January 31 – Cold as Ice

Today’s Factismal: Using a pair of birding binoculars, Yuji Hyakutake discovered his second comet in 1996.

One of the best ways to become famous in astronomy is to discover your very own comet. Not only is the comet named after you, but you stand a very good chance of discovering something that will light up the night skies for all to see. And though it may seem surprising to some, most people who discover comets are not professional astronomers. Instead, they are people who just happen to want to find comets.

Yuji Hyakutake is a good example of the breed. Using a pair of birding binoculars, he would go out at night and scan the skies looking for the faint blob that foretells of an incoming comet. Binoculars are preferred by comet hunters because they gather a lot of light, which helps you see faint things, and because they give enough magnification, so you can see things like the moons of Jupiter, and because they are inexpensive (about $50). He’d been looking for a comet for some time without much luck when he saw a dim fuzzy patch in December of 1995. He reported it to the observatory and was elated to find that it was a comet – his first discovery! Bad weather set in and kept him from looking at the stars for a couple of weeks. When he did go back outside, he looked around and found another, even better comet. It was his second comet that came to be known as Comet Hyakutake.

Comet Hyakutake (Image courtesy ???)

Comet Hyakutake (Image courtesy Jerry Lodrigruss)

As astronomers started to observe Yuji’s comet, they became more and more excited. The comet had obviously come into the inner solar system before, which was good because that meant that it would provide a better and more consistent display. And the comet would pass close to Earth. Very close to Earth. It turned out that this would be the closest approach by a comet in nearly a century. Taken together, that meant that the comet would be very bright; only the full Moon and Jupiter would shine more brightly in the night. And, best of all, it would be moving so quickly relative to Earth that people could actually see it move across the sky at night.

Another view of Comet Hyakutake (Image courtesy Shigemi Numazawa)

Another view of Comet Hyakutake (Image courtesy Shigemi Numazawa)

Comet Hyatuke turned out to be everything that was promised and more. It had a distinct green color from the carbon locked in its ice. It had a head that appeared four times as large as the Moon, and a tail that stretched out three times as far as the head. About the only disappointment with the comet was that it was moving so quickly that it was visible in the night sky for only a few months. Soon it went in beyond the orbit of Venus and was lost to the naked eye.

Comet Hyakutake passes the Sun (Image from SoHo)

Comet Hyakutake passes the Sun (Image from SoHo)

But not to the Solar and Heliospheric Observatory Satellite, or SoHo for short. This satellite, which was launched in 1995, was intended to observe the Sun and tell us more about how solar flares and coronal mass ejections affect life on Earth. But what NASA hadn’t expected when they launched SoHo was that they would see comets. But it turned out that SoHo saw a lot of comets that came to be called “Sun-grazers” for their death-defying feat of diving in near the Sun before heading back out into the dark depths of the outer Solar System. And, as fate would have it, Comet Hyatuke was a Sun-grazer. It came to within .2 AU of the Sun before it started to move back out.

SoHo is still in orbit today, looking at the Sun and looking for comets. If you’d like to join the folks that have found more than 2,400 comets using SoHo images, then head on over to Sungrazing Comets:
http://sungrazer.nrl.navy.mil/index.php?p=guide

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