Comet ISON has traveled for at least a million years, pulled by the gravity of the sun that binds it, and us, in orbit. Now ISON’s moment of truth is here – its closest point to the sun, or perihelion – today, November 28, 2013 at around 18:44 UTC/ 1:44 p.m. EST. The comet is difficult, probably impossible, to view from Earth right now; it is temporarily lost in the sun’s blinding glare. How can you see Comet ISON as it sweeps closest to the sun that binds it in orbit … and may destroy it? The best bet for the few hours around perihelion may be NASA’s SDO page. Experts will be answering questions live from Twitter; use the hashtags #ISON and #askNASA. But there are many other possibilities! Follow the links below to learn how you can experience ISON’s encounter with the sun today, online.
Do NOT do this to experience ISON closest to the sun. We’ve seen several images already on EarthSky’s Facebook page posted by people who aimed their cameras at the sun, thinking they could snap a shot of Comet ISON. Do NOT do this. Never look at the sun in any way, searching for Comet ISON. Especially don’t look near the sun with binoculars, cameras or any other optical aid. You know that staring at the sun directly can burn the retina of your eye, without causing any pain. It can damage your eyes, permanently. Also, remember, ISON is tiny in contrast to its parent star. If you’re on Earth, you will not catch it when closest to the sun on November 28. Those posts on our Facebook page? Not Comet ISON.
If I can’t see ISON closest to the sun on November 28, who can see it? We’ll see Comet ISON with our spacecraft: the robot extensions of our eyes. ESA and NASA have a fleet of spacecraft poised to observe the comet. Most observations have already begun. Keep reading, and you’ll find links to spacecraft observations of the comet, which you can access online. Here are the dates of the planned NASA spacecraft observations.
Nov 21-28: STEREO-A Heliospheric Imager
Nov 26-29: STEREO-B coronagraphs
Nov 27-30: SOHO coronagraphs
Nov 28-29: STEREO-A coronagraphs
Nov 28: SDO
Nov 28: Hinode
Google hangout with experts at 18:00 – 20:30 UTC (1:00 – 3:30 p.m. EST) on November 28. NASA is holding a live video Hangout on G+ during ISON’s perihelion passage. You can watch Comet ISON’s perihelion live, with the Slate’s Bad Astronomer Phil Plait, plus astronomers C. Alex Young, W. Dean Pesnell and Karl Battams (aka @SungrazerComets on Twitter and a blogger at NASA’s Comet ISON Observing Campaign website, who, in my opinion, has done more to keep us updated on Comet ISON than anyone on Earth!). There will be live feed from NASA’s SOHO Sun-observing satellite (that should be spectacular) and from the Kitt Peak Observatory solar telescope. The event is from 18:00 – 20:30 UTC (1:00 – 3:30 p.m. EST).
Watching Comet ISON with the SDO spacecraft, at perihelion NASA’s Solar Dynamics Observatory, or SDO, will view the comet for a few hours during its closest approach to the sun. SDO’s real-time images can let you see the comet at closest approach and may be your best bet for watching the comet online. Look for SDO views of Comet ISON here.
One exciting possibility, NASA says, is that we might see extreme-ultraviolet emission from the comet when it’s closest to the sun.
In SDO’s view, the comet will appear to travel above the sun, and the SDO instruments will point away from the center of the sun to get a better view for three hours on November 28.
How can I see Comet ISON with the STEREO spacecraft? NASA’s Solar TErrestrial RElations Observatory, or STEREO, is already viewing Comet ISON this week. There are two nearly identical STEREO spacecraft, which were launched in 2006. For Comet ISON, watch for images from SECCHI, which is a suite of remote sensing instruments consisting of two white-light coronagraphs (images that block the brighter view of the sun itself, in order to see details in the sun’s atmosphere or, in this case, a comet).
This spacecraft and its instruments have provided some awesome images of sungrazing comets, such as those of Comet Lovejoy in 2011.
At ISON’s pass near the sun, STEREO-B will be the only one of all the observing spacecraft that will see the comet transit across the face of the sun. Otherwise, the coronagraphs will show the comet.
There’s always a delay in the availability of the full resolution data from STEREO. But, NASA says, the lower-resolution “beacon” data should be available in real-time, depending on the availability of the volunteer ground stations that help bring in these data. Places to look for STEREO views of Comet ISON include:
How can I see Comet ISON with the SOHO spacecraft? The SOlar and Heliospheric Observatory (SOHO) is a joint European Space Agency/NASA. It was launched in 1995 to study the sun. SOHO is no stranger to comets; it has discovered over 2,400 of them.
Like STEREO, SOHO will provide coronagraphs, images that block the bright sun to focus in on fainter objects. See the image above for ISON’s anticipated track through SOHO’s field-of-view. Places to look for SOHO views of Comet ISON include:
How can I see Comet ISON with the Hinode spacecraft? The X-Ray Telescope on the JAXA/NASA Hinode mission will also be looking at Comet ISON for about 55 minutes during perihelion. I didn’t see a place to look for real-time images, so watch for Hinode images in the days following the comet’s November 28 perihelion. NASA’s Hinode page is here.
What will happen to ISON when it’s closest to the sun? There are several possibilities. ISON is a fresh comet, a first-time visitor to the inner solar system. It’s a fragile ice-ball that has never known the sun’s gravity up close, or the sun’s intense heat. Tidal forces from the sun may break the comet to pieces. Or, the sun’s heat may boil away so much of ISON’s ice that the comet will literally fall to pieces. Or, the nucleus, or core, of Comet ISON may emerge intact.
If ISON does remain intact, it may become a bright comet in our sky! In that case, the best time to look for it will be before dawn in early December. You’ll be looking east, in the general direction of the sunrise. Will it be visible? No one can answer that question yet.
Just don’t wait for Comet ISON to become visible in the evening. That’ll happen in the second half of December. It’ll be much fainter in late December than early in the month.
What then for Comet ISON? Although its inbound journey in our solar system will have ended, ISON will still be journeying onward. It’ll be moving away from the sun, on a path that will carry it, ultimately, out of our solar system. In other words, unlike some comets that become trapped in the inner part of the solar system, so that we see them again and again, we’ll never see Comet ISON again after its 2013 trek into the inner solar system.
Here’s the good news for us stargazers, who struggle with all sorts of inclement weather: no clouds or rain will ruin the view of any of these space-based observations. They all should go as planned.
Comet ISON has traveled more than a light-year from the Oort Cloud. Its travel-time is at least a million years, perhaps much more than that. Bookmark this post, and as ISON sweeps only 730,000 miles (1.2 million km) above the sun’s surface on November 28, check out some of these links!
Bottom line: Many different NASA and ESA spacecraft will be observing Comet ISON this week, and especially on November 28 – Thanksgiving Day in the U.S. – as ISON makes its closest sweep past the sun. This post contains links to a host of real-time images, expected from the various craft. If I had to choose one, the SDO page looks the most organized for the event, but bear in mind SDO will only be broadcasting results for a few hours around perihelion on November 28, while others have been posting images of ISON near the sun all week. My second choice might be SECCHI’s page, whose team says it will try to provide images quickly. Personally … I’ll be checking all the links, periodically, as this week progresses.