View Full Version : Discussion: Soho Has Seen 750 Comets

2004-Apr-06, 08:02 PM
SUMMARY: On March 22, 2004, the ESA/NASA SOHO solar observatory spacecraft observed its 750th comet since its launch in late 1995. SOHO has a special instrument that blocks out the glare of the Sun, and allows it to see comets that graze the Sun. Amateur astronomers from around the world analyze the photographs taken by SOHO, which are published on the Internet - more than 75% of the discoveries have been made by amateurs. This one was discovered by Sebastian Hönig from Germany.

What do you think about this story? Post your comments below.

2004-Apr-06, 09:43 PM
This is an interesting story, Fraser. :D

Trajectories of comets may contain information on the birth of the solar system. :rolleyes:

Has anyone back-calculated from the number presently observed, and the probability of capture by the Sun or another planet, to estimate the number of these objects 4-5 billion years ago?

With kind regards,

Oliver :D

PS - The origin and composition of the Sun may be related to the trajectories established for comets at the birth of the solar system. See the ongoing discussion at:

2004-Apr-07, 08:12 AM
I've got a question,

in the gif movie which you can find here (http://home.tiscali.nl/sfictie/data/astronomy/images/anim.gif) (603Kb) on October 24, 2003 (01:00 am) you can see towards the top of the sun an impact like feature which dissapates within 24 hours.

Is this an actual impact or is this caused by something else?

2004-Apr-07, 07:02 PM
Thas a lot of comets to find in such little time i have a question can this equitment be soled to amature astronomers like me so i can find comets. B)

2004-Apr-07, 08:28 PM
cool i think this is interesting ;)

2004-Apr-08, 01:00 AM
Surely that couldn't be an impact feature isferno,i mean the comet would frizzle up in the sun's corona, wouldn't it? perhaps it is the shockwave? or maybe totally unrelated?

Am i missing something?

2004-Apr-08, 04:58 AM
I wouldn't know Damienpaul, but its shape isn't the tipical outgassing of a upraising gasbubble as you can see in the overall picture.

It also does produces a shockwave feature as seen with the new eruption north of the equator a couple of days later, though smaller (only 1 frame I believe)

The first thing it did remind me of was of a demonstration during science class where the teacher demonstrates what happens if a charged particle enters a petridish filled with condens.
But that would be definitely not be it. (unless a very very large charged particle)

2004-Apr-11, 09:36 AM
I've forwarded the question to "Dr Soho"

I'm very curius as to what it might be. I'll post their answer here.

2004-Apr-19, 08:27 PM
I got the following reply back on my question if the feature as I described could have been an asteroid. (As the feature looked like a splash with a crown and a trail)
The first set of values (especially density) were the ones I provided as possible values, (of which I assumed were correct for the stratosphere of the Sun.)

With the numbers you gave me, 8 km diameter, 10 kg/m3 density, 72 km/s velocity,
I calculate an energy of 7e21 joules. Your assumed density is extremely low; if
I put in a more realistic density of 1000 kg/m3, that makes it 7e23 joules.
I'll use this larger number in the rest of the analysis.

The pixels in your image are about 8000 kilometers on a side. Each pixel
radiates about 3.7e21 joules every second. The reddish area I think you're
referring to covers something on the order of 100 pixels, so we're talking about
3.7e23 joules/second as the normal energy output from this region. Over the
four hours between successive frames, the total energy output would be 5.3e27
joules, which is 7600 times more than the energy presumed to be deposited by an
asteroid. In other words, the energy deposited by even a fairly large asteroid
is miniscule compared to the energy that the Sun is putting out all the time.

There's no need to invoke asteroids to explain energy release in the corona,
such as the one you point out. Energy is being released in the corona all the
time, due to reconnection events in the magnetic field. The event that you
point out is just one example.

William Thompson
NASA Goddard Space Flight Center

Thank you for replying Mr. Thompson.