Comet Elenin on August 3 (left) when near maximum brightness and after breakup when last seen on September 14 (right). Credit: Michael Mattiazzo
This is the week many have looked forward to since shortly after the discovery of C/2010 X1 Elenin last December. Original predictions made last winter based on a relatively close approach to Earth on October 16 indicated the comet might have been as bright as 4th magnitude and visible with the naked eye from outer ring suburbs and rural areas.
Much has changed since then. Comet Elenin was slow to brighten during spring and early summer. Even through my 15-inch reflecting telescope it never amounted to more than a faint 13th magnitude patch of hazy light. By mid-August things looked better when the comet became visible to southern hemisphere sky watchers in binoculars at around magnitude 8. Revised predictions then downgraded its brightness at closest approach to Earth from 4th to 6th magnitude. While very faint to the naked eye, that still easily placed Elenin within binocular range.
So far so good. Then around August 20th the comet busted apart under the intense solar heat experienced en route to perihelion or closest approach to the sun. Comet Elenin’s lost its intense inner glow and suddenly began to fade. It was last seen about September 14 as a diffuse glow fainter than 10th magnitude. Sad news for comet observers.
Use the two stars at the end of the Big Dipper's bucket to point you to the bright star Regulus in Leo the Lion. Using the detailed chart below, you can navigate to Comet Elenin's location. This map shows the sky around 90 minutes before sunrise facing east. Created with Stellarium
Still we hoped the comet might keep its act together long enough to show up in the SOHO coronagraph images late last month. Maybe a brightly glowing cloud of dust? Nothing was seen. Now we’re finally down to the last straw. Will the comet be visible through telescopes when it returns this week in a dark sky before dawn?
I’ve drawn up a couple charts to help you search for it. The wider one includes the Big Dipper to point you to Leo and its bright star Regulus. From there you can use binoculars and telescopes to navigate to Comet Elenin. And don’t forget our consolation prize - Comet Honda-Mrkos-Pajdusakova! It’s still around 7th magnitude and faintly visible in binoculars, while a telescope will show its skinny tail and bright, pale blue-green coma.
In this detailed map, the star Regulus is at top right. The comets' positions are shown for each day beginning October 4. Stars are plotted to 8th magnitude. Comet Elenin quickly moves up day by day from the eastern horizon, while Comet Honda slowly drops toward the horizon. The time shown is 90 minutes before sunrise. Created with Chris Marriott's SkyMap software.
Both comets are very low in the eastern sky at the start of dawn or about 1 1/2 hours before sunrise for northern latitudes. Elenin starts off tomorrow morning at just 4 degrees high while Comet Honda does better at 11 degrees or about one fist above the eastern horizon. Notice though how quickly Comet Elenin shoots up from the horizon. By the 9th and 10th, it will lie straight across from Regulus and 25 degrees high – perfect conditions for seeking from places where trees block the horizon. The higher up objects are, the less air their light must travel through and therefore the less light absorbed. That means that as the comet vaults higher in the sky, its faint remains will be easier to see. That’s assuming there’s anything left that amateur-sized telescopes can pick up. Comet Elenin was last seen at around 10th magnitude – visible in 6-inch and larger telescopes – but may be much fainter now.
After the 10th, a bright moon (full on the 11th) will make it impossible to see any faint comets in the morning sky for a period of about 10 days. You’ll need to get cracking in the next week if you have a telescope, clear skies and any hope of seeing the comet. I’m one of those guys with a lot of hope when it comes to astronomy, so I’ll be out later this week squinting through the eyepiece and report back on what if anything is out there.
Author:astrobob Read Full Article