Author: NASA中文

2020年9月21日 Omega Sunrise Image Credit & Copyright: Juan Antonio Sendra Explanation: Capturing this sunrise required both luck and timing. First and foremost, precise timing was needed to capture a sailboat crossing right in front of a rising Sun. Additionally, by a lucky coincidence, the background Sun itself appears unusual — it looks like the Greek letter Omega (Ω). In reality, the Sun remained its circular self — the Omega illusion was created by sunlight refracting through warm air just above the water. Optically, the feet of the capital Omega are actually an inverted image of the Sun region just above it. Although somewhat rare, optical effects caused by the Earth’s atmosphere can make distant objects near the horizon — including the Sun and Moon —…

2020年9月20日 Breaking Distant Light Image Credit: VIMOS, VLT, ESO Explanation: In the distant universe, time appears to run slowly. Since time-dilated light appears shifted toward the red end of the spectrum (redshifted), astronomers are able to use cosmological time-slowing to help measure vast distances in the universe. Featured, the light from distant galaxies has been broken up into its constituent colors (spectra), allowing astronomers to measure the cosmological redshift of known spectral lines. The novelty of the featured image is that the distance to hundreds of galaxies can be measured from a single frame, in this case one taken by the Visible MultiObject Spectrograph (VIMOS) operating at the Very Large Telescope (VLT) array in Chile. Analyzing the space distribution of distant objects will allow insight…

2020年9月19日 Orion in Depth Illustration Credit & Copyright: Ronald Davison Explanation: Orion is a familiar constellation. The apparent positions of its stars in two dimensions create a well-known pattern on the bowl of planet Earth’s night sky. Orion may not look quite so familiar in this 3D view though. The illustration reconstructs the relative positions of Orion’s bright stars, including data from the Hipparcus catalog of parallax distances. The most distant star shown is Alnilam. The middle one in the projected line of three that make up Orion’s belt when viewed from planet Earth, Alnilam is nearly 2,000 light-years away, almost 3 times as far as fellow belt stars Alnitak and Mintaka. Though Rigel and Betelgeuse apparently shine brighter in planet Earth’s sky, that makes…

2020年9月17日 Solar Cycle 25 Has Begun Image Credit: NASA, SDO Explanation: The general trend of monthly sunspot data now confirms that the minimum of the approximately 11 year cycle of solar activity occurred in December 2019, marking the start of Solar Cycle 25. That quiet Sun, at minimum activity, appears on the right of this split hemispherical view. In contrast, the left side shows the active Sun at the recognized maximum of Solar Cycle 24, captured in April 2014. The extreme ultraviolet images from the orbiting Solar Dynamics Observatory highlight coronal loops and active regions in the light of highly ionized iron atoms. Driving the space weather around our fair planet, Solar Cycle 24 was a relatively calm one and predictions are that cycle 25…