Home / News / Astronomy news /

Hubble Captures Outburst from Comet Targeted By Deep Impact

In a dress rehearsal for the rendezvous between NASA's Deep Impact spacecraft and comet 9P/Tempel 1, the Hubble Space Telescope captured dramatic images of a new jet of dust streaming from the icy comet.

Posted by Tormod
27 June, 2005 06:06:45

print article
A | A | A

The images are a reminder that Tempel 1's icy nucleus, roughly the size of central Paris, is dynamic and volatile. Astronomers hope the eruption of dust seen in these observations is a preview of the fireworks that may come 4 July, when a probe from the Deep Impact spacecraft will slam into the comet, possibly blasting off material and giving rise to a similar dust plume.

These observations demonstrate that Hubble's sharp "eye" can see exquisite details of the comet's temperamental activities. The Earth-orbiting observatory was 120 million kilometres away from the comet when these images were taken by the Advanced Camera for Surveys' High Resolution Camera. The telescope's views complement close-up images being taken by cameras aboard Deep Impact, which is speeding toward the comet.

The two images, taken seven hours apart on 14 June, show Tempel 1 and its new jet.

The image at left, taken at 7:17 a.m. (UT), is a view of the comet before the outburst. The bright dot is light reflecting from the comet's nucleus, which appears star-like in these images because it is too small even for Hubble to resolve. The nucleus, a potato-shaped object, is 7 kilometres across and 2 kilometres long. Hubble's viewing the nucleus is as difficult as someone trying to spot a potato in Stockholm from Madrid.

The photo at right, snapped at 14:15 a.m. (UT), reveals the jet [the bright fan-shaped area]. The jet extends about 2,200 kilometers, which is roughly the distance from Copenhagen to Athens. It is pointing in the direction of the Sun. Comets frequently show outbursts in activity, but astronomers still don't know exactly why they occur. Tempel 1 has been moving closer to the Sun, and perhaps the increasing heat opened up a crack in the comet's dark, crusty surface. Dust and gas trapped beneath the surface could then spew out of the crack, forming a jet. Or, perhaps a portion of the crust itself was lifted off the nucleus by the pressure of heated gases beneath the surface. This porous crust might then crumble into small dust particles shortly after leaving the nucleus, producing a fan-shaped coma on the sunward side. Whatever the cause, the new feature may not last for long.

Astronomers hope that the July 4 collision will unleash more primordial material trapped inside the comet, which formed billions of years ago. Comets are thought to be 'dirty snowballs', porous agglomerates of ice and rock that dwell in the frigid outer boundaries of our solar system. Periodically, they make their journey into the inner solar system as they loop around the Sun.

The contrast in these images has been enhanced to highlight the brightness of the new jet.

In Europe, the European Southern Observatory will conduct a massive ground-based observing campaign before and in the week after the impact.

Source: NASA

Comments (10 posted):

starrmtn001 on 27 June, 2005 08:45:40

What if the "plan" backfires? :eek:

C1ay on 27 June, 2005 09:08:16

What if the "plan" backfires? :eek: Backfires? How?

starrmtn001 on 28 June, 2005 12:48:44

C1ay on 28 June, 2005 01:42:16

What are the chances (if any) of impact shatter? What are the chances (if any) of fragments reaching our orbit (in due time)? I presume small fragment would do little damage on Earth. But what about orbiting hardware i.e. satellites, spacestations, high altitude aircraft, etc.? Since the impact will be head on and tangent to the comet's orbit there will not be any significant deflective energy that would alter the orbit of those pieces.

starrmtn001 on 28 June, 2005 05:00:34

Good to know. Thank you.

Tormod on 28 June, 2005 05:26:36

Anyway, comet Tempel-1's orbit is outside Mars. And the speed and size of the comet compared to the impactor is like a boeing 767 slamming into a mosquito...

starrmtn001 on 28 June, 2005 06:27:13

Yuck. Got Windex?

nkt on 28 June, 2005 10:45:00

Anyway, comet Tempel-1's orbit is outside Mars. And the speed and size of the comet compared to the impactor is like a boeing 767 slamming into a mosquito... Though if the out-gassing seen here is indicative of a very soft core, we could be looking at a seven storey+ deep crater! That's a pretty tough mozzie!

Tormod on 28 June, 2005 01:26:38

Though if the out-gassing seen here is indicative of a very soft core, we could be looking at a seven storey+ deep crater! That's a pretty tough mozzie! I know. We're going to watch it live at the Norwegian Space Centre on the morning of July 4... :)

UncleAl on 28 June, 2005 09:53:19

UPDATE! The impactor masses 370 kg and will hit with a relative velocity of 10.2 km/sec for an impact energy of 19 gigajoules, equivalent to 4.8 tons of TNT. Compression phase on impact is roughly diameter/speed or 100 microsconds. Excavation phase thereafter is roughly sqrt(diameter)/local gee or 300 seconds. 500 lbs of copper coming into comet Tempel-1 at 25,000 ft/sec. After it passes through it's own mass or a little more it flashes into plasma. The plasma then expands, explodes, and deposits most of the energy all at once. Three scenarios: 1) Dirty snowball. Mostly frozen gases with lots of pebbles and dust. Low density overall. Deep penetration then boom. Crater 10 stories deep and wide as a football field; big debris plume to photograph from all the high pressure gas generated. NASA gets fat publicity. Gravity-dominated result. 2) Icy dirtball. Mostly pebbles and dust cemented by some frozen gases. High density overall. Shallow penetration then boom. Rock is a crappy vaporizer. NASA creates a small astro-fart. A Commission is appointed to investigate. Strength-dominated result. 3) Unconsolidated. The comet is a foam of frozen gas and dirt and pebbles with lots of void spaces. Now the impactor goes real deep, like an ice pick thrust into styrofoam - so deep there is no weak exit when the plasma explodes. The whole thing blows and fragments into a shotgun blast of debris. Compression-dominated result. 4) NASA can't hit a lump the size of Manhattan. Number (3) is my favorite. With any luck the slightly expanding cloud will soak in sunlight and vaporizing gases will randomly thrust the solids into a purely huge rapidly expanding cloud. We then enjoy the sight of Not A Space Agency furiously tap dancing before the Media.