Proto-Planetary Smashup Discovered Around Baby Star
This artist’s concept shows the immediate aftermath of a large asteroid impact around NGC 2547-ID8, a 35-million-year-old sun-like star thought to be forming rocky planets. NASA's Spitzer Space Telescope witnessed a giant surge in dust around the star, likely the result of two asteroids colliding.
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.
Scientists believe they have spotted a rocky planet in the making around a young, sun-like star 1,200 light years away in the constellation Vela.
The violent process, marked by collisions of asteroids and other proto-planetary bodies, was detected by a dramatic change in telltale infrared radiation emissions coming from warm dust circling the 35 million-year-old star.
Astronomers monitored the star, known as NGC 2547-ID8, with NASA’s Spitzer infrared space telescope between May 25, 2012, and Aug. 23, 2015, taking a 157-day break when the star was behind the sun and not visible. During the gap, the star’s disk of orbiting dust dramatically brightened, then slowly dimmed over the course of a nearly a year.
“The observed sudden brightening and the consequent decay would be very hard to explain, if at all possible, without the occurrence of a new impact,” Huan Meng, a planetary sciences graduate student at the University of Arizona, wrote in an email to Discovery News.
Meng and colleagues turned to computer simulations to better understand what they were seeing. The best explanation is that in late 2012, a major collision took place among the star’s orbiting proto-planetary bodies, producing vapor that condensed into a thick cloud of silicate spheres. Later collisions pulverized the small spheres into dust.
The crash is believed to be similar to the one that occurred early in Earth’s history which led to the formation of the moon.
While scientists have discovered brightening in stars’ debris disks before, they did not have real-time observations to rule out other phenomena besides smashing proto-planets as the cause. A super-volcanic explosion on a young terrestrial planet, for example, or the breakup of a comet could brighten up a debris disk, but these events wouldn’t cause variations over time like what was observed around ID8.
“This is the first detection of a planetary impact outside our solar system,” Meng said.
Scientists estimate it takes 10 to 15 giant impacts of planetary embryos to form a rocky Earth-sized world.
“We now directly witness a large impact around ID8, suggesting a reservoir of large asteroids and planetary embryos, but we still do not know whether ID8 has giant or ice-giant planets, or outer planetesimals analogous to Kuiper belt objects,” Kate Su, associate astronomer at University of Arizona’s Steward Observatory, wrote in an email to Discovery News.
“This study pioneers a new way to gain direct observational evidence for terrestrial planet formation,” added astronomer Peter Plavchan, with Missouri State University “Because the debris disk from the star ID8 changes in brightness on particular timescales or periods, we can use Newton’s version of Kepler’s Third Law to infer the formation of planets at specific distances from the host star.”
The research, which appears in this week's Science, also may shed light on the construction phase of Earth and the rest of the terrestrial planets in our solar system.