Star Trails for a Red Planet
Does Mars have a north star? In long exposures of Earth's night sky, star trails make concentric arcs around the north celestial pole, the direction of our fair planet's axis of rotation. Bright star Polaris is presently the Earth's North Star, close on the sky to Earth's north celestial pole. But long exposures on Mars show star trails too, concentric arcs about a celestial pole determined by Mars' axis of rotation. Tilted like planet Earth's, the martian axis of rotation points in a different direction in space though. It points to a place on the sky between stars in Cygnus and Cepheus with no bright star comparable to Earth's north star Polaris nearby. So even though this ruddy, weathered landscape is remarkably reminiscent of terrain in images from the martian surface, the view must be from planet Earth, with north star Polaris near the center of concentric star trails. The landforms in the foreground are found in Qinghai Province in northwestern China.
Starburst Galaxy M94 from Hubble Why does this galaxy have a ring of bright blue stars? Beautiful island universe Messier 94 lies a mere 15 million light-years distant in the
Mercury Crosses a Quiet Sun What's that black dot crossing the Sun? The planet Mercury. Mercury usually passes over or under the Sun, as seen from Earth, but last month
M27: The Dumbbell Nebula Is this what will become of our Sun? Quite possibly. The first hint of our Sun's future was discovered inadvertently in 1764. At that time,
Electric Night It may appear, at first, like the Galaxy is producing the lightning, but really it's the Earth. The featured nighttime landscape was taken from a southern tip
Spiral Galaxy NGC 6744 Beautiful spiral galaxy NGC 6744 is nearly 175,000 light-years across, larger than our own Milky Way. It lies some 30 million light-years distant in the southern constellation
Pleiades to Hyades This cosmic vista stretches almost 20 degrees from top to bottom, across the dusty constellation Taurus. It begins at the Pleiades and ends at the Hyades, two star
Lines of Time In time stars trace lines through the night sky on a rotating planet. Taken over two hours or more, these digitally added consecutive exposures were made with a
Geminid Meteors over Chile Are meteors streaming out from a point in the sky? Yes, in a way. When the Earth crosses a stream of Sun-orbiting meteors, these meteors
Looking Sideways from the Parker Solar Probe Everybody sees the Sun. Nobody's been there. Starting in 2018 though, NASA launched the robotic Parker Solar Probe (PSP) to investigate regions near
N63A: Supernova Remnant in Visible and X-ray What has this supernova left behind? As little as 2,000 years ago, light from a massive stellar explosion in the Large Magellanic Cloud
Decorating the Sky Bright stars, clouds of dust and glowing nebulae decorate this cosmic scene, a skyscape just north of Orion's belt. Close to the plane of our Milky Way galaxy,
Full Moon Geminids The dependable annual Geminid meteor shower will be near its peak tonight (December 13/14) and before tomorrow's dawn. As Earth crosses through the dusty trail of active asteroid
Mammatus Clouds over Nebraska When do cloud bottoms appear like bubbles? Normally, cloud bottoms are flat. This is because moist warm air that rises and cools will condense into water
The Magnetic Fields of Spiral Galaxy M77 Can magnetic fields help tell us how spiral galaxies form and evolve? To find out, the HAWC instrument on NASA's airborne (747)
