Reaching Earth just in time for Independence Day — a new view from NASA’s Hubble Space Telescope, which includes ultraviolet (UV) light, shows Eta Carinae, a supermassive star in the constellation Carina, glowing in red, white, and blue. Eta Carinae resides 7500 light-years away. Astronomers using Hubble’s Wide Field Camera 3 to map the UV-light glow of magnesium embedded in the star were surprised to discover that the star had hot, expanding gases in places where they had not seen it before. “We had used Hubble for decades to study Eta Carinae in visible and infrared light, and we thought we had a pretty full accounting of its ejected debris,” said Nathan Smith of Steward Observatory at the University of Arizona. “But this new ultraviolet-light image looks astonishingly different, revealing gas we did not see in other visible-light or infrared images.” This Hubble Space Telescope image of the giant, petulant star Eta Carinae is yielding new surprises. Telescopes such as Hubble have monitored the supermassive star for more than two decades. The star, the largest member of a double-star system, has been prone to violent outbursts, including an episode in the 1840s during which ejected material formed the bipolar bubbles seen here. Now, using Hubble’s Wide Field Camera 3 to probe the nebula in ultraviolet light, astronomers have uncovered the glow of magnesium embedded in warm gas (shown in blue) in places they had not seen it before. The luminous magnesium resides in the space between the dusty bipolar bubbles and the outer shock-heated nitrogen-rich filaments (shown in red). The streaks visible in the blue region outside the lower-left lobe are a striking feature in the image. These streaks are created when the star’s light rays poke through the dust clumps scattered along the bubble’s surface. Wherever the ultraviolet light strikes the dense dust, it leaves a long, thin shadow that extends beyond the lobe into the surrounding gas. Courtesy of NASA, ESA, N. Smith (University of Arizona), and J. Morse (BoldlyGo Institute). Eta Carinae’s celestial outburst takes the shape of a pair of ballooning lobes of dust and gas and other filaments that were blown out from the star. The fireworks started in the 1840s when the star went through a titanic outburst, called the Great Eruption, making Eta Carinae the second-brightest star in the sky for over a decade after the eruption. Scientists have long known that the outer material thrown off in the 1840s eruption has been heated by shock waves after crashing into the star’s previously ejected material. In the new images, the team had expected to find light from magnesium coming from the same complicated array of filaments as seen in the glowing nitrogen. Instead, a completely new luminous magnesium structure was found in the space between the dusty bipolar bubbles and the outer shock-heated nitrogen-rich filaments. “Most of the emission is located where we expected to find an empty cavity. This extra material is fast, and it ‘ups the ante’ in terms of the total energy for an already powerful stellar blast,” Smith said. The streaks visible in the blue region outside the lower-left lobe are created when the star’s light rays poke through the dust clumps scattered along the bubble’s surface. Wherever the UV light strikes the dense dust, it leaves a long, thin shadow that extends beyond the lobe into the surrounding gas. The technique that was used to search in UV light for warm gas could be used to study other stars and gaseous nebulas, the researchers said. “We’re excited by the prospect that this type of ultraviolet magnesium emission may also expose previously hidden gas in other types of objects that eject material, such as protostars or other dying stars. Only Hubble can take these kinds of pictures,” Smith said. The stellar fireworks will eventually reach their finale when Eta Carinae explodes as a supernova. This could have already happened, although the geyser of light from such a brilliant blast hasn’t yet reached Earth. For the complete story, visit the Hubble web page. In the mid-1800s, mariners sailing the southern seas navigated at night by a brilliant star in the constellation Carina. The star, named Eta Carinae, was the second brightest star in the sky for more than a decade. Those mariners could hardly have imagined that by the mid-1860s the brilliant orb would no longer be visible. Eta Carinae was enveloped by a cloud of dust ejected during a violent outburst named “The Great Eruption.” Courtesy of NASA's Goddard Space Flight Center.
