Fermi’s Spriagraph

Fermi's Motion Produces a Study in SpirographThe Fermi Gamma-ray Space Telescope orbits the Earth every 95 minutes, it’s scans building up increasingly more complex views of the universe with every circuit. The image above was put together from eight frames from a movie showing over 4 years’ position and exposure data recorded by Fermi‘s Large Area Telescope (LAT) into a single snapshot. The pattern reflects the various motions of the spacecraft, including its orbit around Earth, the precession of its orbital plane, and the manner in which the LAT nods north and south on alternate orbits.

The LAT sweeps across the entire sky every three hours, capturing the highest-energy form of light—gamma rays—from sources across the universe. Those sources range from supermassive black holes billions of light-years away to objects in our own galaxy, such as X-ray binaries, supernova remnants, and pulsars.

Image Credit: NASA/DoE

Andromeda’s Bright X-Ray Source

The Andromeda galaxy is our nearest neighboring large galaxy. It has a mysterious dominant source of high-energy X-ray emission called Swift J0042.6+4112. Recent observations by the NuSTAR (Nuclear Spectroscopic Telescope Array) mission have pinpointed a pulsar that is for this high-energy radiation. A pulsar is the dense remnant of a dead star that is highly magnetized and spinning. The strong pulsar in Andromeda is likely in a binary system in which material from a stellar companion gets pulled onto the pulsar. X-rays are radiated by the material as it heats up.

The highest energy x-rays are color code blue in the NuSTAR image above, and the pulsar is shown as a blue dot. It appears brighter in high-energy X-rays than anything else in the galaxy.

Image Credit: NASA

A Deep View in X-Rays

chandra-deep-field-southMade with over 7 million seconds (about 11-1/2 weeks) of Chandra X-Ray Observatory observing time, this image is part of the Chandra Deep Field-South and is the deepest X-ray image ever obtained. This look at the early Universe in X-rays gives astronomers the best look yet at the growth of black holes over billions of years starting soon after the Big Bang. In this image, low, medium, and high-energy X-rays that Chandra detects are shown as red, green, and blue respectively.

Image Credit: NASA

It Wasn’t a Complete Waste of Time

Video Credit: NASA

I had a small part in the development and construction of the Soft X-ray Spectrometer. In order to be sensitive to energy of individual photons, the detector had to be kept very cold at a very constant temperature. I was responsible for the analog electronics in the system that powered and controlled the last three stages of the refrigeration system. Our team was able to maintain the sensor array at 0.05 K (±0.000001 °K). That’s 5/100 of a degree above absolute zero.

Hitomi (Astro-H)

This video from JAXA describes some of the astronomy that the Hitomi (Astro-H) mission will be doing. It mentions that the the Soft X-ray Spectrometer on board operates at very low temperature. That’s correct. 50 mK. That’s 0.05 degrees above absolute zero. I was a member of the engineering team at Goddard Space Flight Center that designed and built the refrigeration system that maintains the sensor array as that cold operating point with within (±0.000001 °K). I’m looking forward to sharing data from the mission with the Gentle Readers.

Video Credit: JAXA

A New X-ray Astronomy Satellite

On Friday, the Japan Aerospace Exploration Agency (JAXA) will be launching their sixth satellite dedicated to X-ray astronomy, ASTRO-H, from the Tanegashima Space Center in Kagoshima, Japan. The launch is scheduled at 3:45 a.m. EST.

The observatory carries a state-of-the-art instrument and two telescope mirrors built at Goddard Space Flight Center. That instrument is the Soft X-ray Spectrometer which is able to detect individual low-energy x-ray photons. The SXS detector is cooled to 0.05 degrees above absolute zero, and to keep system noise within useful limits, the operating temperature is held constant ±0.000001 degrees. I was the analog electronics engineer for the team that designed the temperature control system for the SXS.astro-h_illo_labels_0

Click the image to embiggen it. A second click may be useful with some browsers.

Image Credit: JAXA

UPDATE—JAXA has announced that the ASTRO-H launch has been postponed because of high winds at the launch facility. The next possible launch date is on Sunday.

Stay tuned.

X-ray Sources in Andromeda

Andromeda NUSTARThe Nuclear Spectroscopic Telescope Array (or NuSTAR) has captured the best high-energy X-ray view yet of a band across Andromeda, our nearest large, neighboring galaxy. The satellite has observed 40 “X-ray binaries,” intense sources of X-rays comprised of a black hole or neutron star that feeds off a stellar companion.

Image Credit: NASA

The Perseus Dark Matter Matter

[youtube http://www.youtube.com/watch?v=3439YtdQZ1Y]

Video Credit: NASA

Personal Note—I contributed to the design of the cryogenic temperature control system being used to cool the detector array in the Soft X-ray Spectrometer that will fly on Astro-H. The system is capable of holding the detector array at 0.05° above absolute zero with a stability better than ±0.000001°.

When an individual x-ray photon strikes one of the pixels in the SXS detector, the energy raises its temperature slightly which changes the resistance of the cell—the more energetic the photon, the greater the change. The low operating temperature and the tight regulation are necessary to make lower energy x-rays detectable and reduce system noise.

Fermi’s Spiragraph

Fermi's Motion Produces a Study in SpirographThe Fermi Gamma-ray Space Telescope orbits the Earth every 95 minutes, it’s scans building up increasingly more complex views of the universe with every circuit. The image above was put together from eight frames from a movie showing over 4 years’ position and exposure data recorded by Fermi‘s Large Area Telescope (LAT) into a single snapshot. The pattern reflects the various motions of the spacecraft, including its orbit around Earth, the precession of its orbital plane, and the manner in which the LAT nods north and south on alternate orbits.

The LAT sweeps across the entire sky every three hours, capturing the highest-energy form of light—gamma rays—from sources across the universe. Those sources range from supermassive black holes billions of light-years away to objects in our own galaxy, such as X-ray binaries, supernova remnants, and pulsars.

Image Credit: NASA/DoE