Contributor Posts

NASA Astronomy Picture of the Day:

If you can see the stars of the Big Dipper, you can find comet NEOWISE in your evening sky tonight. After sunset look for the naked-eye comet below the bowl of the famous celestial kitchen utensil of the north and above your northwestern horizon. You're looking for a fuzzy 'star' with a tail, though probably not so long a tail as in this clear sky snapshot taken from Los Padres National Forest in California on the evening of July 16. Recent photographs of C/2020 F3 (NEOWISE) often show this comet's broad dust tail and fainter but separate ion tail extending farther than the eye can follow. Skygazers around the world have been delighted to find NEOWISE, surprise visitor from the outer Solar System. Comet NEOWISE Images: July 17 | July 16 | July 15 | July 14 | July 13 | July 12 | July 11 | July 10 & earlier

Photo by Tom Masterson

NASA Astronomy Picture of the Day:

After local midnight on July 14 comet NEOWISE was still above the horizon for Goldenrod, Alberta, Canada, just north of Calgary, planet Earth. In this snapshot it makes for an awesome night with dancing displays of the northern lights. The long-tailed comet and auroral displays are beautiful apparitions in the north these days. Both show the influence of spaceweather and the wind from the Sun. Skygazers have widely welcomed the visitor from the Oort cloud, though C/2020 F3 (NEOWISE) is in an orbit that is now taking it out of the inner Solar System. Comet NEOWISE Images: July 16 | July 15 | July 14 | July 13 | July 12 | July 11 | July 10 & earlier

Photo by Bill Peters

NASA Astronomy Picture of the Day:

This Comet NEOWISE (C/2020 F3) now sweeps through our fair planet's northern skies. Its long tails stretch across this deep skyview from Suchy Vrch, Czech Republic. Recorded on the night of July 13/14, the composite of untracked foreground and tracked and filtered sky exposures teases out details in the comet's tail not visible to the unaided eye. Faint structures extend to the top of the frame, over 20 degrees from the comet's bright coma. Pushed out by the pressure of sunlight itself, the broad curve of the comet's yellowish dust tail is easy to see by eye. But the fainter, more bluish tail is separate from the reflective comet dust. The fainter tail is an ion tail, formed as ions from the cometary coma are dragged outward by magnetic fields in the solar wind and fluoresce in the sunlight. Outbound NEOWISE is climbing higher in northern evening skies, coming closest to Earth on July 23rd. Comet NEOWISE Images: July 15 | July 14 | July 13 | July 12 | July 11 | July 10 & earlier

Photo by Petr Horalek

NASA Astronomy Picture of the Day:

Comet NEOWISE has been wowing photographers around much of the world during dawn and dusk, at the margins of day and night. For the most northern residents of planet Earth, however, the comet circles the North Star and never sets. The night part of this circular arc is apparent in the featured composite of images assembled from a webcam located at a ski resort in the Swiss Alps. Images were selected at 30-minute intervals throughout the night from July 12th -13th. Comet NEOWISE (C/2020 F3) will continue to become more accessible to northern hemisphere observers as its motion places it higher in the sky each evening after sunset over the next few weeks, as it begins its outbound journey. As with all comets, departure from the inner Solar System comes with inevitable fading. Binoculars are the best way to find and observe the comet visually. Notable Images of Comet NEOWISE Submitted to APOD: || July 14 || July 13 || July 12 || July 11 || July 10 & earlier ||

Photo by Philipp Salzgeberfoto-webcam.euAdam Block

NASA Astronomy Picture of the Day:

This sight was worth getting out of bed early. Comet C/2020 F3 (NEOWISE) has been rising before dawn during the past week to the delight of northern sky enthusiasts awake that early. Up before sunrise, the featured photographer was able to capture in dramatic fashion one of the few comets visible to the unaided eye this century, an inner-Solar System intruder that might become known as the Great Comet of 2020. The resulting video details Comet NEOWISE from Italy rising over the Adriatic Sea. The time-lapse video combines over 240 images taken over 30 minutes. The comet is seen rising through a foreground of bright and undulating noctilucent clouds, and before a background of distant stars. Comet NEOWISE has remained unexpectedly bright, so far, with its ion and dust tails found to emanate from a nucleus spanning about five kilometers across. Fortunately, starting tonight, northern observers with a clear and dark northwestern horizon should be able to see the sun-reflecting interplanetary snowball just after sunset. Notable Images of Comet NEOWISE Submitted to APOD: || July 12 || July 11 || July 10 & earlier ||

Video by Paolo Girotti

NASA Astronomy Picture of the Day:

Where do comet tails come from? There are no obvious places on the nuclei of comets from which the jets that create comet tails emanate. One of the best images of emerging jets is shown in the featured picture, taken in 2015 by ESA's robotic Rosetta spacecraft that orbited Comet 67P/Churyumov-Gerasimenko (Comet CG) from 2014 to 2016. The picture shows plumes of gas and dust escaping numerous places from Comet CG's nucleus as it neared the Sun and heated up. The comet has two prominent lobes, the larger one spanning about 4 kilometers, and a smaller 2.5-kilometer lobe connected by a narrow neck. Analyses indicate that evaporation must be taking place well inside the comet's surface to create the jets of dust and ice that we see emitted through the surface. Comet CG (also known as Comet 67P) loses in jets about a meter of radius during each of its 6.44-year orbits around the Sun, a rate at which will completely destroy the comet in only thousands of years. In 2016, Rosetta's mission ended with a controlled impact onto Comet CG's surface. Comet NEOWISE from Around the Globe: Notable Images Submitted to APOD

