My attempt at explaining the weird goings on in the comet ISON videos from SOHO and SDO. Enjoy (and please forgive my rambling – I had so many technical problems I’m just glad I got the dumb thing published!)
The folks at the Solar and Heliospheric Observatory (SOHO) have been busy on this Thanksgiving Day taking images of ISON’s flight around the Sun. While we had hoped ISON might survive its closest approach, the truth is that a sungrazing comet’s chance of surviving a trip around the Sun is remarkably similar to that of a snowball in hell.
Even so, the results are quite surprising. Take a close look at the last few frames of the video:
Let me explain the video a bit: The Sun is at the very center of the image, but in order for SOHO to take images of its outer heliosphere, it must block out the Sun itself. The Sun’s disk is drawn in white so we can tell exactly where it is, but the occulting disk needs to be considerably larger than the Sun itself in order to block out its light.
ISON enters the field of view in the lower right, peaking in brightness at around 0:10 (the horizontal line it produces is not real – it’s an artifact due to the detector saturating, a process called blooming).
ISON starts to dim as it goes “under” the occulting disk, and that’s typically an indication that the comet is breaking up. But then something appears to emerge from underneath the disk, and it’s pretty damn bright!
In the updated image taken at 12:30 UTC on November 29, the object has moved farther away and continues to appear rather comet-like:
Here’s another view of the event, taken with SOHO’s LASCO C2 instrument, which has a close-in field of view:
All of this is to say…I have no idea. Comets are very strange creatures, and they surprise us all the time. At this point, I can hardly make any conclusions, and from what I’m reading on the interwebs even comet specialists are stumped. And that’s the best part of all of this. Being surprised by nature is part of what makes science so fun!
ISON may very well be the little comet that could.
This coming Tuesday, November 19, the US Air Force will be launching a Minotaur I rocket from te Mid-Atlantic Regional Spaceport at NASA’s Wallops Island, VA flight facility. The mission, called Minotaur I/ORS-3, will be carrying twenty-nine (yes, 29!) satellites into orbit. Best of all, it’s going to be a night launch so it should be very visible to everyone in the Eastern United States.
The launch is being carried out by Orbital Sciences Corp, and they have a handy page set up with maps showing where and when viewers should expect to be able to spot Minotaur as it ascends. Here’s a map to give you an idea of when you’ll be able to spot the launch from your location:
Their site has several simulated ground views of where the rocket should appear from various locations such as Washington DC, Raleigh NC, Philadelphia PA, Liberty Park New Jersey, and New York City among others.
Since I live in none of those places, I downloaded their Google Earth kmz file and created some visualizations for myself and my friends. Here’s a simulated view from my house in Westminster, MD:
Here’s a view from Frederick, MD:
And here’s a view from Springfield, PA for my Delco peeps:
What you should expect to see, and when
The Minotaur is a solid-fuel rocket, which is ideal for viewing at night because it produces an orange/red “flamey” tail that’s relatively easy to spot. “Relatively” is the key word here because at the locations I’ve chosen, the rocket will appear as a tiny red dot moving quickly across the southeastern sky in an arc like what you see in the images above (except at night).
The launch window is from 7:30 – 9:30 pm on Tuesday. Naturally, they’ll try to launch at 7:30 but keep in mind that the farther you are from the launch site, the longer it will take for the rocket to clear the horizon. The images I show above assume a flat horizon all the way to Wallops, and we know that’s not the case. Fortunately, Orbital created a first sighting map to give you some idea of when you should expect to see the rocket clear the horizon (keep in mind though that it would have already moved slightly eastward by the time you pick it up).
Minotaur is a four stage rocket, so it will appear to dim and then light up again a little further to the east as the expended stage is jettisoned and the next stage ignites.
Monitor the launch on your smart phone, but watch the timing
If you have a smart phone and a good 3G or 4G signal, you can monitor the countdown on the NASA app for iPhone or on Wallops’ live stream. Android users might want to check out the What’s Up at Wallops app, which contains a compass showing the precise direction for launch viewing1.
…keep in mind that everything coming down to your tablet or cell phone is probably going to be a minute or so after the fact. If you wait until you hear them say “liftoff” to go outside and look, the rocket may already have reached orbit. Instead, listen to / follow the countdown to make sure the launch time hasn’t changed, and then use your cell phone’s clock to make sure you’re really at L-0, *then* look toward Wallops!
