Sudan
- the most viewed post is “In the Sky This Month – February 2009” with 10,934 views (the interest that month was focused on Comet Lulin which was at its brightest that month)
Plans for year 2 include more comet images (and more comet info in general) and the expansion of the Tucson-based meteor system to include more all-sky fireball detection and the determination of meteor orbits.
I’d especially like to thank Bob Lunsford for contributing his nightly meteor observations. A hearty thanks to everyone who has been reading the blog and to those of you who have been leaving comments. I might not have continued blogging if it weren’t for the kind notes of encouragement and knowing that this information is being read by so many people. Thanks again…
I will be taking a break from blogging for the next few weeks. That will mean that I will be missing the Perseid peak.
So for the rest of the month, postings will be sparse. I do have 2 postings scheduled to be published over the next 2 weeks.
The plan is to be back at the end of August with the usual daily updates on what’s going on up in the sky.
So till then, enjoy the rest of the summer.
Two news stories related to meteors hit the news wires the past few days.
On Thursday came a story about the United States Department of Defense (DoD) classifying data on fireballs. Specifically data taken by their Defense Support Program satellites that monitor the world for signs of missile launches. As it turns out, these satellites were also very good at detecting bright fireballs as they “burn up” in the Earth’s atmosphere. For the past 15 years, the DoD has been sharing fireball data with the scientific community. For some examples, a collection of releases for past fireballs can be found here.
More than 15 years ago, the DoD’s fireball data was classified. This now appears to be the case once again. I have yet to see an official reason for this, though usually the real movie behind classifying information has less to do with the object itself but rather, what the data can tell others about the detection capability of our satellites. Perhaps it has something to do with our soon-to-be upgrade to a newer, more sensitive constellation of satellites. The Space-Based Infrared System (SBIRS) is the DoD’s next generation system and it is possible that the DoD would like to keep its capabilities hush for awhile.
Regardless, the loss of this data to science isn’t too bad. We will still be able to detect and study fireballs over a good fraction of the world. This is becoming more and more possible due to the proliferation of low light camera systems operated by astronomers and for security purposes.
Yesterday’s story comes out of Essen, Germany. There is a report that a 14 year old boy was struck by a meteorite on the hand. As reported by The Telegraph, the boy stated that “At first I just saw a large ball of light, and then I suddenly felt a pain in my hand. Then a split second after that there was an enormous bang like a crash of thunder. The noise that came after the flash of light was so loud that my ears were ringing for hours afterwards. When it hit me it knocked me flying and then was still going fast enough to bury itself into the road.”
Getting hit by a meteorite is an extremely rare event. There is only one documented case, that being of a woman from Alabama being struck back in 1954. So being hit is not impossible. Still the story out of Germany has some inconsistencies.
The meteorite is said to be very small, only the size of a pea. No problem there. It is also reported that it struck the boy on the hand. Again unlikely but no problem. Everything else about the story is problematic.
First let’s run down what a meteorite fall would look like. Many people have seen Hollywood’s version of a meteorite fall. Great examples include the CGI meteors in many of Michael Bay’s movies (Transformers, Armageddon). The meteors are portrayed as relatively small but crashing to the ground at a low angle at 1000’s of miles per hour. They are usually flaming with smoke trails behind them. The meteorites then crash through buildings, bridges, whatever. This is true for large objects.
For your “run-of-the-mill” meteorite-dropping fireball (fragments up to the size of a volleyball), the event will look very different. The original small asteroid will hit the atmosphere at velocities of ~10-70 km/s. Its passage through the atmosphere is violent as air is compressed in front of it in a bow shock. Eventually there comes a point when the pressure is too great and the meteoroid starts to fragment. On many occasions there is a final disruption event. It is usually at this point when the meteoroid has broken into much smaller pieces that a bright flash, or terminal flash, is seen and sonic booms are heard. The sonic boom are caused by the small meteoroid pieces decelerating rapidly below supersonic speeds due to atmospheric drag. So great we have a loud noise and a bright flash just like those mentioned in the German article. Problem is, all of this happens tens of miles up.
So here’s some problems with the “meteorite hits boy” account:
- “30,000 mph space meteoroid“: Well, yes and no. The meteorite might have been traveling 30,000 mph when it first hit the atmosphere but it was moving much, much slower by the time it hit the ground. After disrupting into smaller pieces, the pea-sized meteorite would have been in free fall from a height of many tens of miles or kilometers. Air drag would slow it to its terminal velocity which for a pea-sized rock is rather slow, slower than the speed limit on most highways.
- “saw a large ball of light“: The fireball produced by the meteoroid traveling through the atmosphere would have been bright enough to see even during the day. But, it would have been seen over many 100’s of miles, and I know of no other sightings. Also the fireball would have ended when the meteoroid disrupted. That means the fireball would have ended many tens of miles up and many minutes before the pea-sized piece hit the ground. A rock of that size would have taken a few minutes to fall from 20-40 miles up. When it did hit the ground it would have looked no different then if a small rock had been thrown off of the top of a building.
- “enormous bang like a crash of thunder“: Again any sonic boom caused by the fireball would have occurred many minutes before the meteorite hit the ground. Also those sonic booms would have been heard over many tens of miles.
- “When it hit me it knocked me flying and then was still going fast enough to bury itself into the road“: Not likely since it was traveling so slow. There is a German article that shows the size of the meteorite and its resulting “crater”. You can see it here. Again, a meteorite this small would have hit the ground too slowly to do any damage to the ground. The meteorite would have simply bounced along the ground.
So what does this story tell us? Either it’s a complete hoax and there never was a meteorite fall. Yes, it’s true that researchers in Germany have confirmed that the rock is a meteorite but that doesn’t mean much yet. Anyone purchase a small legit meteorite of this size off of Ebay for a few dollars. It is also possible that this is a real meteorite fall and the boy’s “story” is fabricated. Maybe to live up to many people’s incorrect idea of what a meteorite fall would look like.