NASA Astronomy Picture of the Day:

Comet NEOWISE (C/2020 F3) is now sweeping through northern skies. Its developing tails stretch some six degrees across this telescopic field of view, recorded from Brno, Czech Republic before daybreak on July 10. Pushed out by the pressure of sunlight itself, the comet's broad, yellowish dust tail is easiest to see. But the image also captures a fainter, more bluish tail too, separate from the reflective comet dust. The fainter tail is an ion tail, formed as ions from the cometary coma are dragged outward by magnetic fields in the solar wind and fluoresce in the sunlight. In this sharp portrait of our new visitor from the outer Solar System, the tails of comet NEOWISE are reminiscent of the even brighter tails of Hale Bopp, the Great Comet of 1997. Comet NEOWISE from Around the Globe: Notable Images Submitted to APOD

Photo by Miloslav Druckmuller

NASA Astronomy Picture of the Day:

Rounding the Sun on July 3rd and currently headed for the outer Solar System, Comet NEOWISE (C/2020 F3) has been growing brighter in the predawn skies of planet Earth. From low Earth orbit it also rises before the Sun, captured above the approaching glow along the eastern horizon in this snapshot from the International Space Station on July 5. Venus, now Earth's morning star is the brilliant celestial beacon on the right in the field of view. Above Venus you can spot the sister stars of the more compact Pleiades cluster. Earthbound skygazers can spot this comet with the unaided eye, but should look for awesome views with binoculars. Comet NEOWISE from Earth's Surface: Notable Images Submitted to APOD

NASA Astronomy Picture of the Day:

These silvery blue waves washing over a tree-lined horizon in the eastern French Alps are noctilucent clouds. From high in planet Earth's mesosphere, they reflect sunlight in this predawn skyscape taken on July 8. This summer, the night-shining clouds are not new to the northern high-latitudes. Comet NEOWISE is though. Also known as C/2020 F3, the comet was discovered in March by the Earth-orbiting Near Earth Object Wide-field Infrared Survey Explorer (NEOWISE) satellite. It's now emerging in morning twilight only just visible to the unaided eye from a clear location above the northeastern horizon.

Photo by Emmanuel Paoly

NASA Astronomy Picture of the Day:

What is that fuzzy streak extending from Mercury? Long exposures of our Solar System's innermost planet may reveal something unexpected: a tail. Mercury's thin atmosphere contains small amounts of sodium that glow when excited by light from the Sun. Sunlight also liberates these molecules from Mercury's surface and pushes them away. The yellow glow from sodium, in particular, is relatively bright. Pictured, Mercury and its sodium tail are visible in a deep image taken in late May from Italy through a filter that primarily transmits yellow light emitted by sodium. First predicted in the 1980s, Mercury's tail was first discovered in 2001. Many tail details were revealed in multiple observations by NASA's robotic MESSENGER spacecraft that orbited Mercury between 2011 and 2015. Tails are usually associated with comets. The tails of Comet NEOWISE are currently visible with the unaided eye in the morning sky. Comet NEOWISE from Around the Globe: Notable Images Submitted to APOD

Photo by Andrea Alessandrini

NASA Astronomy Picture of the Day:

A comet has suddenly become visible to the unaided eye. Comet C/2020 F3 (NEOWISE) was discovered in late March and brightened as it reached its closest approach to the Sun, inside the orbit of Mercury, late last week. The interplanetary iceberg survived solar heating, so far, and is now becoming closer to the Earth as it starts its long trek back to the outer Solar System. As Comet NEOWISE became one of the few naked-eye comets of the 21st Century, word spread quickly, and the comet has already been photographed behind many famous sites and cities around the globe. Featured, Comet NEOWISE was captured over Lebanon two days ago just before sunrise. The future brightness of Comet NEOWISE remains somewhat uncertain but the comet will likely continue to be findable not only in the early morning sky, but also next week in the early evening sky. Comet NEOWISE from Around the Globe: Notable Images Submitted to APOD

Photo by Moophz

NASA Astronomy Picture of the Day:

Unspeakable beauty and unimaginable bedlam can be found together in the Orion Nebula Arguably the most famous of all astronomy nebulas, the Great Nebula in Orion is an immense interstellar molecular cloud only 1500 light-years away. In the featured deep image shown in assigned colors, the part of the nebula's center known as M43 is shown as taken by the Hubble Space Telescope. The Great Nebula in Orion can be found with the unaided eye near the easily identifiable belt of three stars in the popular constellation Orion. The entire Orion Nebula, including both M42 and M43 spans about 40 light years and is located in the same spiral arm of our Galaxy as the Sun.

Photo by Bryan Goff