Category: Astronomy

Exploring the cosmos

Geomagnetic Activity and Airglow

Taking starscape photos last week I was surprised at the intense red glow appearing in the photographs. All across the southern sky were glowing areas of sky, here and there dark rifts cut through the glow. Set beside the Winter Milky Way it created beautiful photographs.

Airglow or auroral glow?
Airglow or auroral glow? An odd red glow in the photos during a strong geomagnetic storm.

The airglow was intense enough to be visually seen when I stepped away from the camera and let my eyes adapt to the darkness. Away from the Milky Way, in what should be dark sky, a faint red glow pervaded. I wondered what was going on, the normal airglow over Mauna Kea is quite faint and usually very green.

I was even further surprised when I later found out that a strong geomagnetic storm was in progress that night. Kp=6 conditions from back to back CME’s were creating strong aurora over Canada and the upper US.

Was I seeing some sort of auroral glow? In Hawaii? At 20°N latitude? This did not seem likely, but something unusual was occurring!

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A Night of Shooting in the Dark

The plan was to do some astrophotography Saturday night. The weather forecast forced a re-schedule, a winter storm arriving Saturday afternoon, Friday it was to be.

The Pleiades
The Pleiades, M45, with the Canon 6D and TV-76mm
The timing proved to be excellent, Mauna Kea providing glorious skies Friday night. Clouds hovered over the side of the mountain on arrival, but there was no worry. These were the sort of clouds that would vanish with the daylight. Anxious tourists wanting to see through the telescopes repeated the same question, will the clouds go away? I answered the questions with the relaxed assurance of experience of years on Mauna Kea, and continued to set up the gear. The clouds didn’t even last as long as I expected, dissipating as the sun settled into the horizon.

Setting up at the Mauna Kea VIS means a crowd of people. Hundreds of tourists that have come to enjoy a dark Mauna Kea Sky. I was joined by Raymond, a Hilo amateur also looking to take some photos. We setup side by side in a parking space just off the patio where the VIS was setting up their telescopes for the night. We would be in the center of the crowd for a while.

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Distant Asteroid Revealed to be a Complex Mini World

W. M. Keck Observatory press release…

After 8 years of observations scientists from the SETI Institute have found an exotic orbit for the largest Trojan asteroid, (624) Hektor—the only one known to possess a moon. The formation of this system made of a dual primary and a small moon is still a mystery, but they found the asteroid could be a captured Kuiper body product of the reshuffling of giant planets in our solar system. The results are being published today in Astrophysical Journal Letters.

624 Hektor NIRC2
Two adaptive optics observations made in July 2006 and October 2008 with the Keck II telescope. The center of each image shows the elongated shape of Hektor. The small, faint moon is shown in the cyan circle. Credit WMKO/Marchis
This study, based on W. M. Keck Observatory data and photometric observations from telescopes throughout the world, suggests that the asteroid and its moon are products of the collision of two icy asteroids. This work sheds light on the complex youth of our solar system, when the building blocks that formed the core of giant planets and their satellites were tossed around or captured during the giant planet migrations.

In 2006, a small team of astronomers led by Franck Marchis, astronomer at the Carl Sagan center of the SETI Institute, detected the presence of a small 12 km diameter moon around the large Trojan asteroid (624) Hektor. They used the 10 m Keck II telescope atop Mauna Kea, fitted with the NIRC-2 (the Near-Infrared Camera 2) instrument behind the adaptive optics and laser guide star system (LGS-AO).

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Water Vapor Detected in the Atmosphere of a Hot Jupiter

W. M. Keck Observatory press release…

California Institute of Technology (Caltech) astronomers using data gathered at the W. M. Keck Observatory have developed a new technique for planetary scientists that could provide insight into how many water planets like Earth exist within our universe. The results have been published on February 24th by The Astrophysical Journal Letters.

Exoplanet Water Spectra
Simulated data showing the method used for detecting water vapor features detected around the hot Jupiter tau Boo b.
Credit: Alexandra Lockwood (CalTech) background image used with permission from David Aguilar (CFA)
Scientists have detected water vapor on other planets in the past, but these detections could only take place under very specific circumstances, according to graduate student Alexandra Lockwood, the first author of the study. “When a planet transits, or passes in orbit, in front of its host star, we can use information from this event to detect water vapor and other atmospheric compounds. Alternatively, if the planet is sufficiently far away from its host star, we can also learn about a planet’s atmosphere by imaging it.”

