Yale astronomers have taken a new, close-up image of the interstellar comet 2l/Borisov. And to help us appreciate the size of the comet they’ve included our planet for comparison. Discovered by amateur astronomer Gennady Borisov in August this year, the comet will come closest to the sun on Dec. 8 at a distance of 186 million miles and then swing by Earth on Dec. 28 a few million miles closer.
The comet is the first discovered that originated from beyond our solar system, what astronomers call an interstellar comet. They suspect it was ejected during a close approach to a giant Jupiter-like planet in a star system elsewhere in our galaxy. No one can point to its parent sun, but this icy sibling grows a tail each and every time it passes another star, in this case our own sun. One can’t help wonder if this is the first time it’s “warmed its hands” by the fire since it departed its home solar system so long ago or one of many.
According to astronomer Pieter van Dokkum, the comet’s tail is nearly 100,000 miles long or 14 times the size of Earth.
“It’s humbling to realize how small Earth is next to this visitor from another solar system,” he said. The solid nucleus of the comet, composed of dust-impregnated ices, is about a mile (1.6 km) across. Although the tail is impressive when seen alongside Earth it’s made of fine dust sprinkled across a great swath of space. If you could somehow sweep it all into a tidy pile with a broom it would only be enough to fill a suitcase.
Borisov remains stuck around magnitude 15, too faint to see in most amateur telescopes but relatively easy to photograph with a quality DLSR through a telescope. I’m still hoping to see it in the next two weeks before it sinks too low in the morning sky. During closest approach to the Earth observers in the southern U.S. and points south are favored. But as of today I’ve yet to hear of a single person who’s seen it with their eye through a telescope. Comets can sometimes fragment and brighten, and that’s my hope for Borisov.
Turkeys in Space
As the turkey comes out of the oven on Thursday, the International Space Station (ISS) returns to the evening sky. It’s been buzzing around up there the past week and will continue to make bright passes through mid-December. Three astronauts, two women and one man, have been busy doing blood and cell research while we thaw out our birds and mash potatoes.
They’ll also be having a special meal for Thanksgiving. Besides the usual turkey and sweet potatoes the astronauts will be dining on pouches of macaroni and cheese, green beans and potatoes. There’s talk of jamming the space cornbread dressing (recipe here) into the bag holding the meat to create an impromptu version of a stuffed turkey. Crew members are also “coming up with some ideas of how we might create our own pumpkin pie, maybe with a little bit of cookies stuffed in the pouch of candied yams,” said Christina Koch.
Yes, you have to get creative in space, too if you want to keep things interesting. Back on the ground you can watch the speedy ship pass over your town during evening twilight. The ISS always “rises” somewhere in the western sky and travels east. A typical full pass takes 5 or 6 minutes but not always. At times they only last a minute. The ship moves up in the western sky only to fade and disappear. That happens when it’s eclipsed by Earth’s shadow.
We see the space station by the sunlight it reflects, and that sunlight lasts well into the night at the 250-mile altitude of the ISS. But eventually the ship passes into Earth’s shadow and literally fades away before our eyes, an exciting event to watch. Of course, it’s still up there moving along its orbital path, but now quenched by Earth’s shadow where the astronauts experience sunset and the onset of night.
Here are a few resources you can use to find out when to look and where to look for the station the next couple weeks. Good luck and clear skies!
Check out Heavens Above. Click the link, select your city and then tap the ISS link for a list of passes for the coming nights. Click on a date to see a map and timeline. Or go to NASA’s super-easy Spot the Station site for times. You can sign up there to get e-mail or text alerts whenever there’s a favorable pass over your city. You can also use an app like ISS Spotter for iPhone or ISS Detector for Android.