These images of star clusters represent a new study from NASA’s Chandra X-ray Observatory that shows how young Sun-like stars are dimmer in X-rays than previously thought. As described in our latest press release, this result has implications for the prospects of life developing and surviving on planets in orbit around these stars.
Trumpler 3 and NGC 2353 are so-called open clusters that contains hundreds of young stars. These stars are tied to each other through gravity, having been formed from the same clouds of gas. Many of these stars have masses that are similar to our Sun, but are much younger. In these new composite images of Trumpler 3 and NGC 2353, X-rays from Chandra (purple) have been combined with an optical image from the PanSTARRS telescope in Hawaii (red, green, and blue). Another star clusters from the new Chandra study, NGC 2301 is shown in the same color schemes with the X-ray and optical data.
In total, the new Chandra study looked at eight clusters of stars between the ages of 45 million and 750 million years old. (By comparison, our Sun has lived for about 4.6 billion years.) The researchers found that Sun-like stars older than about 100 million years in these clusters unleashed only about a quarter to a third of the X-rays that they expected.
This relative calm could be a boon to the formation of life on planets around stars that are younger versions of our own Sun. This is because large amounts of X-rays can erode a planet’s atmosphere and prevent formation of molecules necessary for organic life, as we know it. On average, three-million-year-old stars with a mass equal to the Sun produce about a thousand times more X-rays than today's Sun. Meanwhile, 100-million-year-old solar-mass stars are about 40 times brighter in X-rays than the present Sun.
An artist’s illustration depicts X-rays and other high energy radiation from a young Sun-like star eroding some of the atmosphere of an orbiting planet. Lower levels of X-rays will cause less erosion of planetary atmospheres.
The researchers found that stars with about the same mass as the Sun quieted down relatively rapidly — after a few hundred million years — while ones with less mass kept up their high levels of X-ray emission for longer. Combined with a decrease in the energy of the X-rays and the disappearance of energetic particles, the Sun-sized stars are apparently better suited to host planets with robust atmospheres and possibly blossoming life than previously thought.
The team used data from ESA’s Gaia satellite and X-ray data from the ROSAT mission. This data allowed them to identify the stars that were members of the clusters (not foreground or background stars). To measure the X-ray output from the stars, they made new Chandra observations of five clusters with ages between 45 million and 100 million years and Chandra and ROSAT data from archives to study three older clusters with ages between 220 and 750 million years.
A new paper describing these results has been accepted and appears in The Astrophysical Journal. The authors of the paper are Konstantin Getman (Penn State University), Eric Feigelson (Penn State), Vladimir Airapetian (NASA Goddard Space Flight Center), and Gordon Garmire (Penn State).
NASA's Marshall Space Flight Center in Huntsville, Alabama, manages the Chandra program. The Smithsonian Astrophysical Observatory's Chandra X-ray Center controls science operations from Cambridge, Massachusetts, and flight operations from Burlington, Massachusetts.
This release features three composite images and one artist's illustration. Each composite image depicts a different star cluster packed with countless glowing specks of light. The close-up artist's illustration depicts the effects of a young Sun-like star's high energy radiation on the atmosphere of an orbiting planet.
The three clusters depicted in today's release are Trumpler 3, NGC 2353, and NGC 2301. In each image, the blackness of space is blanketed in white, blue, orange, purple, and golden yellow dots. Some of the dots are in the foreground, while others are background stars. Many in the middle-ground are clustered Sun-like stars being observed in a new study by Chandra. Some of the stars in the cluster and foreground appear as gleaming dots with glowing halos and occasional diffraction spikes, while the background stars are generally smaller and fainter.
In these composite images, purple represents X-rays from Chandra, while reds, greens and blues are courtesy of optical images from the Pan-STARRS telescope in Hawaii.
Results from the new study reveal that many young Sun-like stars are dimmer in X-rays than previously thought. X-rays and other high energy radiation from a young Sun-like star can erode some of the atmosphere of an orbiting planet. This erosion is highlighted in the artist's illustration. Here, a massive ball of churning fire, the young Sun-like star, occupies our left half of the photorealistic graphic. At its right is an orbiting planet, a relatively small, pale sphere, shedding its atmosphere, depicted as a wake of faint blue mist.
Sun-like stars that emit lower levels of X-rays will cause less atmospheric erosion on orbiting planets. This impacts the prospects of life developing and surviving on planets orbiting these stars.
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