Watch with friends to increase your chances of actually seeing it
Even at night, the Minotaur may be hard to spot, especially if this is your first time. Haze, aircraft, and all kinds of things can be in the field of view to confuse you even more. If you’re with a small group of people, chances are that one of you will be able to spot it and point it out for the rest. Watch with friends to increase your chances!
Watching and tracking rocket launches is challenging and fun, especially at night. Hopefully the weather from your location will cooperate and you get to see an amazing show. Good luck!
- Sadly, there’s no iPhone version for that yet. Grrr…. ↩
Every frame in the video you are about to see is a photo taken from astronauts on board the International Space Station. Those photos are free to the public, free to admire, and free for gifted artists like Knate Meyers to string together in a mesmerizing time lapse video. Go full screen, hit HD, turn up your speakers, and behold:
I love how several of the images used in the sequence are long exposures, allowing for the stars and the surface of the Earth below to blur into trails as ISS orbits at over 17,500 miles per hour. At 0:40, you can see one of the docked Soyuz spacecraft firing it’s attitude jets to help the space station maintain its orientation.
ISS’ orbit is inclined 51.64 degrees from the equator, sending it fairly far up north and far down south. This gives astronauts onboard a ringside view of the Aurora Borealis and Aurora Australis, which appear as green shimmering curtains of light.
And the stars! Of course they are the same stars we can see here on Earth (or would be able to see if we lived in the right locations) but there’s no comparison to the view you can get from up there. Wow!
At 17,500 miles per hour, there’s a sunrise every 90 minutes. Even though the video is primarily of images taken at night, it does a wonderful job of capturing the regular cycle of night and day.
Knate has some other time-lapse videos of the night sky, taken from this side of Earth that are really worth checking out as well.
July 19, 2013 was a very special day in the history of humanity. From a distance of 898.414 million miles (1.445858 billion kilometers) from Earth, the Cassini spacecraft made this stunning mosaic of the ringed planet as it eclipsed the Sun. The result is nothing less than breathtaking:
There is simply no way to adequately convey the beauty of this image in mere words. Instead, I invite you to view the colossal 9000×3500 pixel mosaic itself. Take a moment for it to load and just scroll around for a while. (Be sure to check out the annotated version of the mosaic as well.)
Cassini was “behind” Saturn in the sense that it was on the side of Saturn opposite the Sun. This gave the Cassini team an opportunity to create a mosaic of the entirety of Saturn and its rings backlit by the Sun.
The planet itself appears in silhouette, but not completely. Notice that part of Saturn’s dark side is illuminated by light reflected off the rings themselves. In other words, “Ringshine.”
Cassini was about 17 degrees below the plane of the rings, allowing the rings to appear as an ellipse in this view. And that’s a good thing because it really allows us to explore the rings in a very unique way.
The outermost E-ring appears diffuse and ghost-like. It’s created by geysers of ice crystals erupting from Enceladus. If you zoom in on the left side of the image, sure enough you’ll spot Enceladus with geysers erupting!
There are several other moons to be seen in this image, and some background stars as well. But as amazing as this image is, what makes it truly interesting is that you, me, and everyone on Earth are in it.
The day Earth smiled
At the bottom right of the mosaic is a tiny pale blue dot. That’s us. That’s you and me and the whole of humanity right there on a tiny, pale blue dot.
We are 898.414 million miles (1.445858 billion kilometers) in the background in this image. Zooming in reveals both our home planet and Moon. That’s all of us, right there, looking up toward Saturn, and smiling.
That’s what makes this image of Saturn so special, and why July 19, 2013 is a special day in the history of humanity. Human beings from all over that blue dot looked up toward Saturn while Cassini was taking its picture, smiled, and waved.
Here’s looking at you, Saturn!
Update 2013-11-14: Emily Lakdewalla from the Planetary Society has an excellent walkthrough of the image and explains why things appear the way they do in the image. It is well worth your time to have a watch (be sure to go full screen and HD so you can really spot the details):
Gravity did an amazing job of depicting the interior and flight characteristics of the Soyuz and its Chinese variant, the Shenzhou (albeit with some liberties taken in pursuit of the storyline). But it’s nothing like coming home in the real thing:
Go full screen and HD and be prepared for a wild ride!
On Nov. 18, NASA will send the Mars Atmosphere and Volatile EvolutioN (MAVEN) spacecraft on its way to the red planet to help us understand its atmosphere – or rather what happened to its atmosphere. My friend Rick Glasby will be covering the launch from Cape Canaveral on the 18th.
To get us ready for the launch, Rick put together a handy video to tell us what the mission is all about: