Comet Hyakutake
What is Comet Hyakutake?
Comets· Nucleus ~4 km. The great comet of spring 1996, which came within about 15 million km of Earth and stretched a long tail across the night sky. It was also the first comet found to give off X-rays.
Past visits and the next return
Orbit and period
| Nucleus | ~4 km |
|---|---|
| Closest to Earth | 1996-03-25, 0.10 AU |
| Period | ~70,000 yr |
| Record | tail 570 million km — longest measured |
Figures are representative approximations. Source: compiled from NASA and IAU public data.
The surprise X-rays from Comet Hyakutake
In March 1996 the German X-ray satellite ROSAT turned toward Comet Hyakutake. Scientists did not expect much. X-rays usually come from extremely hot places, and a comet is a cold lump of ice and dust. Yet a bright, crescent-shaped glow of X-rays appeared on the comet's sunward side. It was the first time X-rays had been detected from a comet.
The puzzle was solved the following year. Electrically charged particles stream constantly from the Sun like a wind. When they meet gas released by a comet, they steal electrons from it. As each captured electron settles into place, it releases energy in the form of X-rays. This process is called charge exchange. X-rays have since been found coming from many other bright comets.
The comet in depth
Comet Hyakutake was discovered on 30 January 1996 by Yuji Hyakutake, a Japanese amateur astronomer using large binoculars. Only two months later, on 25 March, it passed 0.10 AU from Earth, about 15 million km or roughly 39 times the distance to the Moon. That makes it one of the closest comet approaches of the past two centuries.
Its nucleus was small, only about 4 km across, but it came so close that it looked very bright, and at its best its tail stretched across a large part of the sky. Later analysis showed that the Ulysses spacecraft had passed through material from the tail about 570 million km from the nucleus. That is the longest comet tail ever measured.
Passing close to the Sun, Hyakutake had its orbit changed by the planets' gravity, so its next return is calculated to be about 70,000 years away. In the orbit view you can watch it dive toward the Sun and swing far back out. In the Sky view, go to the night of 26 March 1996 (13:00 UTC) to see where it passed near Polaris.
Frequently asked
- How close does Comet Hyakutake get to the Sun?
- The closest to earth of Comet Hyakutake is 1996-03-25, 0.10 AU.
- How long is the orbital period of Comet Hyakutake?
- The period of Comet Hyakutake is ~70,000 yr.
- In one line, what is Comet Hyakutake?
- Comets — The great comet of spring 1996, which came within about 15 million km of Earth and stretched a long tail across the night sky.
Related
Figures are representative approximations. Simulated positions use J2000 mean elements.