Thursday, September 18, 2025

APOD - Comet C/2025 R2 (SWAN)

Astronomy Picture of the Day

Discover the cosmos! Each day a different image or photograph of our fascinating universe is featured, along with a brief explanation written by a professional astronomer.

2025 September 18
See Explanation.  Clicking on the picture will download  the highest resolution version available.

Comet C/2025 R2 (SWAN)
Image Credit & Copyright: Team Ciel Austral

Explanation: A new visitor from the outer Solar System, comet C/2025 R2 (SWAN) also known as SWAN25B was only discovered late last week, on September 11. That's just a day before the comet reached perihelion, its closest approach to the Sun. First spotted by Vladimir Bezugly in images from the SWAN instrument on the sun-staring SOHO spacecraft, the comet was surprisingly bright but understandably difficult to see against the Sun's glare. Still close to the Sun on the sky, the greenish coma and tail of C/2025 R2 (SWAN) are captured in this telescopic snapshot from September 17. Spica, alpha star of the constellation Virgo, shines just beyond the upper left edge of the frame while the comet is about 6.5 light-minutes from planet Earth. Near the western horizon after sunset and slightly easier to see in binoculars from the southern hemisphere, this comet SWAN will pass near Zubenelgenubi, alpha star of Libra, on October 2. C/2025 R2 (SWAN) is scheduled to make its closest approach to our fair planet around October 20.

Tomorrow's picture: it's complicated


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Authors & editors: Robert Nemiroff (MTU) & Jerry Bonnell (UMCP)
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Wednesday, September 17, 2025

APOD - Nebulas and Clusters in Sagittarius

Astronomy Picture of the Day

Discover the cosmos! Each day a different image or photograph of our fascinating universe is featured, along with a brief explanation written by a professional astronomer.

2025 September 17
A starfield surrounds a several large nebulas  that appear mostly red but also white and blue.  Dark dust and blue filaments also populate the frame.   Please see the explanation for more detailed information.

Nebulas and Clusters in Sagittarius
Image Credit & Copyright: J. De Winter, C. Humbert, C. Robert & V. Sabet; Text: Ogetay Kayali (MTU)

Explanation: Can you spot famous celestial objects in this image? 18th-century astronomer Charles Messier cataloged only two of them: the bright Lagoon Nebula (M8) at the bottom, and the colorful Trifid Nebula (M20) at the upper right. The one on the left that resembles a cat's paw is NGC 6559, and it is much fainter than the other two. Even harder to spot are the thin blue filaments on the left, from supernova remnant (SNR G007.5-01.7). Their glow comes from small amounts of glowing oxygen atoms that are so faint that it took over 17 hours of exposure with just one blue color to bring up. Framing this scene of stellar birth and death are two star clusters: the open cluster M21 just above Trifid, and the globular cluster NGC 6544 at lower left.

Tomorrow's picture: NGC 6914


< | Archive | Submissions | Index | Search | Calendar | RSS | Education | About APOD | Discuss | >

Authors & editors: Robert Nemiroff (MTU) & Jerry Bonnell (UMCP)
NASA Official: Amber Straughn Specific rights apply.
NASA Web Privacy, Accessibility, Notices;
A service of: ASD at NASA / GSFC,
NASA Science Activation
& Michigan Tech. U.


This is an automated email. If you notice any problems, just send me a note at gtracy@gmail.com. You can add and remove email addresses to this distribution list here, https://apodemail.org.Unsubscribe