SOHO : Solar & Heliospheric Observatory

The objectives :

The objective of the mission is to

study the structure and dynamics

of the solar interior, corona and

solar wind

The Launch :

Launched on 2nd December 1995

with a nominal lifetime of two

years, however was extended

several times

The project :

It is an international collaboration

between NASA and ESA

Instruments aboard :

SOHO harbors 12 complimentary

instruments

SOHO : the LASCOs

LLarge AAngle and SSpectrometric COCOronograph (LASCO)

It blocks direct light from the surface of the Sun with the help of an

occulter, creating an artificial eclipse. It observes the outer solar

atmosphere from near the limb to a distance of about 21 million km.

C2 image� More magnification

� Small FOV (6 Rs)

� Fainter comets

C3 image� Less magnification

� Large FOV (30 Rs)

� More area to check

SOHO and Comets

Comet with perihelion of

a few solar radius can be

seen in SOHO images.

Brightest comets

detected by ground-

based telescopes can

be seen by SOHO

For example, this is

Comet NEAT (discovered

under Near Earth

Asteroids Tracking

project) appeared in

February 2003 as seen in

‘C3’ telescope on SOHO

SOHO and Comets

But…such comets are

discovered much before they

are detected by SOHO

SOHO : its prolific comet hunting…

So what kind of comets are

found by SOHO?

The SunThe Sun--grazing cometsgrazing comets

Typically small comets

only seen when they

come close to the Sun

Such comets ‘graze’

within a few solar radii of

the Sun

Most of them belong to

the ‘family’ that is

fragmented from a

single ‘parent’ comet

SOHO : its prolific comet hunting…

Byproduct of SOHO mission

Although SOHO’s main

objective is to study the

Solar dynamics, SOHO

witnessed amazing world

of sungrazing comets.

Solar region, which

previously thought to be

very calm and devoid of

any activities, turned out

to be an eventful world…

With the discovery of

2500+ comets, SOHO

became history’s most

prolific comet hunter

SOHO : its prolific comet hunting…

How Sun-grazing comets are

discovered with the help of SOHO?

SOHO comet hunting pre-requisites…

What are the pre-requisites of SOHO

comet hunting ?

a fast computer with lots of RAM

large monitor

a good image viewing software

….and most importantly…

a fast internet connection

SOHO : its prolific comet hunting…

lots of patience….!

Select the

instrument C2 or C3

Select the resolution

of the image

Select the date

Number of images

Step 1 : Getting images

Amateur Astronomy Workshop 2010, Akashmitra, KalyanAmateur Astronomy Workshop 2010, Akashmitra, Kalyan

Step 2 : Loading and running images

Images accessed are to be loaded and run in a software

There are many things

visible in each image

How to find a

suspicious object in

the myriad of other

objects?

How to confirm that it

is a genuine sun-

grazing comet?

Amateur Astronomy Workshop 2010, Akashmitra, Kalyan

Holding arm of the

Occulting disc

Occulting disc

The Sun (Behind)

Date and Time of

the image

Step 3 : Looking for comets…

Then, where to look for comets amid hundreds of stars,

debris, streaks, etc.?

Remember that, most sun grazing comets have identical

orbits, called ‘family’ of comets, so their paths are fairly

predictable. Almost 85% of LASCO comets are from a

known group called ‘Kreutz’ group.

For example, paths of various groups comet for January

are as follows:

Looking for any suspicious

object moving towards the

sun…

After ruling out it for…

� Noise

� Image defect

� Planet

� Cosmic rays

� Any other invalid

candidate

�COMET

Step 4 : Focus on Kreutz group and their path…

Step 5: Measuring the position of the object

If you still feel that you have got a good suspect, then your software might come to help you

Remember that the suspicious

object has to be visible in

minimum three consecutive

images (for C3 image) or two

consecutive images for (C2

images) to register a valid claim

Once the suspect passes this test,

its pixel position is to be measured

as accurately as possible

this can be done by zooming in

the image and clicking perfectly

on the object. Softwares like

‘Aladin, Irfan view, ImageJ’ will do

the rest for you.

( X Coordinate )(

Y C

oo

rdin

ate

)

Step 6 : Putting up your claim

Go to Reports page now and prepare to put up your claim at:

http://sungrazer.nrl.navy.mil/index.php?p=cometform

Select ‘new user’ (if it is your

first claim)

Date of the image (mentioned at

Lower left on each image

Select C2 or C3 and image resolution

(512X512 or 1024X1024)

Select the ‘origin’ of measurement (upper

or lower left,etc)

Select the family of the comet

Enter image time (mentioned at the lower

left corner of each image) and the X, Y

coordinates of the object

Submit your claim and just keep….

Although experienced comet hunters may confirm your report unofficially, officialconfirmatory report by SOHO announcing discoveries comes much later, as follows:

Discovery confirmation report

Post discovery feel…

Well, you have just successfully discovered a sun-

grazing comet ! However…

Instead, it will be given unofficial name, such as

SOHO-1695, later on after confirmation from Central

Bureau of Astronomical Telegrams (CBAT), an official

name will be given to the comet as C/2010 H5 (SOHO),

that’s it !

Your name will NOT be given to the said comet

No matter, you will be given credit of the discovery,

Well ! That’s not a bad bargain !

Get, set, go….

SOHO’s official Comet Hunting Guide:

http://sungrazer.nrl.navy.mil/index.php?p=guide

SOHO Real-time images

a) Jpeg Images

http://sohodata.nascom.nasa.gov/cgi-bin/data_query

b) Gif images

http://lasco-www.nrl.navy.mil/javagif/gifs/

c) Fits images

ftp://lasco6.nascom.nasa.gov/pub/lasco/lastimage/level_05

SOHO Recent Reports page

http://sungrazer.nrl.navy.mil/index.php?p=recent

SOHO Comet reporting form

http://sungrazer.nrl.navy.mil/index.php?p=cometform

Tracks of SOHO-observed comet groups in C2 and C3

http://sungrazer.nrl.navy.mil/index.php?p=comet_tracks

SOHO Comet Hunting FAQs

http://sungrazer.nrl.navy.mil/index.php?p=FAQs

SOHO 14-day Deep Space Network schedule (To know when real-time images will come?)

http://sohowww.nascom.nasa.gov/operations/schedule/schedule.html

Shishir is available at : shishir.supernova@gmail.com ☺☺☺☺