SOHO : Solar & Heliospheric Observatory · SOHO : Solar & Heliospheric Observatory The objectives :...
Transcript of SOHO : Solar & Heliospheric Observatory · SOHO : Solar & Heliospheric Observatory The objectives :...
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 : [email protected] ☺☺☺☺