However, a significant portion of the population of extrasolar planets does not fit either of these criteria and there wasn’t really a way to find information about the atmospheres of these planets. Looking to resolve this problem, Lockwood and her advisor Geoffrey Blake—Caltech professor of cosmochemistry, planetary sciences and chemistry—were inspired by the recent detection of carbon monoxide in the extrasolar planet, tau Boo b and they wondered if they could detect water in a similar manner.

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The Moon and Venus

Crescent Venus
Venus approaching inferior conjunction, 24Dec2013
Tomorrow morning, February 24th, will see a brilliant Venus paired with a crescent Moon. Look for the pair to rise about 04:00HST to be 33° above the horizon at sunrise. An 18% illuminated Moon will be a nice match for Venus shining brilliantly at -4.6 magnitude. Separation will be about 7&deg.

The following morning, February 25th, will see the Moon 7° below Venus. Observant sky-watchers will note Mercury another 16° closer to the eastern horizon and the rising Sun.

Postcard from the Universe – The Rosette

A result from Saturday night. About an hour of integration all told… Good color, very nice stars, good detail. While encouraging, I really need more time on this one, there is too much noise in the fainter regions of the nebula. I can get more data and add it to the stack to continue to improve the result. From up on the mountain I should be able to use longer exposures with darker skies. Colder conditions will reduce the dark current in the camera, also aiding in longer exposures.

Rosette Subframe
A single unprocessed subframe of the Rosette Nebula, Canon 6D and TV-76mm, 240s @ ISO6400
Compare the processed shot with the single subframe I published yesterday. The final shot is a stack of 10 x 4min, 10 x 1min, and 10 x 15s frames, 30 frames for just under an hour of exposure. Also needed is another 10 x 240s dark frames and 10 flat field frames to use for calibration. This takes another hour, but was done after the telescope was rolled back into the garage and I went to bed.

The Rosette Nebula is a large star forming region just east of Orion in the constellation of Monocerus. It is quite large, the main body seen in the photograph is well over a degree across. The dark region in the center is about the size of the Full Moon

The Rosette Nebula
The Rosette Nebula, NGC2237, NGC2238, NGC2244, NGC2246, Canon 6D and TV-76mm, 10x240s+10x60s+10x15s @ISO6400

Shooting from the Driveway

A good night in the driveway last night.

Rosette Subframe
A single unprocessed subframe of the Rosette Nebula, Canon 6D and TV-76mm, 240s @ ISO6400
After solving the little equipment issues, waiting out weeks of bad weather and waiting for the Moon to go away, I finally had a nice photographic night. Setting up at sunset I shot until the Moon rose. Most of the targets I have shot before, Orion, Rosette, Markarian’s Chain. I also shot Melotte 111, an object that has always intrigued me. The full frame camera and the TV-76 has a wide enough field to capture this very large and nearby star cluster.

I want to use this combination camera and telescope with a very wide field to work over the dark nebulae of the Summer Milky Way. With 384mm focal length the full frame camera gives me over 5.35° x 3.56° field of view. The beehive also lent itself to the wide field, another large object that was worth a stop to shoot.

Aside from one little equipment issue to start, more an operator education issue, the gear worked great. Note to self… Must turn off camera WiFi before the camera will link to the computer via USB. I am currently using APT to control the camera, a very impressive bit of software. The auto-guider worked perfectly, frame after frame nearly identical. I can slideshow through dozens of sub-frames and not see any difference, no drift!

A single sub-frame of the Rosette Nebula is shown to the right. The Rosette is an emission nebula with most of the light emitted at the wavelength of Hα 656.28 nm. My Canon 6D is stock, no astrophoto modifications. Despite an IR cutoff filter that blocks much of the Hα light the camera captures a fair amount of the nebula. Perhaps I should get a 48mm Hα filter for the camera to shoot from the driveway.

With everything working so well I really need to haul the rig up to Hale Pohaku for a night of imaging under darker skies than I get down at 1000ft. Next weekend is dark-of-the-Moon weekend. Need to plan an outing?

It will take a bit to process the results of the night. As usual, keep an eye here on Darker View for the finished photos.