Cold Corpse of Dead Star Could be Giant Diamond
B. Saxton (NRAO/AUI/NSF)
An artist's impression of the white dwarf star orbiting with the pulsar PSR J2222-0137.
NASA/JPL-Caltech/K. Su (Univ. of Arizona)
NASA's Spitzer Space Telescope was launched 10 years ago and has since peeled back an infrared veil on the Cosmos. The mission has worked in parallel with NASA's other "Great Observatories" (Hubble and Chandra) to provide coverage of the emissions from galaxies, interstellar dust, comet tails and the solar system's planets. But some of the most striking imagery to come from the orbiting telescope has been that of nebulae. Supernova remnants, star-forming regions and planetary nebulae are some of the most iconic objects to be spotted by Spitzer. So, to celebrate a decade in space, here are Discovery News' favorite Spitzer nebulae.
First up, the Helix Nebula -- a so-called planetary nebula -- located around 700 light-years from Earth. A planetary nebula is the remnants of the death throes of a red giant star -- all that remains is a white dwarf star in the core, clouded by cometary dust.
NASA/JPL-Caltech/B. Williams (NCSU)
Spitzer will often work in tandem with other space telescopes to image a broad spectrum of light from celestial objects. Here, the supernova remnant RCW 86 is imaged by NASA's Spitzer, WISE and Chandra, and ESA's XMM-Newton.
Staring deep into the Messier 78 star-forming nebula, Spitzer sees the infrared glow of baby stars blasting cavities into the cool nebulous gas and dust.
The green-glowing infrared ring of the nebula RCW 120 is caused by tiny dust grains called polycyclic aromatic hydrocarbons -- the bubble is being shaped by the powerful stellar winds emanating from the central massive O-type star.
NASA/JPL-Caltech/J. Stauffer (SSC/Caltech)
Spitzer stares deep into the Orion nebula, imaging the infrared light generated by a star factory.
X-Ray: NASA/CXC/J.Hester (ASU); Optical: NASA/ESA/J.Hester & A.Loll (ASU); Infrared: NASA/JPL-Caltech/R.Gehrz (Univ. Minn.)
In the year 1054 A.D. a star exploded as a supernova. Today, Spitzer was helped by NASA's other "Great Observatories" (Hubble and Chandra) to image the nebula that remains. The Crab Nebula is the result; a vast cloud of gas and dust with a spinning pulsar in the center.
The Tycho supernova remnant as imaged by Spitzer (in infrared wavelengths) and Chandra (X-rays). The supernova's powerful shockwave is visible as the outer blue shell, emitting X-rays.
NASA/JPL-Caltech/E. Churchwell (University of Wisconsin - Madison)
Over 2,200 baby stars can be seen inside the bustling star-forming region RCW 49.
X-ray: NASA/CXC/Univ.Potsdam/L.Oskinova et al; Optical: NASA/STScI; Infrared: NASA/JPL-Caltech
The "Wing" of the Small Magellanic Cloud (SMC) glitters with stars and warm clouds of dust and gas. By combining observations by Spitzer, Chandra and Hubble, the complex nature of this nebulous region can be realized.
Astronomers aren't being poetic when they say this star is a diamond.
Scientists have identified what is possibly the coldest white dwarf ever detected. In fact, this dim stellar corpse is so cold that its carbon has crystallized, effectively forming a diamond the size of Earth, astronomers said.
"It's a really remarkable object," study leader David Kaplan, a professor at the University of Wisconsin-Milwaukee, said in a statement from the National Radio Astronomy Observatory (NRAO). "These things should be out there, but because they are so dim they are very hard to find." [10 Strangest Things in Space]
Kaplan and colleagues were able to find this cosmic gem because it has a more conspicuous companion. The white dwarf does an orbital tango with a pulsar, or a fast-spinning neutron star formed from a supernova explosion that sends out a stream of radio waves like a lighthouse beam. Dubbed PSR J2222-0137, the pulsar lies 900 light-years away from Earth near the constellation Aquarius, and it was first detected using the NRAO's Green Bank Telescope in West Virginia.
Astronomers noticed that the radio signal from PSR J2222-0137 sometimes got delayed because a companion object was passing in front of it, warping space. Studying these delays using the NRAO's Very Large Baseline Array (VLBA) helped scientists determine that the pulsar has a mass 1.2 times that of Earth's sun with a companion that has a mass 1.05 times that of the sun.
The team suspected this companion was a white dwarf, or a dense stellar core left after a star has died. Believing they would be able to see the object in optical and infrared light, the scientists looked for it using the Southern Astrophysical Research (SOAR) telescope in Chile and the 10-meter (33 feet) Keck telescope in Hawaii. But neither instrument was able to detect the white dwarf.
"Because of the radio observations, we know exactly where to look, so we pointed SOAR there and collected light for two and a half hours," Bart Dunlap, a graduate student at the University of North Carolina at Chapel Hill, said in a statement. "Our final image should show us a companion 100 times fainter than any other white dwarf orbiting a neutron star and about 10 times fainter than any known white dwarf, but we don’t see a thing. If there's a white dwarf there, and there almost certainly is, it must be extremely cold."
When talking about stellar objects, "cold" is a relative term; this white dwarf is still burning at 4,892 degrees Fahrenheit (2,700 degrees Celsius), but that's 5,000 times cooler than the center of Earth's sun.
Such a cool object would be largely crystallized carbon, similar to a diamond, the scientists said. Astronomers have theorized that these objects should be lurking in the universe, but diamond stars are difficult to detect because they are so faint.
Scientists have theorized that diamond alien planets should exist, too. A "super-Earth" 40 light-years from our planet called 55 Cancri e is suspected to be one such world; a 2012 paper in the Astrophysical Journal Letters argued that this exoplanet is composed mainly of carbon in the form of diamond and graphite.
The study on the diamond white dwarf was published in the Astrophysical Journal.